WO2024077475A1

WO2024077475A1 - Electrode sheet and preparation method therefor, and secondary battery and electric apparatus

Info

Publication number: WO2024077475A1
Application number: PCT/CN2022/124596
Authority: WO
Inventors: 黄思应; 孙成栋; 刘义修; 王耀辉
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2022-10-11
Filing date: 2022-10-11
Publication date: 2024-04-18

Abstract

Provided in the present application are an electrode sheet and a preparation method therefor, and a secondary battery and an electric apparatus. The electrode sheet comprises a carbon material layer (100) and an active layer (200), wherein the carbon material layer (100) has pores, the active layer (200) is located on at least one surface of the carbon material layer (100), and the active layer (200) includes an active material, part of the active material permeating into the pores.

Description

Electrode sheet and preparation method thereof, secondary battery and electric device

Technical Field

The present application relates to the field of secondary batteries, and in particular to an electrode plate and a preparation method thereof, a secondary battery and an electrical device.

Background technique

With the advancement of battery technology, the energy density of secondary batteries continues to increase, and their scope of use is also expanding. In secondary batteries, the electrode plate has an important influence on the performance of the battery. Traditional electrode plates are usually made by coating active materials on the surface of metal foil. The electrode plate has a high energy density, which enables the battery to better meet the energy density requirements, but the tensile strength of the plate is low, and the risk of the plate breaking during the production process is high.

Summary of the invention

Based on the above problems, the present application provides an electrode plate and a preparation method thereof, a secondary battery and an electric device. By designing the structure of the electrode plate, the tensile strength of the electrode plate is effectively improved.

In order to achieve the above-mentioned objectives, the first aspect of the present application provides an electrode plate, comprising a carbon material layer and an active layer, wherein the carbon material layer has pores, the active layer is located on at least one surface of the carbon material layer, the active layer contains active material, and part of the active material penetrates into the pores.

In the electrode plate provided in the present application, by compounding the active layer and the carbon material layer, and partially infiltrating the active material into the pores of the carbon material layer, the electrode plate can exhibit better tensile strength. At the same time, the conductive performance of the electrode plate can be maintained, the internal resistance of the battery can be reduced, and the energy density of the battery can be increased.

In some embodiments, the active layers and the carbon material layers are alternately stacked; the number of active layers is equal to the number of carbon material layers, or the active layers have one more layer than the carbon material layers.

In some embodiments, the number of carbon material layers is ≥2.

In some embodiments, the carbon material layer has a thickness of 1 μm to 20 μm.

In some embodiments, the carbon content of the carbon material layer is 90.00-99.99%.

In some embodiments, the porosity of the carbon material layer is 13% to 91%.

In some embodiments, the carbon material layer includes carbon fibers, and the carbon fibers are interwoven to form the pores.

In some embodiments, the diameter of the carbon fiber is 1 μm to 20 μm.

In some embodiments, the length of the carbon fiber is ≥50 mm.

In some of the embodiments, in a projection of the carbon material layer onto a plane perpendicular to the thickness direction of the carbon material layer, a distance between adjacent carbon fibers is 0 to 100 μm.

In some embodiments, the distribution of the carbon fibers includes one or more of a determinant distribution, a unidirectional distribution, and a disordered distribution.

In some embodiments, the angle formed between the rows and columns in the determinant distribution is 45° to 90°.

In some embodiments, the carbon fiber includes one or more of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber, viscose-based carbon fiber and vapor-grown carbon fiber.

In some of the embodiments, the carbon material layer further includes a binder, and the binder is used to bond adjacent carbon fibers.

In some embodiments, the adhesive includes one or more of polyvinylidene fluoride, polyimide, polyamide-imide, styrene-butadiene rubber, nitrile rubber, epoxy modified products thereof, and acrylate modified products thereof.

In some embodiments, the carbon material layer further includes a conductive agent, and the conductive agent is located in the pores of the carbon material layer.

In some embodiments, the mass ratio of the conductive agent to the binder is (0.1-4): (0.1-3).

In some embodiments, the conductive agent includes one or more of superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In a second aspect, the present application also provides a method for preparing the electrode plate of the first aspect, comprising: disposing the active layer on at least one surface of the carbon material layer, and allowing part of the active material of the active layer to penetrate into the pores of the carbon material layer.

In some embodiments, disposing the active layer on at least one surface of the carbon material layer includes: alternately stacking the active layer and the carbon material layer so that the number of layers of the active layer is equal to the number of layers of the carbon material layer, or the active layer has one more layer than the carbon material layer.

In some of the embodiments, the active slurry is transferred to the corresponding surface of the carbon material layer to form the active layer, wherein a portion of the active material in the active slurry penetrates into the pores of the carbon material layer.

In some of the embodiments, before disposing the active layer on at least one surface of the carbon material layer, the step of filling a conductive agent in the pores of the carbon material layer is also included.

In some embodiments, filling the pores of the carbon material layer with a conductive agent includes: transferring a modified slurry containing the conductive agent to the carbon material layer.

In some of the embodiments, the mass ratio of the solvent in the modified slurry to the conductive agent is (65-99): (0.5-20).

In some embodiments, the carbon material layer includes carbon fibers, the carbon fibers are interwoven to form the pores, and the modified slurry further includes a binder.

In a third aspect, the present application further provides a secondary battery, comprising the electrode plate of the second aspect.

In a fourth aspect, the present application further provides an electrical device, comprising the secondary battery of the third aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

FIG. 1 is a schematic diagram of an electrode plate according to an embodiment of the present application.

FIG. 2 is a schematic diagram of an electrode plate according to another embodiment of the present application.

FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.

FIG. 4 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 3 .

FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.

FIG. 6 is a schematic diagram of a battery pack according to an embodiment of the present application.

FIG. 7 is an exploded view of the battery pack shown in FIG. 6 according to an embodiment of the present application.

FIG. 8 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

Description of reference numerals:

100. Carbon material layer; 200. Active layer; 1. Battery pack; 2. Upper case; 3. Lower case; 4. Battery module; 5. Secondary battery; 51. Shell; 52. Electrode assembly; 53. Cover plate; 6. Electrical device.

In order to better describe and illustrate the embodiments and/or examples of the inventions disclosed herein, reference may be made to one or more drawings. The additional details or examples used to describe the drawings should not be considered to limit the scope of the disclosed inventions, the embodiments and/or examples currently described, and any of the best modes of these inventions currently understood.

Detailed ways

In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and/or" used herein includes any and all combinations of one or more related listed items.

The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the

minimum range values

1 and 2 are listed, and if the

maximum range values

3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed in this article, and "0 to 5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means 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.

If there is no special explanation, the "include" and "comprising" mentioned in this application represent open or closed forms. For example, the "include" and "comprising" may mean that other components not listed may also be included or included, or may only include or include the listed components.

If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

Referring to FIG1 , the present application provides an electrode plate, which includes a carbon material layer 100 and an active layer 200 , wherein the carbon material layer 100 has pores, the active layer 200 is located on at least one surface of the carbon material layer 100 , and the active layer 100 contains active materials, and part of the active materials penetrate into the pores.

It should be noted that in the electrode plate shown in FIG. 1 , the positional relationship between the carbon material layer 100 and the active layer 200 is mainly shown, wherein the pores of the carbon material layer 100 are not shown, and the active material infiltrated into the pores of the carbon material layer 100 is not shown.

In the electrode plate provided in the present application, the active layer 200 and the carbon material layer 100 are compounded, and part of the active material penetrates into the pores of the carbon material layer 100, so that the electrode plate can exhibit better tensile strength. At the same time, the conductive performance of the electrode plate can be maintained, the internal resistance of the battery can be reduced, and the energy density of the battery can be improved.

It is understood that the electrode plate in the present application can be a positive electrode plate or a negative electrode plate. When the active material is a positive electrode active material, a positive electrode active layer can be obtained, and then a positive electrode plate can be obtained. When the active material is a negative electrode active material, a negative electrode active layer can be obtained, and then a negative electrode plate can be obtained.

In some embodiments, the active layers and the carbon material layers are alternately stacked; the number of active layers is equal to the number of carbon material layers, or the number of active layers is one more than the number of carbon material layers.

It is understood that the active layer and the carbon material layer are alternately stacked, indicating that two adjacent layers are different. In this case, the stacking relationship between the active layer and the carbon material layer can be expressed as active layer-carbon material layer, active layer-carbon material layer-active layer, active layer-carbon material layer-active layer-carbon material layer, carbon material layer-active layer, carbon material layer-active layer-carbon material layer-active layer, etc.

It is understandable that the number of layers of the active layer is equal to the number of layers of the carbon material layer, which can be represented as the structure shown in Figure 1, wherein the number of layers of the active layer and the carbon material layer is equal and both are 1 layer. Of course, the active layer and the carbon material layer can also be other numbers of layers. For example, the number of layers of the active layer and the carbon material layer is equal and both are 2 layers, the number of layers of the active layer and the carbon material layer is equal and both are 3 layers, the number of layers of the active layer and the carbon material layer is equal and both are 4 layers, the number of layers of the active layer and the carbon material layer is equal and both are 5 layers, the number of layers of the active layer and the carbon material layer is equal and both are 6 layers, etc.

It can also be understood that the active layer has one more layer than the carbon material layer, which can be represented by the structure shown in FIG2 , wherein the number of layers of the active layer 200 is 3, and the number of layers of the carbon material layer 100 is 2. Of course, the active layer and the carbon material layer can also have other numbers of layers. For example, the number of layers of the active layer is 2, and the number of layers of the carbon material layer is 1. The number of layers of the active layer is 4, and the number of layers of the carbon material layer is 3. The number of layers of the active layer is 5, and the number of layers of the carbon material layer is 4. The number of layers of the active layer is 6, and the number of layers of the carbon material layer is 5. It can also be understood that the active layer has one more layer than the carbon material layer, and on the basis of the alternating stacking of the active layer and the carbon material layer, in the stacking structure formed by the active layer and the carbon material layer, the outermost layer is the active layer.

In some embodiments, the number of carbon material layers is ≥ 2. In this case, the carbon material layer can provide relatively stable support for the electrode plate, thereby improving the performance stability of the electrode plate.

In some embodiments, the thickness of the carbon material layer is 1 μm to 20 μm. With the continuous deepening of battery development, the thinning of the electrode plate is one of the main trends. By thinning the electrode plate, on the one hand, the volume and weight of the battery can be reduced. On the other hand, by thinning the current collector in the electrode plate, the amount of active material used can be increased on the basis of the unchanged volume and weight of the electrode plate, thereby increasing the energy density of the battery. In these embodiments, by selecting a carbon material layer with a smaller thickness, a basis is provided for the thinning of the electrode plate, so that the electrode plate can have a smaller thickness while maintaining good tensile strength, which is conducive to improving the energy density of the battery. Optionally, the thickness of the carbon material layer can be but is not limited to 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm, etc. It is understandable that the thickness of the carbon material layer may be selected in the range of 1 μm to 20 μm.

In some embodiments, the carbon content of the carbon material layer is 90.00% to 99.99%. The carbon content of the carbon material layer has good conductivity and strength when it is in the range of 90.00% to 99.99%, which is beneficial to further improve the conductivity and tensile strength of the electrode plate. Optionally, the carbon content of the carbon material layer can be but is not limited to 90.00%, 91.00%, 92.00%, 93.00%, 94.00%, 95.00%, 96.00%, 97.00%, 98.00%, 99.00%, 99.90% or 99.99%, etc. It can be understood that the carbon content of the carbon material layer can also be other suitable selections within the range of 90.00% to 99.99%.

As a method for obtaining a carbon material layer with a carbon content of 90.00% to 99.99%, the carbon material layer can be treated by high-temperature graphitization to increase the carbon content of the carbon material layer. Optionally, the temperature of high-temperature graphitization is ≥2000°C. Further optionally, the temperature of high-temperature graphitization is ≥3000°C. Specifically, the temperature of high-temperature graphitization can be 2000°C, 2200°C, 2500°C, 2600°C, 2700°C, 2800°C, 2900°C, 3000°C, 3100°C, 3200°C, 3300°C, 3400°C, 3500°C, etc.

In some embodiments, the porosity of the carbon material layer is 13% to 91%. Optionally, the porosity of the carbon material layer can be, but is not limited to, 13%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, etc. It is understandable that the porosity of the carbon material layer can also be other suitable selections within the range of 13% to 91%.

In some embodiments, the thickness of the active layer is 5 μm to 100 μm. For example, the thickness of the active layer is 5 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, etc. It is understood that the thickness of the active layer can be determined based on the total thickness of the electrode sheet, the thickness and number of carbon material layers, and the number of active layer layers.

In some embodiments, the sum of the thickness of all active layers and all carbon material layers is 130 μm to 200 μm. Optionally, the sum of the thickness of all active layers and the carbon material layers may be, but is not limited to, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, etc. Of course, the sum of the thickness of all active layers and all carbon material layers may also be selected according to the actual design thickness of the electrode sheet.

In some embodiments, the carbon material layer includes carbon fibers, and the carbon fibers are interwoven to form pores. By interweaving carbon fibers to form pores, it is more convenient to obtain a carbon material layer of corresponding porosity, and it is also possible to reduce the weight of the carbon material layer, providing a basis for lightweight electrode plates and batteries. In addition, during the battery assembly process, it may be necessary to use steel nails and other fixings to perforate and fix multiple electrode plates. At this time, pores are formed by interweaving carbon fibers, and the fixings can pass through the fibers, which can reduce the risk of thermal runaway of the battery and improve the safety of battery use.

As some selected examples of carbon fiber, the diameter of the carbon fiber is 1μm to 20μm. Optionally, the diameter of the carbon fiber can be but is not limited to 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc. It is understandable that the diameter of the carbon fiber can also be other suitable choices within the range of 1μm to 20μm. The length of the carbon fiber is 5mm to 80mm, for example, 5mm, 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, etc. The length of the carbon fiber can also be other suitable choices within the range of 5mm to 80mm.

In some embodiments, in the projection of the carbon material layer on a plane perpendicular to its thickness direction, the distance between adjacent carbon fibers is 0 to 100 μm. It is understood that the projection of the carbon material layer on a plane perpendicular to its thickness direction represents the morphology of the carbon material layer in a plane perpendicular to its thickness direction, wherein the distance between adjacent carbon fibers is 0 to 100 μm. For example, the distance between adjacent carbon fibers can be 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc. It is also understood that when the distance between adjacent carbon fibers is 0, it means that the carbon fibers intersect, or that the carbon fibers block each other in the thickness direction of the carbon material layer.

As some examples of carbon fiber distribution, the distribution of carbon fibers includes one or more of a determinant distribution, a unidirectional distribution, and a disordered distribution. It is understood that a determinant distribution means that the carbon fibers are distributed in the form of rows and columns, with a certain angle formed between the rows and columns. A unidirectional distribution means that there is a large amount of carbon fibers in one direction (usually the warp direction) and a small amount of carbon fibers in another direction. Optionally, in a unidirectional distribution, the diameter of the carbon fibers in the direction where a large amount of carbon fibers are distributed is greater than the diameter of the carbon fibers in the direction where a small amount of carbon fibers are distributed. A disordered distribution means that there is no obvious distribution pattern between the carbon fibers as a whole.

Optionally, the angle formed between the row and the column in the determinant distribution is 45° to 90°. For example, the angle formed between the row and the column in the determinant is 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85° or 90°, etc. It is understandable that the angle formed between the row and the column in the determinant distribution can also be other suitable selections within the range of 45° to 90°.

In some embodiments, as material examples of carbon fibers, the carbon fibers include one or more of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, viscose-based carbon fibers, and vapor-grown carbon fibers.

In some embodiments, the carbon material layer includes carbon fibers, and the carbon fibers can be prepared by one or both of fiber spinning and air-laying. Optionally, the carbon material layer is a carbon material layer formed of carbon fibers.

In some embodiments, the carbon material layer further comprises a binder, and the binder is used to bond adjacent carbon fibers. By adding the binder, the bonding force between adjacent carbon fibers can be improved, making the structure of the carbon material layer more stable. As an example of the selection of the binder, the binder comprises one or more of polyvinylidene fluoride, polyimide, polyamide-imide, styrene-butadiene rubber, nitrile rubber, their epoxy modified products, and their acrylate modified products.

In some embodiments, the carbon material layer further includes a conductive agent, which is located in the pores of the carbon material layer. By adding the conductive agent, the conductivity of the electrode plate can be further improved, thereby improving the electrical performance of the battery. The conductive agent includes one or more of superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. Optionally, the carbon black includes one or more of Super P, Super S, acetylene black and Ketjen black. Optionally, the conductive agent is a mixture of carbon black and carbon nanotubes in a mass ratio of (0.1 to 10): 1. Further optionally, the mass ratio of carbon black to carbon nanotubes is 0.5: 1, 0.8: 1, 1: 1, 1.2: 1, 1.5: 1, 2: 1, 5: 1, 8: 1, 10: 1, etc. It is understandable that the mass ratio of carbon black and carbon nanotubes can also be selected in the range of (0.1 to 10): 1.

Optionally, the mass ratio of the conductive agent to the carbon material layer is (0.1-10):1. Optionally, the mass ratio of the conductive agent to the carbon material layer is 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 4:3, 1.5:1, 5:3, 2:1, 2.5:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc. Understandably, the mass ratio of the conductive agent to the carbon material layer can also be selected in the range of (0.1-10):1. The mass ratio of the conductive agent to the carbon material layer in the range of (0.1-10):1 can enable the electrode plate to better balance excellent conductivity and excellent tensile strength.

In some embodiments, the carbon material layer includes a conductive agent and a binder. Optionally, the mass ratio of the conductive agent to the binder is (0.1-4): (0.1-3). Optionally, the mass ratio of the conductive agent to the binder can be, but is not limited to, (0.1-4): 0.1, (0.1-4): 0.2, (0.1-4): 0.3, (0.1-4): 0.5, (0.1-4): 0.8, (0.1-4): 1, (0.1-4): 1.2, (0.1-4): 1.5, (0.1-4): 1.8, (0.1-4): 2, (0.1-4): 2.2, (0.1-4): 2.5, (0.1-4): 2.8, (0.1-4): 3, etc. It is understandable that the mass ratio of the conductive agent to the binder may be other suitable selections within the range of (0.1-4): (0.1-3).

The present application also provides a method for preparing an electrode plate, which comprises: arranging an active layer on at least one surface of a carbon material layer, and allowing part of the active material of the active layer to penetrate into the pores of the carbon material layer.

Optionally, disposing the active layer on at least one surface of the carbon material layer includes: alternately stacking the active layer and the carbon material layer so that the number of active layers is equal to the number of carbon material layers, or the active layer has one more layer than the carbon material layer.

In some embodiments, the active slurry is transferred to the corresponding surface of the carbon material layer to form the active layer, wherein a portion of the active material in the active slurry penetrates into the pores of the carbon material layer. The carbon material layer having pores has good wettability with the active slurry, and the active layer is formed by transferring the active slurry to the corresponding surface of the carbon material layer. The preparation method is simple and easy, and it is convenient to make a portion of the active material in the active slurry penetrate into the pores of the carbon material layer.

It is understood that the active slurry can be a positive electrode active slurry or a negative electrode active slurry. When a positive electrode active material is used, a positive electrode sheet can be obtained. When a negative electrode active material is used, a negative electrode sheet can be obtained. It is also understood that in a battery, the positive electrode sheet and the negative electrode sheet can be used as a positive electrode sheet and a negative electrode sheet, respectively.

In some embodiments, before disposing the active layer on at least one surface of the carbon material layer, the method further includes filling the pores of the carbon material layer with a conductive agent.

Optionally, filling the pores of the carbon material layer with a conductive agent includes: transferring a modified slurry containing a conductive agent to the carbon material layer. Optionally, transferring the modified slurry containing a conductive agent to the carbon material layer may be coating the modified slurry containing a conductive agent on the carbon material layer, or immersing the carbon material layer in the modified slurry containing a conductive agent. Further optionally, the mass ratio of the solvent to the conductive agent in the modified slurry is (65-99): (0.5-20). For example, the mass ratio of the solvent to the conductive agent in the modified slurry can be (65-99): 0.5, (65-99): 0.8, (65-99): 1, (65-99): 2, (65-99): 3, (65-99): 4, (65-99): 5, (65-99): 8, (65-99): 10, (65-99): 12, (65-99): 15, (65-99): 18, (65-99): 20, etc. It is understood that the mass ratio of the solvent to the conductive agent in the modified slurry can also be other suitable selections within the range of (65-99): (0.5-20). It is also understood that the solvent in the modified slurry includes at least one of NMP and water.

In some embodiments, after the conductive agent is filled into the pores of the carbon material layer, the carbon material layer is flattened. Optionally, after the carbon material layer is flattened, the carbon material layer is rolled up.

In some embodiments, the carbon material layer includes carbon fibers, the carbon fibers are interwoven to form the pores, and the modified slurry further contains a binder. Optionally, the mass ratio of the conductive agent to the binder is (0.1-4): (0.1-3). Optionally, the mass ratio of the conductive agent to the binder can be, but is not limited to, (0.1-4): 0.1, (0.1-4): 0.2, (0.1-4): 0.3, (0.1-4): 0.5, (0.1-4): 0.8, (0.1-4): 1, (0.1-4): 1.2, (0.1-4): 1.5, (0.1-4): 1.8, (0.1-4): 2, (0.1-4): 2.2, (0.1-4): 2.5, (0.1-4): 2.8, (0.1-4): 3, etc. It is understandable that the mass ratio of the conductive agent to the binder may be other suitable selections within the range of (0.1-4): (0.1-3).

In some embodiments, the modified slurry includes a solvent, a conductive agent, and a binder, wherein the mass ratio of the solvent, the conductive agent, and the binder is (65-99): (0.5-20): (0.5-15).

The present application provides a secondary battery. The secondary battery includes the above-mentioned electrode plate. The secondary battery is suitable for various battery-using electrical devices, such as mobile phones, portable devices, laptop computers, battery cars, electric toys, electric tools, electric cars, ships and spacecraft, etc. For example, the spacecraft includes airplanes, rockets, space shuttles and spacecrafts, etc.

The present application also provides an electric device, which includes the secondary battery mentioned above.

The secondary battery, battery module, battery pack, and electric device of the present application are described below with reference to the accompanying drawings as appropriate.

Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

Positive electrode

The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver 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.).

As an example, the positive electrode active material may include a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, 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 LiNi1 _/ 3Co1 _/ _3Mn1 _/ _3O2 (also referred to as _NCM333 ), _{LiNi0.5Co0.2Mn0.3O2} (also referred _to _as _NCM523 ₎ _, _{LiNi0.5Co0.25Mn0.25O2} (also referred _to as _NCM211 ₎ , _{LiNi0.6Co0.2Mn0.2O2} (also referred to as _NCM622 ), _{LiNi0.8Co0.1Mn0.1O2} (also referred to _as _NCM811 ), lithium _nickel _cobalt aluminum oxide ( _such as LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and at least one of modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO ₄ (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. The weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100 weight %, based on the total weight of the positive electrode film layer.

In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0 to 20 weight%, based on the total weight of the positive electrode film layer.

In some embodiments, the positive electrode film layer may further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode film layer is 0 to 20 weight %, based on the total weight of the positive electrode film layer.

In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40-80wt%, and the viscosity at room temperature is adjusted to 5000-25000mPa·s, the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, it is cold-pressed by a cold rolling mill to form a positive electrode sheet; the positive electrode powder coating unit area density is 150-350mg/ ^m2 , and the positive electrode sheet compaction density is 3.0-3.6g/ ^cm3 , and can be 3.3-3.5g/ ^cm3 . The compaction density is calculated as follows: compaction density = coating area density/(thickness of the sheet after extrusion-thickness of the current collector).

It is understandable that the positive electrode sheet in the embodiment of the present application can be made by using the above-mentioned positive electrode sheet as the positive electrode sheet body and forming a solid electrolyte interface film on the surface of the positive electrode sheet body.

Negative electrode

The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver 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.).

In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more. The weight ratio of the negative electrode active material in the negative electrode film layer is 70 to 100% by weight, based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS). The weight ratio of the binder in the negative electrode film layer is 0 to 30% by weight, based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode film layer may further include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The weight ratio of the conductive agent in the negative electrode film layer is 0 to 20 weight %, based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode film layer may further include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc. The weight ratio of the other additives in the negative electrode film layer is 0 to 15 weight %, based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa·s; the obtained negative electrode slurry is coated on the negative electrode collector, and after a drying process, cold pressing such as rolling, a negative electrode sheet is obtained. The negative electrode powder coating unit area density is 75-220mg/ ^m2 , and the negative electrode sheet compaction density is 1.2-2.0g/ ^m3 .

It can be understood that the negative electrode sheet in the embodiment of the present application can be made by using the above-mentioned negative electrode sheet as the negative electrode sheet body and forming a solid electrolyte interface film on the surface of the negative electrode sheet body.

Electrolytes

The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalatoborate) (LiBOB), lithium difluorophosphate (LiPO ₂ F ₂ ), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP). The concentration of the electrolyte salt is generally 0.5 to 5 mol/L.

In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

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.

Isolation film

In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer package that can be used to encapsulate the electrode assembly and the electrolyte.

In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. may be listed. The present application has no particular restrictions on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG. 3 is a secondary battery 5 of a square structure as an example.

In some embodiments, referring to FIG. 4 , the outer package may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

FIG5 is a battery module 4 as an example. Referring to FIG5 , in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

Optionally, the battery module 4 may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.

In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

FIG6 and FIG7 are battery packs 1 as an example. Referring to FIG6 and FIG7 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

FIG8 is an example of an electric device. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or a battery module may be used.

Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

Example

In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in conjunction with the embodiments and drawings. Obviously, the described embodiments are only 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.

If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

Embodiment 1:

(1) In this embodiment, the carbon material layer is a polyacrylonitrile-based carbon fiber mesh after graphitization at 2000°C, and the carbon fibers are distributed in a grid-like pattern, with the angle between the rows and the columns being 90°. The carbon fiber mesh is obtained by fiber weaving, has a thickness of 10 μm, a carbon content of 95.0%, and a porosity of 55%.

(2) The modified slurry in this embodiment includes a solvent, a conductive agent and a binder, wherein the mass ratio of the solvent, the conductive agent and the binder is 90:5:5. The solvent is NMP, the conductive agent is carbon nanotubes, and the binder is PVDF.

(3) The active slurry in this embodiment is a positive electrode active slurry. The positive electrode active slurry is composed of positive electrode active material NCM ₃₃₃ , conductive carbon black SP and binder PVDF in a weight ratio of 97:1:2.

(4) The method for preparing the electrode plate in this embodiment includes the following steps:

S01: The carbon fiber mesh is immersed in the modification slurry for pretreatment, and then taken out, dried, flattened, and rolled up for use.

S02: coating an active slurry on one surface of a pretreated carbon fiber mesh, and then laminating it with another pretreated carbon fiber mesh, and then coating the active slurry on the surface of the carbon fiber mesh to obtain an electrode sheet with a 5-layer structure of active layer-carbon fiber mesh-active layer-carbon fiber mesh-active layer. The thickness of the electrode sheet is 150 μm.

Embodiment 2:

(1) In this embodiment, the carbon material layer is a polyacrylonitrile-based carbon fiber mesh that has been graphitized at 2800°C. The distribution of the carbon fibers is disordered, and the maximum spacing between adjacent carbon fibers is 60 μm. The carbon fiber mesh is obtained by airflow forming, has a thickness of 10 μm, a carbon content of 99.5%, and a porosity of 90%.

(2) The modified slurry in this embodiment includes a solvent, a conductive agent and a binder. The solvent is NMP, the conductive agent is carbon nanotubes and Super P, and the binder is PVDF. The mass ratio of the solvent, carbon nanotubes, Super P and binder is 90:3:3:4.

(3) The active slurry in this embodiment is a positive electrode active slurry. The positive electrode active slurry is composed of NCM ₃₃₃ , conductive carbon black SP and binder PVDF in a weight ratio of 97:1:2.

(4) The method for preparing the electrode sheet in this embodiment includes the following steps:

S01: Transfer and coat the modified slurry onto the carbon fiber mesh for pretreatment, then take it out, dry it, flatten it, and roll it up for use.

S02: coating an active slurry on one surface of a pretreated carbon fiber mesh, and then laminating it with another pretreated carbon fiber mesh, and then coating the active slurry on the surface of the carbon fiber mesh, and then laminating the carbon fiber mesh, and then coating the active slurry to obtain an electrode sheet with a 7-layer structure of active layer-carbon fiber mesh-active layer-carbon fiber mesh-active layer-carbon fiber mesh-active layer. The thickness of the electrode sheet is 150 μm.

Example 3

Compared with Example 2, the difference of this embodiment is that the electrode plate has a 9-layer structure of active layer-carbon fiber mesh-active layer-carbon fiber mesh-active layer-carbon fiber mesh-active layer-carbon fiber mesh-active layer, and the thickness of the electrode plate is 150μm.

Example 4

Compared with Example 1, the difference of this embodiment is that the electrode plate has a three-layer structure of active layer-carbon fiber mesh-active layer, and the thickness of the electrode plate is 150 μm.

Example 5

Compared with Example 1, the difference of this embodiment is that the electrode plate is a two-layer structure of active layer-carbon fiber mesh, and the thickness of the electrode plate is 150 μm.

Example 6

Compared with Example 1, the difference of this embodiment is that the electrode plate has a four-layer structure of active layer-carbon fiber mesh-active layer-carbon fiber mesh, and the thickness of the electrode plate is 150 μm.

Example 7

Compared with Example 1, the difference of this embodiment is that the electrode plate is a negative electrode plate. Among them, the active slurry in this embodiment is a negative electrode active slurry. The negative electrode active slurry is composed of negative electrode active materials graphite, CMC, SBR, and conductive agent SP, according to the mass ratio of 90:1:2:7.

Comparative Example 1

A 12 μm thick aluminum foil was used as the current collector, and the active slurry was coated on both sides. The thickness of the electrode sheet was 150 μm. The active slurry was the same as that in Example 1.

Comparative Example 2

Compared with Example 2, the difference of this embodiment is that the electrode plate has a three-layer structure of carbon fiber mesh-active layer-carbon fiber mesh, and the thickness of the electrode plate is 150 μm.

Preparation of batteries

(1) Preparation of positive electrode sheet

In the batteries corresponding to Examples 1 to 6 and Comparative Examples 1 to 2, the positive electrode sheets are the electrode sheets corresponding to Examples 1 to 6 and Comparative Examples 1 to 2 as the positive electrode sheets.

The positive electrode plate of the battery corresponding to Example 7 adopts 12 μm thick aluminum foil.

(2) Preparation of negative electrode sheet

In the batteries corresponding to Examples 1 to 6 and Comparative Examples 1 to 2, the preparation method of the negative electrode sheet is as follows: using silicon carbon material as the negative electrode active material, thickener CMC, adhesive styrene butadiene rubber, and conductive agent SP, are mixed in a mass ratio of 90:1:2:7, deionized water is added, and a negative electrode slurry is obtained under the action of a vacuum mixer, and the solid content of the negative electrode slurry is 30wt%. The negative electrode slurry is evenly coated on a copper foil, and after drying and cold pressing, the corresponding negative electrode sheet is obtained.

In the battery corresponding to Example 7, the negative electrode plate uses the electrode plate corresponding to Example 7 as the negative electrode plate.

In the battery corresponding to Example 8, the positive electrode sheet uses the electrode sheet corresponding to Example 1 as the positive electrode sheet, and the negative electrode sheet uses the electrode sheet corresponding to Example 7 as the negative electrode sheet.

(3) Isolation film

A 12μm thick polypropylene isolation film was selected.

(4) Preparation of electrolyte

The organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60. In an argon atmosphere glove box with a water content of <0.1ppm, fully dried lithium salt LiPF6 is dissolved in the organic solvent and mixed evenly to obtain an electrolyte. The concentration of the lithium salt is 1 mol/L.

(5) Preparation of batteries

The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is placed between the positive and negative electrode sheets to play an isolating role. After being wound into a square bare battery cell, it is loaded into a battery casing, and then after standing and forming processes, a lithium-ion battery is obtained.

Test Case

(1) The electrode plates in the examples and comparative examples were made into strips with a length of 15 cm and a width of 5 cm, and the breaking tensile force test was performed. The test method was: using a tensile machine to stretch at a stretching speed of 50 mm/min, and recording the maximum force at break. The test results are shown in Table 1.

(2) Battery test

Test the capacity and internal resistance of the battery. Capacity test method: Charge to 4.2V at 1C constant current at 25°C, then charge to ≤0.5C at constant voltage, then discharge to 2.8V at 1C constant current. The discharge capacity is the battery capacity. The internal resistance test method refers to the HPPC test method in the US FreedomCAR Battery Test Manual. The test results are shown in Table 2. The test results are shown in Table 1.

Table 1

The	样片断裂拉伸力/NSample breaking tensile force/N	电池容量/mAhBattery capacity/mAh	内阻/mΩInternal resistance/mΩ
实施例1Example 1	170170	29602960	22twenty two
实施例2Example 2	180180	29102910	2525
实施例3Example 3	215215	28602860	1818
实施例4Example 4	9090	30003000	2828
实施例5Example 5	8484	29802980	3131

实施例6Example 6	165165	29402940	23twenty three
实施例7Example 7	168168	27002700	2929
对比例1Comparative Example 1	8585	26402640	3838
对比例2Comparative Example 2	160160	28502850	1515
实施例8Example 8	//	31003100	1515

It can be seen from Table 1 that the tensile strength of the electrode plate in the embodiment is relatively high, and the energy density of the battery corresponding to the electrode plate in the embodiment is relatively high and the internal resistance is relatively low.

The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

An electrode plate, characterized in that it includes a carbon material layer and an active layer, the carbon material layer has pores, the active layer is located on at least one surface of the carbon material layer, the active layer contains active material, and part of the active material penetrates into the pores.
The electrode plate according to claim 1 is characterized in that the active layer and the carbon material layer are alternately stacked; the number of layers of the active layer is equal to the number of layers of the carbon material layer, or the active layer has one more layer than the carbon material layer.
The electrode plate according to claim 2 is characterized in that the number of layers of the carbon material layer is ≥ 2.
The electrode plate according to any one of claims 1 to 3, characterized in that the carbon material layer satisfies one or more of the following characteristics:

(1) The thickness of the carbon material layer is 1 μm to 20 μm;

(2) the carbon content of the carbon material layer is 90.00 to 99.99%;

(3) The porosity of the carbon material layer is 13% to 91%.
The electrode plate according to any one of claims 1 to 4, characterized in that the carbon material layer comprises carbon fibers, and the carbon fibers are interwoven to form the pores.
The electrode plate according to claim 5, characterized in that the carbon fiber satisfies one or more of the following characteristics:

(1) The diameter of the carbon fiber is 1 μm to 20 μm;

(2) The length of the carbon fiber is ≥50 mm.
The electrode plate according to claim 5 or 6 is characterized in that, in the projection of the carbon material layer on a plane perpendicular to its thickness direction, the distance between adjacent carbon fibers is 0 to 100 μm.
The electrode plate according to any one of claims 5 to 7 is characterized in that the distribution of the carbon fibers includes one or more of a determinant distribution, a unidirectional distribution and a disordered distribution.
The electrode plate according to claim 8 is characterized in that the angle formed between the rows and columns in the determinant distribution is 45° to 90°.
The electrode plate according to any one of claims 5 to 9 is characterized in that the carbon fiber includes one or more of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber, viscose-based carbon fiber and vapor-grown carbon fiber.
The electrode plate according to any one of claims 5 to 10, characterized in that the carbon material layer further comprises a binder, and the binder is used to bond adjacent carbon fibers;

Optionally, the adhesive includes one or more of polyvinylidene fluoride, polyimide, polyamide-imide, styrene-butadiene rubber, nitrile rubber, epoxy modified products thereof, and acrylate modified products thereof.
The electrode plate according to claim 11, characterized in that the carbon material layer further comprises a conductive agent, and the conductive agent is located in the pores of the carbon material layer;

Optionally, the mass ratio of the conductive agent to the binder is (0.1-4): (0.1-3);

Optionally, the conductive agent includes one or more of superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
The electrode plate according to any one of claims 1 to 10, characterized in that the carbon material layer further comprises a conductive agent, and the conductive agent is located in the pores of the carbon material layer;

Optionally, the conductive agent includes one or more of superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
The method for preparing an electrode sheet according to any one of claims 1 to 13, characterized in that it comprises:

The active layer is disposed on at least one surface of the carbon material layer, and a portion of the active material of the active layer is infiltrated into the pores of the carbon material layer.
The method for preparing an electrode sheet according to claim 14, characterized in that the step of disposing the active layer on at least one surface of the carbon material layer comprises:

The active layers and the carbon material layers are alternately stacked so that the number of active layers is equal to the number of carbon material layers, or the number of active layers is one more than the number of carbon material layers.
The method for preparing an electrode plate according to claim 14 or 15 is characterized in that the active slurry is transferred to the corresponding surface of the carbon material layer to form the active layer, wherein part of the active material in the active slurry penetrates into the pores of the carbon material layer.
The method for preparing an electrode plate according to any one of claims 14 to 16 is characterized in that before the active layer is arranged on at least one surface of the carbon material layer, it also includes a step of filling a conductive agent in the pores of the carbon material layer.
The method for preparing an electrode sheet according to claim 17, characterized in that filling the pores of the carbon material layer with a conductive agent comprises:

transferring the modified slurry containing the conductive agent onto the carbon material layer;

Optionally, the mass ratio of the solvent in the modified slurry to the conductive agent is (65-99): (0.5-20).
The method for preparing an electrode plate according to claim 18, characterized in that the carbon material layer comprises carbon fibers, the carbon fibers are interwoven to form the pores, and the modified slurry further comprises a binder;

Optionally, the mass ratio of the conductive agent to the binder is (0.1-4): (0.1-3).
A secondary battery, characterized by comprising the electrode plate according to any one of claims 1 to 13.
An electrical device, characterized by comprising the secondary battery according to claim 20.