Method for refining electrocoppering crystals

Abstract

The invention relates to the technical field of electro-coppering, in particular to a method for refining electro-coppering crystals. The preparation method specifically comprises the following steps that 1, copper serves as a target material, magnetron sputtering treatment is conducted on a base film, and a magnetron film is obtained; and 2, placing the magnetic control film in an electroplating solution containing 1-piperazine carboxamide and N, N-dimethyl dithiocarbonyl sodium propane sulfonate, and carrying out electroplating treatment on the magnetic control film by adopting pulse current to obtain the functional current collector. By adjusting the components of the electroplating liquid and combining the pulse electroplating technology, finer crystal grains are prepared in the electroplating process. The crystal grains are fine, so that the tensile strength in the MD / TD direction can be intuitively improved, the ductility is further improved, and the resistivity is reduced; meanwhile, the surface smoothness of the plating layer can be improved, so that the stability of the functional current collector is improved; finally, the service life and the safety performance of the battery are improved.

Description

Technical Field

[0001] The invention relates to the technical field of electroplating copper, in particular to a method for refining electroplating copper crystals. Background Art

[0002] With the rapid development of new energy and electronic technologies, battery performance, including cycle life, safety, and energy density, has become a top priority. The current collector, a crucial component of a battery, is used to collect the current generated by the battery's active materials to generate a larger current output. Its performance directly impacts battery cycle life, safety, and energy density.

[0003] Previously, copper foil and aluminum foil were mostly used as current collectors for the positive and negative electrodes in lithium batteries and sodium batteries. However, this type of current collector has high cost and quality, which is not conducive to controlling battery costs and improving energy density. Based on this, composite foils have begun to be used as current collectors, which have more obvious advantages than traditional foils. The functional current collector made of composite foil is usually a "sandwich" structure, with a polymer high molecular layer on the inner layer and metal conductive layers on both sides. Since the functional current collector has a thinner metal layer on the surface and a lighter polymer layer inside, it can greatly reduce the overall weight of the current collector, thereby increasing the energy density of the lithium-ion battery; at the same time, the thinner metal layer on the surface of the functional current collector is easier to disconnect than the current collector of traditional foil when the lithium-ion battery undergoes thermal runaway, thereby blocking the connection between the active material and the current collector, and preventing the thermal runaway of the lithium-ion battery from continuing.

[0004] While composite foil offers the advantages of low cost and light weight, the substantial heat generated during battery charge and discharge cycles causes the functional current collector to undergo volume changes and shrinkage. Currently, most functional current collectors utilize a water-based direct current copper plating process to thicken the copper layer. This process has limitations in tensile strength, elongation, and resistivity, hindering effective improvements in battery energy density and cycle life, and also posing serious safety risks.

[0005] In summary, in order to further enhance the stability of the functional current collector in the battery and improve the service life and related performance of the battery, the present invention will, based on the water electroplating process, refine the copper layer on the functional current collector by innovating the electroplating solution formula and electroplating process parameters, thereby improving the quality and performance of the electroplated copper layer and enhancing the stability of the functional current collector. Summary of the Invention

[0006] The object of the present invention is to provide a method for refining electroplated copper crystals to solve the problems raised in the prior art.

[0007] To achieve the above object, the present invention proposes the following technical solutions: A method for refining electroplated copper crystals comprises the following steps: Step 1: Using copper as a target, the base film is subjected to magnetron sputtering treatment to obtain a magnetron film; Step 2: placing the magnetron film in an electroplating solution containing 1-piperazinecarboxamide and sodium N,N-dimethyldithiocarbonylpropanesulfonate, and electroplating the magnetron film with a pulse current to obtain a functional current collector.

[0008] Furthermore, the electroplating solution includes the following concentration components: copper sulfate 100-130 g / L, sulfuric acid 100-160 g / L, hydrochloric acid 50-70 g / L, leveler 1-4 g / L, and brightener 1-4 g / L.

[0009] Furthermore, the electroplating solution also includes 1-piperazinecarboxamide and sodium N,N-dimethyldithiocarbonylpropanesulfonate, and the addition ratio of the two is (3~5):1; wherein the addition concentration of sodium N,N-dimethyldithiocarbonylpropanesulfonate is in the range of 11~16g / L.

[0010] Furthermore, the electroplating parameters of the pulse current are: the pulse current density is 10~30A / dm 2 , pulse width is 180~220ms, duty cycle is 40~50%, and electroplating time is 2~5min.

[0011] Furthermore, the sputtering parameters of the magnetron sputtering process are: vacuum degree is 1×10 -3 ~1×10 -4 Pa, target spacing is 80~150mm, working gas is argon, gas flow rate is 50~150sccm, pressure is 0.1~1Pa, sputtering power is 10~20KW, substrate temperature is 20~200℃, and pre-sputtering time is 2min.

[0012] Furthermore, the base film is PP or PET, and has a thickness of 3-5 μm.

[0013] Furthermore, the sputtering thickness of the copper layer of the magnetron film is 50-70 nm.

[0014] Furthermore, the electroplated copper layer has an electroplating thickness of 1-2 μm.

[0015] Compared with the prior art, the present invention has the following beneficial effects: In traditional electroplating processes, sodium N,N-dimethyldithiocarbonylpropane sulfonate is usually used as an additive for electroplating copper foil. It interacts with copper ions through sulfur-containing groups, and this effect is relatively simple. Compared with other additives, it has limited ability to change the deposition path of copper ions and inhibit grain growth, and it is difficult to fully control the growth direction and speed of grains, thereby limiting its effect on grain refinement. The present invention introduces 1-piperazinecarboxamide additives, and sodium N,N-dimethyldithiocarbonylpropane sulfonate synergistically adsorbs on the surface of metal crystals to form a more stable adsorption layer, which promotes the formation of copper nuclei while inhibiting grain growth, first forming island-shaped fine copper grain piles, and the island-shaped fine copper grain piles are continuously connected in series to form continuous wavy grain piles, and layers of fine and uniform ones are slowly superimposed to increase the hindrance to movement between copper grains and improve the bonding strength of the copper layer; Compared to traditional DC electroplating technology, this invention uses high-current, long-period pulse current to continuously interrupt the direction of grain growth during the metal deposition process, prompting the metal grains to continue to form but not grow. This allows copper ions to be more evenly deposited on the wavy surface of the copper grain pile, reducing the unevenness and roughness of the coating surface, thereby improving the flatness of the coating and helping to obtain a bright, flat, and uniform electroplated copper layer, avoiding defects such as pinholes and pitting. The present invention adjusts the composition of the electroplating solution and combines it with pulse electroplating technology. The two work together to make the microstructure of the coating more dense and uniform, reduce grain boundary defects and stress concentration phenomena, thereby improving the bonding force between the coating and the substrate, so that the electroplated copper layer can be more firmly attached to the substrate and less likely to peel off, thereby improving the tensile strength and elongation in the MD longitudinal direction, reducing the resistivity and other properties, improving the quality and reliability of the electroplated products, and further improving the stability of the functional current collector, ultimately achieving the purpose of improving the service life and safety performance of the battery. DETAILED DESCRIPTION

[0016] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0017] It should be noted that the purchasers of all raw materials involved in the present invention include, without any special restrictions, illustratively: In the following examples, 1-piperazinecarboxamide and sodium N,N-dimethyldithiocarbonylpropanesulfonate were purchased from Jingmen Dongxin Biotechnology Co., Ltd. Copper sulfate, sulfuric acid, and hydrochloric acid were purchased from Dongyouyue (Suzhou) Electronic Technology New Materials Co., Ltd. Leveling agent, model JRM310A, brightener, model JRM200B, were purchased from Suzhou Jerry Beautification Company, and the rest were purchased from the market.

[0018] Example 1: A method for refining electroplated copper crystals: Step 1: Preparation of magnetron film: (1) Target material preparation: Pure copper is surface treated to ensure that its surface is smooth and free of impurities before being used as a target material; (2) Use high vacuum winding magnetron sputtering equipment and set the parameters: vacuum degree is 1×10 -3 Pa, the target spacing is 100 mm, the working gas is argon, the gas flow rate is 100 sccm, the pressure is 0.5 Pa, the sputtering power is 10 KW, the substrate temperature is room temperature (25 ° C), the pre-sputtering time is 2 min, and the copper treated in (1) is used as the target material for magnetron sputtering. A 60 nm thick copper layer is sputtered on a 4 μm thick PP base film to obtain a magnetron film; Step 2: Preparation of functional current collector: (1) Preparation of electroplating solution: Add 1-piperazinecarboxamide and sodium N,N-dimethyldithiocarbonylpropanesulfonate to the copper electroplating tank (containing component concentrations: copper sulfate 100 g / L, sulfuric acid 120 g / L, hydrochloric acid 60 g / L, leveler 2.5 g / L, brightener 2.5 g / L, solvent is water), wherein the concentration of 1-piperazinecarboxamide is 56 g / L, and the concentration of sodium N,N-dimethyldithiocarbonylpropanesulfonate is 14 g / L; (2) At room temperature of 25°C, the magnetron film was placed in an electroplating solution and electroplated using a pulse electroplating technique to form a 1 μm thick copper layer on the magnetron film to obtain a functional current collector; wherein the electroplating parameters of the pulse current were set to: a pulse current density of 20 A / dm 2 , the pulse period is 200ms, the duty cycle is 45%, and the electroplating time is 3min.

[0019] Based on Example 1, Examples 2 to 5 and Comparative Examples 1 to 4 are provided as follows: Example 2: Example 2 is based on Example 1, with the following adjustments made: electroplating parameters, while other processes remain unchanged, specifically as follows: Step 2: Preparation of functional current collector: (2) At room temperature of 25°C, the magnetron film was placed in an electroplating solution and electroplated using a pulse electroplating technique to form a 1 μm thick copper layer on the magnetron film to obtain a functional current collector; wherein the electroplating parameters were set to: a pulse current density of 30 A / dm 2 , the pulse period is 200ms, the duty cycle is 45%, and the electroplating time is 3min.

[0020] Example 3: Example 3 is based on Example 1, with the following adjustments: electroplating parameters, other processes remain unchanged, specifically as follows: Step 2: Preparation of functional current collector: (2) At room temperature of 25°C, the magnetron film was placed in an electroplating solution and electroplated using a pulse electroplating technique to form a 1 μm thick copper layer on the magnetron film to obtain a functional current collector; wherein the electroplating parameters were set to: a pulse current density of 10 A / dm 2 , the pulse period is 200ms, the duty cycle is 45%, and the electroplating time is 3min.

[0021] Example 4: Example 4 is based on Example 1, with the following adjustments made: electroplating parameters, while other processes remain unchanged, specifically as follows: Step 2: Preparation of functional current collector: (2) At room temperature of 25°C, the magnetron film was placed in an electroplating solution and electroplated using a pulse electroplating technique to form a 1 μm thick copper layer on the magnetron film to obtain a functional current collector; wherein the electroplating parameters were set to: a pulse current density of 20 A / dm 2 , the pulse period is 220ms, the duty cycle is 45%, and the electroplating time is 3min.

[0022] Example 5: Example 5 is based on Example 1, with the following adjustments: electroplating parameters, other processes remain unchanged, specifically as follows: Step 2: Preparation of functional current collector: (2) At room temperature of 25°C, the magnetron film was placed in an electroplating solution and electroplated using a pulse electroplating technique to form a 1 μm thick copper layer on the magnetron film to obtain a functional current collector; wherein the electroplating parameters were set to: a pulse current density of 20 A / dm 2 , the pulse period is 180ms, the duty cycle is 45%, and the electroplating time is 3min.

[0023] Comparative Example 1: Comparative Example 1 is based on Example 1, with the following adjustments: DC electroplating technology is adopted, and other processes remain unchanged, as follows: Step 2: Preparation of functional current collector: (2) At room temperature of 25°C, the magnetron film is placed in an electroplating solution and electroplated using a direct current electroplating technique to obtain a functional current collector; wherein the electroplating parameters are set to: a current density of 3A / dm 2 , the electroplating time is 3min.

[0024] Comparative Example 2: Comparative Example 2 is based on Example 1, with the following adjustments: only 1-piperazinecarboxamide is added, and other processes remain unchanged, specifically as follows: Step 2: Preparation of functional current collector: (1) Preparation of electroplating solution: Add 1-piperazinecarboxamide to the copper electroplating tank (containing component concentrations: copper sulfate 100 g / L, sulfuric acid 120 g / L, hydrochloric acid 60 g / L, leveler 2.5 g / L, brightener 2.5 g / L, solvent is water). The mass concentration of 1-piperazinecarboxamide in the copper electroplating tank is 56 g / L.

[0025] Comparative Example 3: Comparative Example 3 is based on Example 1, with the following modifications: only sodium N,N-dimethyldithiocarbonylpropanesulfonate is added, and other processes remain unchanged, as follows: Step 2: Preparation of functional current collector: (1) Preparation of electroplating solution: Add sodium N,N-dimethyldithiocarbonylpropane sulfonate to the copper electroplating tank (containing component concentrations: copper sulfate 100g / L, sulfuric acid 120g / L, hydrochloric acid 60g / L, leveler 2.5g / L, brightener 2.5g / L, solvent is water). The mass concentration of sodium N,N-dimethyldithiocarbonylpropane sulfonate in the copper electroplating tank is 14g / L.

[0026] Comparative Example 4: Comparative Example 4 is based on Example 1, with the following adjustments: 1-piperazinecarboxamide and sodium N,N-dimethyldithiocarbonylpropanesulfonate are not added, and other processes remain unchanged, specifically: Step 2: Preparation of functional current collector: (1) At room temperature of 25°C, the magnetron film was placed in an electroplating solution (containing the following components: copper sulfate 100 g / L, sulfuric acid 120 g / L, hydrochloric acid 60 g / L, leveler 2.5 g / L, brightener 2.5 g / L, and water as solvent), and electroplated using pulse electroplating technology to form a 1 μm thick copper layer on the magnetron film to obtain a functional current collector; wherein the electroplating parameters were set as follows: pulse current density of 20 A / dm 2 , the pulse period is 200ms, the duty cycle is 45%, and the electroplating time is 3min.

[0027] Performance test: The tensile strength, elongation and square resistance tests were performed on the functional current collectors prepared in Examples 1 to 5 and Comparative Examples 1 to 4: 1. Tensile strength and elongation test: According to the standard of GB / T 1040.3-2006, samples are taken along the longitudinal direction of the functional current collector and the tensile strength and elongation are tested using a universal testing machine; 2. Square resistance test: Use a four-probe tester to perform square resistance test on the functional current collector.

[0028] The results of the above test items are shown in Table 1 below: Table 1

[0029] Analysis of results: From the data of Examples 1 to 5 and Comparative Examples 1 to 4 in Table 1 above, it can be seen that the present invention adjusts the composition of the electroplating solution and combines it with pulse electroplating technology, and the two synergistically produce finer and more uniform grains, thereby improving the quality of the electroplated copper layer. The prepared functional current collector has higher MD longitudinal tensile strength and elongation, and lower resistivity. When applied to batteries, it can greatly improve the service life and safety performance of the batteries.

[0030] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for refining electroplated copper crystals, characterized in that: The following steps are involved: Step 1: Using copper as a target, the base film is subjected to magnetron sputtering treatment to obtain a magnetron film; Step 2: placing the magnetron film in a plating solution and electroplating the magnetron film using a pulse current to obtain a functional current collector; The electroplating solution comprises 1-piperazinecarboxamide and sodium N,N-dimethyldithiocarbonylpropanesulfonate, and the addition ratio of the two is (3-5):1; wherein the addition concentration of sodium N,N-dimethyldithiocarbonylpropanesulfonate is in the range of 11-16 g / L; The electroplating parameters of the pulse current are: the pulse current density is 10~30A / dm 2 , the pulse period is 180~220ms, the duty cycle is 40~50%, and the electroplating time is 2~5min.

2. The method for refining electroplated copper crystals according to claim 1, wherein: The electroplating solution includes the following components in concentrations: 100-130 g / L copper sulfate, 100-160 g / L sulfuric acid, 50-70 g / L hydrochloric acid, 1-4 g / L leveler, and 1-4 g / L brightener.

3. The method for refining electroplated copper crystals according to claim 1, wherein: The sputtering parameters of the magnetron sputtering process are: vacuum degree is 1×10 -3 ~1×10 -4 Pa, target spacing is 80~150mm, working gas is argon, gas flow rate is 50~150sccm, pressure is 0.1~1Pa, sputtering power is 10~20KW, substrate temperature is 20~200℃, and pre-sputtering time is 2min.

4. The method for refining electroplated copper crystals according to claim 1, wherein: The sputtering thickness of the copper layer of the magnetron film is 50-70 nm.

5. The method for refining electroplated copper crystals according to claim 1, wherein: The base film is PP or PET, and has a thickness of 3-5 μm.

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