Ionic liquid additive for nickel-copper alloy foil with high tensile strength and application of ionic liquid additive

Abstract

The invention relates to an ionic liquid additive for nickel-copper alloy foil with high tensile strength and application of the ionic liquid additive. The ionic liquid additive comprises one or more of eutectic ionic liquid, imidazole ionic liquid, quaternary ammonium ionic liquid, pyrrolidine ionic liquid and piperidine ionic liquid. According to the invention, the problems of poor corrosion resistance and low tensile strength of pure copper foil are effectively solved, so that the performance degradation and potential safety hazard of a lithium battery are improved, the transmission efficiency problem caused by roughness is reduced, and directional reference is expected to be provided for a novel alloy foil additive.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic copper foil, and particularly relates to an ionic liquid additive for high tensile strength nickel-copper alloy foil and its application. Background Art

[0002] Copper foil is an important component of lithium-ion batteries (LIBs), printed circuit boards (PCBs), and chip packaging substrates (CPSs), and plays a key role in various applications such as new energy vehicles, new energy storage devices, consumer electronic products, and 5G communication devices. In LIBs, copper is prone to oxidation at high potentials. Once the copper foil current collector corrodes, it will reduce the service life of the battery and have a negative impact on its stability and safety. In PCBs, a rough copper foil surface may increase the loss of high-frequency signal transmission in PCBs, while high-strength copper foil can withstand greater tension to ensure the stability and reliability of PCBs. Therefore, to meet the requirements of long service life, safety of LIBs and low signal transmission loss in high-speed and high-frequency PCBs, it is particularly important to prepare copper foil with excellent mechanical properties, low surface roughness, and high corrosion resistance.

[0003] Numerous studies have shown that the use of additives in direct current electroplating is an important means to control the mechanical properties of copper foil. Trace additives in the plating solution mainly affect the electrochemical reaction process at the electrode interface through cathode adsorption, metal ion complexation, and ion diffusion, thereby controlling grain growth. Compared with organic solvents, ionic liquids have the advantages of stable chemical properties, negligible vapor pressure, safety, and non-toxicity. In addition, their broad electrochemical window, high solubility, and better conductivity than non-aqueous solvents make them widely used in the field of metal electrodeposition. Ionic liquids as electroplating solutions or as electrolyte additives mainly include low eutectic ionic liquids and imidazole-based ionic liquids. Recently, people have used the functionalized ionic liquid 1-aminopropyl-3-methylimidazolium chloride as an additive to the electrolyte, and adjusted grain growth through cathodic polarization, refined grains, and increased the density of twin boundaries in copper foil, effectively improving its mechanical properties. At the same time, the invention patent CN16024618A discloses that imidazole-based ionic liquids are used as electrolyte additives, which improve the tensile strength and elongation rate of copper foil, and reduce the surface roughness and average grain size of copper foil. Therefore, ionic liquids have the potential to improve the mechanical properties of electrolytic alloy foil as additives. The above existing additives are mainly used in electrolytes to prepare pure copper foil. However, alloy foil based on ionic liquids still needs further research. In addition, the application of alloy foil in lithium batteries is crucial. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an ionic liquid additive for high tensile strength nickel-copper alloy foil and its application, so as to solve the problems of poor corrosion resistance and low tensile strength of pure copper foil.

[0005] The present invention provides an ionic liquid additive for high tensile strength nickel - copper alloy foil, and the ionic liquid additive includes one or more of eutectic - like ionic liquids, imidazole - based ionic liquids, quaternary ammonium - based ionic liquids, pyrrolidine - based ionic liquids, and piperidine - based ionic liquids.

[0006] Preferably, the eutectic - like ionic liquid includes one or more of choline chloride - urea and choline chloride - ethylene glycol.

[0007] Preferably, the imidazole - based ionic liquid includes 1 - butyl - 3 - methylimidazolium chloride ([Bmim][Cl], such as [Bmim][NiCl 3 or [Bmim][CuCl]), 1 - butyl - 3 - methylimidazolium bromide ([Bmim][Br]), 1 - butyl - 3 - methylimidazolium tetrafluoroborate ([Bmim][BF 4 ), 1 - butyl - 3 - methylimidazolium hexafluorophosphate ([Bmim][PF 6 ), 1 - butyl - 3 - methylimidazolium acetate ([Bmim][OAc]), 1 - hexyl - 3 - methylimidazolium trifluoromethanesulfonate (HmimOTF), 1 - aminopropyl - 3 - methylimidazolium chloride ([C 3 NH 2 CIm][Cl]), or one or more thereof.

[0008] Preferably, the quaternary ammonium - based ionic liquid includes one or more of tetraethylammonium bis(trifluoromethanesulfonyl)imide, tetraethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetraethylammonium bromide, and tetrabutylammonium bromide.

[0009] Preferably, the pyrrolidine - based ionic liquid is 1 - ethyl - 1 - methylpyrrolidinium tetrafluoroborate.

[0010] Preferably, the piperidine - based ionic liquid is N - butyl - N - methylpiperidinium bis(trifluoromethanesulfonyl)imide.

[0011] The present invention also provides an application of the ionic liquid additive for high tensile strength nickel - copper alloy foil in the preparation of nickel - copper alloy foil. Further, it includes the following steps:

[0012] (1) Dissolve copper sulfate pentahydrate, nickel sulfate hexahydrate, and nickel chloride hexahydrate in dilute sulfuric acid solution, then add citric acid, and continue stirring after heating;

[0013] (2) Add the ionic liquid additive, connect a DC power supply, and regulate the cathode current, electrolyte temperature, and acidity to electro - deposit nickel - copper alloy foil.

[0014] Preferably, the concentration of copper sulfate pentahydrate in step (1) is 30 - 80 g / L; the concentration of nickel sulfate hexahydrate is 150 - 250 g / L; the concentration of nickel chloride hexahydrate is 40 - 60 g / L; and the concentration of citric acid is 30 - 80 g / L.

[0015] Preferably, boric acid is further added in step (1), and the addition amount is 10 - 60 g / L.

[0016] Preferably, the addition amount of the ionic liquid additive in step (2) is 1 - 40 mg / L.

[0017] Preferably, the cathode current in step (2) is 10 - 50 A / dm 2 , the electrolyte temperature is 30 - 70 °C, the acidity pH is 3 - 5, and the electrodeposition time is 10 - 20 min.

[0018] Preferably, the nickel - copper alloy foil in step (2) is used in the fields of lithium batteries or electronic circuits.

[0019] Beneficial effects

[0020] (1) By studying the regulation of ionic liquid additives and combining the co - deposition method for electrolytic preparation of alloy foil, the present invention greatly improves the tensile strength and elongation rate of copper foil, and effectively solves the serious problem of battery life decline caused by copper foil corrosion.

[0021] (2) The ionic liquid additive disclosed in the present invention has low volatility, non - flammability, good solubility, high thermal stability and chemical stability, high ionic conductivity, a large electrochemical window, is environmentally friendly and can be recycled; at the same time, it is cheap and easy to prepare. In addition, the electrolytic alloy foil can overcome the problems of complex traditional rolling process and too high production cost, and has broad application value and market prospect.

[0022] (3) The present invention effectively solves the problems of poor corrosion resistance and low tensile strength of pure copper foil, thereby improving the performance attenuation and safety hazards of lithium batteries, and at the same time reducing the transmission efficiency problem caused by roughness, and is expected to provide a directional reference for new alloy foil additives. Description of the Drawings

[0023] Figure 1 It is the SEM image of the electrodeposited nickel - copper alloy foil in Example 2. Detailed Embodiments

[0024] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0025] For those not specified in the embodiments in terms of specific techniques or conditions, they can all be carried out according to the techniques or conditions described in the literature in this field or according to the product instructions.

[0026] The present invention provides an application of an ionic liquid additive for high tensile strength nickel-copper alloy foil in the preparation of nickel-copper alloy foil. Further, it includes the following steps:

[0027] S1: Dissolve nickel sulfate hexahydrate, nickel chloride hexahydrate, and copper sulfate pentahydrate in dilute sulfuric acid solution, add citric acid, and continue stirring after heating;

[0028] S2: Add an ionic liquid additive, including one or more of deep eutectic ionic liquids, imidazole ionic liquids, quaternary ammonium ionic liquids, pyrrolidine ionic liquids, and piperidine ionic liquids;

[0029] S3: Connect a DC power supply, and regulate the cathode current, electrolyte temperature, and acidity to electro-deposit nickel-copper alloy foil.

[0030] Further, in step S1, the concentration of copper sulfate pentahydrate is 30 - 80 g / L, preferably 40 - 60 g / L; the concentration of nickel sulfate hexahydrate is 150 - 250 g / L, preferably 180 - 220 g / L; the concentration of nickel chloride hexahydrate is 40 - 60 g / L, preferably 50 - 60 g / L; the concentration of citric acid is 30 - 80 g / L, preferably 40 - 60 g / L.

[0031] Further, boric acid is also added in step S1, and the addition amount is 10 - 60 g / L, preferably 20 - 40 g / L.

[0032] Further, in step S2, the deep eutectic ionic liquids include choline chloride-urea, choline chloride-ethylene glycol; preferably choline chloride-urea.

[0033] Further, in step S2, the imidazole ionic liquids include 1-butyl-3-methylimidazolium chloride ([Bmim][Cl], such as [Bmim][NiCl 3 or [Bmim][CuCl]), 1-butyl-3-methylimidazolium bromide ([Bmim][Br]), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF 4) 1-Butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF 6 ) 1-Butyl-3-methylimidazolium acetate ([Bmim][OAc]), 1-Hexyl-3-methylimidazolium trifluoromethanesulfonate (HmimOTF), 1-Aminopropyl-3-methylimidazolium chloride ([C 3 NH 2 CIm][Cl]), or one or more of them; preferably 1-Hexyl-3-methylimidazolium trifluoromethanesulfonate (HmimOTF).

[0034] Furthermore, in step S2, the quaternary ammonium ionic liquid includes tetraethylammonium bis(trifluoromethanesulfonyl)imide, tetraethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetraethylammonium bromide, and tetrabutylammonium bromide, preferably tetraethylammonium bis(trifluoromethanesulfonyl)imide. The pyrrolidine-based ionic liquid is 1-Ethyl-1-methylpyrrolidinium tetrafluoroborate. The piperidine-based ionic liquid is N-Butyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide.

[0035] Furthermore, in step S2, the addition amount of the ionic liquid additive is 1-40 mg / L, preferably 10-20 mg / L.

[0036] Furthermore, in step S3, the cathode current is 10-50 A / dm 2 , preferably 20-30 A / dm 2 ; the electrolyte temperature is 30-70 °C, preferably 40-60 °C; the acidity pH is 3-5, preferably 4-5.

[0037] The present invention provides the application of the above nickel-copper alloy foil in the preparation of battery or electronic circuit electrode materials, and the electrode materials include lithium battery current collectors or all-solid-state battery current collectors or electronic circuit signal transmission carriers.

[0038] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0039] Example 1

[0040] 190 g / L nickel sulfate hexahydrate, 55 g / L nickel chloride hexahydrate, 80 g / L copper sulfate pentahydrate, 70 g / L citric acid, 30 g / L boric acid, and dilute sulfuric acid (1 mol / L) were mixed to obtain a composite electrolyte. The electrolyte was heated to 35 °C and completely dissolved. 20 mg / L choline chloride-urea ionic liquid additive was added, and then the pH of the electrolyte was adjusted to 3.5. The DC power supply was connected, the cathode current density was 20 A / dm 2 , the alloy plating time was 10 min, and the peeled alloy foil was rinsed with pure water and dried. The thickness of the nickel-copper alloy foil was 6 μm.

[0041] Example 2

[0042] Mix 250 g / L nickel sulfate hexahydrate, 60 g / L nickel chloride hexahydrate, 60 g / L copper sulfate pentahydrate, 80 g / L citric acid, 40 g / L boric acid, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 55 °C and dissolve it completely. Add 15 mg / L of the ionic liquid additive 1-hexyl-3-methylimidazolium trifluoromethanesulfonate (HmimOTF), and then adjust the pH of the electrolyte to 3. Connect a DC power supply, with a cathode current density of 15 A / dm 2 , and the alloy plating time is 12 min. Flush the peeled alloy foil with pure water and dry it. The thickness of the nickel-copper alloy foil is 8 μm.

[0043] Example 3

[0044] Mix 200 g / L nickel sulfate hexahydrate, 50 g / L nickel chloride hexahydrate, 70 g / L copper sulfate pentahydrate, 60 g / L citric acid, 20 g / L boric acid, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 60 °C and dissolve it completely. Add 10 mg / L of the ionic liquid additive tetraethylammonium bis(trifluoromethanesulfonate) imide salt, and then adjust the pH of the electrolyte to 4. Connect a DC power supply, with a cathode current density of 15 A / dm 2 , and the alloy plating time is 15 min. Flush the peeled alloy foil with pure water and dry it. The thickness of the nickel-copper alloy foil is 8 μm.

[0045] Example 4

[0046] Mix 170 g / L nickel sulfate hexahydrate, 60 g / L nickel chloride hexahydrate, 75 g / L copper sulfate pentahydrate, 65 g / L citric acid, 25 g / L boric acid, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 65 °C and dissolve it completely. Add 20 mg / L of the ionic liquid additive N-butyl-N-methylpiperidinium bis(trifluoromethanesulfonyl) imide salt, and then adjust the pH of the electrolyte to 5. Connect a DC power supply, with a cathode current density of 40 A / dm 2 , and the alloy plating time is 10 min. Flush the peeled alloy foil with pure water and dry it. The thickness of the nickel-copper alloy foil is 6 μm.

[0047] Example 5

[0048] Mix 150 g / L nickel sulfate hexahydrate, 60 g / L nickel chloride hexahydrate, 30 g / L copper sulfate pentahydrate, 45 g / L citric acid, 20 g / L boric acid, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 70 °C and dissolve it completely. Add 5 mg / L of the ionic liquid additive 1-aminopropyl-3-methylimidazolium chloride ([C3 NH 2 CIm][Cl]), and then adjust the pH of the electrolyte to 4.5. Connect the DC power supply, and the cathode current density is 50 A / dm 2 , the alloy plating time is 10 min, and the peeled alloy foil is rinsed with pure water and dried. The thickness of the nickel-copper alloy foil is 8 μm.

[0049] Example 6

[0050] Mix 160 g / L nickel sulfate hexahydrate, 50 g / L nickel chloride hexahydrate, 35 g / L copper sulfate pentahydrate, 30 g / L citric acid, 30 g / L boric acid, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 60 °C and dissolve it completely. Add 15 mg / L of the ionic liquid additive 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF 6 , and then adjust the pH of the electrolyte to 4. Connect the DC power supply, and the cathode current density is 45 A / dm 2 , the alloy plating time is 12 min, and the peeled alloy foil is rinsed with pure water and dried. The thickness of the nickel-copper alloy foil is 8 μm.

[0051] Comparative Example 1

[0052] Different from Example 1, no ionic liquid additive is added, and other common copper foil additives used in industry are added.

[0053] Mix 190 g / L nickel sulfate hexahydrate, 55 g / L nickel chloride hexahydrate, 80 g / L copper sulfate pentahydrate, 70 g / L citric acid, 30 g / L boric acid, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Add 15 mg / L of the composite additive hydroxyethyl cellulose, 5 mg / L of polyethylene glycol, 10 mg / L of sodium polydithiopropane sulfonate, and 10 mg / L of sodium mercaptothiopropane sulfonate. Heat the electrolyte to 55 °C and dissolve it completely. Adjust the pH of the electrolyte to 3. Connect the DC power supply, and the cathode current density is 40 A / dm 2 , the alloy plating time is 20 min, and the peeled alloy foil is rinsed with pure water and dried.

[0054] Comparative Example 2

[0055] Different from Example 1, pure copper foil is prepared without adding nickel sulfate hexahydrate, nickel chloride hexahydrate, and complexing agent.

[0056] Mix 80 g / L copper sulfate pentahydrate, 70 g / L citric acid, 30 g / L boric acid, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 35 °C and dissolve it completely. Adjust the pH of the electrolyte to 3.5. Connect the DC power supply, and the cathode current density is 20 A / dm 2, the alloy plating time was 10 min, and the peeled alloy foil was rinsed with pure water and dried.

[0057] Table 1 Performance test results of the products in the examples and comparative examples

[0058]

[0059]

[0060] As can be seen from Table 1, in Examples 1-6, the nickel-copper alloy foil prepared by adding ionic liquid had a tensile strength range of 860-920 MPa at room temperature, which was significantly improved compared with Comparative Examples 1-2. The nickel ions and choline chloride-urea reacted to produce a complex [NiCl 3 - , and it was determined that after adding the metal salt, it only physically mixed with the system and did not change the characteristics of the ionic liquid. The Ni-Cu synthesis process included three stages, namely, the diffusion-controlled three-dimensional nucleation / growth process, the adsorption process, and the reduction of water. Boric acid helped to increase the nucleation rate, reduce the cracks in the Ni-Cu coating, refine the grains, and make the coating smooth and dense. The synergistic effect of the ionic liquid additive containing chloride ions or -NH 2 groups further improved the mechanical properties of the copper foil, but it did not affect the nucleation mechanism. Therefore, ionic liquids are expected to provide new ideas for electrolyte additives in lithium batteries.

[0061] Table 2 Performance test results of the products in the examples and comparative examples used to assemble lithium iron phosphate batteries

[0062]

[0063] The nickel-copper alloy foil prepared by adding ionic liquid was assembled into a lithium iron phosphate battery. As can be seen from Table 2, in Examples 1-6, the initial discharge capacity was basically maintained at about 160 mAh / g, and after 200 cycles, it still remained at 154.0-160.2 mAh / g, and the capacity retention rate was 95.7-97.1%. In contrast, the capacity retention rates of the alloy copper foil without ionic liquid in Comparative Example 1 and the pure copper foil in Comparative Example 2 were about 91%. Therefore, ionic liquids, as lithium battery additives, improve the corrosion resistance of current collectors and effectively solve the cycle stability of lithium batteries.​

Claims

1. An ionic liquid additive for high tensile strength nickel-copper alloy foil, characterized in that: The ionic liquid additive includes one or more of a low-eutectic ionic liquid, an imidazole ionic liquid, a quaternary ammonium ionic liquid, a pyrrolidine ionic liquid, and a piperidine ionic liquid.

2. The ionic liquid additive for high tensile strength nickel-copper alloy foil according to claim 1, characterized in that: The low eutectic ionic liquid includes one or more of choline chloride-urea and choline chloride-ethylene glycol; the imidazole ionic liquid includes one or more of butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium acetate, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate, and 1-aminopropyl-3-methylimidazolium chloride; the quaternary ammonium ionic liquid includes one or more of tetraethylammonium bis(trifluoromethanesulfonic acid)imide, tetraethyl hexafluorophosphate quaternary ammonium salt, tetrabutyl hexafluorophosphate quaternary ammonium salt, tetraethylammonium bromide, and tetrabutylammonium bromide; the pyrrolidine ionic liquid is 1-ethyl-1-methylpyrrolidine tetrafluoroborate; and the piperidine ionic liquid is N-butyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide.

3. Use of the ionic liquid additive for high tensile strength nickel-copper alloy foil as claimed in claim 1 in the preparation of nickel-copper alloy foil.

4. The use according to claim 3, characterized in that: The steps include: (1) dissolving copper sulfate pentahydrate, nickel sulfate hexahydrate, and nickel chloride hexahydrate in a dilute sulfuric acid solution, adding citric acid, and continuing to stir after heating; (2) adding ionic liquid additives, connecting a DC power supply, and regulating the cathode current and the electrolyte temperature and acidity to electrodeposit a nickel-copper alloy foil.

5. The use according to claim 4, characterized in that: In the step (1), the concentration of copper sulfate pentahydrate is 30-80 g / L; the concentration of nickel sulfate hexahydrate is 150-250 g / L; the concentration of nickel chloride hexahydrate is 40-60 g / L; and the concentration of citric acid is 30-80 g / L.

6. The use according to claim 4, characterized in that: The amount of the ionic liquid additive added in step (2) is 1-40 mg / L.

7. The use according to claim 4, characterized in that: The cathode current in step (2) is 10-50A / dm 2 , the electrolyte temperature is 30-70℃, the acidity pH is 3-5, and the electrodeposition time is 10-20min.

8. The use according to claim 4, characterized in that: The nickel-copper alloy foil in step (2) is used in the field of lithium batteries or electronic circuits.

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