Method for enhancing elongation of microporous copper foil

Abstract

The invention relates to a method for enhancing the elongation of a microporous copper foil, which comprises the following steps of: electroplating in an electrolyte II by taking a microporous copper foil I as a cathode; the temperature is room temperature, and the electroplating current density is 0.5-5A / dm < 2 >; the electrolyte II is a copper pyrophosphate electrolyte containing an additive; the copper pyrophosphate electrolyte comprises the following components in concentration ranges: copper pyrophosphate Cu2P2O7 in concentration range of 30-50 g / L, potassium pyrophosphate K4P2O7 in concentration range of 250-300 g / L, an additive is one of benzotriazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole and sodium 3, 3 '-dithiodipropane sulfonate (SPS), and the concentration range of the additive is 0.001-0.5 g / L. According to the method, on the basis of an existing microporous copper foil, accurate reinforcement treatment is carried out on a pore part through an electrochemical post-treatment technology, and the overall thickness of the copper foil does not need to be increased.

Description

Technical Field

[0001] The invention relates to a method for enhancing the elongation of a microporous copper foil, and belongs 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 invention aims to solve the problem of low elongation of existing microporous copper foil. This patent provides an innovative method for improving the elongation of microporous copper foil. Based on the existing microporous copper foil, the pores are precisely reinforced by electrochemical post-treatment technology without increasing the overall thickness of the copper foil.

[0005] To achieve the above object, the technical scheme of the present invention is as follows: a method for enhancing the elongation of microporous copper foil, wherein microporous copper foil I is used as a cathode and electroplated in electrolyte II; the temperature is room temperature, and the electroplating current density is 0.5-5A / dm 2 ; Electrolyte II is a copper pyrophosphate electrolyte containing additives; the composition and concentration range of the copper pyrophosphate electrolyte are as follows: the concentration range of copper pyrophosphate Cu2P2O7 is 30-50g / L, the concentration range of potassium pyrophosphate K4P2O7 is 250-300g / L, and the additive is one of benzotriazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, and sodium polydisulfide dipropane sulfonate (SPS), and the concentration range is 0.001-0.5g / L.

[0006] In the above electrolyte II, Cu 2+ Provides the main salt, pyrophosphate ion (P2O7 4-) is a complexing agent. Excess pyrophosphate ions combine with copper ions to form copper pyrophosphate complex ions: Cu2P2O7+3K4P2O7=2K6[Cu(P2O7)2]. At the beginning of electroplating, copper ions need to get rid of 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 pyrophosphate complex consumes a lot of energy, and the reduction rate of copper ions is relatively slow, resulting in finer crystallization of the coating. If the copper content is too low, the deposition rate is low, the allowable working current density range is narrow, and the brightness and leveling of the coating are poor; if the copper content is too high, the cathode polarization effect decreases and the coating is rough. 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 benzotriazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, sodium poly(disulfide-bis(propylene disulfide)sulfonate) and other small molecules have electron-donating functional groups that can be adsorbed on the surface of the micropores, promoting the electroplating of copper ions inside the pores, thereby leading to an enhanced effect on the micropores.

[0007] The technical solution for further improving the device of the present invention is as follows:

[0008] Preferably, the iridium-plated titanium plate III serves as the anode.

[0009] Preferably, the microporous copper foil I needs to be pretreated before electroplating, using 5% 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.

[0010] Preferably, the electroplating is one of direct current electroplating, pulse electroplating, and linear sweep voltammetry.

[0011] This treatment process not only improves the elongation of microporous copper foil, but also ensures that its tensile strength remains at an ideal level, which is expected to optimize the overall performance of copper foil in battery manufacturing and use. The advantage of this technology is that by improving the existing copper foil manufacturing process, the problem of copper foil breakage caused by too low elongation can be effectively avoided. At the same time, it is expected to improve the production reliability and service life of the battery, meet the needs of large-cell batteries for high-performance current collectors, and provide strong support for the development of new battery technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Comparison of the morphology of the original microporous copper foil and the enhanced microporous copper foil; DETAILED DESCRIPTION

[0013] A method for enhancing the elongation of microporous copper foil, comprising the following steps:

[0014] a. Use 5% 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;

[0015] b. Prepare copper pyrophosphate electrolyte II containing additives;

[0016] c. Using microporous copper foil I as cathode and iridium-plated titanium plate III as anode, direct current electroplating is performed in electrolyte II;

[0017] d. After electroplating is completed, use pure water to clean the residual electrolyte on the surface and dry it.

[0018] The composition and concentration range of the copper pyrophosphate electrolyte II are as follows: the concentration range of copper pyrophosphate Cu2P2O7 is 30-50 g / L, the concentration range of potassium pyrophosphate K4P2O7 is 250-300 g / L, the additive is one of benzotriazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, and sodium polydisulfide propane sulfonate (SPS), the concentration range is 0.001-0.5 g / L, the temperature is room temperature, and the electroplating current density is 0.5-5 A / dm 2 .

[0019] In the above electrolyte II, Cu 2+ Provides the main salt, pyrophosphate ion (P2O7 4- ) is a complexing agent. Excess pyrophosphate ions combine with copper ions to form copper pyrophosphate complex ions: Cu2P2O7+3K4P2O7=2K6[Cu(P2O7)2]. At the beginning of electroplating, copper ions need to get rid of 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 pyrophosphate complex consumes a lot of energy, and the reduction rate of copper ions is relatively slow, resulting in finer crystallization of the coating. If the copper content is too low, the deposition rate is low, the allowable working current density range is narrow, and the brightness and leveling of the coating are poor; if the copper content is too high, the cathode polarization effect decreases and the coating is rough. 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 benzotriazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, sodium poly(disulfide-bis(propylene disulfide)sulfonate) and other small molecules have electron-donating functional groups that can be adsorbed on the surface of the micropores, promoting the electroplating of copper ions inside the pores, thereby leading to an enhanced effect on the micropores.

[0020] See the following table for comparative experimental data:

[0021]

[0022] 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 elongation of microporous copper foil, characterized in that: The microporous copper foil I is used as the cathode and electroplated in the electrolyte II; the temperature is room temperature and the electroplating current density is 0.5-5A / dm 2 ; Electrolyte II is a copper pyrophosphate electrolyte containing additives; the composition and concentration range of the copper pyrophosphate electrolyte are as follows: the concentration range of copper pyrophosphate Cu2P2O7 is 30-50g / L, the concentration range of potassium pyrophosphate K4P2O7 is 250-300g / L, and the additive is one of benzotriazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, and sodium polydisulfide dipropane sulfonate (SPS), and the concentration range is 0.001-0.5g / 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 5% dilute H2SO4, and then washed with pure water to obtain the microporous copper foil I without the oxide layer.

4. The method for enhancing the elongation of microporous copper foil according to claim 1, characterized in that: The electroplating method is one of direct current electroplating, pulse electroplating and linear sweep voltammetry.

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