A method for preparing a carbon nanotube-doped porous carbon composite material

Abstract

The application discloses a preparation method of a carbon nanotube doped porous carbon composite material, and at least comprises the following operation steps: S1, carbon nanotubes, Co-MOF-74 materials, polyacrylonitrile, an organic pore forming agent, an organic metal compound and a water-soluble carbon source are respectively added into a solvent to be uniformly mixed to obtain a mixed solution; S2, the mixed solution obtained in the step S1 is prepared into a multi-element doped carbon fiber composite material through electrostatic spinning; S3, a crosslinking agent mixed gas is passed into the multi-element doped carbon fiber composite material obtained in the step S2 to perform oxidation crosslinking, then the temperature is raised to not less than 850 DEG C, and carbon dioxide gas is passed in to perform activation treatment, so that the carbon nanotube doped porous carbon composite material is obtained; the carbon nanotube doped porous carbon composite material provided by the application can be applied as a silicon-carbon negative material of a lithium ion battery, so that the expansion can be obviously reduced, and the cycle performance of the applied battery can be improved.

Description

Technical Field

[0001] This invention belongs to the field of silicon-carbon anode materials, specifically relating to a method for preparing carbon nanotube-doped porous carbon composite materials. Background Technology

[0002] Porous carbon, as a precursor material for silicon-carbon anode materials, significantly influences the power, expansion, and cycling performance of silicon-carbon materials due to its pore volume, pore size, electronic conductivity, and compressive strength. Current methods for preparing porous carbon involve pre-carbonization, activation, and impurity removal of the precursor material, resulting in bulk and spherical structures that deviate from the material's power and cycling performance.

[0003] Therefore, the applicant hopes to find a technical solution to solve the above technical problems. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing carbon nanotube-doped porous carbon composite material, which can be used as a silicon-carbon anode material for lithium-ion batteries, and can significantly reduce expansion and improve the cycle performance of the battery.

[0005] The technical solution adopted in this invention is as follows: A method for preparing a carbon nanotube-doped porous carbon composite material includes at least the following steps: S1. Carbon nanotubes, Co-MOF-74 material, polyacrylonitrile, organic pore-forming agent, organometallic compound and water-soluble carbon source are added to solvent and mixed evenly to obtain a mixed solution; S2. The mixed solution obtained in step S1 above is used to prepare a multi-element doped carbon fiber composite material by electrospinning; S3. The multi-element doped carbon fiber composite material obtained in step S2 is oxidized and crosslinked by passing a crosslinking agent mixture gas through it, and then heated to not less than 850°C and activated by passing carbon dioxide gas through it to obtain the carbon nanotube doped porous carbon composite material. The carbon nanotube doped porous carbon composite material is preferably used as the silicon-carbon anode material for lithium batteries.

[0006] Preferably, in step S1, the mass ratio of carbon nanotubes, Co-MOF-74 material, polyacrylonitrile, organic pore-forming agent, organometallic compound and water-soluble carbon source is set to a range of 1-5:1-5:100:5-20:1-5:100-200; the mass ratio of carbon nanotubes to solvent is 1:1000-50000.

[0007] Preferably, in step S1, the organic pore-forming agent is any one or a mixture of several of polystyrene, polyethylene glycol, polyvinyl chloride, polyglycolic acid, carboxymethyl cellulose, and lignin; the organometallic compound is any one or a mixture of several of niobium ethoxide, niobium n-propoxide, niobium isopropoxide, titanium ethoxide, titanium n-propoxide, and titanium isopropoxide; the water-soluble carbon source is any one or a mixture of several of sodium acetate, citric acid, malic acid, tartaric acid, acetic acid, succinic acid, and oxalic acid; and the solvent is any one or a mixture of several of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and tetrahydrofuran (THF).

[0008] Preferably, in step S2, the electrospinning operating parameters are set as follows: static voltage range of 15-20KV, jetting speed range of 0.2-0.7ml / h, and receiving distance range of 10-20cm.

[0009] Preferably, in step S3, the flow rate of the crosslinking agent mixed gas is set to 100-500 ml / min; the working temperature of the oxidative crosslinking is set to 300-500℃, and the working time is set to 30-300 min.

[0010] Preferably, in step S3, the flow rate of carbon dioxide gas is set to 100-500 ml / min; wherein, the working temperature of the activation treatment is set to 900-1200℃, and the working time is set to 60-600 min.

[0011] Preferably, in step S3, the crosslinking agent mixed gas is a mixture of vaporized peroxide and nitrogen, wherein the volume ratio of vaporized peroxide to nitrogen is set to 1-5:10.

[0012] Preferably, the peroxide compound is any one or a mixture of several of peracetic acid, peroxyformic acid, butanone peroxide, benzoyl peroxide, diethyl peroxide, and tert-butanol peroxide.

[0013] Preferably, in step S1, the carbon nanotubes are prepared by the following method: a1. Place the magnesium and nickel mesh in a CVD high-temperature furnace and heat it to 700-1200℃ under an inert gas atmosphere; a2. Acetylene gas is introduced at a flow rate of 100-500 ml / min for 30-300 min, and carbon nanotube network is grown on the nickel mesh described in step a1; a3. The grown carbon nanotube network is washed and dried to obtain the carbon nanotubes.

[0014] Preferably, in step a1, the aperture of the nickel mesh is 0.5-2 mm; the distance between the magnesium metal and the nickel mesh is set to 1-5 cm.

[0015] The working mechanism and technical effects of this application are as follows: This application adds carbon nanotubes to polyacrylonitrile to improve the electronic conductivity of the material. At the same time, it utilizes the porous niobium oxide / titanium oxide obtained after carbonization of organometallic compounds, which has the characteristics of large interlayer spacing and high ion diffusion coefficient. Moreover, the Co-MOF-74 material expands the carbon layer during the carbonization process, improves the insertion and extraction rate during charge and discharge, and improves the rate performance. It gives full play to the synergistic effect between carbon nanotubes, organometallic oxides, and Co-MOF-74, thereby improving power performance and reducing expansion. In addition, this application first prepares multi-element doped carbon fiber composite material by electrospinning a raw material mixture solution. Then, it introduces a crosslinking agent mixture gas to perform oxidative crosslinking treatment on the multi-element doped carbon fiber composite material to form a structurally stable precursor. After that, carbon dioxide is introduced for activation. The resulting porous carbon composite material, when used as a silicon-carbon anode material for lithium-ion batteries, can significantly reduce expansion and improve the cycle performance of the applied battery. Attached Figure Description

[0016] Figure 1 This is a SEM image of the carbon nanotube-doped porous carbon composite material obtained in Example 1 of this application. Detailed Implementation

[0017] This embodiment proposes a method for preparing carbon nanotube-doped porous carbon composite materials, which includes at least the following steps: S1. Carbon nanotubes, Co-MOF-74 material, polyacrylonitrile, organic pore-forming agent, organometallic compound and water-soluble carbon source are added to solvent and mixed evenly to obtain a mixed solution; Preferably, in step S1, the carbon nanotubes are prepared as follows: a1. Place the magnesium metal and nickel mesh in a CVD high-temperature furnace and heat to 700-1200℃ under an inert gas atmosphere; wherein, preferably, the aperture of the nickel mesh is 0.5-2mm; the distance between the magnesium metal and the nickel mesh is set to 1-5cm, more preferably 1.5-3.5cm; a2. Acetylene gas is introduced at a flow rate of 100-500 ml / min for 30-300 min, and carbon nanotube network is grown on the nickel mesh in step a1; a3. The grown carbon nanotube network is washed and dried to obtain carbon nanotubes.

[0018] Preferably, in step S1, the mass ratio of carbon nanotubes, Co-MOF-74 material, polyacrylonitrile, organic pore-forming agent, organometallic compound and water-soluble carbon source is set to 1-5:1-5:100:5-20:1-5:100-200; the mass ratio of carbon nanotubes to solvent is 1:1000-50000.

[0019] Preferably, in step S1, the organic pore-forming agent is any one or a mixture of several of polystyrene, polyethylene glycol, polyvinyl chloride, polyglycolic acid, carboxymethyl cellulose, and lignin; the organometallic compound is any one or a mixture of several of niobium ethoxide, niobium n-propoxide, niobium isopropoxide, titanium ethoxide, titanium n-propoxide, and titanium isopropoxide; the water-soluble carbon source is any one or a mixture of several of sodium acetate, citric acid, malic acid, tartaric acid, acetic acid, succinic acid, and oxalic acid; and the solvent is any one or a mixture of several of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and tetrahydrofuran (THF).

[0020] S2. The mixed solution obtained in step S1 is used to prepare a multi-element doped carbon fiber composite material by electrospinning; preferably, in this step S2, the working parameters of electrospinning are set as follows: the electrostatic voltage range is 15-20KV, the spraying speed range is 0.2-0.7ml / h, and the receiving distance range is 10-20cm. S3. The multi-element doped carbon fiber composite material obtained in step S2 is oxidized and crosslinked by passing a crosslinking agent mixture gas through it, and then heated to not less than 850°C and activated by passing carbon dioxide gas through it to obtain carbon nanotube doped porous carbon composite material. The carbon nanotube doped porous carbon composite material is preferably used as the silicon-carbon anode material for lithium batteries. Preferably, in step S3, the flow rate of the crosslinking agent mixed gas is set to 100-500 ml / min; the working temperature of the oxidative crosslinking is set to 300-500℃, and the working time is set to 30-300 min; preferably, in step S3, the flow rate of the carbon dioxide gas is set to 100-500 ml / min; wherein, the working temperature of the activation treatment is set to 900-1200℃, and the working time is set to 60-600 min; the crosslinking agent mixed gas is: preferably, in step S3, it is a mixture of gasified peroxide and nitrogen, wherein the volume ratio of gasified peroxide to nitrogen is set to 1-5:10; preferably, the peroxide is any one or a mixture of several of peracetic acid, performic acid, methyl ethyl ketone peroxide, benzoyl peroxide, diethyl peroxide, and tert-butanol peroxide.

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0022] Based on the above-described implementation schemes, this application further proposes the following specific embodiments: It should be noted that, unless otherwise specified, the raw materials used in the following specific embodiments of the present invention are all commercially available products. The carbon nanotubes used in the following specific embodiments were all obtained using the preparation method described below: 100g of magnesium powder and a nickel mesh (1mm in diameter, i.e., the aperture of the nickel mesh) were placed in a CVD high-temperature furnace and heated to 1000℃ under argon protection, while maintaining a distance of 2cm between the magnesium powder and the nickel mesh. Then, acetylene gas was introduced at a flow rate of 300ml / min for 150min to grow a carbon nanotube network on the nickel mesh. The network was then washed with dilute hydrochloric acid and deionized water in sequence, and then vacuum dried at 80℃ for 24h to obtain the carbon nanotube network.

[0023] The Co-MOF-74 material involved in this application is a metal-organic framework material composed of cobalt ions (Co) and organic ligands (MOF), which is commercially available and is not specifically limited in this application. In the following specific embodiments of this application, the Co-MOF-74 material model used is CAS: 871458-67-2; manufacturer: Zhongke Leiming (Beijing) Technology Co., Ltd.

[0024] It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] Example 1: A method for preparing a carbon nanotube-doped porous carbon composite material, comprising the following steps: 3g of carbon nanotubes, 3g of Co-MOF-74 material, 100g of polyacrylonitrile, 10g of polystyrene, 3g of niobium ethoxide, and 150g of sodium acetate were added to 5400g of N,N-dimethylformamide solvent and mixed evenly to prepare a mixed solution. This mixed solution was then electrospun using electrostatic parameters of 20kV, a jetting speed of 0.5ml / min, and a receiving distance of 15cm to prepare a multi-element doped carbon fiber composite material. The temperature was then raised to 400℃, and a peracetic acid mixed gas (volume ratio: peracetic acid: nitrogen = 3:10) was introduced at a flow rate of 300ml / min for oxidative crosslinking treatment for 150min. Afterward, the temperature was raised to 1000℃, and carbon dioxide gas was introduced at a flow rate of 300ml / min for activation treatment for 300min, resulting in a carbon nanotube-doped porous carbon composite material. For the SEM image of the carbon nanotube-doped porous carbon composite material obtained in Example 1 of this application, please refer to [link to SEM image]. Figure 1 As shown.

[0026] Example 2: A method for preparing a carbon nanotube-doped porous carbon composite material, comprising the following steps: 1g of carbon nanotubes, 1g of Co-MOF-74 material, 100g of polyacrylonitrile, 5g of polyethylene glycol, 1g of niobium n-propoxide, and 100g of citric acid were added to 20800g of N,N-dimethylacetamide solvent and mixed evenly to prepare a mixed solution. The mixed solution was then electrospun with the electrostatic voltage set at 15KV, the jetting speed at 0.2ml / min, and the receiving distance at 10cm to prepare a multi-element doped carbon fiber composite material. Then, the temperature was raised to 300℃, and a peroxyformic acid mixed gas (volume ratio: peroxyformic acid: nitrogen = 5:10) was introduced at a flow rate of 100ml / min to perform an oxidative crosslinking treatment for 300min. After that, the temperature was raised to 900℃, and carbon dioxide gas was introduced at a flow rate of 100ml / min to perform an activation treatment for 600min, resulting in a carbon nanotube doped porous carbon composite material.

[0027] Example 3: A method for preparing a carbon nanotube-doped porous carbon composite material, comprising the following steps: 5g of carbon nanotubes, 5g of Co-MOF-74 material, 100g of polyacrylonitrile, 20g of polyvinyl chloride, 5g of niobium isopropoxide, and 200g of malic acid were added to 3350g of tetrahydrofuran solvent and mixed evenly to a concentration of 10wt%. The mixture was then prepared by electrospinning with the following parameters: electrostatic voltage 20KV, spray speed 0.7ml / min, and receiving distance 20cm. Multi-element doped carbon fiber composite material was then prepared. The temperature was then raised to 500℃, and a crosslinking agent mixture (volume ratio of butanone peroxide: nitrogen = 5:10) was introduced at a flow rate of 500ml / min for oxidative crosslinking treatment for 30min. Afterward, the temperature was raised to 1200℃, and carbon dioxide gas was introduced at a flow rate of 500ml / min for activation treatment for 60min, yielding a carbon nanotube doped porous carbon composite material.

[0028] Comparative Example 1: The rest of the technical solutions of Comparative Example 1 are the same as those of Example 1, except that Co-MOF-74 material is not added in Comparative Example 1.

[0029] Comparative Example 2: The rest of the technical solutions of Comparative Example 2 are the same as those of Example 1, except that niobium ethanol is not added in Comparative Example 2.

[0030] Comparative Example 3: The rest of the technical solutions of Comparative Example 3 are the same as those of Example 1, except that: in Comparative Example 3, the liquid phase method is used to replace the electrospinning in Example 1 to prepare porous carbon composite materials.

[0031] Comparative Example 4: The remaining technical solutions of Comparative Example 4 are the same as those of Example 1, except that no oxidative crosslinking treatment is performed in Comparative Example 4.

[0032] Comparative Example 5: The remaining technical solutions of Comparative Example 5 are the same as those of Example 1, except that carbon dioxide gas activation treatment is not performed in Comparative Example 5.

[0033] To verify the technical effects achieved by this application, the following physical and chemical tests and button cell tests were conducted:

[0034] The pore size and specific surface area of ​​each porous carbon composite material were tested according to the national standards GB / T-38949-2020 "Determination of Pore Size of Porous Membranes - Standard Particle Method" and GB / T7702.20-2008 "Detection of Pore Volume of Coal-based Activated Carbon". The powder resistivity (i.e., "powder resistivity" as shown in Table 1) of each porous carbon composite material was then tested using a four-probe tester. The diffusion coefficient of the material was tested by GITT (Galvanostatic Intermittent Titration Technique). The test results are shown in Table 1 below.

[0035]

[0036] As can be seen from Table 1 above, the porous carbon composite materials prepared by the embodiments of this application are superior to those of comparative examples 1-5 in terms of pore size, pore volume, specific surface area and powder resistivity. The main reason is that the embodiments of this application increase the pore volume and pore size by using MOF materials with large pore size and reduce the powder resistivity by doping with carbon nanotubes, while also improving the diffusion coefficient of the material.

[0037] The coin cell was prepared according to the following method: The negative electrode active material (corresponding to the porous carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-5, respectively), binder, conductive agent and solvent were mixed (in a ratio of 70g:15g:15g:300mL), stirred to form a slurry, and then coated onto copper foil. After drying and pressing, the negative electrode sheet was obtained. The binder used was LA136D, the conductive agent was SP (conductive carbon black), and the solvent was NMP. The electrolyte was a solution with LiPF6 as the electrolyte and a concentration of 1mol / L. The solvent was a mixture of EC and DEC in a volume ratio of 1:1. The lithium metal sheet was used as the counter electrode, and the separator was a polypropylene (PP) membrane. Each coin cell was assembled in an argon-filled glove box. Then, the following performance tests were performed on each button cell: (1) Electrochemical performance was tested on the Wuhan Landian CT2001A battery tester. The charge and discharge voltage range was 0.005V to 2.0V, and the charge and discharge rate was 0.1C. The discharge specific capacity and initial efficiency of the corresponding coin cell were tested. At the same time, the cycle performance (0.1C / 0.1C, 100 cycles) and rate performance (1C / 0.1C) of the corresponding coin cell were tested. (2) Full charge expansion test: Test the thickness D1 of the electrode after rolling, and test the thickness D2 when fully charged to 100% SOC. Full charge expansion = (D2-D1) / D1; Please refer to Table 2 below for the test results:

[0038] As shown in Table 2 above, compared with the comparative examples, the porous carbon materials prepared by the embodiments of this application have high specific capacity, first-pass efficiency and rate performance. The main reasons are: in the preparation process of the embodiments of this application, niobium oxide is doped into MOF materials with large interlayer spacing and high porosity, which reduces polarization and defects, and improves first-pass efficiency and rate performance; at the same time, carbon nanotubes are doped into the materials of the embodiments of this application to improve the electronic conductivity of the materials; and the fibrous structure prepared by electrospinning can significantly reduce expansion and improve the cycle performance of the battery.

[0039] 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 implemented 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 exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0040] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a carbon nanotube-doped porous carbon composite material, characterized in that, It should include at least the following steps: S1. Carbon nanotubes, Co-MOF-74 material, polyacrylonitrile, organic pore-forming agent, organometallic compound and water-soluble carbon source are added to solvent and mixed evenly to obtain a mixed solution; S2. The mixed solution obtained in step S1 above is used to prepare a multi-element doped carbon fiber composite material by electrospinning; S3. The multi-element doped carbon fiber composite material obtained in step S2 is oxidized and crosslinked by passing a crosslinking agent mixture gas through it, and then heated to not less than 850°C and activated by passing carbon dioxide gas through it to obtain the carbon nanotube doped porous carbon composite material. The carbon nanotube doped porous carbon composite material is preferably used as the silicon-carbon anode material for lithium batteries.

2. The method for preparing carbon nanotube-doped porous carbon composite material according to claim 1, characterized in that, In step S1, the mass ratio of carbon nanotubes, Co-MOF-74 material, polyacrylonitrile, organic pore-forming agent, organometallic compound and water-soluble carbon source is set to 1-5:1-5:100:5-20:1-5:100-200; the mass ratio of carbon nanotubes to solvent is 1:1000-50000.

3. The method for preparing carbon nanotube-doped porous carbon composite material according to claim 1, characterized in that, In step S1, the organic pore-forming agent is any one or a mixture of several of polystyrene, polyethylene glycol, polyvinyl chloride, polyglycolic acid, carboxymethyl cellulose, and lignin; the organometallic compound is any one or a mixture of several of niobium ethoxide, niobium n-propoxide, niobium isopropoxide, titanium ethoxide, titanium n-propoxide, and titanium isopropoxide; the water-soluble carbon source is any one or a mixture of several of sodium acetate, citric acid, malic acid, tartaric acid, acetic acid, succinic acid, and oxalic acid; and the solvent is any one or a mixture of several of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and tetrahydrofuran (THF).

4. The method for preparing carbon nanotube-doped porous carbon composite material according to claim 1, characterized in that, In step S2, the electrospinning operating parameters are set as follows: static voltage range of 15-20KV, jetting speed range of 0.2-0.7ml / h, and receiving distance range of 10-20cm.

5. The method for preparing carbon nanotube-doped porous carbon composite material according to claim 1, characterized in that, In step S3, the flow rate of the crosslinking agent mixed gas is set to 100-500 ml / min; the working temperature of the oxidative crosslinking is set to 300-500℃, and the working time is set to 30-300 min.

6. The method for preparing carbon nanotube-doped porous carbon composite material according to claim 1, characterized in that, In step S3, the flow rate of carbon dioxide gas is set to 100-500 ml / min; the working temperature of the activation treatment is set to 900-1200℃, and the working time is set to 60-600 min.

7. The method for preparing carbon nanotube-doped porous carbon composite material according to claim 1, characterized in that, In step S3, the crosslinking agent mixed gas is formed by mixing a vaporized peroxide with nitrogen, wherein the volume ratio of the vaporized peroxide to nitrogen is set to 1-5:

10.

8. The method for preparing carbon nanotube-doped porous carbon composite material according to claim 7, characterized in that, The peroxide compound is any one or a mixture of several of the following: peracetic acid, peroxyformic acid, butanone peroxide, benzoyl peroxide, diethyl peroxide, and tert-butanol peroxide.

9. The method for preparing carbon nanotube-doped porous carbon composite material according to claim 1, characterized in that, In step S1, the carbon nanotubes are prepared as follows: a1. Place the magnesium and nickel mesh in a CVD high-temperature furnace and heat it to 700-1200℃ under an inert gas atmosphere; a2. Acetylene gas is introduced at a flow rate of 100-500 ml / min for 30-300 min, and carbon nanotube network is grown on the nickel mesh described in step a1; a3. The grown carbon nanotube network is washed and dried to obtain the carbon nanotubes.

10. The method for preparing carbon nanotube-doped porous carbon composite material according to claim 9, characterized in that, In step a1, the aperture of the nickel mesh is 0.5-2 mm; the distance between the magnesium metal and the nickel mesh is set to 1-5 cm.

Images