Application of ionic liquid additive in electrolytic copper foil and preparation method of high tensile and high elongation electrolytic copper foil

Abstract

The application relates to application of an ionic liquid additive in electrolytic copper foil and a preparation method of high-tensile high-elongation electrolytic copper foil, and the structure of the ionic liquid additive is as follows: wherein R1 and R2 represent one of any alkyl groups; X represents one of H, -COOH, -SO3H, -PO3H, -NH2, -SH and -CN; and Y represents one of any anions. The ionic liquid additive prepared by directional synthesis is used to prepare an electrolyte, so that a synergistic promotion effect is generated with sulfuric acid and copper sulfate in the electrolyte. The additive can simultaneously improve the tensile strength and elongation of the copper foil, and reduce the surface roughness and average grain size of the copper foil under the direct current deposition process condition; the novel single ionic liquid additive can replace the traditional composite additive, so that the types and dosages of the additive are reduced, and the comprehensive performance of the copper foil is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrolytic copper foil preparation, and particularly relates to application of an ionic liquid additive in electrolytic copper foil and a preparation method of high-tensile high-elongation electrolytic copper foil. BACKGROUND

[0002] Ionic liquids have low vapor pressure, good thermal stability, high electrochemical stability, good conductivity and a wide electrochemical window, and thus have attracted more and more attention as a new generation of green solvents. Electrolytic copper foil, as the “nerve network” of electronic products, has become a functional basic raw material in the electronic manufacturing industry. With the rapid development of electric vehicles and smart phones, the demand for lithium ion batteries is increasing year by year. High-energy density and high-safety lithium ion batteries are currently in great demand and are a major problem that needs to be solved. As a core material in lithium ion batteries, the tensile strength of industrial lithium copper foil is generally 250 MPa to 300 MPa, and the elongation is 2.5% to 3%. It is difficult to meet the current demand for high-performance batteries. Therefore, the preparation of high-tensile high-elongation copper foil is the key to improving the quality of copper foil and meeting the application requirements of high-performance lithium ion batteries. In the current industrial production of electrolytic copper foil, in order to improve the quality and performance of copper foil, additives are usually added during electroplating.

[0003] Generally, additives are divided into accelerators, inhibitors and levelers, which are mostly compounds with heteroatoms (such as nitrogen, sulfur), polar functional groups and conjugated double bonds. They have strong coordination interactions with Cu 2+ Therefore, after adding a small amount of additives to the plating solution, the performance of the copper foil can be significantly improved. For example, gelatin, as a widely used leveler, can significantly increase the deposition overpotential of Cu 2+ , thereby preparing copper foil with compact structure and excellent performance. The current copper foil production additives in industrial applications are mainly composite additives, which exhibit good effects in reducing the surface roughness of copper foil and improving the ductility of copper foil. However, the composite additives have many types, large amount, complex preparation process, and the large amount of addition also causes the high cost of additives. SUMMARY

[0004] In view of the defects and deficiencies of the prior art, the application provides an application of an ionic liquid additive in electrolytic copper foil and a preparation method of high-tensile high-elongation electrolytic copper foil. The purpose is to replace the traditional composite additive with a new type of ionic liquid single additive to improve the production quality and performance of electrolytic copper foil, and to solve the problems of multiple types of additives, large amount of addition, and difficulty in simultaneously improving the tensile strength and elongation during the process production of electrolytic copper foil.

[0005] The application provides the application of the ionic liquid additive in electrolytic copper foil, and the ionic liquid additive has the following structure:

[0006]

[0007] Wherein, R1 and R2 represent one of any alkyl group; X represents one of -H, -COOH, -SO3H, -PO3H, -NH2, -SH and -CN; Y represents one of any anion.

[0008] Preferably, the ionic liquid additive comprises one of 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-aminopropyl-3-methylimidazolium chloride and 1-aminopropyl-3-methylimidazolium bromide.

[0009] Preferably, the method for preparing the electrolytic copper foil comprises the following steps:

[0010] (1) mechanically polishing the cathode titanium to obtain a reusable non-oxidized layer surface;

[0011] (2) adding copper sulfate pentahydrate and sulfuric acid into deionized water to configure a basic electrolyte;

[0012] (3) adjusting the temperature of the configured copper sulfate-sulfuric acid basic electrolyte;

[0013] (4) adding the copper sulfate-sulfuric acid basic electrolyte after temperature adjustment into an electrolytic tank, adding the ionic liquid additive into the electrolytic tank, stirring, fully mixing the additive and the basic electrolyte, and then starting direct current deposition on the titanium cathode, and keeping the current density at 40A / dm 2 ~ 80A / dm 2 to obtain the electrolytic copper foil with high tensile strength and high elongation.

[0014] Preferably, in the step (2), the Cu 2+ ion content in the basic electrolyte is 80g / L~150g / L, and the sulfuric acid content is 65g / L~110g / L.

[0015] Preferably, in the step (3), the temperature of the basic electrolyte is adjusted to 30℃~60℃.

[0016] Preferably, in the step (4), the concentration of the ionic liquid additive in the basic electrolyte is 10mg / L~50mg / L.

[0017] Preferably, the ionic liquid additive can improve the tensile strength and elongation of the electrolytic copper foil and reduce the surface roughness, the tensile strength of the electrolytic copper foil prepared by using the ionic liquid additive reaches 609.9 Mpa, the elongation reaches 17.1%, and the roughness reaches 2.655 mu m.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] 1. The present application introduces various special groups into ionic liquids, finds a new single ionic liquid additive that can replace traditional composite additives, reduces the types and amounts of additives, and comprehensively improves the performance of copper foil.

[0020] 2. The ionic liquid additive of the present application has good designability, can be designed according to the role in the preparation process of electrolytic copper foil, so that the single ionic liquid has multiple regulation functions, and the performance of the copper foil is comprehensively improved.

[0021] 3. The ionic liquid additive of the present application can simultaneously improve the tensile strength and elongation of the electrolytic copper foil, reduce the surface roughness and average grain size of the copper foil under the conditions of direct current deposition process. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a schematic diagram of the chemical structure of the ionic liquid additive of the present application.

[0023] Figure 2 It is the rough surface morphology diagram (a) of the electrolytic copper foil prepared in the present application Example 1 and the stress-strain curve diagram (b) compared with the electrolytic copper foil prepared in the present application Comparative Example 1.

[0024] Figure 3 It is the rough surface morphology diagram (a) of the electrolytic copper foil prepared in the present application Example 1 and the stress-strain curve diagram (b) compared with the electrolytic copper foil prepared in the present application Comparative Example 1.

[0025] Figure 4 It is the rough surface morphology diagram (a) of the electrolytic copper foil prepared in the present application Example 2 and the stress-strain curve diagram (b) compared with the electrolytic copper foil prepared in the present application Comparative Example 1.

[0026] Figure 5 It is the rough surface morphology diagram (a) of the electrolytic copper foil prepared in the present application Example 3 and the stress-strain curve diagram (b) compared with the electrolytic copper foil prepared in the present application Comparative Example 1.

[0027] Figure 6 It is the rough surface morphology diagram (a) of the electrolytic copper foil prepared in the present application Example 4 and the stress-strain curve diagram (b) compared with the electrolytic copper foil prepared in the present application Comparative Example 1.

[0028] Figure 7 Surface topography of the rough surface of the electrolytic copper foil prepared in Example 5 of the present application (a) and stress-strain curve (b) in comparison with the electrolytic copper foil prepared in Comparative Example 1.

[0029] Figure 8 Surface topography of the rough surface of the electrolytic copper foil prepared in Example 6 of the present application (a) and stress-strain curve (b) in comparison with the electrolytic copper foil prepared in Comparative Example 1.

[0030] Figure 9 Surface topography of the rough surface of the electrolytic copper foil prepared in Comparative Example 2 of the present application (a) and stress-strain curve (b) in comparison with the electrolytic copper foil prepared in Comparative Example 2.

[0031] Figure 10 Cross-sectional grain boundary diagram (a) of the electrolytic copper foil prepared in Comparative Example 1 of the present application and its corresponding grain size distribution diagram (b).

[0032] Figure 11 Cross-sectional grain boundary diagram (a) of the electrolytic copper foil prepared in Example 5 of the present application and its corresponding grain size distribution diagram (b). DETAILED DESCRIPTION

[0033] In order to better understand the content of the present application, the present application will be further described below in combination with specific examples and drawings. The following examples give detailed implementation and operation steps based on the technology of the present application, but the protection scope of the present application is not limited to the following examples.

[0034] Please refer to Figure 1 , Figure 1 Chemical structure diagram of the ionic liquid additive for the electrolytic copper foil of the present application: R1, R2 represent one of any alkyl groups, wherein R1 represents one of CH2, C2H4, C4H8, C6H 12 , C8H 16 , C 10 H 20 , etc., and R2 represents one of CH3, C2H5, C4H9, C6H 13 , C8H 17 , C 10 H 21one of -H, -COOH, -SO3H, -PO3H, -NH2, -SH, -CN group, Y represents one of [Cl]-, [Br]-, [BF4]-, [PF6]-, [CF3CO2]-, [CF3SO3]- and the like (all of the anions can participate in the formation of ionic liquid); the additive for electrolytic copper foil (i.e. copper foil additive) of the present application includes imidazole ring containing nitrogen element and -NH2, and [Cl]-, [Br]- (including but not limited to the above groups), due to the specific groups contained in the cation or anion of the functional ionic liquid, the copper foil additive has good designability, and can be "designed as needed". For example, the leveling agent is usually a heterocyclic compound containing nitrogen element, which can inhibit the abnormal deposition growth of Cu 2+ , the -NH2 group can form complex with Cu 2+ in electrolyte, accelerate the formation of crystal nucleus, reduce the size of deposition particles, and is beneficial to the improvement of the density of electrolytic copper foil; as the brightener commonly used in the production process of electrolytic copper foil, [Cl]- can change the transformation crystallization speed of Cu 2+ , make the copper foil grain structure and surface uniform and fine, and the anion [Br]- in the same main group as [Cl]- also has similar properties, the negative Br - can also participate in the reduction process of Cu 2+ near the cathode; the joint of the above specific groups can make the performance of copper foil be comprehensively improved. The ionic liquid is designed according to the function of the copper foil additive, especially the introduction of various special groups into X and Y of ionic liquid, which can make the single ionic liquid additive have multiple regulation functions, and then replace the traditional composite additive by single ionic liquid additive, reduce the types and amount of additives, and realize the comprehensive improvement of the performance of copper foil.

[0035] The application of the ionic liquid additive of the present application is to improve the comprehensive performance of electrolytic copper foil products; the ionic liquid additive for electrolytic copper foil adopted by the present application comprises one of 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, 1-decyl-3-methylimidazolium chloride, 1-aminopropyl-3-methylimidazolium chloride and 1-aminopropyl-3-methylimidazolium bromide, wherein the concentration of the ionic liquid additive in the base electrolyte is 10 mg / L to 50 mg / L; among the ionic liquid additives selected and combined through different mechanisms of groups, the additive with an imidazole ring containing a nitrogen element and [Cl]ˉ includes 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride and 1-decyl-3-methylimidazolium chloride, the additive with an imidazole ring containing a nitrogen element, an -NH2 group and [Cl]ˉ includes 1-aminopropyl-3-methylimidazolium chloride, and the additive with an imidazole ring containing a nitrogen element, an -NH2 group and [Br]ˉ includes 1-aminopropyl-3-methylimidazolium bromide.

[0036] The preparation method of the high-tensile high-elongation electrolytic copper foil proposed by the present application comprises the following steps:

[0037] Step A: mechanically polishing the cathode titanium to obtain a reusable surface without an oxide layer;

[0038] Step B: adding copper sulfate pentahydrate and sulfuric acid into deionized water to configure a base electrolyte, wherein the Cu 2+ ion content is 80 g / L to 150 g / L, and the sulfuric acid content is 65 g / L to 110 g / L;

[0039] Step C: adjusting the temperature of the configured copper sulfate-sulfuric acid base electrolyte to 30℃ to 60℃;

[0040] Step D: adding the copper sulfate-sulfuric acid base electrolyte after temperature adjustment into an electrolytic cell, adding a single ionic liquid additive with a certain concentration into the electrolytic cell, stirring, fully mixing the additive and the base electrolyte, and then starting direct current deposition on the titanium cathode, wherein the current density is kept at 40 A / dm 2 to 80 A / dm 2 , to obtain the high-tensile high-elongation electrolytic copper foil.

[0041] The application of the ionic liquid additive in the electrolytic copper foil and the preparation method of the high-tensile high-elongation electrolytic copper foil proposed by the present application are to prepare the electrolyte by using the ionic liquid additive prepared through directional synthesis, so that the additive can produce a synergistic promotion effect with sulfuric acid and copper sulfate in the electrolyte. The additive can simultaneously improve the tensile strength and elongation of the copper foil under the direct current deposition process condition, and reduce the surface roughness and average grain size of the copper foil.

[0042] The ionic liquid additive provided by the application can be used to prepare electrolytic copper foil with high tensile strength and high elongation under single type of additive condition, the tensile strength can be up to 609.9 MPa at room temperature, the elongation can be up to 17.1%, and the roughness Rz can be as small as 2.655 μm. The additive process of the application has wide application range, and the additive type is less, which is convenient for process control, and solves the problems of many types of additives and large amount of addition in the production process of electrolytic copper foil, and improves the quality of copper foil products, and is beneficial to reduce the loss cost, and has practical significance for the production of lithium battery copper foil.

[0043] The application will be described in detail below with specific examples:

[0044] Comparative Example 1: The preparation of electrolytic copper foil and the test of performance results were carried out on the basis electrolyte without adding new type of ionic liquid additive or traditional composite additive; please refer to Figure 2 , the surface morphology diagram (a) of the rough surface of the electrolytic copper foil prepared in Comparative Example 1 of the application and the corresponding stress-strain curve diagram (b) thereof.

[0045] Comparative Example 2: The preparation of electrolytic copper foil and the test of performance results were carried out on the basis electrolyte by adding traditional composite additive; the traditional composite additive used in this comparative example was gelatin 50 mg / L, polyethylene glycol 5 mg / L, hydrochloric acid 20 mg / L, and sodium polydithiodipropyl sulfone 10 mg / L; please refer to Figure 9 , the surface morphology diagram (a) of the rough surface of the electrolytic copper foil prepared in Comparative Example 2 and the stress-strain curve diagram (b) thereof compared with the electrolytic copper foil prepared without adding composite additive.

[0046] Example 1:

[0047] (1) The cathode titanium was mechanically polished to obtain reusable surface without oxide layer;

[0048] (2) Copper sulfate pentahydrate and sulfuric acid were added in deionized water to configure a basis electrolyte, the Cu 2+ ion content in the basis electrolyte was 100 g / L, and the sulfuric acid content was 95 g / L;

[0049] (3) The temperature of the configured copper sulfate-sulfuric acid basis electrolyte was adjusted to 50℃;

[0050] (4) The copper sulfate-sulfuric acid basis electrolyte after temperature adjustment was added into an electrolytic cell, and 20 mg / L of 1-butyl-3-methylimidazole chloride salt was added into the electrolytic cell, and stirring was carried out, so that the additive and the basis electrolyte were fully mixed, and then direct current deposition was started on the titanium cathode, the current density was kept at 60 A / dm 2, the electrolytic copper foil with high tensile strength and high elongation is obtained.

[0051] Please refer to Figure 3 , the surface topography of the electrolytic copper foil prepared in Example 1 of the present application (a) and the stress-strain curve (b) of the electrolytic copper foil prepared in Comparative Example 1 are shown in the following figures. Figure 2 and Figure 3 It can be seen that, under the same conditions, after the addition of the single ionic liquid additive described in the present application, the surface topography profile of the prepared electrolytic copper foil is greatly improved, and the surface becomes more flat. The stress-strain curve shows that the addition of the single ionic liquid additive can simultaneously increase the tensile strength and elongation of the copper foil.

[0052] Example 2:

[0053] Compared with Example 1, the new ionic liquid additive used in this example is 20 mg / L of 1-hexyl-3-methylimidazolium chloride. Please refer to Figure 4 , the surface topography of the electrolytic copper foil prepared in Example 2 of the present application (a) and the stress-strain curve (b) of the electrolytic copper foil prepared without the addition of the new ionic liquid additive in the present application (Comparative Example 1) are shown in the following figures.

[0054] Example 3:

[0055] Compared with Example 1, the new ionic liquid additive used in this example is 20 mg / L of 1-octyl-3-methylimidazolium chloride. Please refer to Figure 5 , the surface topography of the electrolytic copper foil prepared in Example 3 of the present application (a) and the stress-strain curve (b) of the electrolytic copper foil prepared without the addition of the new ionic liquid additive in the present application (Comparative Example 1) are shown in the following figures.

[0056] Example 4:

[0057] Compared with Example 1, the new ionic liquid additive used in this example is 20 mg / L of 1-decyl-3-methylimidazolium chloride. Please refer to Figure 6 , the surface topography of the electrolytic copper foil prepared in Example 4 of the present application (a) and the stress-strain curve (b) of the electrolytic copper foil prepared without the addition of the new ionic liquid additive in the present application (Comparative Example 1) are shown in the following figures.

[0058] Example 5:

[0059] Compared with Example 1, the new ionic liquid additive used in this example is 30 mg / L of 1-aminopropyl-3-methylimidazolium chloride. Please refer to Figure 7The image shows the rough surface morphology of the electrolytic copper foil prepared in Example 5 of the present invention (a) and the stress-strain curve (b) compared with the electrolytic copper foil prepared without the novel ionic liquid additive of the present invention (comparative Example 1 above).

[0060] Example 6:

[0061] Compared to Example 1, the novel ionic liquid additive used in this example is 30 mg / L of 1-aminopropyl-3-methylimidazolium bromide. Please refer to [link to example]. Figure 8 The image shows the rough surface morphology of the electrolytic copper foil prepared in Example 6 of the present invention (a) and the stress-strain curve (b) compared with the electrolytic copper foil prepared without the novel ionic liquid additive of the present invention (comparative Example 1 above).

[0062] The room temperature tensile strength, elongation, and roughness Rz test results of the electrolytic copper foils prepared in the examples and control examples are shown in Table 1.

[0063] Table 1 Performance test results of electrolytic copper foil

[0064]

[0065] As can be seen from the above comparison, the electrolytic copper foil prepared by adding a small amount of the single ionic liquid additive of the present invention has higher tensile strength and elongation as well as lower roughness.

[0066] This application allows for the design of ionic liquids, introducing various special groups into the X and Y components of the ionic liquid, enabling a single ionic liquid additive to possess multiple regulatory functions. By replacing traditional composite additives with a single ionic liquid additive, the overall performance of copper foil can be comprehensively improved while reducing the types and amounts of additives used.

[0067] This invention can have other embodiments based on the above preparation method, which will not be listed one by one. Therefore, any simple modifications, equivalent changes and alterations made by any person skilled in the art to the above embodiments without departing from the scope of the technical solution of this invention shall still fall within the scope of the technical solution of this invention.

Claims

1. The application of ionic liquid additives in electrolytic copper foil, wherein the ionic liquid additive is 1-aminopropyl-3-methylimidazolium chloride; Methods for preparing electrolytic copper foil include: (1) Mechanically polish the cathode titanium to obtain a reusable oxide-free surface; (2) Prepare a basic electrolyte by adding copper sulfate pentahydrate and sulfuric acid to deionized water; (3) Adjust the temperature of the prepared copper sulfate-sulfuric acid basic electrolyte; (4) Add the copper sulfate-sulfuric acid basic electrolyte, after reaching the adjusted temperature, to the electrolytic cell, and add the aforementioned ionic liquid additive. Stir until the additive is fully mixed with the basic electrolyte, and then begin DC electrodeposition on the titanium cathode, maintaining a current density of 40 A / dm³. 2 ~80A / dm 2 This yields electrolytic copper foil with high tensile strength and high elongation. Step (2) Cu in the basic electrolyte 2+ The ion content is 80g / L ~ 150g / L, and the sulfuric acid content is 65g / L ~ 110g / L.

2. The application of the ionic liquid additive as described in claim 1 in electrolytic copper foil, characterized in that, Step (3) Adjust the temperature of the basic electrolyte to 30℃~60℃.

3. The application of the ionic liquid additive as described in claim 1 in electrolytic copper foil, characterized in that, Step (4) The concentration of the ionic liquid additive in the base electrolyte is 10 mg / L ~ 50 mg / L.

4. The application of the ionic liquid additive as described in claim 1 in electrolytic copper foil, characterized in that, The ionic liquid additive can simultaneously improve the tensile strength and elongation of electrolytic copper foil and reduce its roughness. The elongation of electrolytic copper foil prepared by using 1-aminopropyl-3-methylimidazolium chloride alone as an additive is as high as 17.1%.

Images