High-concentration dispersion system and preparation method thereof

Abstract

The invention relates to the technical field of conductive materials, in particular to a high-concentration dispersion system and a preparation method thereof. The high-concentration dispersion system comprises a conductive agent, a dispersing agent, a solvent and a viscosity reduction auxiliary agent, the conductive agent is modified carbon nanotubes, the dispersing agent is modified polyvinylpyrrolidone, the solvent is N-methyl pyrrolidone or deionized water, and the viscosity reduction auxiliary agent is piperazine anhydrous; wherein the modified carbon nano tube is obtained by mixing and heating a carbon nano tube and a mixed acid solution of nitric acid and sulfuric acid, then cooling, filtering, washing, drying, then dispersing in 75% ethanol, and finally adding 3-[3-carboxyl allylamido] propyltriethoxysilane for modification; the modified polyvinylpyrrolidone is obtained by heating polyvinylpyrrolidone at 310-330 DEG C and then oxidizing the polyvinylpyrrolidone. The conductive agent content of the high-concentration dispersion system is high, the conductive agent accounts for 15%-20% of the high-concentration dispersion system by mass, and the high-concentration dispersion system is low in viscosity, high in dispersity and good in conductivity.

Description

Technical Field

[0001] This invention relates to the field of conductive materials technology, specifically to a high-concentration dispersion system and its preparation method. Background Technology

[0002] Conductive paste is a dispersion system with electronic functions that integrates materials, chemical engineering, metallurgy, and electronic technology. It is most widely used in lead-acid batteries, sodium-ion batteries, and lithium-ion batteries. By adding this dispersion system, the conductivity of battery electrode materials can be improved. Common conductive agents used in conductive pastes include carbon nanofibers, conductive carbon black, carbon nanotubes, and graphene. Among these, carbon nanotubes, as a novel conductive agent for lithium-ion batteries, can effectively improve the conductivity of lithium-ion batteries, requiring 60%-70% less addition than conventional carbon black, and significantly improving the energy density of lithium-ion batteries. However, carbon nanotubes generally have a diameter of less than 50 nm and a very large aspect ratio, leading to severe agglomeration at the microscopic level. This makes them prone to stratification and precipitation, reducing the uniformity of the conductive paste. Furthermore, after agglomeration, some carbon nanotubes are encapsulated within the agglomeration, reducing the conductivity of the conductive paste, and the viscosity of the conductive paste is also affected.

[0003] The existing method to solve the agglomeration of carbon nanotubes is to increase the solvent to improve the dispersibility of carbon nanotubes in the solvent and reduce the agglomeration of carbon nanotubes. However, the presence of a large amount of solvent has created new problems: (1) it increases the cost of raw materials and the difficulty of transportation; (2) after the conductive paste and the active material of lithium battery are combined, the solvent needs to be removed. If the solvent content is too high, it will increase the difficulty of solvent removal and increase the process cost. Summary of the Invention

[0004] To address the technical problem that high solvent content in existing conductive pastes increases costs, while low solvent content leads to carbon nanotube agglomeration and reduced conductivity, this invention provides a high-concentration dispersion system and its preparation method, which improves the dispersibility of carbon nanotube conductive agents and reduces solvent usage, thus saving costs.

[0005] In a first aspect, the present invention provides a high-concentration dispersion system, comprising a conductive agent, a dispersant, a solvent, and a viscosity-reducing agent, wherein the conductive agent is modified carbon nanotubes, the dispersant is modified polyvinylpyrrolidone, the solvent is N-methylpyrrolidone or deionized water, and the viscosity-reducing agent is anhydrous piperazine. Among them, the modified carbon nanotubes are obtained by mixing carbon nanotubes with a mixed acid solution of nitric acid and sulfuric acid, heating, then cooling, filtering, washing, drying and then dispersing in 75% ethanol, and finally adding 3-[3-carboxyallylamido]propyltriethoxysilane for modification. Modified polyvinylpyrrolidone is obtained by oxidizing polyvinylpyrrolidone after heating at 310-330℃.

[0006] Furthermore, the mass percentage of the conductive agent in the high-concentration dispersion system is 15%-20%.

[0007] Furthermore, the mass ratio of conductive agent, dispersant, viscosity reducer and solvent is 16-20:0.5-3:0.01-1:80-90.

[0008] Furthermore, the mass ratio of the conductive agent, dispersant, viscosity reducer, and solvent is 17:3:1:85.

[0009] Secondly, the present invention provides a method for preparing a high-concentration dispersion system, comprising the following steps: (1) Carbon nanotubes are mixed with a mixed acid solution of nitric acid and sulfuric acid and heated, then cooled, filtered, washed, dried and dispersed in 75% ethanol. Finally, 3-[3-carboxyallylamido]propyltriethoxysilane is added and reacted at 70-80℃ for 2-3 hours. After filtration and drying, modified carbon nanotubes are obtained. (2) Modified polyvinylpyrrolidone is prepared by heating polyvinylpyrrolidone in air to 310-330℃ and holding it at that temperature for 1-5 hours. (3) Modified polyvinylpyrrolidone and modified carbon nanotubes are added to a solvent and homogenized to perform a first mixing process to obtain a first mixed slurry; (4) Add the viscosity reducer to the first mixture and then use a homogenizer for a second mixing process to obtain a high concentration dispersion system.

[0010] Furthermore, in step (1), the mixed acid solution is prepared by mixing 35% nitric acid and 70% sulfuric acid in a mass ratio of 1:1.

[0011] Furthermore, in step (1), the mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and 3-[3-carboxyallylamamido]propyltriethoxysilane is 16-20:900-1000:50-55:1-1.5.

[0012] Furthermore, in step (3), the homogenization is carried out for 5-8 cycles at a homogenization pressure of 130-150 MPa.

[0013] Furthermore, in step (4), the homogenization is carried out for 4-5 cycles at a homogenization pressure of 80-100 MPa.

[0014] The beneficial effects of this invention are as follows: The high-concentration dispersion system provided by this invention has a high conductive agent content, accounting for 15%-20% of the mass of the high-concentration dispersion system. It also exhibits low viscosity, strong dispersibility, and good conductivity. Specifically, 3-[3-carboxyallylamamido]propyltriethoxysilane is used to modify carbon nanotubes, which helps to improve the uniform dispersion of carbon nanotubes in the plasma and reduce agglomeration. Adding modified polyvinylpyrrolidone as a dispersant can increase the content of modified carbon nanotubes in the conductive paste, increasing the solid content to over 15%. The conductive paste raw materials are homogenized twice using a high-pressure homogenizer, which can effectively break up the agglomerated modified carbon nanotubes, thereby improving the wetting and surface adsorption of the conductive agent by the solvent and dispersant, further improving the dispersibility of the high-concentration conductive agent. Adding a small amount of anhydrous piperazine, a viscosity-reducing agent, lowers the viscosity of the conductive paste, improves its fluidity, and can further increase the content of modified carbon nanotubes in the conductive paste. Detailed Implementation

[0015] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0016] Example 1 A high-concentration dispersion system, comprising the following parts by weight of raw materials: 20 parts by weight of modified carbon nanotubes, 0.5 parts by weight of modified polyvinylpyrrolidone, 0.05 parts by weight of anhydrous piperazine and 80 parts by weight of N-methylpyrrolidone.

[0017] The preparation method of the high-concentration dispersion system is as follows: (1) At room temperature, carbon nanotubes and a mixed acid solution (35% nitric acid and 70% sulfuric acid mixed in a mass ratio of 1:1) were mixed in an ultrasonic instrument with an ultrasonic power of 400W and an ultrasonic frequency of 50kHz. The mixture was heated to 100℃ and then heated for 3h. After cooling, filtering, washing, and drying, the mixture was dispersed in 75% ethanol. Then, 3-[3-carboxyallylamido]propyltriethoxysilane was added and reacted at 70℃ for 3h. After filtering and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and 3-[3-carboxyallylamido]propyltriethoxysilane was 20:1000:55:1. (2) Polyvinylpyrrolidone is heated to 320°C in air and kept at that temperature for 2 hours to partially oxidize it and form modified polyvinylpyrrolidone. (3) Modified polyvinylpyrrolidone and modified carbon nanotubes were added to N-methylpyrrolidone and homogenized to obtain the first mixing slurry. The mixture was homogenized for 5 cycles at a homogenization pressure of 150 MPa. (4) Add anhydrous piperazine to the first mixed slurry, and then use a homogenizer for a second mixing process. Homogenize for 5 cycles at a homogenization pressure of 80 MPa to obtain conductive slurry.

[0018] Example 2 A high-concentration dispersion system, comprising the following parts by weight of raw materials: 16 parts by weight of modified carbon nanotubes, 0.9 parts by weight of modified polyvinylpyrrolidone, 0.01 parts by weight of anhydrous piperazine and 90 parts by weight of N-methylpyrrolidone.

[0019] The preparation method of the high-concentration dispersion system is as follows: (1) At room temperature, carbon nanotubes and a mixed acid solution (35% nitric acid and 70% sulfuric acid mixed in a mass ratio of 1:1) were mixed in an ultrasonic instrument with an ultrasonic power of 400W and an ultrasonic frequency of 50kHz. The mixture was heated to 100℃ and then heated for 2h. After cooling, filtering, washing, and drying, the mixture was dispersed in 75% ethanol. Then, 3-[3-carboxyallylamido]propyltriethoxysilane was added and reacted at 80℃ for 2h. After filtering and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and 3-[3-carboxyallylamido]propyltriethoxysilane was 16:900:50:1. (2) Polyvinylpyrrolidone is heated to 310°C in air and kept at that temperature for 5 hours to partially oxidize it and form modified polyvinylpyrrolidone. (3) Modified polyvinylpyrrolidone and modified carbon nanotubes were added to deionized water and homogenized to obtain the first mixed slurry. The mixture was circulated and homogenized for 7 cycles at a homogenization pressure of 140 MPa. (4) Add anhydrous piperazine to the first mixed slurry, and then use a homogenizer for the second mixing process. Homogenize for 4 cycles at a homogenization pressure of 90 MPa to obtain conductive slurry.

[0020] Example 3 A high-concentration dispersion system, comprising the following parts by weight of raw materials: 17 parts by weight of modified carbon nanotubes, 3 parts by weight of modified polyvinylpyrrolidone, 1 part by weight of anhydrous piperazine and 85 parts by weight of N-methylpyrrolidone.

[0021] The preparation method of the high-concentration dispersion system is as follows: (1) At room temperature, carbon nanotubes and a mixed acid solution (35% nitric acid and 70% sulfuric acid mixed in a mass ratio of 1:1) were mixed in an ultrasonic instrument with an ultrasonic power of 400W and an ultrasonic frequency of 50kHz. The mixture was heated to 100℃ and then heated for 3h. After cooling, filtering, washing, drying, and dispersing in 75% ethanol, 3-[3-carboxyallylamido]propyltriethoxysilane was added. The mixture was reacted at 70℃ for 3h, filtered, and dried to obtain modified carbon nanotubes. The mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and 3-[3-carboxyallylamido]propyltriethoxysilane was 17:950:55:1.5. (2) Polyvinylpyrrolidone is heated to 330°C in air and kept at that temperature for 1 hour to partially oxidize it and form modified polyvinylpyrrolidone. (3) Modified polyvinylpyrrolidone and modified carbon nanotubes were added to N-methylpyrrolidone and homogenized to obtain the first mixing slurry. The mixture was homogenized for 8 cycles at a homogenization pressure of 130 MPa. (4) Add anhydrous piperazine to the first mixed slurry, and then use a homogenizer for a second mixing process. Homogenize for 4 cycles at a homogenization pressure of 100 MPa to obtain conductive slurry.

[0022] Comparative Example 1 A dispersion system comprising the following parts by weight of raw materials: 17 parts by weight of modified carbon nanotubes, 3 parts by weight of modified polyvinylpyrrolidone, 1 part by weight of anhydrous piperazine and 85 parts by weight of N-methylpyrrolidone.

[0023] The preparation method of the dispersion system is as follows: (1) At room temperature, carbon nanotubes and a mixed acid solution (35% nitric acid and 70% sulfuric acid mixed in a mass ratio of 1:1) were mixed in an ultrasonic instrument with an ultrasonic power of 400W and an ultrasonic frequency of 50kHz. The mixture was heated to 100℃ and then heated for 3h. After cooling, filtering, washing, drying, and dispersing in 75% ethanol, a modifier was added. The mixture was reacted at 70℃ for 3h, filtered, and dried to obtain modified carbon nanotubes. The mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and modifier was 17:950:55:1.5. The modifier was a mixture of N-(6-aminohexyl)aminomethyltriethoxysilane and 3-[3-carboxyallylamido]propyltriethoxysilane in a mass ratio of 2:3. (2) Polyvinylpyrrolidone is heated to 330°C in air and kept at that temperature for 1 hour to partially oxidize it and form modified polyvinylpyrrolidone. (3) Modified polyvinylpyrrolidone and modified carbon nanotubes were added to N-methylpyrrolidone and homogenized to obtain the first mixing slurry. The mixture was homogenized for 8 cycles at a homogenization pressure of 130 MPa. (4) Add anhydrous piperazine to the first mixed slurry, and then use a homogenizer for a second mixing process. Homogenize for 4 cycles at a homogenization pressure of 100 MPa to obtain conductive slurry.

[0024] Comparative Example 2 A dispersion system comprising the following parts by weight of raw materials: 17 parts by weight of modified carbon nanotubes, 3 parts by weight of modified polyvinylpyrrolidone, 1 part by weight of anhydrous piperazine and 85 parts by weight of N-methylpyrrolidone.

[0025] The preparation method of the dispersion system is as follows: (1) At room temperature, carbon nanotubes and a mixed acid solution (35% nitric acid and 70% sulfuric acid mixed in a mass ratio of 1:1) were mixed in an ultrasonic instrument with an ultrasonic power of 400W and an ultrasonic frequency of 50kHz. The mixture was heated to 100℃ and then heated for 3h. After cooling, filtering, washing, drying, and dispersing in 75% ethanol, 3-[3-carboxyallylamido]propyltriethoxysilane was added. The mixture was reacted at 70℃ for 3h, filtered, and dried to obtain modified carbon nanotubes. The mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and 3-[3-carboxyallylamido]propyltriethoxysilane was 17:950:55:1.5. (2) Polyvinylpyrrolidone is heated to 300°C in air and kept at that temperature for 1 hour to partially oxidize it and form modified polyvinylpyrrolidone. (3) Modified polyvinylpyrrolidone and modified carbon nanotubes were added to N-methylpyrrolidone and homogenized to obtain the first mixing slurry. The mixture was homogenized for 8 cycles at a homogenization pressure of 130 MPa. (4) Add anhydrous piperazine to the first mixed slurry, and then use a homogenizer for a second mixing process. Homogenize for 4 cycles at a homogenization pressure of 100 MPa to obtain conductive slurry.

[0026] Comparative Example 3 A high-concentration dispersion system, comprising the following parts by weight of raw materials: 17 parts by weight of modified carbon nanotubes, 3 parts by weight of modified polyvinylpyrrolidone, 1 part by weight of anhydrous piperazine and 85 parts by weight of N-methylpyrrolidone.

[0027] The preparation method of the high-concentration dispersion system is as follows: (1) At room temperature, carbon nanotubes and a mixed acid solution (35% nitric acid and 70% sulfuric acid mixed in a mass ratio of 1:1) were mixed in an ultrasonic instrument with an ultrasonic power of 400W and an ultrasonic frequency of 50kHz. The mixture was heated to 100℃ and then heated for 3h. After cooling, filtering, washing, drying, and dispersing in 75% ethanol, 3-[3-carboxyallylamido]propyltriethoxysilane was added. The mixture was reacted at 70℃ for 3h, filtered, and dried to obtain modified carbon nanotubes. The mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and 3-[3-carboxyallylamido]propyltriethoxysilane was 17:950:55:1.5. (2) Polyvinylpyrrolidone is heated to 330°C in air and kept at that temperature for 1 hour to partially oxidize it and form modified polyvinylpyrrolidone. (3) Modified polyvinylpyrrolidone and modified carbon nanotubes were added to N-methylpyrrolidone and mixed using a homogenizer to obtain conductive slurry. The homogenizer was circulated for 8 cycles and the homogenization pressure was 130 MPa.

[0028] Comparative Example 4 A high-concentration dispersion system, comprising the following parts by weight of raw materials: 17 parts by weight of modified carbon nanotubes, 3 parts by weight of modified polyvinylpyrrolidone, 1 part by weight of anhydrous piperazine and 85 parts by weight of N-methylpyrrolidone.

[0029] The preparation method of the high-concentration dispersion system is as follows: (1) At room temperature, carbon nanotubes and a mixed acid solution (35% nitric acid and 70% sulfuric acid mixed in a mass ratio of 1:1) were mixed in an ultrasonic instrument with an ultrasonic power of 400W and an ultrasonic frequency of 50kHz. The mixture was heated to 100℃ and then heated for 3h. After cooling, filtering, washing, drying, and dispersing in 75% ethanol, 3-[3-carboxyallylamido]propyltriethoxysilane was added. The mixture was reacted at 70℃ for 3h, filtered, and dried to obtain modified carbon nanotubes. The mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and 3-[3-carboxyallylamido]propyltriethoxysilane was 17:950:55:1.5. (2) Polyvinylpyrrolidone is heated to 330°C in air and kept at that temperature for 1 hour to partially oxidize it and form modified polyvinylpyrrolidone. (3) Modified polyvinylpyrrolidone, modified carbon nanotubes and anhydrous piperazine were added to N-methylpyrrolidone and dispersed using a grinding mill for 4 hours to obtain conductive slurry. The frequency of the grinding mill was 40 Hz.

[0030] Comparative Example 5 A high-concentration dispersion system, comprising the following parts by weight of raw materials: The composition consists of 17 parts by weight of carbon nanotubes, 3 parts by weight of polyvinylpyrrolidone, 1 part by weight of anhydrous piperazine, and 85 parts by weight of N-methylpyrrolidone.

[0031] The preparation method of the high-concentration dispersion system is as follows: (1) Polyvinylpyrrolidone and carbon nanotubes were added to N-methylpyrrolidone and homogenized to obtain a first mixing slurry. The mixture was homogenized for 8 cycles at a homogenization pressure of 130 MPa. (2) Add anhydrous piperazine to the first mixed slurry, and then use a homogenizer for the second mixing process. Homogenize for 4 cycles at a homogenization pressure of 100 MPa to obtain conductive slurry.

[0032] Comparative Example 6 A high-concentration dispersion system, comprising the following parts by weight of raw materials: 17 parts by weight of modified carbon nanotubes, 3 parts by weight of polyvinylpyrrolidone, 1 part by weight of anhydrous piperazine and 85 parts by weight of N-methylpyrrolidone.

[0033] The preparation method of the high-concentration dispersion system is as follows: (1) At room temperature, carbon nanotubes and a mixed acid solution (35% nitric acid and 70% sulfuric acid mixed in a mass ratio of 1:1) were mixed in an ultrasonic instrument with an ultrasonic power of 400W and an ultrasonic frequency of 50kHz. The mixture was heated to 100℃ and then heated for 3h. After cooling, filtering, washing, drying, and dispersing in 75% ethanol, 3-[3-carboxyallylamido]propyltriethoxysilane was added. The mixture was reacted at 70℃ for 3h, filtered, and dried to obtain modified carbon nanotubes. The mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and 3-[3-carboxyallylamido]propyltriethoxysilane was 17:950:55:1.5. (2) Polyvinylpyrrolidone and modified carbon nanotubes were added to N-methylpyrrolidone and homogenized to obtain a first mixing slurry. The mixture was homogenized for 8 cycles at a homogenization pressure of 130 MPa. (3) Add anhydrous piperazine to the first mixed slurry, and then use a homogenizer for a second mixing process. Homogenize for 4 cycles at a homogenization pressure of 100 MPa to obtain conductive slurry.

[0034] Comparative Example 7 A high-concentration dispersion system, comprising the following parts by weight of raw materials: The composition consists of 17 parts by weight of carbon nanotubes, 3 parts by weight of modified polyvinylpyrrolidone, 1 part by weight of anhydrous piperazine, and 85 parts by weight of N-methylpyrrolidone.

[0035] The preparation method of the high-concentration dispersion system is as follows: (1) Polyvinylpyrrolidone is heated to 330°C in air and kept at that temperature for 1 hour to partially oxidize it and form modified polyvinylpyrrolidone. (2) Modified polyvinylpyrrolidone and carbon nanotubes were added to N-methylpyrrolidone and homogenized to obtain a first mixing slurry. The mixture was circulated for 8 cycles and the homogenization pressure was 130 MPa. (3) Add anhydrous piperazine to the first mixed slurry, and then use a homogenizer for a second mixing process. Homogenize for 4 cycles at a homogenization pressure of 100 MPa to obtain conductive slurry.

[0036] Experiment Example 1 Performance Testing (1) Electrical conductivity The high-concentration dispersion systems of the above embodiments and comparative examples were uniformly coated on a clean 5cm×5cm PET film and dried to obtain conductive films. The thickness of the conductive film was measured to be 10 micrometers using a micrometer screw gauge. After the obtained conductive film was rolled, the conductivity of the film layer was measured using a four-probe tester. Six different points on the conductive film layer were randomly selected, with a probe spacing of 2mm. The average value was taken after six measurements.

[0037] (2) Viscosity test The high-concentration dispersion systems of the examples and comparative examples were tested according to the test methods provided in GB / T10247-2008 Viscosity Measurement Method. A Bollerfeld rotary viscometer was used for the test at a temperature of 25°C, with a No. 4 rotor and a rotation speed of 60 rpm.

[0038] (3) Performance testing of the manufactured battery The high-concentration dispersion systems of the examples and comparative examples were uniformly coated onto the positive electrode current collector. After drying, they were rolled using a conventional mirror milling machine to form a conductive coating with a thickness of 3 micrometers. The positive electrode slurry was uniformly coated onto the conductive coating, dried, and then rolled using a conventional mirror milling machine to produce a positive electrode sheet. The positive electrode sheet was applied to an 18650 lithium battery, and the appearance of the electrode sheet was observed. The battery capacity retention rate was tested after 500 cycles at a discharge rate of 0.2C.

[0039] (4) Experimental results As shown in Table 1, the high-concentration dispersion systems of Examples 1-3 of this invention exhibit good conductivity, with a conductivity exceeding 2691 S / cm. In contrast, the high-concentration dispersion systems using only modified carbon nanotubes (Comparative Example 6), only modified polyvinylpyrrolidone (Comparative Example 7), or both using only conventional carbon nanotubes and polyvinylpyrrolidone (Comparative Example 5) show significantly lower conductivity, below 1695 S / cm. Furthermore, the high-concentration dispersion systems obtained without homogenization (Comparative Example 4), without adding viscosity-reducing agents and only performing a single mixing process using a homogenizer (Comparative Example 3), or with altered modifier formulations (Comparative Example 1), or with altered heating temperatures (Comparative Example 2) all exhibited lower conductivity than those of Examples 1-3. This indicates that, under certain proportions, the modified conductive agent and dispersant work together, and the high-concentration dispersion system obtained through two mixing processes using a homogenizer exhibits superior conductivity.

[0040] The conductive agent mass percentages in Examples 3 and Comparative Examples 1-7 are the same, but the lower viscosity of the high-concentration dispersion system in Example 3 indicates better dispersion and superior performance of the conductive agent. The high-concentration dispersion systems in Examples 1-3 and Comparative Examples 1-2 are very smooth when coated on the positive electrode surface, indicating that modifying the raw materials and homogenizing twice with a homogenizer can improve the smoothness of the positive electrode surface, which is beneficial for improving the uniform dispersion of the conductive agent in the high-concentration dispersion system, reducing agglomeration, and forming a uniform network structure. In terms of battery cycle performance, the high-concentration dispersion system in Examples 1-3 performs better, with a capacity loss rate of less than 2% after 500 cycles.

[0041] Table 1 Performance tests of conductive pastes in the examples and comparative examples

[0042] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A high-concentration dispersion system, characterized in that, It includes a conductive agent, a dispersant, a solvent, and a viscosity reducer. The conductive agent is modified carbon nanotubes, the dispersant is modified polyvinylpyrrolidone, the solvent is N-methylpyrrolidone or deionized water, and the viscosity reducer is anhydrous piperazine. Among them, the modified carbon nanotubes are obtained by mixing carbon nanotubes with a mixed acid solution of nitric acid and sulfuric acid, heating, then cooling, filtering, washing, drying and then dispersing in 75% ethanol, and finally adding 3-[3-carboxyallylamido]propyltriethoxysilane for modification. Modified polyvinylpyrrolidone is obtained by oxidizing polyvinylpyrrolidone after heating at 310-330℃.

2. The high-concentration dispersion system as described in claim 1, characterized in that, The mass percentage of conductive agent in a high-concentration dispersion system is 15%-20%.

3. The high-concentration dispersion system as described in claim 1, characterized in that, The mass ratio of conductive agent, dispersant, viscosity reducer and solvent is 16-20:0.5-3:0.01-1:80-90.

4. The high-concentration dispersion system as described in claim 3, characterized in that, The mass ratio of conductive agent, dispersant, viscosity reducer and solvent is 17:3:1:

85.

5. A method for preparing the high-concentration dispersion system as described in claim 1, characterized in that, Includes the following steps: (1) Carbon nanotubes are mixed with a mixed acid solution of nitric acid and sulfuric acid and heated, then cooled, filtered, washed, dried and dispersed in 75% ethanol. Finally, 3-[3-carboxyallylamido]propyltriethoxysilane is added and reacted at 70-80℃ for 2-3 hours. After filtration and drying, modified carbon nanotubes are obtained. (2) Modified polyvinylpyrrolidone is prepared by heating polyvinylpyrrolidone in air to 310-330℃ and holding it at that temperature for 1-5 hours. (3) Modified polyvinylpyrrolidone and modified carbon nanotubes are added to a solvent and homogenized to perform a first mixing process to obtain a first mixed slurry; (4) Add the viscosity reducer to the first mixture and then use a homogenizer for a second mixing process to obtain a high concentration dispersion system.

6. The method for preparing the high-concentration dispersion system as described in claim 5, characterized in that, In step (1), the mixed acid solution is prepared by mixing 35% nitric acid and 70% sulfuric acid in a mass ratio of 1:

1.

7. The method for preparing the high-concentration dispersion system as described in claim 5, characterized in that, In step (1), the mass ratio of carbon nanotubes, mixed acid solution, 75% ethanol and 3-[3-carboxyallylamamido]propyltriethoxysilane is 16-20:900-1000:50-55:1-1.

5.

8. The method for preparing the high-concentration dispersion system as described in claim 5, characterized in that, In step (3), the homogenization is carried out for 5-8 cycles at a pressure of 130-150 MPa.

9. The method for preparing the high-concentration dispersion system as described in claim 5, characterized in that, In step (4), the homogenization is carried out for 4-5 cycles, and the homogenization pressure is 80-100MPa.

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