Method for enhancing tensile strength and elongation of microporous copper foil

Abstract

The invention relates to a method for enhancing tensile strength and elongation of a microporous copper foil, which is used for improving the mechanical property of the microporous copper foil. On the basis of the existing microporous copper foil, the microporous copper foil and pore surfaces are modified through a pulse electrochemical post-treatment technology. According to the method, on the basis of an existing microporous copper foil, by controlling parameters of positive and negative pulse current, a uniform and fine plating layer is formed on the microporous copper foil and the pore surface of the microporous copper foil, meanwhile, defects and abnormal protrusions are reduced, and therefore the mechanical property of the microporous copper foil is remarkably improved. The treatment process not only improves the elongation of the microporous copper foil, but also ensures that the tensile strength of the microporous copper foil is kept at an ideal level, so that the overall performance of the copper foil in battery manufacturing and use is expected to be optimized.

Description

Technical Field

[0001] The invention relates to a method for enhancing the tensile strength and elongation of a microporous copper foil, belonging to the technical field of energy storage batteries. Background Art

[0002] With the continuous advancement of battery technology, the market demand for large-capacity, fast-charging batteries is growing, and there is also widespread concern about the development of differentiated products. As the negative electrode current collector of the battery, copper foil plays a vital role in the battery's charge and discharge performance, directly affecting the battery's overall performance and service life. In the production process of large-cell batteries, problems such as slow electrolyte infiltration speed gradually emerge. For these problems, the application of microporous copper foil has shown a significant solution effect.

[0003] However, due to the special preparation process and microporous structure of existing microporous copper foil products, their mechanical properties, especially elongation, are lower than those of traditional non-porous copper foil. The tensile strength and elongation of copper foil are two key indicators to measure its performance. Insufficient elongation may cause quality problems such as broken tape during battery coating or manufacturing, thereby affecting the production efficiency and yield of the battery. In addition, during the actual charging and discharging process of the battery, the performance of the copper foil also has a direct impact on the battery life and stability. Summary of the invention

[0004] The purpose of the invention to be achieved is: in order to solve the problem of low tensile strength and elongation of existing microporous copper foil, this patent provides an innovative method for improving the mechanical properties of microporous copper foil.

[0005] To achieve the above object, the technical scheme of the present invention is as follows: a method for enhancing the tensile strength and elongation of microporous copper foil, characterized in that: microporous copper foil I is used as a cathode and pulse electroplating is performed in electrolyte II; the temperature is room temperature, and the negative pulse current density is -0.5 to -20A / dm 2 , positive pulse current density is 0~1A / dm 2 , pulse period is 8-100ms, negative pulse duration is 2-15ms, positive pulse duration is 6-90ms; electrolyte II is copper pyrophosphate electrolyte containing additives; the composition and concentration range of the copper pyrophosphate electrolyte containing additives are as follows: copper pyrophosphate Cu2P2O7 concentration range is 20-50g / L, potassium pyrophosphate K4P2O7 concentration range is 250-300g / L, the additive is one of 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, sodium polydisulfide dipropane sulfonate (SPS), and benzotriazole, and the concentration range is 0.005-0.3g / L.

[0006] In the above electrolyte II, Cu 2+Provides the main salt, potassium pyrophosphate is a complexing agent, its role is to stabilize the complex, prevent precipitation, and improve the crystallization of the coating: Cu2P2O7+3K4P2O7=2K6[Cu(P2O7)2]. At the beginning of electroplating, copper ions need to get rid of the complex ions, and then combine with electrons at the electrode | electrolyte interface to be reduced. Due to the high stability of copper pyrophosphate complex ions, the process of removing the pyrophosphate complex consumes a lot of energy, and the reduction rate of copper ions is relatively slow, resulting in finer crystallization of the coating. A certain amount of free potassium pyrophosphate must be maintained in the electrolyte, its role is to make the complex more stable, prevent copper pyrophosphate precipitation, and improve the dispersion ability of the plating solution. Additives such as 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, benzotriazole, polydisulfide dipropane sulfonate and other small molecules can be adsorbed on the surface of the micropores, improve the distribution of current on the surface of the micropores, and thus achieve the purpose of modifying the morphology inside the pores.

[0007] In pulse plating, due to the off / positive current time, the consumed metal ions diffuse and replenish near the cathode during this time. When the next on / negative current time comes, the metal ion concentration near the cathode is restored, so a higher current density can be used. The peak current of pulse plating can be much higher than the average current, which makes the formation speed of crystal seeds higher than the growth speed of crystals, making the coating crystallization refined.

[0008] The current density of the negative pulse current is much higher than that of the positive pulse current, ensuring that a fine, uniform and high-density copper coating is deposited on the surface of the microporous copper foil and inside the pores. This coating can effectively fill the tiny defects and gaps inside the micropores and enhance the overall mechanical properties of the copper foil. After the negative pulse current electroplating, a positive pulse current of lower intensity is applied. The role of the positive pulse current is to alleviate the concentration polarization phenomenon generated during the negative pulse current electroplating process and avoid the non-uniform deposition of the coating due to the concentration gradient. Due to the tip effect of the electric field, the positive pulse current can selectively dissolve the abnormal protrusions on the surface of the copper foil, eliminate the surface roughness, and improve the flatness of the copper foil surface, thereby reducing potential structural defects.

[0009] The technical solution for further improving the device of the present invention is as follows:

[0010] Preferably, the iridium-plated titanium plate III serves as the anode.

[0011] Preferably, the microporous copper foil I needs to be pretreated before electroplating, using 10% dilute H2SO4 to remove the oxide layer on the surface of the microporous copper foil, and then washing with pure water to obtain a microporous copper foil I without an oxide layer.

[0012] The beneficial effects of the present invention are as follows: on the basis of the existing microporous copper foil, the microporous copper foil and the pore surface are modified by pulse electrochemical post-treatment technology. On the basis of the existing microporous copper foil, this method forms a uniform and delicate coating on the microporous copper foil and its pore surface by controlling the parameters of the positive and negative pulse currents, while reducing defects and abnormal protrusions, thereby significantly improving the mechanical properties of the microporous copper foil. This treatment process not only improves the elongation of the microporous copper foil, but also ensures that its tensile strength remains at an ideal level, which is expected to optimize the overall performance of the copper foil in battery manufacturing and use. The advantage of this technology is that the pulse electrochemical post-treatment of the existing microporous copper foil can effectively solve the problem of copper foil breakage caused by insufficient mechanical properties. This not only helps to improve the manufacturing stability and service life of the battery, but also can meet the requirements of large-cell batteries for high-performance current collectors, providing strong support for the advancement of a new generation of battery technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Comparison of the morphology of the original microporous copper foil and the enhanced microporous copper foil; DETAILED DESCRIPTION

[0014] Example 1

[0015] A method for enhancing the tensile strength and elongation of microporous copper foil, comprising the following steps:

[0016] a. Use 10% diluted H2SO4 to remove the oxide layer on the surface of the microporous copper foil, and wash it with pure water to obtain a microporous copper foil I without an oxide layer;

[0017] b. Prepare copper pyrophosphate electrolyte II;

[0018] c. Using microporous copper foil I as cathode and iridium-plated titanium plate III as anode, pulse electroplating is performed in electrolyte II;

[0019] d. After completing the pulse electrochemical treatment, the microporous copper foil is cleaned and dried to further remove surface residues.

[0020] The composition and concentration range of the copper pyrophosphate electrolyte II are as follows: the concentration range of copper pyrophosphate Cu2P2O7 is 20-50g / L, the concentration range of potassium pyrophosphate K4P2O7 is 250-300g / L, the additive is one of 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, sodium polydisulfide propane sulfonate (SPS), and benzotriazole, and the concentration range is 0.005-0.3g / L, the temperature is room temperature, the electroplating method is pulse electroplating, and the negative pulse current density is -0.5 to -20A / dm 2 , positive pulse current density is 0~1A / dm 2, pulse period is 8-100ms, negative pulse duration: 2-15ms, positive pulse duration: 6-90ms.

[0021] In the above electrolyte II, Cu 2+ Provides the main salt, potassium pyrophosphate is a complexing agent, its role is to stabilize the complex, prevent precipitation, and improve the crystallization of the coating: Cu2P2O7+3K4P2O7=2K6[Cu(P2O7)2]. At the beginning of electroplating, copper ions need to get rid of the complex ions, and then combine with electrons at the electrode | electrolyte interface to be reduced. Due to the high stability of copper pyrophosphate complex ions, the process of removing the pyrophosphate complex consumes a lot of energy, and the reduction rate of copper ions is relatively slow, resulting in finer crystallization of the coating. A certain amount of free potassium pyrophosphate must be maintained in the electrolyte, its role is to make the complex more stable, prevent copper pyrophosphate precipitation, and improve the dispersion ability of the plating solution. Additives such as 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, benzotriazole, polydisulfide dipropane sulfonate and other small molecules can be adsorbed on the surface of the micropores, improve the distribution of current on the surface of the micropores, and thus achieve the purpose of modifying the morphology inside the pores.

[0022] When electroplating with direct current, a thick diffusion layer is formed at the interface between the cathode and the solution, which reduces the metal ion concentration on the cathode surface and produces concentration polarization, limiting the speed of electrodeposition. In pulse electroplating, due to the off / positive current time, the consumed metal ions diffuse and replenish near the cathode during this time. When the next on / negative current time comes, the metal ion concentration near the cathode is restored, so a higher current density can be used. The peak current of pulse electroplating can be much higher than the average current, which makes the formation speed of crystal seeds higher than the growth speed of crystals, making the coating crystallization refined.

[0023] The current density of the negative pulse current is much higher than that of the positive pulse current, ensuring that a fine, uniform and high-density copper coating is deposited on the surface of the microporous copper foil and inside the pores. This coating can effectively fill the tiny defects and gaps inside the micropores and enhance the overall mechanical properties of the copper foil. After the negative pulse current electroplating, a positive pulse current of lower intensity is applied. The role of the positive pulse current is to alleviate the concentration polarization phenomenon generated during the negative pulse current electroplating process and avoid the non-uniform deposition of the coating due to the concentration gradient. Due to the tip effect of the electric field, the positive pulse current can selectively dissolve the abnormal protrusions on the surface of the copper foil, eliminate the surface roughness, and improve the flatness of the copper foil surface, thereby reducing potential structural defects.

[0024]

[0025] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for enhancing the tensile strength and elongation of microporous copper foil, characterized in that: Microporous copper foil I was used as cathode and pulse electroplating was performed in electrolyte II; the temperature was room temperature and the negative pulse current density was -0.5 to -20 A / dm 2 , positive pulse current density is 0~1A / dm 2 , pulse period is 8-100ms, negative pulse duration is 2-15ms, positive pulse duration is 6-90ms; electrolyte II is copper pyrophosphate electrolyte containing additives; the composition and concentration range of the copper pyrophosphate electrolyte containing additives are as follows: copper pyrophosphate Cu2P2O7 concentration range is 20-50g / L, potassium pyrophosphate K4P2O7 concentration range is 250-300g / L, the additive is one of 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, sodium polydisulfide dipropane sulfonate (SPS), and benzotriazole, and the concentration range is 0.005-0.3g / L.

2. The method for enhancing the elongation of microporous copper foil according to claim 1, characterized in that: Iridium-coated titanium plate III serves as the anode.

3. The method for enhancing the elongation of microporous copper foil according to claim 1, characterized in that: The microporous copper foil I needs to be pretreated before electroplating. The oxide layer on the surface of the microporous copper foil is removed by using 10% dilute H2SO4, and then washed with pure water to obtain the microporous copper foil I without the oxide layer.

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