Electrode plate, preparation method of electrode plate, battery and electric equipment

Abstract

The invention discloses an electrode plate, a preparation method of the electrode plate, a battery and electric equipment. The electrode plate comprises a base layer and a first active layer, and the first active layer is located on the base layer; the first active layer comprises a middle region and an edge region, the edge region surrounds the middle region, and based on the same unit area, the mass ratio of the active material of the middle region is larger than the mass ratio of the active material of the edge region. Through the mode, the ion deintercalation quantity of the middle region of the first active layer can be improved, polarization is reduced, and the cycle life of the cylindrical battery is prolonged.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to an electrode sheet, a method for preparing the electrode sheet, a battery and an electrical device. Background Art

[0002] With the continuous development of new energy technologies, power batteries are widely used in various consumer electronic products, electric vehicles, aerospace and other fields. According to the shape of the battery, power batteries include cylindrical batteries, soft-pack batteries and square batteries. With the development of technology, cylindrical batteries with larger diameters and longer lengths have been developed. However, as the size of cylindrical batteries increases, initial wetting is difficult, and during long cycles, the electrolyte is easily squeezed out. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art. Summary of the invention

[0003] The main technical problem solved by the present application is to provide an electrode sheet, a method for preparing the electrode sheet, a battery and an electrical device, which can increase the amount of ion extraction and extraction in the middle area of ​​the first active layer, reduce polarization, and increase the cycle life of the cylindrical battery.

[0004] In order to solve the above technical problems, a technical solution adopted in this application is: to provide an electrode sheet, the electrode sheet includes a base layer and a first active layer, the first active layer is located on the base layer; the first active layer includes a middle area and an edge area, the edge area surrounds the middle area, and based on the same unit area, the mass proportion of the active material in the middle area is greater than the mass proportion of the active material in the edge area. Through this arrangement, the ion deintercalation amount in the middle area of ​​the first active layer can be increased, polarization can be reduced, the cycle life of the cylindrical battery can be increased, and the battery dynamics can be improved.

[0005] In one embodiment, the porosity of the middle area is greater than that of the edge area. This arrangement can improve the wetting effect of the middle area, effectively improve the initial wetting difficulty, especially the problem of very long wetting time in the middle axial area of ​​the cylindrical battery. Furthermore, it can also improve the liquid retention capacity of the middle area, reduce the degree of electrolyte extrusion, and thus reduce polarization, effectively improving the problem of lithium precipitation in the middle area.

[0006] In one embodiment, the compaction density of the middle region is less than the compaction density of the edge region. The porosity of the middle region is regulated by reducing the compaction density and increasing the active material content. That is, although the porosity of the middle region is increased, the active material content is not reduced. The capacity of the battery can be increased on the basis of improving the wetting effect and liquid retention capacity of the middle region.

[0007] In one embodiment, the electrode sheet further includes a second active layer, which is located on a side of the first active layer away from the base layer; based on the same unit area, the mass proportion of the active material in the second active layer is greater than the mass proportion of the active material in the edge area. This arrangement can increase the capacity of the battery.

[0008] In one embodiment, the porosity of the second active layer is greater than the porosity of the edge region. This arrangement can increase the contact area between the active material and the electrolyte, improve the infiltration effect and liquid retention capacity of the electrolyte, and further increase the active ion migration rate, reduce the polarization internal resistance, and improve the rate performance of the electrode.

[0009] In one embodiment, the compaction density of the second active layer is less than the compaction density of the edge region. The porosity of the second active layer is regulated by reducing the compaction density and increasing the content of the active material. That is, although the porosity of the second active layer is increased, the content of the active material is not reduced. The capacity of the battery can be increased on the basis of improving the wetting effect and liquid retention capacity of the second active layer.

[0010] In one embodiment, the middle region is formed by extending the second active layer. This arrangement can simplify the preparation process and reduce production costs.

[0011] In one embodiment, the mass content of active material in the edge region is 94%-96%.

[0012] In one embodiment, the mass content of the active material in the second active layer is 95%-97%. By regulating the content of the active material in the edge region and the active material in the second active layer, the dynamic performance of the battery is improved.

[0013] In one embodiment, the ratio of the porosity of the second active layer to the porosity of the edge region is 2:1-1:1.

[0014] In one embodiment, the ratio of the compaction density of the second active layer to the compaction density of the edge region is 1:1-1:1.5. This configuration can improve the capacity of the battery while improving the wetting effect and liquid retention capacity of the middle region.

[0015] In one embodiment, the edge region of the first active layer includes a first active material, and the second active layer includes a second active material, and the particle size of the second active material is smaller than that of the first active material. This arrangement is conducive to forming an active layer with a high mass ratio of active materials, high porosity, and low compaction density. This improves the ionic conductivity of the electrode material, thereby improving the overall conductivity of the electrode, improving the battery rate performance, and also improving the battery capacity.

[0016] In one embodiment, the specific surface area of ​​the second active material is greater than that of the first active material. This arrangement is conducive to forming an active layer with a high mass ratio of active materials, high porosity, and low compaction density. This increases the contact area between the active material and the electrolyte, improves the infiltration effect and liquid retention capacity of the electrolyte, thereby reducing polarization and effectively improving the problem of lithium precipitation.

[0017] In one embodiment, the ratio of the particle size of the second active material to the particle size of the first active material is 1:1-1:7.

[0018] In one embodiment, the ratio of the specific surface area of ​​the second active material to the specific surface area of ​​the first active material is 3:1-1:1. This arrangement is conducive to forming an active layer with a high mass ratio of active materials, high porosity, and low compaction density. This increases the contact area between the active material and the electrolyte, improves the infiltration effect and liquid retention capacity of the electrolyte, thereby reducing polarization and effectively improving the problem of lithium precipitation.

[0019] In one embodiment, in the width direction, the length of the middle area is L1, the total length of the edge area is L2, and 0<L1 / L2<0.6. This arrangement can take into account the wetting effect and liquid retention capacity of the electrode sheet and the capacity of the battery; so that the capacity of the battery is increased on the basis of improving the wetting effect and liquid retention capacity of the electrode sheet.

[0020] In one embodiment, in the height direction, the length of the middle area is L3, the total length of the edge area is L4, and 0<L3 / L4<0.5. This arrangement can take into account the wetting effect and liquid retention capacity of the electrode sheet and the capacity of the battery; so that the energy density of the battery is improved on the basis of improving the wetting effect and liquid retention capacity of the electrode sheet.

[0021] In one embodiment, the electrode sheet is a positive electrode sheet, and the positive electrode sheet includes a base layer and a first positive electrode active layer located on the base layer, and the first positive electrode active layer includes an intermediate area and an edge area, wherein the porosity of the intermediate area of ​​the first positive electrode active layer is ≥15%, which can be selected as 15%-20%. The porosity of the edge area of ​​the first positive electrode active layer is ≥10%, which can be selected as 10%-15%. This arrangement can improve the wetting effect of the intermediate area, effectively improve the initial wetting difficulty, especially the problem of very long wetting time in the axial area in the middle of the cylindrical battery. Furthermore, it is also possible to improve the liquid retention capacity of the intermediate area, reduce the degree of electrolyte extrusion, and thereby reduce polarization, effectively improving the problem of lithium precipitation in the intermediate area.

[0022] In one embodiment, the coating amount of the first positive electrode active layer in the middle region and the edge region is 0.1-0.2 g / 1540.25 mm 2 This configuration can increase the battery capacity.

[0023] In one embodiment, the thickness of the middle region and the edge region of the first positive electrode active layer is 30-60 μm. This configuration can improve the energy density of the battery.

[0024] In one embodiment, the compaction density of the middle region of the first positive electrode active layer is 2.0-2.2 g / cm³. The compaction density of the edge region of the first positive electrode active layer is 2.2-2.5 g / cm³. This arrangement can improve the capacity of the battery while improving the wetting effect and liquid retention capacity of the middle region.

[0025] In one embodiment, the edge region of the first positive electrode active layer includes a first positive electrode active material, and the particle size D of the first positive electrode active material is V 50 is 1000-2000 nm. This setting can improve the ionic conductivity of the electrode material, thereby improving the overall conductivity of the electrode, improving the battery rate performance, and at the same time increasing the battery capacity.

[0026] In one embodiment, the specific surface area of ​​the first positive electrode active material is 10-15 m 2 This arrangement can increase the contact area between the active material and the electrolyte, improve the infiltration effect and liquid retention capacity of the electrolyte, thereby reducing polarization and effectively improving the problem of lithium precipitation.

[0027] In one embodiment, the first positive electrode active material includes one or more of lithium iron phosphate, nano lithium iron phosphate, lithium iron manganese phosphate, lithium manganese oxide, lithium cobalt oxide, ternary materials, and lithium-rich manganese-based materials. This configuration can improve the energy density of the battery.

[0028] In one embodiment, the positive electrode plate further includes a second positive electrode active layer, the second positive electrode active layer is located on the side of the first positive electrode active layer away from the base layer, and the porosity of the second positive electrode active layer is ≥15%, which can be selected as 15%-20%. This arrangement can improve the wetting effect of the middle zone, effectively improve the initial wetting difficulty, especially the problem of very long wetting time in the middle axial area of ​​the cylindrical battery. Furthermore, it can also improve the liquid retention capacity of the middle zone, reduce the degree of electrolyte extrusion, thereby reducing polarization, and effectively improve the problem of lithium precipitation in the middle zone.

[0029] In one embodiment, the coating amount of the second positive electrode active layer is 0.1-0.2 g / 1540.25 mm 2 This configuration can increase the battery capacity.

[0030] In one embodiment, the thickness of the second positive electrode active layer is 30-60 μm. This configuration can improve the energy density of the battery.

[0031] In one embodiment, the compaction density of the second positive electrode active layer is in the range of 2.0-2.2 g / cm³. This configuration can improve the capacity of the battery while improving the wetting effect and liquid retention capacity of the intermediate region.

[0032] In one embodiment, the second positive electrode active layer includes a second positive electrode active material, and the particle size D of the second positive electrode active material is V 50 is 300-900 nm. This setting can improve the ionic conductivity of the electrode material, thereby improving the overall conductivity of the electrode, improving the battery rate performance, and at the same time increasing the battery capacity.

[0033] In one embodiment, the specific surface area of ​​the second positive electrode active material is 19-30 m 2 This arrangement can increase the contact area between the active material and the electrolyte, improve the infiltration effect and liquid retention capacity of the electrolyte, thereby reducing polarization and effectively improving the problem of lithium precipitation.

[0034] In one embodiment, the second positive electrode active material includes one or more of lithium iron phosphate, nano lithium iron phosphate, lithium iron manganese phosphate, lithium manganese oxide, lithium cobalt oxide, ternary materials, and lithium-rich manganese-based materials. This configuration can improve the energy density of the battery.

[0035] In one embodiment, the electrode sheet is a negative electrode sheet, and the negative electrode sheet includes a base layer and a first negative electrode active layer located on the base layer, and the first negative electrode active layer includes an intermediate region and an edge region, wherein the porosity of the intermediate region of the first negative electrode active layer is ≥25%, which can be selected as 25%-29%. The porosity of the edge region of the first negative electrode active layer is ≥20%, which can be selected as 20%-24%. This arrangement can improve the wetting effect of the intermediate region, effectively improve the initial wetting difficulty, especially the problem of very long wetting time in the axial region in the middle of the cylindrical battery. Furthermore, it is also possible to improve the liquid retention capacity of the intermediate region, reduce the degree of electrolyte extrusion, and thereby reduce polarization, effectively improving the problem of lithium precipitation in the intermediate region.

[0036] In one embodiment, the coating amount of the first negative electrode active layer in the middle region and the edge region is 0.05-0.09 g / 1540.25 mm 2 This configuration can increase the battery capacity.

[0037] In one embodiment, the thickness of the middle region and the edge region of the first negative electrode active layer is 25-60 μm. This configuration can improve the energy density of the battery.

[0038] In one embodiment, the compaction density of the middle region of the first negative electrode active layer is 1.2-1.3 g / cm³. The compaction density of the edge region of the first negative electrode active layer is 1.3-1.6 g / cm³. This arrangement can improve the capacity of the battery while improving the wetting effect and liquid retention capacity of the middle region.

[0039] In one embodiment, the edge region of the first negative electrode active layer comprises a first negative electrode active material, wherein the particle size D of the first negative electrode active material is V 50 is 10-15 μm. This setting can improve the ionic conductivity of the electrode material, thereby improving the overall conductivity of the electrode, improving the battery rate performance, and at the same time increasing the battery capacity.

[0040] In one embodiment, the specific surface area of ​​the first negative electrode active material is 1.0-2.5 m 2 This arrangement can increase the contact area between the active material and the electrolyte, improve the infiltration effect and liquid retention capacity of the electrolyte, thereby reducing polarization and effectively improving the problem of lithium precipitation.

[0041] In one embodiment, the first negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, and tin-based materials. This configuration can improve the energy density of the battery.

[0042] In one embodiment, the negative electrode plate further includes a second negative electrode active layer, which is located on a side of the first negative electrode active layer away from the base layer, wherein the porosity of the second negative electrode active layer is ≥25%, which may be 25%-29%. This arrangement can improve the wetting effect of the middle zone, effectively improve the initial wetting difficulty, especially the problem of very long wetting time in the middle axial area of ​​the cylindrical battery. Furthermore, it can also improve the liquid retention capacity of the middle zone, reduce the degree of electrolyte extrusion, and thereby reduce polarization, effectively improving the problem of lithium precipitation in the middle zone.

[0043] In one embodiment, the coating amount of the second negative electrode active layer is 0.05-0.09 g / 1540.25 mm 2 This configuration can increase the battery capacity.

[0044] In one embodiment, the thickness of the second negative electrode active layer is 25-60 μm. This configuration can improve the energy density of the battery.

[0045] In one embodiment, the compaction density of the second negative electrode active layer is in the range of 1.2-1.3 g / cm³. This configuration can improve the capacity of the battery while improving the wetting effect and liquid retention capacity of the middle region.

[0046] In one embodiment, the second negative electrode active layer includes a second negative electrode active material, wherein the particle size D of the second negative electrode active material is V 50 is 5-10 μm. This setting can improve the ionic conductivity of the electrode material, thereby improving the overall conductivity of the electrode, improving the battery rate performance, and at the same time increasing the battery capacity.

[0047] In one embodiment, the contact area between the active material and the electrolyte can be increased, the wetting effect and the liquid retention capacity of the electrolyte can be improved, and the polarization can be reduced, thereby effectively improving the problem of lithium precipitation.

[0048] In one embodiment, the second negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, and tin-based materials. This configuration can improve the energy density of the battery.

[0049] In order to solve the above technical problems, another technical solution adopted in the present application is: to provide a method for preparing an electrode sheet, including providing a base layer, a first electrode slurry and a second electrode slurry; the base layer includes a middle area and an edge area, and the edge area surrounds the middle area; the mass proportion of the active material in the first electrode slurry is less than the mass proportion of the active material in the second electrode slurry; the first electrode slurry is used to form an active layer in the edge area, and the second electrode slurry is used to form an active layer in the middle area. The prepared electrode sheet can improve the capacity of the battery on the basis of improving the wetting effect and liquid retention capacity of the middle area.

[0050] In one embodiment, the mass content of the active material in the first electrode slurry is 94%-96%. This configuration can increase the capacity and cycle life of the battery and improve the dynamics of the battery.

[0051] In one embodiment, the mass content of the active material in the second electrode slurry is 95%-97%. This configuration can increase the capacity and cycle life of the battery and improve the dynamics of the battery.

[0052] In order to solve the above technical problems, another technical solution adopted in the present application is: to provide a battery, the battery comprising the electrode sheet of any of the aforementioned embodiments, or the electrode sheet prepared by the preparation method of the electrode sheet of any of the aforementioned embodiments.

[0053] In order to solve the above technical problems, another technical solution adopted by the present application is to provide an electric device, which includes the above battery. The electric device has at least the same advantages as the battery.

[0054] 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

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0056] Figure 1 is a schematic diagram of an exploded structure of a battery cell according to one or more embodiments; Figure 2 is a schematic structural diagram of an electrode sheet according to one or more embodiments; Figure 3 is another exploded structural schematic diagram of a battery cell according to one or more embodiments; Figure 4 is another schematic structural diagram of an electrode sheet according to one or more embodiments; Figure 5 is a schematic diagram of an exploded structure of a battery according to one or more embodiments; Figure 6 is a schematic diagram of the structure of a vehicle according to one or more embodiments.

[0057] In the attached figure: 1000, vehicle; 300, motor; 200, controller; 100, battery; 10, housing; 11, first part; 12, second part; 20, battery cell; 21, end cap; 22, housing; 23, electrode assembly; 231, positive electrode plate; 233, negative electrode plate; 235, separator.

[0058] 40. Electrode sheet; 41. Base layer; 43. First active layer; 431. Middle region; 433. Edge region; 45. Second active layer. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and effect of the present application clearer and more specific, the following will describe the embodiments of the technical solution of the present application in detail with reference to 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.

[0060] 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.

[0061] 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 term "multiple" refers to more than two (including two), similarly, "multiple groups" refers to more than two (including two groups), and "multiple pieces" refers to more than two (including two pieces), unless otherwise clearly and specifically defined.

[0062] 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.

[0063] 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.

[0064] Amounts, ratios and other numerical values ​​are presented herein in a range format. It should be understood that such a range format is for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly specified as range limits, but also all individual values ​​or sub-ranges encompassed within the range, as if each value and sub-range were explicitly specified.

[0065] If there is no special explanation, all steps of the present application can be performed sequentially, randomly, or in parallel, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially, or may be steps (a) and (b) performed simultaneously in parallel. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0066] With the continuous development of new energy technology, power batteries are widely used in various consumer electronic products, electric vehicles, aerospace and other fields. According to the shape of the battery, power batteries include cylindrical batteries, soft-pack batteries and square batteries. With the development of technology, cylindrical batteries have developed from traditional 18650 and 21700 to 4680 and other cylindrical batteries with larger diameters and longer lengths. However, as the size of cylindrical batteries increases, some problems are also exposed. Taking lithium batteries as an example, cylindrical lithium batteries are prone to initial wetting difficulties, especially the wetting time of the axial area in the middle of the cylindrical battery is very long, which seriously affects the production efficiency; further, the negative electrode sheet that is not fully wetted will cause lithium precipitation problems during charging and discharging. Furthermore, during the long cycle, the electrolyte in the middle of the cylindrical battery in the axial direction is easily squeezed out, and then the polarization increases, causing problems such as lithium precipitation in the middle area of ​​the cylindrical battery pole.

[0067] See also Figure 1 , Figure 1 2 is a schematic diagram of a decomposed structure of a battery cell according to one or more embodiments. A battery cell 20 refers to the smallest unit that constitutes a battery. The battery cell 20 may be square, cylindrical, etc. Each battery cell 20 may be a secondary battery or a primary battery; it may be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, a potassium-ion battery, or a magnesium-ion battery, but is not limited thereto. The following will take a lithium-ion battery as an example to describe in detail any cylindrical battery cell.

[0068] The battery cell 20 includes an electrode assembly 23 and an electrolyte, and the electrode assembly 23 includes a positive electrode sheet 231, a negative electrode sheet 233 and a separator 235. The electrode assembly 23 is mainly formed by winding the positive electrode sheet 231 and the negative electrode sheet 233, and the separator 235 is arranged between the positive electrode sheet 231 and the negative electrode sheet 233. The separator 235 is used to isolate the positive electrode sheet 231 and the negative electrode sheet 233 to prevent the positive electrode sheet 231 and the negative electrode sheet 233 from overlapping and short-circuiting. The material of the separator 235 can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without special restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without special restrictions.

[0069] The battery cell mainly relies on the movement of active ions between the positive electrode sheet and the negative electrode sheet to work. Specifically, the parts of the positive electrode sheet 231 and the negative electrode sheet 233 with active materials constitute the main body of the electrode assembly, and the parts of the positive electrode sheet 231 and the negative electrode sheet 233 without active materials each constitute the tabs. The positive tab and the negative tab can be located together at one end of the main body or at both ends of the main body respectively. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the tabs connect the electrode terminals to form a current loop.

[0070] The battery cell 20 also includes a housing, electrode terminals (not shown) and other functional components. The housing is used to accommodate the electrode assembly 23. The electrode terminals are installed in the housing. The electrode terminals are used to be electrically connected to the electrode assembly 23 to realize the charging and discharging of the battery cell. The housing includes a shell 22 and an end cap 21. The shell 22 is a cylindrical structure with one end open. The end cap 21 covers the opening of the shell 22 to form a sealed accommodation space to accommodate the electrode assembly 23, electrolyte, etc.

[0071] The end cap 21 refers to a component that fits into the opening of the shell 22 to isolate the internal environment of the cylindrical 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 fit the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as an aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the cylindrical battery cell 20 can have a higher structural strength and the safety performance can also be improved. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose special restrictions on this. Functional components such as electrode terminals can be provided on the end cap 21, and a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold value can also be provided on the end cap 21.

[0072] The shell 22 and the end cap 21 can be independent components, and an opening can be set on the shell 22, and the end cap 21 covers the opening to form the internal environment of the cylindrical battery cell 20. Without limitation, the end cap 21 and the shell 22 can also be integrated. Specifically, the end cap 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when the interior of the shell 22 needs to be encapsulated, the end cap 21 is covered on the shell 22. The shell 22 can 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.

[0073] Please refer to Figure 2 and Figure 3 , Figure 2 is a schematic diagram of a structure of an electrode sheet according to one or more embodiments, Figure 3 1 is another schematic diagram of the exploded structure of a battery cell according to one or more embodiments. The present application provides an electrode sheet 40, which includes a base layer 41 and a first active layer 43, wherein the first active layer 43 is located on the base layer 41; the first active layer 43 includes a middle region 431 and an edge region 433, wherein the edge region 433 surrounds the middle region 431, and based on the same unit area, the mass proportion of the active material in the middle region 431 is greater than the mass proportion of the active material in the edge region 433.

[0074] Among them, the base layer 41 is a conductive base layer, which can be a metal foil or a composite material, for example, a composite conductive material formed by mixing a metal material with a polymer substrate. For example, aluminum foil, copper foil, etc. can be used as the metal foil. The composite conductive material may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite conductive material can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, copper, copper alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). The base layer 41 may be in a cubic shape, having a first surface and a second surface arranged opposite to each other along its thickness direction, so as to support the arrangement of other layer structures.

[0075] The first active layer 43 includes at least an active material. The first active layer 43 may be a layered structure formed with the active material as the main material, and may be specifically a layered film. The first active layer 43 may be provided only on the first surface or the second surface of the base layer 41, or may be provided on both the first surface and the second surface of the base layer 41. The first active layer 43 may be provided directly on the surface of the base layer 41, or other functional material layers may be provided between the first active layer 43 and the base layer 41. The first active layer 43 is the main structural layer of the electrode to realize the basic functions of the battery.

[0076] Among them, the middle area 431 and the edge area 433 are relative concepts, which are only used to divide the first active layer 43 into regions, and there is no primary and secondary orientation. The mass proportion of active materials is calculated based on the mass of the active layer. The mass proportion of active materials in the middle area 431 = (total mass of active materials in the middle area) / (total mass of the first active layer in the middle area); the mass proportion of active materials in the edge area 433 = (total mass of active materials in the edge area) / (total mass of the first active layer in the edge area). Because the area of ​​the middle area 431 is not necessarily the same as the area of ​​the edge area 433, when comparing the mass content of active materials, they should be based on the same area. That is, the content of active materials in the middle area 431 of the same area size is greater than the content of active materials in the edge area 433. In order to effectively realize the function of the electrode sheet, the active materials in the middle area 431 are evenly distributed; similarly, the active materials in the edge area 433 are also evenly distributed. In other words, when comparing the mass content of active materials, the average value of each position in the same area is taken.

[0077] In this embodiment, by increasing the active material content in the middle region, the amount of ion extraction in the middle region of the first active layer can be increased, polarization can be reduced, the problem of easy lithium precipitation in the middle region of the cylindrical lithium battery can be improved, and the cycle life of the cylindrical lithium battery can be increased.

[0078] In one embodiment, the mass content of active material in the edge region is 94%-96%; and / or the mass content of active material in the middle region is 95%-97%. For example, the mass content of active material in the edge region is 94%, 94.5%, 95%, 95.5%, 96%, etc., and the mass content of active material in the middle region is 95%, 95.5%, 96%, 96.5%, 97%, etc. This arrangement can improve the dynamics of the battery and reduce polarization.

[0079] In one embodiment, the porosity of the middle region 431 is greater than the porosity of the edge region 433. By increasing the porosity of the middle region, the wetting effect of the middle region can be improved, and the initial wetting difficulty, especially the problem of very long wetting time in the middle axial region of the cylindrical battery, can be effectively improved. Furthermore, the liquid retention capacity of the middle region can be improved, the degree of electrolyte extrusion can be reduced, and polarization can be reduced, effectively improving the problem of lithium precipitation in the middle region.

[0080] In one embodiment, the compaction density of the middle region 431 is less than the compaction density of the edge region 433. The porosity of the middle region is regulated by reducing the compaction density and increasing the active material content. That is, although the porosity of the middle region is increased, the active material content is not reduced. The capacity of the battery can be increased on the basis of improving the wetting effect and liquid retention capacity of the middle region.

[0081] In one embodiment, the ratio of the porosity of the middle region to the porosity of the edge region is 2:1-1:1; and / or the ratio of the compacted density of the middle region to the compacted density of the edge region is 1:1-1:1.5. For example, the ratio of the porosity of the middle region to the porosity of the edge region is 2:1, 1.8:1, 1.5:1, 1.3:1, 1.2:1, 1:1, etc. The ratio of the compacted density of the middle region to the compacted density of the edge region is 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc.

[0082] Please continue reading Figure 3 In one embodiment, in the width direction (the Y direction shown in the figure), the length of the middle area 431 is L1, the total length of the edge area 433 is L2, and 0<L1 / L2<0.6.

[0083] Among them, the edge area 433 is divided into multiple areas by the middle area 431, and the length of the edge area 433 is the sum of the lengths of each edge area, that is, L2=L21+L22. L1 / L2 can be 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, etc. Or it can be a range composed of any two of the above values, for example, 0-0.60, 0.05-0.15, 0.15-0.30, 0.30-0.50, 0.40-0.60, etc. Through this setting, the wetting effect and liquid retention capacity of the electrode sheet and the capacity of the battery can be taken into account; so that the capacity of the battery is improved on the basis of improving the wetting effect and liquid retention capacity of the electrode sheet.

[0084] Please continue reading Figure 3 In one embodiment, in the height direction (the X direction shown in the figure), the length of the middle area 431 is L3, the total length of the edge area 433 is L4, and 0<L3 / L4<0.5.

[0085] Among them, the edge area 433 is divided into multiple areas by the middle area 431, and the length of the edge area 433 is the sum of the lengths of each edge area, that is, L4=L41+L42. L3 / L4 can be 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, etc. Or it can be a range consisting of any two of the above values, for example, 0-0.50, 0.05-0.15, 0.15-0.30, 0.20-0.45, 0.30-0.50, etc. Through this setting, the wetting effect and liquid retention capacity of the electrode sheet and the capacity of the battery can be taken into account; so that the capacity of the battery is improved on the basis of improving the wetting effect and liquid retention capacity of the electrode sheet.

[0086] See also Figure 4 , Figure 44 is another schematic diagram of the structure of the electrode sheet according to one or more embodiments. In this embodiment, the electrode sheet 40 further includes a second active layer 45, and the second active layer 45 is located on the side of the first active layer 43 away from the base layer 41; based on the same unit area, the mass proportion of the active material of the second active layer 45 is greater than the mass proportion of the active material of the edge area 433.

[0087] Specifically, the electrode sheet 40 includes a base layer 41, a first active layer 43 and a second active layer 45, wherein the first active layer 43 is located on the base layer 41, and the second active layer 45 is located on the side of the first active layer 43 away from the base layer 41. The first active layer 43 includes a middle area 431 and an edge area 433, wherein the edge area 433 surrounds the middle area 431, and based on the same unit area, the mass proportion of the active material in the middle area 431 is greater than the mass proportion of the active material in the edge area 433; the mass proportion of the active material in the second active layer 45 is greater than the mass proportion of the active material in the edge area 433. The mass proportion of the active material in the second active layer 45 is equal to the mass proportion of the active material in the middle area 431; or the mass proportion of the active material in the second active layer 45 is greater than the mass proportion of the active material in the middle area 431. In this embodiment, by providing two layers of active layers, the capacity of the battery can be increased.

[0088] In one embodiment, the porosity of the second active layer 45 is greater than the porosity of the edge region 433. This can increase the contact area between the active material and the electrolyte, improve the wetting effect and liquid retention capacity of the electrolyte, and further increase the active ion migration rate, reduce the polarization internal resistance, and improve the rate performance of the electrode.

[0089] In one embodiment, the compaction density of the second active layer 45 is less than the compaction density of the edge region 433. The porosity of the second active layer is regulated by reducing the compaction density and increasing the active material content. That is, although the porosity of the second active layer is increased, the active material content is not reduced. The capacity of the battery can be increased on the basis of improving the wetting effect and liquid retention capacity of the second active layer.

[0090] In one embodiment, the middle region 431 of the first active layer 43 is formed by extending the second active layer 45. The middle region 431 of the first active layer 43 and the second active layer 45 may be integrally formed; or the middle region 431 of the first active layer 43 may be prepared using the same raw materials and process as the second active layer 45. In this way, the preparation process can be simplified and the production cost can be reduced.

[0091] In one embodiment, the edge region of the first active layer includes a first active material, and the second active layer includes a second active material, wherein the particle size of the second active material is smaller than the particle size of the first active material. In this way, it is beneficial to form an active layer with a high mass ratio of active materials, high porosity, and low compaction density. This improves the ionic conductivity of the electrode material, thereby improving the overall conductivity of the electrode, improving the battery rate performance, and also improving the battery capacity.

[0092] In one embodiment, the edge region of the first active layer includes a first active material, and the second active layer includes a second active material, wherein the specific surface area of ​​the second active material is greater than the specific surface area of ​​the first active material. In this way, it is beneficial to form an active layer with a high mass ratio of active materials, high porosity, and low compaction density. This increases the contact area between the active material and the electrolyte, improves the infiltration effect and liquid retention capacity of the electrolyte, thereby reducing polarization and effectively improving the problem of lithium precipitation.

[0093] In one embodiment, the ratio of the particle size of the second active material to the particle size of the first active material is 1:1-1:7; and / or the ratio of the specific surface area of ​​the second active material to the specific surface area of ​​the first active material is 3:1-1:1. The ratio of the particle size of the second active material to the particle size of the first active material is 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, etc. The ratio of the specific surface area of ​​the second active material to the specific surface area of ​​the first active material is 3:1, 2.8:1, 2.5:1, 2.3:1, 2:1, 1.8:1, 1.5:1, 1.3:1, 1:1, etc.

[0094] The electrode sheet described in the above embodiments can be applied to the design of the positive electrode sheet of a cylindrical battery, and can also be applied to the design of the negative electrode sheet of a cylindrical battery.

[0095] In one embodiment, the present application provides a positive electrode plate, which includes a base layer and a first positive electrode active layer located on the base layer, wherein the first positive electrode active layer includes a middle region and an edge region.

[0096] The base layer of the positive electrode plate may be an aluminum foil layer.

[0097] The porosity of the middle region of the first positive electrode active layer is ≥15%, and may be 15%-20%, for example, 15%, 16%, 17%, 18%, 19%, 20%, etc., or a range consisting of any two of the above values, for example, 15%-17%, 17%-19%, 19%-20%, etc.

[0098] The porosity of the edge region of the first positive electrode active layer is ≥10%, and may be 10%-15%. For example, it may be 10%, 11%, 12%, 13%, 14%, 25%, etc.; or a range consisting of any two of the above values, for example, 10%-12%, 12%-14%, 14%-15%, etc.

[0099] The coating amount of the first positive electrode active layer in the middle area and the edge area is 0.1-0.2 g / 1540.25mm 2 For example, it can be 0.10 g / 1540.25 mm 2 , 0.12 g / 1540.25 mm 2 , 0.14 g / 1540.25 mm 2 , 0.16 g / 1540.25 mm 2 , 0.18g / 1540.25mm 2 , 0.2 g / 1540.25mm 2 etc.; or a range consisting of any two of the above values, for example, 0.10-0.12g / 1540.25mm 2 , 0.12-0.14 g / 1540.25mm 2 , 0.14-0.16 g / 1540.25mm 2 , 0.16-0.18 g / 1540.25mm 2 , 0.18-0.20 g / 1540.25mm 2 wait.

[0100] The thickness of the middle region and edge region of the first positive electrode active layer is 30-60 μm. For example, it can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, etc. Or it can be a range consisting of any two of the above values, for example, 30-40 μm, 40-50 μm, 50-60 μm, etc.

[0101] The compaction density of the middle region of the first positive electrode active layer is 2.0-2.2 g / cm³. For example, it can be 2.00 g / cm³, 2.05 g / cm³, 2.10 g / cm³, 2.15 g / cm³, 2.20 g / cm³, etc. Or it can be a range consisting of any two of the above values, for example, 2.00-2.10 g / cm³, 2.10-2.20 g / cm³, etc.

[0102] The compaction density of the edge region of the first positive electrode active layer is 2.2-2.5 g / cm³. For example, it may be 2.20 g / cm³, 2.25 g / cm³, 2.30 g / cm³, 2.35 g / cm³, 2.40 g / cm³, 2.45 g / cm³, 2.50 g / cm³, etc. Or it may be a range consisting of any two of the above values, for example, 2.20-2.30 g / cm³, 2.30-2.40 g / cm³, 2.40-2.50 g / cm³, etc.

[0103] In one embodiment, the positive electrode plate further includes a second positive electrode active layer, and the second positive electrode active layer is located on a side of the first positive electrode active layer away from the base layer.

[0104] The porosity of the second positive electrode active layer is ≥15%, and may be 15%-20%, for example, 15%, 16%, 17%, 18%, 19%, 20%, etc., or a range consisting of any two of the above values, for example, 15%-17%, 17%-19%, 19%-20%, etc.

[0105] The coating amount of the second positive electrode active layer is 0.1-0.2 g / 1540.25mm 2 For example, it can be 0.10 g / 1540.25 mm 2 , 0.12g / 1540.25mm 2 , 0.14g / 1540.25mm 2 , 0.16g / 1540.25mm 2 , 0.18 g / 1540.25 mm 2 , 0.2 g / 1540.25mm 2 etc.; or a range consisting of any two of the above values, for example, 0.10-0.12 g / 1540.25mm 2 , 0.12-0.14 g / 1540.25mm 2 , 0.14-0.16 g / 1540.25mm 2 , 0.16-0.18 g / 1540.25mm 2 , 0.18-0.20 g / 1540.25mm 2 wait.

[0106] The thickness of the second positive electrode active layer is 30-60 μm, for example, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, etc., or a range consisting of any two of the above values, for example, 30-40 μm, 40-50 μm, 50-60 μm, etc.

[0107] The compaction density of the second positive electrode active layer is 2.0-2.2 g / cm³. For example, it can be 2.00 g / cm³, 2.05 g / cm³, 2.10 g / cm³, 2.15 g / cm³, 2.20 g / cm³, etc. Or it can be a range consisting of any two of the above values, for example, 2.00-2.10 g / cm³, 2.10-2.20 g / cm³, etc.

[0108] By setting it in this way, the porosity of the middle area of ​​the positive electrode plate can be increased, the liquid retention capacity can be improved, and the non-uniformity of the plate after long cycles can be improved.

[0109] In one embodiment, the edge region of the first positive active layer includes the first positive active material.

[0110] The first positive electrode active material includes one or more of lithium iron phosphate, nano lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, ternary materials, and lithium-rich manganese-based materials. It can be an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds. Examples of lithium phosphates containing olivine structures may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon. Ternary materials refer to active materials containing three elements of nickel, cobalt, and manganese (or aluminum), and the molecular formula is usually Li(Ni x Co y Mn z )O2, where x+y+z=1. According to the different mixing ratios of the three elements of nickel, cobalt, manganese (or aluminum) in the cathode material, there are different ternary models, such as 523, 622 and 811. 523 refers to x:y:z=5:2:3, generally known as the ternary 5 series; 622 refers to x:y:z=6:2:2, generally known as the ternary 6 series; 811 refers to x:y:z=8:1:1, generally known as the ternary 8 series. For example, the ternary material includes Li a Ni x Co y M 1-x-y O 2-b , wherein M includes at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg and Nb, optionally, M includes at least one of Mn, Al, B, Zr, Sr, W, Mg and Nb; 0.2≤a≤1.2, -0.2≤b≤0.2; the values ​​of x and y simultaneously satisfy the following conditions: 0.70≤x≤1, 0≤y≤0.15; optionally, 0.85≤x≤1, 0≤y≤0.15; optionally, 0.92≤x≤0.98, 0<y≤0.08.

[0111] Taking lithium iron phosphate as an example, the particle size D of the first positive electrode active material is V 50 is 1000-2000 nm. For example, it can be 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1500 nm, 1700 nm, 2000 nm, etc. Or it can be a range consisting of any two of the above values, for example, 1000-1100 nm, 1100-1200 nm, 1200-1300 nm, 1300-1500 nm, 1500-1700 nm, 1700-2000 nm, etc.

[0112] Taking lithium iron phosphate as an example, the specific surface area of ​​the first positive electrode active material is 10-15 m 2 / g. For example, it can be 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g, 15 m 2 / g, etc. Or a range consisting of any two of the above values, for example, 10-11 m 2 / g, 11-12 m 2 / g, 12-13 m 2 / g, 13-14 m 2 / g, 14-15 m 2 / g, etc.

[0113] In one embodiment, the second positive electrode active layer includes a second positive electrode active material.

[0114] The second positive electrode active material includes one or more of lithium iron phosphate, nano lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, ternary materials, and lithium-rich manganese-based materials. It can be an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds. Examples of lithium phosphates containing olivine structures may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Ternary materials include Li a Ni x Co y M 1-x-y O 2-b , wherein M includes at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg and Nb, optionally, M includes at least one of Mn, Al, B, Zr, Sr, W, Mg and Nb; 0.2≤a≤1.2, -0.2≤b≤0.2; the values ​​of x and y simultaneously satisfy the following conditions: 0.70≤x≤1, 0≤y≤0.15; optionally, 0.85≤x≤1, 0≤y≤0.15; optionally, 0.92≤x≤0.98, 0<y≤0.08.

[0115] The material of the second positive electrode active material may be the same as or different from the material of the first positive electrode active material.

[0116] Taking lithium iron phosphate as an example, the particle size D of the second positive electrode active material is V 50 is 300-900 nm. For example, it can be 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, etc. Or it can be a range consisting of any two of the above values, for example, 300-400 nm, 400-500 nm, 500-600 nm, 600-700 nm, 700-800 nm, 800-900 nm, etc.

[0117] Taking lithium iron phosphate as an example, the specific surface area of ​​the second cathode active material is 19-30 m 2 / g. For example, it can be 19 m 2 / g, 21 m 2 / g, 23 m 2 / g, 25 m 2 / g, 27 m 2 / g, 30 m 2 / g, etc. Or a range consisting of any two of the above values, for example, 19-21 m 2 / g, 21-23 m 2 / g, 23-25 ​​m 2 / g, 25-27 m 2 / g, 27-30 m 2 / g, etc.

[0118] In this way, the contact area between the active material and the electrolyte is increased, the wetting effect and the liquid retention capacity of the electrolyte are improved, and the polarization is reduced, which effectively improves the problem of lithium precipitation. It can also improve the ionic conductivity of the electrode material, thereby improving the overall conductivity of the electrode, improving the battery rate performance, and at the same time increasing the energy density of the battery.

[0119] In one embodiment, the present application provides a negative electrode plate, which includes a base layer and a first negative electrode active layer located on the base layer, wherein the first negative electrode active layer includes a middle region and an edge region.

[0120] Wherein, the negative electrode plate base layer may be a copper foil layer.

[0121] The porosity of the middle region of the first negative electrode active layer is ≥25%, and may be 25%-29%, for example, 25%, 26%, 27%, 28%, 29%, etc., or a range consisting of any two of the above values, for example, 25%-26%, 26%-27%, 27%-29%, etc.

[0122] The porosity of the edge region of the first negative electrode active layer is ≥20%, and may be 20%-24%, for example, 20%, 21%, 22%, 23%, 24%, etc., or a range consisting of any two of the above values, for example, 20%-22%, 22%-24%, etc.

[0123] The coating amount of the first negative electrode active layer in the middle area and the edge area is 0.05-0.09 g / 1540.25mm 2 For example, it can be 0.05 g / 1540.25 mm 2 , 0.06 g / 1540.25 mm 2 , 0.07 g / 1540.25 mm 2 , 0.08 g / 1540.25 mm 2 , 0.09g / 1540.25mm 2 etc.; or a range consisting of any two of the above values, for example, 0.05-0.06g / 1540.25mm 2 , 0.06-0.07 g / 1540.25mm 2 , 0.07-0.08g / 1540.25mm 2 , 0.08-0.09g / 1540.25mm 2 wait.

[0124] The thickness of the middle region and the edge region of the first negative electrode active layer is 25-60 μm. For example, it can be 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, etc. Or it can be a range consisting of any two of the above values, for example, 25-40 μm, 40-50 μm, 50-60 μm, etc.

[0125] The compaction density of the middle region of the first negative electrode active layer is 1.2-1.3 g / cm³. For example, it can be 1.20 g / cm³, 1.22 g / cm³, 1.24 g / cm³, 1.26 g / cm³, 1.28 g / cm³, 1.30 g / cm³, etc. Or it can be a range consisting of any two of the above values, for example, 1.20-1.22 g / cm³, 1.22-1.24 g / cm³, 1.24-1.26 g / cm³, 1.26-1.28 g / cm³, 1.28-1.30 g / cm³, etc.

[0126] The compaction density of the edge region of the first negative electrode active layer is 1.3-1.6 g / cm³. For example, it may be 1.30 g / cm³, 1.35 g / cm³, 1.40 g / cm³, 1.45 g / cm³, 1.50 g / cm³, 1.55 g / cm³, 1.60 g / cm³, etc. Or it may be a range consisting of any two of the above values, for example, 1.30-1.40 g / cm³, 1.40-1.50 g / cm³, 1.50-1.60 g / cm³, etc.

[0127] In one embodiment, the negative electrode plate further includes a second negative electrode active layer, and the second negative electrode active layer is located on a side of the first negative electrode active layer away from the base layer.

[0128] The porosity of the second negative electrode active layer is ≥25%, and may be 25%-29%, for example, 25%, 26%, 27%, 28%, 29%, etc., or a range consisting of any two of the above values, for example, 25%-26%, 26%-27%, 27%-29%, etc.

[0129] The coating amount of the second negative electrode active layer is 0.05-0.09 g / 1540.25 mm 2 For example, it can be 0.05 g / 1540.25 mm 2 , 0.06 g / 1540.25 mm 2 , 0.07 g / 1540.25 mm 2 , 0.08 g / 1540.25 mm 2 , 0.09 g / 1540.25 mm 2etc.; or a range consisting of any two of the above values, for example, 0.05-0.06g / 1540.25mm 2 , 0.06-0.07 g / 1540.25mm 2 , 0.07-0.08g / 1540.25mm 2 , 0.08-0.09g / 1540.25mm 2 wait.

[0130] The thickness of the second negative electrode active layer is 25-60 μm, for example, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, etc., or a range consisting of any two of the above values, for example, 25-40 μm, 40-50 μm, 50-60 μm, etc.

[0131] The compaction density of the second negative electrode active layer is 1.2-1.3 g / cm³. For example, it can be 1.20 g / cm³, 1.22 g / cm³, 1.24 g / cm³, 1.26 g / cm³, 1.28 g / cm³, 1.30 g / cm³, etc. Or it can be a range consisting of any two of the above values, for example, 1.20-1.22 g / cm³, 1.22-1.24 g / cm³, 1.24-1.26 g / cm³, 1.26-1.28 g / cm³, 1.28-1.30 g / cm³, etc.

[0132] By setting it in this way, the porosity of the negative electrode sheet can be increased and the liquid retention capacity can be improved; by setting the active material in the upper layer to account for a relatively high proportion, the amount of lithium that can be embedded in the negative electrode is increased.

[0133] In one embodiment, the edge region of the first negative electrode active layer includes the first negative electrode active material.

[0134] The first negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, and tin-based material. It can be a carbon-based negative electrode material, a silicon-based negative electrode material, a tin-based negative electrode material, a lithium titanate negative electrode material, a metal lithium negative electrode material, etc.; specifically including but not limited to graphite materials, silicon-carbon materials, graphite-silicon oxide materials, nano-silicon materials, silicon oxide materials and tin-based materials; more specifically including natural graphite, artificial graphite, mesophase microcarbon beads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, spinel-structured lithiated TiO2-Li4Ti5O 12 , one or more of Li-Al alloys.

[0135] Taking artificial graphite as an example, the particle size D of the first negative electrode active material isV 50 is 10-15 μm. For example, it can be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc. Or it can be a range consisting of any two of the above values, for example, 10-11 μm, 11-12 μm, 12-13 μm, 13-14 μm, 14-15 μm, etc.

[0136] Taking artificial graphite as an example, the specific surface area of ​​the first negative electrode active material is 1.0-2.5 m 2 / g. For example, it can be 1.0m 2 / g, 1.3 m 2 / g, 1.6 m 2 / g, 1.9 m 2 / g, 2.1 m 2 / g, 2.3 m 2 / g, 2.5 m 2 / g, etc. Or a range consisting of any two of the above values, for example, 1.0-1.3 m 2 / g, 1.3-1.6 m 2 / g, 1.6-1.9 m 2 / g, 1.9-2.1 m 2 / g, 2.1-2.3m 2 / g, 2.3-2.5 m 2 / g, etc.

[0137] In one embodiment, the second negative electrode active layer includes a second negative electrode active material.

[0138] The second negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, and tin-based material. It can be a carbon-based negative electrode material, a silicon-based negative electrode material, a tin-based negative electrode material, a lithium titanate negative electrode material, a metal lithium negative electrode material, etc.; specifically including but not limited to graphite materials, silicon-carbon materials, graphite-silicon oxide materials, nano-silicon materials, silicon oxide materials and tin-based materials; more specifically including natural graphite, artificial graphite, mesophase microcarbon beads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, spinel structured lithiated TiO2-Li4Ti5O 12 , one or more of Li-Al alloys.

[0139] The material of the second negative electrode active material may be the same as or different from the material of the first negative electrode active material.

[0140] Taking artificial graphite as an example, the particle size D of the second negative electrode active material is V50 is 5-10 μm. For example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. Or it can be a range consisting of any two of the above values, for example, 5-6 μm, 6-7 μm, 7-8 μm, 8-9 μm, 9-10 μm, etc.

[0141] Taking artificial graphite as an example, the specific surface area of ​​the second negative electrode active material is 2.0-4.0 m 2 / g. For example, it can be 2.0m 2 / g, 2.3 m 2 / g, 2.6 m 2 / g, 2.9 m 2 / g, 3.1 m 2 / g, 3.3 m 2 / g, 3.5 m 2 / g, 3.7 m 2 / g, 4.0 m 2 / g, etc. Or a range consisting of any two of the above values, for example, 2.0-2.3 m 2 / g, 2.3-2.6 m 2 / g, 2.6-2.9 m 2 / g, 2.9-3.1 m 2 / g, 3.1-3.3 m 2 / g, 3.3-3.5 m 2 / g, 3.5-3.7 m 2 / g, 3.7-4.0 m 2 / g, etc.

[0142] In this way, the contact area between the active material and the electrolyte can be increased, the wetting effect and liquid retention capacity of the electrolyte can be improved, thereby reducing polarization and effectively improving the problem of lithium precipitation. It can also improve the ionic conductivity of the electrode material, thereby improving the overall conductivity of the electrode, improving the battery rate performance, and at the same time increasing the energy density of the battery.

[0143] The present application also provides a method for preparing an electrode plate, which specifically includes: providing a base layer, a first electrode slurry and a second electrode slurry; wherein the base layer includes a middle area and an edge area, and the edge area surrounds the middle area; the mass proportion of the active material in the first electrode slurry is less than the mass proportion of the active material in the second electrode slurry; using the first electrode slurry to form an active layer in the edge area, and using the second electrode slurry to form an active layer in the middle area.

[0144] In one embodiment, the preparation method includes: forming a first active layer in the edge region using a first electrode slurry, forming a first active layer in the middle region using a second electrode slurry, and forming a second active layer on the first active layer using a second electrode slurry.

[0145] In one embodiment, the mass content of the active material in the first electrode slurry is 94%-96%, for example, it can be 94%, 95%, 96%, etc.

[0146] In one embodiment, the mass content of the active material in the second electrode slurry is 95%-97%; for example, it can be 95%, 96%, 97%, etc.

[0147] In one embodiment, the first electrode slurry and the second electrode slurry further include a binder, a conductive agent and other optional additives. As an example, the conductive agent can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene and carbon nanofibers. As an example, the binder can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB). As an example, other optional additives can be thickeners and dispersants (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials.

[0148] In one embodiment, the first active layer and the second active layer can be formed by coating separately. Specifically, the first electrode slurry is firstly coated on the base layer in different areas, and the middle area is thinned to no slurry out through the gasket control, so as to form the first active layer in the edge area, and the middle area is left empty; then the second electrode slurry is coated on the upper layer of the first electrode slurry, and the two ends are controlled by the gasket to have less slurry outflow and more slurry outflow in the middle, so as to form the middle area of ​​the first active layer and the second active layer at the same time. Drying is performed to obtain the electrode sheet.

[0149] In one embodiment, the coating of the upper and lower layers can be performed simultaneously. Specifically, the lower gasket is thinned in the middle and the two sides are kept unchanged, so that the first electrode slurry is distributed in the edge area to form the edge area of ​​the first active layer; the upper gasket is thinned on both sides and the middle is kept unchanged, so that the second electrode slurry has a large amount in the middle area and a small amount in the edge area, so as to form the middle area of ​​the first active layer and the second active layer at the same time. Drying is performed to obtain the electrode sheet.

[0150] The present application also provides an electrochemical device, which includes any device that generates an electrochemical reaction, and its specific examples include all kinds of primary batteries or secondary batteries. For example, it can be different types of secondary batteries such as lithium batteries, sodium batteries, potassium batteries, etc. Lithium secondary batteries may include lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium ion polymer secondary batteries.

[0151] Please refer to Figure 5 , Figure 5 1 is a schematic diagram of the exploded structure of a battery according to one or more embodiments. The battery 100 includes a box body 10 and a battery cell 20, and the battery cell 20 is accommodated in the box body 10. Among them, the box body 10 is used to provide a storage space for the battery cell 20, and the box body 10 can adopt a variety of structures. In some embodiments, the box body 10 may include a first part 11 and a second part 12, and the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 may be a hollow structure with one end open, and the first part 11 may be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box body 10 formed by the first part 11 and the second part 12 may be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0152] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0153] Each battery cell 20 may be a secondary battery or a primary battery; may be a lithium-sulfur battery, a sodium-ion battery or a magnesium-ion battery, but is not limited thereto.

[0154] The battery cell 20 may be the aforementioned cylindrical battery.

[0155] The cylindrical battery cell 20 includes an electrode assembly and an electrolyte, and the electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode sheet can be the positive electrode sheet of any of the above-mentioned embodiments, and the specific structure can be found in the above text, which will not be repeated here; the negative electrode sheet can be the negative electrode sheet of any of the above-mentioned embodiments, and the specific structure can be found in the above text, which will not be repeated here.

[0156] In one embodiment, the electrolyte includes one or more of carbonate solvents and ether solvents.

[0157] The carbonate is usually a small molecule cyclic or chain carbonate; including but not limited to one or more of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and fluorocarbonate; it can also be at least one ester solvent selected from γ-butyrolactone, dimethyl sulfite, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, methyl propionate, ethyl propionate, propyl acetate, and fluorocarboxylic acid esters.

[0158] Ether solvents include, but are not limited to, one or more of dimethyl ether, diethyl ether, tetrahydrofuran, methyltetrahydrofuran, ethylene oxide, 1,3-dioxolane, fluoroether, DME (ethylene glycol dimethyl ether), DEE (ethylene glycol diethyl ether), DEGDME (diethylene glycol dimethyl ether), TRGDME (triethylene glycol dimethyl ether), TEGDME (tetraethylene glycol dimethyl ether), dipropyl ether and dibutyl ether.

[0159] In other embodiments, the electrolyte may also include any one or a mixture of several of an amine solvent, a sulfone solvent, and a nitrile solvent. Amine solvents include at least one of N-methylacetamide, N-methylformamide, dimethylformamide, and diethylformamide. Sulfone solvents include at least one of dimethyl sulfoxide, cyclopentane sulfone, diphenyl sulfoxide, thionyl chloride, and dipropyl sulfone. Nitrile solvents include at least one of acetonitrile, succinonitrile, adiponitrile, and glutaronitrile. The electrolyte is preferably a high-voltage resistant electrolyte, which has a weakened acidity under high voltage, can facilitate the transmission of active ions, significantly reduce side reactions on the electrode surface, and improve battery stability.

[0160] In some embodiments, the electrolyte further includes an electrolyte salt, which can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate and lithium tetrafluorooxalatophosphate.

[0161] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0162] In some embodiments, the purpose of the electrochemical device of the present application is not particularly limited, and it can be used for any electronic device known in the prior art. The battery disclosed in the embodiment of the present application can be used for various energy storage systems using batteries as power supplies or using batteries as energy storage elements. That is, a kind of electric device is provided. In some embodiments, the electric device of the present application can be used for, but not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, ships, spacecraft, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large-scale household batteries and lithium-ion capacitors, etc.

[0163] Electrical equipment can choose battery cells, battery modules or battery packs according to its usage requirements.

[0164] Please refer to Figure 6 , Figure 6 : is a schematic diagram of the structure of a vehicle according to one or more embodiments. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, the head or the tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for the starting, navigation and working power requirements of the vehicle 1000 during driving.

[0165] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0166] The beneficial effects of the present application are further illustrated below with reference to the embodiments.

[0167] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0168] Example 1 1. Preparation of negative electrode sheet Artificial graphite, Sup-P and polyacrylic acid are mixed in deionized water in different proportions to obtain a first negative electrode slurry and a second negative electrode slurry, wherein the mass proportion of graphite in the first negative electrode slurry is 96%, and the mass proportion of graphite in the second negative electrode slurry is 97%; The first negative electrode slurry is coated on a Cu substrate, and during the coating process, a gasket is used to control the thinning of the middle area until no slurry flows out, so as to obtain a first electrode slurry layer located in the edge area; then the second negative electrode slurry is coated, and during the coating, the gasket is used to control the slurry outflow at both ends to be less, and the slurry outflow in the middle is more, so as to form the second negative electrode slurry layer on the substrate in the vacated middle area and on the first negative electrode slurry layer at the same time, and after drying, a first negative electrode active layer having different performance parameters in the edge area and the middle area, and a second negative electrode active layer formed integrally with the middle area of ​​the first negative electrode active layer are obtained, so as to obtain a negative electrode sheet.

[0169] 2. Preparation of positive electrode Lithium iron phosphate, conductive agent Super P, and binder PVDF are respectively mixed in different proportions in an appropriate amount of NMP to obtain a first positive electrode slurry and a second positive electrode slurry, wherein the mass proportion of lithium iron phosphate in the first positive electrode slurry is 96%, and the mass proportion of lithium iron phosphate in the second positive electrode slurry is 97%; The first positive electrode slurry is coated on the aluminum foil, and during the coating process, the middle area is thinned by a gasket to control the thinning until no slurry flows out, so as to obtain a first positive electrode slurry layer located in the edge area; then the second positive electrode slurry is coated, and during the coating, the gaskets are used to control the slurry outflow at both ends to be less and the slurry outflow in the middle to be more, so as to form the second positive electrode slurry layer on the substrate in the vacated middle area and on the first positive electrode slurry layer at the same time, and after drying, a first positive electrode active layer with different performance parameters in the edge area and the middle area and a second positive electrode active layer are obtained to obtain a positive electrode sheet.

[0170] 3. Isolation film Use PP / PE composite isolation film.

[0171] 4. Electrolyte Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte. In the electrolyte, the concentration of LiPF6 is 1 mol / L.

[0172] 5. Battery assembly The negative electrode plate and the positive electrode plate, the separator, the mechanical parts, etc. obtained above are assembled into a lithium-ion battery dry cell, and the electrolyte is injected and the lithium-ion battery is obtained after formation.

[0173] Embodiment 2-10 Compared with Example 1, the proportion of active materials, porosity, compaction density, active material particle size, specific surface area, etc. are adjusted in Examples 2-10, as shown in Table 1 for details.

[0174] Comparative Example 1 Compared with Example 1, the active material proportion, porosity, compaction density, active material particle size, specific surface area, etc. in each region of the active layer in Comparative Example 1 are uniformly distributed.

[0175] 1. Preparation of negative electrode sheet Artificial graphite, Sup-P and polyacrylic acid are mixed in deionized water in proportion to obtain a negative electrode slurry, in which the mass proportion of graphite in the negative electrode slurry is 94%; the negative electrode slurry is coated on a Cu substrate, and after drying, a negative electrode active layer is obtained to obtain a negative electrode sheet.

[0176] 2. Preparation of positive electrode Lithium iron phosphate, conductive agent Super P, and binder PVDF are fully stirred and mixed in a proper amount of NMP in proportion to obtain a positive electrode slurry, in which the mass proportion of lithium iron phosphate in the positive electrode slurry is 94%; the positive electrode slurry is coated on aluminum foil, and after drying, a positive electrode active layer is obtained to obtain a positive electrode sheet.

[0177] Battery related parameter test (1) Cycle life At 25°C, charge the battery to 3.65V at 1C, leave it for 1 h, and discharge it to 2.5V at 1C. Then charge it again and repeat the cycle, recording the number of cycles when the battery capacity decays to 80% of the initial capacity.

[0178] (2) Full charge interface The battery that was cycled to 80% SOH at 25°C was fully charged and then disassembled to observe the fully charged interface.

[0179] (3) Battery DC resistance DCR First, discharge to 2.5V at 0.33C rate at 25℃, and charge to 4.3V at 0.33C after 30 minutes, and then keep constant voltage at 4.3V until the current is less than 0.05C; after 30 minutes, discharge to 2.5V at 0.33C to get the battery capacity C0. Then charge the battery to 4.3V at 0.33C, and keep constant voltage at 4.3V until the current is less than 0.05C, and after 30 minutes, discharge the battery to 50% SOC at 0.5C0 capacity at 0.33C, and then discharge at 4C for 30s, and the battery voltage is V2. According to (V1-V2) / 4C*1000, the battery DCR (in mΩ) is obtained.

[0180] Table 1: Condition parameters and performance parameters of each embodiment and comparative example It can be seen from the data in Table 1 that the parameter settings of each area in the active layer of the electrode of Comparative Example 1 are uniform. Relative to Comparative Example 1, the batteries of each embodiment in which the mass proportion of the active material in the middle area is set to be greater than the mass proportion of the active material in the edge area can increase the ion deintercalation amount in the middle area of ​​the active layer, reduce polarization, and increase the cycle life of the cylindrical battery.

[0181] From Examples 1 to 5, by setting the mass proportion of active materials in the middle area of ​​the negative electrode plate to be higher than the mass proportion of active materials in the edge area, the kinetic performance of the battery can be improved, the amount of lithium that can be embedded in the anode is increased, and the internal resistance is reduced. At the same time, the amount of active ions increases, which can extend the cycle life.

[0182] From Examples 1, 6-8, by setting a high porosity in the middle area of ​​the negative electrode sheet, the liquid retention capacity can be improved; by increasing the porosity in the middle area of ​​the positive electrode sheet, the liquid retention capacity is improved; and by setting a high porosity in the middle area of ​​the positive electrode sheet and the negative electrode sheet at the same time, the unevenness of the electrode sheets after long cycles can be improved.

[0183] From Examples 1, 9-10, it can be seen that by selecting active materials with small particle size and large specific surface area, the contact with the electrolyte can be increased, the kinetics can be improved, and the polarization can be reduced. At the same time, the porosity of the material itself can be increased, the liquid retention capacity can be improved, and the cycle life can be extended.

[0184] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An electrode sheet, characterized in that: include: Grassroots; A first active layer, comprising an active material, is disposed on the substrate; The first active layer includes a middle region and an edge region, wherein the edge region surrounds the middle region, and based on the same unit area, a mass proportion of active material in the middle region is greater than a mass proportion of active material in the edge region.

2. The electrode sheet according to claim 1, characterized in that: The porosity of the middle region is greater than the porosity of the edge region; and / or The compaction density of the middle region is less than the compaction density of the edge region.

3. The electrode sheet according to claim 1 or 2, characterized in that: The electrode sheet also includes a second active layer, which is located on a side of the first active layer away from the base layer; based on the same unit area, the mass proportion of the active material in the second active layer is greater than the mass proportion of the active material in the edge area.

4. The electrode sheet according to claim 3, characterized in that: The porosity of the second active layer is greater than the porosity of the edge region; and / or The compaction density of the second active layer is less than the compaction density of the edge region.

5. The electrode sheet according to claim 3 or 4, characterized in that: The middle region is formed by extending the second active layer.

6. The electrode sheet according to any one of claims 3 to 5, characterized in that: The mass content of active material in the edge region is 94%-96%; and / or The mass content of the active material in the second active layer is 95%-97%.

7. The electrode sheet according to any one of claims 3 to 6, characterized in that: The ratio of the porosity of the second active layer to the porosity of the edge region is 2:1-1:1; and / or The ratio of the compaction density of the second active layer to the compaction density of the edge region is 1:1-1:1.

5.

8. The electrode sheet according to any one of claims 3 to 7, characterized in that: The edge region of the first active layer includes a first active material, and the second active layer includes a second active material, wherein: The particle size of the second active material is smaller than the particle size of the first active material; and / or The specific surface area of ​​the second active material is greater than the specific surface area of ​​the first active material.

9. The electrode sheet according to any one of claims 1 to 6, characterized in that: The ratio of the particle size of the second active material to the particle size of the first active material is 1:1-1:7; and / or The ratio of the specific surface area of ​​the second active material to the specific surface area of ​​the first active material is 3:1-1:

1.

10. The electrode sheet according to any one of claims 1 to 9, characterized in that: In the width direction, the length of the middle area is L1, the total length of the edge area is L2, 0<L1 / L2<0.6; and / or In the height direction, the length of the middle area is L3, the total length of the edge area is L4, and 0<L3 / L4<0.

5.

11. The electrode sheet according to any one of claims 1 to 10, characterized in that: The electrode sheet is a positive electrode sheet, and the positive electrode sheet includes a base layer and a first positive electrode active layer located on the base layer, and the first positive electrode active layer includes a middle area and an edge area, wherein: The porosity of the middle region of the first positive electrode active layer is ≥15%, and can be 15%-20%; and / or The porosity of the edge region of the first positive electrode active layer is ≥10%, and can be 10%-15%; and / or The coating amount of the middle area and the edge area of ​​the first positive electrode active layer is 0.1-0.2 g / 1540.25 mm 2 ; and / or The thickness of the middle region and the edge region of the first positive electrode active layer is 30-60 μm; and / or The compaction density of the middle region of the first positive electrode active layer is 2.0-2.2 g / cm³; and / or The compaction density of the edge region of the first positive electrode active layer is 2.2-2.5 g / cm³.

12. The electrode sheet according to claim 11, characterized in that: The edge region of the first positive electrode active layer includes a first positive electrode active material, wherein: The particle size D of the first positive electrode active material V 50 is 1000-2000 nm; and / or The specific surface area of ​​the first positive electrode active material is 10-15 m 2 / g; The first positive electrode active material includes one or more of lithium iron phosphate, nano lithium iron phosphate, lithium iron manganese phosphate, lithium manganese oxide, lithium cobalt oxide, ternary materials, and lithium-rich manganese-based materials.

13. The electrode sheet according to claim 11 or 12, characterized in that: The positive electrode plate further includes a second positive electrode active layer, and the second positive electrode active layer is located on a side of the first positive electrode active layer away from the base layer, wherein: The porosity of the second positive electrode active layer is ≥15%, and may be 15%-20%; and / or The coating amount of the second positive electrode active layer is 0.1-0.2 g / 1540.25 mm 2 ; and / or The thickness of the second positive electrode active layer is 30-60 μm; and / or The compaction density of the second positive electrode active layer is in the range of 2.0-2.2 g / cm³.

14. The electrode sheet according to claim 13, characterized in that: The second positive electrode active layer includes a second positive electrode active material, wherein: The particle size D of the second positive electrode active material V 50 is 300-900 nm; and / or The specific surface area of ​​the second positive electrode active material is 19-30 m 2 / g; The second positive electrode active material includes one or more of lithium iron phosphate, nano lithium iron phosphate, lithium iron manganese phosphate, lithium manganese oxide, lithium cobalt oxide, ternary materials, and lithium-rich manganese-based materials.

15. The electrode sheet according to any one of claims 1 to 10, characterized in that: The electrode sheet is a negative electrode sheet, and the negative electrode sheet includes a base layer and a first negative electrode active layer located on the base layer, and the first negative electrode active layer includes a middle area and an edge area, wherein: The porosity of the middle region of the first negative electrode active layer is ≥25%, and can be 25%-29%; and / or The porosity of the edge region of the first negative electrode active layer is ≥20%, and can be 20%-24%; and / or The coating amount of the middle area and the edge area of ​​the first negative electrode active layer is 0.05-0.09 g / 1540.25 mm 2 ; and / or The thickness of the middle region and the edge region of the first negative electrode active layer is 25-60 μm; and / or The compaction density of the middle region of the first negative electrode active layer is 1.2-1.3 g / cm³; and / or The compaction density of the edge region of the first negative electrode active layer is 1.3-1.6 g / cm³.

16. The electrode sheet according to claim 15, characterized in that: The edge region of the first negative electrode active layer includes a first negative electrode active material, wherein: The particle size D of the first negative electrode active material V 50 is 10-15 μm; and / or The specific surface area of ​​the first negative electrode active material is 1.0-2.5 m 2 / g; The first negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, and tin-based material.

17. The electrode sheet according to claim 15 or 16, characterized in that: The negative electrode plate further includes a second negative electrode active layer, which is located on a side of the first negative electrode active layer away from the base layer, wherein: The porosity of the second negative electrode active layer is ≥25%, and can be 25%-29%; and / or The coating amount of the second negative electrode active layer is 0.05-0.09 g / 1540.25 mm 2 ; and / or The thickness of the second negative electrode active layer is 25-60 μm; and / or The compaction density of the second negative electrode active layer is in the range of 1.2-1.3 g / cm³.

18. The electrode sheet according to claim 17, characterized in that: The second negative electrode active layer includes a second negative electrode active material, wherein: The particle size D of the second negative electrode active material V 50 is 5-10 μm; and / or The specific surface area of ​​the second negative electrode active material is 2.0-4.0 m 2 / g; The second negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, and tin-based material.

19. A method for preparing an electrode sheet, characterized in that: include: Providing a base layer, a first electrode paste and a second electrode paste; the base layer comprises a middle region and an edge region, and the edge region surrounds the middle region; The mass proportion of the active material in the first electrode slurry is less than the mass proportion of the active material in the second electrode slurry; The first electrode slurry is used to form an active layer in the edge region, and the second electrode slurry is used to form an active layer in the middle region.

20. The method for preparing an electrode sheet according to claim 19, characterized in that: The mass content of active material in the first electrode slurry is 94%-96%; and / or The mass content of active material in the second electrode slurry is 95%-97%.

21. A battery, characterized in that: The invention comprises an electrode sheet as described in any one of claims 1 to 18, or an electrode sheet prepared by the method for preparing an electrode sheet as described in claim 19 or 20.

22. An electrical equipment, characterized in that: Comprising the battery of claim 21.

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