Preparation method of anti-salt spray erosion agent for 18650 lithium battery housing

Abstract

The invention discloses a preparation method and a usage method of an anti-salt spray erosion agent for the shell of 18650 lithium batteries. The raw material ratio is as follows: refined vegetable oleic acid 5-10%, triethanolamine 5-8%, sodium molybdate 0.5-1%, fatty alcohol polyoxyethylene ether acidic phosphate 3-5%, sodium salt of sulfuric acid mono(2-ethylhexyl) ester 0.1-0.5%, n-propanol 4-8%, dodecenyl succinic acid 0.5-1.5%, and deionized water is added to make up 100%. The main active components of the anti-salt spray erosion agent of the invention can interact with the shell of 18650 lithium batteries. The active components penetrate through the voids on the surface of the shell, adsorb and combine with metal atoms, and then form a firm protective film. This protective film will not fall off after being rinsed with pure water, and can pass the 8-hour salt spray test. After the test, the defect area grade of the shell of 18650 lithium batteries is not lower than grade 4. This anti-salt spray erosion agent is an environment-friendly product and does not contain substances such as chromate, nitrite, and phosphate.

Description

Technical Field

[0001] The present invention relates to the technical field of salt spray treatment for 18650 lithium battery casings, and particularly to a preparation method of a salt spray erosion inhibitor for 18650 lithium battery casings. Background Art

[0002] With the rapid development of the new energy industry, 18650 cylindrical lithium batteries are used more extensively due to their advantages such as large capacity, long life, small internal resistance, and high safety. However, compared with the production of general batteries, the production conditions for 18650 lithium batteries are more demanding. Especially during the period from battery casing production to final assembly into a finished battery, how to prevent the casing from being eroded by salt spray components in the air and corroding and rusting has become a major problem.

[0003] Relationship between the defect area S of the 18650 lithium battery casing salt spray test and the corrosion rating:

[0004] Grade 0: S > 50%; Grade 1: 25% - 50%; Grade 2: 10% - 25%; Grade 3: 5% - 10%; Grade 4: 2.5% - 5%; Grade 5: 1% - 2.5%; Grade 6: 0.5% - 1%; Grade 7: 0.25 - 0.5%; Grade 8: 0.1% - 0.25%; Grade 9: S ≤ 0.1%; Grade 10: No defect

[0005] Currently, water-based rust inhibitors are generally used for 18650 cylindrical lithium battery casings. Most of the water-based rust inhibitors mainly use nitrites, which will oxidize over time. Moreover, after the lithium battery casing is treated with a water-based rust inhibitor, due to its water solubility, it cannot pass the salt spray test, that is, the salt spray test is Grade 0. During the period from battery casing production to final assembly into a finished battery, the casing will be eroded by salt spray components in the air and corrode and rust. Summary of the Invention

[0006] To solve the problem that the existing 18650 cylindrical lithium battery casing treated with a water-based rust inhibitor cannot pass the salt spray test, and during the period from battery casing production to final assembly into a finished battery, the casing will be eroded by salt spray components in the air and corrode and rust, the present invention provides a preparation method of a salt spray erosion inhibitor for 18650 lithium battery casings. This erosion inhibitor can pass the 8-hour salt spray test, and the defect area grade of the 18650 lithium battery casing after the test is not lower than Grade 4, which can ensure that the 18650 lithium battery casing does not corrode and rust for at least 4 months before being assembled into a finished battery.

[0007] The technical solution of the present invention is realized as follows:

[0008] A preparation method of a salt spray erosion inhibitor for 18650 lithium battery casings, characterized by including the following steps:

[0009] S1. Prepare raw materials according to parts by mass:

[0010] Refined vegetable oleic acid: 5 - 10%;

[0011] Triethanolamine: 5 - 8%;

[0012] Sodium molybdate: 0.5 - 1%;

[0013] Fatty alcohol polyoxyethylene ether acidic phosphate: 3 - 5%;

[0014] Sodium salt of mono(2 - ethylhexyl) sulfate: 0.1 - 0.5%;

[0015] n - Propanol: 4 - 8%;

[0016] Dodecenylsuccinic acid: 0.5 - 1.5%;

[0017] Deionized water: make up to 100%;

[0018] S2. First, add 5 - 10% refined vegetable oleic acid and 5 - 8% triethanolamine into the reaction kettle, set the temperature of the reaction kettle to 60 - 80 °C, and carry out a mixing reaction to generate triethanolamine oleate. After the reaction is complete, add 20 - 30% deionized water and stir at a stirring speed of 50 r / min until a homogeneous and transparent emulsion is obtained;

[0019] S3. In the emulsion obtained in step S2, successively add 0.5 - 1% sodium molybdate, 3 - 5% fatty alcohol polyoxyethylene ether acidic phosphate, 0.1 - 0.5% sodium salt of mono(2 - ethylhexyl) sulfate, 4 - 8% n - propanol, 0.5 - 1.5% dodecenylsuccinic acid, and make up deionized water to 100%. After stirring until it becomes transparent, a salt - spray corrosion inhibitor is obtained. After cooling, it is filled into containers.

[0020] In the present invention, the sodium salt of mono(2 - ethylhexyl) sulfate mainly plays the roles of wetting and penetration to promote the interaction between other active ingredients and the surface of the battery case; the main role of sodium molybdate is to enter the metal pores of the battery case and carry out complexation, adsorption, etc. with metal atoms to fill the metal voids on the surface of the battery case and form the first protective layer; the main role of refined vegetable oleic acid and triethanolamine is to react to generate triethanolamine oleate that is not easily rinsed off, forming the second protective layer on the surface of the battery case. At the same time, both of them also have a certain role in adjusting the pH; the main role of dodecenylsuccinic acid is to form an oily film on the surface of the triethanolamine oleate protective layer to constitute the third protective layer and isolate the erosion of salt water; the main role of fatty alcohol polyoxyethylene ether acidic phosphate is to reduce the surface energy of the battery case, improve the surface smoothness of the battery case, and at the same time have a certain cleaning ability to remove mild oil stains on the surface of the battery case; the role of n - propanol is mainly solubilization.

[0021] As a further improvement of this technology, the stirring speed in step S2 and step S3 is set to 50 r / min.

[0022] As a further improvement of the present technology, the anti-salt spray erosion agent obtained in step S3 is a light yellow or yellow transparent liquid, with a pH of 8 - 9, a density of 1.05 ± 0.02 g / mL, and a salt spray corrosion rating of ≥ 4 levels after 8 hours.

[0023] The present invention also provides a usage method of the preparation method of the anti-salt spray erosion agent for the 18650 lithium battery case, which is characterized in that: the 18650 lithium battery case after the degreasing - pure water rinsing process is soaked with the anti-salt spray erosion agent for rust prevention treatment. The treatment temperature is 20 - 60 °C, the pH value is 8 - 9, the treatment time is 3 - 20 minutes. After the treatment is completed, a light yellow or yellow transparent protective film is formed on the surface of the lithium battery case, and then the lithium battery case is rinsed with deionized water and dried at a temperature of 50 - 80 °C.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The anti-salt spray erosion agent of the present invention can pass the 8-hour salt spray test. After the test, the defect area level of the 18650 lithium battery case is not lower than 4 levels, which can ensure that the 18650 lithium battery case does not corrode and rust for at least 4 months before being assembled into a finished battery; 2. After the anti-salt spray erosion agent of the present invention is used, the 18650 lithium battery case can be rinsed with pure water again to reduce the surface energy, thus being more conducive to the anti-salt spray erosion of the case. The reason is that the main active ingredient of the anti-erosion agent can interact with the 18650 lithium battery case. The active ingredient penetrates through the pores on the surface of the case, adsorbs and combines with metal atoms, and then forms a firm protective film. The protective film will not fall off after being rinsed with pure water; 3. The fatty alcohol polyoxyethylene ether acidic phosphate in the anti-salt spray erosion agent of the present invention has a mild cleaning function and can assist in removing a small amount of slightly residual oil stains that were not cleaned thoroughly in the previous aqueous cleaning process of the 18650 lithium battery case, thereby improving the cleanliness of the case; 4. The anti-salt spray erosion agent of the present invention will not affect the nickel plating layer on the surface of the 18650 lithium battery case and damage its performance; 5. The anti-salt spray erosion agent of the present invention is an environment-friendly product, does not contain substances such as chromate, nitrite, phosphate, etc., and is also harmless to the human body. Specific embodiments

[0025] The present invention will be described in detail below in conjunction with embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0026] Example 1:

[0027] A preparation method of an anti-salt spray erosion agent for an 18650 lithium battery case, which is characterized by including the following steps:

[0028] S1. Prepare raw materials by mass fraction: refined vegetable oleic acid 5%, triethanolamine 5%, sodium molybdate 0.5%, fatty alcohol polyoxyethylene ether acidic phosphate 3%, sodium salt of sulfuric acid mono(2-ethylhexyl) ester 0.1%, n-propanol 4%, dodecenyl succinic acid 0.5%, make up to 100% with deionized water;

[0029] S2. First, add 5% refined vegetable oleic acid and 5% triethanolamine into the reaction kettle, set the temperature of the reaction kettle to 65 °C, and carry out a mixing reaction to generate triethanolamine oleate. After the reaction is complete, add 20% deionized water and stir at a stirring speed of 50 r / min until a homogeneous and transparent emulsion is obtained;

[0030] S3. Sequentially add 0.5% sodium molybdate, 3% fatty alcohol polyoxyethylene ether acidic phosphate, 0.1% sodium salt of sulfuric acid mono(2-ethylhexyl) ester, 4% n-propanol, and 0.5% dodecenyl succinic acid to the emulsion obtained in step S2, and make up deionized water to 100%. After stirring until transparent, a salt spray corrosion inhibitor is obtained. After cooling, it is filled.

[0031] The obtained salt spray corrosion inhibitor is a light yellow transparent liquid, with a pH of 8 and a density of 1.05 ± 0.02 g / mL.

[0032] Immerse the 18650 lithium battery case after the degreasing - pure water rinsing process in the salt spray corrosion inhibitor prepared in Example 1 for rust prevention treatment. The treatment temperature is 20 °C, the pH value is 8, and the treatment time is 10 min. After the treatment is completed, a light yellow or yellow transparent protective film is formed on the surface of the lithium battery case. Then, rinse the lithium battery case with deionized water and dry it at 80 °C.

[0033] Conduct an 8-hour salt spray test on the 18650 lithium battery case after rust prevention treatment with the salt spray corrosion inhibitor of this example. After the test, the defect area grade of the 18650 lithium battery case is level 4.

[0034] Example 2:

[0035] A method for preparing a salt spray corrosion inhibitor for 18650 lithium battery cases, which is characterized by including the following steps:

[0036] S1. Prepare raw materials by mass fraction: refined vegetable oleic acid 10%, triethanolamine 8%, sodium molybdate 1%, fatty alcohol polyoxyethylene ether acidic phosphate 5%, sodium salt of sulfuric acid mono(2-ethylhexyl) ester 0.5%, n-propanol 8%, dodecenyl succinic acid 1.5%, make up to 100% with deionized water;

[0037] S2. First, add 10% refined vegetable oleic acid and 8% triethanolamine into the reaction kettle, set the temperature of the reaction kettle to 80 °C, and mix and react to produce triethanolamine oleate. After the reaction is complete, add 30% deionized water and stir at a stirring speed of 50 r / min until a uniform and transparent emulsion is obtained;

[0038] S3. Sequentially add 1% sodium molybdate, 5% fatty alcohol polyoxyethylene ether acidic phosphate ester, 0.5% sodium sulfate mono(2-ethylhexyl) ester, 8% n-propanol, and 1.5% dodecenyl succinic acid to the emulsion obtained in step S2, and make up deionized water to 100%. After stirring until transparent, an anti-salt spray corrosion inhibitor is obtained. After cooling, it is filled.

[0039] The obtained anti-salt spray corrosion inhibitor is a yellow transparent liquid, with a pH of 9 and a density of 1.05 ± 0.02 g / mL.

[0040] Use the anti-salt spray corrosion inhibitor prepared in Example 1 to soak the 18650 lithium battery case after the degreasing - pure water rinsing process for rust prevention treatment. The treatment temperature is 40 °C, the pH value is 9, and the treatment time is 10 min. After the treatment is completed, a light yellow or yellow transparent protective film is formed on the surface of the lithium battery case, and then the lithium battery case is rinsed with deionized water and dried at 80 °C.

[0041] The 18650 lithium battery case treated with the anti-salt spray corrosion inhibitor of this example is subjected to an 8-hour salt spray test. After the test, the defect area grade of the 18650 lithium battery case is grade 5.

[0042] Example 3:

[0043] A method for preparing an anti-salt spray corrosion inhibitor for an 18650 lithium battery case, which is characterized by including the following steps:

[0044] S1. Prepare raw materials by mass fraction: 8% refined vegetable oleic acid, 6.5% triethanolamine, 0.75% sodium molybdate, 4% fatty alcohol polyoxyethylene ether acidic phosphate ester, 0.3% sodium sulfate mono(2-ethylhexyl) ester, 6% n-propanol, 1% dodecenyl succinic acid, and make up deionized water to 100%;

[0045] S2. First, add 8% refined vegetable oleic acid and 6.5% triethanolamine into the reaction kettle, set the temperature of the reaction kettle to 70 °C, and mix and react to produce triethanolamine oleate. After the reaction is complete, add 25% deionized water and stir at a stirring speed of 50 r / min until a uniform and transparent emulsion is obtained;

[0046] S3. Sequentially add 0.75% sodium molybdate, 4% fatty alcohol polyoxyethylene ether acidic phosphate, 0.3% sodium bis(2-ethylhexyl) sulfate, 6% n-propanol, and 1% dodecenyl succinic acid to the emulsion obtained in step S2, and make up deionized water to 100%. After stirring until transparent, obtain the anti-salt spray corrosion agent, cool it and then fill it into containers.

[0047] The obtained anti-salt spray corrosion agent is a light yellow transparent liquid, with a pH of 9 and a density of 1.05 ± 0.02 g / mL.

[0048] Immerse the 18650 lithium battery case after the degreasing - pure water rinsing process in the anti-salt spray corrosion agent prepared in Example 1 for rust prevention treatment. The treatment temperature is 60°C, the pH value is 9, and the treatment time is 20 minutes. After the treatment is completed, a light yellow or yellow transparent protective film is formed on the surface of the lithium battery case. Then, rinse the lithium battery case with deionized water and dry it at 80°C.

[0049] Conduct an 8-hour salt spray test on the 18650 lithium battery case after rust prevention treatment with the anti-salt spray corrosion agent of this example. After the test, the defect area grade of the 18650 lithium battery case is grade 6.

[0050] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. Preparation method of anti - salt spray erosion agent for 18650 lithium battery shell, characterized in that It includes the following steps: S1. Prepare raw materials by mass fraction: Refined vegetable oleic acid: 5 - 10%; Triethanolamine: 5 - 8%; Sodium molybdate: 0.5 - 1%; Fatty alcohol polyoxyethylene ether acidic phosphate: 3 - 5%; Sodium bis(2-ethylhexyl) sulfate: 0.1 - 0.5%; n-Propanol: 4 - 8%; Dodecenylsuccinic acid: 0.5 - 1.5%; Deionized water: make up to 100%; S2. First, add 5 - 10% of refined vegetable oleic acid and 5 - 8% of triethanolamine into a reaction kettle, set the temperature of the reaction kettle at 60 - 80 °C, and carry out a mixing reaction to generate triethanolamine oleate. After the reaction is complete, add 20 - 30% of deionized water and stir at a stirring speed of 50 r / min until a uniform and transparent emulsion is obtained; S3. Sequentially add 0.5 - 1% of sodium molybdate, 3 - 5% of fatty alcohol polyoxyethylene ether acidic phosphate, 0.1 - 0.5% of sodium bis(2-ethylhexyl) sulfate, 4 - 8% of n-propanol, and 0.5 - 1.5% of dodecenylsuccinic acid into the emulsion obtained in step S2, and make up deionized water to 100%. After stirring until it is transparent, an anti-salt spray corrosion agent is obtained. After cooling, it is filled; The anti-salt spray corrosion agent obtained in step S3 is a light yellow or yellow transparent liquid, with a pH of 8 - 9, a density of 1.05 ± 0.02 g / mL, and a salt spray corrosion rating of ≥ 4 levels after 8 h; 2. The preparation method of the anti-salt spray erosion agent for the 18650 lithium battery housing according to claim 1, wherein: The stirring speed in step S2 and step S3 is set at 50 r / min; 3. A method for using the anti-salt spray erosion agent for the 18650 lithium battery case according to claim 1 or 2, characterized in that: Use the anti-salt spray corrosion agent to soak the 18650 lithium battery shell after the degreasing - pure water rinsing process for rust prevention treatment. The treatment temperature is 20 - 60 °C, the pH value is 8 - 9, the treatment time is 3 - 20 min. After the treatment is completed, a light yellow or yellow transparent protective film is formed on the surface of the lithium battery shell. Then, rinse the lithium battery shell with deionized water and dry it at a temperature of 50 - 80 °C.