Preparation method of extra-high-strength electrolytic copper foil

Abstract

The invention discloses a preparation method of an extra-high-strength electrolytic copper foil. Belongs to the technical field of electrolytic copper foils. The method is characterized by comprising the following steps: (1) dissolving copper to obtain a copper sulfate solution for later use; (2) mixing: filtering the copper sulfate solution, and mixing the filtered copper sulfate solution with an additive solution containing rare metal elements to obtain a mixed electrolyte capable of being subjected to electro-deposition for later use; the rare metal elements have the characteristics of relatively low electronegativity and relatively large ion radius; (3) foil generation; (4) surface treatment; and (5) slitting and rolling to obtain the ultra-high-strength lithium battery copper foil. The invention aims to provide the preparation method of the extra-high-strength electrolytic copper foil which is scientific in process and novel in formula; the method is used for preparing electrolytic copper foil.

Description

Technical Field

[0001] The present invention relates to a method for preparing an electrolytic copper foil, and more specifically, to a method for preparing an ultra-high strength electrolytic copper foil. Background Art

[0002] In the continuous evolution of lithium-ion battery technology, a breakthrough material innovation - ultra-high strength copper foil has emerged to address the application challenges of silicon-based negative electrode materials. This type of copper foil has unprecedented mechanical properties, and its tensile strength is as high as 900 megapascals (MPa), far exceeding the strength level of traditional copper foil. At the same time, the purity of the copper foil has also reached a high standard of 99.8%, which means that the impurity content inside it is extremely low, which effectively reduces the electrochemical side reactions inside the battery and improves the overall performance of the battery. High purity not only ensures good conductivity, but also helps to extend the service life of the battery. It is an indispensable key element for high-performance lithium-ion batteries.

[0003] With the rapid development of the electronics industry, the performance requirements for copper foil are getting higher and higher, especially the tensile strength. The traditional copper foil preparation method is often difficult to meet the demand for ultra-high strength copper foil (tensile strength exceeding 900 MPa) with a purity of more than 99.8%. Therefore, it is urgent to develop a method for preparing electrolytic copper foil with ultra-high strength and purity of more than 99.8%. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing an ultra-high strength electrolytic copper foil with scientific process and novel formula to overcome the above-mentioned deficiencies in the prior art. The method not only meets the requirements of mechanical properties, but also has a purity of more than 99.8%.

[0005] The technical solution of the present invention is implemented as follows: a method for preparing ultra-high strength electrolytic copper foil, comprising the following steps: (1) dissolving copper to obtain a copper sulfate solution for standby use; (2) mixing, filtering the copper sulfate solution and mixing it with an additive solution containing a rare metal element to obtain a mixed electrolyte that can be electrodeposited for standby use; the rare metal element has the characteristics of low electronegativity and large ion radius; (3) raw foil; (4) surface treatment; (5) slitting and winding to obtain an ultra-high strength lithium battery copper foil.

[0006] In the above-mentioned method for preparing an ultra-high strength electrolytic copper foil, in step (2), the copper ion concentration in the mixed electrolyte is 50-120 g / l, the acid concentration is 50-140 g / l, and the chloride ion content is 15-45 mg / l.

[0007] In the above-mentioned method for preparing ultra-high strength electrolytic copper foil, the current during foil production in step (3) is 20000-45000A, the voltage is 4.0-5.5V, and the cathode roller speed is 4.8-10.5m / min.

[0008] In the above-mentioned method for preparing ultra-high strength electrolytic copper foil, the additives include dilute hydrochloric acid, agent A, agent B, agent C, and agent D, agent A is a small molecule sulfur-containing organic matter, agent B is a sulfur- or nitrogen-containing organic matter, agent C is a high molecular weight oxygen-containing compound, and agent D is a rare metal compound.

[0009] In the above-mentioned method for preparing ultra-high strength electrolytic copper foil, the content of agent A in the mixed electrolyte is 10-180 mg / l; the agent A is one or any combination of two or more of sodium polydisulfide propane sulfonate, sodium 3-mercaptopropane sulfonate, and tetrahydrothiazolidine-2-thione.

[0010] In the above-mentioned method for preparing an ultra-high strength electrolytic copper foil, the content of agent B in the mixed electrolyte is 0.01-15 mg / l; the agent B is one or any combination of two or more of n-diethyl trithioamino performate, sodium formamide propane sulfonate, polyethylene imine alkyl salt, and pyridinium propane sulfonate.

[0011] In the above-mentioned method for preparing ultra-high strength electrolytic copper foil, the content of agent C in the mixed electrolyte is 0.01-25 mg / l; the agent C is one or any combination of two or more of polyethylene glycol, hydroxyethyl cellulose, and allyl polyoxyethylene ether.

[0012] In the above-mentioned method for preparing an ultra-high strength electrolytic copper foil, the content of agent D in the mixed electrolyte is 0.01-5 mg / l; the agent D is a mixture of propoxylated propynyl alcohol and tin molybdate compounds; in the mixture, the mass ratio of propoxylated propynyl alcohol to tin molybdate compounds is 1:2-4.

[0013] In the above-mentioned method for preparing an ultra-high strength electrolytic copper foil, in the tin molybdate compound, the mass ratio of the rare metal molybdenum to tin is 1:2.5-4.

[0014] After adopting the above scheme, the present invention achieves a great improvement in the performance of copper foil by adding rare metals with low electronegativity and large ion radius to the additive. Low electronegativity makes it easier to form a complex with copper ions, adsorb on the metal surface, inhibit pitting corrosion, and thus change the deposition potential of copper. Large ion radius can change the reduction potential of copper ions through replacement reaction with copper ions, affect the deposition process of copper, thereby affecting the microstructure and morphology of the coating, and then accelerate the deposition rate of ultra-high strength copper foil, and it will change the surface energy of the cathode during the reaction mechanism, and improve the strength and purity of the copper foil.

[0015] The present invention adopts an original additive process containing rare metals to refine the crystals to nanocrystalline particles, while affecting the grain growth and crystal density during the crystallization process, and can prepare copper foil with high purity and ultra-high tensile strength.

[0016] The electrolytic copper foil prepared by the process of the present invention has a purity greater than 99.8%, a tensile strength greater than 900 MPa, an elongation greater than 3.5%, a glossiness of the smooth and rough surfaces higher than 400 gs, a roughness ra of the smooth and rough surfaces less than 0.3 μm, and a roughness rz of less than 2 μm, and has stable and controllable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is an electron microscope image of the rough surface of ordinary electrolytic copper foil magnified 1000 times;

[0018] Figure 2 This is an electron microscope image of the rough surface of ordinary electrolytic copper foil magnified 2000 times;

[0019] Figure 3 This is an electron microscope image of the rough surface of high-tensile electrolytic copper foil magnified 1000 times;

[0020] Figure 4 This is an electron microscope image of the rough surface of high-tensile electrolytic copper foil magnified 2000 times;

[0021] Figure 5 This is an electron microscope image of the rough surface of the ultra-high strength electrolytic copper foil of the present invention magnified 1000 times;

[0022] Figure 6 This is an electron microscope image of the rough surface of the ultra-high strength electrolytic copper foil of the present invention magnified 2000 times;

[0023] Figure 7 It is a tensile force stroke breakpoint curve diagram of the ultra-high strength electrolytic copper foil of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with the embodiments, but they do not constitute any limitation to the present invention.

[0025] The method for preparing an ultra-high strength electrolytic copper foil of the present invention comprises the following steps: (1) dissolving copper to obtain a copper sulfate solution for standby use; this step is a conventional process in the art and will not be described in detail herein.

[0026] (2) mixing, filtering the copper sulfate solution and mixing it with an additive solution containing a rare metal element to obtain a mixed electrolyte that can be electrodeposited, which is then used for standby; the rare metal element has the characteristics of low electronegativity and large ion radius;

[0027] Further preferably, the copper ion concentration in the mixed electrolyte is 50-120 g / l, the acid concentration is 50-140 g / l, and the chloride ion content is 15-45 mg / l.

[0028] In this embodiment, the additives include dilute hydrochloric acid, agent A, agent B, agent C, and agent D. Agent A is a small molecule sulfur-containing organic matter, agent B is a sulfur- or nitrogen-containing organic matter, agent C is a high molecular weight oxygen-containing compound, and agent D is a rare metal compound.

[0029] Preferably, the content of agent A in the mixed electrolyte is 10-180 mg / l; the agent A is one or any combination of two or more of sodium polydisulfide propane sulfonate, sodium 3-mercaptopropane sulfonate, and tetrahydrothiazolidine-2-thione.

[0030] Preferably, the content of agent B in the mixed electrolyte is 0.01-15 mg / l; the agent B is one or any combination of two or more of n-diethyl trithioaminoperformate, sodium formamide propane sulfonate, polyethyleneimine alkyl salt, and pyridinium propane sulfonate.

[0031] Preferably, the content of agent C in the mixed electrolyte is 0.01-25 mg / l; the agent C is one or any combination of two or more of polyethylene glycol, hydroxyethyl cellulose, and allyl polyoxyethylene ether.

[0032] Preferably, the content of agent D in the mixed electrolyte is 0.01-5 mg / l; the agent D is a mixture of propoxylated propargyl alcohol and tin molybdate compound; in the mixture, the mass ratio of propoxylated propargyl alcohol to tin molybdate compound is 1:2-4.

[0033] Tin molybdate (SnMoO 4 ) is the key technology for controlling the performance of copper foil. By introducing rare metals molybdenum and tin into the electrolyte, the reaction potential of copper deposition can be changed. Molybdenum has a low electronegativity and is more likely to form a complex with copper ions, adsorb on the metal surface, inhibit pitting corrosion, and thus change the deposition potential of copper. At the same time, tin has a large ion radius and changes the reduction potential of copper ions through a replacement reaction with copper ions, thereby affecting the deposition process of copper.

[0034] Further preferably, in the tin molybdate compound, the mass ratio of rare metal molybdenum to tin is 1:2.5-4. The molybdenum content is small because a large content will combine with copper ions to form a copper-molybdenum alloy, so a small amount is required, and the tin content is large because copper ions cannot combine with copper ions during the electrodeposition process to form a copper-tin alloy, and can only affect the growth of copper ions and finally be absorbed by filtering materials such as diatomaceous earth and activated carbon.

[0035] (3) Foil production: The current during foil production is 20000-45000A, the voltage is 4.0-7.5V, and the cathode roller speed is 4.8-10.5m / min. The effect of rare metal additives on the reduction potential of copper ions will also be reflected in the voltage. In this embodiment, the addition of tin molybdate compounds reduces the reduction potential of copper ions. In order to maintain the same deposition rate, the voltage needs to be increased to provide sufficient driving force to ensure that the deposition process is more efficient.

[0036] (4) Surface treatment: This step is a conventional process in the art and will not be described in detail here.

[0037] (5) Slitting and reeling to obtain ultra-high-strength lithium battery copper foil.

[0038] Example 1

[0039] The raw copper is placed in a copper dissolving tank, and a copper sulfate solution is prepared according to a conventional process. The copper sulfate solution is filtered at multiple stages and then mixed with an additive solution to obtain a mixed electrolyte. The copper ion concentration, acid concentration, and chloride ion content of the mixed electrolyte are 50 g / l, 50 g / l, and 15 mg / l, respectively. The content of sodium polydisulfide propane sulfonate is 10 mg / l, the content of n-diethyl trithioaminoperformate is 0.01 mg / l, the content of polyethylene glycol is 0.01 mg / l, and the content of a mixture of propoxylated propargyl alcohol and tin molybdate compound is 0.01 mg / l; wherein the mass ratio of propoxylated propargyl alcohol to tin molybdate compound is 1:2.

[0040] After the mixed electrolyte is heated to a predetermined temperature, it is introduced into the electrolytic cell of the foil machine through conventional pipeline equipment for electrolytic foil production. The current during foil production is 20000A, the voltage is 4.0V, and the cathode roller speed is 4.8m / min. The copper foil peeled from the foil machine is sequentially surface treated and slit and rolled to obtain 4.0μm ultra-high strength lithium copper foil.

[0041] Example 2

[0042] The raw copper is placed in a copper dissolving tank, and a copper sulfate solution is prepared according to a conventional process. The copper sulfate solution is filtered at multiple stages and then mixed with an additive solution to obtain a mixed electrolyte. The copper ion concentration in the mixed electrolyte is 70g / l, the acid concentration is 70g / l, and the chloride ion content is 20mg / l. The content of sodium 3-mercaptopropane sulfonate is 50mg / l, and the total content of sodium formamide propane sulfonate and polyethylene imine alkyl salt is 3mg / l. The mass ratio of sodium formamide propane sulfonate and polyethylene imine alkyl salt is 1:1; the content of hydroxyethyl cellulose is 5mg / l; the content of the mixture of propoxylated propargyl alcohol and tin molybdate compound is 0.8mg / l; and the mass ratio of propoxylated propargyl alcohol and tin molybdate compound is 1:2.

[0043] After the mixed electrolyte is heated to a predetermined temperature, it is introduced into the electrolytic cell of the foil machine through conventional pipeline equipment for electrolytic foil production. The current during foil production is 25000A, the voltage is 4.5V, and the cathode roller speed is 6m / min. The copper foil peeled from the foil machine is sequentially surface treated and slit and rolled to obtain 5μm ultra-high strength lithium copper foil.

[0044] Example 3

[0045] The raw copper is placed in a copper dissolving tank, and a copper sulfate solution is prepared according to a conventional process. The copper sulfate solution is filtered at multiple stages and mixed with an additive solution to obtain a mixed electrolyte. The copper ion concentration, acid concentration and chloride ion content of the mixed electrolyte are 90 g / l, 90 g / l and 25 mg / l, respectively.

[0046] The content of tetrahydrothiazolidine-2-thione is 95 mg / l; the content of polyethyleneimine alkyl salt is 6 mg / l; the content of allyl polyoxyethylene ether is 10 mg / l; the content of the mixture of propoxylated propynyl alcohol and tin molybdate compound is 1.8 mg / l; wherein the mass ratio of propoxylated propynyl alcohol to tin molybdate compound is 1:2.5.

[0047] After the mixed electrolyte is heated to a predetermined temperature, it is introduced into the electrolytic cell of the foil machine through conventional pipeline equipment for electrolytic foil production. The current during foil production is 29000A, the voltage is 5V, and the cathode roller speed is 7.5m / min. The copper foil peeled from the foil machine is subjected to surface treatment and slitting and winding in sequence to obtain 6μm ultra-high strength lithium copper foil.

[0048] Example 4

[0049] The raw copper is placed in a copper dissolving tank, and a copper sulfate solution is prepared according to a conventional process. The copper sulfate solution is filtered at multiple stages and mixed with an additive solution to obtain a mixed electrolyte. The copper ion concentration, acid concentration and chloride ion content of the mixed electrolyte are 110 g / l, 110 g / l and 35 mg / l, respectively.

[0050] The content of the mixture of sodium 3-mercaptopropane sulfonate and tetrahydrothiazolidine-2-thione is 150 mg / l, wherein the mass ratio of sodium 3-mercaptopropane sulfonate to tetrahydrothiazolidine-2-thione is 1:1; the content of pyridinium propane sulfonate is 12 mg / l; the content of allyl polyoxyethylene ether is 20 mg / l; the content of the mixture of propoxylated propynyl alcohol and tin molybdate compound is 3 mg / l; wherein the mass ratio of propoxylated propynyl alcohol to tin molybdate compound is 1:3.

[0051] After the mixed electrolyte is heated to a predetermined temperature, it is introduced into the electrolytic cell of the foil machine through conventional pipeline equipment for electrolytic foil production. The current during foil production is 32000A, the voltage is 6V, and the cathode roller speed is 9m / min. The copper foil peeled from the foil machine is subjected to surface treatment and slitting and winding in sequence to obtain 8μm ultra-high strength lithium copper foil.

[0052] Example 5

[0053] The raw copper is put into a copper dissolving tank, and a copper sulfate solution is prepared according to a conventional process. The copper sulfate solution is filtered at multiple stages and then mixed with an additive solution to obtain a mixed electrolyte. The copper ion concentration in the mixed electrolyte is 120g / l, the acid concentration is 140g / l, and the chloride ion content is 45mg / l. The content of sodium 3-mercaptopropane sulfonate is 180mg / l; the content of pyridine propane sulfonate is 15mg / l; the content of allyl polyoxyethylene ether is 25mg / l; the content of a mixture of propoxylated propargyl alcohol and tin molybdate compound is 5mg / l; wherein the mass ratio of propoxylated propargyl alcohol to tin molybdate compound is 1:4.

[0054] After the mixed electrolyte is heated to a predetermined temperature, it is introduced into the electrolytic cell of the foil machine through conventional pipeline equipment for electrolytic foil production. The current during foil production is 45000A, the voltage is 7.5V, and the cathode roller speed is 10.5m / min. The copper foil peeled from the foil machine is sequentially surface treated and slit and rolled to obtain 10μm ultra-high strength lithium copper foil.

[0055] Experimental example

[0056] From the copper foil produced in the above five embodiments, four small sections of copper foil strips with a specification of 1.5*15 cm were cut respectively, and their thickness, matte glossiness, tensile strength (MPa), elongation (%), and copper foil purity (%) were tested by a thickness tester, a glossiness tester, an electronic tensile testing machine, and an electrolytic-spectrophotometer. The specific results are as follows:

[0057] Table 1 Test results

[0058] Physical properties Example 1 Example 2 Example 3 Example 4 Example 5 Thickness(μm) 4μm 5μm 6μm 8μm 10μm Matte glossiness 595 506 490 430 445 Tensile strength(MPa) 902.6 933.2 926.4 942.8 983.8 Elongation(%) 4.2 4.7 4.6 5.3 3.7 Copper foil purity (%) 99.816 99.835 99.846 99.841 99.838

[0059] As shown in Table 1, the high-purity and ultra-high-strength electrolytic copper foil prepared by the rare metal additive process formula of the present invention has excellent physical properties, a tensile strength of more than 900 MPa, an elongation of more than 4%, and a copper foil purity of more than 99.8%.

[0060] At the same time, in order to more intuitively present the difference between the electrolytic copper foil prepared by the present invention and the existing electrolytic copper foil, the copper foil prepared in Example 3, the ordinary electrolytic copper foil obtained by the conventional process, and the high tensile strength electrolytic copper foil were randomly selected, and the rough surface of the copper foil was scanned by a scanning electron microscope (SEM) at 1000 times and 2000 times magnification, respectively, to obtain Figures 1 to 6 Electron micrograph shown.

[0061] As can be seen from the figure, the electrolytic copper foil obtained by the present invention has finer particles and excellent density and flatness, and is significantly different from ordinary copper foil and high tensile copper foil.

[0062] The electrolytic copper foil obtained in Example 2 was randomly selected and tested for tensile strength and elongation using an electronic tensile testing machine. The breakpoint curve is shown in the figure below. Figure 7 The corresponding maximum tensile force data are shown in Table 2.

[0063] Table 2 Maximum tensile force data

[0064]

[0065] Combined with Table 2 Figure 7 It can be seen that the electrolytic copper foil obtained by the process of the present invention has excellent tensile strength and elongation properties and an extremely high travel breaking point.

[0066] The above embodiments are preferred implementation modes of the present invention and are only used to facilitate the description of the present invention. They are not intended to limit the present invention in any form. Any person with ordinary knowledge in the relevant technical field, if they do not depart from the scope of the technical features of the present invention, can make equivalent embodiments by partial changes or modifications to the technical contents disclosed in the present invention, and they still fall within the scope of the technical features of the present invention without departing from the technical features of the present invention.

Claims

1. A method for preparing ultra-high strength electrolytic copper foil, characterized in that: The method comprises the following steps: (1) dissolving copper to obtain a copper sulfate solution for standby use; (2) mixing, filtering the copper sulfate solution and mixing it with an additive solution containing a rare metal element to obtain a mixed electrolyte that can be electrodeposited, which is then used for later use; the rare metal element has the characteristics of low electronegativity and large ion radius; (3) raw foil; (4) surface treatment; (5) slitting and winding to obtain ultra-high strength lithium battery copper foil.

2. The method for preparing an ultra-high strength electrolytic copper foil according to claim 1, characterized in that: In step (2), the copper ion concentration in the mixed electrolyte is 50-120 g / l, the acid concentration is 50-140 g / l, and the chloride ion content is 15-45 mg / l.

3. The method for preparing an ultra-high strength electrolytic copper foil according to claim 1, characterized in that: In step (3), the current during foil production is 20000-45000A, the voltage is 4.0V, and the cathode roller speed is 4.8-10.5m / min.

4. The method for preparing an ultra-high strength electrolytic copper foil according to claim 1, characterized in that: The additives include diluted hydrochloric acid, agent A, agent B, agent C, and agent D. Agent A is a small molecular sulfur-containing organic matter, agent B is a sulfur- or nitrogen-containing organic matter, agent C is a high molecular oxygen-containing compound, and agent D is a rare metal compound.

5. The method for preparing an ultra-high strength electrolytic copper foil according to claim 4, characterized in that: The content of agent A in the mixed electrolyte is 10-180 mg / l; the agent A is one or any combination of two or more of sodium polydisulfide propane sulfonate, sodium 3-mercaptopropane sulfonate, and tetrahydrothiazolidine-2-thione.

6. The method for preparing an ultra-high strength electrolytic copper foil according to claim 4, characterized in that: The content of agent B in the mixed electrolyte is 0.01-15 mg / l; the agent B is one or any combination of two or more of n-diethyl trithioamino performate, sodium formamide propane sulfonate, polyethylene imine alkyl salt, and pyridinium propane sulfonate.

7. The method for preparing an ultra-high strength electrolytic copper foil according to claim 4, characterized in that: The content of agent C in the mixed electrolyte is 0.01-25 mg / l; the agent C is one or any combination of two or more of polyethylene glycol, hydroxyethyl cellulose and allyl polyoxyethylene ether.

8. The method for preparing an ultra-high strength electrolytic copper foil according to claim 4, characterized in that: The content of agent D in the mixed electrolyte is 0.01-5 mg / l; the agent D is a mixture of propoxylated propargyl alcohol and tin molybdate compound; in the mixture, the mass ratio of propoxylated propargyl alcohol to tin molybdate compound is 1:2-4.

9. The method for preparing an ultra-high strength electrolytic copper foil according to claim 8, characterized in that: In the tin molybdate compound, the mass ratio of rare metal molybdenum to tin is 1:2.5-4.

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