An insulating coating paste and a method of preparing it for dip coating on a battery case

Abstract

The application relates to a kind of insulating coating slurry and preparation method for dip coating on battery shell, and relates to the technical field of battery production, the insulating coating slurry, including the following weight parts of each raw material component: 20-50 parts of inorganic precursor;10-40 parts of aqueous organic resin;5-20 parts of inorganic filler;20-40 parts of solvent;1-5 parts of auxiliary agent;The above raw material components are prepared into insulating coating slurry, and then the insulating coating slurry is dip coated on the battery shell, the inorganic precursor in the insulating coating slurry makes the insulating coating have higher hardness, better heat resistance, insulation, chemical corrosion resistance and other characteristics;Aqueous organic resin provides good flexibility and high adhesion to the substrate, during the curing process, the inorganic network and the aqueous organic resin are penetrated and bonded at the molecular scale, forming a dense and uniform hybrid structure, and the inorganic filler uses inorganic ceramic particles as a reinforcing phase, further improving the insulation, hardness, corrosion resistance, heat resistance and other properties of the insulating coating.

Description

An insulating coating slurry and a method for preparing it by dip-coating it onto a battery casing. Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and in particular to an insulating coating slurry and a method for preparing it by dipping the slurry onto a battery casing. Background Technology

[0002] Existing battery casings are typically made of aluminum alloy or stainless steel. In order to achieve insulation between individual cells, the outer side of the battery casing usually needs to be covered with PET blue film. This insulation process increases the manufacturing process of individual cells and is not conducive to efficient production.

[0003] As is well known, insulation protection is also required between the bare cell and the battery casing inside the battery casing to prevent casing corrosion caused by the negative electrode conducting through the casing. The existing insulation solution between the cell and the casing is to coat the bare cell with a Mylar film. However, in actual use, the Mylar film cannot completely isolate the conduction between the casing and the cell. There are still cases where welding slag or particles puncture the Mylar film, causing a short circuit between the cell and the casing. In addition, the process of coating the bare cell with a Mylar film also complicates the cell manufacturing process and reduces the efficiency of production.

[0004] In the invention application with application number 202311151563.6, application date 2023.09.07, and title: Preparation method of lithium battery casing and insulating corrosion-resistant coating, the invention discloses the technical feature of using PET, polyamide epoxy resin, etc. as insulating materials for the insulating coating inside the casing. However, the method only performs insulation treatment on the inside of the casing and does not consider the insulation treatment on the outside of the casing. Moreover, the curing temperature of the coating is between 100℃ and 130℃, and the curing process is relatively complicated.

[0005] The invention disclosed in application number 202211094001.8, application date 2022.09.08, entitled "A UV-curable adhesive for batteries and its application", discloses a UV-curable adhesive mainly composed of polytetrahydrofuran acrylate prepolymer and first acrylate monomer, used for external insulation protection of battery casing. The technical solution is that the coating is sprayed at low to medium temperature and then cured after UV irradiation. The coating and process are relatively simple, but require coating equipment and light curing equipment, which increases production costs.

[0006] The aforementioned invention proposes solutions for internal or external insulation of the battery casing, but it does not provide a comprehensive design for the internal and external insulation protection of the battery casing, and it also has problems such as complex process flow and equipment. Therefore, a new solution is needed for the insulation protection of the battery casing. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an insulating coating slurry and a method for preparing it by dipping it onto a battery casing.

[0008] The technical solution adopted in this invention is:

[0009] An insulating coating paste comprising the following raw material components in parts by weight:

[0010] 20-50 parts of inorganic precursor;

[0011] 10-40 parts of water-based organic resin;

[0012] 5-20 parts of inorganic filler;

[0013] 20-40 parts solvent;

[0014] 1-5 parts of adjuvant;

[0015] The raw material components of the above slurry satisfy formula (1):

[0016] 0.5 < (W2 + W3) / W1 < 6 (1);

[0017] Wherein, W1 represents the number of parts of the effective component of the water-based organic resin, W2 represents the number of parts of the effective component of the inorganic precursor, and W3 represents the number of parts of the inorganic filler.

[0018] Specifically, the inorganic precursor is any one of the following: tetrabutyl orthosilicate pre-reaction solution, tetrabutyl titanate pre-reaction solution, silica sol, and aluminum dihydrogen phosphate.

[0019] Specifically, the waterborne organic resin is any one of waterborne epoxy resin, waterborne acrylic resin, waterborne polyurethane resin, and waterborne silicone resin.

[0020] Specifically, the inorganic filler is any one of aluminum nitride, aluminum oxide, silicon carbide, silicon dioxide, or boron nitride, which are nano- or submicron-sized particles.

[0021] Specifically, the solvent is water.

[0022] Specifically, the additive is at least one of silane coupling agent, leveling agent, defoamer, and dispersant.

[0023] The preparation method of the insulating coating slurry specifically includes the following steps:

[0024] S1. Add 20-30 parts of solvent, water-based organic resin and additives to a high-speed disperser and stir for 10-30 minutes;

[0025] S2. Following the previous step, add inorganic filler to the high-speed disperser and stir for 1-2 hours;

[0026] S3. Following the previous step, add the remaining solvent, water-based organic resin, and additives to a high-speed disperser and stir for 30-60 minutes.

[0027] S4. Finally, add the inorganic precursor to the slurry formed in the previous step and continue stirring for 30-60 minutes.

[0028] S5. Let the slurry with the added inorganic precursor stand for 2 hours to eliminate foaming.

[0029] Specifically, in step S1, the stirring speed of the high-speed disperser is 200-500 r / min; in step S2, the stirring speed of the high-speed disperser is 1000-1200 r / min; in step S3, the stirring speed of the high-speed disperser is 200-500 r / min; and in step S4, the stirring speed of the high-speed disperser is 200-500 r / min.

[0030] A method for preparing an insulating coating slurry by dip-coating it onto a battery casing, comprising the following specific steps:

[0031] At room temperature, after phosphating, the battery casing, except for the 2mm protective area on the upper inner edge, is completely immersed in the prepared insulating coating slurry for 10-20 minutes. Then, using a special tool, the battery casing is held against the inner cavity of the battery casing and lifted at a uniform speed. The casing is then placed in a ventilated and dry place at room temperature for 24-48 hours until the coating hardens. The above dipping and coating process is repeated 2-4 times until the coating thickness reaches 80-120μm to obtain a battery casing with an insulating coating on both the inner and outer surfaces.

[0032] Due to the adoption of the technical solution described above, the present invention has the following advantages:

[0033] 1. The insulating coating slurry and its preparation method for dipping onto a battery casing as described in this invention, wherein the inorganic precursor in the insulating coating slurry provides a ceramic skeleton, which forms an inorganic network structure after curing, giving the insulating coating high hardness, good heat resistance, insulation, and chemical corrosion resistance; the water-based organic resin acts as a continuous phase, providing good flexibility, high adhesion to the substrate, and promoting the cross-linking and curing of the inorganic network. During the curing process, the inorganic network and the water-based organic resin penetrate and bond at the molecular scale, forming a dense and uniform hybrid structure; the inorganic filler uses inorganic ceramic particles as a reinforcing phase, further improving the insulation, hardness, corrosion resistance, and heat resistance properties of the insulating coating.

[0034] 2. The insulating coating slurry and its preparation method for dipping it onto a battery casing according to the present invention employ a dipping coating method to coat both the inner and outer surfaces of the battery casing with the insulating coating slurry, replacing the commonly used PET blue film in the market. This eliminates the need for the film application process on the outside of the individual battery casing, simplifying the battery manufacturing process and improving the adhesion between the insulating layer and the substrate. Furthermore, the main component of the insulating coating slurry is a ceramic-based inorganic non-metallic material, which has higher insulation performance and thermal stability than resin-based polymer materials such as PET. It also replaces the cell protective film used in the current process, eliminating the film application process before the cell is inserted into the casing. While simplifying the process, it effectively isolates the ion and electron pathways between the casing and the electrodes, preventing corrosion of the battery casing.

[0035] 3. The insulating coating slurry and its preparation method for dipping onto a battery casing according to the present invention, wherein the raw material composition of the slurry satisfies the formula 0.5<(W2+W3) / W1<6, can obtain a higher coating breakdown voltage compared with the prior art. Detailed Implementation

[0036] The present invention will be further explained and illustrated below with reference to embodiments. However, this should not be construed as limiting the scope of protection of the present invention. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention.

[0037] The insulating coating paste of the present invention comprises the following raw material components in parts by weight:

[0038] 20-50 parts of inorganic precursor, wherein the inorganic precursor is any one of tetraethyl orthosilicate pre-reaction solution, tetrabutyl titanate pre-reaction solution, silica sol, and aluminum dihydrogen phosphate.

[0039] 10-40 parts of waterborne organic resin, wherein the waterborne organic resin is any one of waterborne epoxy resin, waterborne acrylic resin, waterborne polyurethane resin, and waterborne silicone resin;

[0040] 5-20 parts of inorganic filler, wherein the inorganic filler is any one of nano- or submicron-sized aluminum nitride, aluminum oxide, silicon carbide, silicon dioxide, or boron nitride.

[0041] 20-40 parts of solvent, the solvent being water;

[0042] 1-5 parts of additives, wherein the additives are at least one of silane coupling agents, leveling agents, defoamers, and dispersants;

[0043] The raw material components of the above slurry satisfy formula (1):

[0044] 0.5 < (W2 + W3) / W1 < 6 (1);

[0045] Wherein, W1 represents the number of parts of the effective component of the water-based organic resin, W2 represents the number of parts of the effective component of the inorganic precursor, and W3 represents the number of parts of the inorganic filler.

[0046] This invention suggests that a higher W1 indicates a higher proportion of organic components, resulting in better coating continuity and lower porosity. However, excessively high W1 leads to a relatively low proportion of inorganic components, which in turn reduces the coating's insulation. Conversely, a lower W1 indicates a relatively high proportion of inorganic components, resulting in insufficient wetting by organic components, higher coating porosity, and increased susceptibility to breakdown, thus reducing insulation. A higher W2 indicates a higher proportion of ceramic skeletons formed by inorganic precursors, which promotes coating insulation and acts as a carrier for filler dispersion. However, coatings formed by inorganic precursors are relatively porous, and excessively high W2 can lead to larger leakage currents, making the coating prone to breakdown and reducing insulation. Conversely, excessively low W2 results in a lower proportion of inorganic network structure, with the coating matrix mainly composed of organic components, leading to reduced insulation. A higher W3 indicates a greater amount of inorganic reinforcing phase, which promotes improved coating insulation. However, excessively high W3 can cause inorganic particles to agglomerate, increasing coating roughness, making it prone to breakdown, and lowering the breakdown voltage.

[0047] The preparation method of the insulating coating slurry specifically includes the following steps:

[0048] S1. Add 20-30 parts of solvent, water-based organic resin and additives to a high-speed disperser and stir for 10-30 minutes at a stirring speed of 200-500 r / min.

[0049] S2. Following the previous step, add inorganic filler to the high-speed disperser and stir at a stirring speed of 1000-1200 r / min for 1-2 hours;

[0050] S3. Following the previous step, add the remaining solvent, water-based organic resin, and additives to a high-speed disperser and stir at a stirring speed of 200-500 r / min for 30-60 min.

[0051] S4. Finally, add the inorganic precursor to the slurry formed in the previous step and continue to stir at a stirring speed of 200-500 r / min for 30-60 min.

[0052] S5. Let the slurry with the added inorganic precursor stand for 2 hours to eliminate foaming.

[0053] A method for preparing an insulating coating slurry by dip-coating it onto a battery casing, comprising the following specific steps:

[0054] At room temperature, after phosphating, the battery casing, except for the 2mm protective area on the upper inner edge, is completely immersed in the prepared insulating coating slurry for 10-20 minutes. Then, using a special tool, the battery casing is held against the inner cavity of the battery casing and lifted at a uniform speed. The casing is then placed in a ventilated and dry place at room temperature for 24-48 hours until the coating hardens. The above dipping and coating process is repeated 2-4 times until the coating thickness reaches 80-120μm to obtain a battery casing with an insulating coating on both the inner and outer surfaces.

[0055] Example 1

[0056] The preparation method of the insulating coating slurry is as follows:

[0057] Add 30 parts water, 35 parts waterborne epoxy resin, 1 part silane coupling agent KH550, and 0.4 parts dispersant polyacrylamide to a high-speed disperser and stir at 300 rpm for 30 min. Add 10 parts nano-aluminum nitride to the high-speed disperser and stir at 1200 rpm for 2 h. Add the remaining 10 parts water, 5 parts waterborne epoxy resin, 2 parts leveling agent polyether-modified polysiloxane BYK-333, and 0.4 parts defoamer acrylate BYK024 to the high-speed disperser and stir at 400 rpm for 30 min. Finally, slowly add 35 parts aluminum dihydrogen phosphate to the slurry formed in the previous step and continue stirring at 400 rpm for 30 min. Let stand for 2 h to eliminate foaming. The waterborne epoxy resin accounts for 50% of the total mass, i.e., the effective component of the waterborne epoxy resin is 20 parts.

[0058] The method for preparing an insulating coating slurry by dip-coating it onto the battery casing is as follows:

[0059] At room temperature, the square aluminum battery casing, after phosphating, is completely immersed in the prepared insulating coating slurry for 20 minutes, except for the 2mm protective area on the upper inner edge. Then, a special tool is used to hold the battery casing in the inner cavity and lift it up at a uniform speed. The casing is then placed in a ventilated and dry place at room temperature for 24-48 hours until the coating hardens. The above dipping and coating process is repeated twice until the coating thickness reaches 92μm, resulting in a battery casing with an insulating coating on both the inner and outer surfaces.

[0060] Example 2

[0061] The preparation method of the insulating coating slurry is as follows:

[0062] Add 25 parts water, 30 parts waterborne acrylic resin, 0.4 parts silane coupling agent KH550, and 0.4 parts dispersant polyacrylamide to a high-speed disperser and stir at 400 rpm for 30 minutes. Add 10 parts nano-alumina to the high-speed disperser and stir at 1100 rpm for 2 hours. Add the remaining 10 parts water, 10 parts waterborne acrylic resin, 1.5 parts leveling agent polyether-modified polysiloxane BYK-333, and 0.4 parts defoamer acetone to the disperser. The acrylic ester BYK024 was added to a high-speed disperser and stirred at 400 rpm for 30 minutes. Finally, 35 parts of silica sol were slowly added to the slurry formed in the previous step, and stirring was continued at 400 rpm for 30 minutes. The mixture was allowed to stand for 2 hours to eliminate foaming. The waterborne acrylic resin accounted for 50% by mass, that is, the effective component of the waterborne acrylic resin was 20 parts; the silica sol accounted for 50% by mass, that is, the effective component of the silica sol was 17.5 parts.

[0063] The method for preparing an insulating coating slurry by dip-coating it onto the battery casing is as follows:

[0064] At room temperature, the cylindrical steel battery casing, after phosphating, is completely immersed in the prepared insulating coating slurry for 20 minutes, except for the 2mm protective area on the upper inner edge. Then, a special tool is used to hold the battery casing in the inner cavity and lift it up at a uniform speed. The casing is then placed in a ventilated and dry place at room temperature for 24-48 hours until the coating hardens. The above dipping and coating process is repeated 3 times until the coating thickness reaches 115μm, resulting in a battery casing with an insulating coating on both the inner and outer surfaces.

[0065] Example 3

[0066] The preparation method of the insulating coating slurry is as follows:

[0067] Add 20 parts water, 15 parts waterborne polyurethane resin, 0.8 parts silane coupling agent KH550, and 0.8 parts dispersant polyacrylamide to a high-speed disperser and stir at 500 rpm for 30 minutes. Add 15 parts submicron-sized silicon carbide to the high-speed disperser and stir at 1200 rpm for 2 hours. Add the remaining 10 parts water, 10 parts waterborne acrylic resin, and 1.5 parts leveling agent polyether-modified polysiloxane BYK- 333 and 0.5 parts of defoamer acrylate BYK024 were added to a high-speed disperser and stirred at 300 r / min for 20 min; finally, 50 parts of tetraethyl orthosilicate pre-reaction solution were slowly added to the slurry formed in the previous step, and stirring was continued at 300 r / min for 60 min; let stand for 2 h to eliminate foaming; wherein, the mass percentage of waterborne polyurethane resin is 35%, that is, the effective component of waterborne polyurethane resin is 8.75 parts;

[0068] The tetraethyl orthosilicate pre-reaction solution is prepared as follows: Anhydrous ethanol, acetic acid, and water are mixed uniformly at a molar ratio of 1:0.01:2 under conditions of 300 r / min and 60°C. An equal amount of tetraethyl orthosilicate as anhydrous ethanol is then added dropwise at a constant rate over a period of 1 hour. The mixture is then stirred for another 1 hour to form the tetraethyl orthosilicate pre-reaction solution. The mass percentage of tetraethyl orthosilicate in the pre-reaction solution is 71.6%, meaning the effective component of tetraethyl orthosilicate is 35.8 parts.

[0069] The method for preparing an insulating coating slurry by dip-coating it onto the battery casing is as follows:

[0070] At room temperature, the phosphated square steel battery casing, except for the 2mm protective area on the upper inner edge, is completely immersed in the prepared insulating coating slurry for 20 minutes. Then, a special tool is used to hold the battery casing in the inner cavity and lift it up at a uniform speed. The casing is then placed in a ventilated and dry place at room temperature for 24-48 hours until the coating hardens. The above dipping and coating process is repeated 3 times until the coating thickness reaches 110μm, thus obtaining a battery casing with an insulating coating on both the inner and outer surfaces.

[0071] Example 4

[0072] The preparation method of the insulating coating slurry is as follows:

[0073] Add 20 parts water, 25 parts waterborne silicone resin, 0.4 parts silane coupling agent KH550, and 0.4 parts dispersant polyacrylamide to a high-speed disperser and stir at 300 rpm for 60 min. Add 6 parts nano boron nitride to the high-speed disperser and stir at 1000 rpm for 1 h. Add the remaining 10 parts water, 10 parts waterborne silicone resin, and 1.0 part leveling agent polyether-modified polysiloxane BYK-33. 3. Add 0.5 parts of defoamer acrylate BYK024 to a high-speed disperser and stir at 300 r / min for 30 min; finally, slowly add 25 parts of tetrabutyl titanate pre-reaction solution to the slurry formed in the previous step and continue stirring at 300 r / min for 60 min; let stand for 2 h to eliminate foaming; wherein, the mass percentage of waterborne silicone resin is 45%, that is, the effective component of waterborne silicone resin is 15.75 parts;

[0074] The tetrabutyl titanate pre-reaction solution is prepared as follows: Tetrabutyl titanate and ethanol are mixed at a volume ratio of 1:4 and stirred continuously for 1 hour to form solution A; simultaneously, water, nitric acid, and ethanol are mixed at a volume ratio of 5:1:4 and stirred continuously for 30 minutes to obtain solution B; solution A and solution B are added dropwise to solution A at a volume ratio of 5:1, and the mixture is stirred continuously for 1 hour to obtain the tetrabutyl titanate pre-reaction solution; wherein, the mass percentage of tetrabutyl titanate in the tetrabutyl titanate pre-reaction solution is 16.4%, that is, the effective component of tetrabutyl titanate is 4.1 parts.

[0075] The method for preparing an insulating coating slurry by dip-coating it onto the battery casing is as follows:

[0076] At room temperature, the entire battery casing, except for the 2mm protective area on the upper inner edge, of the phosphated square aluminum casing is immersed in the prepared insulating coating slurry for 20 minutes. Then, a special tool is used to hold the battery casing in the inner cavity and lift it up at a uniform speed. The casing is then placed in a ventilated and dry place at room temperature for 24-48 hours until the coating hardens. The above immersion coating process is repeated 3 times until the coating thickness reaches 105μm, thus obtaining a battery casing with an insulating coating on both the inner and outer surfaces.

[0077] Example 5

[0078] The preparation method of the insulating coating slurry is as follows:

[0079] Add 25 parts water, 25 parts waterborne epoxy resin, 0.6 parts silane coupling agent KH550, and 0.6 parts dispersant polyacrylamide to a high-speed disperser and stir at 300 rpm for 30 min. Add 5 parts nano-silica to the high-speed disperser and stir at 1200 rpm for 2 h. Add the remaining 10 parts water, 5 parts waterborne epoxy resin, 1.0 part leveling agent polyether-modified polysiloxane BYK-333, and 0.4 parts defoamer acrylate BYK024 to the high-speed disperser and stir at 400 rpm for 30 min. Finally, slowly add 25 parts aluminum dihydrogen phosphate to the slurry formed in the previous step and continue stirring at 400 rpm for 60 min. Let stand for 2 h to eliminate foaming. The waterborne epoxy resin accounts for 50% of the total mass, i.e., the effective component of the waterborne epoxy resin is 15 parts.

[0080] The method for preparing an insulating coating slurry by dip-coating it onto the battery casing is as follows:

[0081] At room temperature, the square aluminum battery casing, after phosphating, is completely immersed in the prepared insulating coating slurry for 20 minutes, except for the 2mm protective area on the upper inner edge. Then, a special tool is used to hold the battery casing in the inner cavity and lift it up at a uniform speed. The casing is then placed in a ventilated and dry place at room temperature for 24-48 hours until the coating hardens. The above dipping and coating process is repeated twice until the coating thickness reaches 98μm, resulting in a battery casing with an insulating coating on both the inner and outer surfaces.

[0082] Comparative Example 1

[0083] The insulating and corrosion-resistant coating comprises 70%-80% insulating material and 20%-30% binder by weight percentage; the insulating material is one or more of PET, polyamide epoxy resin, phenol-formaldehyde resin, alkyd resin, chlorinated rubber, vinyl resin, polyaniline, and polyurethane; the binder is one of PTFE emulsion and PVDF emulsion.

[0084] The insulating and corrosion-resistant coating is applied to the main body of the casing using a thermal spraying method and then baked in an oven.

[0085] Comparative Example 2

[0086] The insulating coating for new energy batteries is composed of the following raw materials in parts by weight: 60 parts of bisphenol A type epoxy resin, 1 part of 10-hydroxydecanoic acid, 0.5 parts of 2-methylimidazole, 0.3 parts of dispersant BYK110, 1 part of GLP588 leveling agent, and 5 parts of silica powder.

[0087] Epoxy resin, 10-hydroxydecanoic acid, 2-methylimidazole, dispersant BYK110, GLP588 leveling agent, and filler are mixed evenly and extruded using a twin-screw extruder at an extrusion temperature of 110℃. After cooling and crushing, the mixture is passed through an 180-mesh sieve to obtain an insulating coating.

[0088] The insulating coatings prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests. The performance tests included: insulation effect according to the standard of GB / T1408.1-2016 for testing breakdown voltage, and adhesion according to the standard of GB / T9486-2021.

[0089] The test results of Examples 1-5 and Comparative Examples 1-2 of this invention are shown in Table 1.

[0090] Table 1

[0091]

[0092] The calculation results in Table 1 are rounded to two significant figures. Compared with Comparative Examples 1-2, the breakdown voltage of Examples 1-5 of the present invention is much higher than that of Comparative Examples 1-2. The insulating coating of the present invention can withstand higher voltages without being broken down, thus improving the safety, reliability and service life of the battery casing. Furthermore, the adhesion level of Examples 1-5 of the present invention is better than that of Comparative Examples 1-2, indicating that the coating of the insulating coating of the present invention is extremely firmly bonded to the battery casing, and there is no risk of the coating detaching from the substrate.

[0093] The parts of this invention not described in detail are prior art.

[0094] The embodiments selected herein for the purpose of disclosing the inventive objectives are currently considered suitable; however, it should be understood that the invention is intended to include all variations and modifications of the embodiments that fall within the scope of this concept and invention.

Claims

1. A method for preparing an insulating coating slurry by dip-coating it onto a battery casing, characterized in that: Specifically, the following steps are included: a. Preparation of insulating coating slurry: The insulating coating slurry comprises the following raw material components in parts by weight: 20-50 parts of inorganic precursor; the inorganic precursor is any one of tetraethyl orthosilicate pre-reaction solution, tetrabutyl titanate pre-reaction solution, silica sol, and aluminum dihydrogen phosphate; 10-40 parts of waterborne organic resin; the waterborne organic resin is any one of waterborne epoxy resin, waterborne acrylic resin, waterborne polyurethane resin, and waterborne silicone resin; 5-20 parts of inorganic filler; the inorganic filler is any one of nano- or submicron-sized aluminum nitride, alumina, silicon carbide, silicon dioxide, and boron nitride; 20-40 parts of solvent; the solvent is water; 1-5 parts of additives; the raw material components of the above slurry satisfy formula (1): 0.5 < (W2 + W3) / W1 < 6 (1); where W1 represents the number of parts of the effective component of the waterborne organic resin, W2 represents the number of parts of the effective component of the inorganic precursor, and W3 represents the number of parts of the inorganic filler; S1, add 20-30 parts of solvent, waterborne organic resin, and additives to a high-speed disperser and stir for 10-30 min; S2, following the previous step, add inorganic filler to the high-speed disperser and stir for 1-2 h; S3, following the previous step, add the remaining solvent, waterborne organic resin, and additives to the high-speed disperser and stir for 30-60 min; S4, finally add the inorganic precursor to the slurry formed in the previous step and continue stirring for 30-60 min; S 5. Let the slurry containing the inorganic precursor stand for 2 hours to eliminate foaming; b. Dip the insulating coating slurry prepared in step a onto the battery casing: At room temperature, immerse the phosphated battery casing, except for the 2mm protective area at the upper inner edge, completely in the prepared insulating coating slurry for 10-20 minutes. Then, use a special tool to hold the battery casing in the inner cavity and slowly lift the battery casing. Place it in a ventilated and dry place at room temperature for 24-48 hours until the coating hardens. Repeat the above dipping process 2-4 times until the coating thickness reaches 80-120μm to obtain a battery casing with an insulating coating on both the inner and outer surfaces.

2. The method for preparing an insulating coating slurry by dip-coating it onto a battery casing according to claim 1, characterized in that: The additive is at least one of silane coupling agent, leveling agent, defoamer, and dispersant.

3. The method for preparing an insulating coating slurry by dip-coating it onto a battery casing according to claim 1, characterized in that: In step S1, the stirring speed of the high-speed disperser is 200-500 r / min; in step S2, the stirring speed of the high-speed disperser is 1000-1200 r / min; in step S3, the stirring speed of the high-speed disperser is 200-500 r / min; and in step S4, the stirring speed of the high-speed disperser is 200-500 r / min.

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