Additive for 5-micron lithium-resistant copper foil and preparation method thereof

Abstract

This invention discloses an additive for 5-micron medium-resistance lithium-ion battery copper foil and its preparation method. The additive consists of sodium polydisulfide dipropane sulfonate, a composite wetting agent, hydrolyzed protein, and a composite medium-resistance agent. The amount of each component added per L of copper sulfate electrolyte is 1.61–6.46 mg of sodium polydisulfide dipropane sulfonate, 0.35–1.5 mg of the composite wetting agent, 2.19–11.16 mg of hydrolyzed protein, and 1.4–12.8 mg of the composite medium-resistance agent. Pretreated copper material is added to a copper dissolving tank, and pure water and dilute sulfuric acid are added to react and obtain a crude copper sulfate solution. The crude copper sulfate solution is filtered, purified, and temperature-adjusted to ensure that the copper ion concentration, sulfuric acid concentration, chloride ion concentration, and temperature in the resulting copper sulfate electrolyte reach the specified range. The additive is added to the copper sulfate electrolyte, and then the electrolyte is fed to a foil-making machine for electrolytic foil production to obtain 5-micron medium-resistance lithium-ion battery copper foil. Using this invention, medium-tensile lithium-ion battery copper foil with a tensile strength of 450-560 MPa and a thickness of 5 micrometers can be prepared, ensuring low warpage and no thermal cracking after heat treatment.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic copper foil manufacturing technology, specifically relating to an additive for 5-micron medium-sized lithium-ion battery copper foil and its preparation method. Background Technology

[0002] Lithium-ion battery copper foil is a key material for the negative electrode of power batteries, and its market demand is closely related to the new energy vehicle market. Currently, in 2024, new energy vehicles accounted for over 60% of the sales of domestically produced cars in my country. With the popularization of intelligent driving technology in 2025 and breakthroughs in flash charging technology by companies like BYD, the new energy vehicle market will continue to grow. This market development places higher demands on the energy density and safety of power batteries. For example, Guoyi's semi-solid-state battery has passed puncture tests, verifying its safety while simultaneously improving its energy density. To adapt to the development needs of solid-state / semi-solid-state batteries, lithium-ion battery copper foil needs to be upgraded towards ultra-thinness, high tensile strength, and high elongation.

[0003] However, current traditional additive systems such as sodium dithiopropane sulfonate, collagen, and hydroxyethyl cellulose are insufficient to stably prepare ultrathin copper foils with medium tensile strength that meet the aforementioned requirements. Therefore, developing a novel additive composition to replace traditional additives, simplifying the process, increasing cost-effectiveness, and simultaneously achieving ideal physical properties (especially medium to high tensile strength) has become a key focus of current additive research and development.

[0004] Currently, there are also relevant patent documents regarding lithium-ion battery copper foil. For example: 1. Invention patent CN 202210330584.3 discloses a method for reducing the unit area mass difference of medium-tensile lithium-ion battery copper foil. The general steps of this method are: a) storing copper sulfate electrolyte in a clean liquid tank; b) storing brightener, leveling agent, and leveling agent separately. The brightener is a mixture of sodium p-thiodipropanesulfonate and chloride ions, the leveling agent is a polyethyleneimine alkyl compound, and the leveling agent is collagen; c) adding additives to an additive storage tank; d) the additives flow to the clean liquid tank, and the additives and electrolyte are transported to the foil production system to electrolyze the foil. 2. Invention patent CN 202210583723.3 discloses a method for improving the elongation of 6µm medium-tensile lithium-ion battery copper foil. The prepared copper sulfate electrolyte is filtered and stored in a clean liquid tank. Brightener, leveling agent, and leveling agent, which are used as electroplating additives, are prepared separately and temporarily stored in brightener preparation tank, leveling agent preparation tank, and leveling agent preparation tank, respectively. The obtained brightener, leveling agent, and leveling agent are added to the additive storage tank to obtain a mixed additive. The mixed additive is then pumped to the clean liquid tank and mixed evenly with the copper sulfate electrolyte. The copper sulfate electrolyte containing the mixed additive is transported to the anode tank through the liquid distributor for electrolytic foil production. Summary of the Invention

[0005] The technical problem this invention aims to solve is the difficulty in stably preparing ultra-thin, medium-tensile strength copper foil that meets application requirements using traditional additive systems such as sodium dithiopropane sulfonate, collagen, and hydroxyethyl cellulose. This invention provides an additive for 5-micron medium-tensile strength lithium-ion battery copper foil and its preparation method. Through improvements to the additive formulation, this invention prepares 5-micron medium-tensile strength lithium-ion battery copper foil with a tensile strength of 450–560 MPa, ensuring low warpage and preventing thermal cracking after heat treatment.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] This invention provides an additive for 5-micron medium-resistance lithium battery copper foil, the additive being composed of sodium polydisulfide dipropane sulfonate, a composite wetting agent, hydrolyzed protein, and a composite medium-resistance agent; the amounts of each component added per L of copper sulfate electrolyte are as follows: sodium polydisulfide dipropane sulfonate 1.61–6.46 mg, composite wetting agent 0.35–1.5 mg, hydrolyzed protein 2.19–11.16 mg, and composite medium-resistance agent 1.4–12.8 mg.

[0008] According to the above-mentioned 5-micron medium-resistance lithium battery copper foil additive, the composite wetting agent is prepared by mixing hydroxyethyl cellulose and polyethylene glycol in a mass ratio of 2:1; the composite medium-resistance agent is prepared by mixing tetrahydrothiazolyl thiophene, agent F and agent G in a mass ratio of 12:25:1.

[0009] In addition, a method for preparing a 5-micron medium-sized lithium-ion battery-resistant copper foil is provided, the method comprising the following steps:

[0010] a. Add pure water and dilute sulfuric acid to the pretreated copper material to react and obtain crude copper sulfate solution;

[0011] b. The crude copper sulfate solution obtained in step a is filtered, purified, and temperature-adjusted; after treatment, the copper ion concentration, sulfuric acid concentration, chloride ion concentration, and temperature in the resulting copper sulfate electrolyte reach the specified range.

[0012] c. Add the above-mentioned additives to the copper sulfate electrolyte obtained after step b, and then electrolyze the electrolyte to form a foil, thus preparing a 5-micron medium-sized lithium-ion battery copper foil.

[0013] According to the above method for preparing 5-micron anti-lithium battery copper foil, the equipment used for the reaction in step a is a copper melting pot.

[0014] According to the above method for preparing 5-micron anti-lithium battery copper foil, the concentration of dilute sulfuric acid in step a is 100-110 g / L; the ratio of pure water, dilute sulfuric acid and copper material added is 50-80 m³ of pure water: 2.4-7.2 t of dilute sulfuric acid: 15-30 t of copper material.

[0015] According to the above-mentioned method for preparing 5-micron anti-lithium battery copper foil, the temperature of the crude copper sulfate solution in step a is 60-80℃; the sulfuric acid content in the crude copper sulfate solution is 30-90 g / L and the copper ion content is 110-150 g / L.

[0016] According to the above-mentioned method for preparing 5-micron anti-lithium battery copper foil, the copper ion concentration, sulfuric acid concentration, chloride ion concentration and temperature in the copper sulfate electrolyte obtained after treatment in step b are 92-98 g / L for copper ions, 100-110 g / L for sulfuric acid, 30-35 ppm for chloride ions and 50-55 °C for chloride ions.

[0017] According to the above-mentioned method for preparing 5-micron anti-lithium battery copper foil, in the electrolytic foil-making process described in step c: the equipment used is a foil-making machine, the electrolyte temperature is controlled at 50-55℃, and the current density on the cathode roller surface of the foil-making machine is 4200-6000 A / m. 2 Copper foil is formed on the surface of the cathode roller.

[0018] According to the above method for preparing 5-micron anti-lithium battery copper foil, the basis weight of the 5-micron anti-lithium battery copper foil obtained in step c is 44-46 g / m³. 2 Surface roughness Ra < 0.3, surface roughness Rz < 3, tensile strength 450-560 MPa, elongation at room temperature ≥ 4%.

[0019] The agent F used in the technical solution of this invention is isothiourea propanesulfonic acid inner salt, and the agent G used is sodium 3-mercapto-1-propanesulfonate.

[0020] The positive and beneficial effects of this invention are:

[0021] 1. The additives used in this invention employ a composite wetting agent formulated with polyethylene glycol and hydroxyethyl cellulose, constructing a two-component synergistic wetting system. The two components form a flexible adsorption film through hydrogen bonding. On one hand, this reduces the surface tension at the electrolyte / cathode interface, achieving highly efficient wetting. Compared to the conventional single polyethylene glycol / hydroxyethyl cellulose system with a wetting performance of 36-38 mN / m, this invention uses a composite wetting agent to optimize the interface wetting to 38-42 mN / m, significantly improving wetting efficiency. On the other hand, this adsorption film precisely controls the ion diffusion path during copper foil electrodeposition through steric hindrance. This synergistic mechanism not only achieves a breakthrough improvement in foil surface flatness (smooth surface Ra < 0.3 μm, rough surface Rz < 3 μm), but also increases the room temperature elongation of the medium-strength copper foil from the industry standard of 3-4% to 4-5%. Simultaneously, it forms a fine, dense, and uniformly sized copper crystal structure, significantly reducing pinhole defects.

[0022] 2. The additives used in this invention employ a composite neutralizing agent combination of tetrahydrothiazolylthione, agent F, and agent G, which can specifically target the copper deposition layer. Compared to traditional additive systems, its performance advantages and process stability are particularly prominent: the highest tensile strength of the neutralizing copper foil prepared by the traditional system is only 430 MPa, with a warpage of 13 mm, and it is easily affected by sodium polydisulfide dipropane sulfonate, causing the tensile strength to drop rapidly from 430 MPa to 390 MPa, which cannot meet the requirements of large-scale mass production; while the composite neutralizing agent combination of this invention can effectively avoid the above problems, significantly improving the flatness of the foil surface and the tensile strength within the elastic deformation range, producing a bright and fine copper foil, and ensuring process stability, keeping the product warpage within the permissible range, which is fully suitable for large-scale production scenarios.

[0023] 3. The additive system used in the technical solution of this invention is well-defined and has a clear ratio, making it easy to implement in existing electrolytic copper foil production lines. It is expected to simplify operation and reduce costs while achieving the target performance.

[0024] 4. The basis weight of the 5-micron anti-lithium battery copper foil prepared by this invention is 44-46 g / m³. 2 The surface roughness Ra < 0.3, the surface roughness Rz < 3, the tensile strength is 450-560 MPa, and the elongation at room temperature is ≥ 4%; it fully meets the requirements of lithium battery copper foil for ultra-thinness, high tensile strength, and high elongation. Detailed Implementation

[0025] The present invention will be further illustrated below with reference to the embodiments, but this does not limit the scope of protection of the technical solution of the present invention.

[0026] Example 1:

[0027] This invention relates to an additive for 5-micron medium-resistance lithium battery copper foil. The additive is composed of sodium polydisulfide dipropane sulfonate, a composite wetting agent, hydrolyzed protein, and a composite medium-resistance agent. The amounts of each component added per L of copper sulfate electrolyte are as follows: sodium polydisulfide dipropane sulfonate 5.25 mg, composite wetting agent 1.21 mg, hydrolyzed protein 8.92 mg, and composite medium-resistance agent 7.12 mg.

[0028] The composite wetting agent is prepared by mixing hydroxyethyl cellulose and polyethylene glycol in a mass ratio of 2:1; the composite neutralizing agent is prepared by mixing tetrahydrothiazolyl thionone, agent F and agent G in a mass ratio of 12:25:1; wherein agent F is isothiourea propanesulfonic acid inner salt and agent G is sodium 3-mercapto-1-propanesulfonate.

[0029] Example 2:

[0030] The detailed steps of the preparation method of the 5-micron anti-lithium battery copper foil of the present invention are as follows:

[0031] a. Add 23t of pretreated copper material to a copper melting tank, then add 65m³ of pure water and 4.8t of dilute sulfuric acid with a concentration of 105g / L to react and obtain a crude copper sulfate solution.

[0032] The temperature of the obtained crude copper sulfate solution was 70±2℃; the crude copper sulfate solution contained 60 g / L of sulfuric acid and 130 g / L of copper ions.

[0033] b. The crude copper sulfate solution obtained in step a is filtered, purified, and temperature-adjusted. After treatment, the copper ion concentration in the resulting copper sulfate electrolyte is 95 g / L, the sulfuric acid concentration is 105 g / L, the chloride ion concentration is 30 ppm, and the temperature is 51.5℃.

[0034] c. Add the additives described in Example 1 to the copper sulfate electrolyte obtained after step b (the amount of each component in the additives is added according to the amount of each component per L of copper sulfate electrolyte specified in Example 1), and then transport the electrolyte to a foil-making machine for electrolytic foil production, controlling the electrolyte temperature at 51.5℃ and the current density on the cathode roller surface of the foil-making machine at 6000 A / m. 2 A copper foil is formed on the surface of the cathode roller; a 5-micron medium-sized lithium-ion battery-resistant copper foil is prepared.

[0035] The lithium-ion battery copper foil prepared in this embodiment of the invention has a basis weight of 44-46 g / m³. 2 The surface roughness Ra < 0.3, the surface roughness Rz < 3, the tensile strength 450-560 MPa, and the elongation at room temperature ≥ 4%. Therefore, the composite wetting agent and composite neutralizing agent used in this invention effectively improve the tensile strength while maintaining the original excellent physical properties of the copper foil.

[0036] In copper foil production, warpage exceeding 10mm can cause substrate folding during downstream battery manufacturing, affecting the coating of active materials. Low tensile strength copper foil can lead to water ripples and breakage during manufacturing. Moreover, lithium-ion secondary batteries on the market have high requirements for tensile strength to improve quality. The copper foil prepared by this invention meets the market's high strength requirements for electrolytic copper foil.

[0037] The performance of the electrolytic copper foil prepared by the present invention will be further illustrated below through comparison with examples and comparative examples.

[0038] The following examples and control examples all used a copper ion concentration of 95 g / L, a sulfuric acid concentration of 105 g / L, a chloride ion concentration of 30 ppm, an electrolyte temperature of 51.5 ± 1.5 °C, and a cathode roller surface current density of 5200 A / m. 2This invention aims to verify whether a composite neutralizing agent can replace traditional additives in the manufacture of 5-micron neutralizing lithium-ion battery copper foil. Therefore, comparative examples were used with different concentrations of sodium polydisulfide dipropane sulfonate and hydrolyzed protein, ranging from 5.04 to 5.68 mg / L and 6.6 to 7.2 mg / L, respectively, to verify whether there were similar effects between the two groups. The following examples and comparative examples are identical except for the type and concentration of additives; the electrolyte concentration, temperature, and current density are the same. Specific additive compositions are detailed in Table 1.

[0039] Table 1. Composition of additives in the examples and comparative examples

[0040] In Table 1, the composite wetting agent used is prepared by mixing hydroxyethyl cellulose and polyethylene glycol in a mass ratio of 2:1; the composite neutralizing agent used is prepared by mixing tetrahydrothiazolyl thiophene, agent F and agent G in a mass ratio of 12:25:1.

[0041] The preparation methods used in Examples 1-7 and Comparative Examples 1-3 in Table 1 are the same as those used in Example 2 above. The tensile strength, elongation, roughness, warpage, and surface defects of the prepared 5-micron copper foil were tested and observed, and the specific test results are detailed in Table 2.

[0042] Table 2 Comparison of relevant properties of copper foils prepared in Examples 1-7 and Comparative Examples 1-3

[0043]

[0044] As shown in Table 2, the results of Examples 1-5 and Comparative Examples 1-3 of this invention demonstrate that the 5-micron copper foil prepared using the composite neutralizing agent, composite wetting agent, sodium polydisulfide dipropane sulfonate, and hydrolyzed protein of this invention can maintain lower warpage while increasing tensile strength compared to traditional copper foil, but it will reduce the elongation of the copper foil. Furthermore, Examples 6-7 show that when the composite neutralizing agent is added in excess, although the tensile strength increases, it will cause severe warpage, and spots will occasionally appear on the foil surface, rendering the lithium battery copper foil unusable.

[0045] In summary, the additive system of this invention, through the synergistic effect of a rationally proportioned composite wetting agent and composite neutralizing agent, significantly improves the tensile strength of copper foil while maintaining ultra-low surface roughness and acceptable elongation. Compared to traditional additive systems, the technical solution of this invention achieves a tensile strength increase of over 40% with lower concentrations of sodium polydisulfide dipropane sulfonate and hydrolyzed protein, while maintaining warpage stably controlled at ≤4mm. This system simplifies the types of additives, reduces the risk of organic contaminants, and is compatible with existing production line processes, providing a reliable solution for the efficient and stable production of ultra-thin lithium-ion battery copper foil.

Claims

1. An additive for 5-micron medium-sized lithium-ion battery-resistant copper foil, characterized in that, The additive consists of sodium polydisulfide dipropane sulfonate, a composite wetting agent, hydrolyzed protein, and a composite neutralizing agent; the amounts of each component added per L of copper sulfate electrolyte are as follows: sodium polydisulfide dipropane sulfonate 1.61–6.46 mg, composite wetting agent 0.35–1.5 mg, hydrolyzed protein 2.19–11.16 mg, and composite neutralizing agent 1.4–12.8 mg.

2. The additive for 5-micron anti-lithium battery copper foil according to claim 1, characterized in that: The composite wetting agent is prepared by mixing hydroxyethyl cellulose and polyethylene glycol in a mass ratio of 2:1; the composite neutralizing agent is prepared by mixing tetrahydrothiazothione, agent F and agent G in a mass ratio of 12:25:

1.

3. A method for preparing a 5-micron medium-sized lithium-ion battery-resistant copper foil, characterized in that, The preparation method includes the following steps: a. Add pure water and dilute sulfuric acid to the pretreated copper material to react and obtain crude copper sulfate solution; b. The crude copper sulfate solution obtained in step a is filtered, purified, and temperature-adjusted; after treatment, the copper ion concentration, sulfuric acid concentration, chloride ion concentration, and temperature in the resulting copper sulfate electrolyte reach the specified range. c. Add the additive described in claim 1 to the copper sulfate electrolyte obtained after step b, and then electrolyze the electrolyte to form a foil, thereby preparing a 5-micron medium-sized lithium-ion battery copper foil.

4. The method for preparing 5-micron anti-lithium battery copper foil according to claim 3, characterized in that: The equipment used for the reaction in step a is a copper melting pot.

5. The method for preparing 5-micron anti-lithium battery copper foil according to claim 3, characterized in that: The concentration of the dilute sulfuric acid in step a is 100-110 g / L; the ratio of pure water, dilute sulfuric acid and copper material added is 50-80 m³ of pure water: 2.4-7.2 t of dilute sulfuric acid: 15-30 t of copper material.

6. The method for preparing 5-micron anti-lithium battery copper foil according to claim 3, characterized in that: The temperature of the crude copper sulfate solution in step a is 60-80℃; the sulfuric acid content in the crude copper sulfate solution is 30-90 g / L and the copper ion content is 110-150 g / L.

7. The method for preparing 5-micron anti-lithium battery copper foil according to claim 3, characterized in that: The copper ion concentration, sulfuric acid concentration, chloride ion concentration, and temperature in the copper sulfate electrolyte obtained after treatment in step b are 92-98 g / L for copper ions, 100-110 g / L for sulfuric acid, 30-35 ppm for chloride ions, and 50-55 °C for chloride ions.

8. The method for preparing 5-micron anti-lithium battery copper foil according to claim 3, characterized in that, In step c, during the electrolytic foil-making process, the equipment used is a foil-making machine, and the electrolyte temperature is controlled at 50–55°C, while the current density on the cathode roller surface of the foil-making machine is 4200–6000 A / m. 2 Copper foil is formed on the surface of the cathode roller.

9. The method for preparing 5-micron anti-lithium battery copper foil according to claim 3, characterized in that: The basis weight of the 5-micron lithium-ion battery-resistant copper foil obtained in step c is 44–46 g / m². 2 Surface roughness Ra < 0.3, surface roughness Rz < 3, tensile strength 450-560 MPa, elongation at room temperature ≥ 4%.

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