Carbon nanotube conductive paste, preparation process and application thereof

Abstract

The application provides a carbon nanotube conductive slurry, a preparation process and application thereof, and the preparation process comprises the following steps: firstly, mixing a dispersing agent, a stabilizing agent and water to obtain a dispersion liquid; secondly, mixing the obtained dispersion liquid and carbon nanotubes to obtain a premixed solution; and finally, performing high-energy dissociation and grinding on the obtained premixed solution to obtain the carbon nanotube conductive slurry. The carbon nanotube conductive slurry prepared by the preparation process has the advantages of high dispersion uniformity, low viscosity, good fluidity and high solid content. On the premise that the long-range conductive advantage of the carbon nanotube itself can be fully exerted, the addition amount of the carbon nanotube in the negative electrode material is reduced, which is helpful to improve the energy density of the negative electrode material, and further helpful to improve the electrical performance of a lithium ion battery containing the negative electrode material.

Description

Technical Field

[0001] This invention belongs to the field of conductive paste technology, specifically relating to a carbon nanotube conductive paste, its preparation process, and its application. Background Technology

[0002] With the development of industrial technology, new environmentally friendly energy batteries are receiving increasing attention. Lithium-ion batteries, as a green energy source at present, have been widely used in mobile phone batteries, new energy vehicles, computers, small and medium-sized energy storage systems and other fields due to their advantages such as high capacity, light weight, safety and long cycle life.

[0003] Adding carbon nanotubes to lithium-ion batteries can significantly increase their cycle life and effectively improve battery performance. Carbon nanotubes offer several advantages: excellent electronic conductivity; their fibrous structure allows them to form a continuous conductive network within the electrode active material; the addition of carbon nanotubes enhances the toughness of the electrode, mitigating peeling caused by volume changes during charging and discharging, thus improving cycle life; and carbon nanotubes can significantly improve the penetration of electrolyte into the electrode material, therefore they are often formulated into slurries for use in the positive and negative electrode materials of lithium-ion batteries.

[0004] In the preparation of carbon nanotube slurries, the degree of dispersion of carbon nanotubes in the slurry and the length of the carbon nanotubes are often contradictory. Uniformly dispersed carbon nanotube conductive slurries can provide a uniform conductive network, thereby improving conductivity. CN106046982A discloses a highly dispersed aqueous carbon nanotube conductive slurry, comprising the following components by weight: 10-60 parts by weight of water-soluble resin, 5-40 parts by weight of activated carbon nanotubes, and 20-70 parts by weight of aqueous solvent B. The activated carbon nanotubes are obtained by high-speed stirring of carbon nanotubes, while a dispersant dissolved in liquid is sprayed into the stirred carbon nanotube powder by spraying, thereby activating the surface of the carbon nanotubes. The highly dispersed aqueous carbon nanotube conductive slurry provided by this invention has good conductivity, good antistatic properties, good dispersibility, and can be stored for a long time.

[0005] However, the solid content of existing carbon nanotube conductive pastes is often low. This is because the smaller the diameter and the longer the length of the carbon nanotubes, the more difficult it is to prepare carbon nanotube conductive pastes with high solid content in order to avoid high viscosity and poor fluidity. In other words, existing carbon nanotube conductive pastes are difficult to have both high solid content and excellent fluidity, which limits the further development of carbon nanotube conductive pastes.

[0006] Therefore, developing a carbon nanotube conductive paste that combines excellent flowability, good dispersibility, and high solid content is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a carbon nanotube conductive slurry, its preparation process, and its application. The preparation process can produce a carbon nanotube conductive slurry with high dispersion uniformity, low viscosity, good flowability, and high solid content, ensuring that the long-range conductivity of carbon nanotubes is fully utilized. It effectively improves the performance of the negative electrode material with a low addition amount, thereby helping to enhance the electrical performance of lithium-ion batteries.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a process for preparing a carbon nanotube conductive paste, the process comprising the following steps:

[0010] (1) Mix the dispersant, stabilizer and water to obtain a dispersion;

[0011] (2) Mix the dispersion obtained in step (1) with carbon nanotubes to obtain a premixed solution;

[0012] (3) The premixed solution obtained in step (2) is subjected to high-energy dissociation and grinding to obtain the carbon nanotube conductive slurry.

[0013] The preparation process of the carbon nanotube conductive slurry provided by this invention first involves mixing a dispersant, a stabilizer, and water to obtain a dispersion. Then, carbon nanotubes are mixed with the dispersion to obtain a premixed solution. Finally, the premixed solution undergoes high-energy dissociation and grinding to obtain a uniformly dispersed carbon nanotube conductive slurry with low viscosity, high fluidity, and high solid content. This carbon nanotube conductive slurry ensures that the long-range conductivity inherent in carbon nanotubes can be fully utilized. Furthermore, due to its high solid content, its addition amount in the negative electrode material can be reduced, which helps to improve the energy density of lithium-ion batteries containing the negative electrode material. Adding it to the negative electrode material can also improve the performance of the negative electrode active material, further enhancing the cycle performance and charge-discharge performance of lithium-ion batteries prepared using it. Simultaneously, the carbon nanotube conductive slurry also has the advantages of good fluidity, ease of storage, and non-viscosity rebound and non-settling properties. No additional mechanical stirring is required before use; it can be used directly without any additional stirring process.

[0014] Preferably, the content of dispersant in the dispersion is 1 to 10 parts by weight, such as 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, or 9 parts by weight.

[0015] Preferably, the dispersant comprises any one or a combination of at least two of polyvinylpyrrolidone, carboxymethyl cellulose, carboxymethyl cellulose salt, or polystyrene butadiene.

[0016] Preferably, the content of stabilizer in the dispersion is 1 to 10 parts by weight, such as 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, or 9 parts by weight.

[0017] Preferably, the stabilizer comprises any one or a combination of at least two of glycerol, cetyltrimethylammonium bromide, polyoxyethylene ether, or styrene-butadiene rubber.

[0018] Preferably, the water content in the dispersion is 65 to 97 parts by weight, such as 66 parts by weight, 68 parts by weight, 70 parts by weight, 72 parts by weight, 74 parts by weight, 76 parts by weight, 78 parts by weight, 80 parts by weight, 82 parts by weight, 84 parts by weight, 86 parts by weight, 88 parts by weight, 90 parts by weight, 92 parts by weight, 94 parts by weight, or 97 parts by weight.

[0019] Preferably, the mixing in step (1) is carried out under a shear rate of 1800 to 2200 rpm (e.g., 1850 rpm, 1900 rpm, 1950 rpm, 2000 rpm, 2050 rpm, 2100 rpm or 2150 rpm).

[0020] Preferably, the mixing time in step (1) is 40 to 60 minutes, such as 42 minutes, 44 minutes, 46 minutes, 48 ​​minutes, 50 minutes, 52 minutes, 54 minutes, 56 minutes, or 58 minutes.

[0021] Preferably, the carbon nanotube content in the premixed solution is 1 to 25 parts by weight, such as 24 parts by weight, 6 parts by weight, 8 parts by weight, 10 parts by weight, 12 parts by weight, 14 parts by weight, 16 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, or 24 parts by weight.

[0022] Preferably, the carbon nanotubes have a length of 30–100 μm, such as 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, or 90 μm.

[0023] Preferably, the mixing in step (2) is carried out under a shear rate of 1800 to 2200 rpm (e.g., 1850 rpm, 1900 rpm, 1950 rpm, 2000 rpm, 2050 rpm, 2100 rpm or 2150 rpm).

[0024] Preferably, the mixing time in step (2) is 40 to 60 minutes, such as 42 minutes, 44 minutes, 46 minutes, 48 ​​minutes, 50 minutes, 52 minutes, 54 minutes, 56 minutes or 58 minutes.

[0025] Preferably, the high-energy dissociation occurs 1 to 3 times, for example, 1 time, 2 times, or 3 times.

[0026] Preferably, the high-energy dissociation pressure is 1500-2000 bar, such as 1550 bar, 1600 bar, 1650 bar, 1700 bar, 1750 bar, 1800 bar, 1850 bar, 1900 bar or 1950 bar.

[0027] Preferably, the grinding speed is 800-1200 r / min, such as 850 r / min, 900 r / min, 950 r / min, 1000 r / min, 1050 r / min, 1100 r / min or 1150 r / min.

[0028] Preferably, the grinding time is 30 to 160 minutes, such as 40 minutes, 50 minutes, 60 minutes, 80 minutes, 100 minutes, 120 minutes or 140 minutes, and more preferably 100 to 150 minutes.

[0029] Preferably, the solid content of the carbon nanotube conductive paste is 3% to 35%, such as 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, or 34%, and more preferably 20% to 25%.

[0030] As a preferred embodiment of the present invention, the preparation process specifically includes the following steps:

[0031] (1) Mix the dispersant, stabilizer and water at a shear rate of 1800-2200 rpm for 40-60 min to obtain a dispersion;

[0032] (2) The dispersion obtained in step (1) and carbon nanotubes are mixed at a shear rate of 1800-2200 rpm for 40-60 min to obtain a premixed solution;

[0033] (3) The premixed solution obtained in step (2) is subjected to high-energy dissociation 1 to 3 times under a pressure of 1500 to 2000 bar, and then ground for 30 to 160 min at a speed of 800 to 1200 r / min to obtain a carbon nanotube conductive slurry with a solid content of 3 to 35%.

[0034] In a second aspect, the present invention provides a carbon nanotube conductive paste, which is prepared using the preparation process described in the first aspect.

[0035] Thirdly, the present invention provides a negative electrode slurry comprising a combination of carbon nanotube conductive slurry as described in the second aspect, a negative electrode active material, a binder, and a solvent.

[0036] Preferably, the negative electrode active material comprises silicon carbide.

[0037] Fourthly, the present invention provides a negative electrode sheet, which is obtained by coating a negative electrode slurry as described in the third aspect onto a copper foil and then drying it.

[0038] Fifthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode sheet as described in the third aspect.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The carbon nanotube conductive slurry prepared by the carbon nanotube conductive slurry preparation process provided by the present invention can be stored for 180 days without hydrogel phenomenon, and the viscosity does not rebound and has ultra-high fluidity. When using it, there is no need to add a mechanical stirring process for dispersion, and no additional application process cost is required.

[0041] (2) The preparation process of carbon nanotube conductive slurry provided by the present invention combines high-energy dissociation and grinding, which can ensure that the carbon nanotubes in the obtained carbon nanotube conductive slurry are uniformly dispersed and have a high solid content. Therefore, it has the characteristic of low addition amount when used, which can increase the proportion of negative electrode active material in the negative electrode material containing it, thereby increasing the energy density of lithium-ion battery. Moreover, the carbon nanotube conductive slurry can effectively coat the surface of negative electrode active material to improve negative electrode performance, thereby effectively improving the cycle life and charge-discharge performance of lithium-ion battery prepared using the negative electrode material. Attached Figure Description

[0042] Figure 1 Viscosity changes of carbon nanotube conductive slurries provided in Examples 1-15 and Comparative Examples 1-3 after storage for 0-180 days. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] Example 1

[0045] A process for preparing a carbon nanotube conductive paste includes the following steps:

[0046] (1) Mix 5 parts by weight of polyvinylpyrrolidone, 0.05 parts by weight of carboxymethyl cellulose, 5 parts by weight of glycerol and 80 parts by weight of distilled water at a shear rate of 2000 rpm for 40 min to obtain a dispersion.

[0047] (2) The dispersion obtained in step (1) and 10 parts by weight of carbon nanotubes (approximately 80 μm in length) were mixed for 40 min at a shear rate of 2000 rpm to obtain a premixed solution.

[0048] (3) The premixed solution obtained in step (2) is subjected to high-energy dissociation twice under a pressure of 1800 bar, and then ground for 100 min at a speed of 1000 r / min to obtain the carbon nanotube conductive slurry.

[0049] Examples 2-5

[0050] A preparation process for a carbon nanotube conductive paste differs from Example 1 only in that the amount of distilled water added is 50 parts by weight (Example 2), 90 parts by weight (Example 3), 170 parts by weight (Example 4), and 200 parts by weight (Example 5), respectively. All other conditions, parameters, and steps are the same as in Example 1.

[0051] Examples 6-7

[0052] A preparation process for a carbon nanotube conductive paste differs from Example 1 only in that the number of high-energy dissociations is 1 (Example 6) and 3 (Example 7), while the other conditions, parameters, and steps are the same as in Example 1.

[0053] Examples 8-11

[0054] A preparation process for a carbon nanotube conductive paste differs from Example 1 only in that the high-energy dissociation pressures are 1000 bar (Example 8), 1500 bar (Example 9), 2000 bar (Example 10), and 2500 bar (Example 11), respectively. All other conditions, parameters, and steps are the same as in Example 1.

[0055] Examples 12-15

[0056] A preparation process for a carbon nanotube conductive paste differs from Example 1 only in that the grinding times are 20 min (Example 12), 30 min (Example 13), 150 min (Example 14), and 180 min (Example 15), respectively. All other conditions, parameters, and steps are the same as in Example 1.

[0057] Comparative Example 1

[0058] A process for preparing a carbon nanotube conductive paste includes the following steps:

[0059] (1) Mix 5 parts by weight of polyvinylpyrrolidone, 0.05 parts by weight of carboxymethyl cellulose, 5 parts by weight of glycerol and 80 parts by weight of distilled water at a shear rate of 2000 rpm for 40 min to obtain a dispersion.

[0060] (2) The dispersion obtained in step (1) and 25 parts by weight of carbon nanotubes (approximately 80 μm in length) were mixed for 40 min at a shear rate of 2000 rpm to obtain a premixed solution.

[0061] (3) The premixed solution obtained in step (2) is subjected to high-energy dissociation twice under a pressure of 1800 bar to obtain the carbon nanotube conductive slurry.

[0062] Comparative Example 2

[0063] A process for preparing a carbon nanotube conductive paste includes the following steps:

[0064] (1) Mix 5 parts by weight of polyvinylpyrrolidone, 0.05 parts by weight of carboxymethyl cellulose, 5 parts by weight of glycerol and 80 parts by weight of distilled water at a shear rate of 2000 rpm for 40 min to obtain a dispersion.

[0065] (2) The dispersion obtained in step (1) and 25 parts by weight of carbon nanotubes (approximately 80 μm in length) were mixed for 40 min at a shear rate of 2000 rpm to obtain a premixed solution.

[0066] (3) The premixed solution obtained in step (2) is ground for 100 minutes at a speed of 1000 r / min to obtain the carbon nanotube conductive slurry.

[0067] Comparative Example 3

[0068] A process for preparing a carbon nanotube conductive paste includes the following steps:

[0069] (1) Mix 5 parts by weight of polyvinylpyrrolidone, 0.05 parts by weight of carboxymethyl cellulose, 5 parts by weight of glycerol, 80 parts by weight of distilled water and 25 parts by weight of carbon nanotubes (approximately 80 μm in length) at a shear rate of 2000 rpm for 40 min to obtain a premixed solution.

[0070] (2) The premixed solution obtained in step (2) is subjected to high-energy dissociation twice under a pressure of 1800 bar, and then ground for 100 min at a speed of 1000 r / min to obtain the carbon nanotube conductive slurry.

[0071] Application Example 1

[0072] A lithium-ion coin cell battery is prepared by the following process: mixing silicon-carbon in a mass ratio of 92:3:2:3, carbon nanotube conductive slurry obtained in Example 1, CMC and SBR in deionized water to obtain a negative electrode slurry with a solid content of 60%; then coating the obtained negative electrode slurry onto a copper foil with a coating thickness of 200 μm, drying and rolling to obtain a negative electrode sheet, and using a lithium metal sheet as the counter electrode to prepare a coin cell battery.

[0073] Application Examples 2-15

[0074] A lithium-ion battery differs from Application Example 1 only in that the carbon nanotube conductive slurry obtained in Application Examples 2 to 15 is used to replace the carbon nanotube conductive slurry obtained in Example 1. The other components, amounts, and preparation methods are the same as in Application Example 1.

[0075] Comparative Application Examples 1-3

[0076] A lithium-ion battery differs from Application Example 1 only in that the carbon nanotube conductive slurry obtained in Comparative Examples 1 to 3 is used instead of the carbon nanotube conductive slurry obtained in Example 1. The other components, amounts and preparation methods are the same as in Application Example 1.

[0077] Performance testing:

[0078] (1) Viscosity: The viscosity of the carbon nanotube conductive slurries provided in Examples 1-15 and Comparative Examples 1-3 was tested using a rotational viscometer during the storage period of 0-180 days. The viscosity change graphs of the carbon nanotube conductive slurries provided in Examples 1-19 and Comparative Examples 1-3 during the storage period of 0-180 days are shown in the figure below. Figure 1 As shown;

[0079] from Figure 1 It can be seen that the carbon nanotube conductive pastes prepared in Examples 1 to 15 have low viscosity and good stability.

[0080] (2) Cyclic performance test: The lithium-ion coin cells obtained corresponding to Case 1-15 and Comparative Application Examples 1-3 were subjected to cycle performance tests and first charge-discharge tests. The test conditions were 1C constant current constant voltage charging, 1C constant current discharging, and 300 cycles. The test results are shown in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] According to the data in Table 1:

[0085] Because the carbon nanotube conductive slurry prepared by this invention has good dispersibility and excellent conductivity, when applied to lithium batteries, especially lithium batteries with silicon-carbon anodes, it can fully utilize the performance of electrode materials and improve the user experience of lithium batteries.

[0086] Specifically, the lithium-ion coin cells provided in Application Examples 1 to 15 have a cycle capacity retention rate of up to 70% to 91% and a discharge specific capacity of 700 to 893 mAh / g; while the lithium-ion coin cells provided in Application Examples 1 to 3 have a lower cycle capacity retention rate and a lower initial discharge specific capacity.

[0087] The applicant declares that this invention illustrates a carbon nanotube conductive paste, its preparation process, and its application through the above embodiments. However, this invention is not limited to the above process steps, meaning that this invention does not necessarily rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used in this invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A preparation process for a carbon nanotube conductive paste, characterized in that, The preparation process includes the following steps: (1) Mix the dispersant, stabilizer and water to obtain a dispersion; (2) Mix the dispersion obtained in step (1) with carbon nanotubes to obtain a premixed solution; (3) The premixed solution obtained in step (2) is subjected to high-energy dissociation and grinding to obtain the carbon nanotube conductive slurry; The mixing in step (1) is carried out under a shear rate of 1800~2200 rpm; The mixing in step (2) is carried out under a shear rate of 1800~2200 rpm; The grinding speed in step (3) is 800~1200 r / min; The stabilizer includes any one or a combination of at least two of glycerol, cetyltrimethylammonium bromide, polyoxyethylene ether, or styrene-butadiene rubber; The pressure for the high-energy dissociation is 1550~2000 bar; The solid content of the carbon nanotube conductive paste is 20-24%.

2. The preparation process according to claim 1, characterized in that, The content of dispersant in the dispersion is 1 to 10 parts by weight.

3. The preparation process according to claim 1, characterized in that, The dispersant includes any one or a combination of at least two of polyvinylpyrrolidone, carboxymethyl cellulose, carboxymethyl cellulose salt, or polystyrene butadiene.

4. The preparation process according to claim 1, characterized in that, The content of stabilizer in the dispersion is 1 to 10 parts by weight.

5. The preparation process according to claim 1, characterized in that, The water content in the dispersion is 65-97 parts by weight.

6. The preparation process according to claim 1, characterized in that, The mixing time in step (1) is 40~60 min.

7. The preparation process according to claim 1, characterized in that, The carbon nanotubes have a length of 30~100 μm.

8. The preparation process according to claim 1, characterized in that, The mixing time in step (2) is 40~60 min.

9. The preparation process according to claim 1, characterized in that, The number of high-energy dissociations is 1 to 3.

10. The preparation process according to claim 1, characterized in that, The grinding time is 30~160 min.

11. The preparation process according to claim 1, characterized in that, The grinding time is 100-150 min.

12. The preparation process according to claim 1, characterized in that, The preparation process specifically includes the following steps: (1) Mix the dispersant, stabilizer and water at a shear rate of 1800~2200 rpm for 40~60 min to obtain a dispersion; The stabilizer includes any one or a combination of at least two of glycerol, cetyltrimethylammonium bromide, polyoxyethylene ether, or styrene-butadiene rubber; (2) The dispersion obtained in step (1) and carbon nanotubes are mixed at a shear rate of 1800~2200 rpm for 40~60 min to obtain a premixed solution; (3) The premixed solution obtained in step (2) is subjected to high-energy dissociation 1 to 3 times under a pressure of 1550 to 2000 bar, and then ground for 30 to 160 min under a rotation speed of 800 to 1200 r / min to obtain the carbon nanotube conductive slurry. The solid content of the carbon nanotube conductive paste is 20-24%.

13. A carbon nanotube conductive paste, characterized in that, The carbon nanotube conductive paste is prepared using the preparation process described in any one of claims 1 to 12.

14. A negative electrode slurry, characterized in that, The negative electrode slurry comprises a combination of the carbon nanotube conductive slurry as described in claim 13, the negative electrode active material, the binder, and the solvent.

15. The negative electrode slurry according to claim 14, characterized in that, The negative electrode active material includes silicon carbide.

16. A negative electrode sheet, characterized in that, The negative electrode sheet is obtained by coating the negative electrode slurry as described in claim 14 or 15 onto a copper foil and then drying it.

17. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode as described in claim 16.

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