An aqueous electroplating solution for composite copper foil for battery current collector

Abstract

The application discloses a water electroplating solution for a composite copper foil for a battery current collector, and the electroplating solution formula comprises the following mass concentration components: copper sulfate pentahydrate 140-180 g / L, sulfuric acid 80-120 g / L, brightener 4-16 g / L, anti-folding plating agent 50-100 mg / L, leveling agent 1-3 g / L, stabilizer 0.5-3 g / L, and grain refiner 5-10 g / L, and the rest is DI pure water. The copper foil obtained through water electroplating has a smooth and bright surface, low porosity, low copper layer stress, and good bonding force with a base film, and can be applied to a battery current collector material.

Description

Technical Field

[0001] This invention relates to the field of materials electrochemistry, and more particularly to an aqueous electroplating solution for composite copper foil used as a battery current collector. Background Technology

[0002] Currently, copper foil is used as the negative electrode current collector in lithium batteries. Due to the high amount of copper used, the material cost is greatly affected by the price of copper. There are also bottlenecks in battery safety and energy density. As a result, power battery manufacturers have the motivation and demand to find new alternative materials for reasons such as cost, safety and energy density.

[0003] PET copper foil is a micron-sized composite copper foil with a "sandwich" structure. It has a "copper-polymer-copper" composite "sandwich" structure, with a 4.5μm thick PET / PP base film in the middle layer and outer layers each plated with 1μm thick copper. Figure 1 As shown. Therefore, from a structural perspective, compared to the current traditional 6μm lithium battery copper foil, PET copper foil replaces metallic copper with a lower-cost PET base film, thereby reducing the amount of copper used by 2 / 3, achieving the goal of reducing raw material costs and weight, and is expected to replace traditional copper foil to a certain extent.

[0004] The basic principle of PET copper foil production is to metallize PET using vacuum deposition, followed by electroplating to thicken the copper layer. Due to the smooth surface of PET, enhancing the adhesion between the copper layer and the PET film, and ensuring the uniformity and flatness of the electroplated copper layer, are key technical challenges. After vacuum deposition on the PET substrate, the seed layer may be uneven and not dense due to deposition yield and film stretching, resulting in numerous rough spots on the surface. Subsequent electroplating of the metal layer is also easily affected, producing many pinholes and pits. Under strong light, these pinhole-like areas appear as bright spots, hindering the application of PET composite copper foil in battery current collectors.

[0005] Currently, copper electroplating technology also suffers from a series of problems, such as low coating brightness and uneven adhesion. Patent CN103173811A describes a copper electroplating solution containing a compound with an -XSY- structure and an aliphatic semialdehyde, where X and Y are atoms independently selected from the group consisting of hydrogen, carbon, sulfur, nitrogen, and oxygen, and X and Y are only identical when they are carbon atoms. This plating solution is prone to precipitation and produces a coating with poor brightness. Furthermore, patent CN113502512A discloses an electroplating solution comprising... ，The additives in the copper plating solution include 1-10 parts of accelerator, 150-300 parts of inhibitor, and 1-20 parts of leveling agent. The accelerator is sodium polydithiopropane sulfonate, the inhibitor is any one or a combination of several of polyethylene glycol-6000, polyethylene glycol-8000, and polyethylene glycol-10000 in any proportion, and the leveling agent is 5-amino-1,3,4-thiadiazole-2-thiol. This leveling agent is inexpensive, has low toxicity, and is stable, but the plating solution obtained by this method also has problems such as high porosity. Summary of the Invention

[0006] To address the shortcomings of the aforementioned technologies, this invention provides an electroplating solution for composite copper foil used in battery current collectors. The copper foil obtained after electroplating has a smooth, bright, and delicate surface, low porosity, low copper layer stress, and good adhesion to the base film, making it suitable for use in battery current collector materials.

[0007] To achieve the above objectives, this invention provides an aqueous electroplating solution for composite copper foil used in battery current collectors. The electroplating solution formulation comprises the following components by mass concentration: copper sulfate pentahydrate 140-180 g / L, sulfuric acid 80-120 g / L, brightener 4-16 g / L, anti-bending agent 50-100 mg / L, leveling agent 1-3 g / L, stabilizer 0.5-3 g / L, grain refiner 5-10 g / L, with the balance being DI pure water. The controlled temperature is 25-35℃, and the flow rate is 0.5-4.5 A / dm³. 2 .

[0008] The brightening agent is a composition of sodium 3-(benzothiazole-2-mercapto)-propanesulfonate and sodium 2-mercaptobenzimidazole-5-sulfonate, wherein the mass concentration ratio during use is 3:1, with sodium 3-(benzothiazole-2-mercapto)-propanesulfonate at 3-12 g / L and sodium 2-mercaptobenzimidazole-5-sulfonate at 1-4 g / L.

[0009] The anti-friction plating agent is a composition of sodium saccharin and sodium ethylenediamine di-o-phenylacetate, with a mass concentration ratio of 1:1 during use. Its main function is to reduce plating stress, make the copper foil plating layer flat and not curled, and at the same time improve the adhesion of the plating layer to prevent peeling from the substrate due to excessive stress.

[0010] The leveling agent is p-aminoazophenyl-4-sulfonic acid and sodium 2-phenylindole-5-sulfonate, with a mass concentration ratio of 1:2 to 1:5 during use. The p-aminoazophenyl-4-sulfonic acid is 0.5 g / L and the sodium 2-phenylindole-5-sulfonate is 0.5-2.5 g / L, which can effectively improve the tolerance to substrate roughness and improve the smoothness of the coating.

[0011] The stabilizer is ethoxy-α-naphthol sulfonic acid, which can prevent the additive components from being oxidized and decomposed too quickly during use, thereby improving the stability and service life of the plating solution.

[0012] The grain refiner is a composition of 1-piperazine carboxamide and sodium N,N-dimethyldithiocarbonylpropanesulfonate, with a mass concentration ratio of 1:1 during use. It refines the grains of the coating and ensures that the coating is free of pinholes, pits, and other roughness.

[0013] The beneficial effects of this invention are as follows: Compared with the prior art, this invention provides an aqueous electroplating solution for composite copper foil used in battery current collectors, which has the following advantages:

[0014] 1) To address the adverse effects of some pores and impurities on the appearance of the subsequent electroplated thick layer after vacuum plating the seed layer on PET substrate, an anti-bending agent and a grain refiner were added to the traditional electroplating additive formula. This resulted in low stress in the electroplated thick layer, achieving better gloss and leveling properties under extremely thin thickness conditions, and the coating was free of pinholes, pits, and other roughness defects.

[0015] 2) In response to the characteristics of continuous large-area electroplating of PET composite copper foil, a stabilizer is added to the new formula to effectively delay the decomposition and failure of additives and increase the service life of the electroplating solution by more than 30%.

[0016] 3) This application uses a combination of indolesulfonic acid compounds and azophenylsulfonic acid compounds to improve the defects of uneven plating and current distribution caused by traditional single quaternary ammonium salt compounds as leveling agents. At the same time, it can effectively improve the tolerance to substrate roughness and improve the smoothness of the coating.

[0017] 4) The brightener used in this application is a composition of sodium 3-(benzothiazole-2-mercapto)-propanesulfonate and sodium 2-mercaptobenzimidazole-5-sulfonate. This composition can improve the problem of the current density distribution of the plating layer being affected by the interference of battery fluid in the traditional electroplating layer. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a PET composite copper foil sandwich structure.

[0019] Figure 2 This is a microscope image of the PET copper foil after electroplating in Example 1;

[0020] Figure 3 This is a microscope image of the PET copper foil after electroplating in Example 2;

[0021] Figure 4 This is a microscope image of the PET copper foil after electroplating in Example 3;

[0022] Figure 5This is a microscope image of PET copper foil after electroplating, for comparison. Detailed Implementation

[0023] To more clearly illustrate the present invention, the invention will be further described below in conjunction with the accompanying drawings and description.

[0024] To achieve the above objectives, this invention provides an aqueous electroplating solution for composite copper foil used in battery current collectors. The electroplating solution formulation comprises the following components by mass concentration: copper sulfate pentahydrate 140-180 g / L, sulfuric acid 80-120 g / L, brightener 4-16 g / L, anti-bending agent 50-100 mg / L, leveling agent 1-3 g / L, stabilizer 0.5-3 g / L, grain refiner 5-10 g / L, with the balance being DI pure water. The controlled temperature is 25-35℃, and the flow rate is 0.5-4.5 A / dm³. 2 .

[0025] In this embodiment, the brightener is a composition of sodium 3-(benzothiazole-2-mercapto)-propanesulfonate and sodium 2-mercaptobenzimidazole-5-sulfonate, with a mass concentration ratio of 3:1 when used, wherein sodium 3-(benzothiazole-2-mercapto)-propanesulfonate is 3-12 g / L and sodium 2-mercaptobenzimidazole-5-sulfonate is 1-4 g / L.

[0026] In this embodiment, the anti-reflective plating agent is a composition of sodium saccharin and sodium ethylenediamine di-o-phenylacetate, with a mass concentration ratio of 1:1 during use.

[0027] In this embodiment, the leveling agent is p-aminoazophenyl-4-sulfonic acid and sodium 2-phenylindole-5-sulfonate, with a mass concentration ratio of 1:2 to 1:5 during use, where p-aminoazophenyl-4-sulfonic acid is 0.5 g / L and sodium 2-phenylindole-5-sulfonate is 0.5-2.5 g / L.

[0028] In this embodiment, the stabilizer is ethoxy-α-naphthol sulfonic acid.

[0029] In this embodiment, the grain refiner is a composition of 1-piperazine carboxamide and sodium N,N-dimethyldithiocarbonylpropane sulfonate, with a mass concentration ratio of 1:1 during use.

[0030] The beneficial effects of this invention are as follows: Compared with the prior art, this invention provides an aqueous electroplating solution for composite copper foil used in battery current collectors, which has the following advantages:

[0031] 1) To address the adverse effects of some pores and impurities on the appearance of the subsequent electroplated thick layer after vacuum plating the seed layer on PET substrate, an anti-bending agent and a grain refiner were added to the traditional electroplating additive formula. This resulted in low stress in the electroplated thick layer, achieving better gloss and leveling properties under extremely thin thickness conditions, and the coating was free of pinholes, pits, and other roughness defects.

[0032] 2) In response to the characteristics of continuous large-area electroplating of PET composite copper foil, a stabilizer is added to the new formula to effectively delay the decomposition and failure of additives and increase the service life of the electroplating solution by more than 30%.

[0033] 3) This application uses a combination of indolesulfonic acid compounds and azophenylsulfonic acid compounds to improve the defects of uneven plating and current distribution caused by traditional single quaternary ammonium salt compounds as leveling agents. At the same time, it can effectively improve the tolerance to substrate roughness and improve the smoothness of the coating.

[0034] 4) The brightener used in this application is a composition of sodium 3-(benzothiazole-2-mercapto)-propanesulfonate and sodium 2-mercaptobenzimidazole-5-sulfonate. This composition can improve the problem of the current density distribution of the plating layer being affected by the interference of battery fluid in the traditional electroplating layer.

[0035] Example 1

[0036] Copper sulfate pentahydrate 150 g / L, sulfuric acid 100 g / L, sodium 3-(benzothiazole-2-mercapto)-propanesulfonate 3 g / L, sodium 2-mercaptobenzimidazole-5-sulfonate 1 g / L, sodium saccharin 25 mg / L, sodium ethylenediamine di-o-phenylacetate 25 mg / L, p-aminoazophenyl-4-sulfonic acid 0.5 g / L, sodium 2-phenylindole-5-sulfonate 0.5 g / L, ethoxy-α-naphthol sulfonic acid 0.5 g / L, 1-piperazine carboxamide 2.5 g / L, sodium N,N-dimethyldithiocarbonylpropanesulfonate 2.5 g / L.

[0037] Current density 3A / dm 2 Time: 1.5 min, Temperature: 30℃.

[0038] Example 2

[0039] Copper sulfate pentahydrate 150 g / L, sulfuric acid 100 g / L, sodium 3-(benzothiazole-2-mercapto)-propanesulfonate 6 g / L, sodium 2-mercaptobenzimidazole-5-sulfonate 2 g / L, sodium saccharin 30 mg / L, sodium ethylenediamine di-o-phenylacetate 30 mg / L, p-aminoazophenyl-4-sulfonic acid 0.5 g / L, sodium 2-phenylindole-5-sulfonate 1 g / L, ethoxy-α-naphthol sulfonic acid 3 g / L, 1-piperazine carboxamide 5 g / L, sodium N,N-dimethyldithiocarbonylpropanesulfonate 5 g / L.

[0040] Current density 2A / dm 2 Time: 2.3 min, Temperature: 30℃

[0041] Example 3

[0042] Copper sulfate pentahydrate 150 g / L, sulfuric acid 100 g / L, sodium 3-(benzothiazole-2-mercapto)-propanesulfonate 12 g / L, sodium 2-mercaptobenzimidazole-5-sulfonate 4 g / L, p-aminoazophenyl-4-sulfonic acid 0.5 g / L, sodium 2-phenylindole-5-sulfonate 2.5 g / L, ethoxy-α-naphthol sulfonic acid 2.5 g / L, 1-piperazine carboxamide 3 g / L, sodium N,N-dimethyldithiocarbonylpropanesulfonate 3 g / L.

[0043] Current density 0.5 A / dm 2 Time: 10 minutes, Temperature: 30℃

[0044] Comparative Example

[0045] Copper sulfate pentahydrate 150 g / L, sulfuric acid 100 g / L, ethoxy-α-naphthol sulfonic acid 0.5 g / L.

[0046] Current density 3A / dm 2 Time: 1.5 min, Temperature: 30℃

[0047] The gloss level is rated as follows: glossy is excellent, semi-gloss is good, dark is poor, and black is very poor. The uniformity level is rated as follows: thickness deviation of 90% or more is excellent, 80%-89% is good, 70-79% is poor, and below 70% is very poor. The porosity is rated as follows: porosity less than or equal to 5% is excellent, 6-10% is good, 11-15% is poor, and 16-20% is very poor. The bonding strength level is rated as follows: no powder falling off when pasted with tape is excellent, a small amount of powder falling off is good, a large amount of powder falling off is poor, and flaky falling off is very poor.

[0048] The above experimental results show that the results obtained in the examples are excellent in terms of gloss, bonding strength, porosity, and uniformity, and the corresponding microscopic surface micrographs are as follows. Figure 2-4 Compared to the examples, the comparative examples lacked brighteners, grain refiners, leveling agents, and anti-reflective plating agents, resulting in poor gloss, poor adhesion, poor porosity, and poor uniformity. The corresponding microscopic surface images are shown below. Figure 5 .

[0049] The above-disclosed embodiments are merely examples of the present invention, but the present invention is not limited thereto. Any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. An electroplating solution for composite copper foil used as a battery current collector, characterized in that, The electroplating solution formulation includes the following components by mass concentration: copper sulfate pentahydrate 140-180 g / L, sulfuric acid 80-120 g / L, brightener 4-16 g / L, anti-reflective agent 50-100 mg / L, leveling agent 1-3 g / L, stabilizer 0.5-3 g / L, grain refiner 5-10 g / L, with the balance being DI pure water. The controlled temperature is 25-35℃, and the current density is 0.5-4.5 A / dm³. 2 ; The brightener is a composition of sodium 3-(benzothiazole-2-mercapto)-propanesulfonate and sodium 2-mercaptobenzimidazole-5-sulfonate, with a mass concentration ratio of 3:1 during use, wherein sodium 3-(benzothiazole-2-mercapto)-propanesulfonate is 3-12 g / L and sodium 2-mercaptobenzimidazole-5-sulfonate is 1-4 g / L; The anti-reflective plating agent is a composition of sodium saccharin and sodium ethylenediamine di-o-phenylacetate, with a mass concentration ratio of 1:1 during use. The leveling agent is sodium p-aminoazophenyl-4-sulfonic acid and sodium 2-phenylindole-5-sulfonate, with a mass concentration ratio of 1:2 to 1:5 during use, where the concentration of sodium p-aminoazophenyl-4-sulfonic acid is 0.5 g / L and the concentration of sodium 2-phenylindole-5-sulfonate is 0.5-2.5 g / L. The stabilizer is ethoxy-α-naphthol sulfonic acid; The grain refiner is a composition of 1-piperazine carboxamide and sodium N,N-dimethyldithiocarbonylpropane sulfonate, with a mass concentration ratio of 1:1 during use.

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