Preparation method of modified nanocarbon material and lithium ion battery

Abstract

The application discloses a preparation method of modified nanometer carbon material and a lithium ion battery. An equipment for implementing the preparation method comprises a feeding machine, an air flow pulverizer and a magnetic field removing machine arranged in sequence along a material running direction, and the air flow pulverizer and the magnetic field removing machine are arranged in sequence from top to bottom along a height direction. The preparation method comprises the following steps: in step 1, nanometer carbon material and modified material are mixed according to a mass ratio of 100:0.1-5, and then the mixture is fed into the air flow pulverizer through the feeding machine, wherein the modified material comprises a polymer and a small molecule amine, and the mass ratio of the polymer to the small molecule amine is 100:5-10; and in step 2, after the material is pulverized by the air flow pulverizer, the material is fed into the magnetic field removing machine in a free fall mode under the action of gravity to remove the magnetic field. The nanometer carbon material has better dispersity and lower metal impurity content.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a method for preparing modified nano-carbon materials and a lithium-ion battery. Background Technology

[0002] Nanocarbon materials refer to carbon materials with at least one dimension of size less than 1000nm. Although the primary particle size (i.e., the original particle size or initial particle size) is very small, due to the π-π conjugated bonds between the nanocarbon material particles, the particles tend to agglomerate together. When combined with other materials, they often clump together, causing uneven distribution, material blockage, and performance degradation. At the same time, nanocarbon materials themselves have small particle size and low density, making them prone to floating and generating dust, which makes it difficult to filter and remove impurities.

[0003] See Figure 5 As shown, in the prior art, after the nano-carbon material comes out of the hopper 7 after the air jet mill, it is fed into the demagnetizer 8 by the screw feeder 10. After being demagnetized by the demagnetizer 8, it enters the finished product hopper 9. The nano-carbon material is squeezed during screw feeding and is prone to clumping. The screw feeding is uneven each time, which may cause material blockage. In addition, the screw device itself is made of metal, and friction with the nano-carbon material during the feeding process will introduce additional metal impurities.

[0004] To demagnetize nano-carbon materials, a negative pressure suction method can be used to send the nano-carbon materials into the demagnetizer. However, this method causes the nano-carbon materials to pass through the demagnetizer quickly, resulting in a short time for the nano-carbon materials to be attracted by the magnetic field in the demagnetizer, poor demagnetization effect, and uneven demagnetization. Summary of the Invention

[0005] This application provides a modified carbon nanomaterial and its preparation method, which can improve the dispersibility of the carbon nanomaterial, control the appropriate particle size and density, reduce dust, make it easy to transport, and at the same time improve the demagnetization effect.

[0006] A method for preparing modified carbon nanomaterials, wherein the equipment for implementing the preparation method includes: a feeder, an air jet mill, and a demagnetizer arranged sequentially along the material travel direction, wherein the air jet mill and the demagnetizer are arranged sequentially from top to bottom along the height direction;

[0007] The preparation method includes:

[0008] Step 1: The nano-carbon material and the modified material are mixed at a mass ratio of 100:0.1 to 5 and then fed into the air jet mill through a feeder. The modified material includes polymers and small molecule amines, and the mass ratio of polymers to small molecule amines is 100:5 to 10.

[0009] The polymer is one of hydrogenated nitrile butadiene rubber, polyvinylpyrrolidone, ethyl cellulose, cellulose acetate ester, polyvinyl butyral, ethylene-vinyl alcohol polymer, and methacrylate-acrylate block copolymer;

[0010] The small molecule amine is one of anhydrous piperazine, isopropanolamine, ethanolamine, hydroxyethylhydrazine, isobutanolamine, triethylamine, and methyl hydrazine carbamate;

[0011] Step 2: After the material is pulverized by the air jet mill, it enters the demagnetizer by free fall under the action of gravity for demagnetization; the pulverization temperature in the air jet mill is 30-60℃.

[0012] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0013] Optionally, a permanent magnet demagnetizing device is provided between the feeder and the airflow pulverizer. The permanent magnet rods of the permanent magnet demagnetizing device have a magnetic force of 10,000 to 12,000 GS and a gap of 5 to 10 cm.

[0014] Optionally, the air jet mill has a pulverizing frequency of 10-50Hz, an air pressure of 6-10MPa, an internal structure made of ceramic, and an inlet temperature of 40-120℃.

[0015] Optionally, a disperser is provided between the air jet mill and the demagnetizer. After the material is pulverized by the air jet mill, it is dispersed by the disperser and then enters the demagnetizer by free fall.

[0016] Optionally, the material falls to a height of at least 3m after entering the demagnetizer and falling freely.

[0017] Optionally, the disperser has at least two outlets, each outlet connected to a demagnetizer.

[0018] Optionally, the demagnetizer has an inlet at the top and an outlet at the bottom. The interior of the demagnetizer has at least one demagnetizing channel arranged vertically, with a height of at least 3m. The inlet of the demagnetizer is connected to the disperser via a pipe, and the angle between the axis of the pipe and the horizontal plane is 45° to 60°.

[0019] Optionally, the inlet of the demagnetizer is located below the outlet of the disperser, and the height difference between the inlet of the demagnetizer and the outlet of the disperser is at least 1.5m.

[0020] Optionally, the equipment is installed on a steel structure frame, which includes: columns and at least two support layers fixed to the columns, wherein the first support layer is 4-5m above the ground and the second support layer is 7-8m above the ground. The demagnetizer is fixedly installed on the first support layer, and the feeder, air jet mill and disperser are installed on the second support layer.

[0021] This application also provides a lithium-ion battery in which the modified nano-carbon material is added as a dispersant in the lithium-ion battery slurry.

[0022] The method for preparing modified carbon nanomaterials provided in this application can continuously produce carbon nanomaterials with controllable particle size and low metal impurity content, with a production efficiency of 200-300 kg / h. Attached Figure Description

[0023] Figure 1 This is a front view of the equipment used to prepare the modified carbon nanomaterials according to this application;

[0024] Figure 2 A front view of the apparatus for preparing modified carbon nanomaterials according to this application (and) Figure 1 (Same perspective, steel structure frame omitted);

[0025] Figure 3 Side view of the equipment used to prepare the modified carbon nanomaterials in this application;

[0026] Figure 4 Side view of the apparatus used to prepare the modified carbon nanomaterials for this application (and) Figure 3 (Same perspective, steel structure frame omitted);

[0027] Figure 5 A schematic diagram of the manufacturing of nano-carbon materials in existing technologies;

[0028] Figure 6 The particle size distribution of the acetylene black powder prepared in Example 1 is shown below.

[0029] Figure 7 The particle size distribution of the carbon nanotube powder prepared in Example 2 is shown below.

[0030] Figure 8 The particle size distribution of the graphite micropowder prepared in Example 3 is shown in the diagram.

[0031] Figure 9 The particle size distribution of the graphite micropowder prepared in Example 4 is shown in the diagram.

[0032] Figure 10 The particle size distribution of the graphite micropowder prepared in Example 5 is shown in the diagram.

[0033] Figure 11 The particle size distribution of the acetylene black powder prepared in Comparative Example 1 is shown.

[0034] Figure 12 SEM image of the acetylene carbon black powder prepared in Example 1;

[0035] Figure 13 SEM image of the carbon nanotube powder prepared in Example 2;

[0036] Figure 14 SEM image of the graphite micropowder prepared in Example 3;

[0037] Figure 15 SEM image of the graphite micropowder prepared in Example 4;

[0038] Figure 16 SEM image of the graphite micropowder prepared in Example 5;

[0039] Figure 17 SEM image of the acetylene carbon black powder prepared in Comparative Example 1.

[0040] Figure 18 The particle size distribution of the acetylene carbon black slurry prepared in Example 1 is shown.

[0041] Figure 19 The particle size distribution of the carbon nanotube slurry prepared in Example 2 is shown.

[0042] Figure 20 The particle size distribution of the graphite slurry prepared in Example 3 is shown.

[0043] Figure 21 The particle size distribution of the graphite slurry prepared in Application Example 4 is shown.

[0044] Figure 22 The particle size distribution of the graphite slurry prepared in Example 5 is shown.

[0045] Figure 23 The particle size distribution of the acetylene carbon black slurry prepared in Example 4 is shown.

[0046] In the diagram: 1. Air jet mill; 2. Disperser; 3. Demagnetizer; 4. Finished product silo; 5. Packaging machine; 6. Pipeline; 7. Material silo; 8. Demagnetizer; 9. Finished product silo; 10. Screw feeder; 11. Column; 12. First support layer; 13. Second support layer. Detailed Implementation

[0047] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0048] To better describe and illustrate the embodiments of this application, reference may be made to one or more accompanying drawings, but the additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the inventive creations of this application, the embodiments or preferred methods described herein.

[0049] It should be noted that when a component is said to be "connected" to another component, it can be directly connected to the other component or it can be connected to a component in between. When a component is said to be "set on" another component, it can be directly set on the other component or it may be set to a component in between.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0051] A method for preparing modified carbon nanomaterials, see [link to relevant documentation]. Figures 1-4 As shown, the equipment for implementing the preparation method includes: a feeder, an air jet mill 1, and a demagnetizer 3 arranged sequentially along the material travel direction, with the air jet mill 1 and the demagnetizer 3 arranged sequentially from top to bottom along the height direction; the preparation method includes:

[0052] Step 1: The nano-carbon material and the modified material are mixed at a mass ratio of 100:0.1 to 5 and then fed into the air jet mill 1 through a feeder. The modified material includes polymer and small molecule amine, and the mass ratio of polymer to small molecule amine is 100:5 to 10.

[0053] The polymer is one of hydrogenated nitrile butadiene rubber, polyvinylpyrrolidone, ethyl cellulose, cellulose acetate ester, polyvinyl butyral, ethylene-vinyl alcohol polymer, and methacrylate-acrylate block copolymer;

[0054] The small molecule amine is one of anhydrous piperazine, isopropanolamine, ethanolamine, hydroxyethyl hydrazine, isobutanolamine, triethylamine, and methyl hydrazine carbamate (CAS: 6294-89-9);

[0055] Step 2: After the material is pulverized by the air jet mill 1, it enters the demagnetizer 3 by free fall under the action of gravity for demagnetization; the pulverization temperature in the air jet mill 1 is 30-60℃.

[0056] This application utilizes modified materials to physically modify the surface of nano-carbon materials, enabling the nano-carbon materials to have good dispersibility. At the same time, it improves the processing equipment for nano-carbon materials, which can continuously produce nano-carbon materials with controllable particle size and low metal impurity content, with a production efficiency of 200-300 kg / h.

[0057] After the nano-carbon material and the modified material are mixed, they are fed into the air jet mill. During the mixing process, the polymer and small molecules are first fully mixed and then used as the modified material. Then, they are mixed with the nano-carbon material. The polymer is mixed with the small molecule amine in the form of powder. The particle size of the polymer powder is 10μm to 500μm. After the polymer powder and the small molecule amine are mixed, the small molecule amine is liquid and the amount used is small. On the one hand, it avoids the agglomeration of the polymer powder. On the other hand, based on the dissolving effect of the small molecule amine on the polymer powder, the polymer powder will appear to be in a moist state. This state is not obvious when observed with the naked eye, but the addition of small molecule amine at least plays a role in dissolving and wetting the surface of part of the polymer.

[0058] The pulverizing temperature of the air jet mill is controlled between 30 and 60°C. The pulverizing temperature of the air jet mill can be controlled by introducing a high-temperature airflow. The modified material and the nano-carbon material are fully mixed and pulverized inside the air jet mill. The high-temperature and high-pressure airflow can break up the agglomerates of the nano-carbon material. At the same time as the air jet mill, the presence of the modified material in the pulverizing chamber of the air jet mill prevents the nano-carbon material from agglomerating again.

[0059] In this application, the amount of polymer added is relatively small. Due to the presence of small molecule amines, at least part of the surface of the polymer is dissolved and wetted, which will have a certain adhesive effect on the fine powder in the nano-carbon material.

[0060] This application uses a modifier to modify the nano-carbon material in order to make its particle size uniform, that is, to simultaneously reduce the aggregation of large particles and the fine powder of small particles, specifically manifested as D 90 Decrease, D 10 Add, in this application, D 90 The reduction is mainly due to the pulverization of large nano-carbon material aggregates within the air jet mill, reducing their particle size. Simultaneously, the presence of polymers in the system prevents the nano-carbon materials from re-aggregating. Meanwhile, D... 10 The increase is achieved by the adhesion of fine powder by polymers that wet small molecules.

[0061] In this application, the actual process within the air jet mill is a dynamic equilibrium process. On one hand, the viscosity of some polymer surfaces promotes the aggregation of nano-carbon materials; on the other hand, the air jet mill simultaneously performs continuous pulverization, preventing the aggregation of nano-carbon materials, ultimately achieving D. 90 Decrease, D 10The enhanced effect depends on the precise control of the amount of polymer and small molecule amine added to the modified material. The amount of small molecule amine added cannot be too large, otherwise more polymer powder will become sticky due to the addition of small molecule amine, which will cause more nano-carbon materials to be adhered, resulting in an increase in particle size. The amount of small molecule amine added cannot be too small either, as too little may cause some small nano-carbon materials to fail to adhere.

[0062] The amount of polymer added also needs to be controlled. In this application, the amount of polymer added is relatively small. In the grinding chamber of the air jet mill, the polymer is dispersed in the system of nano-carbon materials. The polymer interacts with the surface of the nano-carbon materials, which changes the surface properties of the nano-carbon materials, prevents the nano-carbon materials from forming larger agglomerates, and makes the particle size control of the nano-carbon materials more uniform.

[0063] In this application, the nano-carbon material is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, graphite flakes, expanded graphite, graphene, furnace black, acetylene black, and Ketjen black.

[0064] Modifying materials physically modify the surface of nano-carbon materials. The polymers all have at least one polar functional group, preferably nitrile, hydroxyl, carboxyl, carbon, ester, amine, aldehyde, etc. The polymer backbone is hydrophobic, which has good compatibility with nano-carbon materials and can be uniformly mixed with nano-carbon materials at a smaller scale. At the same time, the polar functional groups contained in the polymer can improve the dispersibility of nano-carbon materials, making nano-carbon materials easier to mix and be compatible with other materials.

[0065] The polymer preferably has a weight-average molecular weight of 3,000 to 80,000 and a viscosity of 10 to 1,000 cPs after dissolution. More preferably, the polymer preferably has a weight-average molecular weight of 3,000 to 30,000 and a viscosity of 10 to 800 cPs after dissolution. Even more preferably, the polymer preferably has a weight-average molecular weight of 3,000 to 10,000 and a viscosity of 100 to 500 cPs after dissolution.

[0066] The viscosity of a polymer after dissolution refers to the viscosity of the polymer dissolved in NMP (N-methylpyrrolidone) at a mass fraction of 4% at 25°C.

[0067] Preferably, the polymer is polyvinylpyrrolidone. More preferably, the polyvinylpyrrolidone is polyvinylpyrrolidone K10 (BASF) or polyvinylpyrrolidone K30 (BASF).

[0068] If the molecular weight is too small, the viscosity is too low, and the hydrophobic main chain of the polymer is too short, it cannot form an effective coating on the surface of the carbon nanomaterial (in this application, coating refers to a change in the surface properties of the carbon nanomaterial, not necessarily a stable existence on the surface of the carbon nanomaterial in the form of physical or chemical bonds, but rather the presence of the modified material affecting the aggregation behavior of the carbon nanomaterial). This prevents the nanomaterial from exerting its steric hindrance effect, resulting in uneven dispersion of the carbon nanomaterial in subsequent processes and leading to agglomeration. Conversely, if the molecular weight is too large, the viscosity is too high, resulting in a modified carbon nanomaterial with excessively high viscosity, poor flowability, and deteriorated processing performance.

[0069] The small molecule amine and the polymer have a synergistic effect. The lone pair electrons carried by the organic small molecule amine form delocalized π bonds with the surface of the nano carbon material, which can further regulate the charge on the surface of the nano carbon material, making the surface of the nano carbon material negatively charged. The organic small molecule amine is first adsorbed on the surface of the nano carbon material. Under the action of the small molecule organic amine, the surface of the nano carbon material becomes negatively charged, so that the polymer can be more easily and uniformly adsorbed on the surface of the nano carbon material.

[0070] After modifying nano-carbon materials with polymers and small molecule amines, the surface of the nano-carbon materials is coated with polymers containing polar functional groups, which makes the nano-carbon materials more compatible with other materials and more dispersible.

[0071] After modifying the nano-carbon material with the polymer and small molecule amine of this application, the nano-carbon material exhibits a moderate particle size distribution, wherein D 10 The size is larger, while D 50 and D 90 The particle size is smaller, D 50 The particle size is 1–5 μm, D90 < 10 μm, and the tapped density is 0.03–0.10 g / mL. If the particle size is too small, the tapped density is low, generating a large amount of dust during transportation and processing, causing pollution. If the particle size is too large, the tapped density is high, and the particles are large, causing material blockage during transportation and processing.

[0072] After the nano-carbon material and the modified material are mixed evenly in the feeder, the feeding speed of the material is controlled at 100-150 kg per hour. The material enters the air jet mill 1, where the modified nano-carbon material is pulverized to reduce its particle size. At the same time, due to the presence of the modified material, the nano-carbon material is less likely to agglomerate, has better dispersibility, and makes it easier to control the uniformity of the nano-carbon material particle size.

[0073] The primary particle size of nano-carbon materials is 30-50 nm. Nano-carbon materials themselves have strong covalent bond interactions, and in the macroscopic state, they will form secondary aggregates. In this application, when measuring the particle size, a laser particle size analyzer is used. The measured particle size is the particle size of the secondary aggregates of nano-carbon materials, not the primary particle size of nano-carbon materials.

[0074] The purpose of air jet milling in this application is not to reduce the primary particle size of carbon nanomaterials, but to make the particle size of carbon nanomaterial aggregates more uniform. When carbon nanomaterials are mixed with other materials, they also appear as secondary aggregates. The size of the secondary aggregates of carbon nanomaterials is more important and has a more direct impact on their dispersibility. The particle size of the secondary aggregates of carbon nanomaterials is in the micrometer range, not the nanometer range.

[0075] Due to the strong interactions between nano-carbon materials, a bridging effect occurs, causing the powder to stick together, resulting in poor flowability and low pulverization efficiency. After introducing polymers and small molecule amines, the aggregation behavior of nano-carbon materials changes. The nano-carbon material agglomerates are repeatedly opened under the action of high temperature and high pressure airflow, and the fine powder is eliminated under the multiple effects of small molecule amines and polymers. At the same time, the formation of large agglomerates of nano-carbon materials is avoided, resulting in better dispersibility of nano-carbon materials, better flowability, and high transport efficiency under the action of high airflow.

[0076] This application also improves the equipment for processing nano-carbon materials. After the modified nano-carbon materials are pulverized by the air jet mill 1, the particle size is reduced and the dispersion is improved. The materials then enter the demagnetizer 3 in a free-fall manner for demagnetization. Compared to the existing technology that uses a screw compressor to push the nano-carbon materials into the demagnetizer 3, the nano-carbon materials enter the demagnetizer 3 in a dispersed state, resulting in better and more uniform demagnetization. Compared to the existing technology that uses negative pressure to draw the nano-carbon materials into the demagnetizer 3, the nano-carbon materials enter the demagnetizer 3 at an appropriate speed, resulting in a longer demagnetization time, better demagnetization effect, and more uniform demagnetization.

[0077] In addition to demagnetizing using the demagnetizer 3, the nano-carbon material can be pre-demagnetized using permanent magnet rods before entering the air jet mill 1. For example, a permanent magnet demagnetizing device is provided between the feeder and the air jet mill 1. The magnetic force of the permanent magnet rods in the permanent magnet demagnetizing device is 10,000 to 12,000 GS, and the gap between the permanent magnet rods is 5 to 10 cm.

[0078] After demagnetizing once with a permanent magnet rod, some of the metal impurities in the nano-carbon material can be removed. After further demagnetization by the demagnetizer 3, the content of metal impurities can be further reduced. The nano-carbon material after demagnetization by the permanent magnet rod enters the airflow pulverizer 1 through negative pressure suction.

[0079] In this application, polymers and small molecule amines are used simultaneously to improve the dispersibility of nano-carbon materials, so that the size of the secondary agglomerates of nano-carbon materials is within an appropriate range. When used in positive electrode slurry, a positive electrode slurry with good uniformity and less tendency to settle is obtained.

[0080] The air jet mill 1 operates at a pulverizing frequency of 10–50 Hz and an airflow pressure of 6–10 MPa. Its internal structure is made of ceramic, and the inlet temperature is 40–120°C. To prevent the introduction of metallic impurities during the pulverization of nano-carbon materials, all internal parts of the air jet mill 1 that may come into direct contact with the nano-carbon materials are constructed of ceramic. For parts such as pipes that are unsuitable for ceramic fabrication, 304 stainless steel with internal polishing is used, strictly controlling the introduction of metallic impurities.

[0081] Further optimization involves using an airflow mill with an air pressure of 6–8 MPa and an inlet temperature of 40–70°C. The feed rate of the nano-carbon material is 200–300 kg / h, and the airflow rate is 20–30 m³ / h. 3 / min.

[0082] See Figures 1-4 As shown, a disperser 2 is provided between the air jet mill 1 and the demagnetizer 3. After the material is crushed by the air jet mill 1, it is dispersed by the disperser and then enters the demagnetizer 3 by free fall.

[0083] The disperser 2 is equipped with spiral stirring blades that rotate continuously, agitating the material inside the disperser 2 to prevent it from agglomerating or clumping. This physically modifies the surface of the material, making it less prone to agglomeration. Simultaneously, the disperser continuously disperses the material after air-jet pulverization. The dispersed material enters the demagnetizer 3 in a free-fall manner. Due to the well-dispersed state of the material, a better demagnetization effect is achieved in the demagnetizer 3.

[0084] After entering the demagnetizer 3, the material falls freely to a height of at least 3m. The material continues to fall freely, and during this free fall, it is demagnetized. The length of the fall is sufficient to ensure thorough demagnetization of the material.

[0085] In this application, the concept of free fall cannot be strictly defined as free fall in the physical sense. During the process of material falling inside the demagnetizer 3, it will encounter a magnetic mesh with a porous structure. Although the magnetic mesh will not block the falling of the material, it will slow down the falling speed of the material to a certain extent. This is different from free fall in the strict physical sense, but it can still be classified as free fall in this application. That is, during the process of material falling, it may encounter other structural components for the purpose of demagnetization. However, the purpose of setting these components is not to change the falling speed of the material, but to achieve the purpose of demagnetization. It is considered that the material is still in free fall motion.

[0086] To improve demagnetization efficiency, multiple demagnetizers 3 can operate simultaneously. The disperser 2 has at least two outlets, each connected to one demagnetizer 3, and all demagnetizers 3 can operate concurrently. See also Figures 1-4 As shown, the buffer tube has three outlets, each of which is connected to a demagnetizer 3, and the three demagnetizers 3 can work simultaneously.

[0087] See Figures 1-4 As shown, the demagnetizer 3 has an inlet at the top and an outlet at the bottom. The interior of the demagnetizer 3 has at least one demagnetizing channel arranged vertically, and the height of the demagnetizing channel is at least 3m. The inlet of the demagnetizer 3 is connected to the disperser 2 by a pipe 6, and the angle between the axis of the pipe 6 and the horizontal plane is 45° to 60°.

[0088] The inlet of the demagnetizer 3 is connected to the disperser 2 via a pipe 6. The axis of the pipe 6 is at an angle of 45 to 60° with the horizontal plane. The material in the disperser 2 enters the demagnetizer 3 through the pipe 6. The pipe 6 is inclined relative to the horizontal plane. The pipe 6 can slow down the free-falling material, so that the material enters the demagnetizer 3 at a relatively lower speed, but it will not cause the material to accumulate in the pipe 6.

[0089] Other structural disturbance components can be further installed inside the pipe 6 to disperse and decelerate the material. For example, at least one flexible disturbance band is provided inside the pipe 6, with one end of the disturbance band fixed to the top of the inner wall of the pipe 6. When the material falls from above, the disturbance band moves under the action of the material, and the moving disturbance band also interferes with the falling of the material. Alternatively, the inner wall of the pipe 6 is provided with several downwardly inclined baffles. When the material falls from above, it is blocked and slowed down by the baffles, and then slides off the baffles, thus slowing down the material.

[0090] See Figure 1 As shown, the inlet of the demagnetizer 3 is located below the outlet of the disperser 2, and the height difference between the inlet of the demagnetizer 3 and the outlet of the disperser 2 is ( Figure 1 H1) is at least 1.5m. After free fall from a certain height, the material in the disperser 2 enters the demagnetizer 3 for demagnetization.

[0091] See Figures 1-4 As shown, the equipment is installed on a steel structure frame, which includes: columns 11 and at least two support layers fixed to the columns 11, wherein the first support layer 12 is at a height of ( Figure 1 The height of the middle H2 is 4-5m, and the height of the second support layer 13 from the ground is ( Figure 1 The height of H3 is 7-8m. The demagnetizer 3 is fixedly installed on the first support layer, while the feeder, air jet mill 1 and disperser 2 are installed on the second support layer.

[0092] See Figure 1 As shown, the outlet of the demagnetizer 3 is connected to the finished product warehouse 4, and the outlet of the finished product warehouse 4 is connected to the packaging machine 5. The finished product warehouse 4 and the packaging machine 5 are located on the ground.

[0093] The above-described equipment was used to prepare the nano-carbon materials in all embodiments.

[0094] Example 1

[0095] 100 kg of acetylene black and 1.8 kg of hydrogenated nitrile rubber powder, with particle size controlled within D 90 0.2 kg of anhydrous piperazine (model Alanxinco 4307) with a particle size smaller than 100 μm was mixed evenly and then fed into an air jet mill under negative pressure at a feeding station. The feeding rate was 100 kg per half hour, the air pressure was 0.65 MPa, the pulverization frequency was 25 Hz, the electromagnetization current was 25 A, and the demagnetization efficiency of a single demagnetizer was 50 kg per half hour. The resulting acetylene black powder had a particle size of D. 50 1–5 μm, D 90 <10μm, the sum of the five elements Fe, Co, Cu, Zn, Cr and Ni is less than 0.5ppm.

[0096] The particle size distribution of the acetylene black powder prepared in Example 1 is shown in the figure. Figure 6 As shown.

[0097] Example 2

[0098] 150 kg of multi-walled carbon nanotubes, 5 kg of ethylene-vinyl alcohol polymer (Kuraray, weight average molecular weight 20,000-80,000), and 0.5 kg of hydroxyethyl hydrazine were mixed evenly and then fed into an air jet mill under negative pressure at a feeding station. The feeding rate was 150 kg per half hour, the air pressure was 0.8 MPa, the pulverization frequency was 35 Hz, the electromagnetization current was 30 A, and the demagnetization efficiency of a single demagnetizer was 60 kg per half hour. The resulting carbon nanotube powder had a particle size of D. 50 5-10 μm, D 90<100μm, the sum of the five elements Fe, Co, Cu, Zn, Cr and Ni is less than 0.5ppm.

[0099] The particle size distribution of the carbon nanotube powder prepared in Example 2 is shown in the figure. Figure 7 As shown.

[0100] Example 3

[0101] 200kg graphite flakes (specific surface area 15m²) 2 10 kg of polyvinylpyrrolidone (BASF, model K10) and 0.5 kg of isobutanolamine were mixed evenly and then fed into an air jet mill under negative pressure at a feeding station. The feeding speed was 200 kg per half hour, the air pressure was 0.8 MPa, the pulverization frequency was 25 Hz, the electromagnetization current was 45 A, and the demagnetization efficiency of a single demagnetizer was 100 kg per half hour. The resulting graphite micropowder had a particle size of D. 50 2-4 μm, D 90 <20μm, magnetic metal content (Fe, Co, Cu, Zn, Cr, Ni) less than 0.5ppm.

[0102] The particle size distribution of the graphite micropowder prepared in Example 3 is shown in the figure. Figure 8 As shown.

[0103] Example 4

[0104] 200kg graphite flakes (specific surface area 56m²) 2 10 kg of polyvinylpyrrolidone (BASF, model K30) and 0.5 kg of isobutanolamine were mixed evenly and then fed into an air jet mill under negative pressure at a feeding station. The feeding speed was 200 kg per half hour, the air pressure was 0.8 MPa, the pulverization frequency was 25 Hz, the electromagnetization current was 45 A, and the demagnetization efficiency of a single demagnetizer was 100 kg per half hour. The resulting graphite micropowder had a particle size of D. 50 2-4 μm, D 90 <20μm, magnetic metal content (Fe, Co, Cu, Zn, Cr, Ni) less than 0.5ppm.

[0105] The particle size distribution of the graphite micropowder prepared in Example 4 is shown in the figure. Figure 9 As shown.

[0106] Example 5

[0107] 200kg graphite flakes (specific surface area 90m²) 210 kg of polyvinylpyrrolidone (BASF, model K30) and 0.5 kg of methyl hydrazine carbamate were mixed evenly and then fed into an air jet mill under negative pressure at a feeding station. The feeding speed was 200 kg per half hour, the air pressure was 0.8 MPa, the pulverization frequency was 25 Hz, the electromagnetization current was 45 A, and the demagnetization efficiency of a single demagnetizer was 100 kg per half hour. The resulting graphite micropowder had a particle size of D. 50 2-4 μm, D 90 <20μm, magnetic metal content (Fe, Co, Cu, Zn, Cr, Ni) less than 0.5ppm.

[0108] The particle size distribution of the graphite micropowder prepared in Example 5 is shown in the figure. Figure 10 As shown.

[0109] Comparative Example 1

[0110] 100 kg of acetylene black, without any modifiers, is fed into an air jet mill under negative pressure at a feeding station. The feeding rate is 100 kg per half hour, the air pressure is 0.65 MPa, the pulverization frequency is 25 Hz, the electromagnetizing current is 25 A, and the demagnetization efficiency of a single demagnetizer is 50 kg per half hour. The resulting acetylene black powder has a particle size of D. 50 5-10 μm, D 90 <30μm, magnetic metal content (Fe, Co, Cu, Zn, Cr, Ni) less than 0.5ppm.

[0111] The particle size distribution of the acetylene black powder prepared in Comparative Example 1 is shown in the figure. Figure 11 As shown.

[0112] Comparative Example 2

[0113] 100 kg of acetylene black, 1.8 kg of hydrogenated nitrile butadiene rubber powder (model Arlanx 4307), and 0.2 kg of anhydrous piperazine were mixed evenly. See [the original text for further instructions]. Figure 5 As shown, the material enters the airflow pulverizer 7 under negative pressure at the feeding station, and is then fed into the demagnetizer 8 by the screw feeder 10 for demagnetization.

[0114] Material property characterization

[0115] The particle size of the nano-carbon material powder in Examples 1-5 is as follows: Figures 6-10 As shown, the particle size of the acetylene carbon black powder prepared in Comparative Example 1 is as follows: Figure 11 As shown, SEM images of the nano-carbon material powders prepared in Examples 1-5 are as follows. Figures 12-16 As shown, the SEM image of the acetylene carbon black powder prepared in Comparative Example 1 is as follows. Figure 17 As shown.

[0116] The performance parameters of the nano-carbon material powder obtained in Example 1 and Comparative Example 1 are compared, as shown in Table 1. Example 1 used modified materials, and compared with Comparative Example 1, the modified nano-carbon material powder has a higher tap density and a larger D. 10 and smaller D 50 and D 90 The particle size is more concentrated.

[0117] The smaller the tap density, the lower the D 10 The smaller the value, the more fine powder particles are present, resulting in greater dust generation and making the material more difficult to process. D... 50 and D 90 The smaller particle size indicates that the carbon nanomaterial powder does not clump and is easily dispersed. Appropriate tap density and particle size control can solve the dispersion and processing problems of carbon nanomaterials.

[0118] Microscopic morphology analysis by SEM revealed that Examples 1-5 exhibited more uniform particle size, with individual nano-carbon particles visible, while the acetylene black in Comparative Example 1 showed obvious agglomeration and large particles.

[0119] Table 1

[0120] serial number Tap density (g / mL) <![CDATA[D 10 / μm]]> <![CDATA[D 50 / μm]]> <![CDATA[D 90 / μm]]> Example 1 0.043 0.954 3.467 8.743 Example 2 0.052 1.459 4.777 11.04 Example 3 0.048 1.774 3.280 5.607 Example 4 0.051 1.846 3.895 7.153 Example 5 0.045 1.382 3.291 6.317 Comparative Example 1 0.034 0.581 6.198 17.34

[0121] Application performance characterization

[0122] 4g of the nano-carbon material powder prepared in Examples 1-5 and Comparative Example 1 was added to 100g of lithium iron phosphate cathode, 48g of 5% HSV900 PVDF solution, and 84.6g of NMP. The mixture was stirred at 1500rpm / min for 2 hours to obtain the battery slurry. The viscosity, particle size, and resistance of the battery slurry are shown in Table 2.

[0123] Application Example 1 uses the acetylene carbon black powder prepared in Example 1; Application Example 2 uses the carbon nanotube powder prepared in Example 2; Application Example 3 uses the graphite micro powder prepared in Example 3; Application Example 4 uses the graphite micro powder prepared in Example 4; Application Example 5 uses the graphite micro powder prepared in Example 5; and Application Example 4 uses the acetylene carbon black powder prepared in Comparative Example 1.

[0124] Table 2

[0125]

[0126] The particle size distributions of the battery slurries prepared in Examples 1-6 are shown below. Figures 18-23 As shown in Table 2 and Figures 18-23It is evident that the battery slurries of Examples 1-5 exhibit lower slurry viscosity, smaller particle size, and lower resistance. The more uniformly the nano-carbon material is mixed with the cathode material and binder, the lower the slurry viscosity and the smaller the particle size of the slurry. Furthermore, because the nano-carbon material is uniformly dispersed as a conductive agent, the surface resistance of the electrode sheet is also lower after dispersion. This indicates that the nano-carbon materials prepared in Examples 1-5 have better dispersibility and compatibility.

[0127] The battery slurry prepared in Example 1 has a low viscosity and is easy to sieve; the battery slurry prepared in Comparative Example 1 has a high viscosity and is difficult to sieve.

[0128] Demagnetization effect characterization

[0129] The demagnetization effects of Example 1 and Comparative Example 2 are shown in Table 3.

[0130] Table 3

[0131] Sample Name Magnetic metals (ppm) Example 1 - Demagnetization front section 0.345 Example 1 - Demagnetization Middle Section 0.267 Example 1 - Post-demagnetization stage 0.358 Comparative Example 2 - Demagnetization Pre-section 0.548 Comparative Example 2 - Demagnetization Middle Section 0.874 Comparative Example 2 - Post-Demagnetization Section 0.387

[0132] In Example 1, the nano-carbon material enters the demagnetizer by free fall. The nano-carbon material enters the demagnetizer by its own gravity without any additional driving force, resulting in a more uniform demagnetization effect. Samples are taken from the batch of material in chronological order. The differences in metal impurity content are small and the metal content is low in the first, middle, and last stages (the first, middle, and last stages are unrelated to the demagnetizer and are mainly used to distinguish the sampling time order. That is, for the same batch of material, the first sample is the first stage, the second sample is the middle stage, and the third sample is the last stage. The first sampling time is close to the beginning of the feeding, the third sampling time is close to the end of the feeding, and the second sampling time is in the middle of the first and third sampling times).

[0133] In Comparative Example 2, a screw feeder 10 was used to push the nano-carbon material into the demagnetizer. The screw device inside the screw feeder rubs against the carbon material during the movement, introducing new metals into the carbon material. Moreover, the screw feeder feeds unevenly each time, which may cause material blockage. The metal impurity content varies greatly between the front, middle and rear sections.

[0134] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0135] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing modified carbon nanomaterials, characterized in that, The equipment for implementing the preparation method includes: a feeder, an air jet mill, and a demagnetizer arranged sequentially along the material travel direction; the air jet mill and the demagnetizer are arranged sequentially from top to bottom along the height direction; a disperser is provided between the air jet mill and the demagnetizer; after the material is pulverized by the air jet mill, it is dispersed by the disperser and then enters the demagnetizer by free fall. The inlet of the demagnetizer is located below the outlet of the disperser, and the height difference between the inlet of the demagnetizer and the outlet of the disperser is at least 1.5m; the material falls to a height of at least 3m after entering the demagnetizer by free fall. The preparation method includes: Step 1: The nano-carbon material and the modified material are mixed at a mass ratio of 100:0.1~5 and then fed into the air jet mill through a feeder. The modified material includes a polymer and a small molecule amine, with a mass ratio of polymer to small molecule amine of 100:5~10. The polymer is mixed with the small molecule amine in the form of powder, and the particle size of the polymer powder is 10μm~500μm. The polymer is one of hydrogenated nitrile butadiene rubber, polyvinylpyrrolidone, ethyl cellulose, cellulose acetate ester, polyvinyl butyral, ethylene-vinyl alcohol polymer, and methacrylate-acrylate block copolymer; The small molecule amine is one of anhydrous piperazine, isopropanolamine, ethanolamine, hydroxyethylhydrazine, isobutanolamine, triethylamine, and methyl hydrazine carbamate; Step 2: After the material is pulverized by the air jet mill, it enters the demagnetizer by free fall under the action of gravity for demagnetization; the pulverization temperature in the air jet mill is 30~60℃.

2. The method for preparing modified carbon nanomaterials according to claim 1, characterized in that, A permanent magnet demagnetizing device is provided between the feeding machine and the airflow pulverizer. The magnetic force of the permanent magnet rods in the permanent magnet demagnetizing device is 10000~12000GS, and the gap between the permanent magnet rods is 5~10cm.

3. The method for preparing modified carbon nanomaterials according to claim 1, characterized in that, The air jet mill has a pulverizing frequency of 10~50Hz, an air pressure of 6~10MPa, an internal structure made of ceramic, and an inlet temperature of 40~120℃.

4. The method for preparing modified carbon nanomaterials according to claim 1, characterized in that, The disperser has at least two outlets, each of which is connected to a demagnetizer.

5. The method for preparing modified carbon nanomaterials according to claim 1, characterized in that, The demagnetizer has an inlet at the top and an outlet at the bottom. Inside the demagnetizer is at least one section of a demagnetizing channel arranged vertically, with a height of at least 3m. The inlet of the demagnetizer is connected to the disperser by a pipe, and the angle between the axis of the pipe and the horizontal plane is 45~60°.

6. The method for preparing modified carbon nanomaterials according to claim 1, characterized in that, The equipment is installed on a steel structure frame, which includes: columns and at least two support layers fixed on the columns. The first support layer is 4-5m above the ground, and the second support layer is 7-8m above the ground. The demagnetizer is fixedly installed on the first support layer, and the feeder, air jet mill and disperser are installed on the second support layer.

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