Carbon nanotube, graphene and carbon black composite material and preparation method thereof

Abstract

The application relates to the technical field of lithium ion battery materials, and particularly discloses a carbon nanotube, graphene and carbon black composite material and a preparation method thereof, and the carbon nanotube, graphene and carbon black composite material comprises the following raw materials in parts by weight: the raw materials comprise the following raw materials in percentage by weight: 2-3% of carbon nanotubes, 0.3-0.7% of graphene, 6-8% of conductive carbon black and 0.5-1.5% of polyvinylpyrrolidone, and the balance is deionized water. The solid content of the carbon nanotube, graphene and carbon black composite material obtained by the application is up to 11.29%, the viscosity is as low as 1490 mPa.s, and the volume resistivity is as low as 11.18 omega.cm, so that the dispersion uniformity of the carbon nanotube, graphene and carbon black composite material is improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery materials, and more specifically, to a composite material of carbon nanotubes, graphene, and carbon black and a method for preparing the same. Background Technology

[0002] The positive electrode material of lithium-ion battery cells has very low conductivity. In order to improve the rate performance of lithium-ion batteries, conductive agents are generally doped into the positive and negative electrode materials of commercial lithium-ion batteries, especially the positive electrode material, which is doped with more conductive agents. The conductive agents come into contact with the positive electrode active material to form a conductive network, thereby improving the rate performance of lithium-ion batteries.

[0003] Currently, conductive agents on the market are usually stored and used in the form of conductive agent slurries. They mainly use carbon nanotube and graphene binary composite materials as conductive agent slurries. During processing, conductive carbon black powder needs to be added as an ingredient. However, graphene slurries are prone to sedimentation, and carbon nanotube slurries are not easy to disperse, making the added conductive carbon black more likely to be unevenly dispersed and difficult to process. Summary of the Invention

[0004] To improve the dispersion uniformity of carbon nanotube, graphene and carbon black composite materials, this application provides a carbon nanotube, graphene and carbon black composite material and its preparation method.

[0005] In a first aspect, this application provides a composite material of carbon nanotubes, graphene, and carbon black, and a method for preparing the same, which adopts the following technical solution:

[0006] A composite material of carbon nanotubes, graphene, and carbon black comprises the following raw materials in weight percentages: 2-3% carbon nanotubes, 0.3-0.7% graphene, 6-8% conductive carbon black, and 0.5-1.5% polyvinylpyrrolidone, with the balance being deionized water.

[0007] The raw materials for the carbon nanotube, graphene, and carbon black composite material of this application can be selected from 2-3% carbon nanotubes, 0.3-0.7% graphene, 6-8% conductive carbon black, and 0.5-1.5% polyvinylpyrrolidone, with the balance being deionized water. Any value within the respective range can be selected, which improves the conductivity of the carbon nanotube, graphene, and carbon black composite material. The best effect is achieved when the raw materials are 2.5% carbon nanotubes, 0.5% graphene, 7% conductive carbon black, 1% polyvinylpyrrolidone, and 89% deionized water.

[0008] By adopting the above technical solutions, carbon nanotubes exhibit high conductivity and acid / alkali resistance, along with excellent mechanical properties. Adding carbon nanotubes to polymer composites can improve the material's acid resistance and oxidation resistance. Using carbon nanotubes as a conductive agent, its network structure can effectively connect more active materials, making it more suitable for lithium-ion battery applications. Graphene possesses excellent electrochemical and mechanical properties, which can improve the cycle performance and high-rate performance of positive and negative electrode materials. Conductive carbon black has high structural density, stable chemical properties, low density, large specific surface area, and good conductivity. Using conductive carbon black as the main raw material for carbon nanotube, graphene, and carbon black composites can improve the stability of these composites.

[0009] Polyvinylpyrrolidone (PVP) is added as a dispersant. It contains cyano, aromatic and imide groups, which can effectively improve the dispersibility of graphene, carbon nanotubes and conductive carbon black in deionized water, reduce the expansion and contraction of electrode sheets, and easily form a good conductive network with active materials, so that the battery has excellent cycle life, energy density and other electrochemical performance.

[0010] As a preferred embodiment: a composite material of carbon nanotubes, graphene and carbon black, comprising the following raw materials in parts by weight: 2.4-2.8% carbon nanotubes, 0.4-0.6% graphene, 6.5-7.5% conductive carbon black and 0.8-1.2% polyvinylpyrrolidone, with the balance being deionized water.

[0011] This application discloses a carbon nanotube, graphene, and carbon black composite material whose raw materials can be selected from 2.4-2.8% carbon nanotubes, 0.4-0.6% graphene, 6.5-7.5% conductive carbon black, and 0.8-1.2% polyvinylpyrrolidone, with the balance being deionized water. Any value within the respective range can be selected, and the conductivity of the carbon nanotube, graphene, and carbon black composite material is improved.

[0012] Preferably, the graphene is modified by L-tryptophan to obtain modified graphene; the modified graphene is prepared by the following steps: preparing an aqueous solution of L-tryptophan with a mass concentration of 2-4%; adding sodium hydroxide of 40-60% L-tryptophan mass, stirring evenly, adding graphene and sodium dodecyl sulfate of 20-40% graphene mass, stirring evenly to obtain modified graphene.

[0013] By adopting the above technical solution, the dispersibility of graphene in deionized aqueous solution can be improved by treating graphene with L-tryptophan, and the addition of sodium dodecyl sulfate can further improve the effect of L-tryptophan treatment on graphene.

[0014] Preferably, the mass ratio of the graphene to the L-tryptophan aqueous solution is 1:(2-2.5).

[0015] By adopting the above technical solution and adjusting the mass ratio of graphene to L-tryptophan aqueous solution, the effect of L-tryptophan treatment on graphene can be further improved.

[0016] Preferably, the carbon nanotube, graphene and carbon black composite material further includes the following raw material in weight percentage: 0.1-0.3% polyoxyalkyleneamine.

[0017] By adopting the above technical solution and adding polyoxyalkylene amine, the critical range of polyvinylpyrrolidone dispersibility can be improved, thereby enhancing the dispersibility of polyvinylpyrrolidone.

[0018] Preferably, the weight ratio of the polyoxyalkyleneamine to polyvinylpyrrolidone is 1:(2-14).

[0019] By adopting the above technical solution and adjusting the weight ratio of polyoxyalkyleneamine to polyvinylpyrrolidone, the dispersibility of polyvinylpyrrolidone can be further improved.

[0020] Preferably, the carbon nanotube, graphene and carbon black composite material further includes the following raw material in weight percentage: 5-10% activated carbon.

[0021] By adopting the above technical solutions, activated carbon can improve the dispersibility of carbon nanotubes.

[0022] Preferably, the weight ratio of the carbon nanotubes to activated carbon is 1:(2-4).

[0023] By adopting the above technical solution and adjusting the weight ratio of carbon nanotubes to activated carbon, the dispersibility of carbon nanotubes can be further improved.

[0024] Secondly, this application provides a method for preparing a composite material of carbon nanotubes, graphene, and carbon black, which is achieved through the following technical solution:

[0025] A composite material of carbon nanotubes, graphene, and carbon black, comprising the following steps:

[0026] Polyvinylpyrrolidone was added to deionized water and stirred to disperse, resulting in a mixture.

[0027] Graphene was added to half of the mixture, stirred and dispersed, and then ground to obtain a graphene slurry.

[0028] Carbon nanotubes were added to the other half of the mixture and stirred to disperse. Graphene slurry was added, stirred to disperse, and ground. Conductive carbon black was added, stirred to disperse, and ground to obtain a composite material of carbon nanotubes, graphene, and carbon black.

[0029] By adopting the above technical solution, each raw material is stirred, dispersed and ground before being added, and graphene and carbon nanotubes are added separately to the mixture for dispersion, which improves the dispersion uniformity of each raw material in the carbon nanotube, graphene and carbon black composite material.

[0030] Thirdly, this application provides a method for preparing a composite material of carbon nanotubes, graphene, and carbon black, which is achieved through the following technical solution:

[0031] A composite material of carbon nanotubes, graphene, and carbon black, comprising the following steps:

[0032] Polyvinylpyrrolidone was added to deionized water and stirred to disperse, resulting in a mixture.

[0033] Modified graphene was added to half of the mixture, stirred and dispersed, and then ground to obtain modified graphene slurry.

[0034] Carbon nanotubes were added to the other half of the mixture and stirred to disperse. Modified graphene slurry was added, stirred to disperse, and ground. Conductive carbon black was added, stirred to disperse, and ground. The remaining raw materials were added, stirred to disperse, and ground to obtain a composite material of carbon nanotubes, modified graphene, and carbon black.

[0035] In summary, this application includes at least one of the following beneficial technical effects:

[0036] (1) By controlling the types and dosages of raw materials in the carbon nanotube, graphene and carbon black composite material, this application achieves a solid content of 10.97% and a viscosity of 1550 mPa·s in the carbon nanotube, graphene and carbon black composite material, thereby increasing the solid content and decreasing the viscosity of the carbon nanotube, graphene and carbon black composite material. The volume resistivity is 13.13 Ω•cm, which improves the dispersion uniformity of the carbon nanotube, graphene and carbon black composite material.

[0037] (2) This application replaces graphene with modified graphene and adjusts the mass ratio of graphene to L-tryptophan aqueous solution to make the solid content of carbon nanotube, graphene and carbon black composite material 11.07-11.12%, the viscosity 1530-1539 mPa·s and the volume resistivity 12.30-12.75 Ω•cm, thereby further improving the dispersion uniformity of carbon nanotube, graphene and carbon black composite material.

[0038] (3) By adding polyoxyalkylene amine and adjusting the weight ratio of polyoxyalkylene amine to polyvinylpyrrolidone, the solid content of the carbon nanotube, graphene and carbon black composite material is 11.16-11.20%, the viscosity is 1510-1515 mPa·s, and the volume resistivity is 11.72-11.89 Ω•cm, which further improves the solid content of the carbon nanotube, graphene and carbon black composite material and reduces the viscosity.

[0039] (4) By adding activated carbon and adjusting the weight ratio of carbon nanotubes to activated carbon, the solid content of the carbon nanotube, graphene and carbon black composite material is 11.25-11.29%, the viscosity is 1490-1503 mPa·s, and the volume resistivity is 11.18-11.32 Ω•cm, which further improves the dispersion uniformity of the carbon nanotube, graphene and carbon black composite material. Detailed Implementation

[0040] The present application will be further described in detail below with reference to specific embodiments.

[0041] The following raw materials used in this application are all commercially available products and are intended to fully disclose the raw materials used in this application. They should not be construed as limiting the source of the raw materials. Specifically: carbon nanotubes, multi-walled carbon nanotubes are selected; graphene, model KS6; conductive carbon black, particle size of 22μm; polyvinylpyrrolidone, effective substance content of 99%; L-tryptophan, effective substance content of 99%; sodium dodecyl sulfate, effective substance content of 99%; polyoxyalkylene amine, effective substance content of 99%; activated carbon, particle size of 200 mesh.

[0042] The following are examples of the preparation of modified graphene.

[0043] Preparation Example 1

[0044] The modified graphene of Preparation Example 1 was prepared by the following steps:

[0045] Add 3g of L-tryptophan to 97g of aqueous solution;

[0046] Add 1.5g of sodium hydroxide and stir well. Then add 66.66g of graphene and 20g of sodium dodecyl sulfate and stir well to obtain modified graphene.

[0047] Preparation Examples 2-5

[0048] The modified graphenes prepared in Examples 2-5 were prepared using the same method as those prepared in Example 1, except that the amount of graphene doped was 50 g, 43.47 g, 40 g, and 33.33 g, respectively. The other operations were the same as those in Example 1. Example

[0049] The carbon nanotube, graphene, and carbon black composite material of Example 1 was prepared by the following steps:

[0050] According to the dosage in Table 1, polyvinylpyrrolidone was added to deionized water and stirred and dispersed for 60 min to obtain a mixture;

[0051] Graphene was added to half of the mixture, stirred and dispersed for 60 minutes, and ground for 15 hours to obtain graphene slurry.

[0052] Carbon nanotubes were added to the other half of the mixture and stirred for 60 minutes. Graphene slurry was then added and stirred for 30 minutes, followed by grinding for 2 hours. Conductive carbon black was then added and stirred for 60 minutes, followed by grinding for 4 hours to obtain a composite material of carbon nanotubes, graphene, and carbon black. The graphene was not modified.

[0053] Example 2-3

[0054] The carbon nanotube, graphene and carbon black composite materials in Examples 2-3 are prepared in the same way as those in Example 1, and the types of raw materials are the same. The difference is that the dosage of each raw material is different, as detailed in Table 1.

[0055] Table 1. Dosage of each raw material in the carbon nanotube, graphene, and carbon black composite materials of Examples 1-3 (unit: %)

[0056]

[0057] Examples 4-8

[0058] The carbon nanotube, graphene, and carbon black composite materials in Examples 4-8 were prepared using the same method as in Example 2, except that the graphene was replaced with the modified graphene prepared in Examples 1-5, while the other raw materials and dosages were the same as in Example 2.

[0059] Examples 9-13

[0060] The carbon nanotube, graphene and carbon black composite materials in Examples 9-13 were prepared using the same method as in Example 6, except that polyoxyalkylene amine was added to the raw materials, and polyoxyalkylene amine was added after the conductive carbon black was added and dispersed and ground, and stirred and dispersed for 30 min. The specific dosage is shown in Table 2.

[0061] Table 2. Dosage of each raw material in the carbon nanotube, graphene and carbon black composite materials of Examples 9-13 (unit: %)

[0062]

[0063] Examples 14-18

[0064] The carbon nanotube, graphene and carbon black composite materials in Examples 14-18 were prepared using the same method as in Example 11, except that activated carbon was added to the raw materials. Activated carbon was added after the polyoxyalkylene amine was added and dispersed, and then stirred and dispersed for 30 minutes. The specific dosage is detailed in Table 3.

[0065] Table 3. Dosage of each raw material in the carbon nanotube, graphene and carbon black composite materials of Examples 14-18 (unit: %)

[0066]

[0067] Comparative Example 1

[0068] The carbon nanotube, graphene, and carbon black composite material of Comparative Example 1 was prepared in the same way as that of Example 1, except that polyvinylpyrrolidone was not added to the raw materials of the carbon nanotube, graphene, and carbon black composite material, while the other raw materials and dosages were the same as those of Example 1.

[0069] Comparative Example 2

[0070] The carbon nanotube, graphene, and carbon black composite material of Comparative Example 2 has the same raw material types and dosages as that of Example 1. The difference is that graphene is added to half of the mixture and stirred and dispersed for 60 minutes to obtain graphene slurry; carbon nanotubes are added to the other half of the mixture and stirred and dispersed for 60 minutes. The rest of the operation is the same as in Example 1.

[0071] Comparative Example 3

[0072] The carbon nanotube, graphene, and carbon black composite material of Comparative Example 3 was prepared in the same way as that of Example 1, except that: carbon nanotubes were added to the other half of the mixture, graphene slurry was added, conductive carbon black was added, the mixture was stirred and dispersed for 60 min, and ground for 4 h. The remaining operations were the same as those in Example 1.

[0073] Performance Testing (Part 1)

[0074] The performance of carbon nanotube, graphene and carbon black composite materials obtained in different Examples 1-18 and Comparative Examples 1-3 was tested using the following testing standards or methods. The test results are detailed in Table 4.

[0075] Solid content: The solid content of the composite material of carbon nanotubes, graphene and carbon black was determined in accordance with DB 13 / T 5025.1-2019 "Determination of Graphene-Carbon Nanotube Composite Conductive Paste - Part 1: Determination of Solid Content".

[0076] Viscosity: The viscosity of carbon nanotube, graphene and carbon black composite materials was tested according to DB 13 / T 5026 "Determination of physical properties of graphene conductive paste - Part 1 Determination of paste viscosity".

[0077] Volume resistivity: A composite material of carbon nanotubes, graphene, and carbon black was added to lithium iron phosphate as a conductive agent at an addition amount of 2%, and the volume resistivity of lithium iron phosphate was tested according to the test standard GB / T 33822-2017.

[0078] Table 4 Performance test results of different carbon nanotube, graphene and carbon black composite materials

[0079]

[0080] The test results in Table 4 show that the carbon nanotube, graphene and carbon black composite material obtained in this application has the highest solid content of 11.29% and the lowest viscosity of 1490 mPa·s, indicating a high solid content. The lowest volume resistivity is 11.18 Ω•cm, which improves the dispersion uniformity of the carbon nanotube, graphene and carbon black composite material.

[0081] In Examples 1-3, the solid content of the carbon nanotube, graphene, and carbon black composite material in Example 2 was 10.97%, higher than that in Examples 1 and 3, and the viscosity was 1550 mPa·s, lower than that in Examples 1 and 3. This indicates that the amount of polyvinylpyrrolidone (PVP) in the carbon nanotube, graphene, and carbon black composite material in Example 2 was appropriate, increasing the solid content of the composite material and reducing the viscosity. Furthermore, the volume resistivity of the carbon nanotube, graphene, and carbon black composite material was 13.13 Ω•cm, both lower than that in Examples 1 and 3, improving the dispersion uniformity of the composite material. This may be related to the addition of PPVP as a dispersant, which contains cyano groups, aromatic groups, and imide groups. This effectively improves the dispersibility of graphene, carbon nanotubes, and conductive carbon black in deionized water, reduces the expansion and contraction of the electrode sheets, and facilitates the formation of a good conductive network with the active material, resulting in excellent cycle life, energy density, and other electrochemical performance of the battery.

[0082] In Examples 4-8, the solid content of the carbon nanotube, graphene, and carbon black composite materials in Examples 5-7 was 11.07-11.12%, higher than that in Examples 4 and 8, and the viscosity was 1530-1539 mPa·s, lower than that in Examples 4 and 8. This indicates that a mass ratio of graphene to L-tryptophan aqueous solution of 1:(2-2.5) is more suitable, increasing the solid content of the carbon nanotube, graphene, and carbon black composite materials and reducing the viscosity. Furthermore, the volume resistivity of the carbon nanotube, graphene, and carbon black composite materials was 12.30-12.75 Ω•cm, both lower than that in Examples 4 and 8, improving the dispersion uniformity of the composite materials. This may be related to adjusting the mass ratio of graphene to L-tryptophan aqueous solution, which can further enhance the effect of L-tryptophan treatment on graphene.

[0083] In Examples 9-13, the solid content of the carbon nanotube, graphene, and carbon black composite materials in Examples 10-12 was 11.16-11.20%, higher than that in Examples 9 and 13, and the viscosity was 1510-1515 mPa·s, lower than that in Examples 9 and 13. This indicates that a weight ratio of polyoxyalkyleneamine to polyvinylpyrrolidone of 1:(2-14) is more suitable, increasing the solid content of the carbon nanotube, graphene, and carbon black composite materials and reducing the viscosity. Furthermore, the volume resistivity of the carbon nanotube, graphene, and carbon black composite materials was 11.72-11.89 Ω•cm, both lower than that in Examples 9 and 13, improving the dispersion uniformity of the composite materials. This may be related to the fact that adjusting the weight ratio of polyoxyalkyleneamine to polyvinylpyrrolidone can further improve the dispersibility of polyvinylpyrrolidone.

[0084] In Examples 14-18, the solid content of the carbon nanotube, graphene, and carbon black composite materials in Examples 15-17 was 11.25-11.29%, higher than that in Examples 14 and 18, and the viscosity was 1490-1503 mPa·s, lower than that in Examples 14 and 18. This indicates that a carbon nanotube to activated carbon weight ratio of 1:(2-4) is more suitable, increasing the solid content of the carbon nanotube, graphene, and carbon black composite materials and reducing the viscosity. Furthermore, the volume resistivity of the carbon nanotube, graphene, and carbon black composite materials was 11.18-11.32 Ω•cm, both lower than that in Examples 4 and 8, improving the dispersion uniformity of the carbon nanotube, graphene, and carbon black composite materials. This may be related to the fact that adjusting the weight ratio of carbon nanotubes to activated carbon can further improve the dispersibility of carbon nanotubes.

[0085] Based on the performance testing data of the carbon nanotube, graphene, and carbon black composite materials from Example 1 and Comparative Examples 1-3, it was found that adding polyvinylpyrrolidone to the carbon nanotube, graphene, and carbon black composite materials can increase the solid content and reduce the viscosity. Furthermore, adding graphene to half of the mixture, stirring and dispersing for 60 min, and grinding for 15 h, adding carbon nanotubes to the other half of the mixture, stirring and dispersing for 60 min, adding graphene slurry, stirring and dispersing for 30 min, and grinding for 2 h, and adding conductive carbon black, stirring and dispersing for 60 min, and grinding for 4 h can increase the solid content and reduce the viscosity of the carbon nanotube, graphene, and carbon black composite materials, and improve the dispersion uniformity of the carbon nanotube, graphene, and carbon black composite materials.

[0086] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A composite material of carbon nanotubes, graphene, and carbon black, characterized in that, It comprises the following raw materials by weight percentage: 2-3% carbon nanotubes, 0.3-0.7% graphene, 6-8% conductive carbon black, 0.1-0.3% polyoxyalkyleneamine, 5-10% activated carbon, and 0.5-1.5% polyvinylpyrrolidone, with the balance being deionized water; The graphene is modified by L-tryptophan to obtain modified graphene; the modified graphene is prepared by the following steps: preparing an L-tryptophan aqueous solution with a mass concentration of 2-4%; adding sodium hydroxide of 40-60% L-tryptophan mass, stirring evenly, adding graphene and sodium dodecyl sulfate of 20-40% graphene mass, stirring evenly to obtain modified graphene. The preparation method of the carbon nanotube, graphene, and carbon black composite material includes the following steps: Polyvinylpyrrolidone was added to deionized water and stirred to disperse, resulting in a mixture. Modified graphene was added to half of the mixture, stirred and dispersed, and then ground to obtain modified graphene slurry. Carbon nanotubes were added to the other half of the mixture and stirred to disperse. Modified graphene slurry was added, stirred to disperse, and ground. Conductive carbon black was added, stirred to disperse, and ground. The remaining raw materials were added, stirred to disperse, and ground to obtain a composite material of carbon nanotubes, modified graphene, and carbon black.

2. The carbon nanotube, graphene, and carbon black composite material according to claim 1, characterized in that: The mass ratio of graphene to L-tryptophan aqueous solution is 1:(2-2.5).

3. The carbon nanotube, graphene, and carbon black composite material according to claim 1, characterized in that: The weight ratio of the polyoxyalkyleneamine to polyvinylpyrrolidone is 1:(2-14).

4. The carbon nanotube, graphene, and carbon black composite material according to claim 1, characterized in that: The weight ratio of carbon nanotubes to activated carbon is 1:(2-4).

5. A method for preparing the carbon nanotube, graphene, and carbon black composite material according to any one of claims 1-4, characterized in that, The following steps are included: Polyvinylpyrrolidone was added to deionized water and stirred to disperse, resulting in a mixture. Modified graphene was added to half of the mixture, stirred and dispersed, and then ground to obtain modified graphene slurry. Carbon nanotubes were added to the other half of the mixture and stirred to disperse. Modified graphene slurry was added, stirred to disperse, and ground. Conductive carbon black was added, stirred to disperse, and ground. The remaining raw materials were added, stirred to disperse, and ground to obtain a composite material of carbon nanotubes, modified graphene, and carbon black.

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