A method for preparing high-strength and high-conductivity copper-silver alloy foil by cyanide-free electroplating

Abstract

The application discloses a method for preparing high-strength and high-conductivity copper-silver alloy foil by cyanide-free electroplating. The method adopts a cyanide-free complexing agent system, which comprises pyrophosphate, organic phosphoric acid, iodide, conductive salt and pH regulator, and is matched with copper sulfate and silver nitrate to prepare an electroplating solution. The high-strength and high-conductivity copper-silver alloy foil is prepared by a direct current electroplating process under the condition of a pure titanium cathode and a pure copper anode. The method does not need to use cyanide, is environmentally friendly and safe, and the prepared copper-silver alloy foil has excellent comprehensive performance, i.e. the tensile strength is greater than or equal to 850 mPa, the electrical conductivity is greater than or equal to 65% IACS, the silver content is less than or equal to 10%, the thickness is 6-12 microns, the roughness Ra value of the rough surface is less than or equal to 4.5 microns, and the Rz value is less than or equal to 2.6 microns. The application overcomes the technical problem that traditional copper foils are difficult to have high strength and high conductivity at the same time, and is suitable for high-end application fields such as electronic interconnection, flexible circuit and lithium ion battery current collector.

Description

Technical Field

[0001] This invention relates to the field of copper foil preparation technology, and specifically to a method for preparing high-strength, high-conductivity copper-silver alloy foil by cyanide-free electroplating. Background Technology

[0002] Copper foil, as a key material for electronic interconnects, flexible circuits, and current collectors in lithium-ion batteries, is crucial for the development of high-density, high-reliability electronic technologies through performance optimization. However, pure copper foil inherently suffers from the difficulty of balancing strength and conductivity, and is prone to corrosion and oxidation. Therefore, copper-silver alloys, which offer significantly improved strength while maintaining good conductivity, have become an important development direction for high-performance foil materials.

[0003] Currently, sheet copper-silver alloy materials are mainly prepared by traditional plastic processing techniques such as cold rolling and cold drawing. These methods are complex and lengthy, and it is difficult to obtain ultra-thin foils with uniform microstructures in a stable manner, which limits their application in high-end electronics.

[0004] Electrodeposition technology is considered an ideal method for preparing high-performance ultrathin copper-silver alloy foils due to its outstanding advantages such as near-net-shape forming, controllable microstructure, and high production efficiency. Previous studies have successfully prepared copper-silver alloys with nanocrystalline supersaturated solid solution structures through electrodeposition, exhibiting excellent comprehensive properties such as an ultimate tensile strength of 1 gPa and an electrical conductivity of approximately 70% IACS.

[0005] However, most existing studies on copper-silver alloy electrodeposition employ cyanide plating bath systems. Cyanide is extremely toxic, posing a serious threat to the ecological environment and production safety, and is inconsistent with the trend of green manufacturing. Therefore, developing new complexation systems based on environmentally friendly ligands to achieve controllable preparation of high-performance copper-silver alloy foils through green electrodeposition processes, and systematically revealing the intrinsic relationship between its process, microstructure, and properties, has become a key technical problem urgently needing breakthroughs in this field, possessing significant scientific value and application prospects. Summary of the Invention

[0006] The purpose of this invention is to solve the problem that copper foil is difficult to have both high conductivity and high tensile strength, and to provide a cyanide-free complexing agent and electroplating solution for preparing high-strength and high-conductivity copper-silver alloy foil, as well as the high-strength and high-conductivity copper-silver alloy foil and its preparation method.

[0007] To achieve the above objectives, a first aspect of the present invention provides a complexing agent for preparing high-strength, high-conductivity copper-silver alloy foil using cyanide-free electroplating, wherein the complexing agent comprises: pyrophosphate, organic phosphoric acid, iodide, conductive salt, and pH adjuster; the pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate; the organic phosphoric acid is selected from one or more of hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, and diethylenetriaminepentamethylenephosphonic acid; the iodide is selected from one or more of potassium iodide and sodium iodide; and the mass ratio of the pyrophosphate, organic phosphoric acid, iodide, conductive salt, and pH adjuster is 10-40:10-50:80-340:3-40:10-100.

[0008] A second aspect of the present invention provides an electroplating solution containing the complexing agent described in the first aspect of the present invention; wherein, based on the total mass of the electroplating solution, the electroplating solution comprises: copper sulfate at a mass content of 20-40 g / L, silver nitrate at a mass content of 0.1-1 g / L, pyrophosphate at a mass content of 10-40 g / L, organophosphate at a mass content of 10-50 g / L, iodide at a mass content of 80-340 g / L, conductive salt at a mass content of 3-40 g / L, and pH adjuster at a mass content of 10-100 g / L.

[0009] A third aspect of the present invention provides a method for preparing high-strength, high-conductivity copper-silver alloy foil by cyanide-free electroplating, the method comprising the following steps: (1) Pyrophosphate, organic phosphoric acid, iodide, conductive salt, copper sulfate, silver nitrate and pH adjuster are dissolved and mixed evenly to obtain an electroplating solution; wherein, the pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate; the organic phosphoric acid is selected from one or more of hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid and diethylenetriaminepentamethylenephosphonic acid; the iodide is selected from one or more of potassium iodide and sodium iodide; (2) The electroplating solution is subjected to DC electroplating to obtain the high-strength and high-conductivity copper-silver alloy foil.

[0010] A fourth aspect of the present invention provides a high-strength, high-conductivity copper-silver alloy foil, prepared by any of the above-described methods for preparing high-strength, high-conductivity copper-silver alloy foil by cyanide-free electroplating, wherein the high-strength, high-conductivity copper-silver alloy foil has a tensile strength ≥850 mPa, preferably 900-1200 mPa; a conductivity ≥65% IACS, preferably 70-85% IACS; a silver content ≤10%, preferably 4.5-9.0%; a thickness of 6-12 μm, preferably 6.5-11.5 μm; a surface roughness Ra value ≤4.5 μm, preferably 0.1-0.4 μm; and a Rz value ≤2.6 μm, preferably 0.85-2.57 μm.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a cyanide-free electroplating system, utilizing a composite complexing agent composed of pyrophosphate, organic phosphoric acid, and iodides to achieve stable co-deposition of copper and silver ions. This method is environmentally friendly, simple, and produces copper-silver alloy foils with both high strength and high conductivity. The tensile strength can reach over 977 mPa, and the conductivity can reach over 71.8% IACS. The surface is smooth, and the microstructure is uniform, making it suitable for high-end electronic interconnects, flexible circuits, and lithium-ion battery current collectors. Attached Figure Description

[0012] Figure 1 This is a grain boundary distribution diagram of the copper-silver alloy foil prepared in Example 1 of the present invention; Figure 2 Electron backscatter diffraction (EBSD) pattern of a cross-section of a copper-silver alloy foil prepared in Example 1 of this invention; Figure 3 This is a grain size diagram of the copper-silver alloy foil prepared in Example 1 of the present invention; Figure 4 The IPF (inverse pole figure) of the copper-silver alloy foil prepared in Example 1 of the present invention; Figure 5 The surface morphology SEM image of the copper-silver alloy foil prepared in Example 1 of this invention; Figure 6 This is a cross-sectional SEM image of the copper-silver alloy foil prepared in Example 1 of the present invention; Figure 7 The above is a SEM image of the surface morphology of the copper-silver alloy foil prepared in Comparative Example 1 of this invention. Figure 8 This is a SEM image of the surface morphology of the copper foil prepared in Comparative Example 3 of this invention; Figure 9 This is a SEM image of the surface morphology of the copper foil prepared in Comparative Example 4 of the present invention. Detailed Implementation

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0014] The first aspect of the present invention provides a cyanide-free complexing agent for preparing high-strength, high-conductivity copper-silver alloy foil, wherein the complexing agent comprises: pyrophosphate, organic phosphoric acid, iodide, conductive salt, and pH adjuster; the pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate; the organic phosphoric acid is selected from one or more of hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, and diethylenetriaminepentamethylenephosphonic acid; the iodide is selected from one or more of potassium iodide and sodium iodide; the mass ratio of the pyrophosphate, organic phosphoric acid, iodide, conductive salt, and pH adjuster is 10-40:10-50:80-340:3-40:10-100.

[0015] In this invention, the inventors discovered through research that by adding a complexing agent containing at least one pyrophosphate, at least one organic phosphoric acid, and at least one iodide to the electroplating solution and performing electrodeposition using DC electroplating, a copper-silver alloy foil with both high tensile strength and high conductivity can be obtained.

[0016] In a preferred embodiment of the present invention, the conductive salt is a nitrate, wherein the nitrate is selected from one or more of sodium nitrate and potassium nitrate.

[0017] In a preferred embodiment of the present invention, the pH adjuster is a strong alkaline hydroxide, wherein the strong alkaline hydroxide is selected from one or more of sodium hydroxide and potassium hydroxide. In this invention, sodium hydroxide and potassium hydroxide are conventional reagents in the art and can be commercially available products purchased through commercial channels.

[0018] In this invention, the inventors discovered through research that adding at least one pH adjuster can significantly improve the stability of the electroplating solution and simultaneously help improve copper-silver co-deposition. Preferably, the pH adjuster can be sodium hydroxide, preferably sodium hydroxide with a mass concentration of 30-80 g / L; or, the pH adjuster can be potassium hydroxide, preferably potassium hydroxide with a mass concentration of 20-60 g / L.

[0019] In a preferred embodiment of the present invention, the mass ratio of the pyrophosphate, organic phosphoric acid, iodide, conductive salt and pH adjuster is 15-35:20-40:120-250:5-20:20-80.

[0020] In this invention, when the mass ratio of pyrophosphate, organic phosphoric acid, iodide, conductive salt, and pH adjuster is within the range specified above, the prepared copper-silver alloy foil has higher tensile strength and higher electrical conductivity.

[0021] A second aspect of the present invention provides an electroplating solution containing the complexing agent described in the first aspect of the present invention, wherein, based on the total mass of the electroplating solution, the electroplating solution comprises: copper sulfate at a mass content of 20-40 g / L, silver nitrate at a mass content of 0.1-1 g / L, pyrophosphate at a mass content of 10-40 g / L, organophosphate at a mass content of 10-50 g / L, iodide at a mass content of 80-340 g / L, conductive salt at a mass content of 3-40 g / L, and pH adjuster at a mass content of 10-100 g / L.

[0022] In a preferred embodiment of the present invention, the electroplating solution comprises, by mass, copper sulfate at a content of 25-35 g / L, silver nitrate at a content of 0.2-0.7 g / L, pyrophosphate at a content of 15-35 g / L, organophosphate at a content of 20-40 g / L, iodide at a content of 120-330 g / L, conductive salt at a content of 5-20 g / L, and pH adjuster at a content of 20-80 g / L.

[0023] In a preferred embodiment of the present invention, the solvent of the electroplating solution is water, preferably deionized water.

[0024] A third aspect of the present invention provides a method for preparing a high-strength, high-conductivity copper-silver alloy foil, wherein the method includes the following steps: (1) Pyrophosphate, organic phosphoric acid, iodide, conductive salt, copper sulfate, silver nitrate and pH adjuster are dissolved and mixed evenly to obtain an electroplating solution; wherein, the pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate; the organic phosphoric acid is selected from one or more of hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid and diethylenetriaminepentamethylenephosphonic acid; the iodide is selected from one or more of potassium iodide and sodium iodide; (2) The electroplating solution is subjected to DC electroplating to obtain the high-strength and high-conductivity copper-silver alloy foil.

[0025] In this invention, the inventors discovered through research that an electroplating solution containing at least one pyrophosphate, at least one organic phosphoric acid, at least one iodide, and at least one pH adjuster can produce high-quality copper-silver alloy foil with a tensile strength ≥850mPa and an electrical conductivity ≥65% IACS under the action of DC electroplating.

[0026] In step (1): In a preferred embodiment of the present invention, the conductive salt is a nitrate, selected from one or more of sodium nitrate and potassium nitrate.

[0027] In a preferred embodiment of the present invention, the pH adjuster is a strong alkaline hydroxide, selected from one or more of sodium hydroxide and potassium hydroxide.

[0028] In this invention, the pH adjuster can be sodium hydroxide, preferably sodium hydroxide with a mass of 30-80 g / L; or, the pH adjuster can be potassium hydroxide, preferably potassium hydroxide with a mass of 20-60 g / L.

[0029] In a preferred embodiment of the present invention, pyrophosphate, organic phosphoric acid, iodide, conductive salt, and pH adjuster are first dissolved in water to obtain a complexing agent mixture. Then, the complexing agent mixture, copper sulfate solution, and silver nitrate solution are mixed and subjected to self-circulation mixing to obtain an electroplating solution. The copper sulfate is preferably copper sulfate pentahydrate. The self-circulation temperature is 30-60 °C, preferably 40-55 °C. The self-circulation time is 5-35 min, preferably 10-30 min. The self-circulation rate is 0.1-0.5 m / s. 3 / min, preferably 0.15-0.3m 3 / min.

[0030] In a preferred embodiment of the present invention, the electroplating solution comprises, by weight, the following: copper sulfate at a mass content of 20-40 g / L, preferably 25-35 g / L; silver nitrate at a mass content of 0.1-1 g / L, preferably 0.2-0.7 g / L; pyrophosphate at a mass content of 10-40 g / L, preferably 15-35 g / L; organophosphate at a mass content of 10-50 g / L, preferably 20-40 g / L; iodide at a mass content of 80-340 g / L, preferably 120-330 g / L; conductive salt at a mass content of 3-40 g / L, preferably 5-20 g / L; and pH adjuster at a mass content of 10-100 g / L, preferably 20-80 g / L.

[0031] In step (2), in a preferred embodiment of the present invention, the cathode of the DC electroplating is pure titanium and the anode is pure copper.

[0032] In a preferred embodiment of the present invention, the operating conditions for DC electroplating include: an electrolyte temperature of 30-80°C, preferably 40-60°C; and an electrolyte circulation rate of 8-14 L / min, preferably 10-12 L / min.

[0033] In a preferred embodiment of the present invention, the operating conditions for DC electroplating further include: a current density of 0.4-2 A / dm³. 2 Preferably, it is 0.5-1.5 A / dm 2The electroplating time is 40-100 min, preferably 50-90 min.

[0034] A fourth aspect of the present invention provides a high-strength, high-conductivity copper-silver alloy foil, wherein the high-strength, high-conductivity copper-silver alloy foil has a tensile strength ≥850 mPa, preferably 900-1200 mPa; and an electrical conductivity ≥65% IACS, preferably 70-85% IACS; In a preferred embodiment of the present invention, the silver content of the copper-silver alloy foil is ≤10%, preferably 4.5-9.0%; the thickness is 6-12 μm, preferably 6.5-11.5 μm; the surface roughness Ra value is ≤4.5 μm, preferably 0.1-0.4 μm; and the Rz value is ≤2.6 μm, preferably 0.85-2.57 μm.

[0035] The present invention will be described in detail below through embodiments. Example 1

[0036] 1) First, add potassium pyrophosphate, hydroxyethylidene diphosphate, potassium iodide, sodium nitrate, and sodium hydroxide to deionized water and mix thoroughly to obtain a complexing agent mixture. Then, add the complexing agent mixture to a copper sulfate solution, followed by silver nitrate solution. The mixture is then circulated at 50 °C at a rate of 0.2 m / s. 3 The electroplating solution was obtained by circulating the solution at a rate of 1 / min for 20 minutes. In the obtained electroplating solution, the concentration of copper sulfate was 27 g / L, the concentration of silver nitrate was 0.2 g / L, the mass concentration of potassium pyrophosphate was 16.5 g / L, the mass concentration of hydroxyethylidene diphosphate was 30 g / L, the mass concentration of potassium iodide was 166 g / L, the mass concentration of sodium nitrate was 20 g / L, and the mass concentration of sodium hydroxide was 30 g / L. 2) The above electroplating solution was placed in an electrolytic cell, with pure titanium as the cathode and pure copper as the anode, and DC electroplating was performed at 40°C and a solution circulation rate of 11 L / min to obtain a high-strength, high-conductivity copper-silver alloy foil; wherein the DC electroplating current density was 0.5 A / dm³. 2 The electroplating time is 75 minutes. Example 2

[0037] 1) First, add sodium pyrophosphate, aminotrimethylenephosphonic acid, sodium iodide, sodium nitrate, and sodium hydroxide to deionized water and mix thoroughly to obtain a complexing agent mixture. Then, add the complexing agent mixture to a copper sulfate solution, followed by silver nitrate solution. The mixture is then circulated at 50 °C at a rate of 0.2 m / s. 3 The electroplating solution was obtained by circulating the solution at a rate of 1 / min for 20 minutes. In the obtained electroplating solution, the concentration of copper sulfate is 30 g / L, the concentration of silver nitrate is 0.4 g / L, the mass concentration of sodium pyrophosphate is 20 g / L, the mass concentration of aminotrimethylenephosphonic acid is 20 g / L, the mass concentration of sodium iodide is 150 g / L, the mass concentration of sodium nitrate is 30 g / L, and the mass concentration of sodium hydroxide is 40 g / L. 2) The above electroplating solution was placed in an electrolytic cell, with pure titanium as the cathode and pure copper as the anode, and direct current electroplating was performed at 50°C and a solution circulation rate of 11 L / min to obtain a high-strength, high-conductivity copper-silver alloy foil; wherein the current density of the direct current electroplating was 1 A / dm³. 2 The electroplating time is 70 minutes. Example 3

[0038] 1) First, add potassium pyrophosphate, ethylenediaminetetramethylenephosphonic acid, potassium iodide, sodium nitrate, and sodium hydroxide to deionized water and mix thoroughly to obtain a complexing agent mixture. Then, add the complexing agent mixture to a copper sulfate solution, followed by silver nitrate solution. The mixture is then circulated at 50 °C at a rate of 0.2 m / s. 3 The electroplating solution was obtained by circulating the solution at a rate of 1 / min for 20 minutes. In the obtained electroplating solution, the concentration of copper sulfate is 35 g / L, the concentration of silver nitrate is 0.5 g / L, the mass concentration of potassium pyrophosphate is 20 g / L, the mass concentration of aminotrimethylenephosphonic acid is 15 g / L, the mass concentration of potassium iodide is 200 g / L, the mass concentration of sodium nitrate is 20 g / L, and the mass concentration of sodium hydroxide is 50 g / L. 2) The above electroplating solution was placed in an electrolytic cell, with pure titanium as the cathode and pure copper as the anode, and DC electroplating was performed at 60°C and a solution circulation rate of 10 L / min to obtain a high-strength, high-conductivity copper-silver alloy foil; wherein the DC electroplating current density was 1.5 A / dm³. 2 The electroplating time is 50 minutes. Example 4

[0039] 1) First, add potassium pyrophosphate, diethylenetriaminepentamethylenephosphonic acid, potassium iodide, sodium nitrate, and sodium hydroxide to deionized water and mix thoroughly to obtain a complexing agent mixture. Then, add the complexing agent mixture to a copper sulfate solution, followed by silver nitrate solution. The mixture is then circulated at 50 °C at a rate of 0.2 m / s. 3 The electroplating solution was obtained by circulating the solution at a rate of 1 / min for 20 minutes. In the obtained electroplating solution, the concentration of copper sulfate is 40 g / L, the concentration of silver nitrate is 1 g / L, the mass concentration of potassium pyrophosphate is 30 g / L, the mass concentration of aminotrimethylenephosphonic acid is 20 g / L, the mass concentration of potassium iodide is 150 g / L, the mass concentration of potassium nitrate is 30 g / L, and the mass concentration of potassium hydroxide is 35 g / L. 2) The above electroplating solution was placed in an electrolytic cell, with pure titanium as the cathode and pure copper as the anode, and direct current electroplating was performed at 45°C and a solution circulation rate of 12 L / min to obtain a high-strength, high-conductivity copper-silver alloy foil; wherein the current density of the direct current electroplating was 0.8 A / dm³. 2 The electroplating time is 60 minutes. Example 5

[0040] 1) First, add potassium pyrophosphate, hydroxyethylidene diphosphate, potassium iodide, sodium nitrate, and sodium hydroxide to deionized water and mix thoroughly to obtain a complexing agent mixture. Then, add the complexing agent mixture to a copper sulfate solution, followed by silver nitrate solution. The mixture is then circulated at 50 °C at a rate of 0.2 m / s. 3 The electroplating solution was obtained by circulating the solution at a rate of 1 / min for 20 minutes. In the obtained electroplating solution, the concentration of copper sulfate was 27 g / L, the concentration of silver nitrate was 0.2 g / L, the mass concentration of potassium pyrophosphate was 16.5 g / L, the mass concentration of hydroxyethylidene diphosphate was 30 g / L, the mass concentration of potassium iodide was 166 g / L, the mass concentration of sodium nitrate was 20 g / L, and the mass concentration of sodium hydroxide was 30 g / L. 2) The above electroplating solution was placed in an electrolytic cell, with pure titanium as the cathode and pure copper as the anode, and DC electroplating was performed at 40°C and a solution circulation rate of 11 L / min to obtain a high-strength, high-conductivity copper-silver alloy foil; wherein the DC electroplating current density was 0.7 A / dm³. 2 The electroplating time is 75 minutes. Example 6

[0041] 1) First, add potassium pyrophosphate, hydroxyethylidene diphosphate, potassium iodide, sodium nitrate, and sodium hydroxide to deionized water and mix thoroughly to obtain a complexing agent mixture. Then, add the complexing agent mixture to a copper sulfate solution, followed by silver nitrate solution. The mixture is then circulated at 50 °C at a rate of 0.2 m / s. 3 The electroplating solution was obtained by circulating the solution at a rate of 1 / min for 20 minutes. In the obtained electroplating solution, the concentration of copper sulfate was 27 g / L, the concentration of silver nitrate was 0.2 g / L, the mass concentration of potassium pyrophosphate was 16.5 g / L, the mass concentration of hydroxyethylidene diphosphate was 30 g / L, the mass concentration of potassium iodide was 166 g / L, the mass concentration of sodium nitrate was 20 g / L, and the mass concentration of sodium hydroxide was 30 g / L. 2) The above electroplating solution was placed in an electrolytic cell, with pure titanium as the cathode and pure copper as the anode, and direct current electroplating was performed at 40°C and a solution circulation rate of 11 L / min to obtain a high-strength, high-conductivity copper-silver alloy foil; wherein the current density of the direct current electroplating was 0.9 A / dm³. 2 The electroplating time is 75 minutes. Example 7

[0042] 1) First, add potassium pyrophosphate, hydroxyethylidene diphosphate, potassium iodide, sodium nitrate, and sodium hydroxide to deionized water and mix thoroughly to obtain a complexing agent mixture. Then, add the complexing agent mixture to a copper sulfate solution, followed by silver nitrate solution. The mixture is then circulated at 50 °C at a rate of 0.2 m / s. 3 The electroplating solution was obtained by circulating the solution at a rate of 1 / min for 20 minutes. In the obtained electroplating solution, the concentration of copper sulfate was 27 g / L, the concentration of silver nitrate was 0.2 g / L, the mass concentration of potassium pyrophosphate was 16.5 g / L, the mass concentration of hydroxyethylidene diphosphate was 30 g / L, the mass concentration of potassium iodide was 166 g / L, the mass concentration of sodium nitrate was 20 g / L, and the mass concentration of sodium hydroxide was 30 g / L. 2) The above electroplating solution was placed in an electrolytic cell, with pure titanium as the cathode and pure copper as the anode, and DC electroplating was performed at 40°C and a solution circulation rate of 11 L / min to obtain a high-strength, high-conductivity copper-silver alloy foil; wherein the DC electroplating current density was 1.2 A / dm³. 2 The electroplating time is 75 minutes. Example 8

[0043] 1) First, add potassium pyrophosphate, hydroxyethylidene diphosphate, potassium iodide, sodium nitrate, and sodium hydroxide to deionized water and mix thoroughly to obtain a complexing agent mixture. Then, add the complexing agent mixture to a copper sulfate solution, followed by silver nitrate solution. The mixture is then circulated at 50 °C at a rate of 0.2 m / s. 3 The electroplating solution was obtained by circulating the solution at a rate of 1 / min for 20 minutes. In the obtained electroplating solution, the concentration of copper sulfate was 27 g / L, the concentration of silver nitrate was 0.2 g / L, the mass concentration of potassium pyrophosphate was 16.5 g / L, the mass concentration of hydroxyethylidene diphosphate was 30 g / L, the mass concentration of potassium iodide was 166 g / L, the mass concentration of sodium nitrate was 20 g / L, and the mass concentration of sodium hydroxide was 30 g / L. 2) The above electroplating solution was placed in an electrolytic cell, with pure titanium as the cathode and pure copper as the anode, and direct current electroplating was performed at 40°C and a solution circulation rate of 11 L / min to obtain a high-strength, high-conductivity copper-silver alloy foil; wherein the current density of the direct current electroplating was 1.5 A / dm³. 2 The electroplating time is 75 minutes.

[0044] Comparative Example 1 Similar to Example 1, except that the pure copper plate in step (2) is replaced with an iridium-coated titanium plate.

[0045] Comparative Example 2 Similar to Example 2, except that the DC electroplating in step (2) is modified to pulse electroplating.

[0046] 1) First, add sodium pyrophosphate, aminotrimethylenephosphonic acid, sodium iodide, sodium nitrate, and sodium hydroxide to deionized water and mix thoroughly to obtain a complexing agent mixture. Then, add the complexing agent mixture to a copper sulfate solution, followed by silver nitrate solution. The mixture is then circulated at 50 °C at a rate of 0.2 m / s. 3 The electroplating solution was obtained by circulating the solution at a rate of 1 / min for 20 minutes. In the obtained electroplating solution, the concentration of copper sulfate is 30 g / L, the concentration of silver nitrate is 0.4 g / L, the mass concentration of sodium pyrophosphate is 20 g / L, the mass concentration of aminotrimethylenephosphonic acid is 20 g / L, the mass concentration of sodium iodide is 150 g / L, the mass concentration of sodium nitrate is 30 g / L, and the mass concentration of sodium hydroxide is 40 g / L. 2) Place the above electroplating solution into an electrolytic cell, using pure titanium as the cathode and pure copper as the anode, at 40°C, with a solution circulation rate of 1 m / s. 3 Pulse electroplating was performed under conditions of 1 A / dm² to obtain copper-silver alloy foil; wherein the pulse electroplating current density was 1 A / dm². 2 The pulse duty cycle is 50%, the pulse frequency is 0.5Hz, and the electroplating time is 100min.

[0047] Comparative Example 3 Similar to Example 1, except that silver nitrate in step (2) is omitted to obtain pure copper foil.

[0048] Comparative Example 4 Commercially available 8μm lithium battery copper foil.

[0049] Test Example 1 The copper-silver alloy foils and copper foils prepared in Examples 1-8 and Comparative Examples 1-4 were subjected to performance tests, and the test results are shown in Table 1.

[0050] The thickness of the copper-silver alloy foil was tested using a scanning electron microscope, the roughness Ra and Rz of the copper-silver alloy foil and copper foil were tested using a Mahrmarsurf PS10 instrument, the tensile strength was tested using a universal tensile testing machine, the electrical conductivity was tested using an ST2253A four-probe tester, and the silver content was tested using inductively coupled plasma atomic emission spectrometry.

[0051] Table 1

[0052] As can be seen from the results in Table 1, the copper-silver alloy foils prepared in Examples 1-8 have a tensile strength ≥977MPa, an electrical conductivity ≥71.8%IACS, a silver content between 4.6-8.8wt.%, and a surface roughness Ra value ≤0.40μm and Rz value ≤2.57μm. They exhibit excellent performance and overcome the technical challenge of simultaneously achieving high tensile strength and high electrical conductivity in ordinary electrolytic copper foils.

[0053] Comparing Example 1 and Comparative Example 1, it is evident that using a pure copper plate as the anode significantly increases the tensile strength and conductivity of the copper-silver alloy foil, and helps to reduce the silver content of the copper-silver alloy foil. Comparing Example 2 and Comparative Example 2, it is evident that direct current electroplating can substantially improve the tensile strength of the copper-silver alloy foil compared to pulse electroplating. Comparing Example 1 with Comparative Examples 3 and 4, it is evident that the copper-silver alloy foil prepared using the electroplating solution provided by this invention has better overall performance than pure copper foil.

[0054] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A complexing agent for preparing high-strength, high-conductivity copper-silver alloy foil using cyanide-free electroplating, characterized in that, The complexing agent comprises: pyrophosphate, organic phosphoric acid, iodide, conductive salt, and pH adjuster; wherein, the pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate; the organic phosphoric acid is selected from one or more of hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, and diethylenetriaminepentamethylenephosphonic acid; the iodide is selected from one or more of potassium iodide and sodium iodide; the mass ratio of pyrophosphate, organic phosphoric acid, iodide, conductive salt, and pH adjuster is 10-40:10-50:80-340:3-40:10-100; the conductive salt is a nitrate; the nitrate is selected from one or more of sodium nitrate and potassium nitrate; the pH adjuster is a strongly alkaline hydroxide; the strongly alkaline hydroxide is selected from one or more of sodium hydroxide and potassium hydroxide.

2. An electroplating solution containing the complexing agent of claim 1, characterized in that, Copper sulfate with a mass content of 20-40 g / L, silver nitrate with a mass content of 0.1-1 g / L, pyrophosphate with a mass content of 10-40 g / L, organophosphate with a mass content of 10-50 g / L, iodide with a mass content of 80-340 g / L, conductive salt with a mass content of 3-40 g / L, and pH adjuster with a mass content of 10-100 g / L.

3. An electroplating solution containing the complexing agent of claim 2, characterized in that, The composition includes copper sulfate (25-35 g / L), silver nitrate (0.2-0.7 g / L), pyrophosphate (15-35 g / L), organophosphate (20-40 g / L), iodide (120-330 g / L), conductive salt (5-20 g / L), and pH adjuster (20-80 g / L).

4. A method for preparing high-strength, high-conductivity copper-silver alloy foil by cyanide-free electroplating, characterized in that, Includes the following steps: (1) Pyrophosphate, organic phosphoric acid, iodide, conductive salt, copper sulfate, silver nitrate and pH adjuster are dissolved and mixed evenly to obtain an electroplating solution; wherein, the pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate; the organic phosphoric acid is selected from one or more of hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid and diethylenetriaminepentamethylenephosphonic acid; the iodide is selected from one or more of potassium iodide and sodium iodide; the conductive salt is a nitrate selected from one or more of sodium nitrate and potassium nitrate; the pH adjuster is a strong alkaline hydroxide selected from one or more of sodium hydroxide and potassium hydroxide. (2) The electroplating solution is subjected to DC electroplating to obtain the high-strength and high-conductivity copper-silver alloy foil; The electroplating solution, based on its total mass, comprises: copper sulfate at a mass content of 20-40 g / L, silver nitrate at a mass content of 0.1-1 g / L, pyrophosphate at a mass content of 10-40 g / L, organic phosphoric acid at a mass content of 10-50 g / L, iodide at a mass content of 80-340 g / L, conductive salt at a mass content of 3-40 g / L, and pH adjuster at a mass content of 10-100 g / L.

5. The method for preparing high-strength, high-conductivity copper-silver alloy foil by cyanide-free electroplating according to claim 4, characterized in that, The electroplating solution comprises, by mass, copper sulfate at a content of 25-35 g / L, silver nitrate at a content of 0.2-0.7 g / L, pyrophosphate at a content of 15-35 g / L, organic phosphoric acid at a content of 20-40 g / L, iodide at a content of 120-330 g / L, conductive salt at a content of 5-20 g / L, and pH adjuster at a content of 20-80 g / L.

6. The method for preparing high-strength, high-conductivity copper-silver alloy foil by cyanide-free electroplating according to any one of claims 4 or 5, characterized in that, The operating conditions for DC electroplating include: electrolyte temperature of 30-80℃; electrolyte circulation rate of 8-14 L / min; and current density of 0.4-2 A / dm³. 2 The electroplating time is 40-100 minutes.

7. The method for preparing high-strength, high-conductivity copper-silver alloy foil by cyanide-free electroplating according to any one of claims 6, characterized in that, The operating conditions for DC electroplating include: electrolyte temperature of 40-60℃; electrolyte circulation rate of 10-12 L / min; and current density of 0.5-1.5 A / dm³. 2 The electroplating time is 50-90 minutes.

8. A high-strength, high-conductivity copper-silver alloy foil, characterized in that, It is prepared by the method for preparing high-strength and high-conductivity copper-silver alloy foil by cyanide-free electroplating according to any one of claims 4-7, wherein the high-strength and high-conductivity copper-silver alloy foil has a tensile strength ≥850mPa; electrical conductivity ≥65% IACS; silver content ≤10%; thickness of 6-12μm; surface roughness Ra value ≤4.5 μm; and Rz value ≤2.6 μm.

9. A high-strength, high-conductivity copper-silver alloy foil, characterized in that, It is prepared by the method for preparing high-strength and high-conductivity copper-silver alloy foil by cyanide-free electroplating according to any one of claims 4-7. The high-strength and high-conductivity copper-silver alloy foil has a tensile strength of 900-1200 mPa, a conductivity of 70-85% IACS, a silver content of 4.5-9.0%, a thickness of 6.5-11.5 μm, a surface roughness Ra value of 0.1-0.4 μm, and a Rz value of 0.85-2.57 μm.

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