Preparation method of foamy copper current collector with dense carbon nanotubes growing on surface

Abstract

The invention relates to a preparation method of a foamy copper current collector with dense carbon nanotubes growing on the surface, which comprises the following steps: firstly loading polyethyleneimine on the surface of foamy copper, then loading oleate on the polyethyleneimine, then carrying out in-situ pyrolysis to obtain foamy copper with nanocrystalline superlattices loaded on the surface, and finally growing the ultra-dense carbon nanotubes through a chemical vapor deposition process to obtain the foamy copper current collector with the dense carbon nanotubes growing on the surface. And preparing the foamy copper current collector with dense carbon nanotubes growing on the surface. Nanocrystalline superlattices generated by in-situ pyrolysis of oleate are adopted as a catalyst for growth of carbon nanotubes, the surface of foamy copper is coated with polyethyleneimine for surface modification, and the nanocrystalline superlattices grow on the surface of foamy copper through in-situ pyrolysis of oleate by means of the property that polyethyleneimine is positively charged and can adsorb oleate with negative charges. And enabling the nanocrystalline superlattice to grow into densely distributed carbon nanotubes in situ through a chemical vapor deposition method. The lithium affinity of copper can be effectively improved, and a branched three-dimensional conductive network is constructed.

Description

Technical Field

[0001] The present invention belongs to the fields of nanomaterials and energy, and particularly relates to a method for preparing a foam copper current collector with densely grown carbon nanotubes on its surface, so as to realize the preparation of a dendrite-free lithium anode in a lithium metal battery. Background Art

[0002] Lithium metal is regarded as an ideal anode material for next-generation high-energy-density batteries due to its extremely high theoretical specific capacity (3860 mAh / g) and the lowest electrode potential (-3.04 V vs. SHE). However, during the charge and discharge process, uneven deposition often occurs on the lithium metal anode, leading to the formation of lithium dendrites. These lithium dendrites may pierce the separator, trigger internal short circuits, cause battery failure, and even lead to safety accidents. In addition, the growth of lithium dendrites will damage the solid electrolyte interface (SEI) film, resulting in continuous consumption of the electrolyte, reducing the Coulomb efficiency, and accelerating capacity decay. Therefore, developing a dendrite-free lithium anode is crucial for improving the safety and cycle life of lithium metal batteries.

[0003] As a three-dimensional current collector, foam copper exhibits significant advantages in the application of dendrite-free lithium anodes. Its unique three-dimensional porous structure provides a high specific surface area and abundant pores, effectively reducing the local current density, evenly distributing the lithium ion flow, and inhibiting the formation of lithium dendrites. Compared with traditional two-dimensional copper foil current collectors, foam copper can better alleviate the volume change of lithium metal during charge and discharge, improving the cycle stability and safety of the battery. Therefore, the application of foam copper as a three-dimensional current collector in dendrite-free lithium anodes is one of the important research directions for improving the performance of lithium metal batteries. However, the lithium-phobic characteristic of copper affects its lithium loading ability, so the surface lithium-philic modification of foam copper is the key to the preparation of dendrite-free lithium anodes. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a foam copper current collector with densely grown carbon nanotubes on its surface.

[0005] A method for preparing a foam copper current collector with densely grown carbon nanotubes on its surface proposed by the present invention obtains foam copper with a surface-loaded nanocrystal superlattice through a thermal decomposition method, and then uses chemical vapor deposition to catalytically grow dense carbon nanotubes on it, completing the preparation of the foam copper current collector with densely grown carbon nanotubes on its surface. The specific steps are as follows:

[0006] (1) Dissolve 100 - 400 mg of polyethyleneimine in 2 - 8 mL of ethanol, immerse the foam copper in this solution, fish out the foam copper after ultrasonic treatment for 15 - 25 minutes, and dry it to obtain foam copper with surface-modified polyethyleneimine;

[0007] (2) Dissolve 50 - 200 mg of oleate in 1 - 4 mL of n - hexane. Using the thermal decomposition method, place the product obtained in step (1) into this solution, and after drying, obtain copper foam with oleate loaded on its surface.

[0008] (3) Using chemical vapor deposition, place the product obtained in step (2) into a tubular furnace, heat it at a heating rate of 2 °C / min to 450 °C, and hold for 2 hours to obtain copper foam with nanocrystalline superlattice loaded on its surface.

[0009] (4) Place the product obtained in step (3) downstream of the tubular furnace, place 1 g of carbon source upstream, heat it at a heating rate of 10 °C / min to 800 °C, hold for 2 hours, and then slowly cool down to obtain the required product.

[0010] In the present invention, the ratio of polyethyleneimine to ethanol in step (1) is 100 mg:2 mL.

[0011] In the present invention, the oleate cation in step (2) is one to three of iron, cobalt, or nickel.

[0012] In the present invention, the ratio of oleate to n - hexane in step (2) is 50 mg:2 mL.

[0013] In the present invention, during the process of heating to 450 °C in step (3), an inert atmosphere (N2 / Ar) is introduced.

[0014] In the present invention, the carbon source in step (4) is dicyandiamide.

[0015] In the present invention, during the process of heating to 800 °C in step (4), a H2 / Ar mixed atmosphere is introduced before 600 °C, and an inert atmosphere (N2 / Ar) is introduced after 700 °C.

[0016] The beneficial effects of the present invention are as follows: The present invention can effectively improve the lithium - repellent surface of copper foam, enhance the lithium - affinity of copper foam, simultaneously construct a more refined three - dimensional conductive network, and reduce the local current density. It can be used for the preparation of dendrite - free lithium anodes. The present invention in - situ grows densely distributed carbon nanotubes on the surface of copper foam by catalyzing nanocrystalline superlattices. Carbon nanotubes are a kind of lithium - affinity material. At the same time, the nanopores formed between the ultra - dense carbon nanotubes can use capillary action to infuse molten lithium into the three - dimensional framework of copper foam. Meanwhile, the branched carbon nanotubes provide a more abundant conductive network, which can further reduce the local current density and disperse the lithium ion flow. Description of the Drawings

[0017] Figure 1 It is the scanning electron microscope image of copper foam with densely grown carbon nanotubes on its surface prepared in Example 1 of the present invention.

[0018] Figure 2 This is the SEM image of the copper foam with densely grown carbon nanotubes on the surface prepared in Example 2 of the present invention.

[0019] Figure 3 For the copper foam with densely grown carbon nanotubes on the surface prepared in Example 2 of the present invention, a lithium-copper half-cell was prepared, and compared with a commercial copper foil, the Coulomb efficiency diagram of the lithium deposition / stripping process was tested.

[0020] Figure 4 This is the SEM image of the copper foam with densely grown carbon nanotubes on the surface prepared in Example 3 of the present invention.

[0021] Figure 5 For the copper foam with densely grown carbon nanotubes on the surface prepared in Example 3 of the present invention, as a lithium anode carrier, a lithium-sulfur full-cell was prepared, and compared with a commercial lithium sheet, the electrochemical impedance diagram was tested. Detailed implementation manners

[0022] Example 1:

[0023] (1) Take 100 mg of polyethyleneimine and dissolve it in 2 mL of ethanol. Immerse the copper foam in the solution, take it out after ultrasonic treatment for 20 minutes, and dry it to obtain copper foam with polyethyleneimine modified on the surface;

[0024] (2) Dissolve 50 mg of oleate in 1 mL of n-hexane. Place the product obtained in step (1) in this solution, and dry it to obtain copper foam with oleate loaded on the surface;

[0025] (3) Place the product obtained in step (2) in a tube furnace, introduce an inert atmosphere (N2 / Ar), and heat it to 450 °C at a heating rate of 2 °C / min and keep it for 2 hours to obtain copper foam with nanocrystalline superlattice loaded on the surface;

[0026] (4) Place the product obtained in step (3) at the downstream of the tube furnace, place 1 g of dicyandiamide as a carbon source at the upstream, and heat it to 800 °C at a heating rate of 10 °C / min. Among them: a mixed atmosphere of H2 / Ar is introduced before 600 °C, and an inert atmosphere of N2 / Ar is introduced after 700 °C. After keeping it for 2 hours, cool it down slowly.

[0027] Figure 1 This is the SEM image of the copper foam with densely grown carbon nanotubes on the surface prepared in Example 1 of the present invention. It can be seen that the surface of the copper foam has been completely coated with dense carbon nanotubes.

[0028] Example 2:

[0029] (1) Dissolve 200 mg of polyethyleneimine in 4 mL of ethanol, immerse the copper foam in the solution, fish it out after ultrasonic treatment for 20 minutes, and dry it to obtain copper foam with polyethyleneimine-modified surface;

[0030] (2) Dissolve 100 mg of oleate in 2 mL of n-hexane, place the product obtained in step (1) in this solution, and dry it to obtain copper foam with oleate loaded on the surface;

[0031] (3) Place the product obtained in step (2) in a tubular furnace, introduce an inert atmosphere (N2 / Ar), heat it to 450 °C at a heating rate of 2 °C / min and hold for 2 hours to obtain copper foam with nanocrystalline superlattice loaded on the surface;

[0032] (4) Place the product obtained in step (3) downstream of the tubular furnace, place 1 g of dicyandiamide as a carbon source upstream, heat it to 800 °C at a heating rate of 10 °C / min, where: a mixed atmosphere of H2 / Ar is introduced before 600 °C, and an inert atmosphere of N2 / Ar is introduced after 700 °C. After holding for 2 hours, cool it down slowly.

[0033] Figure 2 This is the scanning electron microscope image of the copper foam with densely grown carbon nanotubes on the surface prepared in Example 2 of the present invention. It can be seen that the growth of carbon nanotubes on the surface of the copper foam is very uniform.

[0034] Figure 3 This is the copper foam with densely grown carbon nanotubes on the surface prepared in Example 2 of the present invention. A lithium-copper half-cell is prepared and compared with a commercial copper foil to test the Coulomb efficiency diagram of the lithium deposition / stripping process. It can be seen that the present invention has a more stable Coulomb efficiency, which proves that the densely packed carbon nanotubes on the surface reduce the local current density, slow down the lithium loss caused by side reactions, and enhance the cycle stability.

[0035] Example 3:

[0036] (1) Dissolve 400 mg of polyethyleneimine in 8 mL of ethanol, immerse the copper foam in the solution, fish it out after ultrasonic treatment for 20 minutes, and dry it to obtain copper foam with polyethyleneimine-modified surface;

[0037] (2) Dissolve 200 mg of oleate in 4 mL of n-hexane, place the product obtained in step (1) in this solution, and dry it to obtain copper foam with oleate loaded on the surface;

[0038] (3) Place the product obtained in step (2) in a tubular furnace, introduce an inert atmosphere (N2 / Ar), heat it to 450 °C at a heating rate of 2 °C / min and hold for 2 hours to obtain copper foam with nanocrystalline superlattice loaded on the surface;

[0039] (4) Place the product obtained in step (3) downstream of the tubular furnace, place 1 g of dicyandiamide as a carbon source upstream, and heat it to 800 °C at a heating rate of 10 °C / min. Among them, a mixed atmosphere of H2 / Ar is introduced before 600 °C, and an inert atmosphere of N2 / Ar is introduced after 700 °C. After maintaining for 2 hours, cool it slowly.

[0040] Figure 4 This is the scanning electron microscope image of the copper foam with densely grown carbon nanotubes on the surface prepared in Example 3 of the present invention. It can be seen that there are pores between the carbon nanotubes, which is the key to capillary action for adsorbing molten lithium. At the same time, it can be observed that the carbon nanotubes form a conductive network on the surface of the copper foam.

[0041] Figure 5 This is the copper foam with densely grown carbon nanotubes on the surface prepared in Example 3 of the present invention. As a lithium negative electrode carrier for preparing a lithium-sulfur full battery, its electrochemical impedance diagram is tested in comparison with a commercial lithium sheet. It can be seen that the arc radius in the Nyquist diagram becomes smaller and the interface resistance decreases, proving that the rich conductive network makes the charge transfer and current distribution in the electrode more uniform.

Claims

1. A method for preparing a foam copper current collector with densely grown carbon nanotubes on its surface, characterized in that The specific steps are as follows: (1) 100-400 mg of polyethyleneimine is dissolved in 2-8 mL of ethanol, and the copper foam is immersed in the solution. After ultrasonic treatment for 15-25 minutes, the copper foam is removed and dried to obtain the copper foam with the polyethyleneimine surface modified; (2) dissolving 50-200 mg of oleate in 1-4 mL of n-hexane, placing the product obtained in step (1) in the solution by thermal decomposition, and drying to obtain a copper foam with oleate loaded on the surface; (3) using a chemical vapor deposition method, placing the product obtained in step (2) in a tube furnace, heating it to 450° C. at a heating rate of 2° C. / min and keeping it at that temperature for 2 hours, to obtain a foam copper having a nanocrystalline superlattice loaded on its surface; (4) The product obtained in step (3) is placed downstream of a tubular furnace, and 1 g of a carbon source is placed upstream. The temperature is raised to 800°C at a heating rate of 10°C / min, maintained for 2 hours, and then slowly cooled to obtain the desired product.

2. The method for preparing a foam copper current collector with densely grown carbon nanotubes on the surface according to claim 1, characterized in that In step (1), the ratio of polyethyleneimine to ethanol is 100 mg: 2 mL.

3. The method for preparing a foam copper current collector with densely grown carbon nanotubes on the surface according to claim 1, characterized in that The oleate cations in step (2) are one to three of iron, cobalt or nickel.

4. The method for preparing a foam copper current collector with densely grown carbon nanotubes on the surface according to claim 1, characterized in that In step (2), the ratio of oleate to n-hexane is 50 mg: 2 mL.

5. The method for preparing a foam copper current collector with densely grown carbon nanotubes on the surface according to claim 1, characterized in that During the process of heating to 450° C. in step (3), an inert N 2 / Ar atmosphere is introduced.

6. The method for preparing a foam copper current collector with densely grown carbon nanotubes on the surface according to claim 1, characterized in that The carbon source described in step (4) is dicyandiamide.

7. The method for preparing a foam copper current collector with densely grown carbon nanotubes on the surface according to claim 1, characterized in that During the heating process to 800°C in step (4), a H2 / Ar mixed atmosphere is introduced before 600°C, and a N2 / Ar inert atmosphere is introduced after 700°C.

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