High-pressure-resistant flame-retardant insulating coating liquid for lithium battery shell and preparation method thereof

Abstract

The application belongs to the technical field of insulating materials, and particularly relates to a high-pressure-resistant and flame-retardant insulating coating liquid for lithium battery shells and a preparation method thereof, wherein the raw materials are composed of the following components in percentage by mass: water-based alkyd resin 5-15%, water-based silicone resin 5-15%, water-based polyurethane resin 3-5%, modified nano composite liquid 3-8%, phosphoric acid composite salt 8-15%, ammonium molybdate 1-2%, ammonium tungstate 1-2%, water-based titanate chelate 3-5%, flame retardant 3-6%, dispersant 0.5-2%, and water as the balance. The coating formed by the coating liquid has excellent high-pressure resistance, flame retardancy, corrosion resistance and heat resistance, and has a good application and promotion prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of insulating materials, and particularly relates to a high-voltage-resistant and flame-retardant insulating coating for a lithium battery shell and a preparation method thereof. BACKGROUND

[0002] With the improvement of people's living standards, in the rapidly changing automobile industry, new energy vehicles are rapidly developing in various places due to their low product noise, high driving stability, and zero-emission green environmental protection. As green travel, new energy vehicles have longer and longer endurance, more series of battery packs, and smaller spacing between adjacent batteries. During use, high-density battery packs have contact between each battery cell and the influence of the external environment. If the insulation is not properly handled, the internal voltage of the battery will increase, and short circuits and other problems will cause electrical leakage. At the same time, the battery pack of the automobile is prone to heat and high temperature during driving. Therefore, the quality of the insulating material between the batteries is a key factor in determining the good operation of the automobile power battery. High-performance insulating materials can improve the applicability of new energy power batteries and prolong their service life.

[0003] At present, traditional power batteries are mostly insulated by insulating paper, film wrapping, and insulating coating for insulation protection and packaging between batteries. Insulating paper has good insulating properties and flexibility, but there is an air gap between the insulating paper and the battery shell, which can easily cause partial discharge and affect the service life of the battery, thereby increasing the uncertainty of the new energy electric vehicle during driving. The film wrapping process is complex. The existing insulating coating has low bonding strength, and is prone to peeling, wear and tear, and other conditions with the increase of use time, and has poor insulation effect in a high-pressure environment. SUMMARY

[0004] The present application provides a high-voltage-resistant and flame-retardant insulating coating liquid for a lithium battery shell and a preparation method thereof, aiming to solve the problems of low adhesion, insufficient high-pressure resistance, poor temperature resistance, and other problems of existing lithium battery shell insulating coatings.

[0005] To solve the above technical problems, the present application provides the following technical solutions:

[0006] The present application first provides a high-voltage-resistant and flame-retardant insulating coating liquid for a lithium battery shell, wherein the ingredients are composed of the following components in mass percentage:

[0007] Water-based alkyd resin 5%-15%

[0008] Water-based silicone resin 5%-15%

[0009] Water-based polyurethane resin 3%-5%

[0010] Modified nano composite liquid 3%-8%

[0011] Phosphoric acid complex salt 8-15%

[0012] Ammonium molybdate 1-2%

[0013] Ammonium tungstate 1-2%

[0014] Aqueous titanate chelate 3-5%

[0015] Flame retardant 3-6%

[0016] Dispersant 0.5-2%

[0017] The balance is water.

[0018] Preferably, the modified nanocomposite liquid is prepared according to the following steps:

[0019] S1, 50 parts of anhydrous ethanol (industrial grade) is added to 50 parts of nanosilica sol (solid content 30.0wt%; density 1.21g / mL; particle size 10nm; pH 9.8; viscosity 10.0cp) by weight fraction, heated to 30-40℃, and ultrasonic dispersion is carried out for 10-20 minutes at constant temperature;

[0020] S2, 5% of hexamethyl disiloxane, 2.5% of sorbitan fatty acid ester, and 2.5% of polyvinylpyrrolidone based on the total weight of nanosilica sol are sequentially added to the system obtained in step S1, heated to 50-60℃, and ultrasonic dispersion is carried out for 1-2 hours at constant temperature to obtain a modified nanocomposite liquid, which is reserved after standing for 48h.

[0021] Preferably, the phosphoric acid complex salt is prepared as follows:

[0022] Phosphoric acid (analytical pure) and aluminum hydroxide (analytical pure) are mixed in a molar ratio of 3.3-3.4:1, heated to 90-100℃, and reacted at constant temperature until a viscous transparent state is obtained, to obtain a phosphoric acid complex salt, which is cooled to room temperature for use.

[0023] Preferably, the flame retardant is at least one of aluminum hydroxide, ammonium phosphate, and ammonium polyphosphate.

[0024] Preferably, the dispersant is at least one of polyethylene glycol and polyethyleneimine.

[0025] The preparation method of the high-pressure-resistant flame-retardant insulating coating liquid for lithium battery shells according to the present application comprises the following steps:

[0026] Step 1: weigh each component by mass percentage;

[0027] Step 2: add water-based alkyd resin, water-based silicone resin into water in sequence, heat to 40-60℃ in water bath, constant temperature stirring for 1.5-2.5h; then add water-based polyurethane resin, flame retardant, dispersant in sequence; continue constant temperature stirring for 1-2h;

[0028] Step 3: add modified nanocomposite liquid, phosphoric acid composite salt, ammonium molybdate, ammonium tungstate, water-based titanate chelate into step 2 in sequence, constant temperature stirring for 1.5-2.5h, then heat to 90-95℃, constant temperature stirring for 7.5-8.5h;

[0029] Step 4: cool the solution in the reaction container to room temperature, stand for 30-35min, then the high-pressure resistant flame-retardant insulating coating liquid for lithium battery shell is obtained.

[0030] The high-pressure resistant flame-retardant insulating coating liquid for lithium battery shell of the application can be used in lithium battery shell.

[0031] Compared with the prior art, the beneficial effects of the application are reflected in:

[0032] (1) The modified nanocomposite liquid prepared by the nanometer modification technology and ammonium tungstate can have synergistic effect to improve the corrosion resistance of the coating;

[0033] (2) The high-pressure resistant flame-retardant system of alkyd resin-modified nanocomposite liquid is formed by the material compounding technology and surface modification technology, with water-based alkyd resin and water-based silicone resin as base material, water-based polyurethane resin as crosslinking agent, modified nanocomposite liquid, phosphoric acid composite salt, water-based titanate chelate and the like as reinforcing agent of the coating.

[0034] (3) The coating formed on the surface of the aluminum alloy substrate by the high-pressure resistant flame-retardant insulating coating liquid has a thickness of 80-100μm, a breakdown voltage of 7000V, a flame retardant grade of V-0 level, a corrosion resistance of 1000h (NSS), an adhesion of 0 level, and a heat resistance of 800℃.

[0035] (4) The application overcomes the problems of low pressure resistance, poor adhesion, poor heat resistance and poor corrosion resistance of the existing insulating coating. The high-pressure resistant flame-retardant insulating coating liquid obtained by the application can be widely used in various insulating facilities, new energy, aerospace equipment, military equipment, high-tech equipment and the like, and has good application and promotion prospect. DETAILED DESCRIPTION

[0036] The application will be described in detail below with reference to the examples, which illustrate the features and advantages of the application. The following examples are not a limitation of the application, and the formula prepared by the skilled in the art according to the idea and raw material ratio of the application also belongs to the protection scope of the application.

[0037] The coating liquid obtained in the following examples was used to form a coating on the surface of an aluminum alloy plate according to the following method.

[0038] An aluminum alloy plate (100*120*0.3mm) was selected, perforated, and used as a hanging template. The surface was polished to a bright finish and cleaned with acetone. After drying in a 100°C oven for 30 minutes, the plate was placed in a desiccator. Before processing, the plate was cleaned with toluene or xylene-ethanol (mass ratio 1:1) and dried.

[0039] The treated aluminum alloy plate was placed in a high-pressure flame-retardant insulating coating liquid for lithium battery cases, left at room temperature (25°C) for 3 minutes, removed, and hung vertically for 30 minutes. The remaining paint was carefully scraped off with a spatula, and the sample was placed in a 120°C oven and dried for 30 minutes.

[0040] The performance test method (or standard) for the coating formed on the surface of the aluminum alloy by the coating liquid obtained in the following examples is as follows:

[0041] Coating thickness detection standard: Determination of the film thickness of pigmented and clear coatings GB / T 13452.2-2008.

[0042] Coating breakdown voltage detection standard: Insulating materials - Determination of the electric strength - Part 1: Test at power frequency GB / T 1408.1-2016.

[0043] Coating flame-retardant grade detection: Standard test methods for flame retardancy of plastics UL94.

[0044] Coating corrosion resistance detection: Determination of the resistance to neutral salt spray of pigmented and clear coatings GB / T 1771-1991.

[0045] Coating adhesion detection: Cross-hatch adhesion test for pigmented and clear coatings GB / T 9286-2021.

[0046] Coating heat resistance detection: Determination of the heat resistance of pigmented and clear coatings GB / T 1735-2009.

[0047] The sources of the raw materials used in the following examples are as follows:

[0048] Example 1

[0049] A high-pressure flame-retardant insulating coating liquid for lithium battery cases, wherein the raw materials are composed of, by mass percentage: 15% water-based alkyd resin, 14% water-based silicone resin, 5% water-based polyurethane resin, 7% modified nano-composite liquid, 13% phosphoric acid complex salt, 2% ammonium molybdate, 2% ammonium tungstate, 5% water-based titanate chelate, 3% aluminum hydroxide, 2.5% ammonium phosphate, 0.5% polyethylene glycol, and 1% polyethyleneimine, with the balance being water.

[0050] The modified nanocomposite liquid in this example is prepared according to the following steps:

[0051] S1: 50 parts of anhydrous ethanol (industrial grade) is added to 50 parts of nanometer silicon sol (solid content 30.0wt%; density 1.21 g / mL; particle size 10 nm; pH 9.8; viscosity 10.0 cp) by weight fraction, heated to 40°C, and ultrasonic dispersion is carried out at constant temperature for 20 minutes;

[0052] S2: 5% of hexamethyl disiloxane, 2.5% of sorbitol anhydride fatty acid ester, and 2.5% of polyvinylpyrrolidone based on the total weight of the nanometer silicon sol are sequentially added to the system obtained in step S1, heated to 60°C, and ultrasonic dispersion is carried out at constant temperature for 2 hours to prepare the modified nanocomposite liquid. After standing for 48 h, it is ready for use.

[0053] The phosphoric acid complex salt in this example is prepared according to the following method:

[0054] A mixture of phosphoric acid (analytical pure) and aluminum hydroxide (analytical pure) (molar ratio 3.4:1) is placed in a beaker, heated to 100°C, and reacted at constant temperature until the beaker shows a viscous transparent state, obtaining the phosphoric acid complex salt, which is cooled to room temperature for standby.

[0055] The high-pressure resistant flame-retardant insulating coating liquid for lithium battery shell in this example is prepared according to the following steps:

[0056] Step 1: weigh each component by mass percentage;

[0057] Step 2: sequentially add the water-based alkyd resin, water-based silicone resin into water, and heat to 60°C in a water bath, and stir at constant temperature and low speed (50 rpm) for 2 h; then sequentially add the water-based polyurethane resin, flame retardant (aluminum hydroxide, ammonium phosphate), dispersant (polyethylene glycol, polyethyleneimine), and continue to stir at constant temperature and low speed (50 rpm) for 1.5 h.

[0058] Step 3: sequentially add the modified nanocomposite liquid, phosphoric acid complex salt, ammonium molybdate, ammonium tungstate, and water-based titanate chelate to step 2, stir at constant temperature and high speed (2000 rpm) for 2 h, then heat to 90°C, and stir at constant temperature and low speed (50 rpm) for 8 h.

[0059] Step 4: cool the solution in the reaction vessel to room temperature, and stand for 30 min to obtain the high-pressure resistant flame-retardant insulating coating liquid for lithium battery shell.

[0060] Example 2

[0061] A high-pressure resistant flame-retardant insulating coating solution for lithium battery shell, each raw material of which is composed of 5.5% water-based alkyd resin, 6% water-based silicone resin, 5% water-based polyurethane resin, 4% modified nano composite liquid, 15% phosphoric acid composite salt, 2% ammonium molybdate, 1.5% ammonium tungstate, 3% water-based titanate chelate, 1.5% aluminum hydroxide, 1.5% ammonium polyphosphate, 0.3% polyethylene glycol, 0.4% polyethyleneimine, and the balance is water.

[0062] The preparation method of the modified nano composite liquid, the phosphoric acid composite salt and the high-pressure resistant flame-retardant insulating coating solution for lithium battery shell in this embodiment is the same as that in Embodiment 1.

[0063] Embodiment 3

[0064] A high-pressure resistant flame-retardant insulating coating solution for lithium battery shell, each raw material of which is composed of 10% water-based alkyd resin, 11% water-based silicone resin, 3% water-based polyurethane resin, 5% modified nano composite liquid, 8% phosphoric acid composite salt, 1% ammonium molybdate, 2% ammonium tungstate, 4% water-based titanate chelate, 1.5% aluminum hydroxide, 3% ammonium polyphosphate, 0.5% polyethylene glycol, 0.6% polyethyleneimine, and the balance is water.

[0065] The preparation method of the modified nano composite liquid, the phosphoric acid composite salt and the high-pressure resistant flame-retardant insulating coating solution for lithium battery shell in this embodiment is the same as that in Embodiment 1.

[0066] Comparative Example 1

[0067] The components of the coating solution configured in this embodiment are the same as those in Embodiment 1, and the only difference is that the modified nano composite liquid is 0.

[0068] Comparative Example 2

[0069] The components of the coating solution configured in this embodiment are the same as those in Embodiment 1, and the only difference is that the water-based polyurethane resin is 0.

[0070] Comparative Example 3

[0071] The components of the coating solution configured in this embodiment are the same as those in Embodiment 1, and the only difference is that the water-based titanate chelate is 0.

[0072] Comparative Example 4

[0073] The components of the coating solution configured in this embodiment are the same as those in Embodiment 1, and the only difference is that the ammonium tungstate is 0.

[0074] The coating performance test results of the coating solutions configured in the above embodiments and comparative examples on the surface of the aluminum alloy plate are shown in Table 1.

[0075] Table 1 Coating performance test results

[0076] The coating performance test results of the coating solutions configured in the above embodiments and comparative examples on the surface of the aluminum alloy plate are shown in Table 1.

[0077] According to Table 1, the coating layer formed on the surface of the aluminum alloy by the coating liquid of Example 1 to Example 3 has a breakdown voltage of 6900V or more, and a flame retardancy of V-0 level, and has excellent high voltage resistance, flame retardancy, corrosion resistance, heat resistance and the like. As can be seen from Example 1 and Comparative Example 1, the modified nano-composite liquid selected in the present application can improve the corrosion resistance and heat resistance of the coating layer. As can be seen from Example 1 and Comparative Example 2, the water-based polyurethane resin selected in the present application can improve the voltage resistance of the coating layer. As can be seen from Example 1 and Comparative Example 3, the water-based titanate chelate selected in the present application can improve the adhesion of the coating layer. As can be seen from Example 1 and Comparative Example 4, the ammonium tungstate selected in the present application can improve the corrosion resistance of the coating layer.

[0078] It will be obvious to a person skilled in the art that, without departing from the spirit or essential characteristics of the application, the present application can be implemented in other specific forms. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0079] Furthermore, it should be appreciated that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the present specification is described in this way only for the sake of clarity, and a person skilled in the art should consider the present specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by a person skilled in the art.

Claims

1. A high-pressure resistant flame-retardant insulating coating solution for a lithium battery case, characterized by comprising: a water-soluble polymer; a water-soluble inorganic salt; and a water-soluble organic compound. The raw materials are composed of the following components by mass percentage: Water-based alkyd resin 5%-15% Water-based silicone resin 5%-15% Water-based polyurethane resin 3%-5% Modified nano-composite liquid 3%-8% Phosphoric acid composite salt 8%-15% Ammonium molybdate 1%-2% Ammonium tungstate 1%-2% Water-based titanate chelate 3%-5% Flame retardant 3%-6% Dispersant 0.5%-2% The balance is water. The modified nano-composite liquid is prepared according to the following steps: S1. According to the weight fraction, 50 parts of anhydrous ethanol is added to 50 parts of nano-silica sol, heated to 30-40℃, and ultrasonic dispersion is carried out at constant temperature for 10-20 minutes; S2. To the system obtained in step S1, 5% of hexamethyl disiloxane, 2.5% of sorbitol anhydride fatty acid ester, and 2.5% of polyvinylpyrrolidone based on the total weight of the nano-silica sol are added in sequence, heated to 50-60℃, and ultrasonic dispersion is carried out at constant temperature for 1-2 hours to obtain a modified nano-composite liquid, which is reserved after standing for 48 hours; The phosphoric acid composite salt is prepared by mixing phosphoric acid and aluminum hydroxide in a molar ratio of 3.3-3.4:1, heating to 90-100℃, and reacting at constant temperature until a viscous transparent state is obtained, and then cooling to room temperature for use; The flame retardant is at least one of aluminum hydroxide, ammonium phosphate, and polyphosphoric acid ammonium.

2. The high-pressure resistant flame-retardant insulating coating solution for a lithium battery case according to claim 1, characterized by, The dispersant is at least one of polyethylene glycol and polyethylene imine.

3. A method for preparing the high-pressure resistant flame-retardant insulating coating solution for a lithium battery case according to any one of claims 1 to 2, characterized by, The method comprises the following steps: Step 1: weigh each component according to the mass percentage; Step 2: add the water-based alkyd resin and the water-based silicone resin to water in sequence, heat in a water bath to 40-60℃, and stir at constant temperature for 1.5-2.5 hours; then add the water-based polyurethane resin, the flame retardant, and the dispersant in sequence; continue to stir at constant temperature for 1-2 hours; Step 3: add the modified nano-composite liquid, the phosphoric acid composite salt, the ammonium molybdate, the ammonium tungstate, and the water-based titanate chelate to step 2 in sequence, stir at constant temperature for 1.5-2.5 hours, then heat to 90-95℃, and stir at constant temperature for another 7.5-8.5 hours; Step 4: cool the solution in the reaction container to room temperature, stand for 30-35 minutes, and then the high-pressure resistant flame-retardant insulating coating liquid for lithium battery shell is obtained.

4. The use of the high-pressure resistant flame-retardant insulating coating liquid for lithium battery shell according to any one of claims 1-2 in a lithium battery shell.

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