CN115295750B - A method for preparing carbon nanotube-doped electrolytic copper foil - Google Patents

Abstract

The present invention discloses a method for preparing carbon nanotube-doped electrolytic copper foil, comprising the following steps: (1) carbon nanotube purification treatment; (2) carbon nanotube sensitization treatment; (3) carbon nanotube activation treatment; (4) chemical deposition of copper on the surface of carbon nanotubes; (5) preparation of carbon nanotube-doped copper foil by electrodeposition. The present invention can keep the original structure of carbon nanotubes intact and efficiently remove impurities in carbon nanotubes; reduce the agglomeration of carbon nanotubes in electrolyte and copper foil; improve the migration rate of carbon nanotubes in electrolyte and the precipitation efficiency on cathode; the prepared copper foil has good mechanical properties and electrical properties.

Description

A method for preparing carbon nanotube-doped electrolytic copper foil

Technical Field

The invention relates to the technical field of electrolytic copper foil preparation, and in particular to a method for preparing electrolytic copper foil for carbon nanotube-doped lithium batteries.

Background Art

Electrolytic copper foil is an important material for manufacturing negative electrode current collectors, copper-clad laminates and printed circuit boards for lithium-ion batteries. In today's "dual carbon" era, new energy vehicles are booming, and the market demand for lithium batteries is increasing. As lithium batteries develop towards "high power, high energy storage, and light weight", the current market generally produces and uses 4-12 micron double-sided photoelectrolytic copper foil as a negative electrode current collector material for lithium batteries, and the thickness of electrolytic copper foil is getting thinner and thinner. Thinning will bring about problems such as uneven thickness of electrolytic copper foil and weakened mechanical properties: uneven thickness of copper foil affects the coating quality of negative electrode active materials, and local corrosion is prone to occur during the electrochemical reaction process, and the battery is easily punctured and exploded; copper foil has low tensile properties and elongation, and is prone to splitting during the rolling process or high-power rapid charging and discharging, affecting battery capacity, and even causing battery breakdown, combustion and explosion. It is of great significance to improve or seek new ultra-thin, high-performance, and high-capacitance electrolytic copper foil preparation processes.

The invention patent with application number CN201780026112.6 discloses an electrolytic copper foil for graphene synthesis and a method for preparing the graphene-doped electrolytic copper foil. By adding nickel to promote graphene synthesis, graphene can be evenly distributed on the surface of the copper foil. The thickness of the copper foil is 4-70 microns; the room temperature tensile strength is 45-70Kgf/ ^mm2 ; the high temperature tensile strength is 20-35Kgf/ ^mm2 .

The electrical properties of graphene are more than 100 times that of copper; the speed of electrons in graphene is more than 100 times faster than that of single-crystal silicon; the strength of graphene is 200 times greater than that of steel; the thermal conductivity of graphene is 2 times higher than that of diamond, which has the highest thermal conductivity; and the excellent elasticity of graphene means that it will not lose its electrical properties when stretched or bent. Carbon nanotubes are superior to graphene in terms of electrical conductivity, thermal conductivity, strength, toughness and stability. Carbon nanotubes can be regarded as a cylinder made of a hexagonal periodic arrangement of graphite sheets, with a tube diameter of about 100nm and an axial dimension of the micrometer order. It is a typical one-dimensional quantum material and is considered to be the most promising reinforcement material at present.

By utilizing the excellent electrical and mechanical properties of carbon nanotubes, as a reinforcing phase doping into electrolytic copper foil, the capacitance of electrolytic copper foil can be increased, the resistance of copper foil can be reduced, and the mechanical properties of copper foil can be increased. However, due to the low purity of carbon nanotubes themselves, they are easy to agglomerate and stratify in the electrolyte, have a low migration rate, and have low deposition and precipitation efficiency; and during the electrodeposition process, copper ions will preferentially nucleate and deposit on the surface of carbon nanotubes, which can easily cause problems such as uneven thickness of copper foil, which seriously restricts the application of carbon nanotubes in the field of electrolytic copper foil.

Summary of the invention

The purpose of the present invention is to provide a method for preparing carbon nanotube-doped electrolytic copper foil around the solution of the above bottleneck problem. On the one hand, impurities in carbon nanotubes are removed by a "purification" process. On the other hand, a "sensitization-activation-chemical plating" process is used to coat some nucleation points on the surface of carbon nanotubes to prevent the transitional deposition of copper ions on their surface; at the same time, metal ion complexes will be adsorbed on the surface of carbon nanotubes to improve the electrical migration rate and electrodeposition efficiency of carbon nanotubes.

To achieve the above object, the present invention is implemented through the following technical steps:

(1) Purification of carbon nanotubes: First, prepare a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid at a volume ratio of 1:3; then add 5-15 g/L of carbon nanotubes to the mixed acid solution; stir magnetically or oscillate ultrasonically at 50-80°C for 5-8 hours; filter, rinse with deionized water until neutral, and then vacuum dry or freeze-dry.

(2) Sensitization of carbon nanotubes. First, dilute concentrated hydrochloric acid with deionized water at a volume ratio of 1:15-20; then add 15-25 g/L _{of SnCl2} to the diluted hydrochloric acid solution and stir evenly; then add 5-10 g/L of purified carbon nanotubes to the above prepared solution; stir magnetically or ultrasonically at 50-60°C for 0.5-1h; filter, rinse with deionized water until neutral, and then vacuum dry or freeze-dry.

(3) Activation of carbon nanotubes. First, dilute concentrated hydrochloric acid with deionized water at a volume ratio of 1:20-25; then add 5-20 g/L _{of PdCl2} to the diluted hydrochloric acid solution and stir evenly; then add 5-10 g/L of sensitized carbon nanotubes to the above prepared solution; stir magnetically or ultrasonically at 50-60°C for 0.5-1h; filter, rinse with deionized water until neutral, and then vacuum dry or freeze-dry.

(4) Chemical deposition of copper on the surface of carbon nanotubes. Dissolve EDTA- _CuNa2 in deionized water at 13-50 g/L; then add NaOH at 15-20 g/L to control the pH value at 9-13; then add 0.5-3 g/L of activated carbon nanotubes to the above prepared solution; then add formaldehyde at 15-30 mL/L; first stir magnetically or ultrasonically oscillate for 2 min at 50-60 °C, then let stand for 3-5 min and stir for 1-2 min, the reaction time is 10-30 min; filter, rinse with deionized water until neutral, and then vacuum dry or freeze dry.

(5) Preparation of carbon nanotube-doped copper foil by electrodeposition. First, prepare an electrolyte solution: Cu ²⁺ concentration of 30-60 g/L; a mixture of SPS (sodium polydisulfide propane sulfonate) and MPS (sodium 3-mercapto-1-propane sulfonate) of 1-15 mg/L; chloride ions of 10-35 mg/L; concentrated sulfuric acid of 70-100 g/L. Then, add 25-200 mg/L of carbon nanotubes surface-modified in steps (1)-(4) to the above electrolyte solution, stir continuously at 60°C for 0.5-1 h, control the current density to 5-40 A/dm ² and start electrodeposition, and carbon nanotube-doped copper foil can be prepared on the cathode surface. Peel the copper foil from the cathode, perform surface anti-oxidation treatment, clean and dry.

Furthermore, in step (1), the carbon nanotubes are 10-12 g/L; the temperature is 60-70° C.; and the time is 5-6 h.

Furthermore, in step (2), SnCl ₂ is 18-23 g/L; carbon nanotubes are 5-7 g/L; and the time is 30-40 min.

Furthermore, in step (3), PdCl ₂ is 16-20 g/L; carbon nanotubes are 5-7 g/L; and the time is 30-40 min.

Furthermore, in step (4), the EDTA-CuNa ₂ is 22-32 g/L, the Cu ²⁺ concentration is 3-4.6 g/L; the carbon nanotubes are 1-1.5 g/L; the pH value is 10-11; and the time is 15-20 min.

Furthermore, in step (5), the concentration of Cu ²⁺ is 30-45 g/L; the SPS+MPS mixture is 5-10 mg/L; the chloride ion is 20-25 mg/L; the concentrated sulfuric acid is 70-80 g/L; the modified carbon nanotubes is 50-100 mg/L; and the current density is 5-25 A/dm ² .

The beneficial effects of the present invention are:

The present invention can keep the original structure of carbon nanotubes intact and efficiently remove impurities in carbon nanotubes; reduce the agglomeration of carbon nanotubes in electrolyte and copper foil; improve the migration rate of carbon nanotubes in electrolyte and the precipitation efficiency on the cathode; the prepared copper foil has good mechanical properties and electrical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a scanning electron microscope image of the copper foil obtained in Comparative Example 1; (a) carbon nanotube agglomeration phenomenon; (b) copper particles grow abnormally coarsely locally on the surface of carbon nanotubes;

FIG2 is a scanning electron microscope image of the copper foil obtained in Example 1; (a) and (b) are different regions;

FIG3 is a scanning electron microscope image of the copper foil obtained in Example 2; (a) and (b) are different regions.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with specific examples, which are only preferred embodiments of the present invention and are not intended to limit the present invention. Other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

The reagents described in the present invention are all commercially available products, wherein the carbon nanotubes are multi-walled carbon nanotubes with a purity greater than 95.0%; the purity of copper sulfate pentahydrate is not less than 99.9%; the purity of sodium hydroxide is not less than 96.0%; the purity of sodium copper ethylenediaminetetraacetate is not less than 99.0%, and the copper content is ≥14.5%; the purity of stannous chloride is not less than 98.0%; the purity of concentrated hydrochloric acid is 36.0-38.0%; the purity of palladium chloride is 99.0%; the purity of concentrated sulfuric acid is not less than 99.0%; the purity of concentrated nitric acid is not less than 65.0%. A pure titanium plate is used as a cathode, and a copper plate with a purity of 99.9% is used as an anode.

The ICP4562 method was used to measure the thickness of the copper foil, the ICP-TM-650 method was used to test the tensile strength and elongation of the copper foil, and the double-arm bridge method was used to measure the resistance of the copper foil.

Comparative Example 1:

The carbon nanotubes were not purified or surface treated. First, an electrolyte was prepared: 120g CuSO ₄ ·5H ₂ O, 200mg polyacrylic acid (3000), 55mg concentrated hydrochloric acid, and 70g concentrated sulfuric acid were added to deionized water and heated to dissolve, and finally calibrated to 1000mL; 200mg of the original carbon nanotubes were added to the above electrolyte, and after continuous stirring at 60°C for 1h, the current density was controlled to be 5A/dm ² to start electrodeposition, and a 12-micron thick copper foil was prepared. The copper foil was peeled off from the cathode, and the surface was treated with anti-oxidation, cleaned, and dried. The electron scanning electron microscope image of the obtained copper foil is shown in Figure 1.

Embodiment 1:

(1) Purification of carbon nanotubes: prepare 250 mL of a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:3; add 2.5 g of original carbon nanotubes to the mixed acid solution; stir magnetically at 60°C for 6 h; filter, rinse with deionized water until neutral, and then dry in vacuum.

(2) Sensitization of carbon nanotubes: dilute concentrated hydrochloric acid to 400 mL at a volume ratio of 1:20; add 8 g of _SnCl2 to the diluted hydrochloric acid solution and stir evenly; then add 2 g of purified carbon nanotubes to the above prepared solution; stir magnetically at 60°C for 0.5 h; filter, rinse with deionized water until neutral, and then vacuum dry.

(3) Activation of carbon nanotubes: dilute concentrated hydrochloric acid to 300 mL at a volume ratio of 1:20; add 6 g of _PdCl2 to the diluted hydrochloric acid solution and stir evenly; then add 1.5 g of sensitized carbon nanotubes to the above prepared solution; stir magnetically at 60°C for 0.5 h; filter, rinse with deionized water until neutral, and then vacuum dry.

(4) Chemical deposition of copper on the surface of carbon nanotubes: Dissolve 25 g of EDTA- _CuNa2 and 15 g of NaOH in 1000 mL of deionized water, and control the pH value to 10; add 1-1.3 g of activated carbon nanotubes to the above solution; then add 20 mL of formaldehyde; let stand for 3 min at 60°C and then stir magnetically for 2 min, with a reaction time of 15 min; filter, rinse with deionized water until neutral, and then dry in vacuum.

(5) Preparation of carbon nanotube-doped copper foil by electrodeposition. 120 g of CuSO ₄ ·5H ₂ O, 5 mg of SPS+MPS mixture, 55 mg of concentrated hydrochloric acid, and 70 g of concentrated sulfuric acid were added to deionized water and heated to dissolve, and finally calibrated to 1000 mL; 50 mg of carbon nanotubes surface-modified in steps (1)-(4) were added to the above electrolyte, and after continuous stirring at 60°C for 1 hour, the current density was controlled to be 5 A/dm ² to start electrodeposition to prepare 12 μm thick copper foil. The copper foil was peeled off from the cathode, and the surface was treated with anti-oxidation, cleaned, and dried. The electron scanning electron microscope image of the obtained copper foil is shown in Figure 2.

Embodiment 2:

(1) Purification of carbon nanotubes: prepare 200 mL of a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:3; add 3 g of original carbon nanotubes into the mixed acid solution; stir magnetically at 60°C for 8 h; filter, rinse with deionized water until neutral, and then vacuum dry.

(2) Sensitization of carbon nanotubes: dilute concentrated hydrochloric acid to 350 mL at a volume ratio of 1:20; add 8 g of _SnCl2 to the diluted hydrochloric acid solution and stir evenly; then add 2.5 g of purified carbon nanotubes to the above prepared solution; stir magnetically at 60°C for 40 min; filter, rinse with deionized water until neutral, and then vacuum dry.

(3) Activation of carbon nanotubes: dilute concentrated hydrochloric acid to 300 mL at a volume ratio of 1:20; add 6 g of _PdCl2 to the diluted hydrochloric acid solution and stir evenly; then add 2 g of sensitized carbon nanotubes to the above prepared solution; stir magnetically at 60°C for 40 min; filter, rinse with deionized water until neutral, and then vacuum dry.

(4) Chemical deposition of copper on the surface of carbon nanotubes: 30 g of EDTA- _CuNa2 and 20 g of NaOH were added to 1000 mL of deionized water to dissolve, and the pH value was controlled at 11; 1.5 g of activated carbon nanotubes were added to the above prepared solution; 20 mL of formaldehyde was added; the mixture was allowed to stand for 3 min at 60°C and then magnetically stirred for 2 min, with a reaction time of 20 min; the mixture was filtered, rinsed with deionized water until neutral, and then dried in vacuum.

(5) Preparation of carbon nanotube-doped copper foil by electrodeposition. 175 g of CuSO ₄ ·5H ₂ O, 10 mg of SPS+MPS mixture, 70 mg of concentrated hydrochloric acid, and 80 g of concentrated sulfuric acid were added to deionized water and heated to dissolve, and finally calibrated to 1000 mL; 100 mg of carbon nanotubes surface-modified in steps (1)-(4) were added to the above electrolyte, and after continuous stirring at 60°C for 1 hour, the current density was controlled to be 15 A/dm ² to start electrodeposition to prepare 9 μm thick copper foil. The copper foil was peeled off from the cathode, and the surface was treated with anti-oxidation, cleaned, and dried. The electron scanning electron microscope image of the obtained copper foil is shown in Figure 3.

From the data in Figures 1-3 and Table 1, it can be seen that the carbon nanotubes without surface modification are prone to agglomeration, and the copper particles on the local surface are coarse, resulting in uneven thickness distribution and increased roughness of the copper foil. The carbon nanotubes after surface modification are evenly dispersed in the copper foil, the copper particles on the surface of the carbon nanotubes are evenly deposited, the thickness of the copper foil is also uniform, the roughness also meets the product quality requirements, and the electrical and mechanical properties are improved to a certain extent.

Table 1 Performance indicators of three groups of samples

Claims (6)

1. A method for preparing a carbon nanotube doped electrolytic copper foil is characterized by comprising the following steps: the method comprises the following steps:

Step 1, purifying the carbon nano tube; firstly, preparing mixed acid liquor of concentrated nitric acid and concentrated sulfuric acid according to the volume ratio of 1:3; adding the carbon nano tube into the mixed acid solution according to the ratio of 5-15 g/L; magnetically stirring or ultrasonic oscillating at 50-80deg.C for 5-8 hr; filtering, washing with deionized water to neutrality, and vacuum drying or freeze drying;

Step 2, sensitization treatment of the carbon nano tube; firstly, diluting concentrated hydrochloric acid with deionized water according to the volume ratio of 1:15-20; adding SnCl ₂ into diluted hydrochloric acid solution according to 15-25g/L, and uniformly stirring; adding purified carbon nano tube into the prepared solution according to the ratio of 5-10 g/L; magnetically stirring or ultrasonic oscillating at 50-60deg.C for 0.5-1 hr; filtering, washing with deionized water to neutrality, and vacuum drying or freeze drying;

Step 3, activating the carbon nano tube; firstly, diluting concentrated hydrochloric acid with deionized water according to the volume ratio of 1:20-25; adding PdCl ₂ to 20g/L into the diluted hydrochloric acid solution, and uniformly stirring; adding the sensitized carbon nano tube into the prepared solution according to the ratio of 5-10 g/L; magnetically stirring or ultrasonic oscillating at 50-60deg.C for 0.5-1 hr; filtering, washing with deionized water to neutrality, and vacuum drying or freeze drying;

Step 4, chemically depositing copper on the surface of the carbon nano tube; adding EDTA-CuNa ₂ into deionized water according to 13-50g/L for dissolution; adding NaOH according to 15-20g/L, and controlling the PH value at 9-13; adding activated carbon nanotubes into the prepared solution according to the ratio of 0.5-3 g/L; adding formaldehyde according to 15-30 mL/L; magnetic stirring or ultrasonic oscillating for 2min at 50-60deg.C, standing for 3-5min, stirring for 1-2min, and reacting for 10-30min; filtering, washing with deionized water to neutrality, and vacuum drying or freeze drying;

Step 5, preparing a carbon nanotube doped copper foil by electrodeposition; firstly, preparing electrolyte: cu ²⁺ concentration is 30-60g/L; 1-15mg/L of a mixture of sodium polydithio-dipropyl sulfonate and sodium 3-mercapto-1-propane sulfonate; chloride ion 10-35mg/L; 70-100g/L of concentrated sulfuric acid; adding the carbon nano tube subjected to the surface modification in the step 1-4 into the electrolyte according to the ratio of 25-200mg/L, continuously stirring at 60 ℃ for 0.5-1h, and controlling the current density to be 5-40A/dm ² to start electrodeposition, so that the carbon nano tube doped copper foil can be prepared on the surface of the cathode; and stripping the copper foil from the cathode, performing surface oxidation prevention treatment, cleaning and drying.

2. The method for preparing a carbon nanotube doped electrolytic copper foil according to claim 1, wherein: in the step 1, the carbon nano tube is 10-12g/L; the temperature is 60-70 ℃; the time is 5-6h.

3. The method for preparing a carbon nanotube doped electrolytic copper foil according to claim 1, wherein: in the step 2, snCl ₂ is 18-23g/L; 5-7g/L of carbon nano tube; the time is 30-40min.

4. The method for preparing a carbon nanotube doped electrolytic copper foil according to claim 1, wherein: in the step 3, pdCl ₂ is 16-20g/L; 5-7g/L of carbon nano tube; the time is 30-40min.

5. The method for preparing a carbon nanotube doped electrolytic copper foil according to claim 1, wherein: in the step 4, EDTA-CuNa ₂ is 22-32g/L, and Cu ²⁺ is 3-4.6g/L; 1-1.5g/L of carbon nano tube; the PH value is 10-11; the time is 15-20min.

6. The method for preparing a carbon nanotube doped electrolytic copper foil according to claim 1, wherein: the concentration of Cu ²⁺ in the step 5 is 30-45g/L; the mixture of the polydithio-dipropyl sodium sulfonate and the 3-mercapto-1-propane sodium sulfonate is 5-10mg/L; 20-25mg/L of chloride ions; 70-80g/L of concentrated sulfuric acid; 50-100mg/L of modified carbon nano tube; the current density is 5-25A/dm ².