Pole piece, coating system thereof, battery cell, battery device, and electric device

Abstract

The application provides a pole piece, 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 has a plurality of regions arranged adjacently along a second direction. The second direction is perpendicular to the first direction. The active material layer is attached to each region. Along the second direction, the expansion coefficient of the active material layer of a first region is greater than the expansion coefficients of the active material layers of regions on both sides of the first region. The first region is a region in which a middle position of the current collector along the second direction is located. The application can solve the problem of uneven temperature change in the charging and discharging process of existing batteries.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrode sheet and its coating system, a battery cell, a battery device, and an electrical device. Background Technology

[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, current conventional lithium-ion batteries face many challenges, particularly the uneven heat distribution within the cell.

[0003] This uneven heat distribution leads to excessively high temperatures in the central region of the cell, which in turn accelerates the chemical reaction rate in that area. This can cause structural damage, such as electrode thinning or an increased gap between the anode and cathode. When recharged, these changes will result in more complex polarization effects inside the battery, causing faster capacity decay and potentially triggering problems such as lithium plating, severely impacting the overall lifespan and performance of the cell.

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

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

[0006] Based on the above objectives, in a first aspect, this application proposes an electrode sheet 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 adjacent to each other along a second direction, the second direction being perpendicular to the first direction, and the active material layer being attached to each region; wherein, along the second direction, the coefficient of thermal expansion of the active material layer in the first region is greater than the coefficient of thermal expansion of the active material layers in the regions on both sides of the first region, and the first region is the region where the current collector is located at the middle position along the second direction.

[0007] The above embodiments provide an electrode in which the expansion coefficient of the active material layer in the middle region is greater than that in the active material layers on both sides, achieving a gradient distribution of expansion coefficients. Thus, when this electrode is used as a cathode electrode, lithium ions embed into the cathode electrode during discharge, accelerating the cathode electrode's reaction rate. Because the expansion coefficient in the middle of the electrode is greater than that on the sides, the expansion in the middle is greater, and the expansion in the middle of the cathode electrode compensates for the reduction in the anode electrode caused by the deintercalation of lithium ions from the anode, reducing the gap between the cathode and anode electrodes. When this electrode is used as an anode electrode, lithium ions deintercalate from the cathode electrode and embed into the anode electrode during charging, accelerating the anode electrode's reaction rate. Because the expansion coefficient in the middle of the electrode is greater than that on the sides, the expansion in the middle is greater, and the expansion in the middle of the anode electrode compensates for the reduction in the middle of the anode electrode caused by the deintercalation of lithium ions from the cathode, reducing the gap between the cathode and anode electrodes, reducing the risk of lithium plating in the battery, and improving the cell's cycle performance.

[0008] In some embodiments, the active material layer includes a first active material and a second active material, wherein the coefficient of thermal expansion of the first active material is less than that of the second active material, and the proportion of the first active material in the active material layer in each region is greater than that 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] By setting the content of the first active material and the second active material in the above embodiments, it is possible to use more second active material with a high expansion coefficient in the middle region in a scenario where the first active material with a small expansion coefficient is the main system. This results in the expansion coefficient of the active material layer in the first region being greater than that in the active material layers on both sides of the first region. This active material distribution scheme can achieve greater expansion in the middle region, thereby balancing the stress and volume changes 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, wherein the coefficient of thermal expansion of the first active material is less than that of the second active material, and the proportion of the first active material in the active material layer in each region is less than that 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 less than the content of the first active material in the active material layers in the regions on both sides of the first region.

[0011] By setting the content of the first active material and the second active material in the above embodiments, it is possible to use more second active material with a high expansion coefficient in the middle region in a scenario where the second active material with a large expansion coefficient is the main system. This results in the expansion coefficient of the active material layer in the first region being greater than that in the active material layers on both sides of the first region. This active material distribution scheme can achieve greater expansion in the middle region, thereby balancing the stress and volume changes 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 comprises lithium iron phosphate, and the second active material comprises a ternary material.

[0013] This embodiment uses different proportions of LFP and NCM in different areas, which enables the battery to 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 an adhesive, and along the second direction, the content of the adhesive in the active material layer of the first region is less than the content of the adhesive in the active material layers of the regions on both sides of the first region.

[0015] The above embodiments change the expansion coefficient of different regions by changing the content of binder in different regions of the electrode, thereby making the expansion of the first region greater than that of the two sides. The expansion of the middle part of the cathode electrode fills the reduction in the middle part of the anode electrode caused by the deintercalation of lithium ions in the anode, reduces the gap between the cathode and anode electrodes, reduces the risk of lithium plating in the battery, and improves the cycle performance of the cell.

[0016] In some embodiments, the current collector has a first surface and a second surface arranged in opposite directions, each of the first surface and the second surface having a plurality of regions arranged adjacent to each other along the second direction, and the active material layer is attached to each region.

[0017] The above embodiments can achieve coating on both sides of the current collector to form a double-sided coated electrode, which can improve the electrode utilization rate and reduce costs.

[0018] In some embodiments, the first region is divided based on historical temperature data, which includes the temperature values ​​of individual battery cells during charging and discharging; wherein, the first region is the electrode region corresponding to the location of the maximum temperature value in the historical temperature data, and the regions on both sides of the first region are divided into two parts by using a preset temperature difference as a region division gradient.

[0019] The above embodiments use the position with the highest temperature of the battery cell to obtain the middle region of the electrode, which makes the division of the electrode region more experimental and improves the reliability of the electrode. Using a preset temperature difference as the region division gradient, the region can be divided into two parts on both sides of the position with the maximum temperature value, reducing the risk of local overheating of the battery.

[0020] In some embodiments, the first region is divided based on historical coin cell capacity data, which includes the specific capacity loss value of a single battery cell; wherein, the first region is the electrode region corresponding to the position in the historical coin cell capacity data where the specific capacity loss value is greater than a preset value, and the regions on both sides of the first region are partitioned into two regions on both sides of the first region by using a preset specific capacity difference as a region division gradient.

[0021] The above embodiments use the relationship between the specific capacity loss value of the battery cell and a preset value to obtain the middle region of the electrode, making the electrode region division more targeted and improving the reliability of the electrode. By using the preset specific capacity difference as the region division gradient, the region with larger specific capacity loss can be divided into two parts, reducing the performance difference between different regions and thus extending the battery's service life.

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

[0023] The electrode obtained in the above embodiments has three regions, which can realize rapid partitioning of the electrode and improve the preparation efficiency of the electrode.

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

[0025] The above embodiments can better match the temperature distribution of the battery cell in actual applications. By dividing the battery cell into gradient zones according to the actual usage of the individual cells, the central area with the highest 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] Secondly, a coating system is also provided, the system comprising: a plurality of coating dies arranged side by side along a second direction, each coating die being connected to a slurry storage tank, the coating die being used to coat the slurry in the slurry storage tank onto a current collector, the current collector extending along a first direction, the surface of the current collector having a plurality of regions arranged adjacent to each other along the second direction, the second direction being perpendicular to the first direction, the slurry storage tank, the coating die, and the regions on the surface of the current collector corresponding one-to-one; wherein, the coefficient of expansion of the slurry in the slurry storage tank corresponding to the first region is greater than the coefficient of expansion of the slurry in the slurry storage tanks corresponding to the regions on both sides of the first region; a conveying device for conveying the current collector along the first direction; the coating die being disposed at one end of the conveying device for coating the current collector surface with slurry; and a controller for controlling the conveying device and the coating die to form the electrode sheet.

[0027] The system described in the above embodiment can precisely control the expansion coefficient of the slurry in different regions by setting up a coating die head and a corresponding slurry storage tank for each region separately. This differentiated control of the slurry expansion coefficient in the first region and its two adjacent regions, with the expansion coefficient of the slurry in the first region being greater than that in the two adjacent regions, allows for the fabrication of electrode sheets that can solve the problem of uneven temperature distribution in batteries.

[0028] In some embodiments, the coating die head includes a first coating die head, a second coating die head, and a third coating die head, which 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 correspondingly arranged to the first region. The coefficient of expansion of the slurry in the first slurry storage tank is greater than that of the slurry in the third slurry storage tank, and the coefficient of expansion of the slurry in the third slurry storage tank is greater than that of the slurry in the second slurry storage tank.

[0029] The above embodiments can better match the temperature distribution of the battery cell in actual applications. By dividing the battery cell into gradient zones according to the actual usage of the battery cell, the central area with the highest 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 made with this electrode, improve battery performance, extend life, and enhance safety.

[0030] Thirdly, a battery cell is also provided, the battery cell including an electrode assembly, an electrolyte and a housing, the electrode assembly and the electrolyte being housed in an accommodating space inside the housing; the electrode assembly including a first electrode, a second electrode and a separator, the separator being disposed between the first electrode and the second electrode, at least one of the first electrode and the second electrode being an electrode as described in any one of the first aspects.

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

[0032] Fifthly, an electrical device is also provided, including a battery device as described in the fourth aspect, the battery device being used to supply power to the electrical device.

[0033] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

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

[0035] Figure 1 This application shows schematic diagrams of the structure of electrode sheets provided in some embodiments;

[0036] Figure 2 This application provides schematic diagrams illustrating electrode changes during discharge according to some embodiments.

[0037] Figure 3 This invention provides another schematic diagram of the structure of an electrode sheet according to some embodiments of the present application;

[0038] Figure 4 This application provides schematic diagrams of the structure of a battery cell formed from electrode sheets according to some embodiments;

[0039] Figure 5 This paper presents a comparison chart of cell parameter results under different material ratios provided in the embodiments of this application;

[0040] Figure 6 This diagram illustrates the structure of the coating system provided in an embodiment of this application.

[0041] Figure 7A schematic diagram of the structure of a battery cell provided in an embodiment of this application is shown. Detailed Implementation

[0042] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0044] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0045] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0046] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0047] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0048] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0049] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0050] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0051] Battery cells are typically housed within a casing to form individual battery cells. This results in limited space in the center of the cell, leading to less heat dissipation compared to the edges and uneven heat distribution within the cell. Consequently, during charge and discharge cycles, the temperature in the center of the battery cell is generally higher than that of the upper and lower sides. If the center remains consistently at a high temperature, the reaction rate in the center accelerates, prioritizing the release of stored energy. This leads to a thinner anode in the center, causing the center to complete the discharge process first, while the upper and lower anodes are not yet fully discharged. However, the cell's state of charge (SOC) has already decreased. At this point, the anode electrode thickness in the center is the smallest, resulting in a larger gap between it and the cathode. This increases polarization during recharging, leading to defects such as lithium plating and increased cell losses. As the number of charge and discharge cycles increases, irreversible capacity loss in the cell intensifies, resulting in performance degradation.

[0052] To address the aforementioned issues, this embodiment provides an electrode where the coefficient of thermal expansion of the active material layer in the central region is greater than that in the regions on either side. Thus, when this electrode is used as a cathode electrode, lithium ions embed into the cathode electrode during discharge, accelerating the cathode electrode's reaction rate. Because the coefficient of thermal expansion in the central region is greater than that on the sides, the expansion in the central region is greater. This expansion in the central region of the cathode electrode compensates for the reduction in the central region of the anode electrode caused by the deintercalation of lithium ions from the anode, reducing the gap between the cathode and anode electrodes. Similarly, when this electrode is used as an anode electrode, lithium ions deintercalate from the cathode electrode and embed into the anode electrode during charging, accelerating the anode electrode's reaction rate. Because the coefficient of thermal expansion in the central region is greater than that on the sides, the expansion in the central region is greater. This expansion in the central region of the anode electrode compensates for the reduction in the central region of the anode electrode caused by the deintercalation of lithium ions from the cathode, reducing the gap between the cathode and anode electrodes, reducing the risk of lithium plating in the battery, and improving the cell's cycle performance.

[0053] For ease of explanation, the following embodiments will be described using an example of an electrode sheet used to form a battery cell, and the battery cell used to form a single battery cell.

[0054] Figure 1 For schematic diagrams of the electrode structure provided in some embodiments of this application, see [link to relevant documentation]. Figure 1 In this embodiment, the electrode 10 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 arranged adjacent to each other along a second direction, the second direction being perpendicular to the first direction. The active material layer 12 is attached to each region. In this second direction, the coefficient of expansion of the active material layer in the first region 111 is greater than the coefficient of expansion of the active material layers in the regions on both sides of the first region. The first region 111 is the region where the current collector is located at the middle position along the second direction.

[0055] The current collector 11 is a structure or component used to collect current, and can 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] In this embodiment, the first direction is the length direction of the current collector. During the electrode fabrication process, the current collector extends along the first direction, thereby enabling the coating of active material slurry onto the current collector to form the electrode. The second direction is perpendicular to the first direction, that is, the width direction of the current collector. In this embodiment, the current collector is divided into multiple regions along its width direction, which can be 3 regions, 4 regions, 5 regions, 6 regions, etc., specifically determined according to the electrode width and actual product requirements.

[0057] like Figure 1The current collector has multiple regions including a first region 111, a second region 112, and a third region 113. The first region 111 is the region located at the middle position of the current collector along the second direction, that is, in... Figure 1 In the second direction shown, the second region 112, the first region 111, and the third region 113 are sequentially adjacent. Furthermore, the coefficient of thermal expansion of the active material layer in the first region 111 is greater than that of the active material layers in the regions on either side of the first region. Continuing with the above example, the coefficient of thermal expansion of the active material layer in the first region 111 is greater than that of the active material layers in the second region 112 and the third region 113. Thus, after the slurry coating of the active material layer is completed and dried, it is compacted using pressure rollers to obtain lithium battery electrode sheets with different structures and coefficients of thermal expansion in the upper and middle sections.

[0058] Figure 2 This is a schematic diagram illustrating the electrode changes during discharge according to some embodiments of this application. This embodiment uses a cathode electrode as an example. When the electrode in this embodiment is used as a cathode electrode, the cathode electrode undergoes a winding process to match the anode electrode and the separator to form a bare cell. See [link to relevant documentation]. Figure 2 In the battery cell, the anode electrode 202, the separator 201, and the electrode 10 of this embodiment are adjacent. During discharge, lithium ions separate from the active material layer of the anode electrode 202 and are inserted into the active material layer of the cathode electrode 10 via the electrolyte. Figure 2 As shown, due to the high temperature in the middle of the battery, the reaction rate in the middle of the anode electrode 202 is fast, and the thickness of lithium ions in the middle decreases rapidly. However, in this embodiment, due to the high temperature in the middle of the cathode electrode 10, such as... Figure 2 The expansion coefficient of the first region 111 is greater than that of the active material layer of the second region 112 and the third region 113. Therefore, during the process of lithium ion insertion 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. As a result, the expansion degree of the first region increases, and the amount of expansion towards the anode also increases, which can make up for the reduction of the anode electrode, thereby reducing the gap between the anode and cathode electrodes, reducing the risk of lithium plating in the battery, and improving the cycle performance of the cell.

[0059] In this embodiment, the active material layer is a slurry coating with micropores, which serves as a carrier for lithium ions and electron insertion during battery charging and discharging, playing a role in energy storage and release.

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

[0061] The above embodiments provide an electrode where the expansion coefficient of the active material layer in the middle region is greater than that in the active material layers on both sides, achieving a gradient distribution of expansion coefficients. Thus, when this electrode is used as a cathode electrode, lithium ions intercalate into the cathode electrode during discharge, accelerating the cathode electrode's reaction rate. Because the expansion coefficient in the middle of the electrode is greater than that on the sides, the expansion in the middle is greater. This expansion in the middle of the cathode electrode compensates for the reduction in the anode electrode caused by lithium ion deintercalation, reducing the gap between the cathode and anode electrodes, decreasing the risk of lithium plating in the battery, and improving the cell's cycle performance. When this electrode is used as an anode electrode, lithium ions deintercalate from the cathode electrode and intercalate into the anode electrode during charging, accelerating the anode electrode's reaction rate. Because the expansion coefficient in the middle of the electrode is greater than that on the sides, the expansion in the middle is greater. This expansion in the middle of the anode electrode compensates for the reduction in the middle of the anode electrode caused by lithium ion deintercalation, reducing the gap between the cathode and anode electrodes, decreasing the risk of lithium plating in the battery, and improving the cell's cycle performance.

[0062] In this embodiment, 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 that of the second active material. The proportion of the first active material in the active material layer in each region is greater than that of the second active material. Along the second direction, 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.

[0063] In this embodiment, the coefficient of thermal expansion of the first active material is smaller than that of the second active material, meaning that under the same temperature or volume change, the second active material expands to a greater extent. Within 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 sheet in this embodiment is a slurry with the first active material as the main component. Specifically, the intermediate region (e.g., Figure 1 The middle region (the first region) contains more of the second active material than the two outer regions. This means that the middle region has more material with a high coefficient of expansion (the second active material), resulting in greater volume expansion during discharge. Furthermore, since the temperature in the middle region is also higher than on the outer regions during discharge, the temperature-induced expansion effect is more pronounced due to the higher content of the second active material in the middle region.

[0064] By setting the content of the first active material and the second active material in the above embodiments, it is possible to use more second active material with a high expansion coefficient in the middle region in a scenario where the first active material with a small expansion coefficient is the main system. This results in the expansion coefficient of the active material layer in the first region being greater than that in the active material layers on both sides of the first region. This active material distribution scheme can achieve greater expansion in the middle region, thereby balancing the stress and volume changes of the anode and cathode plates inside the battery and improving the performance and safety of the battery.

[0065] In this embodiment, 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 that of the second active material. The proportion of the first active material in the active material layer in each region is smaller than that of the second active material. Along the second direction, the content of the first active material in the active material layer of the first region is smaller than the content of the first active material in the active material layers of the regions on both sides of the first region.

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

[0067] By setting the content of the first active material and the second active material in the above embodiments, it is possible to use more second active material with a high expansion coefficient in the middle region in a scenario where the second active material with a large expansion coefficient is the main system. This results in the expansion coefficient of the active material layer in the first region being greater than that in the active material layers on both sides of the first region. This active material distribution scheme can achieve greater expansion in the middle region, thereby balancing the stress and volume changes 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 of the central region of the cathode in this embodiment can not only reduce lithium plating on the anode electrode, but also cause the cathode electrode to be squeezed against the separator and the anode, thereby reducing the ion throughput rate and the reaction rate, thus lowering the temperature of the central region, improving the consistency of the reaction rate in each region, and alleviating the phenomenon of uneven temperature distribution of the cell during charging and discharging.

[0069] In this embodiment, the first active material includes lithium iron phosphate, and the second active material includes ternary materials.

[0070] Lithium iron phosphate (LiFePO4, hereinafter referred to as LFP) exhibits good cycle stability, maintaining relatively stable electrochemical performance through multiple charge-discharge cycles. Ternary materials (such as LiNixCoyMnzO2, hereinafter referred to as NCM) also possess good electrochemical performance and a long cycle life. In this embodiment, the ternary material mainly comprises nickel, cobalt, and manganese. By adjusting the ratio of nickel, cobalt, and manganese, different battery requirements can be met. LFP has a stable structure and a low thermal decomposition temperature; therefore, the coefficient of thermal expansion of LFP is lower than that of NCM.

[0071] For example, in the LFP system, which uses LFP as the main material and does NCM in it, the NCM content in the first region of the electrode is greater than that in the second and third regions because the coefficient of thermal expansion of NCM is higher than that of LFP.

[0072] In one example, the first region contains 90% LFP, 3% NCM, 3% binder, 3% conductive agent, and 1% plasticizer; the second region contains 1% LFP, 2% NCM, 3% binder, 3% conductive agent, and 1% plasticizer; and the third region contains 0.5% LFP, 2.5% NCM, 3% binder, 3% conductive agent, and 1% plasticizer.

[0073] For example, in an NCM system, where NCM is the main material and LFP is doped into it, because the coefficient of thermal expansion of NCM is higher than that of LFP, the LFP content in the central region of the NCM system is less than the LFP content in the two side regions, so that the proportion of NCM in the central region is larger.

[0074] In one 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 0.5% NCM, 2.5% LFP, 3% binder, 3% conductive agent, and 1% plasticizer.

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

[0076] This embodiment uses different proportions of LFP and NCM in different areas, which enables the battery to 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 this embodiment, the active material layer includes an adhesive, and along the second direction, the content of the adhesive in the active material layer of the first region is less than the content of the adhesive in the active material layers of the regions on both sides of the first region.

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

[0079] The distribution of the binder affects the electrochemical performance of the electrode. As shown in the above embodiments, the active material layer is a slurry coating with micropores, meaning that the active material contains voids and has a certain porosity. The binder reduces 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 that in the regions on both sides of the first region. That is, the porosity in the first region is higher, thus providing more space when the active material expands, further increasing the expansion. This makes the expansion of the first region greater than that of the regions on both sides. During discharge, the expansion in the middle of the cathode electrode fills the gap caused by the deintercalation of lithium ions in the anode electrode. During charging, the expansion in the middle of the anode electrode fills the gap caused by the deintercalation of lithium ions in the cathode electrode, reducing the gap between the anode and cathode, reducing the risk of lithium plating in the battery, and improving the cycle performance of the cell.

[0080] In one example, assuming the first region contains 1% adhesive, then the third region can contain 2% adhesive and the third region can contain 3% adhesive.

[0081] The above embodiments change the expansion coefficient of different regions by changing the binder content in different regions of the electrode, thereby making the expansion of the first region greater than that of the two side regions. During discharge, the expansion of the middle part of the cathode electrode fills the reduction in the middle part of the anode electrode caused by the deintercalation of lithium ions from the anode. During charging, the expansion of the middle part of the anode electrode fills the reduction in the middle part of the cathode electrode caused by the deintercalation of lithium ions from the cathode, thereby reducing the gap between the anode and cathode electrodes, reducing the risk of lithium plating in the battery, and improving the cycle performance of the cell.

[0082] In this embodiment, the method of controlling the content of binder in the active material layer of the first region to be less than the content of binder in the active material layers of the regions on both sides of the first region along the second direction can be applied to scenarios where the proportion of the first active material in the active material layer of each region is greater than the proportion 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 scenarios where the proportion of the first active material in the active material layer of each region is less than the proportion 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 this embodiment, the current collector has a first surface and a second surface arranged in opposite directions. Both the first surface and the second surface have multiple regions arranged adjacent to each other along a second direction, and the active material layer is attached to each region.

[0084] Understandably, the first surface and the second surface are two surfaces along the thickness direction of the current collector, with 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. Furthermore, the coefficient of thermal expansion of the active material layer in the first region 111 of both the first and second surfaces is greater than the coefficient of thermal expansion of the active material layers in the regions on either side of the first region. Since both achieve the purpose of this application, they should all be within the scope of protection of this application.

[0085] The above embodiments can achieve coating on both sides of the current collector to form a double-sided coated electrode, which can improve the electrode utilization rate and reduce costs.

[0086] In this embodiment, the first region is divided based on historical temperature data, which includes the temperature values ​​of individual battery cells during charging and discharging. The first region is the electrode region corresponding to the location of the maximum temperature value in the historical temperature data. The regions on both sides of the first region are divided into two parts by using a preset temperature difference as a region division gradient.

[0087] In this embodiment, the historical temperature data can be based on the charge-discharge test monitoring data of existing battery cells. By setting up several temperature sampling points on the battery cell, the temperature distribution of the battery cell during the charge-discharge process can be obtained, and the area with the highest temperature during the charge-discharge process can be identified. Then, before preparing the electrode sheet of this application, the current collector can be divided into regions, and the electrode area corresponding to the location of the maximum temperature value in the historical temperature data can be taken as the first region. That is to say, the first region of the electrode sheet in this application embodiment corresponds to the area with the highest temperature of the battery cell in actual application. 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. Thus, as can be seen from the principle of the electrode sheet in the above embodiment, the risk of lithium plating in the new battery cell made using the electrode sheet of this application is reduced, and the cell cycle performance is improved.

[0088] As described above, after the first region is determined, it can be used as a reference position, and other regions can be obtained by dividing the first region into two parts with a preset temperature difference as a gradient. For example, if the temperature corresponding to the first region is 50℃, and the preset temperature difference is 1℃, then the region can be expanded to both sides of the first region. Each time the temperature drops by 1℃, it is considered as a new region. In this way, multiple regions can be obtained by dividing the first region into two parts.

[0089] In this embodiment, the middle region of the electrode is obtained by taking the position of the highest temperature of the battery cell. This makes the division of the electrode region more experimental and improves the reliability of the electrode. By using the preset temperature difference as the region division gradient, the region can be divided into two parts on both sides of the position of the maximum temperature value, reducing the risk of local overheating of the battery.

[0090] In this embodiment, the first region is divided based on historical coin cell capacity data, which includes the specific capacity loss value of the battery cell; wherein, the first region is the electrode region corresponding to the position in the historical coin cell capacity data where the specific capacity loss value is greater than a preset value, and the regions on both sides of the first region are obtained by dividing the first region into two parts by using a preset specific capacity difference as a region division gradient.

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

[0092] Historical coin capacity data in this embodiment can be obtained through laboratory testing, such as performing charge-discharge cycles on the battery and recording the specific capacity loss value in each cycle. Alternatively, it can be collected online through a battery management system (BMS) during the use of individual battery cells.

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

[0095] Using a preset difference in specific capacity as a gradient to divide the first region into regions on both sides, this partitioning optimization helps to balance the electrochemical reactions inside the battery, reduce performance differences between different regions, and thus extend the battery's lifespan.

[0096] This embodiment uses the relationship between the specific capacity loss value of a single battery cell and a preset value to obtain the middle region of the electrode, making the electrode region division more targeted and improving the reliability of the electrode. By using the preset specific capacity difference as the region division gradient, the region with larger specific capacity loss can be divided into two parts, reducing the performance difference between different regions and thus extending the battery's service life.

[0097] In this embodiment of the 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 located on both sides of the first region.

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

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

[0100] In the embodiments of this application, Figure 3 This is another schematic diagram of the structure of the electrode provided in some embodiments of this application. Figure 4 This is a schematic diagram of the structure of a battery cell formed from electrode sheets, provided for some embodiments of this application.

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

[0102] The fourth region 114 forms the electrode 40 such as Figure 4 As shown, the fourth region 114 is adjacent to the second region 112, meaning the second region 112 is located at the top of the battery. Since the upper part of the cell, near the tabs, is at the edge of the battery, its heat dissipation performance is good. The first region 111 is located in the middle of the cell, so the third region 113 is located at the bottom of the cell, away from the tabs 40. The bottom of the cell is surrounded by the casing, so the heat dissipation of the third region is less than that of the second region. Therefore, in this embodiment, the coefficient of thermal expansion of the active material layer in the first region 111 is greater than that in the third region 113, and the coefficient of thermal expansion of the active material layer in the third region 113 is greater than that in the second region 112.

[0103] This embodiment can better match the temperature distribution of the battery cell in actual applications. It performs gradient zoning based on the actual usage of the battery cell, so that the central area with high temperature has a large expansion coefficient, the lower part is next, and the upper part has the smallest expansion coefficient. This can optimize the battery design, improve battery performance, extend life, and enhance safety.

[0104] The electrode sheet provided in the embodiments of this application will be described below with a specific example.

[0105] like Figure 4 As shown, the electrode 10 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 fourth region 114, a second region 112, a first region 111, and a third region 113 arranged sequentially adjacent to each other along a second direction. The fourth region 114 is used to form an electrode tab.

[0106] The expansion coefficient of the first region 111 is greater than that 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 that of the active material layer of the third region 113. Therefore, during the process of lithium ion insertion 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. As a result, the expansion degree of the first region increases. During the discharge process, the expansion amount in the middle of the cathode electrode can be used to fill the reduction in the middle of the anode electrode caused by the deintercalation of lithium ions. During the charging process, the expansion amount in the middle of the anode electrode can be used to fill the reduction in the middle of the cathode electrode caused by the deintercalation of lithium ions. This reduces the gap between the anode and cathode electrodes, reduces the risk of lithium plating in the battery, and improves the cycle performance of the cell.

[0107] In this process, the number of regions coated with the active material layer on the current collector can be greater than three. The specific number of regions can be determined by using the electrode region corresponding to the location of the maximum temperature value in historical temperature data as the first region. After obtaining the first region, other regions are obtained by dividing the first region into two parts on both sides using a preset temperature difference as a dividing gradient. For example, if the temperature corresponding to the first region is 50℃, and the preset temperature difference is 1℃, then the first region is expanded to both sides, and each temperature drop of 1℃ is considered as a new region. This process of dividing the first region into two parts on both sides yields multiple regions.

[0108] The specific number of regions can be determined by using the pole region corresponding to the location where the specific capacity loss value is greater than a preset value as the first region. After obtaining the first region, the other regions are obtained by dividing the first region into two parts using a preset specific capacity difference as a dividing gradient. For example, the preset specific capacity difference can be 10% of the initial specific capacity as a dividing gradient.

[0109] Figure 5This paper presents a comparison chart of cell parameter results under different material ratios according to embodiments of this application. Figure 5 The serial number indicates different groups. The proportion of high expansion coefficient material or the reduction of binder refers to the proportion of high expansion coefficient material or binder in the upper, middle and lower regions of the electrode, taking a three-region electrode as an example.

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

[0111] If the second region contains 0% NCM, the first region contains 3% NCM, and the third region contains 1% NCM, the corresponding temperatures for the upper, middle, and lower regions are 46℃, 50℃, and 46℃, respectively, and the corresponding capacity retention rate is 88%. Compared with the first set of data, the temperature difference between the three regions is reduced, indicating better performance.

[0112] If the second region contains 0% NCM, the first region contains 5% NCM, and the third region contains 3% NCM, the corresponding temperatures at the top, middle, and bottom are 47℃, 49℃, and 47℃, respectively, and the corresponding capacity retention rate is 92%. Compared with the data from the first and second groups, the temperature difference between the three regions is further reduced, which can solve the problem of uneven battery temperature distribution.

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

[0114] This application provides an electrode where the coefficient of thermal expansion of the active material layer in the middle region is greater than that in the active material layers on both sides. When this electrode is used as a cathode electrode, lithium ions embed into the cathode electrode during discharge, accelerating the cathode electrode's reaction rate. Because the coefficient of thermal expansion in the middle of the electrode is greater than that on the sides, the expansion in the middle is greater. This expansion in the middle of the cathode electrode compensates for the reduction in the middle of the anode electrode caused by lithium ion deintercalation, thus reducing the gap between the cathode and anode electrodes. When this electrode is used as an anode electrode, lithium ions deintercalate from the cathode electrode and embed into the anode electrode during charging, accelerating the anode electrode's reaction rate. Because the coefficient of thermal expansion in the middle of the electrode is greater than that on the sides, the expansion in the middle is greater. This expansion in the middle of the anode electrode compensates for the reduction in the middle of the anode electrode caused by lithium ion deintercalation, reducing the gap between the cathode and anode electrodes, reducing the risk of lithium plating in the battery, and improving the cell's cycle performance.

[0115] Figure 6 This illustration shows a schematic diagram of the electrode coating system provided in an embodiment of this application. The electrode coating system is used to prepare the electrodes described in the above embodiments. The system includes: a plurality of coating dies arranged side-by-side along a second direction (e.g., ...). Figure 6 The second coating die 602, the first coating die 601, and the third coating die 603 are connected to a slurry storage tank (e.g., a slurry storage tank). Figure 6 The second slurry storage tank 612, the first slurry storage tank 611, and the third slurry storage tank 613 are included. The current collector extends along a first direction, and the surface of the current collector has multiple regions arranged adjacent to each other along a second direction. The second direction is perpendicular to the first direction. The regions of the slurry storage tank, the coating die head, and the surface of the current collector correspond one-to-one. Among them, 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 head includes a first coating die head 601, a second coating die head 602, and a third coating die head 603. The second coating die head 602, the first coating die head 601, and the third coating die head 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 head 602, the first coating die head 601, and the third coating die head 603 also correspond to the second region 112, the first region 111, and the third region 113, respectively.

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

[0118] Conveying device ( Figure 6 (Not shown in the image), the conveying device is used to convey the current collector along a first direction; the coating die is disposed at one end of the conveying device and is used to coat the surface of the current collector with slurry. In this embodiment, the conveying device can be a conveying assembly consisting of a conveyor belt and gears, such as... Figure 6 As shown, the coating die is set at one end of the current collector. When the current collector is conveyed along the first direction, the slurry in the coating die will be coated on the current collector, thereby preparing the electrode.

[0119] Controller ( Figure 6 (Not shown in the image) is used to control the conveying device and the coating die head. The coating die head is used to coat the slurry in the slurry storage tank onto the current collector to form the aforementioned electrode sheet. For example, the controller can control the start and stop of the conveying device, and control the opening and closing of the coating die head, etc.

[0120] The system in this embodiment can precisely control the expansion coefficient of the slurry in different regions by setting up a coating die head and a corresponding slurry storage tank for each region individually. This differentiated control of the slurry expansion coefficient in the first region and its two adjacent regions, with the expansion coefficient of the slurry in the first region being greater than that in the two adjacent regions, allows for the fabrication of electrode sheets that can solve the problem of uneven temperature distribution in batteries.

[0121] In the embodiments of this application, such as Figure 6 As shown, the coating die head includes a first coating die head 601, a second coating die head 602, and a third coating die head 603. The second coating die head 602, the first coating die head, and the third coating die head 603 are arranged sequentially along a second direction. The second coating die head 602, the first coating die head 601, and the third coating die head 603 are respectively connected to a second slurry storage tank 612, a first slurry storage tank 611, and a third slurry storage tank 613. The first coating die head 601 is correspondingly arranged with the first region 111. The expansion coefficient of the slurry in the first slurry storage tank 611 is greater than that 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 that 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 region 112, the first region 111, and the third region 113, respectively.

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

[0124] Thus, on the electrode sheet coated using this system, the coefficient of thermal expansion of the active material layer in the first region 111 is greater than that in the third region 113, and the coefficient of thermal expansion of the active material layer in the third region 113 is greater than that in the second region 112. This allows for a closer fit to the temperature distribution of the battery cell in actual applications. By creating a gradient zone based on the actual usage of the individual battery cells, the central region with the highest temperature has a larger coefficient of thermal expansion, followed by the lower region, and the upper region has the smallest coefficient of thermal expansion. This optimizes the battery made using this electrode sheet, improving battery performance, extending lifespan, and enhancing safety.

[0125] This application provides a battery cell, which includes an electrode assembly, an electrolyte, and a casing. The electrode assembly and the electrolyte are housed in an accommodating space inside the casing. The electrode assembly includes a first electrode, a second electrode, and a separator. The separator is disposed between the first electrode and the second electrode. At least one of the first electrode and the second electrode is the electrode provided in the above embodiment.

[0126] Specifically, the battery cell 20 refers to the smallest unit that makes up the battery. For example... Figure 7The battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components. The end cap 21 is a component that covers the opening of the housing 22 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the end cap 21 can be adapted to the shape of the housing 22 to fit it. 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 less prone to deformation under pressure and impact, giving the battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminals 21a can be used for electrical connection with the electrode assembly 23 to output or input electrical energy to the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The end cap 21 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. This application embodiment does not impose any special restrictions on this.

[0127] In some embodiments, an insulating element may be provided inside the end cap 21. This insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. Exemplarily, the insulating element can 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 can be used to contain the electrolyte of the electrode assembly 23 and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 can be used to close the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connection surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can have various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can 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. This application embodiment does not impose any special restrictions on this.

[0128] In this embodiment, electrode assembly 23 is a component within the battery cell where an electrochemical reaction occurs. This electrode assembly can be one of the embodiments described in this application. Figure 4The electrode structure is shown. The housing may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking anode and cathode electrodes 10, i.e., the first and second electrodes mentioned above, and typically a separator is provided between the anode and cathode electrodes 10. The portions of the anode and cathode electrodes 10 with active material layers constitute the main body of the electrode assembly 23, while the portions of the anode and cathode electrodes 10 without active material layers each constitute tabs 23a. The anode and cathode tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery, the anode and cathode active materials react with the electrolyte, and the tabs 23a connect to the electrode terminals to form a current loop.

[0129] The first and second electrodes are those described in any of the above embodiments. The coefficient of expansion of the active material layer in the middle region of the electrode is greater than that in the active material layers on both sides. Therefore, when this electrode is used as a cathode electrode, lithium ions embed into the cathode electrode during discharge, accelerating the cathode electrode's reaction rate. Because the coefficient of expansion in the middle of the electrode is greater than that on both sides, the expansion in the middle increases. This expansion in the middle of the cathode electrode compensates for the reduction in the middle of the anode electrode caused by the deintercalation of lithium ions from the anode, reducing the gap between the cathode and anode electrodes. Similarly, when this electrode is used as an anode electrode, lithium ions deintercalate from the cathode electrode and embed into the anode electrode during charging, accelerating the anode electrode's reaction rate. Because the coefficient of expansion in the middle of the electrode is greater than that on both sides, the expansion in the middle increases. This expansion in the middle of the anode electrode compensates for the reduction in the middle of the anode electrode caused by the deintercalation of lithium ions from the cathode, reducing the gap between the cathode and anode electrodes, reducing the risk of lithium plating in the battery, and improving the cell's cycle performance.

[0130] This application provides a battery device including the aforementioned battery cell. The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include one or more battery cells, and multiple battery cells may be connected in series, parallel, or mixed connections via a busbar.

[0131] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells; as an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form a single module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0132] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0133] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0134] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0135] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0136] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0137] As an example, the housing can be part of the vehicle's chassis structure. For instance, the housing's roof can be at least part of the vehicle's floor, or the housing's frame can be at least part of the vehicle's crossbeams and longitudinal beams.

[0138] In some embodiments, the battery device refers to an energy storage device, which includes a housing with a door on at least one side. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0139] This application provides an electrical device including the aforementioned battery device, which is used to supply power to the electrical device.

[0140] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery cells and battery devices, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships and spacecraft, etc. For example, spacecraft include airplanes, rockets, space shuttles and spacecraft.

[0141] It should be noted that:

[0142] In the foregoing text, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0143] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0144] The embodiments of this application have been described above with reference to the accompanying drawings. These are merely specific implementations of this application, but this application is not limited to the specific implementations described above. The specific implementations described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. An electrode sheet, characterized in that, include: Current collector and active material layer; The current collector extends along a first direction, and the surface of the current collector has a plurality of regions arranged adjacent to each other along a second direction, the second direction being perpendicular to the first direction, and the active material layer is attached to each region; The second direction is the width direction of the current collector; 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 layers in the regions on both sides of the first region, and the first region is the region where the current collector is located at the middle position along the second direction; The first region is divided based on historical temperature data or historical coin capacity data. The historical temperature data includes the temperature value of a single battery cell during the charging and discharging process; the historical coin capacity data includes the specific capacity loss value of a single battery cell. When the electrode is used as a cathode electrode, the expansion of the central part of the cathode electrode during discharge compensates for the reduction in the anode electrode; when the electrode is used as an anode electrode, the expansion of the central part of the anode electrode during charging compensates for the reduction in the central part of the cathode electrode.

2. The electrode sheet 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 that of the second active material. The proportion of the first active material in the active material layer in each region is greater than that of the second active material. Along the second direction, 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.

3. The electrode sheet 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 that of the second active material. The proportion of the first active material in the active material layer in each region is smaller than that of the second active material. Along the second direction, 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.

4. The electrode sheet according to claim 3, characterized in that, The first active material includes lithium iron phosphate, and the second active material includes ternary materials.

5. The electrode sheet according to any one of claims 1-4, characterized in that, The active material layer includes an adhesive, and along the second direction, the content of the adhesive in the active material layer of the first region is less than the content of the adhesive in the active material layers of the regions on both sides of the first region.

6. The electrode sheet according to any one of claims 1-4, characterized in that, The current collector has a first surface and a second surface arranged in opposite directions. Both the first surface and the second surface have multiple regions arranged adjacent to each other along the second direction, and the active material layer is attached to each region.

7. The electrode sheet according to claim 5, characterized in that, The first region was divided based on historical temperature data; The first region is the electrode region corresponding to the location of the maximum temperature value in the historical temperature data, and the regions on both sides of the first region are obtained by dividing the first region into two parts by using a preset temperature difference as a region division gradient.

8. The electrode sheet according to claim 5, characterized in that, The first region was divided based on historical truncation capacity data; The first region is the electrode region corresponding to the position where the specific capacity loss value in the historical coin capacity data is greater than a preset value. The regions on both sides of the first region are obtained by dividing the first region into two parts using a preset specific capacity difference as a region division gradient.

9. The electrode sheet according to claim 5, characterized in that, The plurality of regions include a first region, a second region, and a third region, with the second region and the third region located on either side of the first region along the second direction.

10. The electrode sheet according to claim 9, characterized in that, The surface of the current collector also has a fourth region for forming a tab, the fourth region being adjacent to the second region; The coefficient of expansion of the active material layer in the first region is greater than that in the third region, and the coefficient of expansion of the active material layer in the third region is greater than that in the second region.

11. A coating system, characterized in that, The system includes: Multiple coating dies are arranged side-by-side along a second direction, each die connected to a slurry storage tank. The coating dies apply the slurry from the storage tank onto a current collector. The current collector extends along a first direction, and its surface has multiple adjacent regions arranged along the second direction, which is the width direction of the current collector and perpendicular to the first direction. The slurry storage tank, the coating dies, and the regions on the current collector surface correspond one-to-one. The coefficient of thermal expansion of the slurry in the storage tank corresponding to the first region is greater than the coefficient of thermal expansion of the slurry in the storage tanks corresponding to the regions on either side of the first region. The first region is defined based on historical temperature data or historical coin capacity data. The historical temperature data includes the temperature values ​​of individual battery cells during charging and discharging; the historical coin capacity data includes the specific capacity loss values ​​of individual battery cells. A conveying device is used to convey the current collector along the first direction; the coating die head is disposed at one end of the conveying device and is used to coat the current collector surface with slurry. A controller is used to control the conveying device and the coating die head to form an electrode sheet, wherein when the electrode sheet is used as a cathode electrode sheet, the expansion of the central part of the cathode electrode sheet during discharge compensates for the reduction of the anode electrode sheet; when the electrode sheet is used as an anode electrode sheet, the expansion of the central part of the anode electrode sheet during charging compensates for the reduction of the central part of the cathode electrode sheet.

12. The coating system according to claim 11, characterized in that, The coating die head includes 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 arranged sequentially 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 correspondingly to the first region. The expansion coefficient of the slurry in the first slurry storage tank is greater than that in the third slurry storage tank, and the expansion coefficient of the slurry in the third slurry storage tank is greater than that in the second slurry storage tank.

13. A single battery cell, characterized in that, The battery cell includes an electrode assembly, an electrolyte, and a housing, wherein the electrode assembly and the electrolyte are housed within an accommodating space inside the housing; The electrode assembly includes a first electrode, a second electrode, and a diaphragm, wherein the diaphragm is disposed between the first electrode and the second electrode, and at least one of the first electrode and the second electrode is an electrode as described in any one of claims 1-10.

14. A battery device, characterized in that, Includes the battery cell as described in claim 13.

15. An electrical appliance, characterized in that, Includes the battery device as described in claim 14, the battery device being used to supply power to the electrical device.

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