Preparation method of electrolytic nickel-iron-copper alloy foil

Abstract

The invention relates to a preparation method of an electrolytic nickel-iron-copper alloy foil, which comprises the following steps: dissolving corresponding salt of an alloy in dilute sulphuric acid, realizing metal coprecipitation through a complexing agent and regulating and controlling the pH value of an electrolyte, and uniformly distributing the metal content of the alloy foil. The mechanical property of the alloy foil is controlled by adopting an additive, and the nickel-iron-copper alloy foil is obtained through direct-current electrolytic electrodeposition. According to the invention, the problems of high cost, complex production process, non-uniform thickness, easy generation of holes and the like, which are caused by a plurality of working procedures in the traditional mechanical rolling method, are solved, and the problems of low tensile strength of the traditional pure copper foil at normal temperature and unstable tensile strength after high-temperature aging are solved; and the problem of thin surface cracking caused by non-uniform metal components of the alloy foil is solved, and the corrosion resistance of the foil layer is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic copper foils, and particularly relates to a method for preparing an electrolytic nickel-iron-copper alloy foil. Background Art

[0002] As the carrier and current collector of the negative electrode material of lithium-ion batteries, electrolytic copper foils play a crucial role. During the charge and discharge process, the copper foil will continuously experience expansion and contraction, which may lead to a decline in battery performance or damage. Copper foils with high elongation can effectively prevent fractures during this process, thereby enhancing the safety of lithium-ion batteries during use. Therefore, seeking mechanical properties such as high tensile strength and excellent elongation is particularly important for supporting the development of lithium-ion batteries towards extreme miniaturization and meeting the growing requirements for reliability in production. Compared with pure metal foils, due to their unique magnetic and electrical conductivity, alloy foils are widely used in the field of electromagnetic fields, such as magnetic recording, superconducting energy storage, and precision electronic materials. Alloy foils exhibit more superior comprehensive properties in terms of magnetic, electrical, and mechanical properties, which gives them stronger competitiveness and broad development prospects in the future market. Currently, the research on alloy foils can be roughly divided into iron-based, nickel-based, and copper-based alloy systems according to their main constituent elements.

[0003] The rolling method is an effective method for manufacturing copper alloy foils in industry, but it is still very difficult to prepare ultra-thin foils with a thickness less than 20 μm. In addition, additional processes such as smelting, casting, and repeated rolling require a large amount of equipment investment and may lead to the deterioration of the working environment [CN110106394A][CN201810864064.4]. In recent years, other preparation methods, including electrodeposition, chemical deposition, sputtering, and chemical vapor deposition, have also been widely studied. However, the problems faced in manufacturing ultra-thin alloy foils have not been effectively solved. Although it is relatively easy to control the aluminum material through sputtering, electrodeposition, or other chemical methods, further exploration is still needed to improve the composition uniformity. For example, alloy foils prepared by electrodeposition often show copper-rich regions and nickel-rich regions, resulting in uneven compositions of copper alloy foils fabricated by the sputtering method. Therefore, it is necessary to explore new methods to achieve ultra-thin alloy foils with controllable and uniform compositions to meet the increasing development requirements of high-end manufacturing. Summary of the Invention

[0004] The present invention provides a method for preparing an electrolytic nickel-iron-copper alloy foil, aiming to solve technical problems such as the need for repeated rolling during the mechanical rolling process, long production cycle, high cost, easy generation of holes, and difficulty in maintaining uniform thickness. At the same time, it optimizes the tensile strength of pure copper foils and the problem of cracking on the thin surface caused by uneven metal compositions of alloy foils, and improves the corrosion resistance of the foil layer.

[0005] The present invention provides a method for preparing electrolytic nickel-iron-copper alloy foil, comprising the following steps:

[0006] (1) Mix nickel salt, ferrous salt, copper salt and dilute sulfuric acid to obtain a composite electrolyte, heat the composite electrolyte to the working temperature, and stir until completely dissolved;

[0007] (2) Sequentially add a complexing agent, a stabilizer, and an additive to the composite electrolyte, adjust the pH of the composite electrolyte to 3-5, then add a buffer, and perform direct current electrolytic deposition to obtain nickel-iron-copper alloy foil.

[0008] Preferably, the nickel salt in step (1) is one or more of nickel sulfate hexahydrate and nickel chloride hexahydrate, with a concentration of 130-200 g / L; the ferrous salt is ferrous sulfate heptahydrate, with a concentration of 50-100 g / L; the copper salt is copper sulfate pentahydrate, with a concentration of 10-100 g / L.

[0009] Preferably, the working temperature in step (1) is 45-70 °C.

[0010] Preferably, the stirring method in step (1) is mechanical stirring, with a rotation speed of 200-300 rpm and the stirring time being continuous stirring.

[0011] Preferably, the complexing agent in step (2) is one or more of citric acid, sodium citrate, xylitol, sorbitol, and mannitol, with a concentration of 30-80 g / L.

[0012] Preferably, the stabilizer in step (2) is ascorbic acid, with a concentration of 5-30 g / L.

[0013] Preferably, the additive in step (2) includes one or more of a wetting agent and a brightening agent, with a concentration of 0.1-10 g / L.

[0014] Preferably, the wetting agent is one or two of sodium dodecyl sulfate and sodium dodecylbenzenesulfonate.

[0015] Preferably, the brightening agent includes one or two of a primary brightening agent and a secondary brightening agent. The primary brightening agent is one or two of sodium saccharin and saccharin. The secondary brightening agent is 791 brightening agent.

[0016] Preferably, the buffer in step (2) is boric acid, with a concentration of 30-60 g / L.

[0017] Preferably, the current density of direct current electrolytic deposition in step (2) is 8-30 A / dm 2 , and the time is 10-20 min.

[0018] Preferably, the tensile strength of the nickel-iron-copper alloy foil obtained in step (2) is 800 - 1100 MPa, the elongation at normal temperature is 3 - 8%, and the roughness Rz of the matte surface is 0.3 - 0.8 μm.

[0019] Preferably, the thickness of the nickel-iron-copper alloy foil obtained in step (2) is 6 - 18 μm.

[0020] Preferably, the nickel-iron-copper alloy foil obtained in step (2) is applied to lithium batteries or electronic circuits.

[0021] Beneficial effects

[0022] (1) The present invention avoids the problems of the traditional mechanical rolling method, such as the need for multiple processes to form the foil, high cost, complex production process, uneven thickness, and easy generation of holes. At the same time, it solves the problems of low tensile strength of traditional pure copper foil at normal temperature and unstable tensile strength after high-temperature aging, and optimizes the problem of thin surface cracking caused by uneven metal composition of the alloy foil, improving the corrosion resistance of the foil layer.

[0023] (2) The present invention successfully realizes the co-deposition of ternary nickel-iron-copper alloy by adjusting the pH value of the electrolyte, and electrolytically prepares the alloy foil, thereby greatly improving the tensile strength and elongation of the alloy foil. The ternary nickel-iron-copper alloy foil surface is dense and hole-free, which is superior to the binary alloy foil, effectively solving the problem of poor corrosion resistance of traditional copper foil. The evenly distributed metal elements improve the stability of the alloy foil and can also be extended to the preparation of other metal alloy foils.

[0024] (3) The present invention provides a preparation method of ternary nickel-iron-copper alloy foil, which not only has few processes, high yield, low cost, and good repeatability, but also can solve the problems of complicated process and high production cost of the rolling method, and has broad practical value and market prospects. Description of the Drawings

[0025] Figure 1 is the X-ray powder diffraction pattern of the electrodeposited nickel-iron-copper alloy foil in Example 1.

[0026] Figure 2 is the SEM image of the electrodeposited nickel-iron-copper alloy foil in Example 1.

[0027] Figure 3 is the SEM image of the electrodeposited nickel-copper alloy foil in Comparative Example 2. Detailed Embodiments

[0028] 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.

[0029] 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 specifications.

[0030] The present invention provides a method for preparing an electrolytic nickel-iron-copper alloy foil, comprising the following steps:

[0031] (1) Mix nickel salt, ferrous salt, copper salt and dilute sulfuric acid to obtain a composite electrolyte, heat the composite electrolyte to the working temperature, and stir until completely dissolved;

[0032] (2) Sequentially add a complexing agent, a stabilizer, and an additive to the composite electrolyte, adjust the pH of the composite electrolyte to 3-5, then add a buffer, and perform direct current electrolytic deposition to obtain a nickel-iron-copper alloy foil.

[0033] In the present invention, the nickel salt in step (1) is nickel sulfate hexahydrate and nickel chloride hexahydrate; the ferrous salt is ferrous sulfate heptahydrate; the copper salt is copper sulfate pentahydrate.

[0034] In the present invention, the concentration of copper sulfate pentahydrate in step (1) is 10-100 g / L, preferably 20-80 g / L, and more preferably 40-60 g / L; the concentration of nickel sulfate hexahydrate is 100-150 g / L, preferably 110-140 g / L, and more preferably 110-120 g / L; the concentration of nickel chloride hexahydrate is 30-50 g / L, preferably 30-45 g / L, and more preferably 40-45 g / L; the concentration of ferrous sulfate heptahydrate is 50-100 g / L, preferably 60-90 g / L, and more preferably 60-80 g / L.

[0035] In the present invention, the working temperature in step (1) is 45-70 °C, preferably 50-60 °C, and more preferably 52-58 °C.

[0036] In the present invention, the complexing agent in step (2) is one or more of citric acid, sodium citrate, xylitol, sorbitol, and mannitol. Preferably it is citric acid.

[0037] In the present invention, the concentration of the complexing agent in step (2) is 30-80 g / L, preferably 40-60 g / L, and more preferably 45-55 g / L.

[0038] In the present invention, the stabilizer in the step (2) is ascorbic acid.

[0039] In the present invention, the concentration of the stabilizer in the step (2) is 5 - 30 g / L, preferably 10 - 30 g / L, and more preferably 10 - 20 g / L.

[0040] In the present invention, the additive in the step (2) includes one or more of a wetting agent and a brightening agent.

[0041] In the present invention, the concentration of the additive in the step (2) is 0.1 - 10 g / L, preferably 2 - 8 g / L, and more preferably 6 g / L.

[0042] In the present invention, the buffer in the step (2) is boric acid.

[0043] In the present invention, the concentration of the buffer in the step (2) is 30 - 60 g / L, preferably 40 - 60 g / L, and more preferably 40 - 50 g / L.

[0044] In the present invention, the direct current electrolytic deposition current density in the step (2) is 8 - 30 A / dm 2 , preferably 10 - 30 A / dm 2 , more preferably 10 - 20 A / dm 2 .

[0045] Example 1

[0046] 150 g / L nickel sulfate hexahydrate, 50 g / L nickel chloride hexahydrate, 50 g / L ferrous sulfate heptahydrate, 20 g / L copper sulfate pentahydrate, and dilute sulfuric acid (1 mol / L) were mixed to obtain a composite electrolyte. The electrolyte was heated to 50 °C and vigorously stirred for 30 min until completely dissolved. 40 g / L citric acid was added and then 20 g / L ascorbic acid was added, and stirring was continued. Then 3 g / L saccharin, 0.3 g / L sodium dodecyl sulfate, and 5 mL / L brightening agent 791 were added. The pH of the electrolyte was adjusted to 3, and then 50 g / L boric acid was added. The direct current power supply was connected, and the cathode current density was 20 A / dm 2 , the alloy plating time was 20 min, and the peeled alloy foil was rinsed with pure water and dried. The obtained copper alloy foil had a thickness of 18 μm, a room temperature tensile strength of 900 MPa, a room temperature elongation of 5.3%, and a surface roughness Rz of 0.6 μm.

[0047] Figure 1 is the X-ray powder diffraction pattern of the copper alloy foil in Example 1. It was found to be similar to the XRD pattern of the copper foil, indicating that the crystal structure of the alloy foil did not change significantly.

[0048] Figure 2It is the SEM image of the copper alloy foil in Example 1. The surface of the alloy foil is flattened without cracking. After passing direct current, the surface of the anode is easily passivated, and the contents of copper ions, nickel cations and iron cations in the electrolyte decrease rapidly, resulting in the deterioration of the electrolyte performance. Adding chloride ions can significantly improve the solubility of the anode, increase the conductivity of the electrolyte and improve the dispersion ability of the electrolyte. Therefore, chloride ions are an essential component in the electrolyte. However, if the content of chloride ions is too high, it will cause the foil layer to be rough or form burrs. In the electrolysis industry, NaCl is usually added to provide chloride ions, but sodium ions will affect the structure of the coating, making the coating hard and brittle with high internal stress. After adding sodium dodecyl sulfate, the surface tension is significantly reduced, and the hydrogen bubbles precipitated during the electrodeposition process are difficult to stay on the cathode surface, thus preventing the generation of pinholes on the foil layer.

[0049] Example 2

[0050] Mix 120 g / L nickel sulfate hexahydrate, 30 g / L nickel chloride hexahydrate, 100 g / L ferrous sulfate heptahydrate, 30 g / L copper sulfate pentahydrate and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 55 °C and stir vigorously for 30 min until completely dissolved. Add 60 g / L sodium citrate and then add 10 g / L ascorbic acid, and continue stirring. Then add 5 g / L saccharin, 0.5 g / L sodium dodecylbenzenesulfonate SBDS and 8 mL / L brightener 791. Adjust the pH of the electrolyte to 3, and then add 50 g / L boric acid. Connect the direct current power supply, the cathode current density is 15 A / dm 2 , the alloy plating time is 10 min, and the peeled alloy foil is rinsed with pure water and dried. The obtained copper alloy foil has a thickness of 12 μm, a room temperature tensile strength of 1100 MPa, a room temperature elongation of 5.8%, a high temperature tensile strength of 1000 MPa, and a matte surface roughness Rz of 0.3 μm.

[0051] SBDS promotes the crystallization nucleation of the alloy foil, accelerates the movement of electrons to the deposition interface, thus achieving the effect of grain refinement. And at high current density, it can effectively relieve the cracking of the foil surface. As a secondary brightener, brightener 791 can also be used as a leveling agent.

[0052] Example 3

[0053] Mix 100 g / L nickel sulfate hexahydrate, 40 g / L nickel chloride hexahydrate, 80 g / L ferrous sulfate heptahydrate, 20 g / L copper sulfate pentahydrate, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 60 °C and stir vigorously for 30 min until completely dissolved. Add 80 g / L xylitol, mix, then add 20 g / L ascorbic acid, and continue stirring. Then add 5 g / L saccharin sodium, 0.5 g / L sodium dodecylbenzenesulfonate SBDS, and 3 mL / L brightener 791. Adjust the pH of the electrolyte to 5, and then add 50 g / L boric acid. Connect a DC power supply, with a cathode current density of 15 A / dm 2 , the alloy plating time is 10 min. Peel the alloy foil, rinse it with pure water, and dry it. The obtained copper alloy foil has a thickness of 6 μm, a normal temperature tensile strength of 900 MPa, a normal temperature elongation of 4.9%, a high temperature tensile strength of 850 MPa, and a surface roughness Rz of 0.8 μm.

[0054] Using saccharin sodium as an additive and adding it to the electrolyte, saccharin sodium reduces the cathodic overpotential of electrodeposition in this complex system, promotes the electrodeposition of copper alloy, and accelerates the crystallization nucleation of copper alloy to achieve the effect of refining grains, but its effect of relieving stress and reducing cracking is not obvious. It inhibits the oxidation of divalent iron ions and more effectively ensures the stability of divalent iron ions in the electrolyte.

[0055] Example 4

[0056] Mix 110 g / L nickel sulfate hexahydrate, 45 g / L nickel chloride hexahydrate, 70 g / L ferrous sulfate heptahydrate, 80 g / L copper sulfate pentahydrate, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 65 °C and stir vigorously for 30 min until completely dissolved. Add 55 g / L xylitol, mix, then add 28 g / L ascorbic acid, and continue stirring. Then add 30 g / L saccharin sodium, 1 g / L sodium dodecylbenzenesulfonate SBDS, and 1 mL / L brightener 791. Adjust the pH of the electrolyte to 4, and then add 30 g / L boric acid. Connect a DC power supply, with a cathode current density of 10 A / dm 2 , the alloy plating time is 10 min. Peel the alloy foil, rinse it with pure water, and dry it. The obtained copper alloy foil has a thickness of 12 μm, a normal temperature tensile strength of 1070 MPa, a normal temperature elongation of 6.1%, a high temperature tensile strength of 940 MPa, and a surface roughness Rz of 0.7 μm.

[0057] Example 5

[0058] Mix 140 g / L nickel sulfate hexahydrate, 35 g / L nickel chloride hexahydrate, 65 g / L ferrous sulfate heptahydrate, 20 g / L copper sulfate pentahydrate, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 45 °C and stir vigorously for 30 min until completely dissolved. Add 80 g / L citric acid, mix, then add 15 g / L ascorbic acid, and continue stirring. Then add 8 g / L saccharin sodium, 0.2 g / L sodium dodecylbenzenesulfonate SBDS, and 5 mL / L brightener 791. Adjust the pH of the electrolyte to 4.7, and then add 40 g / L boric acid. Connect the DC power supply, with the cathode current density at 25 A / dm 2 , the alloy plating time is 12 min. Peel off the alloy foil, rinse it with pure water, and dry it. The obtained copper alloy foil has a thickness of 8 μm, a tensile strength at room temperature of 860 MPa, an elongation at room temperature of 8.3%, a tensile strength at high temperature reaching 800 MPa, and a roughness Rz of the matte surface of 0.9 μm.

[0059] Example 6

[0060] Mix 130 g / L nickel sulfate hexahydrate, 45 g / L nickel chloride hexahydrate, 65 g / L ferrous sulfate heptahydrate, 20 g / L copper sulfate pentahydrate, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 70 °C and stir vigorously for 30 min until completely dissolved. Add 30 g / L xylitol, mix, then add 12 g / L ascorbic acid, and continue stirring. Then add 3 g / L saccharin sodium, 0.1 g / L sodium dodecylbenzenesulfonate SBDS, and 4 mL / L brightener 791. Adjust the pH of the electrolyte to 3.5, and then add 45 g / L boric acid. Connect the DC power supply, with the cathode current density at 30 A / dm 2 , the alloy plating time is 17 min. Peel off the alloy foil, rinse it with pure water, and dry it. The obtained copper alloy foil has a thickness of 12 μm, a tensile strength at room temperature of 1000 MPa, an elongation at room temperature of 8.0%, a tensile strength at high temperature reaching 980 MPa, and a roughness Rz of the matte surface of 0.7 μm.

[0061] Comparative Example 1

[0062] Differing from Example 1, nickel-iron binary alloy foil is prepared without adding copper sulfate pentahydrate, and the other conditions are the same as those in Example 1.

[0063] Mix 150 g / L nickel sulfate hexahydrate, 50 g / L nickel chloride hexahydrate, 50 g / L ferrous sulfate heptahydrate, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 50 °C and stir vigorously for 30 min until completely dissolved. Add 40 g / L citric acid, mix, and then add 20 g / L ascorbic acid. Continue stirring. Then add 3 g / L saccharin, 0.3 g / L sodium dodecyl sulfate, and 5 mL / L brightener 791. Adjust the pH of the electrolyte to 3, and then add 50 g / L boric acid. Connect a DC power supply, with a cathode current density of 20 A / dm 2 , and the alloy plating time is 20 min. Flake off the alloy foil, rinse it with pure water, and dry it.

[0064] The obtained nickel-iron alloy foil has poorer electrical conductivity than copper foil. Compared with the flexibility of copper foil, the nickel-iron alloy foil has higher rigidity and poorer adaptability in scenarios such as flexible circuits and bendable devices, which is not conducive to its application in lithium batteries.

[0065] Comparative Example 2

[0066] Differing from Example 1, prepare a nickel-copper binary alloy foil without adding ferrous sulfate heptahydrate and ascorbic acid, and the other conditions are the same as those in Example 1.

[0067] Mix 150 g / L nickel sulfate hexahydrate, 50 g / L nickel chloride hexahydrate, 20 g / L copper sulfate pentahydrate, and dilute sulfuric acid (1 mol / L) to obtain a composite electrolyte. Heat the electrolyte to 50 °C and stir vigorously for 30 min until completely dissolved. Add 40 g / L citric acid, mix, and continue stirring. Then add 3 g / L saccharin, 0.3 g / L sodium dodecyl sulfate, and 5 mL / L brightener 791. Adjust the pH of the electrolyte to 3, and then add 50 g / L boric acid. Connect a DC power supply, with a cathode current density of 20 A / dm 2 , and the alloy plating time is 20 min. Flake off the alloy foil, rinse it with pure water, and dry it. The obtained nickel-copper alloy foil has a thickness of 18 μm, a tensile strength of 500 MPa at room temperature, an elongation at room temperature of 4.5%, a tensile strength of 460 MPa at high temperature, and a surface roughness Rz of 2.1 μm.

[0068] Figure 3 is the SEM image of the copper alloy foil in Comparative Example 2, and it is found that the roughness is significantly greater than that of Examples 1-6. The tensile strength of Comparative Example 2 is less than that of Examples 1-6.

[0069] The nickel-iron-copper alloy foil of the present invention improves the tensile strength after high-temperature aging of the alloy foil and the corrosion resistance of the thin layer. The electrolytic nickel-iron-copper alloy foil solves the problems of complex processes and high production costs in the rolling method, and has broad practical value and market prospects.

Claims

1. A method for preparing an electrolytic nickel-iron-copper alloy foil, comprising the following steps: (1) mixing nickel salt, ferrous salt, copper salt and dilute sulfuric acid to obtain a composite electrolyte, heating the composite electrolyte to a working temperature, and stirring until the composite electrolyte is completely dissolved; (2) Adding a chelating agent, a stabilizer, and an additive to the composite electrolyte in sequence, adjusting the pH of the composite electrolyte to 3-5, and then adding a buffer, and performing direct current electrolysis and electrodeposition to obtain a nickel-iron-copper alloy foil.

2. The preparation method according to claim 1, characterized in that: The nickel salt in step (1) is one or more of nickel sulfate hexahydrate and nickel chloride hexahydrate, with a concentration of 130-200 g / L; the ferrous salt is ferrous sulfate heptahydrate, with a concentration of 50-100 g / L; and the copper salt is copper sulfate pentahydrate, with a concentration of 10-100 g / L.

3. The preparation method according to claim 1, characterized in that: The working temperature in step (1) is 45-70°C.

4. The preparation method according to claim 1, characterized in that: The complexing agent in step (2) is one or more of citric acid, sodium citrate, xylitol, sorbitol and mannitol, with a concentration of 30-80 g / L.

5. The preparation method according to claim 1, characterized in that: The stabilizer in step (2) is ascorbic acid with a concentration of 5-30 g / L.

6. The preparation method according to claim 1, characterized in that: The additives in step (2) include one or more of a wetting agent and a brightening agent, and the concentration is 0.1-10 g / L.

7. The preparation method according to claim 1, characterized in that: The buffer in step (2) is boric acid with a concentration of 30-60 g / L.

8. The preparation method according to claim 1, characterized in that: The DC electrolytic deposition current density in step (2) is 8-30A / dm 2 , time is 10-20min.

9. The preparation method according to claim 1, characterized in that: The nickel-iron-copper alloy foil obtained in the step (2) has a tensile strength of 800-1100 MPa, an elongation at room temperature of 3-8%, and a roughness Rz of 0.3-0.8 μm.

10. The preparation method according to claim 1, characterized in that: The nickel-iron-copper alloy foil obtained in the step (2) is applied to lithium batteries or electronic circuits.

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