Two-component copper foil passivator and use method thereof

Abstract

The invention relates to the technical field of copper foil surface treatment, in particular to a two-component copper foil passivator and a using method thereof. The copper foil passivator comprises a component A and a component B. The component A is a passivator and comprises 150-400 g / L of a chelating agent, 20-80 g / L of molybdate, 5-50 g / L of sodium formate and the balance water. The component B is a sealing agent and comprises 400-600 g / L of antioxidant organic acid, 25-50 g / L of a silane coupling agent, 5-50 g / L of a titanate coupling agent and the balance of water. The copper foil passivating agent can form a uniform passivating film on the surface of a base material, molybdate serves as a main film forming substance, copper is chelated through multiple chelating agents and antioxidants, copper is not prone to being oxidized, meanwhile, the oxidized copper can be rapidly reduced into elementary substance copper, and discoloration is relieved. And then silane and a titanate coupling agent are used for sealing the surface, so that oxygen cannot be in contact with metal, and the base material is prevented from being oxidized while the normal-temperature and high-temperature oxidation resistance, wettability and conductivity of the lithium battery copper foil are improved.

Description

Technical Field

[0001] The invention relates to the technical field of electrolytic copper foil surface treatment, and in particular to a two-component copper foil passivator and a use method thereof. Background Art

[0002] In the production process of electrolytic copper foil for lithium-ion batteries, anti-oxidation of copper foil is a very important process. Since the copper foil current collector is contaminated by external water vapor, dust, oxidation, and fingerprints during transportation, storage, and copper-clad board production operations, it will be sealed into the copper coil during the winding process, causing oxidation and discoloration on the surface of the copper foil. This not only affects the appearance of the copper foil, but more importantly, it affects the performance of the battery, such as increasing internal resistance, affecting conductivity, and reducing the mechanical properties of the material. As lithium battery copper foil customers have higher requirements for the quality of high-end battery products, a research has been conducted to obtain an environmentally friendly anti-oxidation process for electrolytic copper foil, which simultaneously improves the room temperature and high temperature oxidation resistance, conductivity, wettability, and mechanical properties of electrolytic copper foil, which is of great value.

[0003] There are various existing processes for chromium-free passivation of copper foil, including inorganic passivators and organic passivators. Inorganic passivators mainly use molybdates, tungstates, etc., which form a passivation film by coordinating with copper. Organic passivators coordinate with copper through organic groups such as heterocyclic rings in the solution to form a passivation film. However, the existing passivation process has problems such as local discoloration of copper foil after passivation, short anti-oxidation effective period, and easy discoloration at high temperature.

[0004] In order to solve the problems existing in the above-mentioned technology. The present invention provides a composite passivator using organic and inorganic materials, so that the copper foil has strong antioxidant properties after passivation. The composite passivator includes four functional agents: a film-forming agent, a chelating agent, an antioxidant, and a sealing agent. The passivation method can form a dense oxide film during the passivation process, which effectively improves the antioxidant capacity of the copper foil. Compared with the prior art, the present invention has the advantages of being environmentally friendly, having strong corrosion resistance and high durability. At the same time, because it is used in dilution, its processing cost will be greatly reduced, thereby improving the economic efficiency of the product. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a copper foil anti-oxidation passivation solution prepared with two components. The purpose is to provide a lithium battery copper foil with an antioxidant that has a good treatment time, good corrosion resistance, no discoloration after long-term placement, and high temperature resistance.

[0006] In order to achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0007] The invention provides a two-component environmentally friendly passivation solution for copper foil, comprising the following components in mass concentrations: agent A: chelating agent: 150-400 g / L,

[0008] Molybdate: 20~80g / L,

[0009] Sodium formate: 5-50g / L,

[0010] Water: balance;

[0011] Agent B: Antioxidant organic acid: 400~600g / L,

[0012] Silane coupling agent: 25-50g / L,

[0013] Titanate coupling agent: 25-50g / L,

[0014] Water: Balance.

[0015] In the above-mentioned copper foil chromium-free passivation solution, molybdate is the main film-forming substance, and a variety of chelating agents are compounded to control the discoloration of the copper foil. The silane coupling agent forms a Si-O-Si skeleton network with good density and forms a covalent connection with copper. However, since the conductivity of Si is much worse than that of copper, titanate is used as a supplement to the silane coupling agent to improve the bonding force while ensuring that the conductivity of the copper foil is not affected. The present invention uses organic coupling agents, chelating agents, and antioxidants to work synergistically with each other to form a dense inorganic-organic composite film with better high temperature resistance and longer daily storage time.

[0016] As a preferred embodiment, the chelating agent is one or more of EDTA2 sodium, EDTA4 sodium, sodium citrate, sodium potassium tartrate, and sodium gluconate. More preferably, it is one or more of EDTA2 sodium, sodium potassium tartrate, sodium citrate, and sodium gluconate.

[0017] In the present invention, the chelating agent in the passivating agent is compounded in multiple ways to achieve the best use effect. Potassium sodium tartrate is a commonly used complexing agent in electroplating technology, and can form soluble complexes with metal ions such as aluminum, beryllium, cadmium, cobalt, molybdenum, niobium, lead, nickel, palladium, platinum, rhodium, antimony, tin, tantalum, tungsten, zinc, copper, selenium, and tellurium. EDTA2 sodium is also a good complexing agent. Its six coordinated atoms can chelate metal ions in the solution to prevent discoloration and deterioration caused by metals. Therefore, the chelating agent in the present invention is preferably potassium sodium tartrate and EDTA for compounding, and the ratio is potassium sodium tartrate: EDTA2 sodium = 10:1~2.5:1, preferably 8:1~4:1, and more preferably 6:1~5:1. The usage is preferably 150~400g / L, and more preferably 250~300g / L.

[0018] Preferably, the molybdate is sodium molybdate, and the dosage of sodium molybdate is 30-70 g / L, and the dosage of sodium molybdate is 40-60 g / L.

[0019] In the present invention, the ratio of antioxidant organic acid salt to reducing salt in the passivating agent is preferably sodium formate: sodium citrate = 8:1-2:1, preferably 6:1-2.5:1, and more preferably 4:1-3:1. The amount of sodium formate is 5.50 g / L, further 10-40 g / L, and further 15-25 g / L. The amount of sodium citrate is preferably 3.5-8.5 g / L.

[0020] In the present invention, the organic carboxylic acid is one or more of citric acid, tartaric acid, gluconic acid, oxalic acid, ethylenediaminetetraacetic acid, and malic acid. More preferably, it is one or more of citric acid, malic acid, and tartaric acid. This is because these organic carboxylic acids have certain antioxidant capacity. Preferably, it is one or more of tartaric acid and citric acid. The dosage is 400-600 g / L, and more preferably 450-550 g / L.

[0021] In the present invention, the silane coupling agent is preferably one or more of 3-aminopropyltriethoxysilane, 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane or tetraethyl orthosilicate. Among the above-mentioned silane coupling agents, whether aminosilane or epoxysilane, after hydrolysis, redundant organic groups will be generated, which can provide certain corrosion resistance, but will also make the high temperature resistance of the treated copper foil worse, so tetraethyl orthosilicate (TEOS) is more preferred.

[0022] In the present invention, the titanate coupling agent is preferably di(triethanolamine) diisopropyl titanate (TE). Lactic acid chelated titanate (LA) has better water solubility, but the addition of lactic acid will reduce the high temperature resistance. In the present invention, the organic coupling agent TEOS:TE in the passivator is preferably 1.5:1-1:1.5, and more preferably 1:1.

[0023] In the present invention, deionized water is used to prepare a two-component copper foil antioxidant into a copper foil passivation working solution with a concentration of 3-5%.

[0024] The present invention also provides a method for using the environmentally friendly passivating agent for copper foil, comprising the following steps:

[0025] 1) Dissolve the passivator component A in 80% water at a ratio of 3-5%. After the passivator is completely dispersed, take the passivator component B and dissolve it in the aqueous solution of component A. Use pure water to make up the remaining amount of water. After stirring evenly, the copper foil passivation solution is obtained.

[0026] 2) The passivating agent prepared according to the above requirements is introduced into the passivation tank and the temperature is controlled between 20 and 40°C;

[0027] 3) Immerse the copper foil into the passivation tank through the guide roller, so that the copper foil is immersed in the passivating agent;

[0028] 4) The passivated copper foil is passed through a squeeze roller to remove the residual passivator on the surface, and then rolled up after hot air drying.

[0029] Preferably, the soaking temperature is 20-30°C.

[0030] Preferably, the soaking time is 3 to 8 seconds.

[0031] The beneficial effects of the present invention include the following:

[0032] 1) The passivator of the present invention is compounded with a variety of chelating agents, and can form a uniform polymer film on the surface of the electrolytic copper foil. The polymer film is stable and difficult to dissolve in a variety of solvents, has a good anti-corrosion protection effect, and improves the room temperature and high temperature oxidation resistance, wettability and conductivity of the electrolytic copper foil for lithium ion batteries. The passivator can well infiltrate the copper surface to prevent copper from being oxidized, has a strong chelating ability with copper, can also improve the roughness of the copper surface, and has good anti-peel strength.

[0033] 2) The passivating agent of the present invention can improve the appearance quality of copper foil, avoid the occurrence of corrupt bacteria in the tank liquid and organic scaling on the conductive roller and the extrusion roller after a period of use, which may cause appearance problems such as stripe color difference, embossing, black spots, etc. on the surface of the copper foil, and can prevent the copper foil from changing color for up to 6 months at room temperature.

[0034] 3) The invention reduces the probability of copper foil surface oxidation and the possibility of discoloration by adding antioxidant organic carboxylic acid, and at the same time uses silane coupling agent to seal the substrate surface, further reducing the possibility of substrate oxidation.

[0035] 4) The anti-oxidation process of the present invention is highly operable, does not require electricity, does not require water washing, and does not generate additional cleaning wastewater. It has the advantages of being green, safe and environmentally friendly. DETAILED DESCRIPTION

[0036] The present invention is described in detail below with reference to the embodiments.

[0037] In the following embodiments of the present invention, the method for passivating the copper foil comprises the following steps:

[0038] Step 1: Clean the surface of the copper material to be processed to remove the oil and the original oxide layer on the surface of the copper material;

[0039] Step 2: Soak the treated copper foil in the working solution for 3-5 seconds and then take it out;

[0040] Step 3: Take out the treated copper foil, squeeze it to remove the residual passivation agent on the surface, and then dry it with hot air to form a dense passivation film on the surface of the copper foil.

[0041] Dissolve the passivator component A in 80% water at a ratio of 3-5%. After the passivator is completely dispersed, take the passivator component B at a ratio of 3-5% and dissolve it in the aqueous solution of component A. Use pure water to make up the remaining water. After stirring evenly, the copper foil passivation solution used in step 2 is obtained.

[0042] The treated copper foil was tested for high temperature resistance and accelerated discoloration under hot and humid conditions.

[0043] 1) High temperature resistance test conditions: 140℃ / 15min;

[0044] 2) The wet heat test conditions are: 50℃ / 95RH%.

[0045] Example 1

[0046] Sodium potassium tartrate: 200 g / L, sodium EDTA2: 50 g / L, sodium molybdate: 45 g / L, sodium formate: 20 g / L, sodium citrate: 10 g / L were completely dissolved in water to prepare a passivation agent A;

[0047] Dissolve 400g / L of tartaric acid in water, then add 50g / L of TEOS. After stirring for a period of time to completely hydrolyze it, add 50g / L of TE. After the solution is completely hydrolyzed, passivation agent B is prepared.

[0048] Dissolve the passivator component A in 80% water at a ratio of 3-5%. After the passivator is completely dispersed, take the passivator component B at a ratio of 3-5% and dissolve it in the aqueous solution of component A. Use pure water to make up the remaining amount of water. After stirring evenly, the copper foil passivation working solution is obtained. Use this working solution to treat copper foil and examine the performance of the copper foil after passivation.

[0049] Example 2

[0050] Sodium potassium tartrate: 250 g / L, sodium EDTA2: 50 g / L, sodium molybdate: 50 g / L, sodium formate: 22.5 g / L, sodium citrate: 7.5 g / L were completely dissolved in water to prepare a passivation agent A;

[0051] 500 g / L of tartaric acid was dissolved in water, and then 20 g / L of TEOS was added. After stirring for a period of time to completely hydrolyze it, 20 g / L of TE was added. After the solution was completely hydrolyzed, a passivation agent B was prepared.

[0052] The working solution was prepared according to the method of Example 1 to treat the copper foil, and the performance of the copper foil after passivation was examined.

[0053] Example 3

[0054] Sodium potassium tartrate: 250 g / L, sodium EDTA2: 45 g / L, sodium molybdate: 60 g / L, sodium formate: 17 g / L, sodium citrate: 8.5 g / L were completely dissolved in water to prepare a passivation agent A;

[0055] Dissolve 450 g / L of tartaric acid in water, then add 25 g / L of TEOS. After stirring for a period of time to completely hydrolyze it, add 25 g / L of TE. After the solution is completely hydrolyzed, passivation agent B is prepared.

[0056] The working solution prepared according to the method of Example 1 was used to treat the copper foil, and the performance of the copper foil after passivation was examined.

[0057] Example 4

[0058] Sodium potassium tartrate: 200 g / L, sodium EDTA2: 50 g / L, sodium molybdate: 45 g / L, sodium formate: 20 g / L, sodium citrate: 10 g / L were completely dissolved in water to prepare a passivation agent A;

[0059] Dissolve 400 g / L of citric acid in water, then add 40 g / L of TEOS. After stirring for a period of time to completely hydrolyze it, add 40 g / L of TE. After the solution is completely hydrolyzed, passivation agent B is prepared.

[0060] The working solution prepared according to the method of Example 1 was used to treat the copper foil, and the performance of the copper foil after passivation was examined.

[0061] Example 5

[0062] Sodium potassium tartrate: 210 g / L, sodium EDTA2: 45 g / L, sodium molybdate: 50 g / L, sodium formate: 20 g / L, sodium citrate: 10 g / L were completely dissolved in water to prepare a passivation agent A;

[0063] Dissolve 250 g / L of tartaric acid and 300 g / L of citric acid in water respectively, then add 30 g / L of TEOS, stir for a period of time to completely hydrolyze it, then add 30 g / L of TE, and after the solution is completely hydrolyzed, prepare passivation agent B.

[0064] The working solution prepared according to the method of Example 1 was used to treat the copper foil, and the performance of the copper foil after passivation was examined.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is that in the passivation solution, EDTA2 sodium is replaced by potassium sodium tartrate.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 1 is that in the passivation solution, potassium sodium tartrate is replaced by EDTA2 sodium.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 2 is that in the passivation solution, the tartaric acid in agent B is replaced by malic acid.

[0071] Comparative Example 4

[0072] The difference between this comparative example and Example 2 is that sodium formate is removed from the passivation solution.

[0073] Comparative Example 5

[0074] The difference between this comparative example and Example 2 is that TEOS is used instead of TE in the passivation solution.

[0075] The copper foil performance test data of each embodiment and comparative example are shown in the following table:

[0076]

[0077]

[0078] It can be seen from the data of each embodiment that the copper foil passivator provided by the present invention has high stability, the formed passivation film can be stable at high temperature, and has outstanding wet heat effect, and is not easy to change color when placed at room temperature.

[0079] It can be seen from the comparative examples that the lack of potassium sodium tartrate or sodium EDTA2 will reduce the anti-oxidation function of the copper foil. The lack of sodium formate will reduce the stability of the bath solution and cause corruption, while the increase of TEOS will reduce the stability of the bath solution and cause gelation.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A two-component copper foil passivator, characterized in that: The copper foil antioxidant contains two components, A and B. Component A is: chelating agent: 150-400 g / L, molybdate: 20-80 g / L, sodium formate: 5-50 g / L, and the balance is water; Component B is: antioxidant organic acid: 400-600 g / L, silane coupling agent: 25-50 g / L, titanate coupling agent: 25-50 g / L, and the balance is water.

2. A two-component copper foil passivator according to claim 1, characterized in that: The chelating agent is one or more of EDTA2 sodium, EDTA4 sodium, sodium citrate, potassium sodium tartrate and sodium gluconate.

3. A two-component copper foil passivator according to claim 1, characterized in that: The molybdate is sodium molybdate or ammonium molybdate.

4. A two-component copper foil passivator according to claim 1, characterized in that: The organic acid is one or more of citric acid, tartaric acid, gluconic acid, oxalic acid, ethylenediaminetetraacetic acid and malic acid.

5. A two-component copper foil passivator according to claim 1, characterized in that: The silane coupling agent is one or more of 3-aminopropyltriethoxysilane, 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane or ethyl orthosilicate.

6. A two-component copper foil passivator according to claim 1, characterized in that: The titanate coupling agent is selected from chelated titanate compatible with water, preferably di(triethanolamine) diisopropyl titanate, lactic acid chelated titanate or one or more thereof.

7. A copper foil passivation working solution, characterized in that: The two-component copper foil passivator according to any one of claims 1 to 6 is prepared into an aqueous solution, and after uniform mixing, a copper foil passivation working solution is obtained, wherein the mass concentration of component A in the copper foil passivation working solution is 3-5%, and the mass concentration of component B in the copper foil passivation working solution is 3-5%.

8. A method for treating copper foil using the copper foil passivation working solution according to claim 7, characterized in that: The following steps are involved: 1) introducing the copper foil passivation working solution of claim 7 into a passivation tank and controlling the temperature between 20 and 40° C.; 2) The cleaned copper foil is immersed in the passivation tank through a guide roller, so that the copper foil is immersed in the passivation working solution; 3) The passivated copper foil is passed through a squeeze roller to remove the residual passivator on the surface, and then rolled up after hot air drying.

9. The method according to claim 8, characterized in that In step 2), the time of immersion in the passivation working solution is 3 to 5 seconds.

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