Carbon material and preparation method, water-based conductive paint and carbon-coated aluminum foil

Abstract

To address the problem of poor adhesion of conventional water-based conductive paints to oil-stained aluminum foil surfaces, the present invention provides a carbon material, a preparation method, a water-based conductive paint, and a carbon-coated aluminum foil. The preparation method involves homogeneously mixing water, an alcoholizing agent, and a carbon material, followed by an alcoholizing treatment, and then modifying the alcoholized carbon material with a surface modifier to obtain a modified carbon material. The surface modifier includes one or more of a hydroxyalkanoate-based substance or a phosphate ester-based substance. In the present invention, the carbon material is alcoholized to increase the number of hydroxyl groups that can be grafted onto the carbon material's surface, and then the carbon material is modified with the surface modifier. The modified carbon material has a certain affinity for rolling oil. When applied to water-based conductive paints, this works synergistically with the carbon material's high oil absorption properties to open the oil film "blockage," allowing the polar groups in the paint resin to contact the substrate and generate an energizing force, improving adhesion. This further increases the carbon material loading in the water-based conductive paint, thereby reducing the coating layer resistance.

Description

[Technical Field]

[0001] The present invention claims priority from Chinese Patent Application No. 202311692987.3 filed on December 11, 2023 (title: Carbon material and preparation method, water-based conductive paint and carbon-coated aluminum foil). The present invention relates to the technical field of lithium ion batteries, and in particular to a carbon material and preparation method, a water-based conductive paint and a carbon-coated aluminum foil. [Background technology]

[0002] Water-based conductive paints are paints with adhesive and conductive properties. The carbon coating layer formed after film formation is applied to the surface of the positive electrode current collector of a lithium-ion battery, reducing the battery's internal resistance, preventing the positive electrode active material from falling off, and protecting the current collector. Therefore, the core properties of water-based conductive paints are their adhesion to the current collector aluminum foil, their peel strength from the positive electrode active material, their conductivity after film formation, and their resistance to electrolytes.

[0003] As shown in Figure 1, polar groups such as carboxyl groups in the resin components of water-based conductive paints tend to interact with hydroxyl groups on the surface of aluminum foil current collectors, providing theoretically good adhesion. However, aluminum foil current collectors are prone to leaving large amounts of residual rolling oil on their surfaces during the cold rolling process. This rolling oil has very low polarity, forming a molecular-level isolating oil film between the carbon coating layer and the aluminum foil current collector, preventing contact between the coating layer and the polar groups on the aluminum foil, significantly affecting adhesion. Currently, corona treatment or baking treatments are commonly used to temporarily change the polarity of the residual rolling oil or reduce its amount to improve the adhesion of the carbon coating layer. However, these methods have limited effectiveness and are not effective on aluminum foils with heavy oil stains or oil-stained areas.

[0004] Furthermore, as the source of conductivity for water-based conductive paints, the loading amount of the carbon material is an important parameter indicator. Because the carbon material does not adhere to aluminum foil, the higher the loading amount, the higher the conductivity but the lower the adhesion. This limits further improvement of the conductive properties of the carbon coating layer. Therefore, how to overcome the above technical problems and deficiencies has become an important issue to be resolved. Summary of the Invention

[0005] To address the problem of poor adhesion of conventional water-based conductive paints to the surface of aluminum foil, the present invention provides a carbon material and preparation method, a water-based conductive paint, and a carbon-coated aluminum foil.

[0006] In order to solve the above technical problems, the technical means of the present invention are as follows: According to a first aspect of the present invention, there is provided a method for preparing a carbon material, comprising the steps of: Alcoholization treatment of carbon material: Water, alcoholizing agent, and carbon material are mixed uniformly and alcoholized at 150℃-180℃ for 3-5 hours to obtain alcoholized carbon material. Surface modification of carbon materials: The modified carbon materials are obtained by modifying the alcoholized carbon materials with a surface modifier, and the surface modifier includes one or more of hydroxyalkanoate-based substances or phosphate ester-based substances.

[0007] Optionally, in the operation of "uniformly mixing water, the alcoholizing agent, and the carbon material," 50 to 75 parts by weight of the water, 26 to 47 parts by weight of the alcoholizing agent, and 1 to 3 parts by weight of the carbon material are uniformly mixed.

[0008] Optionally, in the operation of "alcoholization treatment of carbon material", the carbon material includes one or more of carbon black, graphite, graphene, and carbon nanotubes, and the alcoholizing agent includes one or more of nitric acid, phosphoric acid, perchloric acid, and sulfuric acid.

[0009] Optionally, in the operation of "surface modification of carbon material", 0.3 to 0.8 parts by weight of the surface modifier is dissolved in a first solvent, and then 4.5 to 7 parts of the alcoholized carbon material is added, and the mixture is ultrasonically treated with stirring for 5 to 20 minutes, and then transferred to a reaction vessel and reacted at 120°C to 160°C for 8 to 12 hours.

[0010] Optionally, in the step of "surface modification of the carbon material", the first solvent includes one or more of carbon tetrachloride, toluene, xylene, butyl ester, ethylene glycol monobutyl ether, propylene glycol methyl ether, propylene glycol butyl ether, propylene glycol methyl ether acetate, and dipropylene glycol methyl ether and dipropylene glycol methyl ether acetate.

[0011] Optionally, the hydroxyalkanoate-based substance includes one or more of methyl 16-hydroxyhexadecanoate, butyl 16-hydroxyhexadecanoate, ethyl 12-hydroxydodecanoate, methyl 3-hydroxyhexadecanoate, methyl hydroxytetradecanoate, and butyl hydroxytetradecanoate, and the phosphate-based substance includes one or more of diphenyl phosphate, xylenyl phosphate, dipentyl phosphate, dibutyl phosphate, dimethyl phosphate, diethyl phosphate, and dipropyl phosphate.

[0012] According to a second aspect of the present invention, there is provided a carbon material prepared by the above-described method for preparing a carbon material.

[0013] According to a third aspect of the present invention, there is provided an aqueous conductive paint comprising, by weight, 35 to 75 parts of water, 15 to 20 parts of a second solvent, 15 to 30 parts of a resin, and 4.5 to 8 parts of the carbon material.

[0014] Optionally, the second solvent includes one or more of ethanol, ethylene glycol monobutyl ether, and ethylene glycol, and the resin includes one or more of acrylic resin, epoxy resin, polyester resin, and polyurethane resin.

[0015] According to a fourth aspect of the present invention, there is provided a carbon-coated aluminum foil comprising a current collector and a coating layer, the coating layer being coated on at least one surface of the current collector, and the coating layer being formed by applying the water-based conductive paint to at least one surface of the current collector.

[0016] According to the method for preparing carbon materials provided by the present invention, the carbon material is first alcoholized to increase the number of hydroxyl groups that can be grafted onto the surface of the carbon material, and then the alcoholized carbon material is surface-modified. Specifically, the carbon material is modified in a solvent phase under high-temperature and high-pressure conditions using a surface modifier. The surface modifier is a low-polarity, low-molecular-weight substance, and since the main component of residual rolling oil is a low-polarity substance such as an alkanoic acid ester, the modified carbon material has a certain affinity with the rolling oil. When applied to an aqueous conductive paint, this surface modifier, combined with the high oil absorption properties of the carbon material, opens the oil film "blockage," allowing polar groups such as carboxyl groups in the paint resin to contact the substrate and generate an energizing force, thereby improving adhesion. Based on the improved adhesion, increasing the loading amount of carbon material when formulating the aqueous conductive paint can improve the conductive performance of the coating layer. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing the effect of the present invention before carbon material treatment. [Figure 2] FIG. 1 is a diagram showing the effect of the present invention after treatment of a carbon material. [Figure 3] FIG. 1 is a graph comparing the adhesion of a carbon coating layer prepared by modifying a carbon material in the present invention with an untreated carbon coating layer to a heavily oil-stained aluminum foil current collector surface. DETAILED DESCRIPTION OF THE INVENTION

[0018] In order to clarify the technical problems, technical means, and beneficial effects of the present invention, the present invention will be described in more detail below with reference to the drawings and examples. Note that the specific examples described in this specification are merely for the purpose of interpreting the present invention and are not intended to limit the present invention. All other examples obtained by those skilled in the art based on the examples of the present invention without any creative efforts are included in the scope of protection of the present invention.

[0019] The test methods used in the following examples are conventional methods unless otherwise specified, and the materials, reagents, etc. used may be commercially available reagents and materials unless otherwise specified.

[0020] In one embodiment, according to a first aspect of the present invention, there is provided a method for preparing a carbon material, comprising the steps of: Alcoholization treatment of carbon material: Water, alcoholizing agent, and carbon material are mixed uniformly and alcoholized at 150℃-180℃ for 3-5 hours to obtain alcoholized carbon material. Surface modification of carbon materials: Modified carbon materials can be obtained by modifying alcoholized carbon materials with a surface modifier, which can include one or more of hydroxyalkanoate-based materials or phosphate-based materials.

[0021] Specifically, the alcoholization treatment of the carbonaceous material includes a pretreatment of the carbonaceous material, which includes ultrasonically cleaning the carbonaceous material in a cleaning agent to remove impurities from the surface of the carbonaceous material, followed by filtering, cleaning, and drying to obtain a clean carbonaceous material, in which the mass ratio of the carbonaceous material to the cleaning agent is 1-10:90-99.

[0022] In a preferred embodiment, the mass ratio of the carbon material to the cleaning agent is 3-8:92-97, for example, any of the following mass ratios: 1:99; 2:98; 3:97; 4:96; 5:95; 6:94; 7:93; 8:92; 9:91 or 10:90.

[0023] Specifically, 5 parts of the carbon material are placed in an ultrasonic cleaning device, 95 parts of a cleaning agent are added, and the mixture is washed for 10 minutes to remove impurities from the surface of the carbon material. The mixture is then suction filtered using a suitable filter cloth, washed with water, and dried in a vacuum oven at 50°C.

[0024] In one embodiment, the cleaning agent is one or more of butanone, acetone, ethyl acetate, ethanol, and butyl acetate.

[0025] The cleaning agent can remove impurities from the surface of the carbon material. Clean carbon material can be obtained by filtering, washing, and drying.

[0026] Specifically, in the process of alcoholizing the carbon material, the water is deionized water or distilled water. Specifically, water, alcoholizing agent, and carbon material are mixed uniformly, then transferred to a reactor and alcoholized at 150-180°C for 3-5 hours. After alcoholizing, the carbon material is taken out, centrifuged, washed, and vacuum-dried at 40-60°C to obtain the alcoholized carbon material.

[0027] In a preferred embodiment, the reaction vessel is a high-pressure reaction vessel, and further, the high-pressure reaction vessel is a polytetrafluoroethylene-lined high-pressure reaction vessel.

[0028] In a preferred embodiment, the temperature of the alcoholization treatment of water, alcoholizing agent and carbon material is 160°C, and the time of the alcoholization treatment is 4 hours.

[0029] In a preferred embodiment, the alcoholized carbon material is vacuum-dried at 50°C. In one embodiment, the surface modifier includes one or more of hydroxyalkanoate-based materials or phosphate-based materials. By modifying the carbon material with hydroxyl long-chain alkanoate ester-based or phosphate ester-based low-polarity low-molecular-weight materials, the modified carbon material has a certain affinity with rolling oil, since the main component of residual rolling oil is a low-polarity material such as alkanoate ester. When applied to water-based conductive paints, the high oil absorption properties of the carbon material are combined to open the oil film "blockage," allowing polar groups such as carboxyl groups in the paint resin to contact the substrate and generate an urging force, thereby improving adhesion. Based on the improved adhesion, increasing the loading amount of carbon material when formulating water-based conductive paints can improve the conductive performance of the coating layer.

[0030] As shown in Figure 1, polar groups such as carboxyl groups in the resin components of water-based conductive paints tend to interact with hydroxyl groups on the surface of aluminum foil current collectors, providing theoretically good adhesion. However, the cold-rolling process of aluminum foil current collectors tends to leave large amounts of rolling oil on the surface. This rolling oil has very low polarity, forming a molecular-level isolating oil film between the carbon coating layer and the aluminum foil current collector, preventing contact between the coating layer and the polar groups on the aluminum foil and significantly affecting adhesion.

[0031] Figure 2 shows the film-forming effect of the water-based conductive paint of the present invention on a current collector surface. In this invention, the carbon material is first alcoholized to increase the number of hydroxyl groups that can be grafted to the carbon material's surface. The alcoholized carbon material is then surface-modified. Specifically, the carbon material is modified in the solvent phase under high-temperature and high-pressure conditions using a surface modifier. The surface modifier is a low-polarity, low-molecular-weight substance. Because the main component of residual rolling oil is a low-polarity substance such as an alkanoic acid ester, the modified carbon material has a certain affinity for rolling oil. By applying this to the water-based conductive paint, the high oil absorption properties of the carbon material are combined to open the "blockage" of the oil film, allowing polar groups such as carboxyl groups in the paint resin to come into contact with the substrate, generating an applied force and improving adhesion.

[0032] In one embodiment, in the step of "uniformly mixing water, an alcoholizing agent, and a carbon material," 50 to 75 parts by weight of water, 26 to 47 parts by weight of the alcoholizing agent, and 1 to 3 parts by weight of the carbon material are uniformly mixed.

[0033] In a preferred embodiment, the water content is 60 to 65 parts, for example, any value selected from 50 parts, 51 parts, 52 parts, 53 parts, 54 parts, 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, 60 parts, 61 parts, 62 parts, 63 parts, 64 parts, 65 parts, 66 parts, 67 parts, 68 parts, 69 parts, 70 parts, 71 parts, 72 parts, 73 parts, 74 parts, and 75 parts, or a range consisting of any two of these values.

[0034] In a preferred embodiment, the alcoholating agent is present in an amount of 30 to 40 parts, for example, any value selected from the group consisting of 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, and 47 parts, or a range consisting of any two of these values.

[0035] In a preferred embodiment, the carbon material is present in an amount of 1.5 to 2.5 parts, for example, any value selected from 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2.0 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.7 parts, 2.8 parts, 2.9 parts, and 3.0 parts, or a range consisting of any two of these values.

[0036] The type and amount of alcohol used in the activation treatment of carbon materials, as well as the temperature and time conditions during the treatment, must be determined experimentally. A vigorous alcoholization process reduces the structural integrity of the carbon material and affects its conductivity, while a too gentle alcoholization process does not generate enough active sites for the reaction. When the water content is 50-75 parts, the alcoholizing agent content is 26-47 parts, and the carbon material content is 1-3 parts, and the alcoholization is performed at 150-180°C for 3-5 hours, the conductive properties of the carbon material are not affected and the number of hydroxyl groups that can be grafted onto the surface of the carbon material is increased, facilitating subsequent modification of the carbon material.

[0037] In one embodiment, in the step of "alcoholizing a carbon material," the carbon material includes one or more of carbon black, graphite, graphene, and carbon nanotubes, and the alcoholizing agent includes one or more of nitric acid, phosphoric acid, perchloric acid, and sulfuric acid.

[0038] Specifically, the carbon black includes conductive carbon black, and the conductive carbon black includes acetylene black and furnace black.

[0039] The graphite may include, but is not limited to, one or more of natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite, and resin-coated graphite. The natural graphite may be scaly graphite, flake graphite, soil graphite, and / or graphite particles obtained by subjecting these graphites to spheroidization, densification, or other processes. The artificial graphite may be obtained by graphitizing organic materials such as coal tar pitch, heavy crude oil from coals, atmospheric residual oil, heavy crude oil from petroleums, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene ether, furfuryl alcohol resin, phenolic resin, and imide resin at high temperatures.

[0040] Specifically, nitric acid, phosphoric acid, perchloric acid, and sulfuric acid can all provide hydroxy groups that can be grafted onto the surface of the carbon material, thereby facilitating subsequent modification of the carbon material.

[0041] In one embodiment, in the "surface modification of carbon material" operation, 0.3 to 0.8 parts by weight of the surface modifier is dissolved in a first solvent, and then 4.5 to 7 parts of the alcoholized carbon material is added. The mixture is ultrasonically treated with stirring for 5 to 20 minutes, and then transferred to a reaction vessel and reacted at 120 to 160°C for 8 to 12 hours.

[0042] In a preferred embodiment, the surface modifier is present in an amount of 0.4 to 0.7 parts, for example, any value selected from the group consisting of 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, or 0.8 parts, or a range consisting of any two of these values.

[0043] In a preferred embodiment, the alcoholized carbonaceous material is 5 to 6 parts, for example, any value selected from 4.5 parts, 4.6 parts, 4.7 parts, 4.8 parts, 4.9 parts, 5.0 parts, 5.1 parts, 5.2 parts, 5.3 parts, 5.4 parts, 5.5 parts, 5.6 parts, 5.7 parts, 5.8 parts, 5.9 parts, 6.0 parts, 6.1 parts, 6.2 parts, 6.3 parts, 6.4 parts, 6.5 parts, 6.6 parts, 6.7 parts, 6.8 parts, 6.9 parts, and 7.0 parts, or a range consisting of any two of these values.

[0044] Specifically, in the process of modifying the alcoholized carbon material with the surface modifier, the surface modifier is dissolved in a first solvent, and then the alcoholized carbon material is added and ultrasonically treated for 10 minutes while stirring at 600 rpm. The mixture is then transferred to a reactor and reacted at 120 to 160°C for 8 to 12 hours. The mixture is then removed, filtered, washed with chloroform, and dried in a vacuum oven at 80°C to obtain the modified carbon material.

[0045] In a preferred embodiment, the heating temperature is 130°C to 150°C, for example, any value selected from 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C, 130°C, 131°C, 132°C, 133°C, 134°C, 135°C, 136°C, 137°C, 138°C, 139°C, 140°C, 141°C, 142°C, 143°C, 144°C, 145°C, 146°C, 147°C, 148°C, 149°C, 150°C, 151°C, 152°C, 153°C, 154°C, 155°C, 156°C, 157°C, 158°C, 159°C, and 160°C, or a range consisting of any two of these values.

[0046] In a preferred embodiment, the reaction time is 9-11 hours, for example, any value among 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, or 12 hours, or a range consisting of any two of these values.

[0047] In one embodiment, in the step of "surface modification of carbon material", the first solvent comprises one or more of carbon tetrachloride, toluene, xylene, butyl ester, ethylene glycol monobutyl ether, propylene glycol methyl ether, propylene glycol butyl ether, propylene glycol methyl ether acetate, dipropylene glycol methyl ether, and dipropylene glycol methyl ether acetate.

[0048] In one embodiment, the hydroxyalkanoate-based material includes one or more of methyl 16-hydroxyhexadecanoate, butyl 16-hydroxyhexadecanoate, ethyl 12-hydroxydodecanoate, methyl 3-hydroxyhexadecanoate, methyl hydroxytetradecanoate, and butyl hydroxytetradecanoate, and the phosphate-based material includes one or more of diphenyl phosphate, xylenyl phosphate, dipentyl phosphate, dibutyl phosphate, dimethyl phosphate, diethyl phosphate, and dipropyl phosphate.

[0049] Specifically, methyl 16-hydroxyhexadecanoate, butyl 16-hydroxyhexadecanoate, ethyl 12-hydroxydodecanoate, methyl 3-hydroxyhexadecanoate, methyl hydroxytetradecanoate, and butyl hydroxytetradecanoate are hydroxyl long-chain alkanoate esters, while diphenyl phosphate, xylenyl phosphate, dipentyl phosphate, dibutyl phosphate, dimethyl phosphate, diethyl phosphate, and dipropyl phosphate are phosphate ester-based low-polarity low-molecular-weight substances. By modifying carbon materials with hydroxyl long-chain alkanoate esters and phosphate ester-based low-polarity low-molecular-weight substances, the modified carbon materials have a certain affinity with rolling oil, since the main component of residual rolling oil is a low-polarity substance such as an alkanoate ester. When applied to water-based conductive paints, the high oil absorption properties of the carbon materials are combined to open the oil film, allowing polar groups such as carboxyl groups in the paint resin to contact the substrate and generate an activating force, thereby improving adhesion. Based on the improved adhesion, the conductive performance of the coating layer can be improved by increasing the loading amount of carbon material when formulating the water-based conductive paint.

[0050] According to a second aspect of the present invention, there is provided a carbon material prepared by the above-described method for preparing a carbon material.

[0051] In the present invention, the modified carbon material has a certain affinity for rolling oil. By applying it to the water-based conductive paint, the high oil absorption property of the carbon material is combined with the "blockage" of the oil film, allowing polar groups such as carboxyl groups in the paint resin to come into contact with the substrate and generate an urging force, thereby improving adhesion.

[0052] According to a third aspect of the present invention, there is provided an aqueous conductive paint, which is obtained by uniformly mixing, by weight, 35 to 75 parts of water, 15 to 20 parts of a second solvent, 15 to 30 parts of a resin, and 4.5 to 8 parts of the carbon material, and then dispersing the mixture to a fineness of 10 to 25 using a sand mill.

[0053] Preferably, the fineness of the paint is 10 to 25, the viscosity is 30 to 1000 mPa·S, and the solid content of the paint is 5 to 15%.

[0054] In a preferred embodiment, the water content is 40 to 70 parts, for example, any value selected from the group consisting of 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 ​​parts, 49 parts, 50 parts, 51 parts, 52 parts, 53 parts, 54 parts, 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, 60 parts, 61 parts, 62 parts, 63 parts, 64 parts, 65 parts, 66 parts, 67 parts, 68 parts, 69 parts, 70 parts, 71 parts, 72 parts, 73 parts, 74 parts, and 75 parts, or a range consisting of any two of these values.

[0055] In a preferred embodiment, the second solvent is present in an amount of 16 to 18 parts, for example, any value selected from the group consisting of 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, or 20 parts, or a range consisting of any two of these values.

[0056] In a preferred embodiment, the resin is present in an amount of 20 to 25 parts, for example, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 parts, or a range consisting of any two of these values.

[0057] In a preferred embodiment, the carbon material is present in an amount of 5 to 8 parts, for example, 4.5 parts, 5.0 parts, 5.5 parts, 6.0 parts, 6.5 parts, 7.0 parts, 7.5 parts, or 8.0 parts, or a range consisting of any two of these values.

[0058] In the present invention, the modified carbon material is applied to an aqueous conductive paint, and based on the principle that "like dissolves like," the high oil absorption properties of the carbon material are utilized synergistically to break down the oil film, allowing groups such as carboxyl groups in the paint resin to come into contact with the substrate, improving adhesion.

[0059] Based on the improvement in adhesion, the conductive performance of the coating layer can be improved by increasing the carbon loading when formulating a water-based conductive paint. For example, increasing the carbon loading from 55% to 70% reduces the resistance by approximately 50%.

[0060] In one embodiment, the second solvent includes one or more of ethanol, ethylene glycol monobutyl ether, and ethylene glycol, and the resin includes one or more of acrylic resin, epoxy resin, polyester resin, and polyurethane resin.

[0061] According to a fourth aspect of the present invention, there is provided a carbon-coated aluminum foil comprising a current collector and a coating layer, the coating layer being coated on at least one surface of the current collector, and the coating layer being formed by applying the above-mentioned water-based conductive paint to at least one surface of the current collector.

[0062] The coating layer on the carbon-coated aluminum foil of the present invention is formed by applying an aqueous conductive paint to at least one surface of a current collector. The aqueous conductive paint of the present invention uses a modified carbon material. By applying the modified carbon material to the aqueous conductive paint, based on the principle that "like dissolves like," the high oil absorption properties of the carbon material are synergistically utilized, disrupting the oil film and allowing groups such as carboxyl groups in the paint resin to come into contact with the substrate, improving adhesion. Based on the improved adhesion, the conductive performance of the coating layer can be improved by increasing the carbon material loading when formulating the aqueous conductive paint. For example, increasing the carbon material loading from 55% to 70% reduces resistance by approximately 50%. This not only reduces substrate processing costs, but also improves the application adaptability of the aqueous conductive paint. Further increasing the carbon material loading reduces resistance, which is highly beneficial for improving the overall performance of lithium-ion batteries.

[0063] In one embodiment, the thickness of the coating layer of the carbon-coated aluminum foil is 0.3 to 2 μm.

[0064] In a preferred embodiment, the thickness of the coating layer of the carbon-coated aluminum foil is 0.5 to 1.5 μm, for example, any value selected from the group consisting of 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, and 2.0 μm, or a range consisting of any two of these values.

[0065] The present invention will now be further described with reference to examples.

[0066] Example 1 1. Alcoholization treatment of carbon materials 1) 5 parts of carbon material was ultrasonically cleaned in 95 parts of butanone for 10 minutes to remove impurities on the surface of the carbon material, and then the carbon material was suction filtered using an appropriate filter cloth, washed with deionized water, and dried in a vacuum oven at 50°C. 2) 57 parts of deionized water, 40 parts of dilute nitric acid, 1 part of phosphoric acid, and 2 parts of acetylene carbon black were mixed in this order and stirred uniformly, then transferred to a high-pressure reactor lined with polytetrafluoroethylene and subjected to alcoholization treatment at 160°C for 4 hours. After removing the mixture, centrifuging it, washing it with deionized water, and drying it under vacuum at 50°C, an alcoholized carbon material was obtained.

[0067] 2. Surface modification of carbon materials 0.78 parts of ethyl 12-hydroxydodecanoate was dissolved in toluene, and then 7 parts of the alcoholized carbon material was added. The mixture was ultrasonically treated for 10 minutes while stirring at 600 rpm, and then transferred to a reactor and reacted at 120°C for 10 hours. The mixture was then removed, filtered, washed with chloroform, and dried in a vacuum oven at 80°C to obtain an alkanoate ester-modified carbon material.

[0068] 3. Preparation of the positive electrode, aqueous carbon-coated aluminum foil 48.89 parts of deionized water, 20 parts of solvent, 25 parts of resin, and 6.11 parts of alkanoate ester-modified carbon material were mixed uniformly, and then dispersed to a fineness of 15 using a sand mill, resulting in an aqueous conductive paint with a carbon material loading of 55%. The paint was applied to both sides of a current collector aluminum foil and baked in a hot air oven at 125°C for 30 seconds to obtain a carbon-coated aluminum foil. The thickness of the single-sided coating layer was 0.5 μm and is designated S1.

[0069] Example 2 Example 2 is intended to illustrate the carbon material and preparation method, water-based conductive paint, and carbon-coated aluminum foil disclosed in the present invention, and the operating procedure is almost the same as that of Example 1, except for the following points. Preparation of positive electrode aqueous carbon-coated aluminum foil 51.12 parts of deionized water, 20 parts of solvent, 22.22 parts of resin, and 6.66 parts of alkanoate ester-modified carbon material were mixed uniformly in this order, and then dispersed to a fineness of 15 in a sand mill to obtain a water-based conductive paint with a carbon material loading of 60%. The paint was applied to both sides of a current collector aluminum foil and baked in a hot air oven at 125°C for 30 seconds to obtain a carbon-coated aluminum foil. The thickness of the coating layer on one side was 0.5 μm and is designated S2.

[0070] Example 3 Example 3 is intended to illustrate the carbon material and preparation method, water-based conductive paint, and carbon-coated aluminum foil disclosed in the present invention, and the operating procedure is almost the same as that of Example 1, except for the following points. Preparation of positive electrode aqueous carbon-coated aluminum foil 53.34 parts of deionized water, 20 parts of solvent, 19.44 parts of resin, and 7.22 parts of alkanoate ester-modified carbon material were mixed uniformly, and then dispersed in a sand mill to a fineness of 15, resulting in an aqueous conductive paint with a carbon material loading of 65%. The paint was applied to both sides of a current collector aluminum foil and baked in a hot air oven at 125°C for 30 seconds to obtain a carbon-coated aluminum foil. The thickness of the single-sided coating layer was 0.5 μm and is designated S3.

[0071] Example 4 Example 4 is intended to illustrate the carbon material and preparation method, water-based conductive paint, and carbon-coated aluminum foil disclosed in the present invention, and the operating procedure is almost the same as that of Example 1, except for the following points. Preparation of positive electrode aqueous carbon-coated aluminum foil 55.55 parts of deionized water, 20 parts of solvent, 16.67 parts of resin, and 7.78 parts of alkanoate ester-modified carbon material were mixed uniformly, and then dispersed to a fineness of 15 using a sand mill, resulting in an aqueous conductive paint with a carbon material loading of 70%. The paint was applied to both sides of a current collector aluminum foil and baked in a hot air oven at 125°C for 30 seconds to obtain a carbon-coated aluminum foil. The thickness of the single-sided coating layer was 0.5 μm and is designated S4.

[0072] Comparative Example 1 Comparative Example 1 is intended to illustrate the carbon material and preparation method, water-based conductive paint, and carbon-coated aluminum foil disclosed in the present invention, and is almost the same as the operating procedure of Example 1, except for the following points. Without alcoholization treatment of the carbon material, an aqueous conductive paint with a carbon material loading of 55% was prepared and fired to obtain a carbon-coated aluminum foil (denoted as X1).

[0073] Comparative Example 2 Comparative Example 2 is intended to illustrate the carbon material and preparation method, water-based conductive paint, and carbon-coated aluminum foil disclosed in the present invention, and is almost the same as the operating procedure of Example 1, except for the following points. Without alcoholization treatment of the carbon material, an aqueous conductive paint with a carbon material loading of 70% was prepared and fired to obtain a carbon-coated aluminum foil (denoted as X2).

[0074] Comparative Example 3 Comparative Example 3 is intended to illustrate the carbon material and preparation method, water-based conductive paint, and carbon-coated aluminum foil disclosed in the present invention, and is almost the same as the operating procedure of Example 1, except for the following points. Without surface modification of the carbon material, an aqueous conductive paint with a carbon material loading of 55% was prepared and fired to obtain a carbon-coated aluminum foil (denoted as X3).

[0075] Comparative Example 4 Comparative Example 4 is intended to illustrate the carbon material and preparation method, water-based conductive paint, and carbon-coated aluminum foil disclosed in the present invention, and is almost the same as the operating procedure of Example 1, except for the following points. Without surface modification of the carbon material, an aqueous conductive paint with a carbon material loading of 70% was prepared and fired to obtain a carbon-coated aluminum foil (denoted as X4).

[0076] Comparative Example 5 Comparative Example 5 is intended to illustrate the carbon material and preparation method, water-based conductive paint, and carbon-coated aluminum foil disclosed in the present invention, and is almost the same as the operating procedure of Example 1, except for the following points. Without any carbon material treatment, a water-based conductive paint with a carbon material loading of 55% was prepared and fired to obtain a carbon-coated aluminum foil (denoted as X5).

[0077] Comparative Example 6 Comparative Example 6 is intended to illustrate the carbon material and preparation method, water-based conductive paint, and carbon-coated aluminum foil disclosed in the present invention, and is almost the same as the operating procedure of Example 1, except for the following points. Without any carbon material treatment, a water-based conductive paint with a carbon material loading of 70% was prepared and fired to obtain a carbon-coated aluminum foil (denoted as X6).

[0078] Performance Test (1) Adhesion test The carbon-coated aluminum foils prepared in Examples 1-4 and Comparative Examples 1-6 were peeled off using 3M tape to evaluate the degree of peeling. Test method: Place the carbon-coated aluminum foil with the coating side facing up, apply 3M tape to the coating, and flatten the 3M tape on the coating with your fingers to remove any air bubbles between the 3M tape and the coating, ensuring maximum adhesion of the 3M tape to the coating. Lift the 3M tape vertically from the bottom and record the degree of coating shedding.

[0079] (2) Conductivity test The carbon-coated aluminum foils prepared in Examples 1-4 and Comparative Examples 1-6 are tested for resistance, respectively. The test equipment is a sheet resistance test system (Chuanyuan Technology TT-ACCF-G2A), the test pressure is 23 MPa, and the pressure holding time is 5 seconds. Three test values ​​are obtained for each carbon-coated aluminum foil, and the average value is used as the result.

[0080] Table 1 shows the test results obtained in Examples 1 to 4 and Comparative Examples 1 to 6.

[0081] [Table 1]

[0082] Some of the adhesion test results are shown in Figure 3. From left to right, they are X5, X6, and S4, respectively.

[0083] As can be seen from the test results in Table 1, in Examples 1-4 of the present invention, long-chain alkanoic acid ester or phosphate ester-based low-molecular-weight materials, whose structure is similar to that of the substrate's residual rolling oil, were used as grafts to modify the carbon material surface through a thermal reaction in a high-pressure solvent. The modified carbon material was then applied to a water-based conductive paint, leveraging the high oil absorption properties of the carbon material based on the principle that "like dissolves well." This disrupts the oil film, allowing groups such as carboxyl groups in the paint resin to come into contact with the substrate, improving adhesion. Figures 1 and 2 analyze the mechanism behind the improvement in adhesion, and Figure 3 shows the adhesion of the coating layer before (X6) and after (S4) treatment with the carbon material, demonstrating a significant improvement in adhesion. Based on the improvement in adhesion, the conductive performance of the coating layer can be improved by increasing the carbon loading when formulating a water-based conductive paint. For example, increasing the carbon loading from 55% to 70% reduces the resistance by approximately 50%.

[0084] The above are only preferred embodiments of the present invention, and do not limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included within the protection scope of the present invention. [Explanation of symbols]

[0085] 1 carbon coating layer, 11. energizing groups in resins; 12. A group that is grafted onto the surface of a carbon material; 2 positive electrode current collector, 21 biasing groups in the substrate; 3 Residual rolling oil

Claims

1. 1. A method for preparing a carbon material, comprising the steps of: Alcoholization treatment of carbon material: Water, an alcoholizing agent, and a carbon material are uniformly mixed, and the mixture is subjected to alcoholization treatment at 150°C-180°C for 3-5 hours to obtain an alcoholized carbon material. Surface modification of carbon material: A method for preparing a carbon material, comprising modifying an alcoholized carbon material with a surface modifier to obtain a modified carbon material, the surface modifier comprising one or more of a hydroxyalkanoate-based substance or a phosphate ester-based substance.

2. 2. The method for preparing a carbon material according to claim 1, wherein in the operation of "uniformly mixing water, the alcoholizing agent, and the carbon material," 50 to 75 parts of the water, 26 to 47 parts of the alcoholizing agent, and 1 to 3 parts of the carbon material are uniformly mixed, in parts by weight.

3. 2. The method for preparing a carbon material according to claim 1, wherein in the operation of "alcoholization treatment of a carbon material," the carbon material includes one or more of carbon black, graphite, graphene, and carbon nanotubes, and the alcoholizing agent includes one or more of nitric acid, phosphoric acid, perchloric acid, and sulfuric acid.

4. The method for preparing a carbon material according to claim 1, wherein in the operation of "surface modification of the carbon material", 0.3 to 0.8 parts by weight of the surface modifier is dissolved in a first solvent, and then 4.5 to 7 parts of the alcoholized carbon material is added, followed by ultrasonic treatment with stirring for 5 to 20 minutes, and then transferring to a reaction vessel and reacting at 120°C to 160°C for 8 to 12 hours.

5. 5. The method for preparing a carbon material according to claim 4, wherein in the step of "surface modification of the carbon material", the first solvent comprises one or more of carbon tetrachloride, toluene, xylene, butyl ester, ethylene glycol monobutyl ether, propylene glycol methyl ether, propylene glycol butyl ether, propylene glycol methyl ether acetate, dipropylene glycol methyl ether, and dipropylene glycol methyl ether acetate.

6. 2. The method for preparing a carbon material according to claim 1, wherein the hydroxyalkanoate-based substance comprises one or more of methyl 16-hydroxyhexadecanoate, butyl 16-hydroxyhexadecanoate, ethyl 12-hydroxydodecanoate, methyl 3-hydroxyhexadecanoate, methyl hydroxytetradecanoate, and butyl hydroxytetradecanoate, and the phosphate ester-based substance comprises one or more of diphenyl phosphate, xylenyl phosphate, dipentyl phosphate, dibutyl phosphate, dimethyl phosphate, diethyl phosphate, and dipropyl phosphate.

7. A carbon material prepared by the method for preparing a carbon material according to any one of claims 1 to 6.

8. An aqueous conductive paint comprising, by weight, 35 to 75 parts of water, 15 to 20 parts of a second solvent, 15 to 30 parts of a resin, and 4.5 to 8 parts of the carbon material according to claim 7.

9. 9. The water-based conductive paint according to claim 8, wherein the second solvent comprises one or more of ethanol, ethylene glycol monobutyl ether, and ethylene glycol, and the resin comprises one or more of an acrylic resin, an epoxy resin, a polyester resin, and a polyurethane resin.

10. 10. A carbon-coated aluminum foil comprising: a current collector; and a coating layer, the coating layer being coated on at least one surface of the current collector, the coating layer being formed by coating the water-based conductive paint according to claim 8 or 9 on at least one surface of the current collector.

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