Method for preparing porous carbon microspheres through microwave induction of high-entropy alloy-petroleum coke and application

Abstract

The invention belongs to the technical field of battery materials, and mainly relates to a method for preparing porous carbon microspheres through microwave induction of high-entropy alloy-petroleum coke and application. The method comprises the following steps: performing low-temperature plasma activation treatment on crushed and sieved petroleum coke powder to obtain activated petroleum coke powder; mixing and reacting the activated petroleum coke powder with a salt solution containing at least five transition metals, and performing freeze drying to obtain a high-entropy alloy-petroleum coke composite material precursor; the high-entropy alloy-petroleum coke composite material precursor is subjected to microwave radiation treatment in an inert atmosphere, and a carbonized precursor of a spherical structure is obtained; and performing high-temperature activation treatment on the carbonized precursor with the spherical structure in an activation atmosphere, and performing acid pickling and drying to obtain the porous carbon microsphere material. According to the method, the porous carbon microsphere material with high specific surface area, high microporosity and excellent conductivity is prepared through plasma activation, multi-metal complexation, microwave radiation and high-temperature activation treatment, and can be applied to a negative electrode material of a lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and mainly relates to a method and application for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke. Background Technology

[0002] Against the backdrop of global energy structure transformation and the accelerated implementation of carbon neutrality strategies, the rapid development of electric vehicles, smart grids, and portable electronic devices has placed higher demands on the performance of lithium-ion batteries. Anode materials, as a core component of batteries, are facing significant technological challenges. While commercially available graphite anode materials offer significant cost advantages and mature manufacturing processes, their inherent limitation of theoretical specific capacity (372 mAh / g) makes it difficult to meet the development needs of next-generation high-energy-density lithium-ion batteries.

[0003] While silicon-based anode materials possess excellent theoretical specific capacity (4200 mAh / g), their low conductivity easily leads to electrode polarization, causing irreversible damage to the electrode structure due to volume expansion during charging, and resulting in significant reductions in coulombic efficiency due to side reactions with the electrolyte. These inherent defects severely limit the electrochemical performance of silicon-based anodes, and their cycle stability falls far short of the basic requirements for commercial applications. In contrast, carbon materials exhibit good conductivity and structural stability. By combining silicon with carbon materials, the advantages of both can be fully integrated, effectively mitigating the volume expansion of silicon during charging while significantly improving the conductivity and cycle stability of the composite material. However, the improvement in electrochemical performance when conventional carbon materials (such as graphite and carbon nanotubes) are combined with silicon is limited, mainly due to their inherent characteristics: on the one hand, the low specific surface area and microporosity make it difficult to achieve effective dispersion and stable loading of silicon nanoparticles, leading to silicon particle agglomeration during cycling; on the other hand, the discontinuous contact interface formed between silicon and the carbon matrix makes the electron transport path prone to breakage during cycling. These structural defects collectively limit the improvement effect of conventional carbon materials on the electrochemical performance of silicon anodes.

[0004] Studies have shown that the structural characteristics of porous carbon matrices are significantly correlated with electrochemical performance: high specific surface area is conducive to achieving uniform loading of silicon nanoparticles and preventing their aggregation; high microporosity can effectively suppress the volume expansion of silicon during lithium intercalation through the interface constraint effect; and highly graphitized carbon skeletons ensure rapid electron conduction, reduce internal resistance, improve the overall conductivity of the electrode, and improve the efficiency of electrochemical reactions.

[0005] Currently, the main methods for preparing porous carbon include physical activation and chemical activation. Physical activation primarily uses oxidizing gases (such as water vapor and carbon dioxide) as the activation medium, etching carbon atoms through a gas-solid phase reaction at high temperatures (800-1000℃) to create pores. However, while physical activation is relatively simple, it has limitations such as low activation efficiency, low specific surface area and microporosity of the resulting material, and a wide pore size distribution. Chemical activation prepares porous carbon materials mainly by reacting chemical activators (such as KOH, ZnCl2, H3PO4, etc.) with carbon precursors at lower temperatures (400-800℃) to construct the porous structure. Furthermore, while chemical activation (such as KOH) can increase the specific surface area, the activation process has significant drawbacks: taking KOH as an example, when activation conditions are not properly controlled (such as an excessively high alkali-to-carbon ratio or excessively long activation time), the vigorous chemical reaction can lead to over-etching of micropores, causing adjacent micropores to merge into mesopores or macropores, thus reducing the microporosity of the material. Furthermore, porous carbon prepared by the aforementioned traditional methods typically exhibits low graphitization and fewer sp² hybrid carbon structures, resulting in weak electron transport capabilities and low electrical conductivity. For example, a method involves using microwave heating to select small molecule compounds with aldehyde groups and amino groups as ligands, generating imino-rich COF through a Schiff base reaction. The COF acetonitrile solution is then reacted with melamine and zinc nitrate hexahydrate to obtain a suspension. After microwave heating and drying, a precipitate is obtained. This precipitate is then heated to create pores, preparing two-dimensional layered porous carbon. This method, using a microwave-assisted composite stirring method to synthesize precursors, produces two-dimensional layered porous carbon with high conductivity and a continuous electron transport path. However, the porous carbon material prepared by this method has insufficient microporosity, and its electrochemical performance needs further improvement. Another example is using honey as a raw material, undergoing a microwave-assisted hydrothermal reaction, followed by drying and immersion in a cobalt nitrate solution. After stirring, centrifugation, and drying, alkali treatment is added, and finally, high-temperature pyrolysis is performed to prepare porous carbon material. The porous carbon material prepared by this method has a significant specific surface area and total pore volume. However, this method uses a large amount of strong alkali, which is highly corrosive. At the same time, the high amount of strong alkali used leads to uneven pore size distribution, further increasing the degree of defects.

[0006] Therefore, there is an urgent need to develop a method for preparing porous carbon materials with high specific surface area, high microporosity, and high electrical conductivity. Summary of the Invention

[0007] In order to overcome the technical problems of porous carbon materials in the prior art, this invention uses petroleum coke as raw material, which is activated and then complexed with a metal solution, freeze-dried, and then activated at high temperature after microwave radiation. Finally, the metal is removed by acid washing, thus preparing a porous carbon microsphere material with high specific surface area, high microporosity and excellent conductivity.

[0008] In this embodiment of the invention, a method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke is provided, the method comprising the following steps: S1. The pulverized and sieved petroleum coke powder is subjected to low-temperature plasma activation treatment to obtain activated petroleum coke powder. S2. The activated petroleum coke powder is mixed and reacted with a salt solution containing at least 5 transition metals, and then freeze-dried to obtain a high-entropy alloy / petroleum coke composite material precursor. S3. The high-entropy alloy / petroleum coke composite material precursor is subjected to microwave radiation treatment in an inert atmosphere to obtain a carbonized precursor with a spherical structure. S4. The carbonized precursor with the spherical structure is activated at high temperature under an activating atmosphere, and then acid washed and dried to obtain porous carbon microsphere material.

[0009] As an optional implementation, in step S1, the low-temperature plasma activation treatment includes: The activation treatment atmosphere is air, oxygen, or a mixture of both. The activation power is 50~1000W; The processing time is 10~60 minutes.

[0010] As an optional implementation, the transition metal is characterized in that it includes: Fe, Co, Ni, Cu, Zn, Mn, Cr, and Mo.

[0011] As an optional implementation, the solid-liquid ratio of the activated petroleum coke powder to the salt solution is 1g:5-10mL; the concentration of each metal salt in the salt solution is 0.1~0.5 mol / L; and the process parameters for the mixing reaction are: temperature 30°C~60°C; and reaction time 2~4h.

[0012] In a specific embodiment, the freeze-drying temperature is -20 to -60°C, and the time is 2 to 6 hours.

[0013] As an optional implementation, in step S3, the power of microwave radiation is 500~2000W and the time is 10~40min.

[0014] As an optional implementation, in step S4, the high-temperature activation treatment is performed by activating the material at a temperature of 750~950℃ for 60~300 minutes under a carbon dioxide or water vapor atmosphere.

[0015] As an optional implementation, in step S4, the acid washing process involves stirring the product after high-temperature activation in a mixed solution of hydrochloric acid and nitric acid with a concentration of 1-3 mol / L for 1-2 hours.

[0016] Based on the same inventive concept, the present invention also provides porous carbon microspheres prepared by the above-described preparation method, wherein the specific surface area of ​​the porous carbon microspheres is not less than 1900 m². 2 / g, microporosity not less than 82%, electrical conductivity not less than 4S / mm.

[0017] Based on the same inventive concept, embodiments of the present invention also provide the application of the above-mentioned porous carbon microspheres in lithium-ion battery anode materials.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention provides a method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke. In the raw material stage, the petroleum coke powder is plasma-activated, effectively introducing abundant oxygen-containing functional groups on its surface. These functional groups serve as anchoring points for subsequent metal ion complexation, ensuring high dispersion and loading of metal species. The polar functional groups and metal ions in the precursor can efficiently absorb microwave energy, causing the material to heat up instantly from the inside out. This rapid heating promotes the melting, flow, and rearrangement of organic molecular chains in the precursor, which automatically shrink into a perfect sphere under surface tension. At the same time, this process helps to eliminate internal defects, promote the densification of the carbon structure, and form a carbon skeleton with higher strength. The precursor is formed by complexation with various transition metal elements. Different metal elements have different catalytic graphitization capabilities and catalytic gasification (reaction with water vapor or CO2) activity temperatures and rates. In the high-temperature activation stage, this difference leads to multi-stage etching behavior. Some metals (such as Fe and Ni) initiate pore formation at relatively low temperatures, while others (such as Co and Mo) continue to act at higher temperatures. This "relay race" etching process avoids the problem of over-reaction or deactivation of a single catalyst at a specific temperature, thus enabling more efficient etching of a large number of micropores in the carbon framework and forming a hierarchical multi-level porous structure, significantly improving the specific surface area and microporosity of the final product. It also provides ideal anchoring points for the uniform loading of subsequent silicon nanoparticles. Simultaneously, during microwave treatment and subsequent high-temperature activation, these metal nanoparticles can reduce the activation energy for the transformation of carbon atoms from a disordered state to an ordered graphite lattice, catalyzing the conversion of surrounding amorphous carbon into short-range ordered graphene sheets with better conductivity, significantly improving conductivity. This method eliminates the need for highly corrosive chemical activators such as potassium hydroxide and sodium hydroxide, avoiding the environmental risks and cost issues associated with subsequent cleaning.

[0019] (2) The porous carbon microspheres prepared by this invention have a high specific surface area (>1900 m²). 2The porous carbon microspheres exhibit high microporosity (>82%) and good electrical conductivity (>4S / mm). Their well-defined hierarchical pore structure provides effective anchoring points for silicon particles, significantly improving their structural stability during cycling. When used in the preparation of lithium-ion battery anode materials, the reversible capacity of the lithium-ion half-cell is no less than 1600 mAh / g, and the retention rate after 300 cycles is no less than 80%. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a SEM image of the porous carbon microsphere material provided in Embodiment 1 of the present invention; Figure 2 The BET diagram of the porous carbon microsphere material provided in Embodiment 1 of the present invention; Figure 3 The graph shows the porous carbon microsphere material provided in Example 1 of this invention under 0.1 A / g cycling test. Detailed Implementation

[0022] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0024] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0025] This invention provides a method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke, specifically including the following steps: S1. Petroleum coke is pulverized and sieved to obtain petroleum coke powder. The petroleum coke powder is then activated using a plasma activation device. During this activation process, the atmosphere is air, oxygen, or a mixture of both, and the treatment is performed for 10-60 minutes at a power of 50-1000W. More preferably, the treatment is performed for 30 minutes at a power of 500W in an oxygen atmosphere. In oxygen plasma, almost all the active species generated are oxygen-containing active groups, such as oxygen radicals (·O), ozone (O3), and excited-state oxygen molecules (O2*). Compared to air plasma (which contains a large number of nitrogen-containing groups), all the energy is concentrated on generating active oxygen species for etching and oxidizing the petroleum coke raw material. At the same power and time, the efficiency and final density of oxygen-containing functional groups (such as C=O, -COOH, -OH) introduced onto the surface of petroleum coke by oxygen plasma are significantly higher than those in an air atmosphere. Experiments have shown that excessively high plasma power and excessively long processing times result in a physical bombardment effect of high-energy ions on the surface that far outweighs the chemical modification effect. This leads to rapid surface material ablation, and the damaged surface structure may prevent the formation of a dense carbon framework in subsequent experiments. Simultaneously, surface defects caused by excessive physical etching can further develop into macropores or cracks during high-temperature activation. While this may increase the total pore volume, it severely sacrifices the microporosity. Micropores are crucial for confining silicon nanoparticles and preventing their aggregation, ultimately leading to a significant reduction in the material's tap density and strength. Insufficiently low plasma power and excessively short processing times result in insufficient energy in the generated active particles, making it difficult to effectively break the stable C / C bonds of petroleum coke, resulting in extremely low functional group introduction efficiency. Metal ions cannot be uniformly loaded and tend to aggregate locally, forming large metal particles. During the high-temperature activation stage, these aggregated large metal particles become localized "over-etching centers," leading to excessively large pores, while other areas are under-activated due to a lack of catalyst. The resulting porous carbon microspheres have extremely uneven pore distribution, low specific surface area, and poor mechanical strength.

[0026] Step S2: Activated petroleum coke powder and a salt solution containing at least five transition metals are mixed and reacted at 30°C to 60°C for 2 to 4 hours at a solid-liquid ratio of 1 g: 5-10 mL. The resulting solution is then frozen and freeze-dried at -20°C to -60°C for 2 to 6 hours to obtain a high-entropy alloy-petroleum coke composite material precursor. The transition metals include Fe, Co, Ni, Cu, Zn, Mn, Cr, and Mo. The metal salt solution is prepared by adding soluble Fe, Co, Ni, Cu, Zn, Mn, Cr, and Mo salts to water to prepare a mixed salt solution with a concentration of 0.1 to 0.5 mol / L for each metal salt. More preferably, the transition metal salt solution is a soluble mixed salt solution of Fe, Co, Ni, Cu, and Zn, with the concentration of each metal salt being 0.1 mol / L. The activated petroleum coke powder and the mixed salt solution are mixed at a ratio of 1 g: 5 mL at 60°C for 4 h, followed by freeze-drying at -40°C for 3 h. After reacting with the aforementioned specific mixed salt solution, the metals adhere to the activated petroleum coke powder, exhibiting excellent synergistic effects during pyrolysis. Fe, Co, and Ni act as strong graphitization catalysts, ensuring the conductivity of the carbon framework. The low-temperature volatilization of Zn, combined with the acid leaching removal of Fe, Co, and Ni nanoparticles, synergistically constructs a hierarchical porous structure, thereby significantly improving the overall performance of the material.

[0027] Step S3: The high-entropy alloy-petroleum coke composite material precursor is subjected to microwave radiation treatment under an inert atmosphere, wherein the microwave radiation power is 500-2000W and the treatment time is 10-40min (preferably 1000W for 20min), to obtain a spherical carbonized precursor. In this process, microwave radiation treatment has a strong selective heating effect on the composite material precursor (especially the high-entropy alloy ions and carbon matrix), instantly generating high temperatures within the particles, causing the precursor to soften and reach a viscous flow state. Subsequently, driven by surface tension, the softened irregular particles spontaneously shrink into thermodynamically stable spheres to reduce their surface energy. Experiments have shown that excessively high microwave power and excessively long treatment time lead to excessively high microwave energy, causing the precursor to experience ultra-high temperatures instantaneously, resulting in over-carbonization and damage to the carbon skeleton structure. Simultaneously, excessively high temperatures cause the high-entropy alloy nanoparticles to migrate, aggregate, and grow, losing their high dispersibility, resulting in larger pores and a significant decrease in microporosity after subsequent acid washing. However, insufficient microwave power and processing time result in inadequate microwave energy, causing only a slight reaction in the precursor and failing to form a robust carbon framework. The product remains predominantly an organic precursor and lacks the high conductivity required for the final material. Furthermore, insufficient energy leads to failure in spheroidization of the product, resulting in its original irregular powder morphology.

[0028] S4. The spherical carbonized precursor is activated at high temperature under an activating atmosphere, followed by acid washing and drying to obtain porous carbon microspheres. The activating atmosphere is a carbon dioxide / water vapor atmosphere, the high-temperature activation treatment temperature is 750-950℃, and the time is 60-300 min. More preferably, the activation treatment is carried out in a tube furnace under a carbon dioxide atmosphere, the pyrolysis treatment temperature is 900℃, the heating rate is 5℃ / min, and the pyrolysis treatment time is 120 min. Experiments have shown that if the pyrolysis treatment temperature is too low or the pyrolysis treatment time is too short, the activation is incomplete. If the pyrolysis treatment temperature is too high or the pyrolysis treatment time is too long, the overall structure may collapse. The main reaction between CO2 and carbon is: C + CO2 → 2CO. This is a strongly endothermic reaction with a relatively slow reaction rate, and the reaction is mild and easy to control. First, CO2 gas molecules diffuse to the active sites (high-entropy alloy nanoparticles) on the surface of the carbon spheres and react. Through their highly efficient catalytic effect, they significantly reduce the activation energy of the carbon gasification reaction, preferentially catalyzing the reaction between the surrounding amorphous carbon and CO2, and then gradually penetrating inwards. During this catalytic process, due to the extremely small size and uniform distribution of the high-entropy alloy particles, this catalytic etching generates a large number of uniformly distributed micropores throughout the carbon spheres, thereby greatly increasing the specific surface area while maintaining the integrity of the pore structure and avoiding the formation of macropores that would damage the structure. The acid washing treatment uses a mixed solution of hydrochloric acid and nitric acid with a concentration of 1-3 mol / L, stirred for 1-2 hours. More preferably, the concentration of the hydrochloric acid and nitric acid mixed solution is 2 mol / L, and the acid washing time is 1.5 hours. The above-mentioned acid concentration and treatment time ensure the purity of the material.

[0029] In summary, the relevant reaction mechanism in the preparation process of this invention is as follows: In the above preparation method, high-energy electrons, ions, and active free radicals (such as ·O, ·OH, etc.) generated in plasma bombard the surface of petroleum coke powder. These high-energy particles transfer energy to the carbon atoms on the surface of the petroleum coke, causing the CH and CC bonds to break and form dangling bonds. Subsequently, active oxygen-containing species in the plasma atmosphere combine with these dangling bonds, thereby introducing oxygen-containing functional groups such as carbonyl (C=O), carboxyl (-COOH), and hydroxyl (-OH) in situ and uniformly onto the surface of the petroleum coke. This provides sufficient "anchoring points" for the subsequent metal ion complexation. Various metal ions with different radii and electronegativity undergo complexation reactions with the oxygen-containing functional groups on the surface of the petroleum coke, forming a complex coordination network. In the subsequent heat treatment process, this multi-metal complex structure hinders the migration and grain growth of single metal species. Due to the extremely high mixing entropy of high-entropy systems, they tend to form stable solid solution phases rather than separated metal elements or simple binary alloys. This means that the final product formed in the carbon matrix will be extremely small and uniformly distributed high-entropy alloy nanoparticles. Furthermore, the polar functional groups and metal ions contained in the activated petroleum coke precursor are excellent microwave absorbers. In the microwave field, the material heats up uniformly from the inside out in a very short time. When the temperature reaches the softening point of the organic components in the precursor, surface tension begins to dominate, driving the irregular precursor particles to automatically shrink into perfect spheres. Simultaneously, the rapid thermal effect of microwaves makes the pyrolysis reaction intense and brief, facilitating the rapid removal of volatile components, creating initial pores within the spheres, and promoting rapid cross-linking and solidification of the carbon skeleton, initially forming a carbon network with fewer defects and a dense structure. Finally, during the high-temperature activation stage, different metal components exhibit different catalytic activities for the gasification reaction of carbon (C + CO2 → 2CO). As a multifunctional catalytic platform, the high-entropy alloy nanoparticles, during the heating process, allow different metal components to sequentially or synergistically catalyze the gasification reaction of the surrounding amorphous carbon. This relay-race-style etching process can more efficiently etch a large number of micropores into the carbon framework, forming a hierarchical multi-level porous structure, thereby significantly improving the specific surface area and microporosity of the final product. The three-dimensional network structure of the porous carbon microspheres provides a uniformly dispersed framework for silicon nanoparticles, and its high mechanical strength can effectively alleviate stress concentration caused by volume expansion of silicon during charging and discharging, inhibit electrode pulverization, and significantly improve cycle life.

[0030] The porous carbon microspheres prepared by the above method have a specific surface area of ​​not less than 1900 m². 2 The porous carbon microspheres have a surface area of ​​not less than 2000 m² / g, a microporosity of not less than 82%, and an electrical conductivity of not less than 4 S / mm. Preferably, the specific surface area of ​​the porous carbon microsphere material is not less than 2000 m² / g. 2 / g, microporosity not less than 85%, electrical conductivity not less than 4.5S / mm.

[0031] The aforementioned porous carbon microsphere material can be applied to lithium-ion batteries. A silicon-carbon anode material is prepared by depositing silane / acetylene onto the porous carbon microsphere material using vapor deposition. This material is then assembled into a half-cell and subjected to constant current charge-discharge testing to evaluate its electrochemical performance. At a current density of 0.1 A / g, the reversible capacity of the lithium-ion half-cell is no less than 1600 mAh / g, and the stability retention rate after 300 cycles is no less than 80%.

[0032] The following is a further explanation using specific embodiments.

[0033] Example 1 S1. Crush the petroleum coke using a ball mill (120 min, 500 rpm), pass it through a 300-mesh sieve to obtain petroleum coke powder with a particle size of 10 μm; place the petroleum coke powder into a plasma treatment device for activation (oxygen atmosphere, 500 W power, 30 min) to obtain activated petroleum coke powder.

[0034] S2. Preparation of mixed salt solution: Dissolve soluble ferric chloride salt, cobalt salt, nickel salt, copper salt and zinc salt in water to prepare a mixed salt solution with a metal ion concentration of 0.1 mol / L; mix the activated petroleum coke powder with the mixed salt solution at a solid-liquid ratio of 1 g: 5 mL, stir and react at 60℃ for 4 h to obtain a high-entropy alloy-petroleum coke composite material solution, and freeze-dry the solution (process parameters: rotation speed 200 rpm, temperature -40℃, treatment for 180 min) to obtain the high-entropy alloy-petroleum coke composite material precursor.

[0035] S3. The high-entropy alloy-petroleum coke composite material precursor was placed in a medium-sized microwave atmosphere furnace for microwave radiation treatment, and an inert gas was introduced. The microwave radiation power was 1000W and the treatment time was 20min to obtain a carbonized precursor with a spherical structure.

[0036] S4. The spherical carbonized precursor was heated to 900℃ for 120 min under a carbon dioxide atmosphere at a heating rate of 5℃ / min. After the pyrolysis was completed, it was acid washed with a 2mol / L mixed solution of hydrochloric acid and nitric acid and dried to form porous carbon microspheres (PC-20-900).

[0037] Example 2 S1. Crush the petroleum coke using a ball mill (120 min, 500 rpm), pass it through a 300-mesh sieve to obtain petroleum coke powder with a particle size of 10 μm; place the petroleum coke powder into a plasma treatment device for activation (oxygen atmosphere, 500 W power, 30 min) to obtain activated petroleum coke powder.

[0038] S2. Preparation of mixed salt solution: Dissolve soluble ferric chloride salt, cobalt salt, nickel salt, copper salt and zinc salt in water to prepare a mixed salt solution with a metal ion concentration of 0.1 mol / L; mix the activated petroleum coke powder with the mixed salt solution at a solid-liquid ratio of 1 g: 5 mL, stir and react at 60℃ for 4 h to obtain a high-entropy alloy-petroleum coke composite material solution, and freeze-dry the solution (process parameters: rotation speed 200 rpm, temperature -40℃, treatment for 180 min) to obtain the high-entropy alloy-petroleum coke composite material precursor.

[0039] S3. The high-entropy alloy-petroleum coke composite material precursor was placed in a medium-sized microwave atmosphere furnace for microwave radiation treatment, and an inert gas was introduced. The microwave radiation power was 1000W and the treatment time was 30min to obtain a carbonized precursor with a spherical structure.

[0040] S4. The spherical carbonized precursor was heated to 900℃ for 120 min under a carbon dioxide atmosphere at a heating rate of 5℃ / min. After the pyrolysis was completed, it was acid washed with a 2mol / L mixed solution of hydrochloric acid and nitric acid and dried to form porous carbon microspheres (PC-30-900).

[0041] Example 3 S1. Crush the petroleum coke using a ball mill (120 min, 500 rpm), pass it through a 300-mesh sieve to obtain petroleum coke powder with a particle size of 10 μm; place the petroleum coke powder into a plasma treatment device for activation (oxygen atmosphere, 500 W power, 30 min) to obtain activated petroleum coke powder.

[0042] S2. Preparation of mixed salt solution: Dissolve soluble ferric chloride salt, cobalt salt, nickel salt, copper salt and zinc salt in water to prepare a mixed salt solution with a metal ion concentration of 0.1 mol / L; mix the activated petroleum coke powder with the mixed salt solution at a solid-liquid ratio of 1 g: 5 mL, stir and react at 60℃ for 4 h to obtain a high-entropy alloy-petroleum coke composite material solution, and freeze-dry the solution (process parameters: rotation speed 200 rpm, temperature -40℃, treatment for 180 min) to obtain the high-entropy alloy-petroleum coke composite material precursor.

[0043] S3. The high-entropy alloy / petroleum coke composite material precursor was placed in a medium-sized microwave atmosphere furnace for microwave radiation treatment, and an inert gas was introduced. The microwave radiation power was 1000W and the treatment time was 40min to obtain a carbonized precursor with a spherical structure.

[0044] S4. The spherical carbonized precursor was heated to 900℃ for 120 min under a carbon dioxide atmosphere at a heating rate of 5℃ / min. After the pyrolysis was completed, it was acid washed with a 2mol / L mixed solution of hydrochloric acid and nitric acid and dried to form porous carbon microspheres (PC-40-900).

[0045] Example 4 S1. Crush the petroleum coke using a ball mill (120 min, 500 rpm), pass it through a 300-mesh sieve to obtain petroleum coke powder with a particle size of 10 μm; place the petroleum coke powder into a plasma treatment device for activation (oxygen atmosphere, 500 W power, 30 min) to obtain activated petroleum coke powder.

[0046] S2. Preparation of mixed salt solution: Dissolve soluble ferric chloride salt, cobalt salt, nickel salt, copper salt and zinc salt in water to prepare a mixed salt solution with a metal ion concentration of 0.1 mol / L; mix the activated petroleum coke powder with the mixed salt solution at a solid-liquid ratio of 1 g: 5 mL, stir and react at 60℃ for 4 h to obtain a high-entropy alloy-petroleum coke composite material solution, and freeze-dry the solution (process parameters: rotation speed 200 rpm, temperature -40℃, treatment for 180 min) to obtain the high-entropy alloy-petroleum coke composite material precursor.

[0047] S3. The high-entropy alloy-petroleum coke composite material precursor was placed in a medium-sized microwave atmosphere furnace for microwave radiation treatment, and an inert gas was introduced. The microwave radiation power was 1000W and the treatment time was 20min to obtain a carbonized precursor with a spherical structure.

[0048] S4. The spherical carbonized precursor was heated to 850℃ for high-temperature activation pyrolysis for 120 min under a carbon dioxide atmosphere at a heating rate of 5℃ / min. After pyrolysis, it was acid washed with a 2mol / L mixed solution of hydrochloric acid and nitric acid and dried to form porous carbon microspheres (PC-20-850).

[0049] Example 5 S1. Crush the petroleum coke using a ball mill (120 min, 500 rpm), pass it through a 300-mesh sieve to obtain petroleum coke powder with a particle size of 10 μm; place the petroleum coke powder into a plasma treatment device for activation (oxygen atmosphere, 500 W power, 30 min) to obtain activated petroleum coke powder.

[0050] S2. Preparation of mixed salt solution: Dissolve soluble ferric chloride salt, cobalt salt, nickel salt, copper salt and zinc salt in water to prepare a mixed salt solution with a metal ion concentration of 0.1 mol / L; mix the activated petroleum coke powder with the mixed salt solution at a solid-liquid ratio of 1 g: 5 mL, stir and react at 60℃ for 4 h to obtain a high-entropy alloy-petroleum coke composite material solution, and freeze-dry the solution (process parameters: rotation speed 200 rpm, temperature -40℃, treatment for 180 min) to obtain the high-entropy alloy-petroleum coke composite material precursor.

[0051] S3. The high-entropy alloy-petroleum coke composite material precursor was placed in a medium-sized microwave atmosphere furnace for microwave radiation treatment, and an inert gas was introduced. The microwave radiation power was 1000W and the treatment time was 20min to obtain a carbonized precursor with a spherical structure.

[0052] S4. The spherical carbonized precursor was heated to 950℃ for high-temperature activation pyrolysis for 120 min under a carbon dioxide atmosphere at a heating rate of 5℃ / min. After pyrolysis, it was acid washed with a 2mol / L mixed solution of hydrochloric acid and nitric acid and dried to form porous carbon microspheres (PC-20-950).

[0053] Comparative Example 1 S1. Crush the petroleum coke using a ball mill (120 min, 500 rpm), and pass it through a 300-mesh sieve to obtain petroleum coke powder with a particle size of 10 μm.

[0054] S2. Preparation of mixed salt solution: Dissolve soluble ferric chloride salt, cobalt salt, nickel salt, copper salt and zinc salt in water to prepare a mixed salt solution with a metal ion concentration of 0.1 mol / L; mix the above petroleum coke powder with the mixed salt solution at a solid-liquid ratio of 1 g: 5 mL, stir and react at 60℃ for 4 h to obtain a high-entropy alloy-petroleum coke composite material solution, and freeze-dry the solution (process parameters: rotation speed 200 rpm, temperature -40℃, treatment for 180 min) to obtain the high-entropy alloy-petroleum coke composite material precursor.

[0055] S3. The high-entropy alloy-petroleum coke composite material precursor was placed in a medium-sized microwave atmosphere furnace for microwave radiation treatment, and an inert gas was introduced. The microwave radiation power was 1000W and the treatment time was 20min to obtain a carbonized precursor with a spherical structure.

[0056] S4. The spherical carbonized precursor was heated to 900℃ for 120 min under a carbon dioxide atmosphere at a heating rate of 5℃ / min. After the pyrolysis was completed, it was acid washed with a 2 mol / L mixed solution of hydrochloric acid and nitric acid and dried to form porous carbon microspheres (PC-1).

[0057] Comparative Example 2 S1. Crush the petroleum coke using a ball mill (120 min, 500 rpm), pass it through a 300-mesh sieve to obtain petroleum coke powder with a particle size of 10 μm; place the petroleum coke powder into a plasma treatment device for activation (oxygen atmosphere, 500 W power, 30 min) to obtain activated petroleum coke powder.

[0058] S2. Preparation of mixed salt solution: Dissolve soluble ferric chloride salt, cobalt salt, nickel salt, copper salt and zinc salt in water to prepare a mixed salt solution with a metal ion concentration of 0.1 mol / L; mix the activated petroleum coke powder with the mixed salt solution at a solid-liquid ratio of 1 g: 5 mL, stir and react at 60℃ for 4 h to obtain a high-entropy alloy-petroleum coke composite material solution, and freeze-dry the solution (process parameters: rotation speed 200 rpm, temperature -40℃, treatment for 180 min) to obtain the high-entropy alloy-petroleum coke composite material precursor.

[0059] S3. The high-entropy alloy-petroleum coke composite material precursor was heated to 900℃ for 120 min under a carbon dioxide atmosphere at a heating rate of 5℃ / min. After the pyrolysis was completed, it was acid washed with a 2mol / L mixed solution of hydrochloric acid and nitric acid and dried to form porous carbon microspheres (PC-2).

[0060] Performance testing 1. The porous carbon microspheres obtained in the examples were subjected to SEM testing. Taking Example 1 as an example, the test results are as follows: Figure 1 As shown, PC-20-900 has a spherical structure.

[0061] 2. According to GB / T19587-2017 "Determination of Specific Surface Area and Pore Size Distribution of Porous Solid Materials by Gas Adsorption Method", nitrogen adsorption / desorption tests were performed on the examples and comparative examples. The test results are as follows: Figure 2 As shown in Table 1, where Figure 2 The specific surface area of ​​PC-20-900 obtained in Example 1 is 2361 m². 2 / g, with a microporosity of 91.7%.

[0062] 3. The conductivity of the porous carbon microspheres obtained in the examples and comparative examples was tested according to GB / T24525-2009: "Method for Determination of Resistivity of Carbon Materials". The test results are shown in Table 1.

[0063] 4. To evaluate the feasibility of the examples and comparative examples as lithium battery anode materials, a silicon-carbon anode material with 51% silicon content (e.g., PC-20-900 / Si / C) was prepared by depositing silane / acetylene onto the porous carbon material of this example using vapor deposition. The battery was then assembled and subjected to constant current charge-discharge tests to evaluate its electrochemical performance. The specific battery assembly method is as follows: Anode slurry was prepared by mixing silicon-carbon anode material (e.g., PC-20-900 / Si / C), carbon black, and CMC binder in an 8:1:1 ratio. This slurry was then coated onto copper foil using a scraper, vacuum-dried at 60°C for 24 hours, and cut into circular electrode sheets with a diameter of 12 mm. A lithium metal sheet (12 mm in diameter and 0.5 mm thick) was used. The separator was made of glass fiber (Whatman, 20 mm). The electrolyte was 1 M LiPF6 (dissolved in a mixed solvent of EC:DMC = 1:1). The components are assembled in the following order: negative electrode, electrolyte, separator, electrolyte, and lithium metal sheet, to form a CR2032 battery. The electrochemical performance of the CR2032 battery was tested. Taking the porous carbon microsphere material obtained in Example 1 as an example, the corresponding battery, at a current density of 0.1 A / g, had a reversible capacity of 1737 mAh / g and a stability retention rate of 88% after 300 cycles. Figure 3 As shown, the electrical performance results of the batteries prepared according to the above method in each embodiment and comparative example are shown in Table 1.

[0064] Table 1 Performance data of porous carbon materials and corresponding lithium batteries in the examples and comparative examples. Comparing Examples 1, 2, and 3 reveals that excessively long microwave treatment times result in excessively high microwave energy, causing the precursor to experience ultra-high temperatures instantaneously. This leads to over-carbonization and damage to the carbon skeleton structure, resulting in micropore collapse and a decrease in specific surface area. Simultaneously, excessively high microwave energy may cause the breakage of weaker C / C bonds in the carbon skeleton, creating defects and thus reducing electrical conductivity. It is evident that microwave radiation treatment time significantly impacts the electrochemical properties, specific surface area, microporosity, and electrical conductivity of the material. A microwave radiation treatment time of 20 minutes represents the optimal induction time for the preparation process of this invention.

[0065] By comparing Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that specific preparation processes have a significant impact on the material structure. The absence of petroleum coke activation and microwave treatment leads to a substantial decrease in specific surface area, microporosity, and electrical conductivity. This demonstrates that the various steps in this invention work synergistically. The initial activation treatment provides corresponding anchoring points, ensuring uniform distribution of metal ions. Microwave radiation treatment then induces a pyrolysis reaction, creating voids within the spheres and promoting rapid cross-linking and solidification of the carbonaceous framework. Finally, high-temperature activation treatment forms a hierarchical porous structure. Furthermore, the specific surface area and microporosity of the material play a crucial role in its electrochemical performance. High specific surface area and microporosity provide a buffer space for the volume expansion of silicon during lithium intercalation, effectively alleviating stress concentration and reducing electrode structure damage caused by volume expansion. Simultaneously, it reduces direct contact between silicon and the electrolyte, decreasing irreversible side reactions and thus improving the material's electrochemical performance. The electrical conductivity of the material also plays a vital role in its electrochemical performance; high conductivity significantly improves the material's capacity and cycle performance.

[0066] As can be seen from the above embodiments and comparative examples, the porous carbon material obtained by the microwave-induced high-entropy alloy-petroleum coke preparation method of the present invention has the characteristics of high specific surface area, high microporosity, and excellent electrical conductivity. In particular, in terms of electrical conductivity, the porous carbon material obtained by the method of this application has a stable electrical conductivity of more than 4 S / mm, which is much higher than the electrical conductivity of the material obtained in the comparative example, with a minimum increase of 90% and a maximum increase of 185%.

[0067] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. However, it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke, characterized in that, The method includes the following steps: S1. The pulverized and sieved petroleum coke powder is subjected to low-temperature plasma activation treatment to obtain activated petroleum coke powder. S2. The activated petroleum coke powder is mixed and reacted with a salt solution containing at least 5 transition metals, and then freeze-dried to obtain a high-entropy alloy-petroleum coke composite material precursor. S3. The high-entropy alloy-petroleum coke composite material precursor is subjected to microwave radiation treatment under an inert atmosphere to obtain a carbonized precursor with a spherical structure. S4. The carbonized precursor with the spherical structure is activated at high temperature under an activating atmosphere, and then acid washed and dried to obtain porous carbon microsphere material.

2. The method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke according to claim 1, characterized in that, In step S1, the low-temperature plasma activation treatment includes: The activation treatment atmosphere is air, oxygen, or a mixture of both. The activation power is 50~1000W; The processing time is 10~60 minutes.

3. The method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke according to claim 1, characterized in that, The transition metals include: Fe, Co, Ni, Cu, Zn, Mn, Cr, and Mo.

4. The method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke according to claim 1, characterized in that, The solid-liquid ratio of the activated petroleum coke powder to the salt solution is 1g:5-10mL; The concentration of each metal salt in the salt solution is 0.1 ~ 0.5 mol / L; The process parameters for the mixing reaction are: temperature 30°C ~ 60°C; reaction time 2 ~ 4 h.

5. The method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke according to claim 1, characterized in that, The freeze-drying temperature is -20 to -60°C, and the time is 2 to 6 hours.

6. The method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke according to claim 1, characterized in that, In step S3, the power of microwave radiation is 500~2000W, and the time is 10~40min.

7. The method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke according to claim 1, characterized in that, In step S4, the high-temperature activation treatment is performed by activating the material at a temperature of 750-950°C for 60-300 minutes under a carbon dioxide or water vapor atmosphere.

8. The method for preparing porous carbon microspheres using microwave-induced high-entropy alloy-petroleum coke according to claim 1, characterized in that, In step S4, the acid washing process involves stirring the product after high-temperature activation in a mixed solution of hydrochloric acid and nitric acid with a concentration of 1-3 mol / L for 1-2 hours.

9. The porous carbon microspheres obtained by the preparation method according to any one of claims 1 to 8, characterized in that, The specific surface area of ​​the porous carbon microspheres is not less than 1900 m². 2 / g, microporosity not less than 82%, electrical conductivity not less than 4S / mm.

10. The application of the porous carbon microspheres as described in claim 9 in lithium-ion battery anode materials.

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