Graphene-carbon nanotube composite conductive cathode paste and its preparation method

Abstract

The present invention provides a graphene-carbon nanotube composite conductive cathode paste, and the conductive paste is composed of the following components: the mass ratio of active material: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent is 70-97.5%: 0.1-5%: 0.5-15%: 0.5-10%: 1-5%; the solvent of the conductive paste is at least one of deionized water, absolute ethanol, and alkaline solution. The conductive agent is composed of carbon nanotubes: graphene: super conductive carbon black in a mass ratio of 0.5-1.5: 0.5-1.5: 1-2; the particle size of the graphene is 50-400 nm, and the carbon nanotube diameter is 5-10 nm. The active material consists of LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 in a mass ratio of 1.7-8:1. The graphene-carbon nanotube composite conductive cathode paste prepared by the present invention has good dispersibility and a long stable storage time.

Description

Technical Field

[0001] The present invention relates to the field of conductive pastes, and particularly to a graphene carbon nanotube composite conductive positive electrode paste and a preparation method thereof. Background Art

[0002] Paste preparation is an important step in batteries, mainly aiming to fully mix the active material with the non-active components. Therefore, the quality and performance of the electrode paste directly affect the electrochemical performance of the electrode sheet. To ensure that the electrode sheet fully exhibits its electrochemical characteristics, on the one hand, it is the uniformity of the paste, ensuring the full and uniform mixing of each component, avoiding agglomeration, and at the same time ensuring the controllability of the electrode sheet loading and the true repeatability of the electrochemical performance; on the other hand, it is the matching between the non-active components and the active substances. Selecting a conductive agent with excellent conductivity and a binding system with better binding performance can improve the electrochemical performance while reducing the content of non-active components, thereby increasing the overall energy density of the battery.

[0003] As a new type of conductive agent for lithium-ion batteries, carbon nanotube conductive paste can improve the conductivity of the battery, reduce the amount of binder, and significantly improve the energy density of lithium-ion batteries, but there are dispersion problems. Conductive pastes prepared from single graphene or carbon nanotubes have greatly improved performance, but there is still room for improvement in processing, especially in the design of high-solid-content products. Increasing the solid content of the product can indirectly increase production capacity, save costs, reduce environmental pollution and waste of resources. Existing carbon black can meet the requirements of high solid content, but its performance as a conductive agent is far inferior to that of graphene and carbon nanotubes. Therefore, preparing a conductive paste with good dispersion and stability is of great significance for the further development of the battery field. Summary of the Invention

[0004] One aspect of the present invention provides a graphene carbon nanotube composite conductive positive electrode paste, which is composed of the following components:

[0005] Active material: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent mass ratio is 70-97.5%: 0.1-5%: 0.5-15%: 0.5-10%: 1-5%; the solvent of the conductive paste is at least one of deionized water, absolute ethanol, and alkaline solution.

[0006] The conductive agent is composed of carbon nanotubes: graphene: super conductive carbon black in a mass ratio of 0.5-1.5: 0.5-1.5: 1-2; the particle size of the graphene is 50-400 nm, and the carbon nanotube diameter is 5-10 nm.

[0007] The active material is composed of LiNi 0.8Co 0.15 Al 0.05 O2 and LiMn2O4 are composed in a mass ratio of 1.7 - 8:1.

[0008] On the other hand, the present invention provides a method for preparing a graphene carbon nanotube composite conductive cathode paste, and the preparation method includes the following steps:

[0009] Mix organic bentonite, polyacrylic acid and carboxymethyl cellulose and dropwise add a solvent to fully dissolve them to obtain a first mixture. Add a conductive agent to the first mixture and stir evenly to obtain a second mixture. Add an active substance to the second mixture and further stir evenly to obtain the graphene carbon nanotube composite conductive cathode paste.

[0010] The beneficial effects achieved by the present invention include at least one of the following:

[0011] 1. The graphene carbon nanotube composite conductive cathode paste prepared by the present invention has good dispersibility and a long stable storage time. At room temperature, the storage time can be guaranteed to be more than 90 days.

[0012] 2. For the graphene carbon nanotube composite conductive cathode paste prepared by the present invention, three conductive agents reduce the internal resistance. At the same time, with the compounding of the paste components, particle size, organic bentonite, polyacrylic acid and carboxymethyl cellulose, the stability of the paste is significantly improved, which helps to make the load amount of the electrode sheet uniformly controllable and improves the electrochemical performance. Specific Embodiments

[0013] In an exemplary embodiment of the present invention, the graphene carbon nanotube conductive paste is composed of the following components: the mass ratio of active substance: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent is 70 - 97.5%: 0.1 - 5%: 0.5 - 15%: 0.5 - 10%: 1 - 5%; the solvent of the conductive paste can be at least one of deionized water, absolute ethanol and alkaline solution. The pH of the alkaline solution is 9 - 10.

[0014] The conductive agent is composed of carbon nanotubes: graphene: super conductive carbon black in a mass ratio of 0.5 - 1.5: 0.5 - 1.5: 1 - 2; the particle size of the graphene is 50 - 400 nm, and the tube diameter of the carbon nanotubes is 5 - 10 nm.

[0015] The active substance is composed of LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 are composed in a mass ratio of 1.7 - 8:1.

[0016] In an exemplary embodiment of the present invention, the mass ratio of the active material: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent is 75-90%: 1.5-4%: 3-10%: 2-8%: 2-4%. Further, the mass ratio of the active material: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent is 80-85%: 2-3%: 5-8%: 4-6%: 2.5-3%.

[0017] In an exemplary embodiment of the present invention, the mass ratio of the carbon nanotubes: graphene: super conductive carbon black is 0.8-1.2: 0.8-1.2: 1.2-1.6. The particle size of the graphene is 100-300 nm, and the carbon nanotube diameter is 7-9 nm.

[0018] In an exemplary embodiment of the present invention, organic bentonite, polyacrylic acid, and carboxymethyl cellulose are mixed and a solvent is added dropwise and dissolved sufficiently to obtain a first mixture. A conductive agent is added to the first mixture and stirred evenly to obtain a second mixture. An active material is added to the second mixture and further stirred evenly to obtain the graphene carbon nanotube composite conductive positive electrode paste. In the present invention, organic bentonite, polyacrylic acid, and carboxymethyl cellulose are used as dispersants; carbon nanotubes, graphene, and super conductive carbon black are used as conductive agents. The purpose of dissolving the dispersant first is to ensure that the viscosity of the paste prepared later is relatively high in the static state, which can effectively prevent the precipitation and agglomeration of the paste. For example, when forming the paste, the mass ratio of the conductive agent: dispersant: solvent can be 2-5: 0.1-5: 90-97.9. However, the present invention is not limited thereto.

[0019] Example 1

[0020] The active material, carbon nanotubes, graphene, and super conductive carbon black required for the experiment are ground. The raw materials are in a mass ratio of organic bentonite: polyacrylic acid: carboxymethyl cellulose of 2%: 3%: 3%. Deionized water is added dropwise, and magnetic constant temperature stirring is carried out. After sufficient dissolution, a ternary conductive agent is added and stirred evenly, where the mass ratio of carbon nanotubes: graphene: super conductive carbon black is 0.8: 0.8: 1, the particle size of the graphene is 100 nm, and the carbon nanotube diameter is 6 nm. Finally, the active material is added and further stirred, where the active materials LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 are in a mass ratio of 2:1 to obtain the graphene carbon nanotube composite conductive positive electrode paste.

[0021] Example 2

[0022] The active substance, carbon nanotubes, graphene, and super conductive carbon black required for the experiment are ground. The raw materials are in a mass ratio of organic bentonite: polyacrylic acid: carboxymethyl cellulose of 3%: 5%: 5%. Deionized water is added dropwise, and magnetic constant temperature stirring is carried out. After complete dissolution, a ternary conductive agent is added and stirred evenly. Among them, the mass ratio of carbon nanotubes: graphene: super conductive carbon black is 1: 0.8: 1.5. The particle size of graphene is 80 nm, and the tube diameter of carbon nanotubes is 9 nm. Finally, the active substance is added and further stirred. Among them, the active substances LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 are in a mass ratio of 5:1 to obtain the graphene carbon nanotube composite conductive positive electrode paste.

[0023] Example 3

[0024] The active substance, carbon nanotubes, graphene, and super conductive carbon black required for the experiment are ground. The raw materials are in a mass ratio of organic bentonite: polyacrylic acid: carboxymethyl cellulose of 2%: 10%: 6%. Deionized water is added dropwise, and magnetic constant temperature stirring is carried out. After complete dissolution, a ternary conductive agent is added and stirred evenly. Among them, the mass ratio of carbon nanotubes: graphene: super conductive carbon black is 0.8: 1: 1.5. The particle size of graphene is 200 nm, and the tube diameter of carbon nanotubes is 6 nm. Finally, the active substance is added and further stirred. Among them, the active substances LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 are in a mass ratio of 3:1 to obtain the graphene carbon nanotube composite conductive positive electrode paste.

[0025] Comparative Example 1

[0026] Based on Example 1, the difference is that carbon nanotubes are not added.

[0027] Comparative Example 2

[0028] Based on Example 1, the difference is that graphene is not added.

[0029] Comparative Example 3

[0030] Based on Example 1, the difference is that super conductive carbon black is not added.

[0031] Comparative Example 4

[0032] Based on Example 1, the difference is that the particle size of graphene is too small.

[0033] Comparative Example 5

[0034] Based on Example 1, the difference is that the particle size of graphene is too large.

[0035] Comparative Example 6

[0036] Based on Example 1, the difference lies in that the carbon nanotube diameter is too small.

[0037] Comparative Example 7

[0038] Based on Example 1, the difference lies in that the carbon nanotube diameter is too large.

[0039] Comparative Example 8

[0040] Based on Example 1, the difference lies in that carboxymethyl cellulose is not added.

[0041] Comparative Example 9

[0042] Based on Example 1, the difference lies in that polyacrylic acid is not added.

[0043] Comparative Example 10

[0044] Based on Example 1, the difference lies in that organic bentonite is not added.

[0045] The ratio of the graphene carbon nanotube slurry is shown in Table 1.

[0046] Table 1 Ratio of the graphene carbon nanotube slurry

[0047]

[0048]

[0049] At 25 °C and 50 °C, in the same environment, stability experiments were respectively carried out on the graphene carbon nanotube composite conductive cathode slurries provided in Examples 1 to 3 and Comparative Examples 1 to 10. The storage time was recorded, and the results are listed in Table 2.

[0050] Table 2 Slurry storage time table

[0051] 25 °C / day 50 °C / day Example 1 95 70 Example 2 94 73 Example 3 96 68 Comparative Example 1 80 60 Comparative Example 2 82 58 Comparative Example 3 82 62 Comparative Example 4 70 60 Comparative Example 5 65 57 Comparative Example 6 65 58 Comparative Example 7 68 60 Comparative Example 8 20 10 Comparative Example 9 20 8 Comparative Example 10 18 7

[0052] Referring to Table 1 and Table 2, Comparative Examples 1, 2, and 3 were respectively compared with Example 1. It can be seen that the conductive agent components and ratios of the present invention have an impact on the stability of the slurry. Under the compounding of the three conductive agents, the stability of the slurry is improved.

[0053] Referring to Table 1 and Table 2, Comparative Examples 4, 5, 6, and 7 were respectively compared with Example 1. It can be seen that too large or too small graphene particle size and carbon nanotube diameter will have an impact on the stability of the slurry.

[0054] Referring to Table 1 and Table 2, Comparative Examples 8, 9, 10, and 11 were respectively compared with Example 1. It can be seen that the dispersant is crucial for the stability of the slurry.

[0055] In summary, under the compounding of the slurry particle size and the slurry component ratio of the graphene-carbon nanotube composite conductive positive electrode slurry prepared by the present invention, the stability of the slurry is greatly improved. At room temperature, the storage time of the slurry is more than 90 days. At a higher temperature, for example, at 50 °C, the storage time of the slurry is more than 65 days. The stability of the slurry is significantly improved, which helps to make the loading amount of the electrode sheet uniform and controllable and improves the electrochemical performance.

[0056] The above are only the embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A graphene-carbon nanotube composite conductive positive electrode paste, characterized in that, The conductive positive electrode paste consists of the following components: active material: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent with a mass ratio of 75-90%: 1.5-4%: 3-10%: 2-8%: 2-4%; the solvent of the conductive positive electrode paste is deionized water; The conductive agent consists of carbon nanotubes: graphene: super conductive carbon black with a mass ratio of 0.5-1.5: 0.5-1.5: 1-2; the particle size of the graphene is 50-400 nm, and the diameter of the carbon nanotubes is 5-10 nm; The active material consists of LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4, which are composed in a mass ratio of 1.7 to 8:

1.

2. The conductive positive electrode paste according to claim 1, wherein The mass ratio of the active material: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent is 80-85%: 2-3%: 5-8%: 4-6%: 2.5-3%.

3. The conductive positive electrode paste according to claim 1, wherein The mass ratio of the carbon nanotubes: graphene: super conductive carbon black is 0.8-1.2: 0.8-1.2: 1.2-1.

6.

4. The conductive positive electrode paste according to claim 1, wherein The particle size of the graphene is 100-300 nm, and the diameter of the carbon nanotubes is 7-9 nm.

5. A method for preparing a graphene-carbon nanotube composite conductive cathode paste according to any one of claims 1 to 4, characterized in that, Including the following steps: Mix the organic bentonite, polyacrylic acid and carboxymethyl cellulose and add the solvent dropwise to dissolve them sufficiently to obtain a first mixture. Add the conductive agent to the first mixture and stir evenly to obtain a second mixture. Add the active material to the second mixture and stir further evenly to obtain the graphene carbon nanotube composite conductive positive electrode paste.

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