Single-walled carbon nanotube conductive paste, preparation method and application thereof

Abstract

The application provides a single-walled carbon nanotube conductive slurry and a preparation method and application thereof. The preparation method comprises the following steps: firstly, mixing a stabilizer and single-walled carbon nanotubes in water step by step to obtain a premix; then, adding a surfactant into the premix to perform high-pressure dispersion and grinding, and repeating the step of adding the surfactant to perform high-pressure dispersion and grinding until the viscosity of the mixture reaches the maximum, so that the single-walled carbon nanotube conductive slurry which is uniformly dispersed and stable can be obtained; the preparation method adopts a combination of high-pressure dispersion and grinding, and the two processes are alternately performed, so that the single-walled carbon nanotubes are dispersed in multiple dimensions, the single-walled carbon nanotube conductive slurry which is uniformly dispersed and stable is obtained, and the single-walled carbon nanotube conductive slurry can be applied to a silicon-carbon, silicon-oxygen and graphite negative electrode system to reduce the resistance of the system and greatly improve the rate performance and cycle performance of the battery.

Description

Technical Field

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

[0002] Single-walled carbon nanotube (SWNT) conductive pastes possess unparalleled conductivity, along with high strength, high flexibility, and a high aspect ratio. They also exhibit the ability to form a well-developed conductive network within the material even with low dosages. Furthermore, when introduced into silicon anodes, SWNTs can cover the surface of silicon particles and establish highly conductive and durable connections between them. These connections are extremely tight, long-lasting, conductive, and robust. Even when silicon anode particles expand and begin to crack, they maintain a strong connection through the SWNTs, preventing anode material breakage. Under these conditions, the silicon anode exhibits excellent cycle life, sufficient to meet the most stringent requirements of electric vehicle manufacturers. Currently, SWNTs have shown potential applications in numerous fields, including nanoelectronic devices, energy storage devices, and structural and functional composite materials.

[0003] However, due to the strong van der Waals forces between single-walled carbon nanotubes and their large aspect ratio, they often form large bundles that are difficult to disperse, greatly limiting their superior performance and practical applications. Therefore, developing high aspect ratio, easily dispersible single-walled carbon nanotube conductive paste products is more in line with the development trend of the lithium battery industry and meets market demand. CN112803025A discloses a method for preparing single-walled carbon nanotube conductive paste, including the following steps: taking single-walled carbon nanotubes, dispersant, and deionized water, and using a pipeline device to pre-disperse the single-walled carbon nanotubes, dispersant, and deionized water to obtain a first dispersion system; and subjecting the first dispersion system to high-pressure dispersion under a pressure of 50-300 MPa to obtain the single-walled carbon nanotube conductive paste. This method uses a conventional high-pressure dispersion process, which fails to find the optimal dispersion point, resulting in an unsatisfactory dispersion effect in the final prepared single-walled carbon nanotube conductive paste.

[0004] Therefore, developing a new preparation method to prepare a uniformly dispersed and stable single-walled carbon nanotube conductive slurry is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a single-walled carbon nanotube conductive paste, its preparation method, and its application. The preparation method employs a combination of high-pressure dispersion and grinding, using these two processes alternately to disperse the single-walled carbon nanotubes in multiple dimensions, resulting in a uniformly dispersed and stable single-walled carbon nanotube conductive paste. When applied to anode systems such as silicon-carbon, silicon-oxygen, and graphite, it can reduce the system's resistance and significantly improve the rate performance and cycle performance of the battery.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a conductive paste made of single-walled carbon nanotubes, the method comprising the following steps:

[0008] (1) Mix the stabilizer and water, then add single-walled carbon nanotubes and mix to obtain a premix;

[0009] (2) Add a surfactant to the premix obtained in step (1) and perform high-pressure dispersion and grinding to obtain a mixture;

[0010] (3) Repeat step (2) of adding surfactant for high-pressure dispersion and grinding until the viscosity of the mixture reaches its maximum, to obtain the single-walled carbon nanotube conductive slurry.

[0011] The preparation method provided by the present invention firstly mixes a stabilizer and single-walled carbon nanotubes in water in steps to obtain a premix. Then, a surfactant is added to the obtained premix for high-pressure dispersion and grinding to obtain a mixture. The steps of adding surfactant and high-pressure dispersion and grinding are repeated, and the dispersion and grinding processes are repeated alternately until the viscosity of the mixture reaches the maximum, so as to obtain a uniformly dispersed and stable single-walled carbon nanotube conductive slurry. This invention employs a processing method that primarily utilizes high-pressure discrete processing, supplemented by grinding and dispersion. The two processes are alternated for dispersion, utilizing these two different dispersion methods to disperse carbon nanotubes in multiple dimensions. The optimal dispersion point (the point of highest viscosity) is found based on the viscosity change trend of the mixture after multiple discrete and milling processes. Simultaneously, the discrete process allows the fluid material to disperse from the agglomerates under the influence of cavitation forces. Under multiple high-pressure discrete processes, each additional appropriate amount of surfactant enters the agglomerates and fully contacts the carbon nanotube surface under the influence of cavitation forces. This allows the surfactant in the slurry to be fully adsorbed onto the carbon nanotube surface. Through electrostatic repulsion and steric hindrance effects, the carbon nanotubes are stably dispersed in the polar solvent. This preparation method effectively disperses single-walled carbon nanotubes in an aqueous system, obtaining a uniformly dispersed and stable conductive slurry of single-walled carbon nanotubes. When applied to silicon-carbon, silicon-oxygen, and graphite anode systems, it can reduce system resistance and significantly improve battery rate performance and cycle performance.

[0012] It should be noted that the way to determine the maximum viscosity of the mixture in step (3) of the preparation method provided by the present invention is that the viscosity of the mixture begins to decrease.

[0013] In this invention, "high pressure discrete" refers to a discrete pressure of not less than 1000 bar.

[0014] Preferably, the stabilizer in step (1) includes sodium carboxymethyl cellulose.

[0015] Preferably, step (1) involves mixing the stabilizer and water in a premixer.

[0016] Preferably, the rotational speed of the premixer is 800-1200 rpm, such as 840 rpm, 880 rpm, 920 rpm, 960 rpm, 1000 rpm, 1040 rpm, 1080 rpm, 1120 rpm, or 1160 rpm.

[0017] Preferably, the flow rate of the premixer is 400-600 L / min, such as 420 L / min, 440 L / min, 460 L / min, 480 L / min, 500 L / min, 520 L / min, 540 L / min, 560 L / min or 580 L / min.

[0018] Preferably, the mixing time for mixing the stabilizer and water in step (1) is 20 to 40 minutes, such as 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, 32 minutes, 34 minutes, 36 minutes, or 38 minutes.

[0019] Preferably, the addition of single-walled carbon nanotubes in step (1) and the mixing are carried out in a premixer.

[0020] Preferably, the rotational speed of the premixer is 800-1200 rpm, such as 840 rpm, 880 rpm, 920 rpm, 960 rpm, 1000 rpm, 1040 rpm, 1080 rpm, 1120 rpm, or 1160 rpm.

[0021] Preferably, the flow rate of the premixer is 200-400 L / min, such as 220 L / min, 240 L / min, 260 L / min, 280 L / min, 300 L / min, 320 L / min, 340 L / min, 360 L / min or 380 L / min.

[0022] Preferably, the mixing time for adding single-walled carbon nanotubes in step (1) is 50 to 70 minutes, such as 52 minutes, 54 minutes, 56 minutes, 58 minutes, 60 minutes, 62 minutes, 64 minutes, 66 minutes, or 68 minutes.

[0023] Preferably, the diameter of the single-walled carbon nanotube is 1 to 3 nm, such as 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm, 2 nm, 2.2 nm, 2.4 nm, 2.6 nm or 2.8 nm.

[0024] Preferably, the length of the single-walled carbon nanotube is greater than 50 μm, such as 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm or 59 μm.

[0025] Preferably, the surfactant comprises hexadecyltrimethylammonium bromide.

[0026] Preferably, the discrete pressure of the high-pressure discrete in step (2) is 1100 to 1300 bar, such as 1120 bar, 1140 bar, 1160 bar, 1180 bar, 1200 bar, 1220 bar, 1240 bar, 1260 bar or 1280 bar.

[0027] As a preferred technical solution of the present invention, the dispersion pressure of high-pressure dispersion is limited to 1100-1300 bar. If the dispersion pressure is higher than 1300 bar, the length of carbon nanotubes will be severely broken; if the dispersion pressure is lower than 1100 bar, the dispersion effect will be unsatisfactory.

[0028] Preferably, the number of grinding times in step (2) is no less than 4 times, such as 5 times, 6 times, 7 times, 8 times or 9 times.

[0029] Preferably, the grinding speed in step (2) is 600 to 800 rpm, such as 620 rpm, 640 rpm, 660 rpm, 680 rpm, 700 rpm, 720 rpm, 740 rpm, 760 rpm or 780 rpm.

[0030] As a preferred technical solution, the preparation method includes the following steps:

[0031] (1) Mix the stabilizer and water in a premix at a speed of 800-1200 rpm and a flow rate of 400-600 L / min for 20-40 min, add single-walled carbon nanotubes with a diameter of 1-3 nm and a length greater than 50 μm, and continue mixing at a speed of 800-1200 rpm and a flow rate of 200-400 L / min for 50-70 min to obtain the premix.

[0032] (2) Add a surfactant to the premix obtained in step (1), perform high-pressure dispersion under a dispersion pressure of 1100 to 1300 bar, and then grind at least 4 times under a rotation speed of 600 to 800 rpm to obtain a mixture.

[0033] (3) Repeat step (2) of adding surfactant for high-pressure dispersion and grinding until the viscosity of the mixture reaches its maximum, to obtain the single-walled carbon nanotube conductive slurry.

[0034] In a second aspect, the present invention provides a single-walled carbon nanotube conductive paste, which is prepared by the preparation method described in the first aspect.

[0035] Preferably, the stabilizer content in the single-walled carbon nanotube conductive slurry is 1 to 5 parts by weight, such as 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, or 5 parts by weight.

[0036] Preferably, the content of single-walled carbon nanotubes in the single-walled carbon nanotube conductive paste is 2 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, 9 parts by weight, or 10 parts by weight.

[0037] Preferably, the surfactant content in the single-walled carbon nanotube conductive slurry is 1 to 3 parts by weight, such as 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.2 parts by weight, 2.4 parts by weight, 2.6 parts by weight, or 2.8 parts by weight.

[0038] Preferably, the water content in the single-walled carbon nanotube conductive slurry is 200 to 1200 parts by weight, such as 200 parts by weight, 300 parts by weight, 400 parts by weight, 500 parts by weight, 600 parts by weight, 700 parts by weight, 800 parts by weight, 900 parts by weight, 1000 parts by weight, 1100 parts by weight, or 1200 parts by weight.

[0039] Thirdly, the present invention provides an application of the single-walled carbon nanotube conductive paste as described in the second aspect in anode materials.

[0040] Preferably, the active material of the negative electrode material includes any one or a combination of at least two of silicon-carbon, silicon-oxygen, or graphite.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The purpose of this invention is to provide a method for preparing a single-walled carbon nanotube conductive slurry. The preparation method firstly mixes a stabilizer and single-walled carbon nanotubes in water stepwise to obtain a premix. Then, a surfactant is added to the premix for high-pressure dispersion and grinding. The steps of adding surfactant and high-pressure dispersion and grinding are repeated until the viscosity of the mixture reaches its maximum, thereby obtaining a uniformly dispersed and stable single-walled carbon nanotube conductive slurry. The preparation method adopts a combination of high-pressure dispersion and grinding, and the two processes are carried out alternately to disperse the single-walled carbon nanotubes in multiple dimensions, resulting in a uniformly dispersed and stable single-walled carbon nanotube conductive slurry. When applied to anode systems such as silicon-carbon, silicon-oxygen, and graphite, it can reduce the resistance of the system and greatly improve the rate performance and cycle performance of the battery.

[0043] (2) Specifically, the resistivity of the negative electrode sheet prepared by the single-walled carbon nanotube conductive paste prepared by the preparation method provided by the present invention is 47.4 to 48.9 Ω·cm. The battery can be further prepared and the capacity retention rate after 100 cycles is 93.5 to 96.2%, and the capacity retention rate under the rate performance test conditions of 0.3C to 5C is 78.4 to 80.6%. Attached Figure Description

[0044] Figure 1 Scanning electron microscope image of single-walled carbon nanotube powder;

[0045] Figure 2 The image shows a scanning electron microscope (SEM) image of the negative electrode slurry obtained in Application Example 1.

[0046] Figure 3 A scanning electron microscope image of the negative electrode slurry obtained in Application Example 2;

[0047] Figure 4 Scanning electron microscope image of the negative electrode slurry obtained in Application Example 3;

[0048] Figure 5 A scanning electron microscope image of the negative electrode slurry obtained in Application Example 4;

[0049] Figure 6 Scanning electron microscope image of the negative electrode slurry obtained in Application Example 5;

[0050] Figure 7 A scanning electron microscope image of the negative electrode slurry obtained in Example 6;

[0051] Figure 8Scanning electron microscope image of the negative electrode slurry obtained in Example 7;

[0052] Figure 9 For comparison, see the scanning electron microscope image of the negative electrode slurry obtained in Application Example 1;

[0053] Figure 10 For comparison, see the scanning electron microscope image of the negative electrode slurry obtained in Application Example 2;

[0054] Figure 11 For comparison, see the scanning electron microscope image of the negative electrode slurry obtained in Application Example 3;

[0055] Figure 12 The scanning electron microscope image of the negative electrode slurry obtained in Application Example 4 is shown for comparison. Detailed Implementation

[0056] 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.

[0057] Example 1

[0058] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps:

[0059] (1) 2 parts by weight of sodium carboxymethyl cellulose and 1200 parts by weight of water were premixed in a premixer at a speed of 1000 rpm and a flow rate of 500 L / min for 30 min. Then, 10 parts by weight of single-walled carbon nanotubes (diameter of 1-3 nm and length of 50-80 μm) were added and the mixture was premixed in a premixer at a speed of 1000 rpm and a flow rate of 300 L / min for another 60 min to obtain a premix.

[0060] (2) Add 2 parts by weight of hexadecyltrimethylammonium bromide to the premix obtained in step (1), perform high pressure dispersion under a dispersion pressure of 1200 bar, and then grind it 5 times under a rotation speed of 700 rpm to obtain a mixture.

[0061] (3) Repeat step (2) of adding hexadecyltrimethylammonium bromide for dispersion and grinding three times, and test the viscosity of the mixture to reach the highest level to obtain the single-walled carbon nanotube conductive slurry.

[0062] Example 2

[0063] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps:

[0064] (1) 2 parts by weight of sodium carboxymethyl cellulose and 1200 parts by weight of water were premixed in a premixer at 800 rpm and 400 L / min for 20 min. Then, 10 parts by weight of single-walled carbon nanotubes (diameter 1-3 nm and length 50-80 μm) were added and the mixture was premixed in a premixer at 800 rpm and 200 L / min for another 50 min to obtain a premix.

[0065] (2) Add 2 parts by weight of hexadecyltrimethylammonium bromide to the premix obtained in step (1), perform high pressure dispersion under a dispersion pressure of 1100 bar, and then grind it 5 times under a rotation speed of 600 rpm to obtain a mixture.

[0066] (3) Repeat step (2) five times to add hexadecyltrimethylammonium bromide for dispersion and grinding. Test the viscosity of the mixture to reach the highest value to obtain the single-walled carbon nanotube conductive slurry.

[0067] Example 3

[0068] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps:

[0069] (1) 2 parts by weight of sodium carboxymethyl cellulose and 1200 parts by weight of water were premixed in a premixer at a speed of 1200 rpm and a flow rate of 600 L / min for 40 min. Then, 10 parts by weight of single-walled carbon nanotubes (diameter of 1-3 nm and length of 50-80 μm) were added and the mixture was premixed in a premixer at a speed of 1200 rpm and a flow rate of 400 L / min for another 70 min to obtain the premix.

[0070] (2) Add 2 parts by weight of hexadecyltrimethylammonium bromide to the premix obtained in step (1) and mix. Discretize under a discrete pressure of 1300 bar and grind 5 times at a speed of 800 rpm to obtain a mixture.

[0071] (3) Repeat step (2) twice to add hexadecyltrimethylammonium bromide for dispersion and grinding. Test the viscosity of the mixture to reach the highest value to obtain the single-walled carbon nanotube conductive slurry.

[0072] Example 4

[0073] A method for preparing a single-walled carbon nanotube conductive paste, which differs from Example 1 only in that the discrete pressure in step (2) is 1100 bar, and step (3) is repeated 4 times to test the viscosity of the mixture to reach the highest level, thereby obtaining the single-walled carbon nanotube conductive paste.

[0074] Example 5

[0075] A method for preparing a single-walled carbon nanotube conductive paste, which differs from Example 1 only in that the discrete pressure in step (2) is 1300 bar, and step (3) is repeated twice to test the viscosity of the mixture to reach the highest level, thereby obtaining the single-walled carbon nanotube conductive paste.

[0076] Example 6

[0077] A method for preparing a single-walled carbon nanotube conductive paste, which differs from Example 1 only in that the discrete pressure in step (2) is 1000 bar, and step (3) is repeated 6 times to test the viscosity of the mixture to reach the highest level, thereby obtaining the single-walled carbon nanotube conductive paste.

[0078] Example 7

[0079] A method for preparing a single-walled carbon nanotube conductive paste, which differs from Example 1 only in that the discrete pressure in step (2) is 1500 bar, and step (3) is repeated once to test the viscosity of the mixture to reach its maximum, thereby obtaining the single-walled carbon nanotube conductive paste.

[0080] Comparative Example 1

[0081] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps:

[0082] (1) 2 parts by weight of sodium carboxymethyl cellulose and 1200 parts by weight of water were premixed in a premixer at a speed of 1000 rpm and a flow rate of 500 L / min for 30 min. Then, 10 parts by weight of single-walled carbon nanotubes (diameter of 1-3 nm and length of 50-80 μm) were added and the mixture was premixed in a premixer at a speed of 1000 rpm and a flow rate of 300 L / min for another 60 min to obtain a premix.

[0083] (2) Add 2 parts by weight of hexadecyltrimethylammonium bromide to the premix obtained in step (1), perform high pressure dispersion under a dispersion pressure of 1200 bar, and then grind 5 times under a rotation speed of 700 rpm to obtain the single-walled carbon nanotube conductive slurry.

[0084] Comparative Example 2

[0085] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps:

[0086] (1) 2 parts by weight of sodium carboxymethyl cellulose and 1200 parts by weight of water were premixed in a premixer at a speed of 1000 rpm and a flow rate of 500 L / min for 30 min. 10 parts by weight of single-walled carbon nanotubes (the diameter of the single-walled carbon nanotubes is 1-3 nm and the length is 50-80 μm) were added and the mixture was premixed in a premixer at a speed of 1000 rpm and a flow rate of 300 L / min for another 60 min to obtain the premix.

[0087] (2) Add 2 parts by weight of the surfactant cetyltrimethylammonium bromide to the premix obtained in step (1), perform high pressure dispersion 3 times under a dispersion pressure of 1200 bar, and then grind 15 times under a rotation speed of 700 rpm to obtain the single-walled carbon nanotube conductive slurry.

[0088] Comparative Example 3

[0089] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps:

[0090] (1) 2 parts by weight of sodium carboxymethyl cellulose and 1200 parts by weight of water were premixed in a premixer at a speed of 1000 rpm and a flow rate of 500 L / min for 30 min. 10 parts by weight of single-walled carbon nanotubes (the diameter of the single-walled carbon nanotubes is 1-3 nm and the length is 50-80 μm) were added and the mixture was premixed in a premixer at a speed of 1000 rpm and a flow rate of 300 L / min for another 60 min to obtain the premix.

[0091] (2) Add 2 parts by weight of the surfactant cetyltrimethylammonium bromide to the premix obtained in step (1) to obtain a mixture;

[0092] (3) Discretize the mixture obtained in step (2) under a discrete pressure of 1200 bar, and then grind it 5 times at a speed of 700 rpm.

[0093] (4) Repeat step (3) 3 times to obtain the single-walled carbon nanotube conductive slurry.

[0094] Comparative Example 4

[0095] A method for preparing a single-walled carbon nanotube conductive paste includes the following steps:

[0096] (1) 2 parts by weight of sodium carboxymethyl cellulose and 1200 parts by weight of water were premixed in a premixer at a speed of 1000 rpm and a flow rate of 500 L / min for 30 min. 10 parts by weight of single-walled carbon nanotubes (the diameter of the single-walled carbon nanotubes is 1-3 nm and the length is 50-80 μm) were added and the mixture was premixed in a premixer at a speed of 1000 rpm and a flow rate of 300 L / min for another 60 min to obtain the premix.

[0097] (2) Add 2 parts by weight of the surfactant cetyltrimethylammonium bromide to the premix obtained in step (1) and grind it 15 times at a speed of 700 rpm to obtain the single-walled carbon nanotube conductive slurry.

[0098] Application Example 1

[0099] A negative electrode slurry with a solid content of 45% comprises graphite, SBR, CMC and single-walled carbon nanotube conductive slurry in a mass ratio of 95.5:2.5:1.2:0.8 (Example 1);

[0100] The method for preparing the negative electrode slurry includes: stirring graphite, SBR (Japan Ayuron, SN-307R), CMC (Japan Paper, MAC500LC) and single-walled carbon nanotube conductive slurry evenly in water to obtain the negative electrode slurry.

[0101] Application Examples 2-7

[0102] A negative electrode paste, which differs from Application Example 1 only in that the single-walled carbon nanotube conductive paste obtained in Examples 2 to 7 is used to replace the single-walled carbon nanotube conductive paste obtained in Example 1, while the other structures and parameters are the same as in Application Example 1.

[0103] Application Example 8

[0104] A lithium-ion battery, wherein the battery prepared by this invention is a button cell, and its preparation process includes the following steps:

[0105] (1) The negative electrode slurry obtained in the application example is coated on copper foil to obtain a negative electrode sheet; the positive electrode uses a lithium sheet as the counter electrode.

[0106] (2) Assemble the negative electrode shell, negative electrode sheet, separator, electrolyte, lithium sheet, gasket, spring sheet, and positive electrode shell in the order from bottom to top, and then seal them to obtain a button half-cell. The battery is tested after standing for 24 hours. Battery model: CR2025.

[0107] Application Examples 9-14

[0108] A lithium-ion battery differs from Application Example 8 only in that the negative electrode slurry obtained in Application Examples 1 to 7 is used to replace the negative electrode slurry obtained in Application Example 1. All other structures and parameters are the same as in Application Example 8.

[0109] Comparative Application Examples 1-4

[0110] A negative electrode paste, which differs from Application Example 1 only in that the single-walled carbon nanotube conductive paste obtained in Comparative Examples 1 to 5 is used instead of the single-walled carbon nanotube conductive paste obtained in Example 1, while the other structures and parameters are the same as in Application Example 1.

[0111] Comparative Application Examples 5-8

[0112] A lithium-ion battery differs from Application Example 8 only in that the negative electrode slurry obtained in Application Example 1 is replaced with the negative electrode slurry obtained in Comparative Application Examples 1 to 4, while the other structures and parameters are the same as in Application Example 8.

[0113] Performance testing:

[0114] (1) Morphology testing: The single-walled carbon nanotube powder was tested using a scanning electron microscope (model: Regulus 8100). Figure 1 It can be seen that the single-walled carbon nanotubes used in the examples and comparative examples have a diameter of about 1 to 3 nm and a length of about 50 to 80 μm.

[0115] The negative electrode slurries obtained in Application Examples 1-7 and Comparative Application Examples 1-4 were tested using a scanning electron microscope (model: Regulus 8100). The scanning electron microscope images of the negative electrode slurries provided in Application Examples 1-7 and Comparative Application Examples 1-4 are shown below. Figures 2-12 As shown: From Figures 2-8 It can be seen that the carbon nanotubes are uniformly dispersed in the negative electrode slurries prepared by Examples 1-7, while from... Figures 9-12 It can be seen that the carbon nanotubes in the negative electrode slurry prepared in comparison Examples 1 to 4 have poor dispersion.

[0116] (2) Viscosity: The viscosity of the carbon nanotube conductive slurry was tested using a DV2T viscometer. The test conditions were: using a No. 3 rotor and a rotation speed of 12 rpm.

[0117] (3) Electrode resistivity test method: A slurry system with graphite:SBR:CMC:conductive paste = 95.5:2.5:1.2:0.8 and solid content of 45% was used. The mixture was homogenized at 2000 rpm for 15 min. The homogenized paste was then coated onto the PI film with a thickness of 200 μm and dried at 140℃ for 1 hour. Finally, the electrode resistivity was tested using a four-probe resistivity tester (model: RTS-8).

[0118] The carbon nanotube conductive pastes provided in Examples 1-7 and Comparative Examples 1-4 were tested according to the above test methods. The test results are shown in Table 1.

[0119] Table 1

[0120]

[0121] According to the data in Table 1:

[0122] (1) By using a combination of high-pressure dispersion and grinding, and alternating between the two processes, and repeatedly adding surfactant, the viscosity of the carbon nanotubes in the produced single-walled carbon nanotube aqueous conductive slurry is higher than that of the single-walled carbon nanotube aqueous conductive slurry prepared under the same conditions: high or low pressure of high-pressure dispersion (Examples 6-7), no repeated addition of surfactant, high-pressure dispersion and grinding process (Comparative Example 1), high-pressure dispersion and sand milling process completed in one step (Comparative Example 2), no repeated addition of surfactant (Comparative Example 3), and no high-pressure dispersion process (Comparative Example 4). The higher viscosity indicates that the carbon nanotubes have a better dispersion effect.

[0123] (2) By combining high-pressure dispersion and grinding, and alternating between the two processes, and repeatedly adding surfactant, the carbon nanotube dispersion uniformity of the produced single-walled carbon nanotube aqueous conductive slurry is better than that of the single-walled carbon nanotube aqueous conductive slurry prepared under the same conditions where the high-pressure dispersion pressure is too high or too low (Examples 6-7), no surfactant is added repeatedly, high-pressure dispersion and grinding process (Comparative Example 1), high-pressure dispersion and sand milling process is completed in one step (Comparative Example 2), no surfactant is added repeatedly (Comparative Example 3), and no high-pressure dispersion process is used (Comparative Example 4). Specifically, the resistivity of the electrode is better. Specifically, the resistivity of the electrode prepared by using the single-walled carbon nanotube aqueous conductive slurry obtained in Examples 1-5 is 47.4-48.9 Ω·cm.

[0124] (3) Cyclic performance: The test was conducted using the Xinwei test system (CT-4008-5V50mA) under the following conditions: constant current and constant voltage charging at 0.3C, constant current discharging at 0.5C, and capacity retention after 100 cycles.

[0125] (4) Rate performance: The test system (CT-4008-5V50mA) was used. The test conditions were constant current and constant voltage charging at 0.3C, and constant current discharging at 0.3, 0.5, 1, 2, 3 and 5C respectively. The rate performance was expressed as the capacity retention rate under the conditions from 0.3C to 5C.

[0126] The lithium-ion batteries obtained according to the above test methods and corresponding test cases 8-14 and comparative application examples 5-8 were tested. The test results are shown in Table 2.

[0127] Table 2

[0128]

[0129]

[0130] According to the data in Table 2:

[0131] By employing a combination of high-pressure dispersion and grinding, alternating between the two processes, and repeatedly adding surfactants, the resulting aqueous conductive slurry containing single-walled carbon nanotubes was used to prepare button-type lithium-ion half-cells with excellent rate and cycle performance. Furthermore, by controlling the high-pressure dispersion pressure to 1100–1300 bar, the cycle and rate performance of the prepared button-type lithium-ion half-cells could be further improved. Specifically, the button-type lithium-ion half-cells obtained in Examples 1–5 exhibited a capacity retention of 93.5–96.2% after 100 cycles in cycle performance testing, and a capacity retention of 78.4–80.6% under rate performance testing conditions from 0.3C to 5C.

[0132] Comparing application examples 6-7 and comparative application examples 5-8, it can be seen that the cycle performance and rate performance of button lithium-ion half-cells prepared by high-pressure dispersion pressure being too high or too low, or by high-pressure dispersion and sand milling processes being completed in one step or not repeated, by adding surfactants, or by not using high-pressure dispersion processes are all reduced.

[0133] The applicant declares that this invention illustrates a single-walled carbon nanotube conductive paste, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A method for preparing a single-walled carbon nanotube conductive paste, characterized in that, The preparation method includes the following steps: (1) Mix the stabilizer and water, then add single-walled carbon nanotubes and mix to obtain a premix; (2) Add a surfactant to the premix obtained in step (1) and perform high-pressure dispersion and grinding to obtain a mixture; (3) Repeat step (2) of adding surfactant for high-pressure dispersion and grinding until the viscosity of the mixture reaches its maximum, to obtain the single-walled carbon nanotube conductive slurry; The single-walled carbon nanotube conductive slurry contains 1-5 parts by weight of stabilizer, 2-10 parts by weight of single-walled carbon nanotubes, 1-3 parts by weight of surfactant, and 200-1200 parts by weight of water. The stabilizer includes sodium carboxymethyl cellulose; The surfactant includes hexadecyltrimethylammonium bromide; The discrete pressure of the high-pressure discrete step (2) is 1100~1300 bar; The grinding process in step (2) shall be performed at least four times; The way to determine in step (3) that the viscosity of the mixture reaches its maximum is when the viscosity of the mixture begins to decrease.

2. The preparation method according to claim 1, characterized in that, Step (1) involves mixing the stabilizer and water in a premixer.

3. The preparation method according to claim 2, characterized in that, The premixer operates at a speed of 800~1200 rpm.

4. The preparation method according to claim 2, characterized in that, The flow rate of the premixer is 400~600 L / min.

5. The preparation method according to claim 1, characterized in that, The mixing time for step (1) of mixing the stabilizer and water is 20-40 min.

6. The preparation method according to claim 1, characterized in that, Step (1) involves adding single-walled carbon nanotubes and mixing them in a premixer.

7. The preparation method according to claim 6, characterized in that, The premixer operates at a speed of 800~1200 rpm.

8. The preparation method according to claim 6, characterized in that, The flow rate of the premixer is 200~400 L / min.

9. The preparation method according to claim 1, characterized in that, The mixing time for adding single-walled carbon nanotubes in step (1) is 50-70 min.

10. The preparation method according to claim 1, characterized in that, The diameter of the single-walled carbon nanotubes is 1~3 nm.

11. The preparation method according to claim 1, characterized in that, The length of the single-walled carbon nanotube is greater than 50 μm.

12. The preparation method according to claim 1, characterized in that, The grinding speed in step (2) is 600~800 rpm.

13. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) Mix the stabilizer and water in a premixer at a speed of 800-1200 rpm and a flow rate of 400-600 L / min for 20-40 min, add single-walled carbon nanotubes with a diameter of 1-3 nm and a length greater than 50 μm, and continue mixing at a speed of 800-1200 rpm and a flow rate of 200-400 L / min for 50-70 min to obtain a premix; (2) Add surfactant to the premix obtained in step (1), disperse it under a dispersion pressure of 1100~1300 bar, and then grind it at a speed of 600~800 rpm for no less than 4 times to obtain a mixture; (3) Repeat step (2) of adding surfactant for high-pressure dispersion and grinding until the viscosity of the mixture reaches its maximum, to obtain the single-walled carbon nanotube conductive slurry; The way to determine in step (3) that the viscosity of the mixture reaches its maximum is when the viscosity of the mixture begins to decrease.

14. A single-walled carbon nanotube conductive paste, characterized in that, The single-walled carbon nanotube conductive paste is prepared by the preparation method described in any one of claims 1 to 13; The single-walled carbon nanotube conductive slurry contains 1-5 parts by weight of stabilizer, 2-10 parts by weight of single-walled carbon nanotubes, 1-3 parts by weight of surfactant, and 200-1200 parts by weight of water.

15. The application of the single-walled carbon nanotube conductive paste as described in claim 14 in anode materials.

16. The application according to claim 15, characterized in that, The active material in the negative electrode material includes any one or a combination of at least two of silicon-carbon, silicon-oxygen, or graphite.

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