A graphene / carbon black composite powder, its preparation method and application

Abstract

This invention discloses a graphene / carbon black composite powder, its preparation method, and its applications. The preparation method of the composite powder includes the following steps: inputting a graphene carbon source into a high-temperature reactor constructed by a plasma torch at a temperature of 3000℃-4000℃ to form graphene-rich flue gas; introducing a carbon black carbon source to cool the flue gas temperature to 1800℃-2500℃ to form a composite reaction zone; pyrolyzing the carbon black carbon source in the composite reaction zone to obtain graphene / carbon black composite powder; introducing the graphene / carbon black composite powder into an activation zone composed of a plasma-heated activator for activation reaction; and obtaining the target product by rapid cooling and gas-solid separation of the activated graphene / carbon black composite powder. This invention achieves in-situ composite of graphene and carbon black at high temperature through plasma technology. The prepared graphene / carbon black composite powder has characteristics such as high specific surface area, high purity, and excellent conductivity, and can be used as a conductive agent for lithium batteries.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation technology, specifically relating to a graphene / carbon black composite powder, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, as important energy storage devices with high energy density and long cycle life, have experienced rapid development in recent years. High-purity, high-structure carbon black is currently the most widely used conductive agent in lithium-ion batteries. However, adding large amounts of carbon black alone as a conductive agent can significantly reduce the energy density of the electrode material. Graphene has a high specific surface area and high conductivity, and as a conductive agent, it can save space for the positive electrode active material, thereby increasing energy density. However, the sheet-like graphene is prone to agglomeration and stacking, which can inhibit ion diffusion, causing severe battery polarization, reducing electrode conductivity, and affecting battery performance. Graphene / carbon black composite powder (binary conductive agent) mainly introduces conductive carbon black during the in-situ reduction process of graphene oxide or directly into graphene. This carbon black is distributed between graphene sheets or adsorbed on graphene nanosheets. On the one hand, it prevents graphene agglomeration and improves its conductivity. On the other hand, zero-dimensional carbon black has good conductivity. Their introduction gives the composite material both continuous electron conduction pathways and provides more and shorter paths for ion transport. In a review of lithium-ion battery cathode materials, Kucinskis et al. reviewed the research progress of graphene (composite) materials, pointing out that graphene / carbon black composite materials form 3D porous structures and conductive networks in lithium-ion battery cathode materials, which is beneficial to electrolyte penetration and accelerates the conduction of lithium ions and electrons. It may be one of the best materials for use as a conductive additive in lithium-ion battery cathode materials, and its effect is better than that of single graphene or carbon black conductive agents (Graphene in lithium ion battery cathode materials: A review, Journal of Power Sources, 240, 66-79, 2013).

[0003] When graphene / carbon black composite powder is used as a conductive agent, the uniform and stable dispersion of the powder in the slurry is one of the keys to ensuring its performance. Only by achieving uniform dispersion of "two-dimensional" graphene and "zero-dimensional" carbon black can the surface-point structure be effectively constructed. Therefore, it is necessary to develop a uniform and stable dispersion technology for graphene / carbon black composite powder. Currently, most published patents use physical mixing to fully disperse graphene and carbon black powders to obtain a mixed conductive agent to improve material performance. However, these physically mixed graphene / carbon black powder conductive agents are prone to component separation and detachment during battery durability verification, which is detrimental to battery charge retention and requires further improvement.

[0004] Plasma is the fourth state, distinct from solid, liquid, and gas, and is characterized by high temperature, high enthalpy, and high chemical activity. Currently, there are numerous reports on the preparation of carbon nanomaterials using plasma, including graphene and carbon black. The literature "Research Progress on Process and Equipment for Plasma Preparation of Conductive Carbon Black" (China Powder Technology, 24(2), 2018) summarizes the development of plasma carbon black in recent years, suggesting that the high temperature and high enthalpy characteristics of plasma are natural conditions for the preparation of conductive carbon black. However, due to the high technical threshold of plasma process equipment, only Monolith in the United States has attempted large-scale industrial production of plasma carbon black. In the field of plasma preparation of graphene, since Dato first reported a plasma method for synthesizing graphene powder in a gaseous environment without a substrate in 2008, research on various preparation methods of plasma graphene powder has developed rapidly, including sliding arc plasma, radio frequency plasma, and electric arc plasma (Research Progress on Plasma Preparation and Modification of Graphene Powder, China Powder Technology, 28(3), 2022). Due to limitations such as high energy consumption and inconsistent product quality of plasma graphene, research on plasma graphene is still in the laboratory exploration stage, and there are no news reports of industrial operation.

[0005] In summary, plasma technology provides a potential pathway for the preparation of carbon nanomaterials. Although many researchers and engineers have made numerous attempts in the field of plasma graphene and carbon black preparation, there have been no reports of in-situ preparation of graphene / carbon black composite powder using plasma. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a graphene / carbon black composite powder, its preparation method and application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] Graphene / carbon black composite powder is synthesized in one step using plasma technology. First, gaseous hydrocarbons or liquid polycyclic aromatic hydrocarbons are input as the graphene carbon source into a high-temperature reactor constructed from multiple plasma torches (average reaction temperature 3000℃-4000℃) to form flue gas rich in few-layer graphene. Next, a carbon black carbon source is introduced, and the graphene flue gas temperature is cooled to 1800℃-2500℃, forming a composite reaction zone. The introduced carbon black carbon source forms carbon black particles in situ on the few-layer graphene, forming the graphene / carbon black composite powder. Then, the graphene / carbon black composite powder is introduced into an activation zone composed of plasma-heated carbon dioxide or water vapor for activation reaction at a temperature of 900℃-1300℃. Finally, the high-temperature flue gas is rapidly cooled and subjected to gas-solid separation to obtain the graphene / carbon black composite powder.

[0009] In the above scheme, the plasma is an electric arc plasma, and the working gas of the plasma is nitrogen, argon, hydrogen, or a mixture of the above gases; multiple electric arc plasma torches are combined to form a high-temperature plasma reactor, and the average reaction temperature of the high-temperature reactor is 3000℃-4000℃; wherein, in order to ensure the uniformity of the reactor temperature, the number of plasma torches is not less than 3, and preferably more than or equal to 4.

[0010] In the above scheme, the gaseous hydrocarbons (i.e., graphene carbon source) input to the high-temperature reactor can be natural gas, acetylene, propane, etc., while the liquid polycyclic aromatic hydrocarbons can be anthracene oil, ethylene tar, etc., with a density of 0.8-1.1 t / m³. 3 The raw material is injected into the central region of the high-temperature reactor through a nozzle. An inert protective gas, such as nitrogen or argon, is placed outside the raw material gas / oil to prevent it from flowing back to the reactor wall and forming hard carbon. The raw material undergoes pyrolysis, nucleation, and growth in the high-temperature reactor, forming high-temperature flue gas rich in few-layer graphene nanosheets. Preferably, gaseous hydrocarbons are used as the graphene carbon source, resulting in higher quality graphene.

[0011] In the above scheme, the graphene carbon source is injected into the central area of ​​the high-temperature reactor through a nozzle. The expansion angle of the graphene carbon source jet into the high-temperature zone is limited to 0°-15° to avoid the raw material colliding with the surface and causing coking, forming hard carbon, which deteriorates the product quality and, in severe cases, causes the equipment to fail to operate.

[0012] In the above scheme, an inert protective gas, such as nitrogen, argon, or a mixture of both, is installed around the nozzle inlet to provide confinement, with a confinement gas flow rate of 10-25 Nm³. 3 / h. Without confining gas, the raw material easily flows back to the area around the nozzle and the reactor wall, forming hard carbon. If the confining gas flow rate is too high, it will reduce the effective power or even directly affect the operation of the unit.

[0013] In the above scheme, after the flue gas rich in few-layer graphene is formed, the carbon black source is introduced into a high-temperature reactor, and the temperature of the graphene flue gas is rapidly cooled to 1800℃-2200℃ to form a composite reaction zone. At this reaction temperature, the carbon black source undergoes pyrolysis, nucleation, and growth to form carbon black particles. Due to the high-temperature environment of the composite reaction zone, the formed carbon black particles will combine with graphene in situ to form graphene / carbon black composite powder. The carbon black source is either a gaseous hydrocarbon or a liquid polycyclic aromatic hydrocarbon; liquid polycyclic aromatic hydrocarbons are preferred as they consume less energy to form carbon black particles.

[0014] In the above scheme, the graphene / carbon black composite powder formed after introducing carbon black as a carbon source has the disadvantages of low toluene transmittance and insufficient specific surface area, requiring activation treatment of the graphene / carbon black composite powder. The graphene / carbon black composite powder is passed into an activation zone rich in carbon dioxide and water vapor to improve the toluene transmittance of the product and increase the specific surface area of ​​the product through etching.

[0015] The reaction temperature in the activation zone is in the range of 900℃-1300℃, and the activator is water vapor, carbon dioxide, or a mixture of both. The water vapor and carbon dioxide are provided by a water vapor and carbon dioxide plasma torch; compared to ordinary high-temperature water vapor and carbon dioxide, plasma heating can provide higher reactivity, which helps to etch the graphene / carbon black composite powder, thereby increasing its porosity and specific surface area.

[0016] The residence time of the raw materials in the high-temperature reactor is in the range of 50-500 milliseconds to ensure the quality of graphene, such as purity and crystallinity; the residence time of the carbon black source in the process of generating carbon black particles is in the range of 0.5-2 seconds to ensure the full reaction of the carbon black source; the activation time of the graphene / carbon black composite powder is generally 1-2 seconds to ensure that the toluene permeability and specific surface area meet the product indicators.

[0017] The rapid cooling and gas-solid separation of the high-temperature flue gas can be achieved using existing mature equipment and processes for carbon black production, such as atomized water cooling, cyclone separator collection, and bag filter dust collection.

[0018] The graphene / carbon black composite powder prepared by the above method has a graphene mass fraction of 5%–15%, an oil absorption value of 220 ml / 100g–280 ml / 100g, a powder resistivity of 0.25 Ω·cm–0.05 Ω·cm, and a BET specific surface area of ​​150 m². 2 / g—250m 2 The powder has an ash content of ≤0.1% and a volatile matter content of ≤0.5%. This graphene / carbon black composite powder features high specific surface area, high structure, high purity, and excellent conductivity, exhibiting superior processing performance and making it suitable for use as a conductive agent in lithium batteries. At low addition levels, this conductive agent demonstrates good synergy in the electrode, effectively improving battery cycle capacity and cycle life.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. This invention uses plasma technology to achieve in-situ composite of graphene and carbon black. The graphene and carbon black are formed at high temperature, which can ensure the uniform and stable combination of graphene and carbon black, and help improve the dispersibility of composite powder.

[0021] 2. The plasma in-situ composite process of this invention enables continuous preparation of graphene / carbon black composite powder, which simplifies the process flow, is easy to operate, and has low cost.

[0022] 3. The graphene / carbon black composite powder prepared by this invention exhibits superior electrochemical performance when used as a conductive agent in battery and supercapacitor electrodes. Its composite structure improves the anisotropy problem of ion transport in graphene conductive agents, achieving synergistic conductivity. Moreover, it can prevent irreversible agglomeration of graphene sheets and increase storage stability. Attached Figure Description

[0023] Figure 1 Intended purpose of graphene / carbon black composite powder device;

[0024] Figure 2 Electron micrograph of the graphene / carbon black composite powder prepared in Example 1;

[0025] Figure 3 High-magnification electron microscope image of carbon black particles composited on graphene sheets prepared in Example 1;

[0026] Figure 4 Electron micrograph of the graphene / carbon black composite powder prepared in Example 2;

[0027] Figure 5 Electron micrograph of the graphene / carbon black composite powder prepared in Comparative Example 3;

[0028] Figure 6 Example 2: Comparison of coking at the furnace head of the high-temperature reactor in Comparative Example 1 and Comparative Example 2;

[0029] Figure labels: 1-Plasma torch, 2-Graphene carbon source inlet, 3-Inert protective gas inlet, 4-Carbon black carbon source inlet, 5-Activator spray inlet, 6-Quick cooling water spray inlet, 7-Outlet pipe, Ⅰ-High temperature reactor, Ⅱ-Graphene reaction quenching zone, Ⅲ-Graphene / carbon black composite reaction zone, Ⅳ-Composite powder activation zone, Ⅴ-Composite powder quenching zone, Ⅵ-Tail gas output zone. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the present invention. Unless otherwise specified, the preparation processes in the following embodiments are conventional methods in the prior art, and therefore will not be described in detail.

[0031] The method in this invention is accomplished using a graphene / carbon black composite powder preparation device. A schematic diagram of the graphene / carbon black composite powder preparation device is shown below. Figure 1It has a high-temperature reactor (I), a graphene reaction quench zone (II), a graphene / carbon black composite reaction zone (III), a composite powder activation zone (IV), a composite powder quench zone (V), and a tail gas output zone (VI) connected in sequence; multiple jet plasma torches (1) are evenly distributed at the top of the high-temperature reactor (I) and arranged at an angle of 15°-45° with the reactor axis. The plasma working gas is N, H2, or a mixture of both. The power of a single torch is 50-500kW, and the flow rate of the working gas in a single torch is 10-100Nm³. 3 / h;

[0032] The head of the high-temperature plasma reactor, which consists of multiple plasma torches, is designed in the shape of a water-cooled spherical cap. The average temperature of the plasma working gas is 4000-7000K. After mixing with the raw materials, the average temperature of the high-temperature reactor is 3000-4000℃. The inner cylinder of the high-temperature reactor is made of high-temperature resistant graphite material, the outside of the graphite cylinder is made of high-temperature resistant alumina spheres, and the outermost layer is high-temperature resistant rock wool.

[0033] The graphene carbon source inlet (2) is located at the center of the head of the high-temperature reactor. The graphene carbon source jet enters the center of the high-temperature flow field composed of multiple plasma torches. The expansion angle of the raw material jet is 0°-15°. A confined inert protective gas inlet (3) is set around the raw material inlet. The protective gas can be nitrogen or argon to prevent the raw material from flowing back to the reactor wall and forming hard carbon. The flow rate of the confined gas is 10-25 Nm³. 3 / h;

[0034] Connected to the bottom of the high-temperature reactor is the graphene reaction quench zone (II), through which the carbon black source is introduced into the carbon black source raw material inlet (4). The carbon black source is a gaseous hydrocarbon or a liquid polycyclic aromatic hydrocarbon. The direction of the carbon black source injection is perpendicular to the direction of the high-temperature graphene powder tail gas flow at a 90° angle. By controlling the amount of carbon black source injection, the tail gas temperature of the high-temperature reactor is reduced to 1800℃-2200℃. At this temperature, a graphene / carbon black composite reaction zone (III) is constructed. Carbon black particles nucleate and grow in this zone and combine with graphene to form graphene / carbon black composite powder. The inner cylinder material of the composite reaction zone is made of high-temperature resistant chromium corundum brick. The outer side of the corundum brick is high-alumina brick, and the outer side of the high-alumina brick is lightweight insulating brick.

[0035] A plasma-heated activator inlet (5) is set up immediately after the graphene / carbon black composite reaction zone. The distance between the inlet and the carbon black carbon source inlet is 2m-5m. The activator is carbon dioxide or water vapor. The injected activator reduces the temperature of the reaction tail gas to the range of 900℃-1300℃, terminating the carbon black generation reaction. After that, it enters the composite powder activation zone (Ⅳ). Through the activation reaction, the oil absorption value of the composite powder is further improved and the porosity and toluene transmittance of the product are improved.

[0036] A cooling device is installed at the tail end of the composite powder activation zone. A quench water inlet (6) is sprayed in to inject high-purity cooling water, which cools the composite powder quench zone (V) to 230℃~280℃. The reaction tail gas is collected in the tail gas output zone (VI) and enters the outlet pipe (7) to separate the composite powder from the bag collector.

[0037] Example 1

[0038] This embodiment uses four plasma torches, each with a power of 50kW, for a total power of 200kW, and the total flow rate of the working gas N2 is 35Nm³. 3 The plasma torch is positioned at a 30° angle to the central axis of the high-temperature reactor; propane is used as the carbon source for the graphene, with a flow rate of 3 Nm³ / h. 3 / h, jet injection expansion angle is 15°, anti-backflow constraint gas flow rate is 10Nm 3 The residence time of the raw material in the high-temperature reactor is 400 milliseconds, and the temperature is maintained at 3300℃ during this period. The carbon source of carbon black is anthracene oil, with a flow rate of 40 kg / h. The activator inlet is 3 m away from the anthracene oil inlet. During the process of generating carbon black particles from the carbon source, the temperature is controlled at 1800℃, and the residence time is 1.5 seconds. The activation time of the graphene / carbon black composite powder is 1.5 seconds, and the activator is water vapor, with the temperature controlled at around 900℃. Figure 2 Transmission electron microscopy images of the composite powder sample prepared for this embodiment reveal the presence of obvious graphene sheets and highly structured carbon black particles in the product. Figure 3 The corresponding high-magnification transmission electron microscopy images show that the carbon black particles are tightly attached to or embedded in the surface of the graphene sheets, confirming that the graphene and carbon black particles in this embodiment can be tightly combined to form a stable composite powder.

[0039] Detailed properties of the composite powder are shown in Table 1. The prepared graphene / carbon black composite powder was added to the lithium iron phosphate cathode material system at a ratio of 1.8%. After stirring, coating, and drying, it was used to fabricate cathode sheets. Batteries were assembled using the CR2032 coin cell assembly method and tested on a battery tester. The main performance characteristics are shown in Table 2. It can be seen that this product has high specific surface area, high structure, high purity, and excellent conductivity, exhibiting superior processing performance and suitable for use in battery positive and negative electrodes. Even at low addition levels, it demonstrates good synergy in the electrode, effectively improving battery cycle capacity and cycle life without affecting the electrochemical mechanism.

[0040] Example 2

[0041] This embodiment uses four plasma torches, each with a power of 100kW, for a total power of 400kW, and the total flow rate of the working gas N2 is 80Nm³. 3 / h, the plasma torch is arranged at a 45° angle to the central axis of the high-temperature reactor, and the graphene carbon source propane is 6.5 Nm.3 / h, jet injection expansion angle is 15°, anti-backflow constraint gas flow rate is 15Nm 3 The residence time of the raw material in the high-temperature reactor is 200 milliseconds, and the temperature is maintained at 3700℃ during this period. The carbon source for carbon black is anthracene oil, with a flow rate of 85 kg / h. The activator inlet is 3 m away from the anthracene oil inlet. During the process of generating carbon black particles from the carbon source, the temperature is controlled at 2000℃ and the residence time is 1 second. The activation time of the graphene / carbon black composite powder is 1.5 seconds, the activator is carbon dioxide, and the temperature is controlled at around 1000℃. Figure 4 Transmission electron microscopy (TEM) images of the composite powder sample prepared for this embodiment reveal the presence of distinct graphene sheets and highly structured carbon black particles. Detailed product performance is shown in Table 1. The performance indicators of the assembled CR2032 coin cells after adding 1.8% (wt) graphene / carbon black powder as a conductive agent to the lithium iron phosphate cathode material system are shown in Table 2.

[0042] Example 3

[0043] This embodiment uses five plasma torches, each with a power of 160kW, for a total power of 800kW, and the total flow rate of the working gas N2 is 120Nm³. 3 / h, the plasma torch is arranged at a 45° angle to the central axis of the high-temperature reactor, and the graphene carbon source propane is 15Nm. 3 / h, jet injection expansion angle is 15°, anti-backflow constraint gas flow rate is 25Nm 3 The residence time of the raw material in the high-temperature reactor is 50 milliseconds, and the temperature is maintained at 3900℃ during this period. The carbon black source is anthracene oil, with a flow rate of 180 kg / h. The activator inlet is 3 m away from the anthracene oil inlet. During the generation of carbon black particles from the carbon black source, the temperature is controlled at 1900℃, and the residence time is 0.5 seconds. The activation time of the graphene / carbon black composite powder is 1.7 seconds, and the activator is carbon dioxide, with the temperature controlled at around 1200℃. The product performance of the composite powder prepared in this example is shown in Table 1. The performance indicators of the CR2032 coin cell assembled after adding 1.8% (wt) graphene / carbon black powder conductive agent to the lithium iron phosphate cathode material system are shown in Table 2.

[0044] Comparative Example 1

[0045] The only parameter change between Comparative Example 1 and Example 2 is the change in the anti-backflow constraint gas volume; the equipment structure and other parameters are the same. Four plasma torches are used, each with a power of 100kW, for a total power of 400kW, and the total flow rate of the working gas N2 is 80Nm³. 3 / h, the plasma torch is arranged at a 45° angle to the central axis of the high-temperature reactor, and the graphene carbon source propane is 6.5 Nm. 3 / h, jet injection expansion angle is 15°, anti-backflow constraint gas flow rate is 0 Nm3 In the high-temperature reactor, the residence time of the raw material is 200 milliseconds, and the temperature is maintained at 3700℃ during this period. The carbon black source is anthracene oil, with a flow rate of 85 kg / h. The activator inlet is 3 m away from the anthracene oil inlet. During the generation of carbon black particles from the carbon black source, the temperature is controlled at 2000℃, and the residence time is 1 second. The activation time of the graphene / carbon black composite powder is 1.5 seconds, and the activator is carbon dioxide, with the temperature controlled at around 1000℃. In Comparative Example 1, severe coking occurred at the head of the high-temperature reactor, ultimately leading to the reactor's inability to operate normally and poor product quality. Figure 6 As shown, the furnace head in Example 2 is covered with only a thin layer of carbon material, which does not affect the continuous operation of the device; in Comparative Example 1, a large amount of hard carbon forms on the furnace head, making it difficult for the raw material propane to enter the high-temperature reactor, and the device cannot operate continuously. The performance of the product prepared in this comparative example is shown in Table 1. The performance indicators of the CR2032 coin cell assembled after adding 1.8% (wt) graphene / carbon black powder conductive agent to the lithium iron phosphate cathode material system are shown in Table 2. It can be seen that its performance is lower than that of Example 2.

[0046] Comparative Example 2

[0047] The difference between Comparative Example 2 and Example 2 is the change in the injection angle of the graphene carbon source; other structures and parameters are the same. Four plasma torches were used, each with a power of 100kW, for a total power of 400kW. The total flow rate of the working gas, N2, was 80Nm³. 3 / h, the plasma torch is arranged at a 45° angle to the central axis of the high-temperature reactor, and the graphene carbon source propane is 6.5 Nm. 3 / h, jet inlet expansion angle is 20°, anti-backflow constraint gas flow rate is 15Nm 3 / h; the carbon source for carbon black is anthracene oil, the flow rate is 85 kg / h, and the activator inlet is 3 m away from the anthracene oil inlet. A small amount of reflux coking occurs at the head of the high-temperature reactor, such as... Figure 6 As shown, the product quality is slightly inferior. This is because a larger expansion angle causes the raw material to be sprayed onto the wall surface, resulting in the formation of hard carbon. Detailed product performance in this comparative example is shown in Table 1. The performance indicators of the assembled CR2032 coin cell after adding 1.8% (wt) graphene / carbon black powder conductive agent to the lithium iron phosphate cathode material system are shown in Table 2. It can be seen that its performance is lower than that of Example 2.

[0048] Comparative Example 3

[0049] Comparative Example 3 differs from Example 3 in that the temperature of the high-temperature reaction section is lowered and controlled at 2500 degrees Celsius (achieved by changing the heating power), while other structures and parameters remain the same. Five plasma torches were used, each with a power of 120 kW, for a total power of 600 kW, and the total flow rate of the working gas N2 was 120 Nm³. 3 / h, the plasma torch is arranged at a 45° angle to the central axis of the high-temperature reactor, and the graphene carbon source propane is 15Nm. 3 / h, jet injection expansion angle is 15°, anti-backflow constraint gas flow rate is 25Nm 3 / h; the carbon source of carbon black is anthracene oil, the flow rate is 180kg / h, and the activator spray inlet is 3m away from the anthracene oil inlet. Figure 5 The transmission electron microscope image of the sample in this example shows that there are a large number of high-structure carbon black particles in the product, and the content of graphene structure product is very low. After testing and analysis, the graphene content is about 1%, which is much lower than that in Example 3. This confirms that the high temperature of the high-temperature reactor is a necessary condition for ensuring the graphene content. More detailed product performance is shown in Table 1 and Table 2.

[0050] Table 1: Performance List of Products Prepared in Each Example and Comparative Example

[0051]

[0052] Table 2: Battery performance with 1.8% (wt) composite conductive agent added to lithium iron phosphate cathode material system

[0053]

[0054] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing graphene / carbon black composite powder, characterized in that: Includes the following steps: A graphene carbon source is fed into a high-temperature reactor constructed by a plasma torch at a temperature of 3000℃-4000℃ to form graphene-rich flue gas. The temperature of the graphene-rich flue gas is cooled to 1800℃-2500℃ by introducing carbon black carbon source, forming a composite reaction zone; the carbon black carbon source is pyrolyzed in the composite reaction zone and carbon black particles are formed in situ on the graphene to obtain graphene / carbon black composite powder. The graphene / carbon black composite powder is introduced into an activation zone composed of a plasma-heated activator for activation reaction; the activated graphene / carbon black composite powder is then rapidly cooled and subjected to gas-solid separation to obtain the final graphene / carbon black composite powder. The graphene carbon source is a gaseous hydrocarbon or a liquid polycyclic aromatic hydrocarbon; the plasma working gas in the plasma torch is at least one of nitrogen, argon, and hydrogen. The graphene carbon source is injected into the central region of the high-temperature reactor through a nozzle, and the expansion angle of the graphene carbon source jet into the high-temperature reactor is limited to 0°-15°; an inert protective gas is set around the nozzle inlet for confinement, and the confinement gas flow rate is 10 Nm³. 3 / h-25 Nm 3 / h.

2. The method for preparing graphene / carbon black composite powder according to claim 1, characterized in that: The number of plasma torches shall not be less than three.

3. The method for preparing graphene / carbon black composite powder according to claim 2, characterized in that: The gaseous hydrocarbon is natural gas, acetylene, or propane; the liquid polycyclic aromatic hydrocarbon is anthracene oil or ethylene tar.

4. The method for preparing graphene / carbon black composite powder according to any one of claims 1 to 3, characterized in that: The residence time of the raw materials in the high-temperature reactor is 50-500 milliseconds.

5. The method for preparing graphene / carbon black composite powder according to claim 4, characterized in that: The inert protective gas is nitrogen, argon, or a mixture of both.

6. The method for preparing graphene / carbon black composite powder according to claim 1, characterized in that: The graphene in the graphene-rich flue gas is few-layer graphene, with no more than 10 graphene layers.

7. The method for preparing graphene / carbon black composite powder according to claim 1, characterized in that: The carbon black source is a gaseous hydrocarbon or a liquid polycyclic aromatic hydrocarbon; the carbon black source resides in the composite reaction zone for 0.5-2 seconds.

8. The method for preparing graphene / carbon black composite powder according to claim 1, characterized in that: The activator is carbon dioxide or water vapor; the activation reaction takes 1-2 seconds.

9. A graphene / carbon black composite powder, characterized in that: It is prepared by the preparation method as described in any one of claims 1 to 8.

10. The graphene / carbon black composite powder obtained as claimed in claim 9 is used as a conductive agent.

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