Y-shaped branched carbon nanotube electrode material

Abstract

A carbon nanotube electrode material with a Y-shaped branch structure has an average diameter of 60nm, the carbon nanotube electrode material is of the Y-shaped branch structure, continuous bamboo-like capsule structure channels are formed in a carbon nanotube, and the carbon nanotube is prepared by dissolving an imidazole aqueous solution, a urea aqueous solution and a ferrocene aqueous solution in an acetonitrile aqueous solution to prepare a precursor solution; the precursor solution is heated and converted into boil-off gas, the precursor solution boil-off gas is conveyed to the surface of a heated silicon wafer through mixed gas of H2 and NH3 for growth, and washing and drying are conducted after growth is finished. The unique structure of the prepared Y-type branched carbon nanotube material can be used as a sodium ion storage space, the branched structure is beneficial to rapid transmission of ions and charges, when the Y-type branched carbon nanotube material is used as a sodium ion battery positive electrode material, the reversible capacity is 416 mAh g <-1 > when the current density is 100 mAh g <-1 >, and the Y-type branched carbon nanotube material has excellent rate capacity of 257 mAh g <-1 > when the current density is 2 A g <-1 >. And the reversible charge-discharge cycle number exceeds 4500.

Description

[0001] This invention is a divisional application of patent application number "202310057655.1", and the invention name is "A branched structure porous carbon nanotube material and its preparation method". Technical Field

[0002] The present invention relates to the technical field of carbon nanotube material preparation, and in particular to a Y-shaped branched carbon nanotube electrode material. Background Art

[0003] Sodium-ion batteries (SIBs) have attracted extensive research interest due to their low price, abundant reserves, and physical and chemical properties similar to lithium. + The large diameter (1.02 Å) leads to severe volume changes and slow diffusion kinetics, which directly impairs the Na + Storage and transportation. It is reported that the insertion of Na + The minimum interlayer spacing of the graphite-based anode material is at least 0.37 nm. However, the interlayer distance of conventional graphite-based anode materials is less than 0.37 nm, which cannot provide an ideal interlayer spacing to accommodate Na + Insertion and deintercalation lead to the Na + Poor storage performance. Some other conversion materials, including metal oxides / sulfides and alloys, usually exhibit poor cycling stability and rate characteristics due to their inherent low conductivity and large volume expansion during cycling, which makes them far away from the practical application of SIBs.

[0004] Extensive research has been conducted in this field to explore new carbon anodes with extended interlayer distances, edge-enriched nitrogen doping, and highly connected mesoporous structures. It is reported that highly interconnected mesoporous structures can expose more active surface sites to the electrolyte and shorten the diffusion distance of ions. For example, in the article "Bamboo-Like Nitrogen-Doped Carbon Nanotube Forests as Durable Metal-Free Catalysts for Self-Powered Flexible Li–CO2 Batteries" published by Xuelian Li et al., bamboo-like carbon nanotubes were prepared. However, the disordered zigzag channels limited the effective adsorption of sodium ions, resulting in low capacity. Therefore, designing suitable anode materials for SIBs remains a huge challenge. Summary of the Invention

[0005] The present invention aims to provide a bamboo-shaped porous carbon nanotube electrode material with a Y-shaped branch structure.

[0006] Another object of the present invention is to provide a method for preparing the bamboo-shaped porous carbon nanotube material with a Y-shaped branch structure. The prepared carbon nanotubes have a unique branch structure and bamboo-shaped continuous pore distribution, which makes the material have excellent Na + Storage performance.

[0007] The purpose of the present invention is achieved through the following technical solutions: A carbon nanotube electrode material with a Y-shaped branch structure is characterized in that: the average diameter of the carbon nanotubes is 60nm, presenting a Y-shaped bifurcated structure, and the interior of the carbon nanotubes has continuous bamboo-shaped capsule structure channels. The carbon nanotube material is prepared by dissolving an imidazole aqueous solution, a urea aqueous solution, and a ferrocene aqueous solution in an acetonitrile aqueous solution to prepare a precursor solution, heating a silicon wafer as a substrate, and heating the precursor solution to convert it into evaporated gas. The precursor evaporated gas is transported to the heated silicon wafer surface with a mixed gas of H2 and NH3 for growth, and then washed and dried to obtain the carbon nanotube material.

[0008] Furthermore, the concentration of the imidazole aqueous solution is 0.35 mol / L, the concentration of the urea aqueous solution is 0.15 mol / L, the concentration of the ferrocene aqueous solution is 0.5 mol / L, and the concentration of the acetonitrile aqueous solution is 50 mol / L.

[0009] Furthermore, the volume ratio of the above-mentioned imidazole aqueous solution, urea aqueous solution, ferrocene aqueous solution and acetonitrile aqueous solution is 1:0.5-0.8:0.1-0.15:10-20.

[0010] Furthermore, the heat treatment of the silicon wafer is to place the silicon wafer in a tube furnace, heat it to 550~650℃ at 10℃ / min, and then continue to heat it to 950~1050℃ at 5℃ / min, and then introduce a mixed gas of H2, NH3 and Ar until the temperature stabilizes. The volume ratio of H2, NH3 and Ar is 1:1:8.

[0011] Furthermore, when the temperature in the tube furnace stabilizes, the precursor is heated and converted into vapor gas, and a mixed gas of H2 and NH3 in a volume ratio of 1:1 is formed and transported to the surface of the silicon wafer in the tube furnace for growth for 12-10 minutes.

[0012] Furthermore, the product after the growth was washed with hydrochloric acid solution, acetone, deionized water and anhydrous ethanol in sequence, and then dried at 80° C. for 3 h.

[0013] In the present invention, imidazole and urea are used as composite carbon sources, ferrocene is mainly used as a catalyst, and multiple carbon sources, nitrogen sources and the introduced mixed gas change the catalyst active sites during the reaction, thereby changing the growth direction of the carbon nanotubes to form a Y-shaped branch structure, and forming a continuous bamboo capsule structure channel inside the carbon nanotubes, which is Na +The branched structure provides a large space for storage, while the branched structure is conducive to the rapid transmission of ions and charges, making the material have fast charging performance and excellent cycle stability when used as the anode material of sodium ion batteries.

[0014] A method for preparing a porous carbon nanotube material with a branched structure is characterized by: dissolving an imidazole aqueous solution, a urea aqueous solution, and a ferrocene aqueous solution in an acetonitrile aqueous solution to prepare a precursor solution, performing heat treatment on a silicon wafer as a substrate, and heating the precursor solution to convert it into evaporated gas. The precursor evaporated gas is transported to the heated silicon wafer surface with a mixed gas of H2 and NH3 for growth, and then washed and dried after completion.

[0015] Furthermore, the concentration of the imidazole aqueous solution is 0.35 mol / L, the concentration of the urea aqueous solution is 0.15 mol / L, the concentration of the ferrocene aqueous solution is 0.5 mol / L, and the concentration of the acetonitrile aqueous solution is 50 mol / L.

[0016] Furthermore, the volume ratio of the above-mentioned imidazole aqueous solution, urea aqueous solution, ferrocene aqueous solution and acetonitrile aqueous solution is 1:0.5-0.8:0.1-0.15:10-20.

[0017] Furthermore, the heat treatment of the silicon wafer is to place the silicon wafer in a tube furnace, heat it to 550~650℃ at 10℃ / min, and then continue to heat it to 950~1050℃ at 5℃ / min. During this process, a mixed gas of H2, NH3 and Ar is continuously introduced until the temperature stabilizes.

[0018] Furthermore, the volume ratio of the above H2, NH3 and Ar is 1:1:8.

[0019] Furthermore, when the temperature in the tube furnace stabilizes, the precursor is heated and converted into vapor gas, and a mixed gas of H2 and NH3 in a volume ratio of 1:1 is formed and transported to the surface of the silicon wafer in the tube furnace for growth for 12-10 minutes.

[0020] Furthermore, the product after the growth was washed with hydrochloric acid solution, acetone, deionized water and anhydrous ethanol in sequence, and then dried at 80° C. for 3 h.

[0021] Furthermore, a method for preparing a porous carbon nanotube material with a branched structure is characterized by the following steps: Step 1: Prepare the precursor solution Adding an imidazole aqueous solution, a urea aqueous solution and a ferrocene aqueous solution to an acetonitrile aqueous solution and stirring at 100-200 rpm for 15 min to obtain a precursor solution; the concentration of the imidazole aqueous solution is 0.35 mol / L, the concentration of the urea aqueous solution is 0.15 mol / L, the concentration of the ferrocene aqueous solution is 0.5 mol / L, the concentration of the acetonitrile aqueous solution is 50 mol / L, and the volume ratio of the imidazole aqueous solution, the urea aqueous solution, the ferrocene aqueous solution and the acetonitrile aqueous solution is 1:0.5-0.8:0.1-0.15:10-20; Step 2: High temperature growth of carbon nanotubes (1) Wash the silicon wafer with acetone and ethanol for 5 minutes respectively, and dry it at 80℃ for 30 minutes. Then fix the silicon wafer in a quartz boat and place the quartz boat in the central heating zone of the tube furnace; (2) First, raise the temperature of the tube furnace to 550-650°C at a rate of 10°C / min, and then continue to raise the temperature to 950-1050°C at a rate of 5°C / min. During this process, a mixed gas of H2, NH3, and Ar is continuously introduced until the temperature stabilizes; (3) The precursor solution is heated and converted into evaporated gas, and the evaporated gas of the precursor mixed solution is transported by a mixed gas of H2 and NH3 with a volume ratio of 1:1 into the tube furnace, and the product begins to grow on the surface of the silicon wafer in the tube furnace. The growth time is 12-20 minutes; (4) The obtained product was washed several times with hydrochloric acid solution, isopropyl alcohol, acetone, deionized water, and anhydrous ethanol, and then dried at 80 °C for 3 h and collected.

[0022] The present invention has the following technical effects: The porous carbon nanotube material with a bamboo-like branched structure prepared in the present invention has an outer diameter of about 60 nanometers and a bamboo-like capsule structure inside. This unique structure can serve as a sodium ion storage space, and its branched structure is conducive to the rapid transmission of ions and charges. When used as a positive electrode material for sodium ion batteries, it can achieve a high current density of 100 mAh g -1 The reversible capacity is 416 mAh g -1 , at a current density of 2 A g -1 Excellent rate capacity of 257 mAh g -1 , and has more than 4500 reversible charge and discharge cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : Schematic diagram of the structure of the porous carbon nanotube material with a bamboo-like branched structure prepared by the present invention.

[0024] Figure 2 : Scanning electron microscope image of the porous carbon nanotube material with bamboo-like branched structure prepared by the present invention.

[0025] Figure 3 : Transmission electron micrographs of the porous carbon nanotube material with a bamboo-like branched structure prepared in the present invention and the porous carbon nanotube prepared in Comparative Example 1.

[0026] Figure 4 : Raman image of the porous carbon nanotube material with bamboo-like branched structure prepared by the present invention.

[0027] Figure 5 : Pore size distribution diagram of the porous carbon nanotube material with bamboo-like branched structure prepared by the present invention.

[0028] Figure 6 : A battery capacity-cycle performance comparison chart of the porous carbon nanotube material with a bamboo-like branched structure prepared in the present invention and the solid carbon nanofiber prepared in Comparative Example 1 at a current density of 1 A / g.

[0029] Figure 7 : The porous carbon nanotube material with a bamboo-like branched structure prepared by the present invention is used as a positive electrode material for sodium ion batteries. DETAILED DESCRIPTION

[0030] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-mentioned contents of the present invention.

[0031] Example 1 A carbon nanotube electrode material with a Y-shaped branched structure is prepared according to the following steps: Step 1: Prepare the precursor solution Adding an imidazole aqueous solution, a urea aqueous solution, and a ferrocene aqueous solution to an acetonitrile aqueous solution and stirring at 100-200 rpm for 15 min to obtain a precursor solution; the concentration of the imidazole aqueous solution is 0.35 mol / L, the concentration of the urea aqueous solution is 0.15 mol / L, the concentration of the ferrocene aqueous solution is 0.5 mol / L, the concentration of the acetonitrile aqueous solution is 50 mol / L, and the volume ratio of the imidazole aqueous solution, the urea aqueous solution, the ferrocene aqueous solution, and the acetonitrile aqueous solution is 1:0.68:0.12:15; Step 2: High temperature growth of carbon nanotubes (1) Wash the silicon wafer with acetone and ethanol for 5 minutes respectively, and dry it at 80℃ for 30 minutes. Then fix the silicon wafer in a quartz boat and place the quartz boat in the central heating zone of the tube furnace; (2) First, the temperature of the tube furnace was raised to 600°C at a rate of 10°C / min, and then continued to be raised to 1000°C at a rate of 5°C / min. During this process, a mixed gas of H2, NH3, and Ar was continuously introduced until the temperature stabilized; (3) The precursor solution is heated and converted into evaporated gas, and the evaporated gas of the precursor mixed solution is transported by a mixed gas of H2 and NH3 with a volume ratio of 1:1 into the tube furnace, and the product begins to grow on the surface of the silicon wafer in the tube furnace for 15 minutes; (4) The obtained product was washed several times with hydrochloric acid solution, isopropyl alcohol, acetone, deionized water, and anhydrous ethanol, and then dried at 80 °C for 3 h and collected.

[0032] When the current density is 100 mAh g -1 The reversible capacity is 416 mAh g -1 , at a current density of 2 A g -1 Excellent rate capacity of 257 mAh g -1 , and has more than 4500 reversible charge and discharge cycles.

[0033] Figure 1 The morphology and structure of carbon nanotubes prepared by the present invention are shown in the scanning electron microscope image of the carbon nanotubes prepared by the present invention. Figure 2 As shown, Figure 3 (a) is its transmission electron microscope image, which clearly shows that it forms a Y-shaped branch structure, and the carbon nanotubes form a uniform and continuous bamboo capsule pore structure inside. Figure 1 The description is consistent.

[0034] The carbon nanotubes prepared in Example 1 were used as anode materials and the current density was 100 mAh g -1 When the rate capacity of the bamboo-shaped porous carbon nanotubes with branched structure prepared in Example 1 is 416 mAh g -1 , at a current density of 2 A g -1 Excellent rate capacity of 257 mAh g -1 , and has more than 4500 reversible charge and discharge cycles.

[0035] Comparative Example 1: Compared with Example 1, in Comparative Example 1, there is no urea in the precursor solution, and H2 and Ar are used as the mixed gas during temperature increase and introduction of the precursor solution evaporation gas, without using NH3.

[0036] like Figure 3As shown in (b), although the carbon nanotubes prepared in Comparative Example 1 also formed a bamboo-like continuous pore structure, the overall structure of the carbon nanotubes did not show bifurcation, the overall diameter was large, and the internal bamboo-like pore structure was poorly uniform and continuous, and the pore size structure was also not ideal. The carbon nanotubes prepared in Example 1 and Comparative Example 1 were used as anode materials, as shown in Figure 6 As shown in the figure, at a current density of 1 A / g, after 30 cycles, the rate capacities of the carbon nanotube anode materials corresponding to Example 1 and Comparative Example 1 were 368 mAh g -1 and 127mAh g -1 .

[0037] Example 2 A carbon nanotube electrode material with a Y-shaped branched structure is prepared according to the following steps: Step 1: Prepare the precursor solution Adding an imidazole aqueous solution, a urea aqueous solution, and a ferrocene aqueous solution to an acetonitrile aqueous solution and stirring at 150 rpm for 15 min to obtain a precursor solution; the concentration of the imidazole aqueous solution is 0.35 mol / L, the concentration of the urea aqueous solution is 0.15 mol / L, the concentration of the ferrocene aqueous solution is 0.5 mol / L, the concentration of the acetonitrile aqueous solution is 50 mol / L, and the volume ratio of the imidazole aqueous solution, the urea aqueous solution, the ferrocene aqueous solution, and the acetonitrile aqueous solution is 1:0.5:0.1:10; Step 2: High temperature growth of carbon nanotubes (1) Wash the silicon wafer with acetone and ethanol for 5 minutes respectively, and dry it at 80℃ for 30 minutes. Then fix the silicon wafer in a quartz boat and place the quartz boat in the central heating zone of the tube furnace; (2) First, the temperature of the tube furnace was raised to 550°C at a rate of 10°C / min, and then continued to be raised to 1050°C at a rate of 5°C / min. During this process, a mixed gas of H2, NH3, and Ar was continuously introduced until the temperature stabilized; (3) The precursor solution is heated and converted into evaporated gas, and the evaporated gas of the precursor mixed solution is transported by a mixed gas of H2 and NH3 with a volume ratio of 1:1 into the tube furnace, and the product begins to grow on the surface of the silicon wafer in the tube furnace for 12 minutes; (4) The obtained product was washed several times with hydrochloric acid solution, isopropyl alcohol, acetone, deionized water, and anhydrous ethanol, and then dried at 80 °C for 3 h and collected.

[0038] The carbon nanotubes prepared in Example 2 were used as anode materials and the current density was 100 mAh g -1 When the rate capacity of the bamboo-shaped porous carbon nanotubes with branched structure prepared in Example 2 is 419 mAh g -1 , at a current density of 2 A g -1Excellent rate capacity of 242 mAh g -1 , and has more than 4500 reversible charge and discharge cycles.

[0039] Example 3 A carbon nanotube electrode material with a Y-shaped branched structure is prepared according to the following steps: Step 1: Prepare the precursor solution The imidazole aqueous solution, the urea aqueous solution and the ferrocene aqueous solution were added to the acetonitrile aqueous solution and stirred at 100-200 rpm for 15 min to obtain a precursor solution; the concentration of the imidazole aqueous solution was 0.35 mol / L, the concentration of the urea aqueous solution was 0.15 mol / L, the concentration of the ferrocene aqueous solution was 0.5 mol / L, the concentration of the acetonitrile aqueous solution was 50 mol / L, and the volume ratio of the imidazole aqueous solution, the urea aqueous solution, the ferrocene aqueous solution and the acetonitrile aqueous solution was 1: 0.8: 0.15:20; Step 2: High temperature growth of carbon nanotubes (1) Wash the silicon wafer with acetone and ethanol for 5 minutes respectively, and dry it at 80℃ for 30 minutes. Then fix the silicon wafer in a quartz boat and place the quartz boat in the central heating zone of the tube furnace; (2) First, the temperature of the tube furnace was raised to 650°C at a rate of 10°C / min, and then continued to be raised to 950°C at a rate of 5°C / min. During this process, a mixed gas of H2, NH3, and Ar was continuously introduced until the temperature stabilized; (3) The precursor solution is heated and converted into evaporated gas, and the evaporated gas of the precursor mixed solution is transported by a mixed gas of H2 and NH3 with a volume ratio of 1:1 into the tube furnace, and the product begins to grow on the surface of the silicon wafer in the tube furnace for 20 minutes; (4) The obtained product was washed several times with hydrochloric acid solution, isopropyl alcohol, acetone, deionized water, and anhydrous ethanol, and then dried at 80 °C for 3 h and collected.

[0040] The carbon nanotubes prepared in Example 3 were used as anode materials and the current density was 100 mA g -1 When the rate capacity of the bamboo-shaped porous carbon nanotubes with branched structure prepared in Example 3 is 409 mAh g -1 , at a current density of 2 Ag -1 Excellent rate capacity of 253 mAh g -1 , and has more than 4500 reversible charge and discharge cycles.

Claims

1. A carbon nanotube electrode material having a Y-shaped branched structure, characterized in that: The carbon nanotubes have an average diameter of 60 nm and a Y-shaped bifurcated structure. The interior of the carbon nanotubes has continuous bamboo-shaped capsule structures. The carbon nanotubes are prepared by dissolving an imidazole aqueous solution, a urea aqueous solution, and a ferrocene aqueous solution in an acetonitrile aqueous solution to prepare a precursor solution. A silicon wafer is used as a substrate for heat treatment, and the precursor solution is heated to convert it into evaporated gas. The precursor evaporated gas is transported to the heated silicon wafer surface with a mixed gas of H2 and NH3 for growth, and then washed and dried to obtain the carbon nanotubes.

2. The carbon nanotube electrode material having a Y-shaped branch structure according to claim 1, wherein: The concentration of the imidazole aqueous solution is 0.35 mol / L, the concentration of the urea aqueous solution is 0.15 mol / L, the concentration of the ferrocene aqueous solution is 0.5 mol / L, and the concentration of the acetonitrile aqueous solution is 50 mol / L.

3. The carbon nanotube electrode material having a Y-shaped branch structure according to claim 1 or 2, characterized in that: The volume ratio of the imidazole aqueous solution, the urea aqueous solution, the ferrocene aqueous solution and the acetonitrile aqueous solution is 1:0.5-0.8:0.1-0.15:10-20.

4. A carbon nanotube electrode material having a Y-shaped branch structure according to any one of claims 1 to 3, characterized in that: The heat treatment of silicon wafers is to place the silicon wafers in a tube furnace, heat it to 550~650℃ at 10℃ / min, and then continue to heat it to 950~1050℃ at 5℃ / min, and then introduce a mixed gas of H2, NH3 and Ar until the temperature stabilizes.

5. The carbon nanotube electrode material having a Y-shaped branch structure according to claim 4, wherein: The volume ratio of the above H2, NH3 and Ar is 1:1:

8.

6. The carbon nanotube electrode material having a Y-shaped branch structure according to claim 4 or 5, characterized in that: When the temperature in the tube furnace stabilizes, the precursor is heated and converted into evaporated gas, and a mixed gas of H2 and NH3 is formed in a volume ratio of 1:1 and the evaporated gas is transported to the surface of the silicon wafer in the tube furnace for growth for 12-10 minutes.

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