A preparation method of an electrolytic copper foil with a (111) texture

Abstract

The present invention belongs to the technical field of electrolytic copper foils, and particularly relates to a method for preparing an electrolytic copper foil with a (111) texture. The method for preparing an electrolytic copper foil with a (111) texture provided by the present invention includes the following steps: using a titanium substrate with a (0001) texture as the cathode, and performing electrodeposition in an electrolyte to obtain a fine-grained electrolytic copper foil with a (111) texture, wherein the average grain size of the electrolytic copper foil < 0.2 μm. The present invention utilizes the fact that the density of stable adsorption active sites of Cu on the (0001) crystal plane of titanium is relatively high, and the lattice matching degree between the (0001) atomic close-packed plane of titanium and the (111) atomic close-packed crystal plane of the copper foil is relatively high, which can reduce the formation energy of (111) copper crystal nuclei, promote the formation of (111) copper crystal nuclei, and further promote the formation of the (111) texture of the copper foil and grain refinement, thereby obtaining an ultrafine-grained electrolytic copper foil with a strong (111) texture and realizing the synergistic improvement of the comprehensive performance of the electrolytic copper foil.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic copper foils, and particularly relates to a method for preparing an electrolytic copper foil with a (111) texture. Background Art

[0002] Electrolytic copper foil is a key basic material for lithium battery current collectors, printed circuit boards and packaging substrates, and is widely used in fields such as chip packaging, printed circuits and new energy. In lithium batteries, electrolytic copper foil is the carrier of the negative electrode active material, playing the role of electron collection and conduction, and determining the energy density of the battery. In printed circuit boards and packaging substrates, electrolytic copper foil plays the role of interconnecting conduction, insulation and support, and determines the signal transmission speed, energy loss and characteristic impedance.

[0003] In industrial production, under the action of an electric field, copper ions in the copper sulfate electrolyte are reduced and deposited on the surface of the titanium cathode roller to form metallic copper. At the same time, the titanium cathode roller rotates continuously and uniformly, and copper ions are continuously electrodeposited on the surface of the cathode titanium. When the deposition reaches a certain thickness, it is peeled off and wound into a roll to form an electrolytic copper foil. In principle, electrolytic copper foil is the electrochemical continuous crystallization product of copper ions on the cathode titanium. During the electrocrystallization process, after the newly formed adsorbed copper atoms reach the surface of the cathode titanium, they nucleate and grow along the original crystal structure of the titanium substrate, gradually forming an initial deposition layer.

[0004] The microscopic structure of the cathode titanium surface directly affects the nucleation and growth process of copper ions, and thus affects the microscopic structure of the electrolytic copper foil. With the gradual high-density, multi-layer and thin-type development of integrated circuits, and at the same time, the development of lithium batteries towards high energy density and lightweight, this requires the copper foil to be thinner and thinner. At this time, the initial deposition layer of the ultra-thin copper foil is crucial for the entire electrolytic copper foil.

[0005] The grain refinement of electrolytic copper foil can make it have both high tensile strength and high elongation. Moreover, a large number of studies have shown that the (111) texture not only endows the electrolytic copper foil with good mechanical properties (tensile strength and elongation), but also is conducive to the uniform deposition nucleation of lithium during the charge and discharge process of lithium batteries, thereby improving the service life of lithium batteries. At present, most reports on the grain refinement and texture control of electrolytic copper foil focus on additive regulation.

[0006] The Chinese patent application with the publication number CN118028918A and the publication date of May 14, 2024 discloses a copper foil composite additive and a method for preparing an electrolytic copper foil with highly oriented crystal planes. The composite additive includes additive A as a brightening agent, additive B as a wetting agent, and additive C as a leveling agent. Additive A is at least one of sulfonated thiacalix[4]arene, sulfonated thiacalix[6]arene, and sulfonated thiacalix[8]arene. The rigid structure of sulfonated thiacalixarene enables the calixarenes adsorbed on the cathode to form an upward-oriented arrangement with sulfonic acid groups. Copper ions can only approach the cathode from the edge of the calixarene, resulting in the directional growth of copper grains, which is beneficial to the precipitation of the (111) crystal plane of copper, thereby improving the tensile strength of the copper foil.

[0007] However, in industrial production, a large amount of additives will not only increase the production cost of electrolytic copper foil, but also may introduce impurity elements into the copper foil. In addition, a large amount of additives poses a certain potential hazard to the environment. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for preparing an electrolytic copper foil with a (111) texture, and to solve the problem of using a large amount of additives when preparing an electrolytic copper foil with a (111) texture.

[0009] In order to solve the above technical problems, the technical solution of the method for preparing an electrolytic copper foil with a (111) texture of the present invention is as follows:

[0010] A method for preparing an electrolytic copper foil with a (111) texture, comprising the following steps: using a titanium substrate with a (0001) texture as the cathode, and performing electrodeposition in an electrolyte to obtain a fine-grained electrolytic copper foil with a (111) texture, and the average grain size of the electrolytic copper foil < 0.2 μm.

[0011] The present invention pioneerly provides a method for preparing an electrolytic copper foil with a (111) texture. By using a titanium substrate with a (0001) texture as the cathode, since the (0001) crystal plane of titanium is an atomic close-packed plane, the density of stable adsorption active sites of Cu on its surface is higher. Moreover, its lattice matching degree with the (111) atomic close-packed crystal plane of the copper foil is relatively high, which can reduce the formation energy of (111) copper crystal nuclei, facilitate the formation of (111) copper crystal nuclei, enable copper ions to nucleate uniformly and densely on the surface of the cathode titanium substrate, and then promote the formation of the (111) texture of the copper foil and grain refinement, thereby obtaining an ultrafine-grained electrolytic copper foil with a strong (111) texture and realizing the synergistic improvement of the comprehensive performance of the electrolytic copper foil.

[0012] In order to further improve the (0001) texture performance of the titanium substrate, preferably, the preparation method of the titanium substrate includes the following steps: hot-rolling the forged pure titanium at 400 - 450 °C, and then performing cold rolling and annealing.

[0013] In order to further improve the (0001) texture performance of the titanium substrate, preferably, the deformation amount during hot rolling is 60-70%.

[0014] In order to further improve the (0001) texture performance of the titanium substrate, preferably, the total deformation amount during cold rolling is 50-60%.

[0015] In order to further improve the (0001) texture performance of the titanium substrate, preferably, multi-pass cold rolling is adopted during cold rolling, and the deformation amount of each pass of cold rolling is 10-15%.

[0016] In order to further refine the grains, preferably, the annealing temperature is 500-550 °C, and the annealing time is 1-2 h. The grains of titanium can be refined through static recrystallization during the annealing process, and finally the obtained titanium has fine equiaxed grains with a grain size of 8-13 grades.

[0017] In order to further improve the deposition quality during electrodeposition and refine the grains of the copper foil, preferably, the electrolytic solution includes 100-120 g / L of CuSO 4 、105-120 g / L of H 2 SO 4 and 40-50 mg / L of HCl.

[0018] In order to further improve the deposition efficiency of electrodeposition, preferably, the temperature of electrodeposition is 40-60 °C, and the current density is 30-50 A / dm 2 .

[0019] In order to further obtain an extremely thin and ultrafine-grained electrolytic copper foil, preferably, the thickness of the prepared electrolytic copper foil is 4.5-6 μm, and the average grain size is 0.15-0.17 μm.

[0020] The beneficial effects of the present invention are as follows: The electrolytic copper foil prepared by the preparation method of the present invention has a strong (111) texture, and the average grain size is less than 0.2 μm. Compared with the current conventional copper foil, the grain size is reduced by more than 50%. Furthermore, an ultrafine-grained electrolytic copper foil with excellent comprehensive performance having a (111) texture is obtained. In addition, the preparation method of the present invention does not require the addition of a variety of complex additives, greatly reducing the production cost, being beneficial to environmental protection, and providing a new preparation method for electrolytic copper foils with excellent comprehensiveness. Brief Description of the Drawings

[0021] Figure 1 It is the orientation imaging diagram of the titanium substrate in Example 1 of the present invention;

[0022] Figure 2 It is the inverse pole figure of the titanium substrate in Example 1 of the present invention;

[0023] Figure 3 The grain size distribution diagram of the titanium substrate in Example 1 of the present invention;

[0024] Figure 4 The orientation imaging diagram of the electrolytic copper foil prepared in Example 1 of the present invention;

[0025] Figure 5 The grain size distribution diagram of the electrolytic copper foil prepared in Example 1 of the present invention;

[0026] Figure 6 The pole figure of the electrolytic copper foil prepared in Example 1 of the present invention;

[0027] Figure 7 The stress-strain curve diagram of the electrolytic copper foil prepared in Example 1 of the present invention;

[0028] Figure 8 The orientation imaging diagram of the electrolytic copper foil prepared in Example 2 of the present invention;

[0029] Figure 9 The grain size distribution diagram of the electrolytic copper foil prepared in Example 2 of the present invention;

[0030] Figure 10 The pole figure of the electrolytic copper foil prepared in Example 2 of the present invention;

[0031] Figure 11 The stress-strain curve diagram of the electrolytic copper foil prepared in Example 2 of the present invention;

[0032] Figure 12 The orientation imaging diagram of the electrolytic copper foil prepared in Comparative Example 1 of the present invention;

[0033] Figure 13 The grain size distribution diagram of the electrolytic copper foil prepared in Comparative Example 1 of the present invention;

[0034] Figure 14 The pole figure of the electrolytic copper foil prepared in Comparative Example 1 of the present invention;

[0035] Figure 15 The stress-strain curve diagram of the electrolytic copper foil prepared in Comparative Example 1 of the present invention. Detailed implementation manners

[0036] The technical concept of the preparation method of the electrolytic copper foil with (111) texture of the present invention is as follows:

[0037] In the prior art, the height-oriented growth of the copper foil (111) plane is effectively promoted by regulating additives, thereby realizing the production of copper foils with high tensile strength. The present invention innovatively utilizes the higher Cu adsorption active sites on the close-packed atomic planes of the substrate during electrodeposition and the matching degree of its lattice with the close-packed plane lattice of the copper foil. By regulating the preferred orientation of the grains of the substrate, the formation energy of the (111) copper crystal nuclei is reduced, thereby promoting the formation of the (111) texture of the copper foil and the refinement of grains, and realizing the strong (111) texture of the ultrafine-grained electrolytic copper foil.

[0038] It can be understood that the electrolyte used in the present invention is prepared from analytical pure copper sulfate pentahydrate, sulfuric acid and water. The mass concentration of CuSO 4 in the electrolyte is calculated based on commercially available analytical pure copper sulfate pentahydrate. Similarly, the mass concentration of H 2 SO 4 is calculated based on commercially available concentrated sulfuric acid (mass fraction 98%), and the mass concentration of HCl is calculated based on commercially available hydrochloric acid (mass fraction 37%).

[0039] The present invention will be described in detail below with reference to specific embodiments. The raw materials used in the following embodiments are all conventional commercially available products and are well-known products to those skilled in the art.

[0040] I. Specific embodiments of the method for preparing electrolytic copper foil with (111) texture according to the present invention

[0041] Example 1

[0042] The method for preparing the electrolytic copper foil with (111) texture in this example is as follows:

[0043] (1) Preparation of the titanium substrate: First, cast pure titanium is prepared by cold crucible vacuum levitation melting, and then free forging is carried out at a temperature of 950 °C to obtain forged pure titanium. The forged pure titanium is hot-rolled, the hot-rolling temperature is 450 °C, and the hot-rolling deformation is 70%; then the pure titanium is cold-rolled, the total cold-rolling deformation is 50%, and 5 passes of cold rolling are adopted, with a deformation of 10% per pass; then annealing treatment is carried out, the annealing temperature is 500 °C, and the annealing time is 1 h to obtain a pure titanium titanium plate with (0001) texture. Before electrodeposition, mechanical polishing and electrolytic polishing are carried out to remove the oxide layer to obtain a smooth surface and used as the cathode.

[0044] It can be understood that in industrial practical applications, the pure titanium with (0001) texture can be made into a cathode roller titanium cylinder. During electrodeposition, the cathode roller rotates continuously and uniformly, and copper ions are continuously electrodeposited on the cathode titanium surface. After depositing to a certain thickness, it is peeled off and wound into a roll to form an extremely thin fine-grained electrolytic copper foil; the preparation method of the cathode roller titanium cylinder can refer to the prior art. For example, the obtained pure titanium titanium plate with (0001) texture is rolled into a circle and welded to prepare the cathode roller titanium cylinder.

[0045] The electron backscatter diffraction (EBSD, Bruker QUANTAX CrystAlign 400i) was used to detect and collect information on the microstructure such as grain size, grain orientation, and local orientation difference of the pure titanium surface. The orientation imaging map, inverse pole figure, and grain size distribution map of the pure titanium with (0001) texture prepared are respectively as Figure 1 , Figure 2 and Figure 3 shown. It can be seen from Figure 1-2 that the microstructure of the pure titanium consists of fine equiaxed grains, among which there are a large number of red grains with (0001) crystal plane orientation, and there is an obvious (0001) texture in the pure titanium substrate. Using the TSL OIM Analysis software in the electron backscatter diffraction (EBSD, Bruker QUANTAX CrystAlign 400i), the intercept method was used to statistically analyze the grain size of the sample surface, and the grain size distribution map of the pure titanium surface ( Figure 3 ) was obtained, and its average value was calculated. The average grain size of the pure titanium substrate was 3.98 μm, and the grain size of this size of grains reached grade 13; in other embodiments, the grain size (calculated by the average grain size) of the prepared titanium substrate was in the range of grades 8-13.

[0046] (2) Electrodeposition: Copper sulfate pentahydrate, sulfuric acid, and hydrochloric acid were added to deionized water to prepare an electrolyte. The mass concentration of CuSO 4 in the electrolyte was 100 g / L, the mass concentration of H 2 SO 4 was 105 g / L, and the mass concentration of HCl was 40 mg / L; the electrolyte was added to the electrolytic cell, and the pure titanium with (0001) texture prepared in step (1) was used as the cathode, and iridium-plated titanium was used as the anode. Direct current electrodeposition was carried out under stirring conditions. The temperature of the electrodeposition was 60 °C, and the current density was 30 A / dm 2 , and an electrolytic copper foil with a thickness of 6 μm was obtained.

[0047] The electron backscatter diffraction instrument was used to detect and collect information on the microstructure such as grain size, grain orientation, and local orientation difference of the copper foil surface. The electrolytic copper foil has a strong (111) texture and fine equiaxed grains. The orientation imaging map, grain size distribution map, and inverse pole figure of the obtained electrolytic copper foil are respectively as Figure 4 , 5 and 6 shown. It can be found from Figure 4 that the microstructure of the copper foil consists of fine equiaxed grains, among which there are a large number of blue grains with (111) crystal plane orientation. From Figure 5 the grain size distribution map of the copper foil, it can be statistically obtained that the average grain size of the copper foil is 0.15 μm. From Figure 6From the inverse pole figure, it can be found that the copper foil has an obvious (111) texture. The mechanical properties of the copper foil were tested, and the stress-strain curve obtained from the test is as Figure 7 shown. From Figure 7 it can be seen that the tensile strength of the copper foil is 426.5 MPa, and the elongation obtained from the test is 5.1%.

[0048] Example 2

[0049] The preparation method of the electrolytic copper foil with (111) texture in this example is basically the same as that in Example 1, except that the electrodeposition process parameters are changed. Specifically: (2) Electrodeposition: Copper sulfate pentahydrate, sulfuric acid and hydrochloric acid were added to deionized water to prepare an electrolyte. The mass concentration of CuSO 4 in the electrolyte is 120 g / L, the mass concentration of H 2 SO 4 is 120 g / L, and the mass concentration of HCl is 50 mg / L; the electrolyte was added to the electrolytic cell, and the pure titanium with (0001) texture prepared in step (1) was used as the cathode, and iridium-coated titanium was used as the anode. Direct current electrodeposition was carried out under stirring conditions. The temperature of the electrodeposition was 40 °C, and the current density was 50 A / dm 2 , and an electrolytic copper foil with a thickness of 4.5 μm was obtained.

[0050] The electrolytic copper foil has fine equiaxed grains and a strong (111) texture. The orientation imaging map, grain size distribution map and inverse pole figure of the obtained electrolytic copper foil are respectively as Figure 8 , 9 and 10 shown. From Figure 8 it can be found that the microstructure of the copper foil is composed of fine equiaxed grains, and there are a large number of grains with blue (111) crystal planes. From Figure 9 the grain size distribution map of the copper foil, it can be statistically obtained that the average grain size of the copper foil is 0.17 μm. From Figure 10 the inverse pole figure, it can be found that the copper foil has an obvious (111) texture. The stress-strain curve obtained from the test is as Figure 11 shown. The tensile strength of the copper foil is 434.1 MPa, and the elongation obtained from the test is 4.6%.

[0051] II. Comparative Example

[0052] Comparative Example 1

[0053] The preparation method of the electrolytic copper foil with (111) texture in this comparative example is basically the same as that in Example 1, except that the crystal plane texture of the titanium substrate is changed. Specifically: (2) Using pure titanium with crystal plane texture as the cathode and iridium-coated titanium as the anode, direct current electrodeposition was carried out under stirring conditions to obtain an electrolytic copper foil with a thickness of 0.6 μm.

[0054] The obtained orientation imaging map, grain size distribution map, and inverse pole figure of the electrolytic copper foil are shown in Figure 12 , 13 and Figure 14 respectively. It can be found from Figure 12 that this copper foil is composed of relatively large blocky and flaky grains, and the microstructure is uneven. From Figure 13 the grain size distribution map of the copper foil, it can be statistically obtained that the average grain size of this copper foil is 0.52 μm, which is more than three times that of the electrolytic copper foil in Example 1. From Figure 14 the inverse pole figure, it can be found that the texture of the copper foil is not a significantly single (111) texture, but there are two textures of (111) and (110). The measured stress-strain curve is shown in Figure 15 . The tensile strength of the copper foil is 286.9 MPa, and the measured elongation is 3.5%.

[0055] The specific tissue characteristic parameters and performance indexes of the electrolytic copper foils prepared in each example and comparative example are shown in Table 1.

[0056] Table 1 Specific tissue characteristic parameters and mechanical properties of electrolytic copper foil

[0057] Serial number Grain size / μm (111) texture strength Tensile strength / MPa Elongation Example 1 0.15 1.675 426.5 5.1% Example 2 0.17 1.520 434.1 4.6% Comparative example 1 0.52 1.112 286.9 3.5%

[0058] The above is only the preferred specific implementation manner of the present invention; however, the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its improved concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A method for preparing an electrolytic copper foil having a (111) texture, characterized in that: The following steps are involved: A titanium substrate with a (0001) texture is used as a cathode, and direct current electrodeposition is performed in an electrolyte to obtain a fine-grained electrolytic copper foil with a (111) texture, wherein the average grain size of the electrolytic copper foil is less than 0.2 μm; The preparation method of the titanium substrate comprises the following steps: hot rolling the forged pure titanium at 400-450°C, and then cold rolling and annealing; the annealing temperature is 500-550°C, and the annealing time is 1-2 hours; the direct current deposition temperature is 40-60°C, and the current density is 30-50A / dm 2 .

2. The method for preparing an electrolytic copper foil having a (111) texture according to claim 1, characterized in that: The deformation during hot rolling is 60-70%.

3. The method for preparing an electrolytic copper foil having a (111) texture according to claim 1, characterized in that: The total deformation during the cold rolling is 50-60%.

4. The method for preparing an electrolytic copper foil having a (111) texture according to claim 1 or 3, characterized in that: Multiple cold rolling passes are used during cold rolling, and the deformation of each cold rolling pass is 10~15%.

5. The method for preparing an electrolytic copper foil having a (111) texture according to claim 1, characterized in that: The electrolyte includes 100-120 g / L of CuSO4, 105-120 g / L of H2SO4 and 40-50 mg / L of HCl.

6. The method for preparing an electrolytic copper foil having a (111) texture according to claim 1, characterized in that: The thickness of the prepared electrolytic copper foil is 4.5~6 μm, and the average grain size is 0.15~0.17 μm.

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