A Chromium-Free Passivating Agent and Its Application

Abstract

This invention discloses a chromium-free passivating agent and its application. The chromium-free passivating agent, by weight, comprises: 5-35 parts film-forming agent, 1-20 parts inorganic salt, 1-8 parts coordination agent, 0.1-5 parts additive, 0.5-8 parts corrosion inhibitor, 0.5-10 parts oxidant, 1-15 parts surfactant, and the balance being water. The chromium-free passivating agent prepared by this invention not only improves the oxidation resistance of the copper foil passivation film but also enhances its corrosion resistance and high-temperature resistance. The chromium-free passivating agent prepared by this invention contains no chromium, is environmentally friendly, has a simple preparation process, and can be used for mass production.

Description

Technical Field

[0001] This invention relates to the field of corrosion protection and environmental protection technology, classified under C23C22 / 52, and specifically to a chromium-free passivating agent and its application. Background Technology

[0002] The final step in the processing of copper foil for lithium batteries is passivation, which prevents oxidation of the copper foil surface and increases its shelf life. Simultaneously, the passivation layer generally exhibits good performance in terms of hydrophilicity, high-temperature oxidation resistance, and adhesion strength to the negative electrode active material. Currently, a common method is to use chromic acid solution to generate a chromium oxide protective layer. However, hexavalent chromium is a potent carcinogen, posing serious harm to the environment and human health; and chromium-free passivation processes for copper foil are relatively rare in domestic research. Therefore, developing and researching chromium-free passivation technology is an innovation in metal passivation technology, a key focus and hot topic in current surface technology research, and a necessity for promoting green industrial technologies and protecting the environment.

[0003] Chinese patent CN103789757A discloses a chromium-free passivating agent for copper and its application method. The chromium-free passivating agent, prepared by benzotriazole, imidazoline corrosion inhibitor, phytic acid and other components, greatly improves the salt spray resistance of copper. However, its application field is not copper foil for lithium batteries, and it does not solve the problem of the oxidation resistance of copper foil under high temperature conditions.

[0004] Chinese patent CN107604349A discloses a chromium-free passivation solution and its preparation method, as well as a method for passivating copper and copper alloys using it. The chromium-free passivation solution prepared by using 2-6g of benzotriazole, 2-8g of methylbenzotriazole, and 10-30mL of hydrogen peroxide has good corrosion resistance to the substrate and good salt spray resistance. Its application field is copper alloys, not copper foil for lithium batteries, and it does not solve the problem of copper's oxidation resistance under high temperature conditions. Summary of the Invention

[0005] To address the aforementioned problems, a first aspect of the present invention provides a chromium-free passivating agent, comprising, by weight: 5-35 parts film-forming agent, 1-20 parts inorganic salt, 1-8 parts coordination agent, 0.1-5 parts additive, 0.5-8 parts corrosion inhibitor, 0.5-10 parts oxidant, 1-15 parts surfactant, and the balance being water.

[0006] More preferably, the chromium-free passivating agent, by weight, comprises: 10-24 parts film-forming agent, 1.5-10 parts inorganic salt, 3-5 parts coordination agent, 1-5 parts additive, 1-4 parts corrosion inhibitor, 5-10 parts oxidant, 2-10 parts surfactant, and the balance being water.

[0007] More preferably, the chromium-free passivating agent, by weight, comprises: 18 parts film-forming agent, 4 parts inorganic salt, 4 parts coordination agent, 3 parts additive, 3 parts corrosion inhibitor, 8 parts oxidant, 8 parts surfactant, and the balance being water.

[0008] More preferably, the oxidant includes at least one of hydrogen peroxide, persulfate, sodium hypochlorite and sodium peroxide, and the mass ratio between the film-forming agent and the additive is (10-24):(1-5).

[0009] More preferably, the oxidant is hydrogen peroxide, and the mass ratio between the film-forming agent and the additive is 18:3.

[0010] Preferably, the film-forming agent includes at least one of waterborne acrylic resin, waterborne polyurethane resin, waterborne epoxy resin, water-soluble phenolic resin, and waterborne alkyd resin.

[0011] More preferably, the film-forming agent is an aqueous acrylic resin.

[0012] Preferably, the inorganic salt includes at least one of molybdate, fluorozirconate, and silicate.

[0013] More preferably, the inorganic salt is a mixture of molybdate and fluorozirconate.

[0014] Preferably, the inorganic salt is molybdate and fluorozirconate, with a mass ratio of (0.1-3):(1.5-3).

[0015] More preferably, the inorganic salt is molybdate and fluorozirconate, with a mass ratio of 1.5:2.5.

[0016] More preferably, the molybdate is ammonium molybdate, and the fluorozirconate is potassium fluorozirconate.

[0017] Preferably, the ligand comprises at least one of 2-mercaptobenzothiazole, ALPHA-methylbenzylaminobenzothiazole, potassium sodium tartrate, sodium oxalate, and sodium citrate.

[0018] More preferably, the ligand is ALPHA-methylbenzylaminobenzothiazole.

[0019] Preferably, the additive is a nano-silica sol dispersion with an average particle size of 1-20 nm.

[0020] More preferably, the additive is a nano-silica sol dispersion with an average particle size of 10-15 nm.

[0021] More preferably, the additive is a nano-silica sol dispersion with an average particle size of 12 nm.

[0022] Preferably, the corrosion inhibitor is at least one of imidazoline corrosion inhibitors, mercapto-containing heterocyclic compounds, sodium petroleum sulfonate, and thiourea.

[0023] More preferably, the corrosion inhibitor is an imidazoline-based corrosion inhibitor.

[0024] More preferably, the imidazoline corrosion inhibitor includes at least one of 2-methylimidazoline, 2-ethylimidazoline, 2-aminoethylheptadecylimidazoline, rosinylimidazoline, and oleic acid imidazoline.

[0025] More preferably, the imidazoline corrosion inhibitor is oleic acid imidazoline.

[0026] Preferably, the mass ratio of the ligand to the corrosion inhibitor is (3-5):(1-4). The applicant unexpectedly discovered that when the mass ratio of the ligand ALPHA-methylbenzylaminobenzothiazole and the corrosion inhibitor imidazoline oleate is (3-5):(1-4), the antioxidant properties of the copper foil passivation film are improved. The nitrogen atom in ALPHA-methylbenzylaminobenzothiazole can form covalent and coordinate bonds with the copper atoms of the copper foil, alternating to form a chain polymer. This creates a multi-layered protective film on the copper surface, enhancing the bond between the passivation layer and the copper foil. Oleic acid imidazoline has excellent adsorption capacity for the passivation film. Under the combined effect of these two components, the passivation film becomes denser and more uniform, greatly improving the oxidation resistance of the copper foil. Furthermore, the addition of aqueous acrylic resin and nano-silica sol dispersion causes cross-linking, forming a three-dimensional network of corrosion-inhibiting film that effectively blocks the diffusion channels of metal ions. The action of inorganic salts ammonium molybdate and potassium fluorozirconate, along with the oxidant hydrogen peroxide, further densifies the passivation film, ensuring a certain level of oxidation resistance while also improving the corrosion resistance and high-temperature resistance of the passivation film.

[0027] More preferably, the mass ratio between the ligand and the corrosion inhibitor is 4:3.

[0028] Preferably, the surfactant is sodium dodecyl sulfonate and / or hexadecyltrimethylammonium bromide.

[0029] More preferably, the surfactant is sodium dodecyl sulfonate.

[0030] The chromium-free passivating agent also includes the following preparation method: the film-forming agent, inorganic salt, ligand, additive, corrosion inhibitor, oxidant and surfactant are added to the reaction vessel in parts by weight, the stirring speed is 100-300 rpm / min and the stirring time is 1-2 h, and the chromium-free passivating agent is obtained.

[0031] A second aspect of the present invention provides the application of a chromium-free passivating agent on copper foil for lithium-ion batteries.

[0032] Dissolve 25-40 mL of passivation solution in 1 L of water, stir for 1-2 min, then immerse an 8-12 μm copper foil in the passivation solution for 8-12 s. Remove the foil, scrape off the liquid from the surface of the copper foil with a scraper, and let it air dry naturally.

[0033] Beneficial effects: This invention improves the oxidation resistance of the copper foil passivation layer by optimizing the mass ratio between the ligand and the corrosion inhibitor. Under the action of aqueous acrylic resin and nano-silica sol dispersion, the diffusion channels of metal ions are effectively blocked. At the same time, it works synergistically with inorganic salts ammonium molybdate and potassium fluorozirconate and oxidant hydrogen peroxide to improve the corrosion resistance and high temperature resistance of the passivation film while ensuring the oxidation resistance of the passivation layer. In addition, the chromium-free passivating agent prepared by this invention contains no chromium, is environmentally friendly, has a simple preparation process, and can be used for mass production. Attached Figure Description

[0034] Figure 1 Copper foil in Example 1 after 25 min of antioxidant performance test. Example

[0035] Example 1

[0036] A chromium-free passivating agent, by weight, comprises the following raw materials: 18 parts film-forming agent, 4 parts inorganic salt, 4 parts coordination agent, 3 parts additive, 3 parts corrosion inhibitor, 8 parts oxidant, 8 parts surfactant, and the balance being water.

[0037] The film-forming agent is an aqueous acrylic resin with a hydroxyl value of 4.2 mg / KOH / g, purchased from DSM, model NeocrylXK-540.

[0038] The inorganic salt is a mixture of ammonium molybdate and potassium fluorozirconate, with a mass ratio of 1.5:2.5.

[0039] The ligand is ALPHA-methylbenzylaminobenzothiazole, CAS number 105026-61-7.

[0040] The additive is a nano-silica sol dispersion with an average particle size of 12 nm, purchased from Grace in the United States, model HS-30.

[0041] The mass ratio between the film-forming agent and the additive is 18:3.

[0042] The corrosion inhibitor is imidazoline oleate, purchased from Qihang Biotechnology, CAS number 68052-47-1.

[0043] The mass ratio between ALPHA-methylbenzylaminobenzothiazole and oleic acid imidazoline is 4:3.

[0044] The oxidant is hydrogen peroxide.

[0045] The surfactant is sodium dodecyl sulfonate.

[0046] The chromium-free passivating agent also includes the following preparation method: the film-forming agent, inorganic salt, ligand, additive, corrosion inhibitor, oxidant and surfactant are added to the reaction vessel in parts by weight, the stirring speed is 200 rpm / min and the stirring time is 1.5 h, and the chromium-free passivating agent is obtained.

[0047] This embodiment also provides an application of a chromium-free passivating agent on copper foil for lithium-ion batteries.

[0048] Dissolve 35 mL of passivation solution in 1 L of water, stir for 1 min, immerse a 10 μm copper foil in the passivation solution for 10 s, remove it, scrape off the liquid on the surface of the copper foil with a scraper, and let it air dry naturally.

[0049] Example 2

[0050] A chromium-free passivating agent, by weight, comprises the following raw materials: 12 parts film-forming agent, 4 parts inorganic salt, 3 parts coordination agent, 5 parts additive, 1 part corrosion inhibitor, 8 parts oxidant, 10 parts surfactant, and the balance being water.

[0051] The film-forming agent is an aqueous acrylic resin with a hydroxyl value of 4.2 mg / KOH / g, purchased from DSM, model NeocrylXK-540.

[0052] The inorganic salt is a mixture of ammonium molybdate and potassium fluorozirconate, with a mass ratio of 1.5:2.5.

[0053] The ligand is ALPHA-methylbenzylaminobenzothiazole, CAS number 105026-61-7.

[0054] The additive is a nano-silica sol dispersion with an average particle size of 12 nm, purchased from Grace in the United States, model HS-30.

[0055] The mass ratio between the film-forming agent and the additive is 12:5.

[0056] The corrosion inhibitor is imidazoline oleate, purchased from Qihang Biotechnology, CAS number 68052-47-1.

[0057] The mass ratio between ALPHA-methylbenzylaminobenzothiazole and oleic acid imidazoline is 3:1.

[0058] The oxidant is hydrogen peroxide.

[0059] The surfactant is sodium dodecyl sulfonate.

[0060] The chromium-free passivating agent also includes the following preparation method: the film-forming agent, inorganic salt, ligand, additive, corrosion inhibitor, oxidant and surfactant are added to the reaction vessel in parts by weight, the stirring speed is 200 rpm / min and the stirring time is 1.5 h, and the chromium-free passivating agent is obtained.

[0061] This embodiment also provides an application of a chromium-free passivating agent on copper foil for lithium-ion batteries.

[0062] Dissolve 35 mL of passivation solution in 1 L of water, stir for 1 min, immerse a 10 μm copper foil in the passivation solution for 10 s, remove it, scrape off the liquid on the surface of the copper foil with a scraper, and let it air dry naturally.

[0063] Example 3

[0064] A chromium-free passivating agent, by weight, comprises: 24 parts film-forming agent, 4 parts inorganic salt, 5 parts coordination agent, 1 part additive, 4 parts corrosion inhibitor, 8 parts oxidant, 10 parts surfactant, and the balance being water.

[0065] The film-forming agent is an aqueous acrylic resin with a hydroxyl value of 4.2 mg / KOH / g, purchased from DSM, model NeocrylXK-540.

[0066] The inorganic salt is a mixture of ammonium molybdate and potassium fluorozirconate, with a mass ratio of 1.5:2.5.

[0067] The ligand is ALPHA-methylbenzylaminobenzothiazole, CAS number 105026-61-7.

[0068] The additive is a nano-silica sol dispersion with an average particle size of 12 nm, purchased from Grace in the United States, model HS-30.

[0069] The mass ratio of the film-forming agent to the additive is 24:1.

[0070] The corrosion inhibitor is imidazoline oleate, purchased from Qihang Biotechnology, CAS number 68052-47-1.

[0071] The mass ratio between ALPHA-methylbenzylaminobenzothiazole and oleic acid imidazoline is 4:3.

[0072] The oxidant is hydrogen peroxide.

[0073] The surfactant is sodium dodecyl sulfonate.

[0074] The chromium-free passivating agent also includes the following preparation method: the film-forming agent, inorganic salt, ligand, additive, corrosion inhibitor, oxidant and surfactant are added to the reaction vessel in parts by weight, the stirring speed is 200 rpm / min and the stirring time is 1.5 h, and the chromium-free passivating agent is obtained.

[0075] This embodiment also provides an application of a chromium-free passivating agent on copper foil for lithium-ion batteries.

[0076] Dissolve 35 mL of passivation solution in 1 L of water, stir for 1 min, immerse a 10 μm copper foil in the passivation solution for 10 s, remove it, scrape off the liquid on the surface of the copper foil with a scraper, and let it air dry naturally.

[0077] Comparative Example 1

[0078] The mass ratio of the complexing agent and the corrosion inhibitor was changed to 10:3, and the nano-silica sol dispersion was not added. The rest was the same as in Example 1.

[0079] Comparative Example 2

[0080] The particle size of the nano-silica sol dispersion was changed to 22 nm. It was purchased from Grace in the United States, model AS-40. The ligand ALPHA-methylbenzylaminobenzothiazole was replaced with potassium sodium tartrate. The rest was the same as in Example 1.

[0081] Comparative Example 3

[0082] The mass ratio of the complexing agent and the corrosion inhibitor was changed to 3:10, and the mass ratio of the film-forming agent and the additive was changed to 30:3. The rest was the same as in Example 1.

[0083] Performance Evaluation

[0084] (1) Antioxidant performance test: The passivated copper foil was placed in an air-circulating constant temperature chamber at 140°C. When the temperature of the constant temperature chamber rose back to the specified temperature, the timing was started, and the two sides of the double-sided copper foil were observed and recorded to see if there was oxidation and discoloration.

[0085] Table 1

[0086] Example 1 25 Example 2 23 Example 3 23 Comparative Example 1 12 Comparative Example 2 18 Comparative Example 3 16

Claims

1. A chromium-free passivating agent, characterized in that, The raw materials, by weight, include: 10-24 parts film-forming agent, 1.5-10 parts inorganic salt, 3-5 parts coordination agent, 1-5 parts additive, 1-4 parts corrosion inhibitor, 5-10 parts oxidant, 2-10 parts surfactant, and the balance being water; the film-forming agent is an aqueous acrylic resin; the inorganic salt is molybdate and fluorozirconate, with a mass ratio of (0.1-3):(1.5-3), the molybdate is ammonium molybdate, and the fluorozirconate is potassium fluorozirconate; the additive is a nano-silica sol dispersion with an average particle size of 1-20 nm; the mass ratio of coordination agent and corrosion inhibitor is (3-5):(1-4), the coordination agent is ALPHA-methylbenzylaminobenzothiazole; the corrosion inhibitor is an imidazoline corrosion inhibitor, and the imidazoline corrosion inhibitor is oleic acid imidazoline.

2. The chromium-free passivating agent according to claim 1, characterized in that, The surfactant is sodium dodecyl sulfonate and / or hexadecyltrimethylammonium bromide.

3. The application of the chromium-free passivating agent according to any one of claims 1-2 on copper foil of lithium-ion batteries.

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