Positive composite current collector, positive electrode sheet, lithium ion battery, and electric device

Abstract

The application provides a positive electrode composite current collector, a positive electrode tab, a lithium ion battery and an electric device. The positive electrode composite current collector comprises a base material and a water-based coating layer located on at least one side of the base material. The water-based coating layer comprises a magnesium silicate additive, a conductive agent and a water-based binder. The mass ratio of the magnesium silicate additive and the water-based binder is (0.05-1.5):1. The magnesium silicate additive comprises one or more of calcium magnesium silicate, sodium magnesium silicate, lithium magnesium silicate, aluminum magnesium silicate and manganese magnesium silicate. By adding the magnesium silicate additive in the water-based coating layer and using the water-based binder, the uniformity of the conductive agent distribution can be effectively improved, and the edge shrinkage problem of the water-based positive electrode slurry coated on the water-based coating layer foil can be solved. Meanwhile, the surface resistance of the whole tab is reduced, and the bonding performance of the tab is improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a positive electrode composite current collector, a positive electrode sheet, a lithium-ion battery, and an electrical device. Background Technology

[0002] In recent years, the application of lithium-ion batteries has provided important support for portable electronic devices, new energy vehicles and smart grids. Lithium-ion battery technology has developed rapidly. With the improvement of living standards and rapid economic development, environmentally friendly and safer batteries are favored.

[0003] Lithium-ion batteries use various types of cathode materials, such as lithium nickel manganese cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, and lithium manganese oxide. Regardless of the cathode material, most lithium-ion batteries use oil-based solvents like N-methylpyrrolidone (NMP) as the solvent for the cathode slurry. However, NMP is toxic, and its recycling incurs significant human and material costs for manufacturers. Therefore, some industry professionals have experimented with using water as the cathode slurry solvent. While water is environmentally friendly, safe, and easy to handle, it places higher demands on the foil material. When coating the foil with the water-based cathode slurry, a water-based coating needs to be pre-formed on its surface to create a water-coated foil. Currently, commonly used water-coated foils are prone to edge shrinkage and uneven conductive agent distribution after coating with the water-based cathode slurry. Summary of the Invention

[0004] Based on this, this application provides a positive electrode composite current collector, a positive electrode sheet, a lithium-ion battery, and an electrical device to improve the problems of edge shrinkage and uneven distribution of conductive agent that occur when aqueous positive electrode slurry is coated on aqueous coating foil.

[0005] The first aspect of this application provides a positive electrode composite current collector, comprising:

[0006] Substrate; and

[0007] A water-based coating is located on at least one side of the substrate. The water-based coating comprises a magnesium silicate additive, a conductive agent, and a water-based binder. The mass ratio of the magnesium silicate additive to the water-based binder is (0.05-1.5):1. The magnesium silicate additive includes one or more of calcium magnesium silicate, sodium magnesium silicate, lithium magnesium silicate, aluminum magnesium silicate, and manganese magnesium silicate.

[0008] In some embodiments, the magnesium silicate additive includes one or more of magnesium aluminum silicate and magnesium lithium silicate.

[0009] In some embodiments, the magnesium silicate additive accounts for 3%-15% by mass in the aqueous coating, and optionally 5%-10%.

[0010] In some embodiments, the magnesium silicate additive used in preparing the aqueous coating has a sheet-like structure with a thickness of 5 nm-100 nm and a cross-sectional diameter of 5 µm-80 µm.

[0011] Optionally, the thickness of the sheet structure is 5nm-20nm, and the cross-sectional diameter of the sheet structure is 5µm-50µm.

[0012] In some embodiments, the mass ratio of the magnesium silicate additive to the aqueous binder is (0.14-0.75):1.

[0013] In some embodiments, the aqueous binder comprises one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyolefin, polyimide, polyacrylamide, and polyamic acid; and / or

[0014] The water-based adhesive accounts for 10%-50% of the mass of the water-based coating, and can be selected as 25%-45%.

[0015] In some embodiments, the conductive agent includes at least one of the following features (1)-(2):

[0016] (1) The conductive agent includes a carbon-based conductive agent;

[0017] Optionally, the conductive agent includes one or more of carbon black, carbon nanotubes, and graphene, and may be graphene.

[0018] (2) The conductive agent in the water-based coating has a mass ratio of 45%-80%, and can be selected as 45%-65%.

[0019] In some embodiments, the substrate is aluminum foil or a composite substrate formed by combining aluminum foil and polymer materials.

[0020] In some embodiments, the thickness of the aqueous coating located on one side of the substrate is 0.5 μm-5 μm.

[0021] A second aspect of this application provides a positive electrode sheet that includes the positive electrode composite current collector of the first aspect of this application.

[0022] In some embodiments, the positive electrode sheet includes a positive electrode active material layer located on the side of the positive electrode composite current collector having an aqueous coating. The positive electrode active material layer contains a positive electrode active material, which includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate, and may be selected as lithium nickel manganese oxide.

[0023] A third aspect of this application provides a lithium-ion battery, including the positive electrode sheet of the second aspect of this application.

[0024] The fourth aspect of this application provides an electrical device including a lithium-ion battery as described in the third aspect of this application.

[0025] The aforementioned positive electrode composite current collector, by adding magnesium silicate-based additives to the aqueous coating and using them in a specific ratio with an aqueous binder, can effectively improve the uniformity of the conductive agent distribution and alleviate the edge shrinkage problem of the aqueous positive electrode slurry coated on the aqueous coating foil. Simultaneously, it reduces the overall surface resistivity of the electrode and improves the adhesion performance of the electrode. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a positive electrode composite current collector provided in one embodiment of this application. In this diagram, 11 represents the substrate, and 12 represents the aqueous coating. Detailed Implementation

[0028] To facilitate understanding of the present invention, a more complete description of this application will be provided below with reference to relevant embodiments. Preferred embodiments of the present application are given below. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the disclosure of this application will be achieved.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0030] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0031] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0032] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0033] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0034] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0035] In this application, unless otherwise specified, the terms "size," "particle size," and "diameter" generally refer to average values. In this application, "particle size" and "particle diameter" have the same definition, both representing the average particle size of spheres or spheroids.

[0036] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0037] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0038] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0039] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0041] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, but sequentially is preferred.

[0042] Using water as a solvent for the positive electrode slurry is environmentally friendly, safe, and easy to handle. However, water-based positive electrode slurries place higher demands on the foil material. When coating the foil with the water-based positive electrode slurry, a water-based coating needs to be pre-formed on its surface to create a water-coated foil. Currently, commonly used water-coated foils are prone to processing problems such as edge shrinkage and uneven distribution of conductive agent after coating with the water-based positive electrode slurry. Furthermore, commonly used water-coated foils also suffer from the problem of electrode sheet detachment after coating with the water-based positive electrode slurry.

[0043] Based on the above problems, this application provides an aqueous coating containing a conductive agent, a magnesium silicate additive, and an aqueous binder on at least one side of an aluminum foil or composite aluminum foil, and adjusts the ratio of the magnesium silicate additive and the aqueous binder to improve the problems of edge shrinkage and uneven distribution of conductive agent when the aqueous positive electrode paste is coated on the aqueous coating foil.

[0044] The first aspect of this application provides a positive electrode composite current collector, including a substrate and an aqueous coating located on at least one side of the substrate. The aqueous coating comprises a magnesium silicate additive, a conductive agent, and an aqueous binder. The mass ratio of the magnesium silicate additive to the aqueous binder is (0.05-1.5):1. The magnesium silicate additive includes one or more of magnesium calcium silicate, magnesium sodium silicate, magnesium lithium silicate, magnesium aluminum silicate, and magnesium manganese silicate.

[0045] As an example, the mass ratio of magnesium silicate additives to water-based binders can be, but is not limited to, 0.05:1, 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, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, or any range between two of the above ratios. When the mass ratio of magnesium silicate additives to water-based binders is within the above ranges, the magnesium silicate additives and water-based binders can maintain a good synergistic effect, resulting in excellent processing performance of the water-based coating while ensuring uniform distribution of conductive agent particles. When the amount of magnesium silicate-based additive is too high, the magnesium silicate-based additive itself has a large attraction while the adsorption potential of the aqueous binder is insufficient, which easily causes local agglomeration and powdering of the conductive agent particles. When the amount of magnesium silicate-based additive is too low, the aqueous binder preferentially adsorbs on the surface of the conductive agent particles, while the adsorption effect on the magnesium silicate-based additive is poor, which easily leads to a decrease in uniform suspension effect, which will also further affect the dispersion of conductive agent particles. Optionally, the mass ratio of magnesium silicate-based additive to aqueous binder is (0.06-1.5):1.

[0046] In the preparation of the positive electrode composite current collector, magnesium silicate-based additives can rapidly disperse in an aqueous system, forming a card-like structure containing a large number of water molecules. This further forms a uniform suspension suitable for coating. Due to the strong hydrophilic properties of the magnesium silicate-based additives, they provide spreading properties, resulting in a uniform surface tension at both the edges and center of the prepared positive electrode composite current collector. This ensures good compatibility with aqueous positive electrode slurries and improves the edge shrinkage phenomenon that occurs during the coating of aqueous positive electrode slurries. Furthermore, the addition of magnesium silicate-based additives creates excellent suspension effects in suspension systems containing conductive agents and other solid particles. The conductive agents can be uniformly distributed within the card-like structure, improving the uniformity of conductive agent distribution.

[0047] Understandably, the positive electrode composite current collector of this application, by adding magnesium silicate-based additives to the aqueous coating and using it in conjunction with an aqueous binder, can effectively improve the uniformity of the conductive agent distribution and alleviate the edge shrinkage problem of the aqueous positive electrode slurry coated on the aqueous coating foil. Simultaneously, it reduces the overall surface resistivity of the electrode and improves the adhesion performance of the electrode.

[0048] It should be noted that the positive electrode composite current collector may have an aqueous coating on only one side of the substrate, or it may have an aqueous coating on both sides of the substrate simultaneously. For example... Figure 1 As shown, Figure 1 a) indicates that the substrate 11 has a water-based coating 12 on both sides; Figure 1 b) indicates that the water-based coating 12 is only present on one side of the substrate 11.

[0049] In some embodiments, the magnesium silicate-based additives include one or more of magnesium aluminum silicate and magnesium lithium silicate.

[0050] In some embodiments, the mass percentage of magnesium silicate-based additives in the aqueous coating is 3%-15%; for example, it can be, but is not limited to, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any range before any two of the above values. When the mass percentage of magnesium silicate-based additives in the aqueous coating is within the above range, it is beneficial to achieve the effects of solving the edge shrinkage problem of aqueous cathode slurry and optimizing the uniformity of conductive agent distribution while maintaining battery energy density. Optionally, the mass percentage of magnesium silicate-based additives in the aqueous coating is 5%-10%.

[0051] As one possible implementation, the magnesium silicate-based additive has a sheet-like structure with a thickness of 5 nm-100 nm and a cross-sectional diameter of 5 µm-80 µm. When the magnesium silicate-based additive has a sheet-like structure and the size of the sheet-like structure is within the above range, it facilitates rapid and uniform dispersion of the magnesium silicate-based additive, and also allows for more thorough contact between the magnesium silicate-based additive and the conductive agent particles in the microstructure of the aqueous coating.

[0052] As an example, the thickness of the sheet structure can be, but is not limited to, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, or any two of the above thicknesses.

[0053] As an example, the cross-sectional diameter of the sheet-like structure can be, but is not limited to, 5µm, 10µm, 15µm, 20µm, 25µm, 30µm, 35µm, 40µm, 45µm, 50µm, 55µm, 60µm, 65µm, 70µm, 75µm, 80µm, or any range between two of the above diameters.

[0054] In some alternative implementations, the thickness of the sheet structure is 5nm-20nm, and the cross-sectional diameter of the sheet structure is 5µm-50µm.

[0055] In one possible implementation, the mass ratio of magnesium silicate-based additive to water-based binder is (0.14-0.75):1. Optionally, the mass ratio of magnesium silicate-based additive to water-based binder is (0.143-0.75):1.

[0056] In some embodiments, the aqueous binder includes one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyolefin, polyimide, polyacrylamide, and polyamic acid.

[0057] In some exemplary embodiments, the water-based binder accounts for 10%-50% of the mass of the water-based coating; for example, it can be, but is not limited to, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any range between two of the above values. When the amount of water-based binder is within the above range, it can ensure that the water-based active material layer has strong peel force on the positive electrode composite current collector.

[0058] In some alternative implementations, the water-based binder accounts for 25%-45% of the mass of the water-based coating.

[0059] In some embodiments, the conductive agent includes a carbon-based conductive agent. Optionally, the conductive agent includes one or more of carbon black, carbon nanotubes, and graphene. More optionally, the conductive agent includes graphene.

[0060] In some exemplary embodiments, the conductive agent includes zero-dimensional carbon black, one-dimensional fibrous carbon nanotubes, and two-dimensional layered graphene.

[0061] In some optional embodiments, the conductive agent accounts for 45%-80% of the mass of the aqueous coating; for example, it can be, but is not limited to, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any range between two of the above values. When the amount of conductive agent is within the above range, it can provide more contact potential to the conductive network between the aqueous active material layer and the aqueous coating, further improving the overall conductivity of the aqueous positive electrode. Optionally, the conductive agent accounts for 45%-65% of the mass of the aqueous coating.

[0062] As one possible implementation, the aqueous coating comprises, by weight percentage: 3%-15% magnesium silicate additives, 45%-80% conductive agents, and 10%-50% aqueous binders.

[0063] In some alternative embodiments, the aqueous coating comprises, by weight percentage: 5%-10% magnesium silicate additives, 45%-65% conductive agents, and 25%-45% aqueous binders.

[0064] In some embodiments, the substrate is aluminum foil or a composite substrate formed by combining aluminum foil with polymer materials.

[0065] As one possible implementation, the thickness of the aqueous coating on one side of the substrate is 0.5 μm to 5 μm; for example, it can be, but is not limited to, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any range between two of the above thicknesses. When the thickness of the aqueous coating on one side is within the above range, it is possible to ensure that the aqueous coating has excellent adhesion, conductivity, and high-pressure corrosion resistance even when the aqueous coating is relatively thin.

[0066] In some embodiments, the preparation method of the positive electrode composite current collector includes the following steps:

[0067] The conductive agent and magnesium silicate additive are mixed with water and stirred evenly. A water-based binder is added and stirred evenly to obtain a water-based coating slurry with a solid content of 0.5%-5%. The water-based coating slurry is then coated onto a substrate to prepare a positive electrode composite current collector.

[0068] A second aspect of this application provides a positive electrode sheet that includes the positive electrode composite current collector of the first aspect of this application.

[0069] In some embodiments, the positive electrode sheet includes a positive electrode active material layer located on the side of the positive electrode composite current collector having an aqueous coating. The positive electrode active material layer contains a positive electrode active material, which includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate. Optionally, the positive electrode active material is lithium nickel manganese oxide.

[0070] The positive electrode sheet of this application contains the above-mentioned positive electrode composite current collector and has high peel strength.

[0071] A third aspect of this application provides a lithium-ion battery that includes the positive electrode sheet of the second aspect of this application. The lithium-ion battery of this application incorporates the aforementioned positive electrode composite current collector, resulting in higher safety performance.

[0072] The fourth aspect of this application provides an electrical device that includes the lithium-ion battery of the third aspect of this application. This electrical device can be used in electric vehicles, electric bicycles, electric two-wheelers, electric vehicle power systems, energy storage systems, or mobile storage devices, etc., and is not specifically limited thereto.

[0073] The electrical device of this application includes the lithium-ion battery provided in this application, and therefore has at least the same advantages as the lithium-ion battery.

[0074] The technical solution of the present invention will be described in detail below with reference to specific embodiments. It should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this invention, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0075] In the specific embodiments described below, the measurement parameters involving raw material components may have slight deviations within the weighing accuracy range unless otherwise specified. Temperature and time parameters are subject to acceptable deviations due to instrument testing accuracy or operational precision.

[0076] I. Preparation of the positive electrode sheet

[0077] Example 1

[0078] Step S1. Mix aqueous graphene (as a conductive agent), magnesium aluminum silicate (as a magnesium silicate additive), and water, stir until homogeneous, add polyacrylic acid (PAA, as an aqueous binder), and continue stirring until homogeneous to obtain an aqueous coating slurry. The magnesium silicate additive has a sheet structure thickness of 50 nm and a cross-sectional diameter of 40 µm.

[0079] Step S2. The aqueous coating slurry is double-sided extruded and coated onto aluminum foil to form an aqueous coating on both sides of the aluminum foil. The coating is then dried to obtain a positive electrode composite current collector. The aluminum foil thickness is 12 μm, and the thickness of the aqueous coating on one side is 2 μm. The conductive agent accounts for 57% of the mass of the aqueous coating, the magnesium silicate additive accounts for 3% of the mass of the aqueous coating, and the aqueous binder accounts for 40% of the mass of the aqueous coating. The mass ratio of the magnesium silicate additive to the aqueous binder is 0.075:1.

[0080] Step S3. Coat both sides of the positive electrode composite current collector with high-voltage aqueous positive electrode slurry at a ratio of 180g / m² on each side. 2 The areal density is subjected to extrusion coating and rolled to 3.0 g / m². 3 The compaction density is used to obtain the positive electrode sheet. Among them, the solid part of the aqueous positive electrode slurry contains 95% by mass of lithium nickel manganese oxide, 3% by mass of carbon black SP, 2% by mass of polyacrylic acid binder, and water as solvent, with a solid content of 60%.

[0081] Example 2-23

[0082] The preparation methods of the positive electrode sheet in Examples 2-23 are similar to those in Example 1. The difference lies in at least one of the following: the type and / or amount of conductive agent, the type and / or amount of magnesium silicate additive, the type and / or amount of aqueous binder, the mass ratio of magnesium silicate additive to aqueous binder, and the thickness and cross-sectional diameter of the magnesium silicate additive sheet structure in step S2. The details are shown in Table 1 below.

[0083] Comparative Example 1

[0084] The difference between Comparative Example 1 and Example 1 is that: in Comparative Example 1, carbon black was used as a conductive agent in step S1 and no magnesium silicate additives were added; in step S2, the conductive agent accounted for 55% of the mass of the water-based coating and the water-based binder accounted for 45% of the mass of the water-based coating.

[0085] Comparative Example 2

[0086] The difference between Comparative Example 2 and Example 1 is that no magnesium silicate additive was added in step S1 of Comparative Example 2; and the mass percentage of the conductive agent in the aqueous coating was 55% and the mass percentage of the aqueous binder in the aqueous coating was 45% in step S2.

[0087] Comparative Example 3

[0088] The difference between Comparative Example 3 and Example 1 is that in step S2 of Comparative Example 3, the mass percentage of the conductive agent in the aqueous coating is 53.5%, the mass percentage of the magnesium silicate additive in the aqueous coating is 1.5%, the mass percentage of the aqueous binder in the aqueous coating is 45%, and the mass ratio of the magnesium silicate additive to the aqueous binder is 0.033:1.

[0089] Comparative Example 4

[0090] The difference between Comparative Example 4 and Example 1 is that in step S2 of Comparative Example 4, the mass percentage of the conductive agent in the aqueous coating is 73%, the mass percentage of the magnesium silicate additive in the aqueous coating is 17%, the mass percentage of the aqueous binder in the aqueous coating is 10%, and the mass ratio of the magnesium silicate additive to the aqueous binder is 1.7:1.

[0091] Comparative Example 5

[0092] The difference between Comparative Example 5 and Example 1 is that the same amount of magnesium silicate was used to replace magnesium aluminum silicate in Comparative Example 5, while everything else was the same.

[0093] Comparative Example 6

[0094] The difference between Comparative Example 6 and Example 1 is that the same amount of aluminum silicate was used to replace magnesium aluminum silicate in Comparative Example 6, while everything else is the same.

[0095] Comparative Example 7

[0096] The difference between Comparative Example 7 and Example 1 is that the same amount of magnesium silicate and aluminum silicate are used to replace magnesium aluminum silicate in Comparative Example 7, and the mass ratio of aluminum silicate to magnesium silicate is 1:1.

[0097] The parameter settings in the above embodiments and comparative examples are shown in Table 1.

[0098] Table 1

[0099]

[0100] Where n represents the mass ratio of magnesium silicate additives to water-based binders; PAA represents polyacrylic acid; PAM represents polyacrylamide; CMC represents carboxymethyl cellulose; and SBR represents styrene-butadiene rubber.

[0101] II. Positive Electrode Performance Testing

[0102] 1. Edge shrinkage test

[0103] The thickness difference between the high-voltage lithium nickel manganese oxide aqueous positive electrode slurry at different positive electrode current collector positions at the edge of the coated pad and the thickness difference in the middle of the coated electrode was used to characterize the positive electrode preparation process. A thickness difference exceeding 10 μm was considered severe edge shrinkage, a thickness difference between 5 μm and 10 μm was considered edge shrinkage, a thickness difference between 2 μm and 5 μm was considered slight edge shrinkage, and a thickness difference within 0-2 μm was considered no edge shrinkage. The results are shown in Table 2.

[0104] Table 2

[0105]

[0106] As shown in Table 2, comparative examples 1-2 exhibited severe edge shrinkage, comparative example 3 exhibited edge shrinkage, and comparative example 4 exhibited slight edge shrinkage, while examples 1-2 and 3 did not show any edge shrinkage. This indicates that when no magnesium silicate additive is added, or when the mass ratio of magnesium silicate additive to aqueous binder is not within (0.05-1.5):1, the positive electrode composite current collector prepared using aqueous coating slurry has poor adaptability to aqueous positive electrode slurry, leading to the occurrence of edge shrinkage. The addition of magnesium silicate-based additives improves the adaptability of the positive electrode composite current collector prepared with aqueous coating slurry to aqueous positive electrode slurry, greatly reducing the occurrence of edge shrinkage. The reason for this may be that magnesium silicate-based additives can disperse rapidly in aqueous systems, forming a card-like structure containing a large number of water molecules, further forming a uniform suspension that can be coated. Due to its strong hydrophilic properties, it provides spreadability, making the surface tension of the prepared positive electrode composite current collector uniform at the edges and the middle. This improves the adaptability of the positive electrode composite current collector to aqueous positive electrode slurry and solves the edge shrinkage phenomenon of aqueous positive electrode slurry. However, when there are more additives, the agglomeration of local conductive agent particles can cause local tension instability, further causing slight edge shrinkage.

[0107] 2. Conductive agent distribution uniformity test

[0108] The uniformity of conductive agent distribution in the aqueous coating of the positive current collector in this application is characterized by testing the standard deviation of the longitudinal surface resistivity of the positive electrode sheet. Five values ​​are measured for the longitudinal surface resistivity of each group. The mean of the five values ​​is used to characterize the overall surface resistivity performance of the electrode sheet, and the standard deviation of the five values ​​is used to evaluate the uniformity of conductive agent distribution in each group of electrodes. Generally, for the same conductive agent, the more uniform the distribution of conductive agent particles, the lower its surface resistivity value. The test method for the longitudinal surface resistivity is as follows:

[0109] The multimeter readings were used as the result of the longitudinal surface resistance. The positive and negative wires of the multimeter were connected to a fixed copper post with dimensions of 30*30*100mm. Each set of electrodes with dimensions of 70*70mm was cut and fixed. One of the copper posts was placed upside down on a horizontal surface, and then the electrodes were placed on the copper post. Another copper post was placed directly above the electrodes. The upper copper post was pressed down three times with the index and middle fingers. After waiting for 10 seconds, the readings were taken and recorded. The results are shown in Table 3.

[0110] Table 3

[0111]

[0112] As shown in Table 3, compared with Comparative Examples 1-7, the average surface resistivity of the electrodes in Examples 1-23 was significantly reduced, indicating that the surface resistivity of the positive electrode composite current collector itself decreased after the addition of magnesium silicate additives, resulting in a smaller overall longitudinal surface resistivity of the prepared positive electrode. The surface resistivity of the electrodes in Comparative Examples 3-4 was relatively large, indicating that both excessively high and low mass ratios of magnesium silicate aluminum additive to aqueous binder would increase the surface resistivity of the positive electrode composite current collector. The reasons for this may be as follows: when the amount of magnesium silicate additive added is too high, the magnesium silicate additive itself has a strong attraction while the adsorption potential of the aqueous binder is insufficient, easily causing local agglomeration and floating of conductive agent particles, leading to uneven distribution of the conductive agent and further resulting in a larger longitudinal surface resistivity of the electrode; when the amount of magnesium silicate additive added is too low, the aqueous binder preferentially adsorbs on the surface of the conductive agent particles, resulting in poor adsorption of the magnesium silicate additive, easily causing a decrease in uniform suspension effect, which will also further affect the dispersion of conductive agent particles and worsen the surface resistivity value.

[0113] Compared with Comparative Examples 1-7, the standard deviation of the electrode surface resistance in Examples 1-23 was significantly reduced, indicating that the addition of magnesium silicate-based additives can significantly improve the uniformity of the conductive agent distribution in the aqueous coating of the positive electrode composite current collector. This may be because the addition of magnesium silicate-based additives can create an excellent suspension effect in a suspension system containing solid particles such as conductive agents, allowing the conductive agent to be uniformly distributed in the card-like structure, thus improving the uniformity of the conductive agent distribution.

[0114] 3. Peel strength test

[0115] A universal tensile testing machine was used to perform a 180° peel test on the electrode sheet to test its peel strength. The results are shown in Table 4.

[0116] Table 4

[0117]

[0118] As shown in Table 4, compared with Comparative Examples 1-7, the peel strength of the electrodes in Examples 1-23 was improved, except for Example 10. This indicates that the addition of magnesium silicate-based additives can optimize the adhesion of the aqueous active material layer to the aqueous coated foil. The reason for this may be that the card-like structure of the magnesium silicate-based additives allows them to adsorb more water and particles. When the aqueous active material layer spreads on it, it facilitates the wetting and penetration of the aqueous positive electrode slurry, further improving the overall peel strength of the aqueous positive electrode. The lower peel strength of Example 10 may be due to its lower binder content, but it still shows a slight improvement compared to Comparative Example 4.

[0119] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0120] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A positive electrode composite current collector, characterized in that, include: Substrate; and A water-based coating is located on at least one side of the substrate. The water-based coating comprises a magnesium silicate additive, a conductive agent, and a water-based binder. The mass ratio of the magnesium silicate additive to the water-based binder is (0.05-1.5):

1. The magnesium silicate additive includes one or more of magnesium calcium silicate, magnesium sodium silicate, magnesium lithium silicate, magnesium aluminum silicate, and magnesium manganese silicate. The magnesium silicate additive accounts for 3%-15% of the mass of the aqueous coating; the magnesium silicate additive used in preparing the aqueous coating has a sheet-like structure with a thickness of 5nm-100nm and a cross-sectional diameter of 5µm-80µm.

2. The positive electrode composite current collector as described in claim 1, characterized in that, The magnesium silicate additives include one or more of magnesium aluminum silicate and magnesium lithium silicate.

3. The positive electrode composite current collector as described in claim 1, characterized in that, The magnesium silicate additive accounts for 5%-10% of the mass of the aqueous coating.

4. The positive electrode composite current collector as described in claim 1, characterized in that, The thickness of the sheet-like structure is 5nm-20nm, and the cross-sectional diameter of the sheet-like structure is 5µm-50µm.

5. The positive electrode composite current collector as described in claim 1, characterized in that, The mass ratio of the magnesium silicate additive to the aqueous binder is (0.14-0.75):

1.

6. The positive electrode composite current collector according to any one of claims 1 to 5, characterized in that, The aqueous binder comprises one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyolefin, polyimide, polyacrylamide, and polyamic acid; and / or The water-based adhesive accounts for 10%-50% of the mass of the water-based coating.

7. The positive electrode composite current collector as described in claim 6, characterized in that, The water-based adhesive accounts for 25%-45% of the mass of the water-based coating.

8. The positive electrode composite current collector as described in any one of claims 1 to 5, characterized in that, The conductive agent includes at least one of the following features (1)-(2): (1) The conductive agent includes a carbon-based conductive agent; (2) The conductive agent accounts for 45%-80% of the mass of the aqueous coating.

9. The positive electrode composite current collector as described in claim 8, characterized in that, The conductive agent includes one or more of carbon black, carbon nanotubes, and graphene.

10. The positive electrode composite current collector as described in claim 9, characterized in that, The conductive agent is graphene.

11. The positive electrode composite current collector as described in claim 8, characterized in that, The conductive agent accounts for 45%-65% of the mass of the aqueous coating.

12. The positive electrode composite current collector according to any one of claims 1 to 5, characterized in that, The substrate is aluminum foil or a composite substrate formed by combining aluminum foil and polymer materials.

13. The positive electrode composite current collector according to any one of claims 1 to 5, characterized in that, The thickness of the water-based coating located on one side of the substrate is 0.5μm-5μm.

14. A positive electrode plate, characterized in that, Includes the positive electrode composite current collector as described in any one of claims 1 to 13.

15. The positive electrode sheet as described in claim 14, characterized in that, The positive electrode sheet includes a positive active material layer located on the side of the positive composite current collector with an aqueous coating. The positive active material layer contains a positive active material, which includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

16. The positive electrode sheet as described in claim 15, characterized in that, The positive electrode active material is lithium nickel manganese oxide.

17. A lithium-ion battery, characterized in that, Including the positive electrode sheet as described in any one of claims 14-15.

18. An electrical appliance, characterized in that, Including the lithium-ion battery as described in claim 17.

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