A method for preparing a mixed crystal electrolytic copper foil

Abstract

The application relates to a preparation method of mixed-crystal electrolytic copper foil, and sodium nitrilotriacetic acid and 4-sec-butyl phenol are added as composite additives in an electrolytic green foil process. In the electrolytic green foil process, a new type of composite additive formula is introduced to regulate the copper atom electrodeposition process, so that the electrolytic copper foil with a mixed-crystal organizational structure composed of coarse blocky crystals and fine equiaxed crystals is obtained.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic copper foil technology, and specifically relates to a method for preparing mixed crystal electrolytic copper foil. Background Technology

[0002] With the trend towards thinner lithium-ion battery copper foil, copper foil is becoming increasingly thinner, with the mainstream thickness being 4-6 μm. Copper foil with ordinary tensile strength is prone to breakage due to insufficient tensile strength, causing a surge in scrap rates throughout the coating, rolling, and slitting processes. High tensile strength can withstand high-speed tension, reducing wrinkles, tears, and microcracks, inhibiting crack propagation, resulting in better electrode consistency and higher production efficiency and yield. However, increasing the tensile strength of copper foil usually leads to a decrease in elongation, thereby increasing the risk of breakage.

[0003] The tensile strength and elongation of electrolytic copper foil are generally inversely proportional; higher tensile strength corresponds to lower elongation, and vice versa. In the electrolytic copper foil industry, additive technology is typically used to improve the tensile strength of copper foil. High tensile strength is achieved by adding additives to the raw foil electrolyte to refine the copper foil grains. However, smaller grains lead to a decrease in elongation. Therefore, high tensile strength and high elongation are the main issues restricting the development of thinner lithium-ion battery copper foil, and the problem of insufficient elongation at high tensile strength urgently needs to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing mixed crystal electrolytic copper foil. The method introduces a novel composite additive formula to regulate the copper atom electrodeposition process in the electrolytic foil production process, so as to obtain an electrolytic copper foil with a mixed crystal structure composed of coarse bulk crystals and fine equiaxed crystals.

[0005] This invention provides a method for preparing mixed-crystal electrolytic copper foil, wherein sodium nitrilotriacetate and 4-sec-butylphenol are added as composite additives in the electrolytic foil production process.

[0006] Preferably, the concentration of sodium nitrilotriacetate and the concentration of 4-sec-butylphenol in the raw foil electrolyte are 5-10 mg / L.

[0007] Preferably, the chloride ion concentration in the raw foil electrolyte is 10-50 mg / L, and the temperature of the raw foil electrolyte is 50-60°C. o C.

[0008] Preferably, in the electrolytic foil production process, the copper ion concentration in the copper sulfate electrolyte is 50~100 g / L, and the acid content is 100~50 g / L.

[0009] Preferably, the current density in the electrolytic foil-making process is 50~100 A / dm³. 2 .

[0010] This invention utilizes the influence of different components in a composite additive on copper atom electrodeposition. Sodium nitrilotriacetate promotes copper atom deposition and coarsens copper grains, while 4-sec-butylphenol inhibits copper atom deposition and refines copper grains. Therefore, a crystal structure exhibiting both coarse bulk crystals and fine equiaxed crystals can be obtained. This mixed-crystal electrolytic copper foil possesses excellent mechanical properties, exhibiting both high tensile strength and high elongation, thus solving the problem of low elongation caused by high tensile strength in electrolytic copper foil.

[0011] Beneficial effects This invention introduces a novel composite additive formulation to regulate the copper atom electrodeposition process in the electrolytic foil production process, thereby obtaining an electrolytic copper foil with a mixed crystal structure composed of coarse bulk crystals and fine equiaxed crystals. The mixed crystal electrolytic copper foil has a room temperature tensile strength of over 600 MPa and an elongation of over 8%, thus solving the risk of foil breakage due to insufficient elongation in the lithium battery anode coating process. Attached Figure Description

[0012] Figure 1 The EBSD crystal structure of the rough surface of the copper foil prepared for Comparative Example 1.

[0013] Figure 2 The EBSD crystal structure of the rough surface of the copper foil prepared for Comparative Example 2.

[0014] Figure 3 The EBSD crystal structure of the rough surface of the copper foil prepared in Example 1. Detailed Implementation

[0015] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0016] Comparative Example 1 1) Elemental copper is added to a copper dissolving tank containing sulfuric acid to dissolve it into copper sulfate electrolyte. After being purified by multi-stage filtration, the electrolyte is sent to an electrolytic foil production machine. The copper ion concentration in the copper sulfate electrolyte is 90 g / L, and the acid content is 110 g / L. 2) Collagen and hydrochloric acid are introduced into the above copper sulfate electrolyte to obtain a raw foil electrolyte; the concentration of sodium nitrilotriacetate in the raw foil electrolyte is 10 mg / L, the concentration of chloride ions is 30 mg / L, and the temperature of the raw foil electrolyte is 54°C. o C; 3) The above-mentioned foil electrolyte is continuously electroplated on the cathode roller using a foil-forming machine to produce foil. The electrolytic cathode of the foil-forming machine is a seamless roller-type titanium roller, and the electrolytic anode is a DSA-coated titanium anode plate. The current density is 90 A / dm³. 2 .

[0017] Under the above process conditions, the physical properties of the 4 μm lithium-ion battery copper foil are as follows: like Figure 1 As shown, the EBSD crystal structure of the rough copper foil is a coarse, massive crystalline structure with a grain size of 5–10 μm. The tensile strength at room temperature is 365 MPa, and the elongation at room temperature is 8.2%.

[0018] Comparative Example 2 1) Elemental copper is added to a copper dissolving tank containing sulfuric acid to dissolve it into copper sulfate electrolyte. After being purified by multi-stage filtration, the electrolyte is sent to an electrolytic foil production machine. The copper ion concentration in the copper sulfate electrolyte is 90 g / L, and the acid content is 110 g / L. 2) Collagen and hydrochloric acid are introduced into the copper sulfate electrolyte to obtain a raw foil electrolyte; the concentration of 4-sec-butylphenol in the raw foil electrolyte is 10 mg / L, the concentration of chloride ions is 30 mg / L, and the temperature of the raw foil electrolyte is 54°C. o C; 3) The above-mentioned foil electrolyte is continuously electroplated on the cathode roller using a foil-forming machine to produce foil. The electrolytic cathode of the foil-forming machine is a seamless roller-type titanium roller, and the electrolytic anode is a DSA-coated titanium anode plate. The current density is 90 A / dm³. 2 .

[0019] Under the above process conditions, the physical properties of the 4 μm lithium-ion battery copper foil are as follows: like Figure 2 As shown, the EBSD crystal structure of the rough copper foil is a fine equiaxed crystal structure with a grain size of 0.2~1.0μm. The tensile strength at room temperature is 657 MPa, and the elongation at room temperature is only 2.2%.

[0020] Example 1 1) Elemental copper is added to a copper dissolving tank containing sulfuric acid to dissolve it into copper sulfate electrolyte. After being purified by multi-stage filtration, the electrolyte is sent to an electrolytic foil production machine. The copper ion concentration in the copper sulfate electrolyte is 90 g / L, and the acid content is 110 g / L. 2) Collagen and hydrochloric acid are introduced into the above copper sulfate electrolyte to obtain a raw foil electrolyte; the concentration of sodium nitrilotriacetate in the raw foil electrolyte is 10 mg / L, the concentration of 4-sec-butylphenol is 10 mg / L, the concentration of chloride ions is 30 mg / L, and the temperature of the raw foil electrolyte is 54°C. o C; 3) The above-mentioned foil electrolyte is continuously electroplated on the cathode roller using a foil-forming machine to produce foil. The electrolytic cathode of the foil-forming machine is a seamless roller-type titanium roller, and the electrolytic anode is a DSA-coated titanium anode plate. The current density is 90 A / dm³. 2 .

[0021] Under the above process conditions, the physical properties of the 4 μm lithium-ion battery copper foil are as follows: like Figure 3 As shown, the EBSD crystal structure of the rough copper foil is a mixed crystal structure composed of coarse bulk crystals and fine equiaxed crystals, wherein the size of the coarse bulk crystals is 4~8 μm and the size of the fine equiaxed crystals is 0.3~0.7 μm. The tensile strength at room temperature is 639 MPa and the elongation at room temperature is 8.6%.

[0022] Example 2 1) Elemental copper is added to a copper dissolving tank containing sulfuric acid to dissolve it into copper sulfate electrolyte. After being purified by multi-stage filtration, the electrolyte is sent to an electrolytic foil production machine. The copper ion concentration in the copper sulfate electrolyte is 90 g / L, and the acid content is 110 g / L. 2) Collagen and hydrochloric acid are introduced into the copper sulfate electrolyte to obtain a raw foil electrolyte; the concentration of sodium nitrilotriacetate in the raw foil electrolyte is 10 mg / L, the concentration of 4-sec-butylphenol is 5 mg / L, the concentration of chloride ions is 30 mg / L, and the temperature of the raw foil electrolyte is 54°C. o C; 3) The above-mentioned foil electrolyte is continuously electroplated on the cathode roller using a foil-forming machine to produce foil. The electrolytic cathode of the foil-forming machine is a seamless roller-type titanium roller, and the electrolytic anode is a DSA-coated titanium anode plate. The current density is 90 A / dm³. 2 .

[0023] Under the above process conditions, the physical properties of the 4 μm lithium-ion battery copper foil are as follows: The EBSD crystal structure of the rough copper foil is a mixed crystal structure composed of coarse bulk crystals and fine equiaxed crystals, with the coarse bulk crystals ranging from 6 to 10 μm in size and the fine equiaxed crystals ranging from 0.5 to 1.0 μm in size. The tensile strength at room temperature is 618 MPa, and the elongation at room temperature is 9.1%.

[0024] Example 3 1) Elemental copper is added to a copper dissolving tank containing sulfuric acid to dissolve it into copper sulfate electrolyte. After being purified by multi-stage filtration, the electrolyte is sent to an electrolytic foil production machine. The copper ion concentration in the copper sulfate electrolyte is 90 g / L, and the acid content is 110 g / L. 2) Collagen and hydrochloric acid are introduced into the above copper sulfate electrolyte to obtain a raw foil electrolyte; the concentration of sodium nitrilotriacetate in the raw foil electrolyte is 5 mg / L, the concentration of 4-sec-butylphenol is 10 mg / L, the concentration of chloride ions is 30 mg / L, and the temperature of the raw foil electrolyte is 54°C.o C; 3) The above-mentioned foil electrolyte is continuously electroplated on the cathode roller using a foil-forming machine to produce foil. The electrolytic cathode of the foil-forming machine is a seamless roller-type titanium roller, and the electrolytic anode is a DSA-coated titanium anode plate. The current density is 90 A / dm³. 2 .

[0025] Under the above process conditions, the physical properties of the 4 μm lithium-ion battery copper foil are as follows: The EBSD crystal structure of the rough copper foil is a mixed crystal structure composed of coarse bulk crystals and fine equiaxed crystals, with the coarse bulk crystals having a size of 4~6 μm and the fine equiaxed crystals having a size of 0.2~0.5 μm. The tensile strength at room temperature is 649 MPa, and the elongation at room temperature is 8.2%.

Claims

1. A method for preparing mixed-crystal electrolytic copper foil, characterized in that, Sodium nitrilotriacetate and 4-sec-butylphenol are added as composite additives in the electrolytic foil production process.

2. The preparation method according to claim 1, characterized in that, The concentration of sodium nitrilotriacetate and the concentration of 4-sec-butylphenol in the raw foil electrolyte are 5~10 mg / L.

3. The preparation method according to claim 1, characterized in that, The chloride ion concentration in the raw foil electrolyte is 10~50 mg / L, and the temperature of the raw foil electrolyte is 50~60°C. o C.

4. The preparation method according to claim 1, characterized in that, In the electrolytic foil production process, the copper ion concentration in the copper sulfate electrolyte is 50~100 g / L, and the acid content is 100~50 g / L.

5. The preparation method according to claim 1, characterized in that, The current density in the electrolytic foil production process is 50~100 A / dm. 2 .

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