High-solid-content conductive paste master batch and preparation method thereof
By using carbon nanotubes and graphene in conductive pastes and adding appropriate dispersants, combined with ultrasonic stirring, grinding and high-pressure homogenization, the problem of easy agglomeration of carbon nanotubes was solved, the stability and conductivity of high solids content conductive pastes were improved, and the cost was reduced.
Patent Information
- Application Number
- CN202411167852.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-23
- Publication Date
- 2026-03-03
AI Technical Summary
In existing conductive pastes, carbon nanotubes tend to agglomerate, leading to decreased conductivity and shortened lifespan. Furthermore, increasing the solvent content will increase costs and process complexity.
Using carbon nanotubes and graphene as conductive agents, and adding dispersants such as polyvinylidene fluoride, polyvinylpyrrolidone, and sodium hydroxymethyl cellulose, a high-solids-content conductive slurry masterbatch is prepared through ultrasonic stirring, grinding, and high-pressure homogenization to ensure uniform dispersion of carbon nanotubes.
It improves conductivity and battery cycle performance, reduces solvent usage, saves costs, and maintains the stability and long lifespan of conductive pastes.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of conductive paste technology, specifically to a high-solids-content conductive paste masterbatch and its preparation method. Background Technology
[0002] Conductive pastes are widely used in the battery field, and adding them can improve the conductivity of battery electrode materials. Commonly used conductive agents in conductive pastes include carbon nanofibers, conductive carbon black, carbon nanotubes, and acetylene black. Carbon nanotubes are a highly promising one-dimensional nanomaterial with a diameter typically ranging from 2 to 50 nm and a length from 10 to 50 μm, making them an excellent conductive agent. Carbon nanotubes not only act as conductors in conductive networks but also exhibit the double-layer effect and the high-rate characteristics of supercapacitors. Simultaneously, the excellent thermal conductivity of carbon nanotubes facilitates heat dissipation during battery charging and discharging, reduces battery polarization, improves high and low temperature performance, and extends battery life. However, due to the strong van der Waals forces between carbon nanotubes, they often exist in an aggregated state at the microscopic level, which reduces their conductivity. In addition, the carbon nanotube conductive paste prepared is prone to precipitation due to the re-agglomeration of carbon nanotubes, and in severe cases, stratification occurs, which reduces the service life of the conductive paste. Currently, the shelf life of conductive pastes on the market is generally 6 months, which has seriously limited the long-distance transportation of conductive pastes.
[0003] The existing method to solve the agglomeration of carbon nanotubes is to increase the proportion of solvent in the conductive paste, thereby reducing the agglomeration of carbon nanotubes and improving the dispersibility of carbon nanotubes in the solvent. However, increasing the solvent has created new problems: (1) it increases the cost of raw materials; (2) after the conductive paste and the active material of the lithium battery are combined, the solvent needs to be removed. If the proportion of solvent is too high, it will increase the difficulty of removing the solvent 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-solids-content conductive paste masterbatch and its preparation method, which reduces both carbon nanotube agglomeration and solvent usage, thus saving costs.
[0005] In a first aspect, the present invention provides a high solids content conductive slurry masterbatch, comprising a conductive agent, a solvent, and a dispersant. The conductive agent is composed of carbon nanotubes and graphene, with a mass ratio of carbon nanotubes to graphene of 1:1-2. The solvent is at least one selected from deionized water, N-methylpyrrolidone, and anhydrous ethanol. The dispersant is at least one selected from polyvinylidene fluoride, polyvinylpyrrolidone, and sodium hydroxymethyl cellulose. The mass ratio of the conductive agent, solvent, and dispersant is 21-26:75-80:0.06-0.1.
[0006] Furthermore, the solvent is N-methylpyrrolidone or anhydrous ethanol.
[0007] Furthermore, the dispersant is polyvinylpyrrolidone or a combination of polyvinylpyrrolidone and polyvinylidene fluoride or a combination of polyvinylpyrrolidone and sodium carboxymethyl cellulose.
[0008] Furthermore, the dispersant is a combination of polyvinylpyrrolidone and polyvinylidene fluoride in a mass ratio of 1:1 or a combination of polyvinylpyrrolidone and sodium carboxymethyl cellulose in a mass ratio of 1:1.
[0009] Secondly, the present invention provides a method for preparing a high-solids-content conductive slurry masterbatch, comprising the following steps: (1) Add dispersant and graphene to solvent and ultrasonically stir for 20-30 min to obtain mixed solution A; (2) Mixed solution A was added to carbon nanotubes in batches under intermittent sonication to obtain mixed solution B. The intermittent sonication was 4 min, stopped for 1 min, and repeated 4-5 times. (3) Grind and homogenize the mixed solution B obtained in step (2) one after another to obtain a high solid content conductive slurry masterbatch.
[0010] Furthermore, in steps (1) and (2), the ultrasonic frequency is set to 30KHz and the power to 400W.
[0011] Furthermore, in step (3), a nano-grinding machine is used for grinding, with a rotation speed of 500rpm-2500rpm and a grinding time of 1-3h.
[0012] Furthermore, in step (3), the pressure of high-pressure homogenization is 1000-2000 bar, and the cycle is repeated 2-3 times.
[0013] The beneficial effects of this invention are as follows: The high-solids-content conductive slurry masterbatch provided by this invention has good conductivity, with a conductivity above 2694 S / cm and low viscosity, below 2794 mPa·s. It exhibits good battery cycle performance, with a capacity loss rate of less than 2% after 500 cycles. The dispersant and graphene in the formulation are first added to the solvent system and ultrasonically treated to create an easily dispersed and uniform environment for the subsequently added carbon nanotubes. The carbon nanotubes are added in stages to ensure full wetting. Intermittent ultrasonic treatment can reduce the permanent damage to the high-solids-content conductive slurry masterbatch caused by the cumulative energy of ultrasound. Grinding disperses the carbon nanotubes in the solvent and prevents them from agglomerating. High-pressure homogenization can open the closed ends of the carbon nanotubes, resulting in a more uniform dispersion and lower viscosity of the high-solids-content conductive slurry masterbatch, thereby improving the battery cycle performance. Detailed Implementation
[0014] 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.
[0015] In the following examples and comparative examples, the carbon nanotubes have diameters ranging from 10 to 50 nm and lengths ranging from 15 to 40 μm, and the graphene is a single-layer graphene.
[0016] Example 1 A high-solids-content conductive paste masterbatch is composed of the following raw materials in parts by weight: 10 parts carbon nanotubes, 12 parts graphene, 78 parts anhydrous ethanol, 0.05 parts polyvinylidene fluoride, and 0.05 parts polyvinylpyrrolidone.
[0017] The preparation method of high solids content conductive paste masterbatch is as follows: (1) Add dispersant (a combination of polyvinylpyrrolidone and polyvinylidene fluoride in a mass ratio of 1:1) and graphene to the solvent anhydrous ethanol according to the weight ratio, and ultrasonically stir for 20 min to obtain mixed solution A. The ultrasonic frequency is set to 30KHz and the power is 400W.
[0018] (2) Mixed solution A was added to carbon nanotubes in 4 separate steps under intermittent sonication to obtain mixed solution B. The intermittent sonication method was to sonicate for 4 minutes, stop for 1 minute, and then continue sonication and stop the cycle for 4 times. The sonication frequency was set to 30KHz and the power was 400W. The number of carbon nanotubes added each time was the same, and the carbon nanotubes were added when the sonication stopped.
[0019] (3) Pour the mixed solution B obtained in step (2) into a nano milling machine for grinding. The nano milling machine rotates at 2500 rpm and grinds for 1 hour. Then pour it into a high-pressure homogenizer for high-pressure homogenization at a pressure of 2000 bar. After three cycles, a high-solids-content conductive slurry masterbatch is obtained.
[0020] Example 2 A high-solids-content conductive paste masterbatch is composed of the following raw materials in parts by weight: 7 parts carbon nanotubes, 14 parts graphene, 75 parts N-methylpyrrolidone, 0.03 parts polyvinylidene fluoride, and 0.03 parts polyvinylpyrrolidone.
[0021] The preparation method of high solids content conductive paste masterbatch is as follows: (1) Add dispersant (a combination of polyvinylpyrrolidone and polyvinylidene fluoride in a mass ratio of 1:1) and graphene to the solvent N-methylpyrrolidone according to the weight ratio, and ultrasonically stir for 30 min to obtain mixed solution A. The ultrasonic frequency is set to 30KHz and the power is 400W.
[0022] (2) Mixed solution A was added to carbon nanotubes in 5 separate steps under intermittent sonication to obtain mixed solution B. Intermittent sonication was performed for 4 minutes, followed by a 1-minute pause, and repeated 5 times. The sonication frequency was set to 30 kHz and the power to 400 W. The weight of carbon nanotubes added each time was 1 part, 2 parts, 1 part, 2 parts, and 1 part, respectively. The carbon nanotubes were added when the sonication stopped.
[0023] (3) Pour the mixed solution B obtained in step (2) into a nano milling machine for grinding. The nano milling machine rotates at 500 rpm and grinds for 3 hours. Then pour it into a high-pressure homogenizer for high-pressure homogenization at 1000 bar. After two cycles, a high-solids-content conductive slurry masterbatch is obtained.
[0024] Example 3 A high-solids-content conductive paste masterbatch is composed of the following raw materials in parts by weight: 13 parts carbon nanotubes, 13 parts graphene, 80 parts N-methylpyrrolidone, 0.04 parts polyvinylpyrrolidone, and 0.04 parts sodium carboxymethyl cellulose.
[0025] The preparation method of the high solids content conductive paste masterbatch is the same as in Example 1.
[0026] Example 4 A high-solids-content conductive paste masterbatch is composed of the following raw materials in parts by weight: 10 parts carbon nanotubes, 12 parts graphene, 78 parts anhydrous ethanol, and 0.1 parts polyvinylpyrrolidone.
[0027] The preparation method of the high solids content conductive slurry masterbatch is the same as in Example 1, except that the dispersant added is replaced by polyvinylpyrrolidone instead of the combination of polyvinylidene fluoride and polyvinylidene fluoride in a mass ratio of 1:1.
[0028] Comparative Example 1 A high-solids-content conductive paste masterbatch, with the same raw materials and proportions as in Example 1.
[0029] The preparation method of high solids content conductive paste masterbatch is as follows: (1) Add dispersant (a combination of polyvinylpyrrolidone and polyvinylidene fluoride in a mass ratio of 1:1) to the solvent anhydrous ethanol according to the weight ratio, add carbon nanotubes, and ultrasonically stir for 20 min to obtain mixed solution A. The ultrasonic frequency is set to 30KHz and the power is 400W.
[0030] (2) Mixed solution A was mixed with graphene in 4 separate additions under intermittent sonication to obtain mixed solution B. The intermittent sonication was 4 min, 1 min, and 4 cycles. The sonication frequency was set to 30 kHz and the power was 400 W. The amount of graphene added each time was the same, and the graphene was added when the sonication stopped.
[0031] (3) Pour the mixed solution B obtained in step (2) into a nano milling machine for grinding. The nano milling machine rotates at 2500 rpm and grinds for 1 hour. Then pour it into a high-pressure homogenizer for high-pressure homogenization at a pressure of 2000 bar. After three cycles, a high-solids-content conductive slurry masterbatch is obtained.
[0032] Comparative Example 2 A high-solids-content conductive paste masterbatch, with the same raw materials and proportions as in Example 1.
[0033] The preparation method of high solids content conductive paste masterbatch is as follows: (1) Dispersant (a combination of polyvinylpyrrolidone and polyvinylidene fluoride in a mass ratio of 1:1) and graphene were added to the solvent anhydrous ethanol according to the weight parts. Carbon nanotubes were added in 4 portions and ultrasonically stirred for 40 minutes to obtain a mixed solution. The ultrasonic frequency was set to 30KHz and the power was 400W. The number of carbon nanotubes added each time was the same.
[0034] (2) The mixed solution obtained in step (2) is poured into a nano milling machine for grinding. The nano milling machine rotates at 2500 rpm and grinds for 1 hour. Then it is poured into a high pressure homogenizer for high pressure homogenization at 2000 bar. After three cycles, a high solid content conductive slurry masterbatch is obtained.
[0035] Comparative Example 3 A high-solids-content conductive paste masterbatch, with the same raw materials and proportions as in Example 1.
[0036] The preparation method of high solids content conductive paste masterbatch is as follows: (1) Add dispersant (a combination of polyvinylpyrrolidone and polyvinylidene fluoride in a mass ratio of 1:1) and graphene to the solvent anhydrous ethanol according to the weight ratio, and ultrasonically stir for 20 min to obtain mixed solution A. The ultrasonic frequency is set to 30KHz and the power is 400W.
[0037] (2) Mixed solution A was added to carbon nanotubes in 4 separate steps under intermittent sonication to obtain mixed solution B. Intermittent sonication was performed for 4 minutes, followed by 1 minute of rest, and the cycle was repeated 4 times. The sonication frequency was set to 30 kHz and the power was 400 W. The number of carbon nanotubes added each time was the same, and the carbon nanotubes were added when the sonication stopped.
[0038] (3) Pour the mixed solution B obtained in step (2) into a high-pressure homogenizer for high-pressure homogenization at a pressure of 2000 bar, cycle 3 times, and then pour it into a nano-grinding machine for grinding at a speed of 2500 rpm. After grinding for 1 hour, a high solid content conductive slurry masterbatch is obtained.
[0039] Comparative Example 4 A high-solids-content conductive paste masterbatch is composed of the following raw materials in parts by weight: 10 parts carbon nanotubes, 12 parts graphene, 85 parts anhydrous ethanol, 0.05 parts polyvinylidene fluoride, and 0.05 parts polyvinylpyrrolidone.
[0040] The preparation method of the high solids content conductive paste masterbatch is the same as in Example 1.
[0041] Comparative Example 5 A high-solids-content conductive paste masterbatch is composed of the following raw materials in parts by weight: 10 parts carbon nanotubes, 12 parts graphene, 78 parts anhydrous ethanol, 0.05 parts styrene-butadiene rubber, and 0.05 parts sodium carboxymethyl cellulose.
[0042] The preparation method of the high solids content conductive slurry masterbatch is the same as that in Example 1. The difference from Example 1 is that the dispersant added is replaced by a combination of polyvinylpyrrolidone and polyvinylidene fluoride in a mass ratio of 1:1 with a combination of styrene-butadiene rubber and sodium hydroxymethyl cellulose in a mass ratio of 1:1.
[0043] Comparative Example 6 A high-solids-content conductive paste masterbatch is composed of the following raw materials in parts by weight: 10 parts carbon nanotubes, 12 parts graphene, and 78 parts anhydrous ethanol.
[0044] The preparation method of high solids content conductive slurry masterbatch is the same as that in Example 1, except that no dispersant is added to the solvent in step (1).
[0045] Comparative Example 7 A high-solids-content conductive paste masterbatch is composed of the following raw materials in parts by weight: 22 parts carbon nanotubes, 78 parts anhydrous ethanol, 0.05 parts polyvinylidene fluoride, and 0.05 parts polyvinylpyrrolidone.
[0046] The preparation method of the high solids content conductive slurry masterbatch is the same as that of Example 1, except that graphene is not added to the solvent in step (1).
[0047] Comparative Example 8 A high-solids-content conductive paste masterbatch is composed of the following raw materials in parts by weight: 12 parts carbon nanotubes, 10 parts graphene, 78 parts anhydrous ethanol, 0.05 parts polyvinylidene fluoride, and 0.05 parts polyvinylpyrrolidone.
[0048] The preparation method of the high solids content conductive paste masterbatch is the same as in Example 1.
[0049] Experimental Example 1 Stability test of conductive paste: The high solids content conductive paste masterbatches obtained in Examples 1-4 and Comparative Examples 1-8 were left to stand at room temperature for a certain period of time, and the presence of agglomeration and stratification was observed by visual inspection.
[0050] As shown in Table 1, Comparative Example 6 showed slight stratification visible to the naked eye after standing for 1 month, and Comparative Example 5 showed slight stratification visible to the naked eye after standing for 2 months. No agglomeration or stratification was observed in the other examples and comparative examples. This indicates that whether or not a dispersant is added, and the addition of different types of dispersants, can significantly affect the stability of high solids content conductive slurry masterbatch.
[0051] Table 1. Stability test of high solids content conductive paste masterbatch
[0052] Experiment Example 2 The high-solids-content conductive slurry masterbatches from Examples 1-4, Comparative Examples 1-4, and Comparative Examples 7-8, which did not exhibit agglomeration or stratification after standing for 2 months in Experiment 1, were used as samples for the following tests: (1) Electrical conductivity Each sample was uniformly coated onto a clean 5cm×5cm PET film and dried to obtain a conductive film. The thickness of the conductive film was measured to be 10μm using a micrometer. 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.
[0053] (2) Viscosity test Each sample was tested according to the test method provided in GB / T10247-2008 Viscosity Measurement Method. A Bollerfel rotary viscometer was used for the test at a temperature of 25℃, with a No. 4 rotor and a rotation speed of 60 rpm.
[0054] (3) Performance testing of the manufactured battery Each sample was uniformly coated onto the positive electrode current collector, dried, and then rolled using a conventional mirror milling machine to form a conductive coating with a thickness of 3 μm. The positive electrode slurry was uniformly coated onto the conductive coating, dried, and then rolled using a conventional mirror milling machine to form a positive electrode sheet. The positive electrode sheet was applied to an 18650 lithium battery, and the appearance of the electrode sheet was observed and the battery capacity retention rate was tested after 500 cycles at a discharge rate of 0.2C.
[0055] (4) Experimental results As shown in Table 2, the high-solids-content conductive slurry masterbatches of Examples 1-4 of the present invention have good conductivity, with a conductivity above 2694 S / cm and low viscosity below 2794 mPa·s. They exhibit good battery cycle performance, with a capacity loss rate of less than 2% after 500 cycles. Appropriate amounts of dispersant and graphene are first added to the solvent system and ultrasonicated to create an easily dispersed and uniform environment for the subsequently added appropriate amount of carbon nanotubes. The phased addition allows the low-density, soft carbon nanotubes to be fully immersed in the mixed solution A during ultrasonication. Intermittent ultrasonic treatment reduces the permanent damage to the viscosity of the high-solids-content conductive slurry masterbatch caused by the cumulative energy of ultrasonication. Grinding disperses the carbon nanotubes in the solvent, preventing agglomeration. High-pressure homogenization opens the closed ends of the carbon nanotubes, resulting in more uniform dispersion and lower viscosity of the high-solids-content conductive slurry masterbatch, thereby improving battery cycle performance.
[0056] While the high-solids-content conductive slurry masterbatches in Comparative Examples 3 and 4 exhibited good performance in conductivity, viscosity, and battery cycle performance, the preparation process of Comparative Example 3 involved homogenization followed by grinding. During homogenization, the unevenness of the mixed solution B caused the homogenizer to easily become clogged, affecting preparation efficiency and increasing costs. Comparative Example 4 increased the proportion of solvent used, which made solvent removal more difficult after subsequent mixing with the active materials of the lithium battery, also increasing costs. The performance indicators of Comparative Examples 1, 2, 7, and 8 were significantly worse than those of Examples 1-4. This demonstrates that the composition, ratio, and order of addition of carbon nanotubes and graphene all affect the performance of the high-solids-content conductive slurry masterbatch.
[0057] Table 2 Performance Tests of High Solids Content Conductive Slurry Masterbatch
[0058] 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-solids-content conductive paste masterbatch, characterized in that, It includes a conductive agent, a solvent, and a dispersant. The conductive agent is composed of carbon nanotubes and graphene, with a mass ratio of carbon nanotubes to graphene of 1:1-2. The solvent is at least one of deionized water, N-methylpyrrolidone, and anhydrous ethanol. The dispersant is at least one of polyvinylidene fluoride, polyvinylpyrrolidone, and sodium hydroxymethyl cellulose. The mass ratio of the conductive agent, solvent, and dispersant is 21-26:75-80:0.06-0.
1.
2. The high solids content conductive paste masterbatch as described in claim 1, characterized in that, The solvent is N-methylpyrrolidone or anhydrous ethanol.
3. The high solids content conductive paste masterbatch as described in claim 1, characterized in that, The dispersant is polyvinylpyrrolidone or a combination of polyvinylpyrrolidone and polyvinylidene fluoride or a combination of polyvinylpyrrolidone and sodium hydroxymethyl cellulose.
4. The high solids content conductive paste masterbatch as described in claim 3, characterized in that, The dispersant is a combination of polyvinylpyrrolidone and polyvinylidene fluoride in a mass ratio of 1:1 or a combination of polyvinylpyrrolidone and sodium carboxymethyl cellulose in a mass ratio of 1:
1.
5. A method for preparing a high-solids-content conductive paste masterbatch as described in claim 1, characterized in that, Includes the following steps: (1) Add dispersant and graphene to solvent and ultrasonically stir for 20-30 min to obtain mixed solution A; (2) Mixed solution A was added to carbon nanotubes in batches under intermittent sonication to obtain mixed solution B. The intermittent sonication was 4 min, stopped for 1 min, and repeated 4-5 times. (3) Grind and homogenize the mixed solution B obtained in step (2) one after another to obtain a high solid content conductive slurry masterbatch.
6. The method for preparing high-solids-content conductive paste masterbatch as described in claim 5, characterized in that, In steps (1) and (2), the ultrasonic frequency is set to 30KHz and the power is 400W.
7. The method for preparing high-solids-content conductive paste masterbatch as described in claim 5, characterized in that, In step (3), a nano-grinding machine is used for grinding, with a rotation speed of 500rpm-2500rpm and a grinding time of 1-3h.
8. The method for preparing high-solids-content conductive paste masterbatch as described in claim 5, characterized in that, In step (3), the pressure for high-pressure homogenization is 1000-2000 bar, and the cycle is repeated 2-3 times.