Activated carbon, silicon-carbon composite materials, their preparation methods, and applications

Abstract

This invention discloses an activated carbon, a silicon-carbon composite material, its preparation method, and its applications. The preparation method of the activated carbon includes the following steps: S1. Spray drying a suspension of carbon nanotubes, an activator, and resin raw materials to obtain an activated carbon precursor; wherein the mass ratio of carbon nanotubes to resin raw materials is (0.4-1.2):40; the mass ratio of activator to resin raw materials is (30-60):40; S2. Flash evaporation and Joule heating are applied to the activated carbon precursor. The activated carbon preparation method of this invention, through spray drying to design resin coating of carbon nanotubes and activator, and by employing flash evaporation and Joule heating technology, can rapidly prepare activated carbon with high specific surface area and numerous micropores in one step, thereby obtaining a silicon-carbon composite material with low expansion, high initial reversible capacity, high initial coulombic efficiency, excellent rate performance, and stability.

Description

Technical Field

[0001] This invention relates to the field of silicon-carbon composite materials, and more particularly to activated carbon, silicon-carbon composite materials, their preparation methods, and applications. Background Technology

[0002] Vapor-phase silicon-carbon composites utilize activated carbon as a substrate and employ vapor-phase deposition of nano-silicon using a vapor-phase silicon source to form a silicon-carbon composite material with nano-silicon embedded within the pores of the activated carbon. Due to its unique structural design, this material exhibits excellent cycle stability, low expansion rate, and high specific capacity, making it a key area for future lithium-ion battery anode material development. In the preparation of vapor-phase silicon-carbon composites, activated carbon is a crucial raw material, typically accounting for 40%-50% of the final product by mass. Therefore, the preparation of activated carbon has a significant impact on vapor-phase silicon-carbon materials.

[0003] The preparation process of activated carbon mainly includes high-temperature carbonization and activation stages. Most existing heating methods employ kiln radiation heating to raise the material temperature. However, this method suffers from problems such as long heating time, high energy consumption, and complex operation; therefore, there is an urgent need to explore more efficient and rapid heating technologies.

[0004] Flash Joule heating is a novel ultrafast heating technology that, through program control, can rapidly heat materials to high temperatures within seconds. In recent years, several patents have utilized flash Joule heating technology to synthesize high-value activated carbon materials. For example, patent CN117585667A uses flash Joule heating to convert waste resin into nanosphere carbon materials; CN114408919A rapidly carbonizes coconut shells through high-temperature thermal shock and then activates and cleans them with KOH to obtain carbon materials for supercapacitors; CN113307267A mixes coal tar pitch with a pore-forming agent, then performs Joule heating and washes with water to obtain porous carbon materials. However, these porous carbon materials prepared using Joule heating typically require subsequent activation treatment, increasing the complexity of the production process. Meanwhile, the significant volume changes during charge-discharge cycles of silicon-carbon composite materials can induce stress accumulation and cracks within the electrodes, leading to electrode pulverization, separation of the active material from the current collector, and consequently, performance degradation and poor cycle stability. Furthermore, silicon's poor conductivity is detrimental to battery capacity release under high current. Excellent porous carbon structure design has a significant impact on the performance of silicon-carbon composites. For example, patents CN117038989A and CN114122370B introduce carbon nanotubes into porous carbon microspheres to improve the electrical conductivity and expansion rate of silicon-carbon composites. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies where porous carbon materials prepared by Joule heating require subsequent activation treatment, increasing process complexity, and silicon-carbon composite materials suffer from electrode cracking, performance degradation, and insufficient conductivity due to volume expansion during charge and discharge. This invention provides activated carbon, silicon-carbon composite materials, their preparation methods, and applications. When this activated carbon is used for the gas-phase preparation of silicon-carbon composite materials, the composite materials exhibit excellent initial reversible capacity, initial coulombic efficiency, rate performance, and expansion rate. The preparation method of this activated carbon utilizes spray drying to design resin-coated carbon nanotubes and activators, and employs flash Joule heating technology to rapidly prepare activated carbon with high specific surface area and numerous micropores in one step, thereby obtaining silicon-carbon composite materials with low expansion, high initial reversible capacity, high initial coulombic efficiency, excellent rate performance, and stability.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution:

[0007] This invention provides a method for preparing activated carbon, which includes the following steps:

[0008] S1. Spray drying of a suspension of carbon nanotubes, activator and resin raw materials to obtain activated carbon precursor;

[0009] The mass ratio of the carbon nanotubes to the resin raw material is (0.4-1.2):40;

[0010] The mass ratio of the activator to the resin raw material is (30-60):40;

[0011] S2. The activated carbon precursor is subjected to flash evaporation and Joule heating.

[0012] In this solution, the suspension is conventional in the art, such as carbon nanotubes, activators and resin raw materials dispersed in a solvent. In this case, the mixture of the solid dispersion phase and the liquid is called a suspension.

[0013] Preferably, the activator is a zinc salt and / or a polymeric template agent.

[0014] More preferably, the zinc salt comprises one or more of zinc acetate, zinc chloride, zinc oxide, and zinc acetylacetonate.

[0015] More preferably, the polymeric template agent includes one or more combinations of polystyrene, PEO-PPO-PEO triblock copolymer, PS-P4VP diblock copolymer, polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), and polyvinyl alcohol (PVA).

[0016] More preferably, the PEO-PPO-PEO triblock copolymer is one or more of Pluronic® F127, Pluronic® P123 and Pluronic® F108.

[0017] More preferably, the activator is zinc acetate or Pluronic® F127.

[0018] In this approach, zinc salts (such as zinc acetate) or polymeric templates (such as Pluronic® F127) are used as activators to help regulate the size and distribution of pores during the formation of activated carbon, thereby improving the specific surface area and pore volume.

[0019] Preferably, the resin raw material is one or more of phenolic resin, polystyrene, polyacrylonitrile, resorcinol-formaldehyde resin and polyimide, for example, phenolic resin.

[0020] Preferably, the solvent for the suspension of carbon nanotubes, activator and resin raw materials is one or more combinations of anhydrous ethanol, N,N dimethylamide, dimethyl sulfoxide, toluene and pure water, for example, anhydrous ethanol.

[0021] Preferably, the diameter of the carbon nanotubes is 0.5-10 nm, for example 1-2 nm.

[0022] Preferably, the length of the carbon nanotubes is 1μm-30μm, for example 5-15μm.

[0023] Preferably, the mass ratio of the carbon nanotubes to the resin raw material is (0.5-1.0):40.

[0024] Preferably, the mass ratio of the activator to the resin raw material is (40-60):40.

[0025] Preferably, the volume ratio of solid to liquid in the suspension is 5%-30%, for example, 20%.

[0026] Preferably, the inlet air temperature of the spray dryer is 80-200°C, for example, 130-200°C.

[0027] Preferably, the outlet air temperature of the spray dryer is 60-100°C, for example, 80-100°C.

[0028] Preferably, the feed rate of the spray dryer is 0.01-1 L / h, and more preferably 0.5 L / h.

[0029] Preferably, the atmosphere for spray drying is compressed air or an inert atmosphere.

[0030] In this scheme, spray drying can precisely control the morphology and particle size of particles, especially under temperature and atmosphere control, it can effectively obtain precursors with predetermined specific surface area and pore structure.

[0031] More preferably, the inert atmosphere is one or a combination of nitrogen, argon and helium.

[0032] Preferably, the D50 of the spray-dried droplets is 10-100 μm, for example 70 μm.

[0033] Preferably, the D10 of the activated carbon precursor is 1.5-5 μm, for example 3.2 μm.

[0034] Preferably, the D50 of the activated carbon precursor is 3-15 μm, for example 4.7 μm.

[0035] Preferably, the D90 of the activated carbon precursor is 5-50 μm, for example 6.5 μm.

[0036] Preferably, the activated carbon precursor is spherical.

[0037] Preferably, in the activated carbon precursor, the interior of the resin raw material contains a plurality of the aforementioned carbon nanotubes, and the surface of the resin raw material contains a network structure formed by a plurality of the aforementioned carbon nanotubes.

[0038] Preferably, the endpoint temperature of the flash Joule heating is 800-3500℃, for example, 1000℃.

[0039] Preferably, the voltage for flash Joule heating is 50-400V, for example 200V.

[0040] Preferably, the flash Joule heating rate is 1000-8000℃ / s.

[0041] Preferably, the continuous energizing time for flash Joule heating is 0-100s, for example, 10s.

[0042] Preferably, the atmosphere for flash Joule heating is a vacuum or an inert atmosphere.

[0043] In this solution, the flash evaporation Joule heating operation can be conventional in the field, such as heating the material with current in milliseconds to microseconds.

[0044] Preferably, the inert atmosphere is one or more of argon, nitrogen, helium and neon, such as argon.

[0045] More preferably, the vacuum degree of the flash Joule heating is 1 mTorr-10 Torr, for example 1.2 Torr.

[0046] Preferably, the flash joule heating reaction equipment is a flash joule heating device.

[0047] The present invention also provides an activated carbon, which is prepared by the above-described preparation method.

[0048] Preferably, the specific surface area of ​​the activated carbon is 1450-1900 m². 2 / g, for example 1459.7, 1520.1 or 1812.8m 2 / g.

[0049] Preferably, the total pore volume of the activated carbon is 1.0-1.2 cm³. 3 / g, for example 1.02 or 1.15cm 3 / g.

[0050] Preferably, the activated carbon has an average pore size of 0.8-1.8 nm, for example 0.83, 0.88 or 1.76 nm.

[0051] The present invention also provides a method for preparing silicon-carbon composite material, which specifically includes the following steps: performing vapor deposition on the above-mentioned activated carbon and silicon source to obtain the composite material.

[0052] Preferably, the silicon-carbon composite material includes the activated carbon and the silicon source deposited in the pores of the activated carbon.

[0053] Preferably, the silicon source is in a gaseous state.

[0054] Preferably, the silicon source is one or more of silane, ethyl silane, and silane derivatives, such as silane.

[0055] Preferably, the flow rate of the silicon source is 0.1-30 L / min, for example 0.8 L / min.

[0056] Preferably, the atmosphere for the vapor deposition is an inert atmosphere.

[0057] More preferably, the inert atmosphere is one or more of nitrogen, argon and helium, such as argon.

[0058] More preferably, the flow rate of the inert atmosphere is 0.1-40 L / min, for example 0.4 L / min.

[0059] Preferably, the reaction equipment for the vapor deposition is a rotary kiln or a fluidized bed, such as a fluidized bed.

[0060] Preferably, the reaction temperature for the vapor deposition is 400-700°C, for example, 600°C.

[0061] Preferably, the reaction time for the vapor deposition is 2-12 hours, for example, 5 hours or 10 hours.

[0062] Preferably, the heating rate from room temperature to the reaction temperature of the vapor deposition is 1-5 °C / min, for example 3 °C / min.

[0063] Preferably, the vapor deposition pressure is 100-11000 Pa, for example 1 MPa.

[0064] Preferably, the vapor deposition process further includes a carbon coating step.

[0065] Further preferably, the carbon source used for the carbon coating is a hydrocarbon mixture, more preferably one or more combinations of methane, ethane, propane, isopropane, butane, isobutane, ethylene, propylene, acetylene, butene, and natural gas, such as acetylene.

[0066] Further preferably, the carbon source used for carbon coating has a flow rate of 0.1-40 L / min, for example 0.2 L / min.

[0067] Further preferably, the carbon coating atmosphere is an inert atmosphere, more preferably a combination of one or more of nitrogen, argon and helium, such as argon.

[0068] More preferably, the flow rate of the inert atmosphere is 0.1-40 L / min, for example 0.4 L / min.

[0069] Further preferably, the carbon coating method is gas phase coating.

[0070] More preferably, the reaction temperature for carbon coating is 400-700℃, for example, 600℃.

[0071] More preferably, the reaction time for carbon coating is 2-24 hours, for example, 3 hours or 6 hours.

[0072] Further preferably, after carbon coating, the thickness of the carbon coating layer of the resulting silicon-carbon composite material is 2-50 nm, for example, 30 nm.

[0073] In this scheme, the carbon coating is achieved by depositing the carbon source onto the surface of activated carbon through vapor deposition to form a carbon coating layer. This reduces the specific surface area of ​​the material, avoids silicon exposure, reduces the occurrence of side reactions, and improves the material's initial coulombic efficiency, conductivity, and cycle stability.

[0074] The present invention also provides a silicon-carbon composite material, which is prepared by the above-described method for preparing silicon-carbon composite materials.

[0075] Preferably, the silicon content of the silicon-carbon composite material is 44-53 wt%, for example 51.9, 52.2 and 52.4 wt%.

[0076] The present invention also provides an application of the silicon-carbon composite material as described above in the preparation of battery electrodes.

[0077] The positive and progressive effects of this invention are as follows:

[0078] (1) Compared with activated carbon prepared by traditional rotary kiln, the activated carbon prepared by the flash evaporation Joule heating method of the present invention has a larger specific surface area, a smaller average pore size and a higher pore size concentration.

[0079] (2) Compared with silicon-carbon composite materials without added carbon nanotubes, the silicon-carbon composite material containing carbon nanotubes in this invention not only exhibits superior conductivity and lower energy consumption, but also improves rate performance and reduces expansion rate. This is attributed to the high conductivity of carbon nanotubes and the network structure they form, which improves the electrochemical performance and mechanical stability of the silicon-carbon composite material.

[0080] (3) The battery made from the silicon-carbon anode material of the present invention has significant advantages in electrochemical performance. The lithium-ion battery made from the silicon-carbon anode material of the preferred embodiment has an initial reversible capacity of 2093.2 mAh / g, an initial coulombic efficiency of 91.3%, a 2C capacity of 1437.7 mAh / g, and an expansion rate of only 81.5% after 1.5 cycles. Although the expansion rate is slightly higher, the overall performance is relatively balanced, especially in terms of initial reversible capacity and rate performance, showing good comprehensive electrochemical performance. Detailed Implementation

[0081] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0082] In the following examples and comparative examples, the carbon nanotubes have a diameter of 1-2 nm and a length of 5-15 μm, and are sourced from Shenzhen Nanoport Co., Ltd. NTP8012.

[0083] In the following examples and comparative examples, the phenolic resin used was derived from model 4123B of Sawada Chemical Co., Ltd.

[0084] In the following embodiments and comparative examples, the flash evaporation Joule heating device is derived from the Joule heat pipe furnace of Hefei In-situ Technology Co., Ltd.

[0085] In the following embodiments and comparative examples, the fluidized bed device is from Hefei Kejing's OTF-1200X-S-FB model.

[0086] In the following examples and comparative examples, the Pluronic® F127 is derived from Sigma-Aldrich's P2243 model, with a molecular weight of 12600 g / mol.

[0087] Example 1

[0088] S1. A homogeneous suspension was prepared by mixing 10g carbon nanotubes, 400g zinc chloride, 400g phenolic resin, and 3200mL anhydrous ethanol. The suspension was then spray-dried to obtain a spherical activated carbon precursor. The spray drying was performed under a nitrogen atmosphere. The droplet diameter (D50) was 70μm, the inlet air temperature was 130℃, the outlet temperature was 80℃, and the feed rate was 0.5L / h. In the spherical activated carbon precursor obtained after spray drying, the phenolic resin was spherical, the carbon nanotubes were partially located inside the phenolic resin and interwoven with it, and the remaining portion formed a network structure on the surface of the phenolic resin. The particle sizes of the spherical activated carbon precursor were D10 3.2μm, D50 4.7μm, and D90 6.5μm.

[0089] S2. Place the spherical activated carbon precursor in a flash Joule heating device. The vacuum degree of the flash Joule heating is 1.2 Torr. Set the voltage of the flash Joule heating to 200V. Heat to 1000℃ in 1s and then continue to power on for 10s. The device operates in an inert atmosphere of argon. After cooling to room temperature, collect the activated carbon powder.

[0090] S3. The collected activated carbon powder was placed in a fluidized bed apparatus and heated from room temperature to 600°C at a rate of 5°C / min under a pressure of 1 MPa. At 600°C, the flow rate of silane was 0.8 L / min and the flow rate of nitrogen was 0.4 L / min. Silane deposition was carried out for 5 h. During this process, silicon was deposited into the pores of the activated carbon.

[0091] S4. In the same apparatus, maintain 600℃, nitrogen flow rate of 0.4L / min, acetylene flow rate of 0.2L / min, deposit for 3h, and continue carbon coating to obtain silicon-carbon composite material with a carbon coating layer thickness of 30nm.

[0092] Example 2

[0093] The difference from Example 1 is that in step S1, 400g of zinc chloride is replaced with 350g of zinc chloride and 50g of Pluronic® F127. The remaining steps are the same as in Example 1.

[0094] Example 3

[0095] The difference from Example 1 is that the weight of the carbon nanotubes in step S1 is changed to 5g.

[0096] Step S2 is modified to place the spherical activated carbon precursor in a flash Joule heating device. The vacuum degree of the flash Joule heating is 1.2 Torr, the voltage of the flash Joule heating is set to 280V, the temperature is raised to 1000℃ in 1s, and then the power is continuously supplied for 10s. The device is operated in an inert atmosphere of argon. After cooling to room temperature, the activated carbon powder is collected.

[0097] The remaining steps are the same as in Example 1.

[0098] Comparative Example 1

[0099] The difference from Example 1 is that the flash Joule heating device in step S2 is replaced with a conventional rotary kiln heating device, with a rotation speed of 10Hz, a nitrogen flow rate of 0.4L / min, and a heating rate of 5℃ / min to 1000℃, which is then held at the temperature for 2 hours. The remaining steps are the same as in Example 1.

[0100] Comparative Example 2

[0101] S1. Compared to Example 1, only carbon nanotubes were not added.

[0102] S2. Since no carbon nanotubes were added, the resin balls had poor electrical conductivity, making flash evaporation and Joule heating difficult. Therefore, a pre-carbonization step was added. The pre-carbonization step involved placing the spherical activated carbon precursor in a rotary kiln, heating it to 500°C at a speed of 10 Hz and a nitrogen flow rate of 0.4 L / min, with a heating rate of 5°C / min, holding it at that temperature for 2 hours, and then collecting the spherical activated carbon precursor after cooling.

[0103] S3. Place the spherical activated carbon precursor in a flash Joule heating device. The vacuum degree of the flash Joule heating is 1.2 Torr. Set the voltage of the flash Joule heating to 350V. Heat to 1000℃ in 1 second and then continue to power on for 10 seconds. The device operates in an inert atmosphere of argon. After cooling to room temperature, collect the activated carbon powder.

[0104] S4. Same as steps S3 and S4 in Example 1.

[0105] Comparative Example 3

[0106] The difference from Example 1 is that the amount of zinc chloride used in step S1 is increased to 800g. The remaining steps are the same as in Example 1.

[0107] Comparative Example 4

[0108] The difference from Example 1 is that zinc chloride in step S1 is replaced with Pluronic® F127 and the amount is increased to 800g. All other steps are the same as in Example 1.

[0109] Comparative Example 5

[0110] The difference from Example 1 is that the amount of zinc chloride used in step S1 is reduced to 200g. The remaining steps are the same as in Example 1.

[0111] Comparative Example 6

[0112] The difference from Example 1 is that the weight of the carbon nanotubes in step S1 is changed to 15g.

[0113] Step S2 is modified to place the spherical activated carbon precursor in a flash Joule heating device. The vacuum degree of the flash Joule heating is 1.2 Torr, the voltage of the flash Joule heating is set to 185V, the temperature is raised to 1000℃ in 1s, and then the power is continuously supplied for 10s. The device is operated in an inert atmosphere of argon. After cooling to room temperature, the activated carbon powder is collected.

[0114] The remaining steps are the same as in Example 1.

[0115] Effect Example

[0116] The silicon-carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-6 were tested for specific surface area, thermogravimetric analysis, and electrochemical performance.

[0117] (1) Specific surface area test

[0118] The specific surface area of ​​the silicon-carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-6 was tested using the NOVAtouch™ fully automated specific surface area and pore size analyzer from CANTA Instruments, USA. The total pore volume was calculated based on the BJH adsorption-desorption model, and the average pore size was calculated based on the NLDFT model. The specific test results are shown in Table 1.

[0119] (2) Raman test

[0120] The Raman spectra of the silicon-carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-6 were measured using a Thermo Fischer DXR Raman spectrometer. The degree of graphitization of the samples was evaluated by calculating the intensity ratio of the D peak to the G peak of carbon and obtaining Id / Ig.

[0121] Table 1 Physicochemical properties of activated carbon from the examples and comparative examples

[0122]

[0123] (3) Silicon content test

[0124] The silicon content of the silicon-carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-6 was tested respectively. The test method involved heating the samples to 1200℃ in air at a heating rate of 1℃ / min, and then determining the silicon content using thermogravimetric analysis (TGA). The TGA used was a Mettler Toledo TGA2(SF) model. During the TGA, the carbon material completely burned in air to generate CO2, and the silicon in the material was completely oxidized to SiO2. The mass of the remaining SiO2 was calculated by comparing molecular weights, converted to the mass of silicon (Si), and finally divided by the total weight of the original sample to obtain the silicon content. Specific test results are shown in Table 2.

[0125] (4) Electrochemical performance testing

[0126] The silicon-carbon composite materials, conductive carbon black, and polyacrylic acid prepared in Examples 1-3 and Comparative Examples 1-6 were dispersed in water at a mass ratio of 7:2:1 to prepare a slurry. This slurry was coated onto copper foil, dried at 70°C, and then rolled and cut into 12mm diameter electrodes to serve as the anode. A lithium metal sheet was used as the cathode. An electrolyte solution of 1 mol / L LiPF6 three-component mixed solvent was prepared with ethyl carbonate:dimethyl carbonate:ethyl methyl carbonate in a volume ratio of 1:1:1. The separator was Celgard 2400. Assembly was performed in an argon-filled glove box to obtain a 2032 button cell battery. Electrical performance was tested using the LAND battery testing system of Wuhan Landian Electronics Co., Ltd.

[0127] The test conditions for the battery's initial reversible capacity and initial coulombic efficiency were as follows: at room temperature, constant current charge and discharge at 0.1C, with the charge and discharge voltage limited to 0.005-1.5V. Specific test results are shown in Table 2.

[0128] (5) Ratio performance test

[0129] Under the same test conditions as the electrochemical performance test, the 2032 button batteries obtained from the silicon-carbon composite materials of Examples 1-3 and Comparative Examples 1-6 were first subjected to two cycles of 0.1C constant current charge-discharge cycle, and then cycled 5 times at discharge rates of 0.2C, 0.5C, 1C, and 2C, respectively, to obtain the corresponding capacity. The specific test results are shown in Table 2.

[0130] (6) Expansion rate test

[0131] Under the same test conditions as the electrochemical performance test, the expansion rate was measured by dividing the electrode thickness of the 2032 button batteries obtained from the silicon-carbon composite materials of Examples 1-3 and Comparative Examples 1-6 after 1.5 cycles by the original electrode thickness and then multiplying by 100%. Specific test results are shown in Table 2.

[0132] Table 2 Electrochemical properties of silicon-carbon composite materials in the examples and comparative examples

[0133]

[0134] Comparing the results of Example 1 and Comparative Example 1, it can be seen that the activated carbon prepared by flash Joule heating has significant advantages over activated carbon prepared by a traditional rotary kiln. Specifically, it has a larger specific surface area, smaller average pore size, and higher pore size concentration. These advantages stem from the ultra-fast heating rate during flash Joule heating, which leads to the formation of finer zinc droplets and promotes the reaction with carbon. After high-temperature evaporation, more fine micropores are formed. Furthermore, Example 1 has a larger Id / Ig value, indicating a higher degree of carbon structural disorder in this material. The increased micropores provide a larger surface area, thus supporting the deposition of more silicon. Moreover, compared to Comparative Example 1, Example 1 shows improvements in both initial reversible capacity and coulombic efficiency.

[0135] Continuing with the comparison between Example 1 and Comparative Example 2, the key role of carbon nanotubes in the preparation of activated carbon materials and silicon-carbon products from flash joules was analyzed. First, since no carbon nanotubes were added in Comparative Example 2, the resin balls obtained by spray drying had poor conductivity, thus necessitating a pre-carbonization process. Continuing with the comparison between Example 1, Comparative Example 2, and Example 3, during the flash joule heating process, although all three reached the same temperature, Comparative Example 2 and Example 3 required higher voltages and consumed more energy. Furthermore, the higher the content of added carbon nanotubes, the larger the specific surface area and pore volume of the obtained activated carbon precursor. This is because carbon nanotubes themselves have a large surface area, and their unique tubular structure can potentially promote the penetration and reaction of the activator with the carbon source. When the activator reacts with the carbon source at high temperatures, it can utilize the surface and pores of the carbon nanotubes to help form a more stable and uniform pore structure. These activated carbons were then applied to a fumed silicon-carbon matrix, and after silicon deposition and carbon coating, silicon-carbon products were obtained. In comparison, Example 1, which incorporated carbon nanotubes, significantly outperformed Example 3 (with less carbon nanotubes) and Comparative Example 2 (without carbon nanotubes) in terms of rate performance and expansion rate. This difference can be attributed to the excellent electrical conductivity and network structure formed by carbon nanotubes. However, it is worth noting that in Comparative Example 6, when the carbon nanotube content increased to 15g, the specific surface area of ​​the prepared activated carbon decreased. Although the rate performance of the resulting silicon-carbon product was higher, both capacity and efficiency decreased. In Example 1, when the carbon nanotube content was further increased to 20g, entanglement and cross-linking easily occurred between the carbon nanotubes, leading to nozzle clogging during spray drying.

[0136] By comparing Comparative Examples 3 and 4, it was found that different activators exhibited different pore-forming effects at the same mass ratio of activator dosage. Compared to the soft template agent F127, zinc chloride created more micropores and had a larger specific surface area. Simultaneously, zinc chloride catalyzed the graphitization of the sample, reducing the Id / Ig value, thus improving electronic conductivity. In the silicon-carbon product, Example 1, activated with zinc chloride, exhibited stronger adsorption due to its more micropores, resulting in the deposition of more silicon, reaching a silicon content of 46.3 wt%, and demonstrating a higher initial reversible capacity (1788.7 mAh / g). Furthermore, comparing Examples 1 and 2, the synergistic activation of zinc chloride and F127 yielded better results than using zinc oxide alone, achieving a larger specific surface area and pore volume. Although the increased specific surface area did not significantly increase the silicon loading, the increased pore volume improved ion wettability and provided additional buffer space, thus significantly improving the rate capability and expansion rate of the silicon-carbon sample.

[0137] Furthermore, the pore structure of activated carbon can be effectively altered by adjusting the amount of pore-forming agent used in this invention. Compared to Example 1, the increased amount of zinc chloride in Comparative Example 3 resulted in a larger average pore size of the activated carbon, but a decreased specific surface area and a reduction in deposited silicon content, leading to a decrease in initial reversible capacity and coulombic efficiency. However, the expansion rate of Comparative Example 3 was significantly reduced, a phenomenon attributed to both the reduced silicon content and the larger pore volume and pore size, changes that help provide more pores to buffer silicon expansion. Compared to Example 1, the reduced amount of zinc chloride in Comparative Example 5 resulted in a significant decrease in the specific surface area of ​​the activated carbon, a reduction in deposited silicon content, and a decrease in initial reversible capacity and coulombic efficiency.

Claims

1. A method for producing activated carbon, characterized by, It comprises the following steps: S1. Spray drying a suspension of carbon nanotubes, an activating agent and a resin raw material to obtain an activated carbon precursor; The activating agent is zinc chloride and PEO-PPO-PEO triblock copolymer; the resin raw material is a combination of one or more of phenolic resin, polystyrene, polyacrylonitrile, resorcinol-formaldehyde resin and polyimide; The mass ratio of the carbon nanotubes to the resin raw material is (0.4-1.2):40; The mass ratio of the activating agent to the resin raw material is (30-60):40; S2. Flashing Joule heating the activated carbon precursor, and the end point temperature of the flashing Joule heating is 800-3500℃.

2. The method of producing activated carbon according to claim 1, characterized by, The solvent of the suspension of carbon nanotubes, an activating agent and a resin raw material is a combination of one or more of anhydrous ethanol, N-N dimethylamide, dimethyl sulfoxide, toluene and pure water; And / or, the diameter of the carbon nanotubes is 0.5nm-10nm; And / or, the length of the carbon nanotubes is 1μm-30μm; And / or, the mass ratio of the carbon nanotubes to the resin raw material is (0.5-1.0):40; And / or, the mass ratio of the activating agent to the resin raw material is (40-60):

40.

3. The method of producing activated carbon according to claim 2, wherein The PEO-PPO-PEO triblock copolymer is a combination of one or more of Pluronic® F127, Pluronic® P123 and Pluronic® F108.

4. The method of producing activated carbon according to claim 1, wherein The resin raw material is phenolic resin; And / or, the solvent of the suspension of carbon nanotubes, an activating agent and a resin raw material is anhydrous ethanol; And / or, the diameter of the carbon nanotubes is 1nm-2nm; And / or, the length of the carbon nanotubes is 5μm-15μm.

5. The method of producing activated carbon according to claim 1, wherein The volume ratio of solid to liquid in the suspension is 5%-30%; And / or, the inlet air temperature of the spray drying is 80℃-200℃; And / or, the outlet air temperature of the spray drying is 60℃-100℃; And / or, the feeding speed of the spray drying is 0.01L / h-1L / h; And / or, the atmosphere of the spray drying is compressed air or inert atmosphere; And / or, the D50 of the droplets of the spray drying is 10μm-100μm; And / or, the D10 of the activated carbon precursor is 1.5μm-5μm; And / or, the D50 of the activated carbon precursor is 3μm-15μm; And / or, the D90 of the activated carbon precursor is 5μm-50μm; And / or, the activated carbon precursor is spherical; And / or, in the activated carbon precursor, the resin raw material contains a plurality of the carbon nanotubes inside, and the surface of the resin raw material contains a network structure formed by a plurality of the carbon nanotubes.

6. The method of producing activated carbon according to claim 5, wherein The volume ratio of solid to liquid in the suspension is 20%; And / or, the inlet air temperature of the spray drying is 130℃-200℃; And / or, the outlet air temperature of the spray drying is 80℃-100℃; And / or, the feeding speed of the spray drying is 0.5L / h; and / or, the inert atmosphere is a combination of one or more of nitrogen, argon, and helium; and / or, the D50 of the spray-dried droplets is 70 pm; and / or, the D10 of the activated carbon precursor is 3.2 pm; and / or, the D50 of the activated carbon precursor is 4.7 pm; and / or, the D90 of the activated carbon precursor is 6.5 pm.

7. The method of claim 1, wherein: the voltage of the flash Joule heating is 50 V to 400 V; and / or, the rate of the flash Joule heating is 1000 °C / s to 8000 °C / s; and / or, the duration of the flash Joule heating is 0 s to 100 s; and / or, the atmosphere of the flash Joule heating is vacuum or inert atmosphere; and / or, the reaction apparatus of the flash Joule heating is a Joule heat pipe furnace.

8. The method of producing activated carbon according to claim 7, characterized by, the end temperature of the flash Joule heating is 1000 °C; and / or, the voltage of the flash Joule heating is 200 V; and / or, the duration of the flash Joule heating is 10 s; and / or, the inert atmosphere is a combination of one or more of argon, nitrogen, helium, and neon.

9. The method of producing activated carbon according to claim 8, characterized by, the inert atmosphere is argon; and / or, the vacuum degree of the flash Joule heating is 1 mTorr to 10 Torr.

10. The method of producing activated carbon according to claim 9, wherein the vacuum degree of the flash Joule heating is 1.2 Torr.

11. An activated carbon, characterized by, The activated carbon is prepared by the method of any one of claims 1-10.

12. The activated carbon according to claim 11, wherein The activated carbon has a specific surface area of 1450 m 2 / g-1900 m 2 / g; and / or the total pore volume of the activated carbon is 1.0 cm 3 / g-1.2 cm 3 / g; and / or, the average pore size of the activated carbon is 0.8 nm to 1.8 nm.

13. The activated carbon according to claim 12, wherein The specific surface area of the activated carbon is 1459.7 m 2 / g, 1520.1 m 2 / g or 1812.8 m 2 / g; and / or the total pore volume of the activated carbon is 1.02 cm 3 / g or 1.15 cm 3 / g; and / or, the average pore size of the activated carbon is 0.83 nm, 0.88 nm, or 1.76 nm.

14. A method of producing a silicon-carbon composite material, characterized by, The method comprises the following step: performing vapor deposition of the activated carbon of any one of claims 11-13 and a silicon source, thereby obtaining the silicon-carbon composite material.

15. The method of claim 14, wherein the silicon-carbon composite material is prepared by the steps of: mixing a silicon source and a carbon source to form a mixture; heating the mixture to form a silicon-carbon composite material; and annealing the silicon-carbon composite material. The silicon-carbon composite material comprises the activated carbon and the silicon source deposited in the pores of the activated carbon.

16. The method of claim 15, wherein the silicon-carbon composite is prepared by the steps of: The method of preparing the silicon-carbon composite material satisfies one or more of the following conditions: (1) the silicon source is gaseous; (2) the silicon source is a combination of one or more of monosilane, disilane, and silane derivatives; (3) the flow rate of the silicon source is 0.1 L / min to 30 L / min; (4) the atmosphere of the vapor deposition is inert atmosphere; (5) the reaction apparatus of the vapor deposition is a rotary kiln or a fluidized bed; (6) the reaction temperature of the vapor deposition is 400 °C to 700 °C; (7) the reaction time of the vapor deposition is 2 h to 12 h; (8) the heating rate from room temperature to the reaction temperature of the vapor deposition is 1 °C / min to 5 °C / min.

17. The method of making a silicon-carbon composite material of claim 16, wherein, The method of preparing the silicon-carbon composite material satisfies one or more of the following conditions: (1) the silicon source is monosilane; (2) the flow rate of the silicon source is 0.8 L / min; (3) the inert atmosphere is a combination of one or more of nitrogen, argon, and helium; (4) the flow rate of the inert atmosphere is 0.1 L / min to 40 L / min; (5) the reaction apparatus of the vapor deposition is a fluidized bed; (6) the reaction temperature of the vapor deposition is 600 °C; (7) the reaction time of the vapor deposition is 5 h or 10 h; (8) the heating rate from room temperature to the reaction temperature of the vapor deposition is 3 ℃ / min; (9) the gas pressure of the vapor deposition is 1 MPa.

18. The method of making a silicon-carbon composite of claim 17, wherein, The preparation method of the silicon-carbon composite material satisfies (1) and / or (2) among the following conditions: (1) the inert atmosphere is helium; (2) the flow rate of the inert atmosphere is 0.4 L / min.

19. The method of making a silicon-carbon composite of claim 14, wherein, After the vapor deposition, a carbon coating step is further included.

20. The method of making a silicon-carbon composite material of claim 19, wherein, The carbon source used in the carbon coating is a hydrocarbon mixture; and / or, the flow rate of the carbon source used in the carbon coating is 0.1 L / min-40 L / min; and / or, the atmosphere of the carbon coating is an inert atmosphere; and / or, the method of the carbon coating is gas-phase coating; and / or, the reaction temperature of the carbon coating is 400 ℃-700 ℃; and / or, the reaction time of the carbon coating is 2 h-24 h; and / or, after the carbon coating, the thickness of the carbon coating layer of the obtained silicon-carbon composite material is 2 nm-50 nm.

21. The method of making a silicon-carbon composite material of claim 20, wherein, The carbon source used in the carbon coating is a combination of one or more of methane, ethane, propane, isopropane, butane, isobutane, ethylene, propylene, acetylene, butene, and natural gas; and / or, the flow rate of the carbon source used in the carbon coating is 0.2 L / min; and / or, the inert atmosphere is a combination of one or more of nitrogen, argon, and helium; and / or, the flow rate of the inert atmosphere is 0.1 L / min-40 L / min; and / or, the reaction temperature of the carbon coating is 600 ℃; and / or, the reaction time of the carbon coating is 3 h or 6 h; and / or, after the carbon coating, the thickness of the carbon coating layer of the obtained silicon-carbon composite material is 30 nm.

22. The method of making a silicon-carbon composite of claim 21, wherein, The flow rate of the inert atmosphere is 0.4 L / min.

23. A silicon-carbon composite material, characterized by, It is prepared by using the preparation method of the silicon-carbon composite material according to any one of claims 14-22.

24. The silicon-carbon composite of claim 23, wherein, The silicon content of the silicon-carbon composite material is 44 wt%-53 wt%.

25. The silicon-carbon composite of claim 24, wherein, The silicon content of the silicon-carbon composite material is 51.9 wt%, 52.2 wt%, and 52.4 wt%.

26. Use of the silicon-carbon composite material according to any one of claims 23-25 in the preparation of a battery pole piece.

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