A carbon microsphere, its preparation method and application

Abstract

This invention belongs to the field of carbon microsphere preparation technology, specifically relating to a carbon microsphere, its preparation method, and its application. The preparation method of the carbon microspheres of this invention includes: (1) dissolving resin and an acidic catalyst in an alcohol solvent to form a precursor solution; (2) adding the precursor solution to an oily continuous phase for emulsification to prepare an emulsion; (3) heating and curing the emulsion to form resin microspheres; and (4) separating, cleaning, drying, and carbonizing the resin microspheres to obtain carbon microspheres. The key to this invention lies in significantly shortening the curing time of the resin microspheres through the selection of a specific catalyst; simultaneously, by precisely controlling the emulsification speed and curing reaction conditions, the particle size and microstructure of the obtained carbon microspheres can be effectively controlled. The prepared carbon microspheres can be used as electrode active materials for supercapacitors. Electrodes prepared using these carbon microspheres as electrode active materials exhibit a specific capacitance of 200~300 F / g in a 6M KOH aqueous solution.

Description

Technical Field

[0001] This invention belongs to the field of carbon microsphere preparation technology, specifically relating to a carbon microsphere, its preparation method, and its application. Background Technology

[0002] Carbon-based functional materials have demonstrated significant application value in various fields due to their unique physicochemical properties. Among them, carbon spheres, as an extremely important carbon material, possess high specific surface area, excellent conductivity, good structural stability, and fluidity, making them promising for applications in energy storage (such as supercapacitors, lithium-sulfur batteries, sodium-ion batteries, and silicon-carbon anodes), multiphase catalytic reaction systems, gas adsorption and separation, and electromagnetic wave absorption materials.

[0003] The current mainstream preparation techniques for carbon spheres include: (1) hydrothermal synthesis: carbon spheres are formed through the self-assembly of precursors such as sugars; (2) template-guided method: the microsphere structure is controlled by hard templates such as silica or soft templates such as surfactants; (3) spray drying method: precursor microspheres are formed by rapid solvent evaporation; (4) suspension polymerization method: microsphere morphology is constructed based on the oil-water interface. Although the above methods are relatively mature in the preparation of nanoscale carbon spheres, micron-scale carbon spheres are more favored in practical applications due to their superior solid-liquid separation performance and processing adaptability.

[0004] In existing processes for preparing micron-sized carbon spheres (carbon microspheres), suspension polymerization is widely used due to its simplicity. This method typically involves dispersing a precursor solution in a continuous phase medium to form a stable emulsion, followed by prolonged heating and curing (10–24 h) to solidify the microsphere structure, and finally high-temperature carbonization to obtain the carbon microspheres. However, the lengthy curing process prolongs the production cycle and increases energy consumption, severely hindering its economic viability for commercial production. Secondly, existing processes struggle to overcome the limitation of a single microsphere structure, resulting in mostly solid or hollow structures. These two types of carbon microspheres have low specific surface areas and simple pore structures (mostly micropores), leading to low utilization of active sites and slow mass transport efficiency. An effective solution to this problem is to construct complex structures (such as porous, network, multi-shell, core-shell structures, etc.) within the carbon spheres. These carbon microspheres with complex internal structures can significantly increase the specific surface area of ​​the microspheres, and they often possess abundant micropores and mesopores, thereby effectively improving the utilization of active sites and mass transport efficiency, which plays a crucial role in enhancing the performance of carbon microspheres. Therefore, it is of great significance to develop carbon microsphere preparation technology with rapid prototyping characteristics and complex internal structures. Summary of the Invention

[0005] This invention aims to provide carbon microspheres, their preparation method, and applications. It primarily uses commercially available resins as raw materials, organic or inorganic acids as catalysts, and alcohols as organic solvents. By controlling parameters such as the ratio, curing temperature, and carbonization temperature, carbon microspheres with different microstructures and particle sizes are prepared. This invention solves the problems of long curing cycles and monotonous carbon sphere structures in current suspension polymerization methods. To achieve the above objectives, the carbon microsphere preparation method of this invention includes the following steps:

[0006] (1) Preparation of precursor solution: The resin and acid catalyst are dissolved in an alcohol solvent to obtain a precursor solution; the mass ratio of resin to acid catalyst is 200:1~1:1; the mass ratio of alcohol solvent to resin is 10:1~1:5;

[0007] (2) Emulsion preparation: The precursor solution obtained in step (1) is added to the oily continuous phase and emulsified at a stirring speed of 3000~20000 r / min, preferably 4000~15000 r / min; the emulsification time is 1~30 min, preferably 10~30 min; and an emulsion is prepared.

[0008] The mass ratio of the oily continuous phase to the precursor solution is 30:1 to 1:1, preferably 10:1 to 5:1;

[0009] (3) Resin curing: The emulsion obtained in step (2) is heated to a temperature of 70~180℃ for a time of 5min~1h, preferably 10~40min; the resin in the emulsion is cured into resin microspheres.

[0010] (4) Solid-liquid separation;

[0011] (5) Drying of resin microspheres: The solid product after solid-liquid separation in step (4) is washed and dried to obtain dry resin microspheres; the drying temperature is 60~200℃, preferably 100~120℃; the drying time is 30min~6h, preferably 1~2h.

[0012] (6) High-temperature carbonization: The dry resin microspheres obtained in step (5) are placed in a vacuum or inert atmosphere for high-temperature carbonization. The carbonization temperature is 500~1500℃, preferably 600~1000℃; the carbonization heating rate is 1~10℃ / min, preferably 2~6℃ / min; the carbonization holding time is 1~10h, preferably 2~4h; and finally, carbon microsphere products are obtained.

[0013] Further, the resin mentioned in step (1) is one or more of the following: melamine-formaldehyde resin, phosphorus-modified melamine-formaldehyde resin, boron-modified melamine-formaldehyde resin, sulfur-modified melamine-formaldehyde resin, phenolic resin, boron-modified phenolic resin, silicon-modified phenolic resin, silicon-boron-modified phenolic resin, and chitosan-modified phenolic resin.

[0014] The acidic catalyst is one or more of formic acid, acetic acid, benzoic acid, hydrochloric acid, terephthalic acid, p-hydroxybenzenesulfonic acid, p-methylbenzenesulfonic acid, p-hydroxybenzoic acid, and p-methylbenzoic acid.

[0015] The alcohol solvent is one or more of ethylene glycol, glycerol, isopropanol and n-propanol.

[0016] Further, the oily continuous phase in step (2) is one or more of dimethyl silicone oil, phenylmethyl silicone oil, epoxy silicone oil, and industrial white oil.

[0017] Furthermore, the cleaning solution used in step (5) is one or more of solvent oil, benzene, xylene and kerosene.

[0018] Further, the inert atmosphere in step (6) is one or both of nitrogen and argon, and the gas flow rate is 1~10L / min, preferably 2~5L / min; the vacuum condition is a vacuum degree ≤0.1kPa.

[0019] Carbon microspheres prepared according to the method of the present invention have a particle diameter of 1-30 μm and a specific surface area of ​​300-700 m². 2 / g; By controlling the curing temperature and the ratio of resin, acidic catalyst, and alcohol solvent, a variety of different micromorphologies can be formed:

[0020] When the ratio of resin to acidic catalyst is 30:1 to 10:1, the ratio of alcohol solvent to resin is 3:1 to 1:2, and the curing temperature is 70 to 140 ℃, the carbon microspheres have a shell-less aerogel structure.

[0021] When the ratio of resin to acidic catalyst is 9:1 to 6:1, the ratio of alcohol solvent to resin is 3:1 to 1:2, and the curing temperature is 70 to 140 ℃, the carbon microspheres have a porous shell-coated aerogel structure.

[0022] When the ratio of resin to acidic catalyst is 5:1 to 3:1, the ratio of alcohol solvent to resin is 3:1 to 1:2, and the curing temperature is 70 to 160 ℃, the carbon microspheres have a dense shell-encapsulated aerogel structure.

[0023] When the ratio of resin to acidic catalyst is 2:1 to 1:1, the ratio of alcohol solvent to resin is 10:1 to 1:2, and the curing temperature is 70 to 180 ℃, the carbon microspheres have a hollow and dense shell structure.

[0024] When the ratio of resin to acidic catalyst is 30:1 to 6:1, the ratio of alcohol solvent to resin is 3:1 to 1:2, and the curing temperature is 160 to 180 ℃, the carbon microspheres have an aerogel shell-hollow structure.

[0025] When the ratio of resin to acidic catalyst is 200:1 to 1:1, the ratio of alcohol solvent to resin is 1:3 to 1:5, and the curing temperature is 70 to 180 ℃, the carbon microspheres have a solid structure.

[0026] The application of carbon microspheres as an electrode active material in supercapacitors: the electrode prepared by the carbon microspheres as the electrode active material has a specific capacitance of 200~300 F / g in 6M KOH aqueous solution.

[0027] This invention provides a rapid and low-cost method for preparing carbon microspheres with controllable morphology. The core design concept involves using suspension polymerization to uniformly disperse a precursor solution in an oil-phase continuous medium, forming micron-sized droplets with controllable particle size (droplet diameter can be adjusted by the speed of the emulsifier). Subsequently, under the catalysis of high temperature and an acidic catalyst, these precursor droplets undergo phase separation in a very short time to form sol-particles. Due to the temperature difference between the surface and core of the precursor droplets, the resulting temperature gradient causes uneven tension on the surface of the sol-particles, producing the Margoli effect. The sol-particles gradually migrate to the surface of the precursor droplets, continuously fusing together to form a shell. When the temperature gradient disappears, the sol-particles that have not completely migrated to the surface undergo a gelation reaction, forming an internal three-dimensional network structure. Therefore, by controlling the heating parameters and raw material ratio, rapid solidification of the microspheres can be achieved, and the morphology and structure of the microspheres can be adjusted according to actual needs. Finally, carbon microspheres are obtained through high-temperature carbonization. This method uses low-cost raw materials, has a simple and efficient process, and a short preparation cycle, making it potential for large-scale commercial production.

[0028] The advantages and beneficial effects of this invention are as follows:

[0029] 1. The key to this invention lies in significantly shortening the curing time of resin microspheres by selecting specific catalysts; at the same time, by precisely controlling the emulsification speed and curing reaction conditions, the particle size and microstructure of the obtained carbon microspheres can be effectively controlled.

[0030] 2. By systematically regulating key process parameters, this invention can precisely induce and control the formation and evolution of the microstructure inside the resin microspheres during the curing process, thereby flexibly and adjustablely realizing the diversified customization of the final morphology of carbon microspheres.

[0031] 3. This invention uses commercially available resins as raw materials, and the method is applicable to a variety of different resins, exhibiting high versatility. Furthermore, compared to traditional processes that use monomer synthesis to prepare carbon spheres, this method has lower raw material costs and a shorter production cycle.

[0032] 4. The carbon microspheres prepared by this invention have a complex internal structure. Compared with hollow or solid carbon spheres of the same particle size, they have a higher specific surface area, lighter weight, and greater specific strength. They also have abundant mesopores and micropores, which can improve the utilization rate of active sites and the efficiency of material transport.

[0033] 5. The carbon microspheres prepared by this invention have a particle diameter of 1~30 μm and a specific surface area of ​​approximately 300~700 m². 2 The electrode prepared using this carbon microsphere as the active material for a supercapacitor has a specific capacitance of 200~300 F / g in a 6M KOH aqueous solution. Attached Figure Description

[0034] Figure 1 Microstructure and electrochemical properties of porous shell-coated aerogel-structured carbon microspheres prepared in Example 1: (a) Scanning electron microscope macroscopic image; (b) Scanning electron microscope internal structure image; (c) Nitrogen isothermal adsorption-desorption curve; (d) Constant current charge-discharge curve;

[0035] Figure 2 Microstructure and electrochemical properties of the dense shell-coated aerogel-structured carbon microspheres prepared in Example 2: (a) Scanning electron microscope macroscopic image; (b) Scanning electron microscope internal structure image; (c) Nitrogen isothermal adsorption-desorption curve; (d) Constant current charge-discharge curve;

[0036] Figure 3 Microstructure and electrochemical properties of the aerogel shell-hollow carbon microspheres prepared in Example 3: (a) Scanning electron microscope macroscopic image; (b) Scanning electron microscope internal structure image; (c) Nitrogen isothermal adsorption-desorption curve; (d) Constant current charge-discharge curve;

[0037] Figure 4 Microstructure and electrochemical properties of the shell-free aerogel carbon microspheres prepared in Example 4: (a) Scanning electron microscope macroscopic image; (b) Scanning electron microscope internal structure image; (c) Nitrogen isothermal adsorption-desorption curve; (d) Constant current charge-discharge curve;

[0038] Figure 5 Scanning electron microscope image of solid carbon microspheres prepared in Example 5;

[0039] Figure 6 Scanning electron microscope image of hollow dense shell carbon microspheres prepared in Example 6;

[0040] Figure 7 Scanning electron microscope image of carbon particles prepared for Comparative Example 1;

[0041] Figure 8Scanning electron microscope image of the carbon bulk material prepared for Comparative Example 2. Detailed Implementation

[0042] To further understand the present invention, the following description is based on embodiments. However, the embodiments are only for further illustrating the features and advantages of the present invention, and are not intended to limit the technical solutions of the present invention.

[0043] Example 1

[0044] In this embodiment, the carbon microspheres are prepared as follows:

[0045] (1) Weigh 100 g of commercially available phenolic resin and 15 g of acetic acid, and add them to 300 g of ethylene glycol. Stir continuously at room temperature until the phenolic resin and acetic acid are completely dissolved to obtain a homogeneous and transparent precursor solution.

[0046] (2) Weigh 200 g of precursor solution and add it to 2000 g of 100# industrial white oil (purchased from Hongtai Petrochemical Co., Ltd.). At room temperature, use a high-speed emulsifier at a speed of 6000 r / min to emulsify the mixture for 10 min to obtain a stable white oil-in-alcohol emulsion.

[0047] (3) The obtained white emulsion was transferred to a reaction vessel, heated to 100 °C, and kept at this temperature for 10 min. The white emulsion was observed to turn into a pink suspension, indicating that the phenolic resin microspheres had been cured.

[0048] (4) The pink suspension was filtered and separated, and the solid product obtained by filtration was collected. The solid product was washed three times with 120# solvent oil (purchased from Shandong Juxing Chemical Co., Ltd.) to fully remove residual industrial white oil.

[0049] (5) The cleaned solid product was placed in an oven at 100 °C and dried for 1 h to obtain dried phenolic resin microspheres.

[0050] (6) The dried phenolic resin microspheres were placed in a tube furnace and subjected to high-temperature carbonization in a vacuum environment (vacuum degree 0.05 kPa). The carbonization temperature was 1000 ℃, the carbonization holding time was 2 h, and the heating rate was 5 ℃ / min. After carbonization, the microspheres were cooled to room temperature in a vacuum environment to obtain carbon microspheres.

[0051] Electrode preparation:

[0052] (1) Weigh carbon microspheres, carbon black conductive agent and polytetrafluoroethylene binder at a mass ratio of 8:1:1. After mixing the three evenly, add anhydrous ethanol as a dispersion medium and continue stirring until a uniform black slurry with good flowability is formed.

[0053] (2) The obtained black slurry was uniformly coated onto the surface of the nickel foam current collector, and then the coated nickel foam current collector was placed in an oven at 100℃ for 12 h to completely remove the ethanol solvent, thus obtaining the nickel foam electrode. The surface loading of the active material (carbon microspheres) on the nickel foam electrode was controlled to be approximately 1 mg / cm². 2 .

[0054] (3) The dried foam nickel electrode sheet was compacted using a tablet press. The pressure of the tablet press was set to 15 MPa and the tableting time was 30 s.

[0055] Electrochemical performance characterization:

[0056] Compacted foamed nickel electrode sheet (electrode sheet area: 1 cm²) 2 Using Hg / HgO as the working electrode, a constant current charge-discharge test was conducted in a three-electrode test system (with Hg / HgO as the reference electrode and a platinum sheet electrode as the counter electrode) using a 6 M KOH aqueous solution as the electrolyte. The test voltage window was set from -1.0 V to 0 V (vs. Hg / HgO).

[0057] Figure 1 (a) and (b) are scanning electron microscope images of the carbon microspheres prepared in this embodiment. The images show that the carbon microspheres exhibit a porous shell-encapsulated aerogel structure: the aerogel has an internal three-dimensional nanonetwork structure with particle sizes of 30–40 nm and pore sizes of 10–50 nm; the outer layer is coated with a porous shell with pore sizes of 10–20 nm and a shell thickness of approximately 100 nm. Statistical results show that the average particle size of the carbon microspheres is approximately 5 μm (particle size range of 2–8 μm). Figure 1 (c) shows the nitrogen isothermal adsorption-desorption curves of the carbon microspheres in this embodiment. Calculated using the Brunauer-Emmett-Teller (BET) model, its specific surface area is 592 m². 2 / g. Figure 1 (d) shows the constant current charge-discharge curves of the carbon microspheres in this embodiment at different current densities. According to the formula: specific capacitance = (discharge current × discharge time) / (voltage window), its specific capacitance at a current density of 0.2 A / g is 315 F / g.

[0058] Example 2

[0059] In this embodiment, the carbon microspheres are prepared as follows:

[0060] (1) Weigh 150 g of commercially available phenolic resin and 40 g of p-toluenesulfonic acid and add them to 300 g of ethylene glycol. Stir continuously at room temperature until the phenolic resin and p-toluenesulfonic acid are completely dissolved to obtain a homogeneous and transparent precursor solution.

[0061] (2) Weigh 200 g of precursor solution and add it to 2000 g of dimethyl silicone oil. At room temperature, use a high-speed emulsifier to emulsify the mixture at a speed of 4000 r / min for 10 min to obtain a stable white oil-in-alcohol emulsion.

[0062] (3) The obtained white emulsion was transferred to a reaction vessel, heated to 150 °C, and kept at this temperature for 30 min. The white emulsion was observed to turn into a pink suspension, indicating that the phenolic resin microspheres had been cured.

[0063] (4) The pink suspension was filtered and separated, and the resulting solid product was collected. The solid product was washed three times with 120# solvent oil to fully remove residual dimethyl silicone oil.

[0064] (5) The cleaned solid product was placed in an oven at 100 °C and dried for 1 h to obtain dried phenolic resin microspheres.

[0065] (6) The dried phenolic resin microspheres were placed in a tube furnace and subjected to high-temperature carbonization in an argon atmosphere. The carbonization temperature was 800 ℃, the carbonization holding time was 2 h, the heating rate was 5 ℃ / min, and the argon gas flow rate was 2 L / min. After carbonization, the microspheres were cooled to room temperature in an argon atmosphere to obtain carbon microspheres.

[0066] Electrode preparation:

[0067] (1) Weigh carbon microspheres, carbon black conductive agent and polytetrafluoroethylene binder at a mass ratio of 8:1:1. After mixing the three evenly, add anhydrous ethanol as a dispersion medium and continue stirring until a uniform black slurry with good flowability is formed.

[0068] (2) The obtained black slurry was uniformly coated onto the surface of the nickel foam current collector, and then the coated nickel foam current collector was placed in an oven at 100℃ for 12 h to completely remove the ethanol solvent, thus obtaining the nickel foam electrode. The surface loading of the active material (carbon microspheres) on the nickel foam electrode was controlled to be approximately 1 mg / cm². 2 .

[0069] (3) The dried foam nickel electrode sheet was compacted using a tablet press. The pressure of the tablet press was set to 15 MPa and the tableting time was 30 s.

[0070] Electrochemical performance testing:

[0071] Compacted foamed nickel electrode sheet (electrode sheet area: 1 cm²) 2Using Hg / HgO as the working electrode, a constant current charge-discharge test was conducted in a three-electrode test system (with Hg / HgO as the reference electrode and a platinum sheet electrode as the counter electrode) using a 6 M KOH aqueous solution as the electrolyte. The test voltage window was set from -1.0 V to 0 V (vs. Hg / HgO).

[0072] Figure 2 (a) and (b) are scanning electron microscope images of the carbon microspheres prepared in this embodiment. The images show that the carbon microspheres exhibit a dense shell-encapsulated aerogel structure: the internal aerogel is a three-dimensional nanonetwork structure with particle sizes of 100–150 nm and pore sizes of 30–90 nm; the outer layer is a dense shell with a thickness of approximately 200 nm and pore sizes of less than 2 nm. Statistical results indicate that the average particle size of the carbon microspheres is approximately 8 μm (particle size range of 3–10 μm). Figure 2 (c) shows the nitrogen isothermal adsorption-desorption curves of the carbon microspheres in this embodiment. Calculated using the Brunauer-Emmett-Teller (BET) model, its specific surface area is 678 m². 2 / g. Figure 2 (d) shows the constant current charge-discharge curves of the carbon microspheres in this embodiment at different current densities. According to the formula: specific capacitance = (discharge current × discharge time) / (voltage window), its specific capacitance at a current density of 0.2 A / g is 321 F / g.

[0073] Example 3

[0074] In this embodiment, the carbon microspheres are prepared as follows:

[0075] (1) Weigh 200 g of commercially available boron phenolic resin and 10 g of p-hydroxybenzenesulfonic acid, and add them to 200 g of glycerol. Stir continuously at room temperature until the boron phenolic resin and p-hydroxybenzenesulfonic acid are completely dissolved to obtain a homogeneous and transparent precursor solution.

[0076] (2) Weigh 300 g of precursor solution and add it to 2000 g of terminal epoxy silicone oil. At room temperature, use a high-speed emulsifier to emulsify the mixture at a speed of 8000 r / min for 30 min to obtain a stable white oil-in-alcohol emulsion.

[0077] (3) The obtained white emulsion was transferred to a reaction vessel, heated to 180 °C, and kept at this temperature for 10 min. The white emulsion was observed to turn into a pink suspension, indicating that the boron phenolic resin microspheres had been cured.

[0078] (4) The pink suspension was filtered and separated, and the resulting solid product was collected. The solid product was washed three times with acetone to thoroughly remove residual terminal epoxy silicone oil.

[0079] (5) The cleaned solid product was placed in an oven at 100 °C and dried for 1 h to obtain dried boron phenolic resin microspheres.

[0080] (6) The dried boron phenolic resin microspheres were placed in a tube furnace and subjected to high-temperature carbonization in an argon atmosphere. The carbonization temperature was 1200 ℃, the carbonization holding time was 4 h, the heating rate was 3 ℃ / min, and the argon gas flow rate was 5 L / min. After carbonization, the microspheres were cooled to room temperature in an argon atmosphere to obtain carbon microspheres.

[0081] Electrode preparation:

[0082] (1) Weigh carbon microspheres, carbon black conductive agent and polytetrafluoroethylene binder at a mass ratio of 8:1:1. After mixing the three evenly, add anhydrous ethanol as a dispersion medium and continue stirring until a uniform black slurry with good flowability is formed.

[0083] (2) The obtained black slurry was uniformly coated onto the surface of the nickel foam current collector, and then the coated nickel foam current collector was placed in an oven at 100℃ for 12 h to completely remove the ethanol solvent, thus obtaining the nickel foam electrode. The surface loading of the active material (carbon microspheres) on the nickel foam electrode was controlled to be approximately 1 mg / cm². 2 .

[0084] (3) The dried foam nickel electrode sheet was compacted using a tablet press. The pressure of the tablet press was set to 15 MPa and the tableting time was 30 s.

[0085] Electrochemical performance testing:

[0086] Compacted foamed nickel electrode sheet (electrode sheet area: 1 cm²) 2 Using Hg / HgO as the working electrode, a constant current charge-discharge test was conducted in a three-electrode test system (with Hg / HgO as the reference electrode and a platinum sheet electrode as the counter electrode) using a 6 M KOH aqueous solution as the electrolyte. The test voltage window was set from -1.0 V to 0 V (vs. Hg / HgO).

[0087] Figure 3 (a) and (b) are scanning electron microscope images of the carbon microspheres prepared in this embodiment. The images show that the carbon microspheres exhibit an aerogel shell-hollow structure with a shell thickness of approximately 700 nm, particle sizes of 110–160 nm within the shell, and pore sizes of approximately 40 nm. Statistical results indicate that the average particle size of the carbon microspheres is approximately 4 μm (particle size range of 2–6 μm). Figure 3 (c) shows the nitrogen isothermal adsorption-desorption curves of the carbon microspheres in this embodiment. Calculated using the Brunauer-Emmett-Teller (BET) model, its specific surface area is 500 m².2 / g. Figure 3 (d) shows the constant current charge-discharge curves of the carbon microspheres in this embodiment at different current densities. According to the formula: specific capacitance = (discharge current × discharge time) / (voltage window), its specific capacitance at a current density of 0.2 A / g is 285 F / g.

[0088] Example 4

[0089] In this embodiment, the carbon microspheres are prepared as follows:

[0090] (1) Weigh 200 g of commercially available melamine-formaldehyde resin and 15 g of benzoic acid, and add them to 400 g of ethylene glycol. Stir continuously at room temperature until the melamine-formaldehyde resin and benzoic acid are completely dissolved to obtain a homogeneous and transparent precursor solution.

[0091] (2) Weigh 200 g of precursor solution and add it to 2000 g of dimethyl silicone oil. At room temperature, use a high-speed emulsifier to emulsify the mixture at a speed of 10000 r / min for 20 min to obtain a stable white oil-in-alcohol emulsion.

[0092] (3) The obtained white emulsion was transferred to a reaction vessel, heated to 120 °C, and kept at this temperature for 20 min. The white emulsion was observed to turn into a white suspension, indicating that the melamine-formaldehyde resin microspheres had been cured.

[0093] (4) The white suspension was filtered and separated, and the resulting solid product was collected. The solid product was washed multiple times with acetone to thoroughly remove residual dimethyl silicone oil.

[0094] (5) The cleaned solid product was placed in an oven at 100 °C and dried for 1 h to obtain dried melamine-formaldehyde resin microspheres.

[0095] (6) The dried melamine-formaldehyde resin microspheres were placed in a tube furnace and subjected to high-temperature carbonization under vacuum (0.1 kPa). The carbonization temperature was 1000 °C, the carbonization holding time was 1 h, and the heating rate was 10 °C / min. After carbonization, the microspheres were cooled to room temperature under vacuum to obtain carbon microspheres.

[0096] Electrode preparation:

[0097] (1) Weigh carbon microspheres, carbon black conductive agent and polytetrafluoroethylene binder at a mass ratio of 8:1:1. After mixing the three evenly, add anhydrous ethanol as a dispersion medium and continue stirring until a uniform black slurry with good flowability is formed.

[0098] (2) The obtained black slurry was uniformly coated onto the surface of the nickel foam current collector, and then the coated nickel foam current collector was placed in an oven at 100℃ for 12 h to completely remove the ethanol solvent, thus obtaining the nickel foam electrode. The surface loading of the active material (carbon microspheres) on the nickel foam electrode was controlled to be approximately 1 mg / cm². 2 .

[0099] (3) The dried foam nickel electrode sheet was compacted using a tablet press. The pressure of the tablet press was set to 15 MPa and the tableting time was 30 s.

[0100] Electrochemical performance testing:

[0101] Compacted foamed nickel electrode sheet (electrode sheet area: 1 cm²) 2 Using Hg / HgO as the working electrode, a constant current charge-discharge test was conducted in a three-electrode test system (with Hg / HgO as the reference electrode and a platinum sheet electrode as the counter electrode) using a 6 M KOH aqueous solution as the electrolyte. The test voltage window was set from -1.0 V to 0 V (vs. Hg / HgO).

[0102] Figure 4 (a) and (b) are scanning electron microscope images of the carbon microspheres prepared in this embodiment. The images show that the carbon microspheres have a shell-less aerogel structure with a particle size of 20–40 nm and a pore size of approximately 10–40 nm. Statistical results indicate that the average particle size of the carbon microspheres is approximately 3 μm (particle size range of 1–6 μm). Figure 4 (c) shows the nitrogen isothermal adsorption-desorption curves of the carbon microspheres in this embodiment. Calculated using the Brunauer-Emmett-Teller (BET) model, its specific surface area is 561 m². 2 / g. Figure 4 (d) shows the constant current charge-discharge curves of the carbon microspheres in this embodiment at different current densities. According to the formula: specific capacitance = (discharge current × discharge time) / (voltage window), its specific capacitance at a current density of 0.2 A / g is 232 F / g.

[0103] Example 5

[0104] In this embodiment, the carbon microspheres are prepared as follows:

[0105] (1) Weigh 180 g of commercially available phenolic resin and 24 g of p-hydroxybenzenesulfonic acid and add them to 60 g of ethylene glycol. Stir continuously at room temperature until the phenolic resin and p-hydroxybenzenesulfonic acid are completely dissolved to obtain a homogeneous and transparent precursor solution.

[0106] (2) Weigh 100 g of precursor solution and add it to 2000 g of phenylmethyl silicone oil. At room temperature, use a high-speed emulsifier to emulsify the mixture at a speed of 6000 r / min for 20 min to obtain a stable white oil-in-alcohol emulsion.

[0107] (3) The obtained white emulsion was transferred to a reaction vessel, heated to 180 °C, and kept at this temperature for 25 min. The white emulsion was observed to turn into a pink suspension, indicating that the phenolic resin microspheres had been cured.

[0108] (4) The pink suspension was filtered and separated, and the resulting solid product was collected. The solid product was washed three times with acetone to thoroughly remove residual phenylmethyl silicone oil.

[0109] (5) The cleaned solid product was placed in an oven at 120 °C and dried for 5 h to obtain dried phenolic resin microspheres.

[0110] (6) The dried phenolic resin microspheres were placed in a tube furnace and subjected to high-temperature carbonization under vacuum (0.1 kPa). The carbonization temperature was 800 °C, the carbonization holding time was 2 h, and the heating rate was 10 °C / min. After carbonization, the microspheres were cooled to room temperature under vacuum to obtain carbon microspheres.

[0111] Figure 5 This is a scanning electron microscope image of the carbon microspheres prepared in this embodiment. The image shows that the carbon microspheres have a solid structure with no obvious pores on the surface and a dense, solid interior. Statistical results indicate that the average particle size of the carbon microspheres is approximately 4 μm (particle size range of 2–8 μm).

[0112] Example 6

[0113] In this embodiment, the carbon microspheres are prepared as follows:

[0114] (1) Weigh 180 g of commercially available phenolic resin and 90 g of p-hydroxybenzoic acid and add them to 360 g of ethylene glycol. Stir continuously at room temperature until the phenolic resin and p-hydroxybenzoic acid are completely dissolved to obtain a homogeneous and transparent precursor solution.

[0115] (2) Weigh 100 g of precursor solution and add it to 2000 g of phenylmethyl silicone oil. At room temperature, use a high-speed emulsifier to emulsify the mixture at a speed of 6000 r / min for 20 min to obtain a stable white oil-in-alcohol emulsion.

[0116] (3) The obtained white emulsion was transferred to a reaction vessel, heated to 160 °C, and kept at this temperature for 25 min. The white emulsion was observed to turn into a pink suspension, indicating that the phenolic resin microspheres had been cured.

[0117] (4) The pink suspension was filtered and separated, and the resulting solid product was collected. The solid product was washed three times with acetone to thoroughly remove residual phenylmethyl silicone oil.

[0118] (5) The cleaned solid product was placed in an oven at 120 °C and dried for 5 h to obtain dried phenolic resin microspheres.

[0119] (6) The dried phenolic resin microspheres were placed in a tube furnace and subjected to high-temperature carbonization under vacuum (0.05 kPa). The carbonization temperature was 800 °C, the carbonization holding time was 2 h, and the heating rate was 10 °C / min. After carbonization, the microspheres were cooled to room temperature under vacuum to obtain carbon microspheres.

[0120] Figure 6 This is a scanning electron microscope image of the carbon microspheres prepared in this embodiment. The image shows that the carbon microspheres exhibit a hollow, dense shell structure with a shell thickness of approximately 110 nm and a pore size of less than 2 nm. The microspheres are hollow inside and have a dense outer shell. Statistical results indicate that the average particle size of the carbon microspheres is approximately 4 μm (particle size range of 2–8 μm).

[0121] Comparative Example 1

[0122] This comparative example is used to further illustrate the advantages of the present invention. The specific comparative methods for preparing carbon microspheres are as follows:

[0123] (1) Weigh 180 g of commercially available phenolic resin and 90 g of p-hydroxybenzoic acid and add them to 180 g of ethylene glycol. Stir continuously at room temperature until the phenolic resin and p-hydroxybenzoic acid are completely dissolved to obtain a homogeneous and transparent precursor solution.

[0124] (2) Weigh 100 g of the precursor solution and add it to 2000 g of benzene silicone oil. Transfer the resulting mixture to a reaction vessel and stir continuously at a stirring speed of 400 r / min. Heat the mixture to 160 ℃ and keep it at that temperature for 25 min (stirring continuously during the heating and holding process). The appearance of large pink particles in the solution indicates that the phenolic resin has been cured.

[0125] (4) The large pink particles are filtered and separated, and the resulting solid product is collected. The solid product is washed multiple times with acetone to thoroughly remove residual benzene silicone oil.

[0126] (5) The cleaned solid product was placed in an oven at 120 °C and dried for 5 h to obtain dried phenolic resin particles.

[0127] (6) The dried phenolic resin particles were placed in a tube furnace and subjected to high-temperature carbonization under vacuum. The carbonization temperature was 800 ℃, the carbonization holding time was 2 h, and the heating rate was 10 ℃ / min. After carbonization, the particles were cooled to room temperature under vacuum to obtain carbon particles.

[0128] Figure 7 This is a scanning electron microscope image of the carbon particles prepared in this comparative example. The image shows that the carbon particles are formed by the agglomeration of a large number of hollow carbon microspheres with an average particle size of approximately 120 μm. However, the large particle size formed by such microsphere aggregation is difficult to meet the requirements for carbon material particle size in practical applications. Although ball milling can reduce the particle size, it will destroy the microsphere structure and increase costs. Compared with the preparation methods in Examples 1-6, the key difference in this comparative example is the use of a lower stirring rate and continuous stirring during the curing stage. The lower stirring rate not only leads to an increase in microsphere size but also reduces the stability of the emulsion system; while continuous stirring during the curing process promotes the agglomeration of microspheres, ultimately forming large-sized aggregated particles.

[0129] Comparative Example 2

[0130] This comparative example is used to further illustrate the advantages of the present invention. The specific comparative methods for preparing carbon microspheres are as follows:

[0131] (1) Weigh 180 g of commercially available phenolic resin and 20 g of hexamethylenetetramine, and add them to 180 g of ethylene glycol. Stir continuously at room temperature until the phenolic resin and hexamethylenetetramine are completely dissolved to obtain a homogeneous and transparent precursor solution.

[0132] (2) Weigh 100 g of precursor solution and add it to 2000 g of benzene silicone oil. At room temperature, use a high-speed emulsifier to emulsify the mixture at a speed of 6000 r / min for 20 min to obtain a stable white oil-in-alcohol emulsion.

[0133] (3) The resulting white emulsion was transferred to a reaction vessel, heated to 160 °C, and kept at this temperature for 24 h. The emulsion was observed to become clear, and yellow blocky solids were deposited at the bottom of the reaction vessel.

[0134] (4) Wash the yellow blocky solid with acetone multiple times to fully remove the residual benzene silicone oil.

[0135] (5) The cleaned solid product was placed in an oven at 120 °C and dried for 5 h to obtain dried phenolic resin blocks.

[0136] (6) The dried phenolic resin block was placed in a tube furnace and subjected to high-temperature carbonization under vacuum. The carbonization temperature was 800 ℃, the carbonization holding time was 2 h, and the heating rate was 10 ℃ / min. After carbonization, the block was cooled to room temperature under vacuum to obtain carbon.

[0137] Figure 8 This is a scanning electron microscope image of the carbon bulk material prepared in this comparative example. The image shows that the carbon bulk material did not form a microsphere structure and contained a large number of large pores. The key difference between this comparative example and the preparation methods of Examples 1-6 is the use of the alkaline catalyst hexamethylenetetramine. Because the curing rate of the alkaline catalyst is significantly lower than that of the acidic catalyst, the precursor droplets in the emulsion remained in a partially cured liquid state for an extended period during the heating stage. These liquid droplets gradually settled and continuously merged at the bottom of the container, eventually forming amorphous, large-sized resin bulk materials.

Claims

1. A method for preparing carbon microspheres, characterized in that, The method includes the following steps: (1) Preparation of precursor solution: The resin and acidic catalyst are dissolved in an alcohol solvent to obtain a precursor solution; the acidic catalyst is one or more of formic acid, acetic acid, benzoic acid, hydrochloric acid, terephthalic acid, p-toluenesulfonic acid, p-hydroxybenzoic acid and p-toluenebenzoic acid; the mass ratio of the resin to the acidic catalyst is 200:1 to 1:1; the mass ratio of the alcohol solvent to the resin is 10:1 to 1:5; (2) Emulsion preparation: The precursor solution obtained in step (1) is added to the oily continuous phase and emulsified at a stirring speed of 3000~20000 r / min for 1~30 min to prepare an emulsion; (3) Resin curing: The emulsion obtained in step (2) is heated to a temperature of 70~180℃ for 5min~1h; the resin in the emulsion is cured into resin microspheres. (4) Solid-liquid separation; (5) Drying of resin microspheres: The solid product after solid-liquid separation in step (4) is washed and dried to obtain dry resin microspheres; (6) High-temperature carbonization: The dry resin microspheres obtained in step (5) are placed in a vacuum or inert atmosphere for high-temperature carbonization to obtain carbon microsphere products.

2. The method for preparing carbon microspheres according to claim 1, characterized in that: The resin mentioned in step (1) is one or more of the following: melamine-formaldehyde resin, phosphorus-modified melamine-formaldehyde resin, boron-modified melamine-formaldehyde resin, sulfur-modified melamine-formaldehyde resin, phenolic resin, boron-modified phenolic resin, silicon-modified phenolic resin, silicon-boron-modified phenolic resin, and chitosan-modified phenolic resin. The alcohol solvent is one or more of ethylene glycol, glycerol, isopropanol and n-propanol.

3. The method for preparing carbon microspheres according to claim 1, characterized in that: The oily continuous phase in step (2) is one or more of dimethyl silicone oil, phenylmethyl silicone oil, epoxy silicone oil, and industrial white oil, and the mass ratio of the oily continuous phase to the precursor solution is 30:1 to 1:

1.

4. The method for preparing carbon microspheres according to claim 1, characterized in that: The emulsification in step (2) is carried out in a high-speed homogenizer with a stirring speed of 4000~15000 r / min and an emulsification time of 10~30 min.

5. The method for preparing carbon microspheres according to claim 1, characterized in that: The cleaning solution used in step (5) is one or more of solvent oil, benzene, xylene and kerosene; The drying temperature is 60~200℃, and the drying time is 30min~6h.

6. The method for preparing carbon microspheres according to claim 1, characterized in that: The inert atmosphere mentioned in step (6) is one or both of nitrogen and argon, and the gas flow rate is 1~10L / min; the vacuum condition is a vacuum degree ≤0.1kPa; The carbonization temperature is 500~1500℃, the carbonization heating rate is 1~10℃ / min, and the carbonization holding time is 1~10h.

7. The carbon microspheres prepared by the method according to any one of claims 1-6, characterized in that: The carbon microspheres have a particle diameter of 1-30 μm and a specific surface area of ​​300-700 m². 2 / g; By controlling the curing temperature and the ratio of resin, acidic catalyst, and alcohol solvent, a variety of different micromorphologies can be formed: When the ratio of resin to acidic catalyst is 30:1 to 10:1, the ratio of alcohol solvent to resin is 3:1 to 1:2, and the curing temperature is 70 to 140 ℃, the carbon microspheres have a shell-less aerogel structure. When the ratio of resin to acidic catalyst is 9:1 to 6:1, the ratio of alcohol solvent to resin is 3:1 to 1:2, and the curing temperature is 70 to 140 ℃, the carbon microspheres have a porous shell-coated aerogel structure. When the ratio of resin to acidic catalyst is 5:1 to 3:1, the ratio of alcohol solvent to resin is 3:1 to 1:2, and the curing temperature is 70 to 160 ℃, the carbon microspheres have a dense shell-encapsulated aerogel structure. When the ratio of resin to acidic catalyst is 2:1 to 1:1, the ratio of alcohol solvent to resin is 10:1 to 1:2, and the curing temperature is 70 to 180 ℃, the carbon microspheres have a hollow and dense shell structure. When the ratio of resin to acidic catalyst is 30:1 to 6:1, the ratio of alcohol solvent to resin is 3:1 to 1:2, and the curing temperature is 160 to 180 ℃, the carbon microspheres have an aerogel shell-hollow structure. When the ratio of resin to acidic catalyst is 200:1 to 1:1, the ratio of alcohol solvent to resin is 1:3 to 1:5, and the curing temperature is 70 to 180 ℃, the carbon microspheres have a solid structure.

8. The application of carbon microspheres as an electrode active material in supercapacitors according to claim 7, characterized in that: The electrode prepared using this carbon microsphere as the electrode active material has a specific capacitance of 200~300 F / g in 6M KOH aqueous solution.

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