Preparation method of water-resistant carbon coating slurry for lithium battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of water-resistant carbon coating slurry for a lithium battery. According to the invention, methyl cyclohexane diisocyanate, hydroxyethyl methylacrylate, n-dodecanethiol, a surfactant fatty alcohol-polyoxyethylene ether, octadecyl acrylate and a cross-linking monomer N-hydroxymethyl acrylamide are used to prepare an acrylic resin emulsion as a carbon-coated slurry base material, and compared with a common polyacrylic acid binder, the acrylic resin emulsion has the advantages that the viscosity is high; the prepared acrylic resin emulsion has more excellent water resistance, and the problems of stripping, electrolyte leakage and the like caused by the fact that an electrode material easily absorbs water or is decomposed in a high-humidity or liquid contact environment can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, in particular to a method for preparing a water-resistant carbon coating slurry for lithium batteries. Background Art

[0002] With the widespread application of lithium batteries in electronic devices, electric vehicles and other fields, the requirements for battery performance are increasing. Among them, the stability and durability of the carbon-coated aluminum foil structure inside the battery is one of the important factors affecting battery performance. The carbon coating layer on the carbon-coated aluminum foil is made by coating the aluminum foil with a carbon coating slurry and baking it, so the carbon coating slurry plays a key role in maintaining the stability of the internal component structure of the battery. However, under some special environmental conditions, such as high humidity or liquid contact environments, the carbon coating layer formed by traditional carbon coating slurry is not water resistant enough. It is easy to absorb water or decompose in high humidity or liquid contact environments, resulting in problems such as peeling of electrode materials and leakage of electrolyte, thereby reducing the performance and life of the battery.

[0003] In order to solve the above problems and improve the water resistance of carbon coating slurry for lithium batteries, the present invention provides a preparation method of water-resistant carbon coating slurry for lithium batteries. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing a water-resistant carbon coating slurry for lithium batteries to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing a water-resistant carbon coating slurry for lithium batteries comprises the following steps:

[0007] Step 1: Take methylcyclohexyl diisocyanate and hydroxyethyl methacrylate, stir and mix for 15-40 minutes, heat to 60-90°C and react for 1-4 hours, then cool to 30-50°C, add butanone oxime, mix evenly, heat to 60-80°C and react for 2-4 hours to prepare a monomer;

[0008] Step 2: dissolving octadecyltrimethylammonium chloride, fatty alcohol polyoxyethylene ether, and N-hydroxymethyl acrylamide in pure water, adding octadecyl acrylate, isobornyl methacrylate, monomer, n-dodecyl mercaptan, and dipropylene glycol dimethyl ether, mixing evenly, and emulsifying to obtain an emulsion; taking the emulsion and an initiator azobisisobutylamidine hydrochloride, reacting under nitrogen protection at 50-80° C. for 5-9 hours to obtain an acrylic resin emulsion;

[0009] Step 3: Take acrylic resin emulsion, deionized water, conductive agent, and wetting agent, stir and disperse them to prepare a water-resistant carbon coating slurry for lithium batteries.

[0010] More optimally, in step three, the stirring and dispersing time is 0.5-2h, and the dispersing speed is 500-1500RPM.

[0011] More optimally, the carbon coating slurry includes the following components, calculated by weight: 10-60 parts of acrylic resin emulsion, 10-30 parts of deionized water, 2-30 parts of conductive agent, and 0.1-6 parts of wetting agent.

[0012] More optimally, the wetting agent is selected from any one or more of n-pentanol, ethanol, methanol, and isopropanol.

[0013] More optimally, the conductive agent is any one or more of acetylene black, natural graphite, and artificial graphite.

[0014] More optimally, the acrylic resin emulsion includes the following components, calculated in parts by mass: the acrylic resin emulsion includes the following components, calculated in parts by mass: 3-5 parts of methylcyclohexane diisocyanate, 1-3 parts of hydroxyethyl methacrylate, 0.01-0.5 parts of butanone oxime, 0.01-0.5 parts of octadecyltrimethylammonium chloride, 0.1-0.6 parts of fatty alcohol polyoxyethylene ether, 1-3 parts of N-hydroxymethyl acrylamide, 20-30 parts of octadecyl acrylate, 5-10 parts of isobornyl methacrylate, 0.01-0.4 parts of n-dodecyl mercaptan, 5-10 parts of dipropylene glycol dimethyl ether, and 0.01-4 parts of azobisisobutylamidine hydrochloride initiator.

[0015] More optimally, the conductive agent is graphene oxide coated with polyaniline, and the preparation method is: take graphene oxide and hydrochloric acid solution, ultrasonically disperse, add sulfosalicylic acid and deionized water, stir evenly, add sodium dodecylbenzenesulfonate, stir evenly to obtain a mixed solution; take aniline and ethylbenzene, stir evenly, add the mixed solution, emulsify for 4-5 minutes, add polyvinyl alcohol and stir evenly, add ammonium persulfate, react for 22-26 hours, wash, and dry to obtain graphene oxide coated with polyaniline.

[0016] More optimally, the water-resistant carbon coating slurry for lithium battery further contains epoxy hyperbranched products, and the preparation method of the epoxy hyperbranched products comprises the following steps:

[0017] S1: Take diethanolamine and anhydrous methanol, stir evenly, add methyl acrylate dropwise under nitrogen atmosphere, heat to 33-35°C, react for 4-5 hours, rotary evaporate, extract, and obtain compound monomer; take trimethylolpropane and p-toluenesulfonic acid, heat to 105-110°C, add compound monomer dropwise, heat to 120-125°C, stir for 4.5-5.5 hours, rotary evaporate at 95-105°C until bubbling stops, extract, and rotary evaporate to obtain hydroxyl hyperbranched product;

[0018] S2: Take hydroxyl hyperbranched product and N,N-dimethylformamide, stir evenly, add boron trifluoride etherate, stir, add epichlorohydrin dropwise, heat to 60-65°C, keep warm for 2-3 hours, rotary evaporate, add sodium hydroxide aqueous solution dropwise, heat to 75-85°C, react for 3-4 hours, rotary evaporate, filter, and centrifuge to obtain epoxy hyperbranched product.

[0019] More optimally, the following steps are included:

[0020] Step 1: Take methylcyclohexyl diisocyanate and hydroxyethyl methacrylate, stir and mix for 15-40 minutes, heat to 60-90°C and react for 1-4 hours, then cool to 30-50°C, add butanone oxime, mix well, heat to 60-80°C and react for 2-4 hours to obtain a monomer;

[0021] Step 2: dissolving octadecyltrimethylammonium chloride, fatty alcohol polyoxyethylene ether, and N-hydroxymethyl acrylamide in pure water, adding octadecyl acrylate, isobornyl methacrylate, monomer, n-dodecyl mercaptan, and dipropylene glycol dimethyl ether, mixing evenly, and emulsifying to obtain an emulsion; taking the emulsion and an initiator azobisisobutylamidine hydrochloride, reacting under nitrogen protection at 50-80° C. for 5-9 hours to obtain an acrylic resin emulsion;

[0022] Step 3: Take acrylic resin emulsion, deionized water, polyaniline-coated graphene oxide, epoxy hyperbranched product, and wetting agent, stir and disperse them to prepare a water-resistant carbon coating slurry for lithium batteries.

[0023] More optimally, the carbon coating slurry comprises the following components, calculated by weight: 10-60 parts of acrylic resin emulsion, 10-30 parts of deionized water, 2-30 parts of polyaniline-coated graphene oxide, 3-5 parts of epoxy hyperbranched product, and 0.1-6 parts of wetting agent.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention uses methylcyclohexane diisocyanate, hydroxyethyl methacrylate, n-dodecyl mercaptan, surfactant fatty alcohol polyoxyethylene ether, octadecyl acrylate, and cross-linking monomer N-hydroxymethyl acrylamide to prepare an acrylic resin emulsion as a carbon coating slurry matrix material. Compared with ordinary polyacrylic acid binders, the acrylic resin emulsion prepared by the present invention has better water resistance and can improve the problems of peeling, electrolyte leakage, etc. caused by the easy water absorption or decomposition of electrode materials in high humidity or liquid contact environments.

[0026] (2) The present invention uses sodium dodecylbenzenesulfonate as a surfactant to prepare a polyaniline with good hydrophobicity, and then coats the polyaniline on graphene oxide, thereby improving the hydrophobicity of the graphene oxide. Adding the polyaniline-coated graphene oxide as a conductive material to the carbon coating slurry can further enhance the water resistance of the carbon coating slurry.

[0027] (3) The present invention also prepares an epoxy hyperbranched compound, and the epoxy groups on the epoxy hyperbranched compound can react with the amino groups on the polyaniline-coated graphene oxide, and the two are cross-linked with each other, thereby further enhancing the water resistance of the carbon-coated slurry and the mechanical properties of the current collector. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0029] There are no special restrictions on the purchasing manufacturers of all raw materials involved in the present invention, and illustratively include: graphene powder: particle size: 5-10 μm; graphene oxide: flake diameter is 2 μm; aluminum sheet: item number lp123tt, which can be purchased from Flex Insulation Building Materials; polyacrylic acid adhesive: can be purchased from Sanying New Materials, model SY-302.

[0030] Example 1: A method for preparing a water-resistant carbon coating slurry for lithium batteries, comprising the following steps:

[0031] Step 1: Take 3.4 kg of methylcyclohexyl diisocyanate and 1.2 kg of hydroxyethyl methacrylate, stir and mix for 30 minutes, heat to 80 ° C and react for 3 hours, then cool to 40 ° C, add 0.1 kg of butanone oxime, mix well, heat to 70 ° C and react for 3 hours to obtain a monomer;

[0032] Step 2: dissolving 0.2 kg of octadecyltrimethylammonium chloride, 0.26 kg of fatty alcohol polyoxyethylene ether, and 1.2 kg of N-hydroxymethyl acrylamide in 60 kg of pure water, adding 22 kg of octadecyl acrylate, 7 kg of isobornyl methacrylate, the monomer prepared in step 1, 0.05 kg of n-dodecyl mercaptan, and 6 kg of dipropylene glycol dimethyl ether, mixing evenly, and emulsifying with a high-pressure homogenizer to obtain an emulsion; adding the emulsion and 0.06 kg of azobisisobutylamidine hydrochloride initiator to a reaction tank, reacting at 70 ° C for 8 hours under nitrogen protection, to obtain an acrylic resin emulsion;

[0033] Step 3: Take 1 kg of graphene and 2 kg of deionized water, ultrasonically disperse them to obtain a graphene solution; take 8 kg of acrylic resin emulsion, add deionized water to dilute it to 25% solid content, add 3 kg of graphene solution, add deionized water to dilute it to 10% solid content, stir and disperse for 1 hour, the dispersion speed is 1000 RPM, add 2 kg of n-pentanol, mix and disperse, and obtain a water-resistant carbon slurry for lithium batteries.

[0034] Example 2: A method for preparing a water-resistant carbon coating slurry for lithium batteries, comprising the following steps:

[0035] Step 1: Take 3.4 kg of methylcyclohexyl diisocyanate and 1.2 kg of hydroxyethyl methacrylate, stir and mix for 30 minutes, heat to 80 ° C and react for 3 hours, then cool to 40 ° C, add 0.1 kg of butanone oxime, mix well, heat to 70 ° C and react for 3 hours to obtain a monomer;

[0036] Step 2: dissolving 0.2 kg of octadecyltrimethylammonium chloride, 0.26 kg of fatty alcohol polyoxyethylene ether, and 1.2 kg of N-hydroxymethyl acrylamide in 60 kg of pure water, adding 22 kg of octadecyl acrylate, 7 kg of isobornyl methacrylate, the monomer prepared in step 1, 0.05 kg of n-dodecyl mercaptan, and 6 kg of dipropylene glycol dimethyl ether, mixing evenly, and emulsifying with a high-pressure homogenizer to obtain an emulsion; adding the emulsion and 0.06 kg of azobisisobutylamidine hydrochloride initiator to a reaction tank, reacting at 70 ° C for 8 hours under nitrogen protection, to obtain an acrylic resin emulsion;

[0037] Step 3: Preparation of epoxy hyperbranched compounds:

[0038] Take 11g of diethanolamine and 10mL of anhydrous methanol, stir evenly, add 13g of methyl acrylate dropwise under a nitrogen environment, heat to 34°C, react for 4.5h, rotary evaporate, and extract to obtain a compound monomer; take 13.5g of trimethylolpropane and 0.2g of p-toluenesulfonic acid, heat to 108°C, add the compound monomer dropwise, heat to 122°C, stir for 5h, rotary evaporate at 100°C until bubbling stops, extract, and rotary evaporate to obtain a hydroxyl hyperbranched product;

[0039] Take 0.02 mol of hydroxy hyperbranched product and 0.04 mol of N,N-dimethylformamide, stir evenly, add 0.2 g of boron trifluoride etherate, stir, add 0.5 mol of epichlorohydrin dropwise, heat to 63°C, keep warm for 2.5 hours, evaporate by rotary evaporation, add 0.3 mol of 25% sodium hydroxide aqueous solution dropwise, heat to 80°C, react for 3.5 hours, evaporate by rotary evaporation, filter, and centrifuge to obtain epoxy hyperbranched product;

[0040] Step 4: Preparation of polyaniline-coated graphene oxide:

[0041] Take 100 mg of graphene oxide and 200 mL of 1 mol / L hydrochloric acid solution, ultrasonically disperse, add 0.5 mmol of sulfosalicylic acid and 20 mL of deionized water, stir evenly, add 150 mg of sodium dodecylbenzenesulfonate, stir evenly to obtain a mixed solution; take 2 mmol of aniline and 1.5 mmol of ethylbenzene, stir evenly, add the mixed solution, emulsify for 4.5 minutes, add 15 mL of polyvinyl alcohol and stir evenly, add 2 mmol of ammonium persulfate, react for 24 hours, wash and dry to obtain graphene oxide coated with polyaniline;

[0042] Step 5: Take 1 kg of polyaniline-coated graphene oxide and 2 kg of deionized water, ultrasonically disperse them to obtain a graphene solution; take 8 kg of acrylic resin emulsion and 2 kg of epoxy hyperbranched product, add deionized water to dilute to 25% solid content, add 3 kg of graphene solution, add deionized water to dilute to 10% solid content, stir and disperse for 0.8 h, the dispersion speed is 1000 RPM, add 2 kg of n-pentanol, mix and disperse to obtain a water-resistant carbon slurry for lithium batteries.

[0043] Example 3: A method for preparing a water-resistant carbon coating slurry for lithium batteries, comprising the following steps:

[0044] Step 1: Take 3.4 kg of methylcyclohexyl diisocyanate and 1.2 kg of hydroxyethyl methacrylate, stir and mix for 15 minutes, heat to 60 ° C and react for 1 hour, then cool to 30 ° C, add 0.1 kg of butanone oxime, mix well, heat to 60 ° C and react for 2 hours to obtain a monomer;

[0045] Step 2: dissolving 0.2 kg of octadecyltrimethylammonium chloride, 0.26 kg of fatty alcohol polyoxyethylene ether, and 1.2 kg of N-hydroxymethyl acrylamide in 60 kg of pure water, adding 22 kg of octadecyl acrylate, 7 kg of isobornyl methacrylate, the monomer prepared in step 1, 0.05 kg of n-dodecyl mercaptan, and 6 kg of dipropylene glycol dimethyl ether, mixing evenly, and emulsifying with a high-pressure homogenizer to obtain an emulsion; adding the emulsion and 0.06 kg of azobisisobutylamidine hydrochloride initiator to a reaction tank, reacting at 50 ° C for 5 hours under nitrogen protection, to obtain an acrylic resin emulsion;

[0046] Step 3: Preparation of epoxy hyperbranched compounds:

[0047] Take 11g of diethanolamine and 10mL of anhydrous methanol, stir evenly, add 13g of methyl acrylate dropwise under a nitrogen environment, heat to 33°C, react for 4h, rotary evaporate, and extract to obtain a compound monomer; take 13.5g of trimethylolpropane and 0.2g of p-toluenesulfonic acid, heat to 105°C, add the compound monomer dropwise, heat to 120°C, stir for 4.5h, rotary evaporate at 95°C until no bubbling occurs, extract, and rotary evaporate to obtain a hydroxyl hyperbranched product;

[0048] Take 0.02 mol of hydroxyl hyperbranched product and 0.04 mol of N,N-dimethylformamide, stir evenly, add 0.2 g of boron trifluoride etherate, stir, add 0.5 mol of epichlorohydrin dropwise, heat to 60°C, keep warm for 2 hours, rotary evaporate, add 0.3 mol of 25% sodium hydroxide aqueous solution dropwise, heat to 75°C, react for 3 hours, rotary evaporate, filter, and centrifuge to obtain epoxy hyperbranched product;

[0049] Step 4: Preparation of polyaniline-coated graphene oxide:

[0050] Take 100 mg of graphene oxide and 200 mL of 1 mol / L hydrochloric acid solution, ultrasonically disperse, add 0.5 mmol of sulfosalicylic acid and 20 mL of deionized water, stir evenly, add 150 mg of sodium dodecylbenzenesulfonate, stir evenly to obtain a mixed solution; take 2 mmol of aniline and 1.5 mmol of ethylbenzene, stir evenly, add the mixed solution, emulsify for 4 minutes, add 15 mL of polyvinyl alcohol and stir evenly, add 2 mmol of ammonium persulfate, react for 22 hours, wash and dry to obtain polyaniline-coated graphene oxide;

[0051] Step 5: Take 1 kg of polyaniline-coated graphene oxide and 2 kg of deionized water, ultrasonically disperse them to obtain a graphene solution; take 8 kg of acrylic resin emulsion and 2 kg of epoxy hyperbranched product, add deionized water to dilute to 25% solid content, add 3 kg of graphene solution, add deionized water to dilute to 10% solid content, stir and disperse for 0.5 h, the dispersion speed is 1000 RPM, add 2 kg of n-pentanol, mix and disperse to obtain a water-resistant carbon slurry for lithium batteries.

[0052] Example 4: A method for preparing a water-resistant carbon coating slurry for lithium batteries, comprising the following steps:

[0053] Step 1: Take 3.4 kg of methylcyclohexyl diisocyanate and 1.2 kg of hydroxyethyl methacrylate, stir and mix for 40 minutes, heat to 90 ° C and react for 2 hours, then cool to 50 ° C, add 0.1 kg of butanone oxime, mix well, heat to 80 ° C and react for 4 hours to obtain a monomer;

[0054] Step 2: dissolving 0.2 kg of octadecyltrimethylammonium chloride, 0.26 kg of fatty alcohol polyoxyethylene ether, and 1.2 kg of N-hydroxymethyl acrylamide in 60 kg of pure water, adding 22 kg of octadecyl acrylate, 7 kg of isobornyl methacrylate, the monomer prepared in step 1, 0.05 kg of n-dodecyl mercaptan, and 6 kg of dipropylene glycol dimethyl ether, mixing evenly, and emulsifying with a high-pressure homogenizer to obtain an emulsion; adding the emulsion and 0.06 kg of azobisisobutylamidine hydrochloride initiator to a reaction tank, reacting at 80 ° C for 9 hours under nitrogen protection, to obtain an acrylic resin emulsion;

[0055] Step 3: Preparation of epoxy hyperbranched compounds:

[0056] Take 11g of diethanolamine and 10mL of anhydrous methanol, stir evenly, add 13g of methyl acrylate dropwise under a nitrogen environment, heat to 35°C, react for 5h, rotary evaporate, and extract to obtain a compound monomer; take 13.5g of trimethylolpropane and 0.2g of p-toluenesulfonic acid, heat to 110°C, add the compound monomer dropwise, heat to 125°C, stir for 5.5h, rotary evaporate at 105°C until no bubbling occurs, extract, and rotary evaporate to obtain a hydroxyl hyperbranched product;

[0057] Take 0.02 mol of hydroxy hyperbranched product and 0.04 mol of N,N-dimethylformamide, stir evenly, add 0.2 g of boron trifluoride etherate, stir, add 0.5 mol of epichlorohydrin dropwise, heat to 65°C, keep warm for 3 hours, evaporate by rotary evaporation, add 0.3 mol of 25% sodium hydroxide aqueous solution dropwise, heat to 85°C, react for 4 hours, evaporate by rotary evaporation, filter, and centrifuge to obtain epoxy hyperbranched product;

[0058] Step 4: Preparation of polyaniline-coated graphene oxide:

[0059] Take 100 mg of graphene oxide and 200 mL of 1 mol / L hydrochloric acid solution, ultrasonically disperse, add 0.5 mmol of sulfosalicylic acid and 20 mL of deionized water, stir evenly, add 150 mg of sodium dodecylbenzenesulfonate, stir evenly to obtain a mixed solution; take 2 mmol of aniline and 1.5 mmol of ethylbenzene, stir evenly, add the mixed solution, emulsify for 5 minutes, add 15 mL of polyvinyl alcohol and stir evenly, add 2 mmol of ammonium persulfate, react for 26 hours, wash and dry to obtain polyaniline-coated graphene oxide;

[0060] Step 5: Take 1 kg of polyaniline-coated graphene oxide and 2 kg of deionized water, ultrasonically disperse them to obtain a graphene solution; take 8 kg of acrylic resin emulsion and 2 kg of epoxy hyperbranched product, add deionized water to dilute to 25% solid content, add 3 kg of graphene solution, add deionized water to dilute to 10% solid content, stir and disperse for 2 hours, the dispersion speed is 1500 RPM, add 2 kg of n-pentanol, mix and disperse to obtain a water-resistant carbon coating slurry for lithium batteries.

[0061] Comparative Example 1: A method for preparing a water-resistant carbon coating slurry for lithium batteries, comprising the following steps:

[0062] Take 1 kg of graphene powder and 2 kg of deionized water, ultrasonically disperse them to obtain a graphene solution; take 3 kg of graphene solution, 8 kg of polyacrylic acid binder, 2 kg of n-pentanol, and 0.1 kg of calcium hydroxide, stir for 2 hours, and disperse at 2000 rpm to obtain a carbon-coated slurry.

[0063] Comparative Example 2: Polyaniline is not coated on the graphene oxide, and the rest is the same as Example 2:

[0064] Step 1: Take 3.4 kg of methylcyclohexyl diisocyanate and 1.2 kg of hydroxyethyl methacrylate, stir and mix for 30 minutes, heat to 80 ° C and react for 3 hours, then cool to 40 ° C, add 0.1 kg of butanone oxime, mix well, heat to 70 ° C and react for 3 hours to obtain a monomer;

[0065] Step 2: dissolving 0.2 kg of octadecyltrimethylammonium chloride, 0.26 kg of fatty alcohol polyoxyethylene ether, and 1.2 kg of N-hydroxymethyl acrylamide in 60 kg of pure water, adding 22 kg of octadecyl acrylate, 7 kg of isobornyl methacrylate, the monomer prepared in step 1, 0.05 kg of n-dodecyl mercaptan, and 6 kg of dipropylene glycol dimethyl ether, mixing evenly, and emulsifying with a high-pressure homogenizer to obtain an emulsion; adding the emulsion and 0.06 kg of azobisisobutylamidine hydrochloride initiator to a reaction tank, reacting at 70 ° C for 8 hours under nitrogen protection, to obtain an acrylic resin emulsion;

[0066] Step 3: Preparation of epoxy hyperbranched compounds:

[0067] Take 11g of diethanolamine and 10mL of anhydrous methanol, stir evenly, add 13g of methyl acrylate dropwise under a nitrogen environment, heat to 34°C, react for 4.5h, rotary evaporate, and extract to obtain a compound monomer; take 13.5g of trimethylolpropane and 0.2g of p-toluenesulfonic acid, heat to 108°C, add the compound monomer dropwise, heat to 122°C, stir for 5h, rotary evaporate at 100°C until bubbling stops, extract, and rotary evaporate to obtain a hydroxyl hyperbranched product;

[0068] Take 0.02 mol of hydroxyl hyperbranched product and 0.04 mol of N,N-dimethylformamide, stir evenly, add 0.2 g of boron trifluoride etherate, stir, add 0.5 mol of epichlorohydrin dropwise, heat to 63°C, keep warm for 2.5 hours, evaporate by rotary evaporation, add 0.3 mol of 25% sodium hydroxide aqueous solution dropwise, heat to 80°C, react for 3.5 hours, evaporate by rotary evaporation, filter, and centrifuge to obtain epoxy hyperbranched product;

[0069] Step 4: Take 1kg of graphene oxide and 2kg of deionized water, ultrasonically disperse to obtain a graphene solution; take 8kg of acrylic resin emulsion and 2kg of epoxy hyperbranched product, add deionized water to dilute to 25% solid content, add 3kg of graphene solution, add deionized water to dilute to 10% solid content, stir and disperse for 0.8h, the dispersion speed is 1000RPM, add 2kg of n-pentanol, mix and disperse to obtain a water-resistant carbon coating slurry for lithium batteries.

[0070] Comparative Example 3: No epoxy hyperbranched product was added, and the rest was the same as Example 2:

[0071] Step 1: Take 3.4 kg of methylcyclohexyl diisocyanate and 1.2 kg of hydroxyethyl methacrylate, stir and mix for 30 minutes, heat to 80 ° C and react for 3 hours, then cool to 40 ° C, add 0.1 kg of butanone oxime, mix well, heat to 70 ° C and react for 3 hours to obtain a monomer;

[0072] Step 2: dissolving 0.2 kg of octadecyltrimethylammonium chloride, 0.26 kg of fatty alcohol polyoxyethylene ether, and 1.2 kg of N-hydroxymethyl acrylamide in 60 kg of pure water, adding 22 kg of octadecyl acrylate, 7 kg of isobornyl methacrylate, the monomer prepared in step 1, 0.05 kg of n-dodecyl mercaptan, and 6 kg of dipropylene glycol dimethyl ether, mixing evenly, and emulsifying with a high-pressure homogenizer to obtain an emulsion; adding the emulsion and 0.06 kg of azobisisobutylamidine hydrochloride initiator to a reaction tank, reacting at 70 ° C for 8 hours under nitrogen protection, to obtain an acrylic resin emulsion;

[0073] Step 3: Preparation of polyaniline-coated graphene oxide:

[0074] Take 100 mg of graphene oxide and 200 mL of 1 mol / L hydrochloric acid solution, ultrasonically disperse, add 0.5 mmol of sulfosalicylic acid and 20 mL of deionized water, stir evenly, add 150 mg of sodium dodecylbenzenesulfonate, stir evenly to obtain a mixed solution; take 2 mmol of aniline and 1.5 mmol of ethylbenzene, stir evenly, add the mixed solution, emulsify for 4.5 minutes, add 15 mL of polyvinyl alcohol and stir evenly, add 2 mmol of ammonium persulfate, react for 24 hours, wash and dry to obtain graphene oxide coated with polyaniline;

[0075] Step 4: Take 1 kg of polyaniline-coated graphene oxide and 2 kg of deionized water, ultrasonically disperse them to obtain a graphene solution; take 8 kg of acrylic resin emulsion, add deionized water to dilute it to 25% solid content, add 3 kg of graphene solution, add deionized water to dilute it to 10% solid content, stir and disperse for 0.8 h, the dispersion speed is 1000 RPM, add 2 kg of n-pentanol, mix and disperse, and obtain a water-resistant carbon slurry for lithium batteries.

[0076] experiment:

[0077] The water-resistant carbon coating slurries for lithium batteries prepared in Examples 1-4 and Comparative Examples 1-3 were respectively coated on one side of a 13 μm aluminum foil and baked at 100° C. for 1 min to obtain a carbon-coated aluminum foil current collector with a total thickness of 13.5 μm for performance testing.

[0078] (1) Carbon coating contact angle test method: drop a drop of 1 μL of water on the carbon coating and use a water contact angle meter to measure the water contact angle of the carbon coating;

[0079] (2) Water wiping test method: Fix the carbon-coated aluminum foil current collector on the table, press a 25g weight + a 55g adjustment rod (80g in total) on a cotton swab soaked in pure water, apply a force F, pull the weight and the adjustment rod back and forth to make the cotton swab wipe the carbon-coated foil coating surface, observe whether the coating changes color and falls off, and record the number of wipes;

[0080] (3) Peel strength test after rolling: After equilibrating at 25°C and 60% relative humidity for 1 hour, use 3M610 tape to adhere to the coating surface and roll twice with a 2kg roller. Finally, use a tensile testing machine to perform a 180° peel test. The peel strength of a sample 12 cm long x 5 cm wide is tested. The data obtained are shown in the following table:

[0081] Water-resistant wipe Carbon coating contact angle° Peeling force after rolling N / M Example 1 >200 times 105 30 Example 2 >300 times 120 38 Example 3 >300 times 119 37 Example 4 >300 times 120 38 Comparative Example 1 8 times 19 30 Comparative Example 2 >250 times 109 35 Comparative Example 3 >250 times 117 33

[0082] Conclusion: From the comparison of the data in the table, it can be seen that Example 1 uses the acrylic resin emulsion prepared by the present invention as the base material of the carbon-coated slurry. Compared with the polyacrylic acid binder in Comparative Example 1, the contact angle of the coating is significantly improved, the surface water resistance is enhanced, and the peeling force of the electrode after rolling is significantly improved. Comparative Example 2 does not coat polyaniline on the graphene oxide, and the contact angle is lower than that of Examples 2-4, and the surface water resistance becomes worse. Comparative Example 3 does not add epoxy hyperbranched substances, and the peeling force after rolling decreases. The epoxy groups on the epoxy hyperbranched substances added in Examples 2-4 can react with the amino groups on the graphene oxide coated with polyaniline, and the two are cross-linked with each other, thereby further enhancing the water resistance and peeling force of the carbon-coated slurry. Adding graphene oxide coated with polyaniline as a conductive material to the carbon-coated slurry further enhances the water resistance of the carbon-coated slurry.

[0083] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a water-resistant carbon coating slurry for lithium batteries, characterized by: The following steps are involved: Step 1: Take methylcyclohexyl diisocyanate and hydroxyethyl methacrylate, stir and mix for 15-40 minutes, heat to 60-90°C and react for 1-4 hours, then cool to 30-50°C, add butanone oxime, mix evenly, heat to 60-80°C and react for 2-4 hours to prepare a monomer; Step 2: dissolving octadecyltrimethylammonium chloride, fatty alcohol polyoxyethylene ether, and N-hydroxymethyl acrylamide in pure water, adding octadecyl acrylate, isobornyl methacrylate, monomer, n-dodecyl mercaptan, and dipropylene glycol dimethyl ether, mixing evenly, and emulsifying to obtain an emulsion; taking the emulsion and an initiator azobisisobutylamidine hydrochloride, reacting under nitrogen protection at 50-80°C for 5-9 hours to obtain an acrylic resin emulsion; Step 3: Take acrylic resin emulsion, deionized water, conductive agent, and wetting agent, stir and disperse them to prepare a water-resistant carbon coating slurry for lithium batteries.

2. The method for preparing a water-resistant carbon coating slurry for lithium batteries according to claim 1, characterized in that: In step 3, the stirring and dispersing time is 0.5-2h, and the dispersing speed is 500-1500RPM.

3. The method for preparing a water-resistant carbon coating slurry for lithium batteries according to claim 1, characterized in that: The carbon coating slurry comprises the following components, calculated by weight: 10-60 parts of acrylic resin emulsion, 10-30 parts of deionized water, 2-30 parts of conductive agent, and 0.1-6 parts of wetting agent.

4. The method for preparing a water-resistant carbon coating slurry for lithium batteries according to claim 1, wherein: The wetting agent is selected from any one or more of n-pentanol, ethanol, methanol, and isopropanol.

5. The method for preparing a water-resistant carbon coating slurry for lithium batteries according to claim 1, wherein: The conductive agent is any one or more of acetylene black, natural graphite, and artificial graphite.

6. The method for preparing a water-resistant carbon coating slurry for lithium batteries according to claim 1, characterized in that: The acrylic resin emulsion includes the following components, calculated by mass: 3-5 parts of methylcyclohexane diisocyanate, 1-3 parts of hydroxyethyl methacrylate, 0.01-0.5 parts of butanone oxime, 0.01-0.5 parts of octadecyltrimethylammonium chloride, 0.1-0.6 parts of fatty alcohol polyoxyethylene ether, 1-3 parts of N-hydroxymethyl acrylamide, 20-30 parts of octadecyl acrylate, 5-10 parts of isobornyl methacrylate, 0.01-0.4 parts of n-dodecyl mercaptan, 5-10 parts of dipropylene glycol dimethyl ether, and 0.01-4 parts of azobisisobutylamidine hydrochloride.

7. The method for preparing a water-resistant carbon coating slurry for lithium batteries according to claim 5, characterized in that: The conductive agent is graphene oxide coated with polyaniline, and the preparation method is as follows: taking graphene oxide and hydrochloric acid solution, ultrasonically dispersing, adding sulfosalicylic acid and deionized water, stirring evenly, adding sodium dodecylbenzenesulfonate, stirring evenly to obtain a mixed solution; taking aniline and ethylbenzene, stirring evenly, adding the mixed solution, emulsifying for 4-5 minutes, adding polyvinyl alcohol and stirring evenly, adding ammonium persulfate, reacting for 22-26 hours, washing, and drying to obtain graphene oxide coated with polyaniline.

8. The method for preparing a water-resistant carbon coating slurry for lithium batteries according to claim 3, characterized in that: Epoxy hyperbranched products are also added to the carbon coating slurry. The preparation method of epoxy hyperbranched products is as follows: The following steps are involved: S1: Take diethanolamine and anhydrous methanol, stir evenly, add methyl acrylate dropwise under nitrogen atmosphere, heat to 33-35°C, react for 4-5 hours, rotary evaporate, extract, and obtain compound monomer; take trimethylolpropane and p-toluenesulfonic acid, heat to 105-110°C, add compound monomer dropwise, heat to 120-125°C, stir for 4.5-5.5 hours, rotary evaporate at 95-105°C until bubbling stops, extract, and rotary evaporate to obtain hydroxyl hyperbranched product; S2: Take hydroxyl hyperbranched product and N,N-dimethylformamide, stir evenly, add boron trifluoride etherate, stir, add epichlorohydrin dropwise, heat to 60-65°C, keep warm for 2-3 hours, rotary evaporate, add sodium hydroxide aqueous solution dropwise, heat to 75-85°C, react for 3-4 hours, rotary evaporate, filter, and centrifuge to obtain epoxy hyperbranched product.

9. The method for preparing a water-resistant carbon coating slurry for lithium batteries according to claims 7-8, characterized in that: The following steps are involved: Step 1: Take methylcyclohexyl diisocyanate and hydroxyethyl methacrylate, stir and mix for 15-40 minutes, heat to 60-90°C and react for 1-4 hours, then cool to 30-50°C, add butanone oxime, mix well, heat to 60-80°C and react for 2-4 hours to obtain a monomer; Step 2: dissolving octadecyltrimethylammonium chloride, fatty alcohol polyoxyethylene ether, and N-hydroxymethyl acrylamide in pure water, adding octadecyl acrylate, isobornyl methacrylate, monomer, n-dodecyl mercaptan, and dipropylene glycol dimethyl ether, mixing evenly, and emulsifying to obtain an emulsion; taking the emulsion and an initiator azobisisobutylamidine hydrochloride, reacting under nitrogen protection at 50-80°C for 5-9 hours to obtain an acrylic resin emulsion; Step 3: Take acrylic resin emulsion, deionized water, polyaniline-coated graphene oxide, epoxy hyperbranched product, and wetting agent, stir and disperse them to prepare a water-resistant carbon coating slurry for lithium batteries.

10. The method for preparing a water-resistant carbon coating slurry for lithium batteries according to claim 9, characterized in that: The carbon coating slurry comprises the following components, calculated by weight: 10-60 parts of acrylic resin emulsion, 10-30 parts of deionized water, 2-30 parts of polyaniline-coated graphene oxide, 3-5 parts of epoxy hyperbranched product, and 0.1-6 parts of wetting agent.