A rolled copper foil for lithium ion battery current collector and a method for manufacturing the same

Abstract

The application belongs to the technical field of electrode materials, and particularly discloses a calendered copper foil for lithium ion battery current collector and a preparation method thereof. The calendered copper foil is sequentially subjected to degreasing treatment, acid pickling activation, roughening treatment, carbon modification treatment and oxidation resistance treatment to obtain the calendered copper foil for lithium ion battery current collector. The carbon modification treatment comprises the following steps: coating a carbon material dispersion liquid on the surface of the calendered copper foil after the roughening treatment, and performing solidification treatment to complete the carbon modification treatment. The calendered copper foil is subjected to multi-step treatment, the surface roughness of the calendered copper foil is improved, the adhesion of the battery negative active material on the copper foil is facilitated, the stability of the electrode is improved, and the conductivity of the high-calendered copper foil is improved.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and in particular to a rolled copper foil for lithium-ion battery current collectors and its preparation method. Background Technology

[0002] As the core technology in the current energy storage field, the performance improvement of lithium-ion batteries depends heavily on the innovative breakthroughs in key materials. Among them, the current collector, as the core component that carries active materials and conducts electrons, directly affects the energy density, power characteristics and cycle life of the battery. Lithium-ion battery anodes typically use electrolytic copper foil or rolled copper foil as current collectors. Electrolytic copper foil possesses good conductivity and suitable surface roughness. However, as battery technology rapidly advances towards higher energy density, fast charging, and long cycle life, the inherent defects of electrolytic copper foil are becoming increasingly prominent: First, the copper foil prepared by electrolytic processes exhibits significant anisotropy, with a marked difference between longitudinal and transverse tensile strength. This can easily lead to stress concentration and breakage during the rolling process of battery electrodes, especially when the foil thickness is reduced to below 6μm, resulting in a significant decrease in processing yield. Second, the surface roughness of electrolytic copper foil is not well-matched with the active material. When the volume change of high-nickel cathodes or silicon-based anodes is too large during charging and discharging, it can easily cause coating peeling. Furthermore, the crystal structure of electrolytic copper foil exhibits preferred crystal orientation, which can easily lead to the formation of dendrites that penetrate the separator during lithium-ion deposition.

[0003] Compared to electrolytic copper foil, rolled copper foil exhibits superior mechanical properties and conductivity as an electrode current collector. Its fibrous grain structure provides higher ductility and bending resistance, enabling it to withstand repeated deformations during dynamic charge and discharge processes without cracking, making it particularly suitable for flexible battery designs. Its surface finish is superior to electrolytic copper foil, reducing interfacial impedance and improving electron transport efficiency. Higher copper purity results in better conductivity and thickness uniformity, which is beneficial for the manufacture of high-energy-density batteries.

[0004] However, rolled copper foil has a smooth surface and lacks a porous structure, resulting in weaker adhesion of active materials (such as graphite and silicon) compared to electrolytic copper foil, leading to the problem of active materials easily detaching. Meanwhile, to meet the manufacturing requirements of high-energy-density batteries, its conductivity also needs further improvement. Summary of the Invention

[0005] In view of this, the present invention provides a rolled copper foil for lithium-ion battery current collectors and a method for preparing the same, in order to solve the problems of the current rolled copper foil having too small a roughness and poor adhesion to the active components, as well as the need to further improve its conductivity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing rolled copper foil for lithium-ion battery current collectors includes the following steps:

[0008] The rolled copper foil is subjected to degreasing, pickling and activation, roughening, carbon modification and anti-oxidation treatment in sequence to obtain rolled copper foil for lithium-ion battery current collectors.

[0009] The carbon modification process includes: coating a carbon material dispersion onto the surface of a roughened rolled copper foil, followed by curing to complete the carbon modification process.

[0010] Preferably, the thickness of the rolled copper foil is 8–20 μm.

[0011] Preferably, the degreasing process includes sequential alkaline washing degreasing and electrolytic degreasing.

[0012] Preferably, the degreasing agent in the alkaline washing degreasing is a mixture of sodium hydroxide solution and anionic surfactant; the concentration of sodium hydroxide in the degreasing agent is 25-30 g / L, and the mass concentration of the anionic surfactant is 0.1-0.3%;

[0013] The alkaline washing and degreasing temperature is 60-70℃, and the alkaline washing and degreasing time is ≥0.5min.

[0014] Preferably, the electrolyte for electrolytic degreasing is a mixed solution of sodium hydroxide and sodium carbonate;

[0015] The concentration of sodium hydroxide in the electrolyte is 25-30 g / L, and the concentration of sodium carbonate is 25-35 g / L.

[0016] The current density for the electrolytic degreasing is 6–8 A / dm³. 2 The temperature is 50-60℃ and the time is 10-100s.

[0017] Preferably, the pickling and activation step involves immersing the degreased rolled copper foil in an acid solution to complete the pickling and activation.

[0018] The acid solution includes sulfuric acid solution and hydrochloric acid solution; the mass concentration of the acid solution is 5-20%;

[0019] The immersion time in the acid solution is 1 to 2 minutes.

[0020] Preferably, the concentration of ferric chloride in the roughening solution of the roughening treatment is 80-150 g / L, the concentration of hydrochloric acid is 30-50 g / L, and the concentration of gum arabic is 0.005-0.02 g / L.

[0021] The roughening process takes 10 to 100 seconds.

[0022] Preferably, the carbon material in the carbon material dispersion includes graphene dispersion and carbon nanotube dispersion.

[0023] Preferably, the coating amount of the carbon material dispersion is 0.05–3 mg / cm³ based on the carbon material. 2 ;

[0024] The curing temperature is 300–400°C, the curing time is 0.5–1.5 h, and the curing atmosphere is an inert atmosphere.

[0025] Another object of the present invention is to provide a rolled copper foil for lithium-ion battery current collectors prepared by the above-described preparation method.

[0026] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention improves the surface roughness of rolled copper foil by performing multi-step processing, which is beneficial to the adhesion of battery negative electrode active material on copper foil and improves electrode stability.

[0028] 2. This invention incorporates a degreasing treatment, which removes contaminants from the surface of the rolled copper foil, improving surface energy and wettability. Acid pickling and activation avoid alkaline residues from the degreasing process and remove the oxide layer; activation of the rolled copper foil surface allows for uniform corrosion through roughening, preventing uneven roughness. The roughening treatment creates micropores of micro / nano-agents on the surface of the rolled copper foil, increasing its roughness and adhesion to the negative electrode active components; it also inhibits lithium dendrite formation. The carbon material in the carbon modification treatment solidifies within the micropores on the surface of the rolled copper foil, forming a barbed effect that mechanically interlocks with the surface. During solidification, a copper-carbon interface is formed under heating conditions, enhancing the bonding of the carbon material. Simultaneously, the carbon modification treatment significantly improves the conductivity of the rolled copper foil. Detailed Implementation

[0029] This invention provides a method for preparing rolled copper foil for lithium-ion battery current collectors, comprising the following steps:

[0030] The rolled copper foil is subjected to degreasing, acid pickling and activation, roughening, carbon modification and anti-oxidation treatment in sequence to obtain rolled copper foil for lithium-ion battery current collectors.

[0031] In this invention, the carbon modification process includes: coating a carbon material dispersion onto the surface of a roughened rolled copper foil, and then performing a curing process to complete the carbon modification process.

[0032] In this invention, the thickness of the rolled copper foil is 8–20 μm, specifically 10 μm, 12 μm, 14 μm, 15 μm, 16 μm, or 18 μm. The rolled copper foil of this invention is preferably battery-grade rolled copper foil.

[0033] In this invention, the degreasing process includes sequential alkaline washing degreasing and electrolytic degreasing.

[0034] In this invention, the degreasing agent in the alkaline washing degreasing is a mixture of sodium hydroxide solution and an anionic surfactant; the concentration of sodium hydroxide in the degreasing agent is 25-30 g / L, specifically 26 g / L, 27 g / L, 28 g / L, or 29 g / L; the mass concentration of the anionic surfactant is 0.1-0.3%, specifically 0.12%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, or 0.28%. The anionic surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium fatty alcohol polyoxyethylene ether sulfate.

[0035] In this invention, the temperature of alkaline washing and degreasing is 60-70℃, specifically 62℃, 64℃, 65℃, 66℃, or 68℃; the time of alkaline washing and degreasing is ≥0.5min, specifically 0.6min, 0.8min, 1min, 2min, 4min, 5min, or 6min.

[0036] In this invention, the electrolyte for electrolytic degreasing is a mixed solution of sodium hydroxide and sodium carbonate.

[0037] In this invention, the concentration of sodium hydroxide in the electrolyte is 25-30 g / L, specifically 26 g / L, 27 g / L, 28 g / L, or 29 g / L; the concentration of sodium carbonate is 25-35 g / L, specifically 26 g / L, 28 g / L, 30 g / L, 32 g / L, or 34 g / L.

[0038] In this invention, the current density for electrolytic degreasing is 6-8 A / dm³. 2 Specifically, it can be 6.2A / dm 2 6.5A / dm 2 6.8A / dm 2 7A / dm 2 7.2A / dm 2 7.5A / dm 2 7.8A / dm 2 The temperature is 50-60℃, specifically 52℃, 54℃, 55℃, 56℃, and 58℃; the time is 10-100s, specifically 20s, 30s, 40s, 50s, 60s, 70s, 80s, and 90s.

[0039] In this invention, the pickling and activation step involves immersing the degreased rolled copper foil in an acid solution to complete the pickling and activation.

[0040] In this invention, the acid solution includes sulfuric acid solution and hydrochloric acid solution; the mass concentration of the acid solution is 5% to 20%, specifically 6%, 8%, 10%, 12%, 14%, 15%, 16%, and 18%.

[0041] In this invention, the immersion time in acid solution is 1 to 2 minutes, specifically 1.2 minutes, 1.4 minutes, 1.5 minutes, 1.6 minutes, or 1.8 minutes.

[0042] In this invention, the concentration of ferric chloride in the roughening solution of the roughening treatment is 80-150 g / L, specifically 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, or 140 g / L; the concentration of hydrochloric acid is 30-50 g / L, specifically 32 g / L, 35 g / L, 38 g / L, 40 g / L, 42 g / L, 45 g / L, or 48 g / L; and the concentration of gum arabic is 0.005-0.02 g / L, specifically 0.008 g / L, 0.01 g / L, 0.012 g / L, 0.015 g / L, or 0.018 g / L.

[0043] In this invention, the roughening process takes 10 to 100 seconds, specifically 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, or 90 seconds.

[0044] In this invention, the carbon materials in the carbon material dispersion include graphene dispersion and carbon nanotube dispersion.

[0045] In this invention, the coating amount of the carbon material dispersion is 0.05–3 mg / cm³, calculated based on the carbon material. 2 Specifically, it can be 0.1 mg / cm³. 2 0.2 mg / cm 2 0.5 mg / cm 2 0.8 mg / cm 2 1mg / cm 2 1.5 mg / cm 2 2mg / cm 2 2.5 mg / cm 2 .

[0046] In this invention, the curing temperature is 300-400℃, specifically 320℃, 340℃, 350℃, 360℃, or 380℃; the curing time is 0.5-1.5h, specifically 0.6h, 0.8h, 1h, 1.2h, or 1.4h; and the curing atmosphere is an inert atmosphere.

[0047] In this invention, the antioxidant treatment is to form a passivation film on the surface of rolled copper foil using benzotriazole.

[0048] The present invention also provides a rolled copper foil for lithium-ion battery current collectors prepared by the above preparation method.

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] The rolled copper foil used in the embodiments of the present invention is ordinary commercially available battery-grade rolled copper foil (available in 12μm and 18μm models).

[0051] Example 1

[0052] A rolled copper foil (12μm) was immersed in a mixed solution of sodium hydroxide and sodium dodecylbenzenesulfonate (sodium hydroxide concentration 25g / L, sodium dodecylbenzenesulfonate concentration 0.2%). The alkaline washing and degreasing agent temperature was controlled at 60℃ for 2 minutes. Then, it was placed in an electrolyte at 60℃ (sodium hydroxide concentration 25g / L, sodium carbonate concentration 30g / L), kept connected to the negative terminal of the power supply, and a 316L stainless steel plate was connected to the positive terminal of the power supply with a distance of 50mm between the electrodes. The current density was controlled at 8A / dm³. 2 Process for 30 seconds, remove and wash until the pH of the wash water is neutral, thus completing the degreasing treatment of the rolled copper foil.

[0053] The degreased rolled copper foil was immersed in a 10% sulfuric acid solution for 1 minute, then removed and washed to complete the acid pickling and activation treatment. Then it was placed in a roughening solution (ferric chloride concentration of 80 g / L, hydrochloric acid concentration of 35 g / L, and gum arabic concentration of 0.01 g / L) for 30 seconds. After washing, the roughened rolled copper foil was obtained, and the surface of the rolled copper foil had tiny micropores.

[0054] A graphene dispersion was coated onto the surface of a roughened rolled copper foil, resulting in a graphene coating amount of 2 mg / cm². 2 Then, under a nitrogen atmosphere, it is cured at 350°C for 1 hour. After curing, a passivation film is formed on the surface of the rolled copper foil using benzotriazole to obtain rolled copper foil for lithium-ion battery current collectors.

[0055] According to GB / T 36146—2018, the tensile strength is 452 MPa and the elongation after fracture is 1.8%, indicating good mechanical properties.

[0056] Example 2

[0057] A rolled copper foil (12μm) was immersed in a mixed solution of sodium hydroxide and sodium dodecylbenzenesulfonate (sodium hydroxide concentration 26g / L, sodium dodecylbenzenesulfonate concentration 0.1%). The temperature of the alkaline washing degreasing agent was controlled at 60℃ and maintained for 2 minutes. Then, it was placed in an electrolyte at 60℃ (sodium hydroxide concentration 30g / L, sodium carbonate concentration 28g / L), kept connected to the negative terminal of the power supply, and a 316L stainless steel plate was connected to the positive terminal of the power supply with a distance of 50mm between the electrodes. The current density was controlled at 6A / dm³. 2 Process for 50 seconds, remove and wash until the pH of the wash water is neutral, thus completing the degreasing treatment of the rolled copper foil.

[0058] The degreased rolled copper foil was immersed in a 10% sulfuric acid solution for 1 minute, then removed and washed to complete the acid pickling and activation treatment. Then it was placed in a roughening solution (ferric chloride concentration of 100 g / L, hydrochloric acid concentration of 30 g / L, and gum arabic concentration of 0.01 g / L) for 20 seconds, then removed and washed to obtain the roughened rolled copper foil. The surface of the rolled copper foil has tiny micropores.

[0059] A graphene dispersion was coated onto the surface of a roughened rolled copper foil, resulting in a graphene coating amount of 2 mg / cm². 2 Then, under a nitrogen atmosphere, it is cured at 400°C for 1 hour. After curing, a passivation film is formed on the surface of the rolled copper foil using benzotriazole to obtain rolled copper foil for lithium-ion battery current collectors.

[0060] According to GB / T 36146—2018, the tensile strength is 446MPa and the elongation after fracture is 1.8%, indicating good mechanical properties.

[0061] Example 3

[0062] A rolled copper foil (12μm) was immersed in a mixed solution of sodium hydroxide and sodium dodecylbenzenesulfonate (sodium hydroxide concentration 30g / L, sodium dodecylbenzenesulfonate concentration 0.1%). The temperature of the alkaline washing degreasing agent was controlled at 70℃ and maintained for 0.5min. Then, it was placed in an electrolyte at 50℃ (sodium hydroxide concentration 25g / L, sodium carbonate concentration 25g / L), kept connected to the negative terminal of the power supply, and a 316L stainless steel plate was connected to the positive terminal of the power supply with a distance of 50mm between the electrodes. The current density was controlled at 7A / dm³. 2 Process for 10 seconds, remove and wash until the pH of the wash water is neutral, thus completing the degreasing treatment of the rolled copper foil.

[0063] The degreased rolled copper foil was immersed in a 10% sulfuric acid solution for 2 minutes, then removed and washed to complete the acid pickling and activation treatment. Then it was placed in a roughening solution (ferric chloride concentration of 150 g / L, hydrochloric acid concentration of 30 g / L, and gum arabic concentration of 0.005 g / L) for 10 seconds, then removed and washed to obtain the roughened rolled copper foil. The surface of the rolled copper foil has tiny micropores.

[0064] A carbon nanotube dispersion was coated onto the surface of a roughened rolled copper foil, resulting in a carbon nanotube coating amount of 0.05 mg / cm². 2 Then, under a nitrogen atmosphere, it is cured at 300°C for 1.5 hours. After curing, a passivation film is formed on the surface of the rolled copper foil using benzotriazole to obtain rolled copper foil for lithium-ion battery current collectors.

[0065] According to GB / T 36146—2018, the tensile strength is 449 MPa and the elongation after fracture is 1.7%, indicating good mechanical properties.

[0066] Example 4

[0067] A rolled copper foil (18 μm) was immersed in a mixed solution of sodium hydroxide and sodium dodecylbenzenesulfonate (sodium hydroxide concentration 28 g / L, sodium dodecylbenzenesulfonate concentration 0.3%), and the alkaline washing and degreasing agent temperature was controlled at 70℃ for 1 min. Then it was placed in an electrolyte solution at 60℃ (sodium hydroxide concentration 30 g / L, sodium carbonate concentration 25 g / L), kept connected to the negative terminal of the power supply, and a 316L stainless steel plate was connected to the positive terminal of the power supply with a 50 mm electrode gap. The current density was controlled at 8 A / dm³. 2 Process for 20 seconds, remove and wash until the pH of the wash water is neutral, thus completing the degreasing treatment of the rolled copper foil.

[0068] The degreased rolled copper foil was immersed in a 10% sulfuric acid solution for 1 minute, then removed and washed to complete the acid pickling and activation treatment. Then it was placed in a roughening solution (ferric chloride concentration of 120 g / L, hydrochloric acid concentration of 50 g / L, and gum arabic concentration of 0.02 g / L) for 60 seconds. After washing, the roughened rolled copper foil was obtained, and the surface of the rolled copper foil had tiny micropores.

[0069] A carbon nanotube dispersion was coated onto the surface of a roughened rolled copper foil, resulting in a carbon nanotube coating amount of 0.08 mg / cm². 2 Then, under a nitrogen atmosphere, it is cured at 300°C for 1 hour. After curing, a passivation film is formed on the surface of the rolled copper foil using benzotriazole to obtain rolled copper foil for lithium-ion battery current collectors.

[0070] According to GB / T 36146—2018, the tensile strength is 483 MPa and the elongation after fracture is 1.9%, indicating good mechanical properties.

[0071] Comparative Example 1

[0072] The untreated rolled copper foil from Example 1 was used as Comparative Example 1.

[0073] The adhesion of Example 1 and Comparative Example 1 was tested separately. Copper foil coated with negative electrode material was fixed on a substrate, and a 180° peel test was performed using an Instron universal testing machine at a uniform speed to measure the peel force. The test results showed that, under the same test conditions, the rolled copper foil obtained in Example 1 of this invention improved by 35.5% compared to the test results in Comparative Example 1. After assembling the battery, under 1C conditions, the capacity retention rate was tested 200 times. Example 1 of this invention improved by 5.6% compared to Comparative Example 1, reaching 95.2%. The rolled copper foil processing method disclosed in this invention is beneficial for improving the stability of lithium-ion batteries.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0075] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing rolled copper foil for lithium-ion battery current collectors, characterized in that, Includes the following steps: The rolled copper foil is subjected to degreasing, pickling and activation, roughening, carbon modification and anti-oxidation treatment in sequence to obtain rolled copper foil for lithium-ion battery current collectors. The carbon modification process includes: coating a carbon material dispersion onto the surface of a roughened rolled copper foil, followed by curing to complete the carbon modification process; The concentration of ferric chloride in the roughening solution of the roughening treatment is 80~150 g / L, the concentration of hydrochloric acid is 30~50 g / L, and the concentration of gum arabic is 0.005~0.02 g / L. The roughening process takes 10-100 seconds. The carbon materials in the carbon material dispersion include graphene dispersion and carbon nanotube dispersion. The coating amount of the carbon material dispersion is 0.05~3 mg / cm³ based on the carbon material. 2 ; The curing temperature is 300~400℃, the curing time is 0.5~1.5h, and the curing atmosphere is an inert atmosphere.

2. The method for preparing rolled copper foil for lithium-ion battery current collectors according to claim 1, characterized in that, The thickness of the rolled copper foil is 8~20μm.

3. The method for preparing rolled copper foil for lithium-ion battery current collectors according to claim 2, characterized in that, The degreasing process includes sequential alkaline washing and electrolytic degreasing.

4. The method for preparing rolled copper foil for lithium-ion battery current collectors according to claim 3, characterized in that, The degreasing agent in the alkaline washing degreasing is a mixture of sodium hydroxide solution and anionic surfactant; the concentration of sodium hydroxide in the degreasing agent is 25~30 g / L, and the mass concentration of the anionic surfactant is 0.1~0.3%; The alkaline washing and degreasing temperature is 60~70℃, and the alkaline washing and degreasing time is ≥0.5min.

5. The method for preparing rolled copper foil for lithium-ion battery current collectors according to claim 4, characterized in that, The electrolyte for the electrolytic degreasing is a mixed solution of sodium hydroxide and sodium carbonate; The concentration of sodium hydroxide in the electrolyte is 25~30 g / L, and the concentration of sodium carbonate is 25~35 g / L; The current density for electrolytic degreasing is 6~8 A / dm³. 2 The temperature is 50~60℃ and the time is 10~100s.

6. A method for preparing rolled copper foil for lithium-ion battery current collectors according to any one of claims 1 to 5, characterized in that, The pickling and activation step involves immersing the degreased rolled copper foil in an acid solution to complete the pickling and activation process. The acid solution includes sulfuric acid solution and hydrochloric acid solution; the mass concentration of the acid solution is 5-20%. The immersion time in the acid solution is 1 to 2 minutes.

7. The rolled copper foil for lithium-ion battery current collector prepared by the preparation method according to any one of claims 1 to 6.