Coal liquefaction pitch-based heteroatom-doped spherical capacitance carbon and preparation method thereof

Abstract

The invention belongs to the technical field of capacitor carbon preparation, and particularly relates to coal liquefaction pitch-based heteroatom-doped spherical capacitor carbon and a preparation method thereof. According to the preparation method of the coal liquefied asphalt-based heteroatom-doped spherical capacitance carbon, the coal liquefied asphalt is adopted as a raw material, so that the production cost is reduced, clean and efficient utilization of coal resources is realized, and the specific surface area, the microporosity, the electrical conductivity, the structural stability and the capacitance performance of the traditional capacitance carbon are improved; the range of production raw materials is widened, the preparation process is simplified, and pollutants are reduced.

Description

Technical Field

[0001] This invention belongs to the field of capacitor carbon preparation technology, specifically relating to a coal liquefaction pitch-based heteroatom-doped spherical capacitor carbon and its preparation method. Background Technology

[0002] With the increasing global energy demand and the growing severity of environmental problems, the development of efficient energy storage technologies has become a key research focus for countries worldwide. In recent years, electrochemical energy storage technology has seen significant development in the energy storage field. Among these, supercapacitors, with their advantages of high energy storage, long cycle life, high power density, rapid charge and discharge, and large operating current, have attracted widespread attention. Capacitor carbon materials, especially those with high specific surface area and excellent capacitance performance, have gradually become a research hotspot in supercapacitor applications. However, with the increasing demand for capacitor materials with high energy density, high power density, and long cycle life, traditional capacitor carbon materials are gradually revealing limitations such as limited specific surface area, unstable capacitance performance, and insufficient structural strength.

[0003] Currently, capacitor carbon primarily uses organic matter or natural carbon sources as raw materials, such as sugars and lignin. However, these materials are often limited by resource supply, cost, and synthesis conditions. Coal liquefaction pitch, a major solid waste generated during direct coal liquefaction, is projected to exceed 4 million tons in production by 2027. It is low-cost, widely available, structurally loose, highly reactive, and easy to process. Furthermore, it possesses aromatic rings and graphite microcrystalline structures, and boasts a high theoretical carbon yield (~90%), making it a suitable raw material for preparing high-performance capacitor carbon. Spherical capacitor carbon, due to its shorter particle spacing and high specific surface area, facilitates faster electrolyte transport and permeation. Additionally, its high sphericity contributes to high packing density, thereby improving the performance stability and structural strength of the capacitor carbon.

[0004] Template methods are considered an effective way to prepare carbon materials with precise pore structures and spherical morphologies. Materials such as SiO2 spheres, polystyrene spheres, or polypropylene spheres are often used as template agents due to their good dispersibility, environmental friendliness, and low cost. The size and shape of the template determine the final size of the spherical carbon particles. Immersing the template in a solvent allows for complete dissolution or expansion, ensuring the formation of uniform spherical shapes.

[0005] While traditional methods for preparing capacitor carbon have achieved some applications in the field of electrochemical energy storage, they still have some significant problems, mainly in the following aspects: First, the selection of carbon sources is limited. Traditional methods often use natural or synthetic organic materials as carbon sources, but these sources are limited in availability, unstable in supply, and expensive. Second, the low structural strength leads to unstable capacitor performance. Traditional capacitor carbon materials have poor structural strength and are prone to deformation or damage during rapid charging and discharging, resulting in poor cycle stability and affecting the stability and long lifespan of electrochemical energy storage devices. Third, the synthesis process is complex and costly. Traditional methods such as high-temperature carbonization and solution polymerization are relatively complex, resulting in high overall production costs and making it difficult to achieve large-scale industrial production.

[0006] Therefore, how to further optimize the preparation method of capacitor carbon has received increasing attention. Summary of the Invention

[0007] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon.

[0008] The method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to an embodiment of the present invention includes the following steps:

[0009] (1) Coal liquefaction pitch is crushed by low-temperature ball milling and then added to tetrahydrofuran and stirred to dissolve to obtain solution A;

[0010] (2) After stirring and mixing polyethylene glycol, isopropanol and deionized water, add spherical SiO2 and dispersant, mix evenly to obtain solution B;

[0011] (3) The solution A obtained in step (1) and the solution B obtained in step (2) are ultrasonically mixed and stirred, cooled to room temperature and centrifuged to obtain the substrate;

[0012] (4) The substrate obtained in step (3) is subjected to solidification and carbonization treatment in sequence to obtain a carbonized sample;

[0013] (5) Add KOH solution to the carbonized sample obtained in step (4), stir and wash to remove spherical SiO2, and then perform vacuum drying and chemical activation treatment.

[0014] The advantages and technical effects of the preparation method of coal liquefaction pitch-based heteroatom-doped spherical capacitor carbon in this invention are as follows: 1. The method of this invention uses nano-SiO2 as a template agent and KOH solution as a template eluent. KOH can also act as an activator to improve the specific surface area and microporosity of the capacitor carbon. 2. In the preparation process, a heteroatom-containing dispersant is added to form a spherical carbon precursor of suitable size, while simultaneously achieving elemental doping, effectively adjusting the electronic structure of the capacitor carbon, improving its conductivity, and thus enhancing its capacitance performance. 3. The method of this invention utilizes a solidification treatment to introduce oxygen-containing functional groups into the capacitor carbon, increasing porosity and stabilizing the spherical structure, preventing carbon sphere adhesion and melting during the carbonization process. 4. The method of this invention uses bulk coal-based solid waste—coal liquefaction pitch—as raw material, reducing production costs, achieving clean and efficient utilization of coal resources, significantly reducing the preparation cost of capacitor carbon materials, simplifying the production process, reducing pollutant generation, improving the overall performance of carbon materials, and facilitating its promotion and application in industrial production.

[0015] In some embodiments, in step (1), the softening point of the coal liquefaction pitch is 100-130°C, and the quinoline insoluble content is <0.01%.

[0016] And / or, in step (1), the particle size of the coal liquefaction pitch after the low-temperature ball milling is greater than 300 mesh, the temperature of the low-temperature ball milling is 0-5℃; the liquid-solid ratio of the tetrahydrofuran and the coal liquefaction pitch is (150-200) mL / 50g, and the temperature of stirring and dissolving is 80-120℃.

[0017] In some embodiments, in step (2), the mass ratio of polyethylene glycol, isopropanol and deionized water is (0.2-0.6):1:0.4; and the stirring temperature is 80-100°C.

[0018] In some embodiments, in step (2), the particle size of the spherical SiO2 is 200 nm to 1 μm, and the solid content of the spherical SiO2 in solution B is 30% to 50%.

[0019] And / or, in step (2), the dispersant includes at least one of H3PO3, CTAB, PVP or SDBS, and the amount of dispersant used is 10 to 20% of the mass of the template agent.

[0020] In some embodiments, in step (3), the mass ratio of solution B to solution A is (1.5 to 2.5):1;

[0021] And / or, in step (3), the temperature of the stirring treatment is 70-80°C, the stirring speed is 200-400 rpm / min, and the stirring time is 30-60 min.

[0022] In some embodiments, in step (4), the curing process is carried out in a nitrogen-oxygen mixed gas atmosphere with an oxygen content of 5-10% VOL, the flow rate of the mixed gas is 80-100 mL / min, the curing temperature is 200-350℃, the curing time is 1-3 h, and the heating rate is 1-5℃ / min.

[0023] In some embodiments, in step (4), the carbonization process is carried out under a N2 atmosphere, and the flow rate of N2 is 30-50 mL / min;

[0024] And / or, in step (4), the carbonization temperature is 500-800℃, the carbonization time is 1-3h, and the heating rate is 3-7℃ / min.

[0025] In some embodiments, in step (5), the concentration of the KOH solution is 20-25%, and the mass ratio of the carbonized sample to KOH is 1:(2-4);

[0026] And / or, in step (5), the temperature of the stirring and washing is 70-90°C, and the stirring and washing time is 4-6 hours.

[0027] In some embodiments, in step (5), the temperature of vacuum drying is 70-90°C and the time of vacuum drying is 10-15 hours;

[0028] And / or, in step (5), the chemical activation treatment is carried out in an N2 atmosphere, the flow rate of N2 is 15-45 mL / min; the temperature of the chemical activation treatment is 750-950℃, the time of the chemical activation treatment is 1-2 h, and the heating rate is 3-7℃ / min.

[0029] This invention also provides a coal liquefaction pitch-based heteroatom-doped spherical capacitor carbon, which is prepared using the method described above. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the process for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon;

[0031] Figure 2 These are the N2 adsorption-desorption curves of the spherical capacitive carbons prepared in Example 1 and Comparative Examples 1-3;

[0032] Figure 3 This is a pore size distribution diagram of the spherical capacitor carbon prepared in Example 2 and Comparative Examples 1-3;

[0033] Figure 4 These are the Raman spectra of the spherical capacitor carbons prepared in Example 3 and Comparative Examples 1-3;

[0034] Figure 5 These are the X-ray diffraction patterns of the spherical capacitor carbons prepared in Example 1 and Comparative Examples 1-3;

[0035] Figure 6 The zeta potential of the spherical capacitive carbon prepared in Example 1;

[0036] Figure 7 This is a schematic diagram of the water contact angle of the spherical capacitive carbon prepared in Example 1;

[0037] Figure 8 This is a thermogravimetric analysis curve of the spherical capacitor carbon prepared in Example 3;

[0038] Figure 9 These are scanning electron microscope images of the spherical capacitive carbons prepared in Example 1 and Comparative Examples 1-3;

[0039] Figure 10 This is the EDS elemental mapping diagram of the spherical capacitor carbon prepared in Example 2;

[0040] Figure 11 These are cyclic voltammetry curves of the electrodes prepared in Examples 4-5 and Comparative Example 4 at a scan rate of 5 mV / s;

[0041] Figure 12 These are charge-discharge curves of the electrodes prepared in Examples 4-5 and Comparative Example 4 under a condition of 5 A / g. Detailed Implementation

[0042] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0043] like Figure 1 As shown, the preparation method of coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to an embodiment of the present invention includes the following steps:

[0044] (1) Coal liquefaction pitch is crushed by low-temperature ball milling and then added to tetrahydrofuran and stirred to dissolve to obtain solution A;

[0045] (2) After stirring and mixing polyethylene glycol, isopropanol and deionized water, add spherical SiO2 and dispersant, mix evenly to obtain solution B;

[0046] (3) The solution A obtained in step (1) and the solution B obtained in step (2) are ultrasonically mixed and stirred, cooled to room temperature and centrifuged to obtain the substrate;

[0047] (4) The substrate obtained in step (3) is subjected to solidification and carbonization treatment in sequence to obtain a carbonized sample;

[0048] (5) Add KOH solution to the carbonized sample obtained in step (4), stir and wash to remove spherical SiO2, and then perform vacuum drying and chemical activation treatment.

[0049] The method for preparing heteroatom-doped spherical capacitor carbon based on coal liquefaction pitch according to embodiments of the present invention uses nano-SiO2 as a template agent and KOH solution as a template eluent. KOH can also act as an activator to increase the specific surface area and microporosity of the capacitor carbon. In the preparation process, a heteroatom-containing dispersant is added to form a spherical carbon precursor of suitable size, while simultaneously achieving elemental doping. This effectively adjusts the electronic structure of the capacitor carbon, improves its conductivity, and thus enhances its capacitance performance. The method also utilizes a curing process to introduce oxygen-containing functional groups into the capacitor carbon, increasing porosity and stabilizing the spherical structure, preventing carbon sphere adhesion and melting during carbonization. This method uses bulk coal-based solid waste—coal liquefaction pitch—as raw material, reducing production costs, achieving clean and efficient utilization of coal resources, significantly reducing the preparation cost of capacitor carbon materials, simplifying the production process, reducing pollutant generation, improving the overall performance of carbon materials, and facilitating their widespread application in industrial production.

[0050] In some embodiments, preferably, in step (1), the softening point of the coal liquefaction pitch is 100-130°C, and the quinoline insoluble content is <0.01%;

[0051] And / or, in step (1), the particle size of the coal liquefaction pitch after the low-temperature ball milling is greater than 300 mesh, the temperature of the low-temperature ball milling is 0-5℃; the liquid-solid ratio of the tetrahydrofuran and the coal liquefaction pitch is (150-200) mL / 50g, and the temperature of stirring and dissolving is 80-120℃.

[0052] In some embodiments, preferably, in step (2), the mass ratio of polyethylene glycol, isopropanol and deionized water is (0.2-0.6):1:0.4; and the stirring temperature is 80-100°C.

[0053] In some embodiments, preferably, in step (2), the particle size of the spherical SiO2 is 200 nm to 1 μm, and the solid content of the spherical SiO2 in solution B is 30% to 50%.

[0054] And / or, in step (2), the dispersant includes at least one of H3PO3, CTAB, PVP or SDBS, and the amount of dispersant used is 10 to 20% of the mass of the template agent.

[0055] In some embodiments, preferably, in step (3), the mass ratio of solution B to solution A is (1.5-2.5):1;

[0056] And / or, in step (3), the temperature of the stirring treatment is 70-80°C, the stirring speed is 200-400 rpm / min, and the stirring time is 30-60 min.

[0057] In this embodiment of the invention, stirring is performed at a temperature of 70-80°C to ensure the formation of carbon sphere precursors with uniform and suitable particle size; if the stirring temperature is too high, the sphericity is poor and the particle size is small; if the stirring temperature is too low, the particle size of the carbon sphere precursors is too large.

[0058] In some embodiments, preferably, in step (4), the curing process is carried out in a nitrogen-oxygen mixed gas atmosphere with an oxygen content of 5-10% VOL, the flow rate of the mixed gas is 80-100 mL / min, the curing temperature is 200-350℃, the curing time is 1-3 h, and the heating rate is 1-5℃ / min.

[0059] In this embodiment of the invention, the curing process is carried out at a temperature of 200-350°C to introduce oxygen-containing functional groups, increase porosity, stabilize the spherical structure, and prevent the carbon spheres from sticking together or melting during the carbonization process. If the curing temperature is too low, the curing effect will be poor, and the carbon spheres will stick together or melt during the carbonization process. If the curing temperature is too high, the spherical morphology will be destroyed.

[0060] In some embodiments, preferably, in step (4), the carbonization process is carried out under an N2 atmosphere with a flow rate of 30-50 mL / min.

[0061] And / or, in step (4), the carbonization temperature is 500-800℃, the carbonization time is 1-3h, and the heating rate is 3-7℃ / min.

[0062] In some embodiments, preferably, in step (5), the concentration of the KOH solution is 20-25%, and the mass ratio of the carbonized sample to KOH is 1:(2-4);

[0063] And / or, in step (5), the temperature of the stirring and washing is 70-90°C, and the stirring and washing time is 4-6 hours.

[0064] In some embodiments, preferably, in step (5), the vacuum drying temperature is 70-90°C and the vacuum drying time is 10-15 hours;

[0065] And / or, in step (5), the chemical activation treatment is carried out in an N2 atmosphere, the flow rate of N2 is 15-45 mL / min; the temperature of the chemical activation treatment is 750-950℃, the time of the chemical activation treatment is 1-2 h, and the heating rate is 3-7℃ / min.

[0066] In this embodiment of the invention, the carbonized sample after template removal is chemically activated at 750–950°C. It is particularly important to note that the temperature needs to be increased to the corresponding activation temperature in one step to prevent KOH decomposition. This ensures that KOH volatilizes and forms small droplets during the high-temperature process, effectively generating a large number of uniformly sized pores. This facilitates the interaction between the carbonized sample and KOH, forming a controllable, dense, and fine pore structure. If the chemical activation temperature is too low, KOH decomposes, resulting in an uneven pore structure and poor activation effect. If the activation temperature is too high, it hinders the interaction between the carbonized sample and KOH, preventing the formation of a controllable pore structure and affecting the activation effect.

[0067] This invention also provides a coal liquefaction pitch-based heteroatom-doped spherical capacitor carbon, which is prepared using the method described above.

[0068] The technical solution of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0069] Example 1

[0070] Preparation of P-doped spherical capacitive carbon:

[0071] (1) 50g of refined coal liquefaction pitch was crushed to a particle size greater than 300 mesh by low-temperature ball milling at 5℃, and 150mL of tetrahydrofuran was added and stirred at 100℃ to dissolve to obtain solution A;

[0072] (2) Polyethylene glycol, isopropanol and deionized water were added to a flask in a mass ratio of 0.4:1:0.4 and stirred at 90°C to dissolve. Then, 1 μm SiO2 was added as a template agent and H3PO3 as a dispersant. The mixture was stirred evenly to obtain solution B. The solid content of SiO2 in solution B was 35% and H3PO3 was 10% of the template agent mass.

[0073] (3) Mix solution B and solution A ultrasonically at a mass ratio of 2:1. Stir the mixture at 300 rpm / min for 30 min at 80℃. After cooling to room temperature, centrifuge to obtain the substrate.

[0074] (4) Place 10g of substrate into a high-temperature tube furnace, and in a nitrogen-oxygen mixed air atmosphere with an oxygen content of 10% VOL, the flow rate of the mixed gas is 100mL / min, and the temperature is raised to 250℃ at a heating rate of 1℃ / min for 2h to obtain coal liquefaction pitch balls containing SiO2.

[0075] (5) The SiO2-containing coal liquefaction pitch balls were placed in a high-temperature tubular furnace under N2 atmosphere with a flow rate of 30 mL / min and heated to 600℃ for 2 hours at a heating rate of 5℃ / min to obtain carbonized samples.

[0076] (6) Add a 23% KOH solution to the carbonized sample and stir and wash at 80°C for 6 hours to remove the SiO2 template (the mass ratio of carbonized sample to KOH is 1:4). After washing the carbonized sample with alkali, vacuum dry it at 80°C for 12 hours and then place it in a high-temperature tube furnace for chemical activation. The temperature is increased to 900°C at a heating rate of 5°C / min. The chemical activation is carried out in an N2 atmosphere with a N2 flow rate of 45 mL / min for 2 hours to obtain P-doped spherical capacitor carbon.

[0077] Example 2

[0078] Preparation of N-doped spherical capacitive carbon:

[0079] (1) 50g of refined coal liquefaction pitch was crushed to a particle size greater than 300 mesh by low-temperature ball milling at 5℃, and 150mL of tetrahydrofuran was added and stirred at 100℃ to dissolve to obtain solution A;

[0080] (2) Polyethylene glycol, isopropanol and deionized water were added to a flask at a mass ratio of 0.4:1:0.4 and stirred at 90°C to dissolve. Then, 500 nm SiO2 was added as a template agent and dispersant CTAB was added and mixed evenly to obtain solution B. The solid content of SiO2 in solution B was 35% and CTAB was 15% of the mass of the template agent.

[0081] (3) Mix solution B and solution A ultrasonically at a mass ratio of 2:1. Stir the mixture at 300 rpm / min for 45 min at 80℃. After cooling to room temperature, centrifuge to obtain the substrate.

[0082] (4) Place 10g of substrate into a high-temperature tube furnace and heat it to 250℃ for 3h under a nitrogen-oxygen mixed gas atmosphere with an oxygen content of 10% VOL and a mixed gas flow rate of 90mL / min at a heating rate of 2℃ / min to obtain coal liquefaction pitch balls containing SiO2.

[0083] (5) The SiO2-containing coal liquefaction pitch balls were placed in a high-temperature tubular furnace under N2 atmosphere with a flow rate of 30 mL / min and heated to 650℃ for 2 hours at a heating rate of 5℃ / min to obtain carbonized samples.

[0084] (6) Add a 23% KOH solution to the carbonized sample and stir and wash at 80°C for 5 h to remove the SiO2 template (the mass ratio of carbonized sample to KOH is 1:3). After washing the carbonized sample with alkali, vacuum dry it at 80°C for 12 h and then place it in a high-temperature tube furnace for chemical activation. The temperature is increased to 850°C at a heating rate of 5°C / min. The chemical activation is carried out in an N2 atmosphere with a N2 flow rate of 45 mL / min for 2 h to obtain N-doped spherical capacitor carbon.

[0085] Example 3

[0086] Preparation of S-doped spherical capacitive carbon:

[0087] (1) 50g of refined coal liquefaction pitch was crushed to a particle size greater than 300 mesh by low-temperature ball milling at 5℃, and 150mL of tetrahydrofuran was added and stirred at 100℃ to dissolve to obtain solution A;

[0088] (2) Polyethylene glycol, isopropanol and deionized water were added to a flask at a mass ratio of 0.2:1:0.4 and stirred at 90°C to dissolve. Then, 1 μm SiO2 was added as a template agent and SDBS as a dispersant. The mixture was stirred evenly to obtain solution B. The solid content of SiO2 in solution B was 30% and SDBS was 15% of the template agent mass.

[0089] (3) Mix solution B and solution A ultrasonically at a mass ratio of 2:1. Stir the mixture at 80°C at 300 rpm / min for 60 min. After cooling to room temperature, centrifuge to obtain the substrate.

[0090] (4) Place 10g of substrate into a high-temperature tube furnace and carry out the curing treatment at 250℃ for 3h under a nitrogen-oxygen mixed gas atmosphere with an oxygen content of 10% VOL and a mixed gas flow rate of 100mL / min, to obtain coal liquefaction pitch balls containing SiO2.

[0091] (5) The SiO2-containing coal liquefaction pitch balls were placed in a high-temperature tubular furnace under N2 atmosphere with a flow rate of 30 mL / min and heated to 550℃ for 2 hours at a heating rate of 5℃ / min to obtain carbonized samples.

[0092] (6) Add a 23% KOH solution to the carbonized sample, stir and wash at 80℃ for 5h to remove the SiO2 template (the mass ratio of carbonized sample to KOH is 1:4). After washing the carbonized sample with alkali, vacuum dry it at 80℃ for 12h and then place it in a high-temperature tube furnace for chemical activation. The temperature is increased to 950℃ at a heating rate of 5℃ / min. Activate it in N2 atmosphere at a flow rate of 45mL / min for 2h to obtain S-doped spherical capacitor carbon.

[0093] Example 4

[0094] Preparation of P-doped spherical capacitive carbon electrode:

[0095] (1) The P-doped spherical capacitive carbon prepared in Example 1 was used as the electrode material for the supercapacitor.

[0096] (2) Cut 14mm diameter nickel foam with a punching die, clean it with deionized water and ethanol by ultrasonic cleaning, and weigh each piece of nickel foam. Weigh the sample according to the mass ratio of capacitor carbon: conductive carbon black: polytetrafluoroethylene dispersion = 8:1:1, add an appropriate amount of ethanol, and grind repeatedly for 30 minutes until a viscous mud-like sample is formed. Coat the sample evenly on the nickel foam, cover it with another piece of nickel foam and compact it, vacuum dry at 80℃ for 12 hours, press it with 5MPa pressure for 5 minutes, and weigh the prepared electrode.

[0097] (3) The prepared electrode is the working electrode, the Pt electrode is the counter electrode, the Hg / HgO electrode (1mol / L KOH) is the reference electrode, and the 6mol / L KOH is the electrolyte. The capacitance performance is tested.

[0098] Example 5

[0099] Fabrication of N-doped spherical capacitive carbon electrode:

[0100] The steps are the same as in Example 4, but the spherical capacitor carbon used was prepared in Example 2.

[0101] Comparative Example 1

[0102] Preparation of spherical capacitor carbon:

[0103] (1) 50g of refined coal liquefaction pitch was crushed to a particle size greater than 300 mesh by low-temperature ball milling at 5℃, and 150mL of tetrahydrofuran was added and stirred at 100℃ to dissolve to obtain solution A;

[0104] (2) Polyethylene glycol, isopropanol and deionized water were added to a flask in a mass ratio of 0.4:1:0.4 and stirred at 90°C to dissolve. Then, 1 μm SiO2 was added as a template agent and mixed evenly to obtain solution B. The solid content of SiO2 in solution B was 35%.

[0105] (3) Mix solution B and solution A ultrasonically at a mass ratio of 2:1. Stir the mixture at 300 rpm / min for 30 min at 80℃. After cooling to room temperature, centrifuge to obtain the substrate.

[0106] (4) Place 10g of substrate into a high-temperature tube furnace and heat it to 250℃ for 2h at a heating rate of 1℃ / min under a nitrogen-oxygen mixed gas atmosphere with an oxygen content of 10% VOL, and a mixed gas flow rate of 100mL / min to obtain SiO2-containing coal liquefaction pitch balls.

[0107] (5) The SiO2-containing coal liquefaction pitch balls were placed in a high-temperature tubular furnace under N2 atmosphere with a flow rate of 30 mL / min and heated to 600℃ for 2 hours at a heating rate of 5℃ / min to obtain carbonized samples.

[0108] (6) Add a 23% KOH solution to the carbonized sample and stir and wash at 80°C for 6 hours to remove the SiO2 template (the mass ratio of carbonized sample to KOH is 1:4). After washing the carbonized sample with alkali, vacuum dry it at 80°C for 12 hours and then place it in a high-temperature tube furnace for chemical activation. The temperature is increased to 900°C at a heating rate of 5°C / min. The chemical activation is carried out in an N2 atmosphere with a N2 flow rate of 45 mL / min for 2 hours to obtain spherical capacitor carbon.

[0109] Comparative Example 2

[0110] Preparation of spherical capacitor carbon:

[0111] (1) 50g of refined coal liquefaction pitch was crushed to a particle size greater than 300 mesh by low-temperature ball milling at 5℃, and 150mL of tetrahydrofuran was added and stirred at 100℃ to dissolve to obtain solution A;

[0112] (2) Polyethylene glycol, isopropanol and deionized water were added to a flask in a mass ratio of 0.4:1:0.4 and stirred at 90°C to dissolve. Then, 1 μm SiO2 was added as a template agent and H3PO3 as a dispersant. The mixture was stirred evenly to obtain solution B. The solid content of SiO2 in solution B was 35% and H3PO3 was 10% of the template agent mass.

[0113] (3) Mix solution B and solution A ultrasonically at a mass ratio of 2:1. Stir the mixture at 300 rpm / min for 30 min at 80℃. After cooling to room temperature, centrifuge to obtain the substrate and dry it.

[0114] (4) The dried substrate was placed in a high-temperature tube furnace under N2 atmosphere with a flow rate of 30 mL / min and heated to 600℃ for 2 hours at a heating rate of 5℃ / min to obtain a carbonized sample.

[0115] (5) Add a 23% KOH solution to the carbonized sample and stir and wash at 80°C for 6 hours to remove the SiO2 template (the mass ratio of carbonized sample to KOH is 1:4). After washing the carbonized sample with alkali, vacuum dry it at 80°C for 12 hours and then place it in a high-temperature tube furnace for chemical activation. The temperature is increased to 900°C at a heating rate of 5°C / min. The chemical activation is carried out in an N2 atmosphere with a N2 flow rate of 45 mL / min for 2 hours to obtain P-doped spherical capacitor carbon.

[0116] Comparative Example 3

[0117] Preparation of spherical capacitor carbon:

[0118] (1) 50g of refined coal liquefaction pitch was crushed to a particle size greater than 300 mesh by low-temperature ball milling at 5℃, and 150mL of tetrahydrofuran was added and stirred at 100℃ to dissolve it to obtain solution A;

[0119] (2) Polyethylene glycol, isopropanol and deionized water were added to a flask in a mass ratio of 0.4:1:0.4 and stirred at 90°C to dissolve. Then, 1 μm SiO2 was added as a template agent and H3PO3 as a dispersant. The mixture was stirred evenly to obtain solution B. The solid content of SiO2 in solution B was 35%, and H3PO3 was 10% of the mass of the template agent.

[0120] (3) Mix solution B and solution A ultrasonically at a mass ratio of 2:1. Stir the mixture at 300 rpm / min for 30 min at 80℃. After cooling to room temperature, centrifuge to obtain the substrate.

[0121] (4) Place 10g of substrate into a high-temperature tube furnace and heat it to 250℃ for 2h at a heating rate of 1℃ / min under a nitrogen-oxygen mixed gas atmosphere with an oxygen content of 10% VOL, and a mixed gas flow rate of 100mL / min to obtain SiO2-containing coal liquefaction pitch balls.

[0122] (5) The SiO2-containing coal liquefaction pitch balls were placed in a high-temperature tubular furnace under N2 atmosphere with a flow rate of 30 mL / min and heated to 600℃ for 2 hours at a heating rate of 5℃ / min to obtain carbonized samples.

[0123] (6) Add an appropriate amount of dilute HF solution to the carbonized sample and stir and wash for 2 hours. Wash it clean with ethanol and deionized water. After vacuum drying at 80℃ for 12 hours, place it in a high-temperature tube furnace for steam activation treatment. Heat the sample to 1000℃ at a heating rate of 5℃ / min for 2 hours. The steam activation treatment is a mixed atmosphere of N2 and water vapor, with an N2 flow rate of 45mL / min and a water vapor flow rate of 5mL / h, to obtain P-doped spherical capacitor carbon.

[0124] Comparative Example 4

[0125] Preparation of spherical capacitor carbon electrode:

[0126] (1) The spherical capacitive carbon prepared in Comparative Example 1 was used as a supercapacitor material.

[0127] (2) Cut 14mm diameter nickel foam with a punching die, clean it with deionized water and ethanol by ultrasonic cleaning, and weigh each piece of nickel foam. Weigh the sample according to the mass ratio of capacitor carbon: conductive carbon black: polytetrafluoroethylene dispersion = 8:1:1, add an appropriate amount of ethanol, and grind repeatedly for 30 minutes until a viscous mud-like sample is formed. Coat the sample evenly on the nickel foam, cover it with another piece of nickel foam and compact it, vacuum dry at 80℃ for 12 hours, press it with 5MPa pressure for 5 minutes, and weigh the prepared electrode.

[0128] (3) The prepared electrode is the working electrode, the Pt electrode is the counter electrode, the Hg / HgO electrode (1mol / L KOH) is the reference electrode, and 6mol / L KOH is the electrolyte. The capacitance performance of the comparative sample 1 is tested.

[0129] The spherical capacitor carbons prepared in Examples 1-3 and Comparative Examples 1-3 were characterized, and the results are shown in Table 1.

[0130] Table 1

[0131]

[0132] As can be seen from the table above, the specific surface area of ​​all spherical capacitive carbon samples prepared by the template method in Examples 1-3 is greater than 1800 m². 2 / g. The specific surface area of ​​Comparative Example 1 is 1380.4 m². 2 The reason for the low specific surface area ( / g) in Comparative Example 1 is that no dispersant was added during the preparation process, resulting in excessively large and poorly spherical SiO2-containing coal liquefaction pitch spheres. This led to unsatisfactory subsequent carbonization and activation effects, with an average pore size of 8.24 nm. Furthermore, since no doping source was introduced, Comparative Example 1 did not undergo heteroatom doping, resulting in poor conductivity and an increased resistivity of 1.76 Ω·cm. Comparative Example 2 had a specific surface area of ​​1242.2 m². 2 / The average pore size was 8.79 nm, mainly due to the lack of a solidification treatment, which led to instability in the prepared spherical structure and subsequent adhesion and melting during carbonization. Comparative Example 3 had a specific surface area of ​​1566.7 m². 2 / g, the sample yield was 43%, mainly because the template was not eluted with alkali and chemically activated, resulting in a low specific surface area and sample yield.

[0133] from Figure 2 As can be seen, the adsorption-desorption curves of the samples prepared in Example 1 and Comparative Examples 1-3 belong to Type I isotherms. The adsorption capacity increases rapidly at lower relative pressures, and saturation occurs after reaching a certain relative pressure. This indicates that the capacitive carbon is predominantly microporous. Furthermore, the capacitive carbon prepared in Example 1 has a higher adsorption volume because it has a higher specific surface area (1864.1 m²). 2 The specific surface area of ​​the samples prepared in the comparative examples ( / g) was higher than that of the samples prepared in the comparative examples 1 to 3. The microporosity of all the comparative examples was low. Microporosity is the key to improving capacitance performance, so the capacitance performance of the comparative examples was poor.

[0134] from Figure 3 As can be seen, the pore size of the sample prepared in Example 2 is significantly smaller, with an average pore size of 1.79 nm, which is lower than that of the samples in Comparative Examples 1-3. Figure 2 and Figure 3The results show that the dispersant, pre-oxidation insoluble treatment, and KOH washing treatment all improve the specific surface area and pore structure of the sample.

[0135] from Figure 4 As can be seen from the data, the samples obtained in Example 3 and Comparative Examples 1-3 all had a cross-sectional area of ​​1350 cm⁻¹. -1 and 1590cm -1 There are two typical carbon characteristic peaks nearby, corresponding to the D peak of the defect structure and the G peak of the ordered structure of carbon materials, respectively. I is calculated based on the fitted peak area ratio of D and G in the spectrum. D / I G The value represents the degree of ordered graphitization. Example 3 sample I... D / I G A value of 0.96 indicates that the sample has the highest degree of graphitization.

[0136] from Figure 5 As can be seen from the data, the spherical capacitor carbons prepared in Example 1 and Comparative Examples 1-3 have obvious (002) and (100) diffraction peaks, indicating that the samples are all amorphous materials.

[0137] from Figure 6 As can be seen, the sample prepared in Example 1 exhibits a Zeta potential of 31.4 mV, which meets the application requirements of good dispersibility of spherical capacitor carbon.

[0138] from Figure 7 As can be seen, the sample prepared in Example 2 showed a water contact angle of 46.5°, indicating good hydrophilicity.

[0139] from Figure 8 As can be seen from the data, the thermal decomposition temperature of the samples prepared in Example 3 is all >800℃, indicating very strong thermal stability.

[0140] from Figure 9 As can be seen, the sample prepared in Example 1 has a spherical morphology with a particle size of 0.5 to 1 μm. The sample prepared in Comparative Example 1 has poor carbon sphere formation because no dispersant was added. The sample prepared in Comparative Example 2 has a melting and coalescence phenomenon during carbonization because no solidification treatment was performed. The sample prepared in Comparative Example 3 was activated with steam, and the sample produced a certain amount of mesoporous structure with a relatively large average pore size and a low microporosity.

[0141] from Figure 10 This is an EDS elemental mapping diagram of the N-doped spherical capacitor carbon prepared in Example 2, which contains elements such as C, N, and O, indicating that nitrogen has been successfully incorporated into the material.

[0142] from Figure 11 and 12As can be seen, the specific capacitance of the electrodes prepared in Examples 4 and 5 reached 151.2 and 164.0 F / g, respectively, which is significantly better than that of the electrode prepared in Comparative Example 4 (122.8 F / g). This indicates that the doping of P or N elements can improve the conductivity of the sample and give the electrode higher capacitance performance.

[0143] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0144] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon, characterized in that, Includes the following steps: (1) Coal liquefaction pitch is crushed by low-temperature ball milling and then added to tetrahydrofuran and stirred to dissolve to obtain solution A; (2) After stirring and mixing polyethylene glycol, isopropanol and deionized water, add spherical SiO2 and dispersant, mix evenly to obtain solution B; (3) The solution A obtained in step (1) and the solution B obtained in step (2) are ultrasonically mixed and stirred, cooled to room temperature and centrifuged to obtain the substrate; (4) The substrate obtained in step (3) is subjected to solidification and carbonization treatment in sequence to obtain a carbonized sample; (5) Add KOH solution to the carbonized sample obtained in step (4), stir and wash to remove spherical SiO2, and then perform vacuum drying and chemical activation treatment.

2. The method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to claim 1, characterized in that, In step (1), the softening point of the coal liquefaction pitch is 100-130℃, and the quinoline insoluble content is <0.01%. And / or, in step (1), the particle size of the coal liquefaction pitch after the low-temperature ball milling is greater than 300 mesh, the temperature of the low-temperature ball milling is 0-5℃; the liquid-solid ratio of the tetrahydrofuran and the coal liquefaction pitch is (150-200) mL / 50g, and the temperature of stirring and dissolving is 80-120℃.

3. The method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to claim 1, characterized in that, In step (2), the mass ratio of polyethylene glycol, isopropanol and deionized water is (0.2-0.6):1:0.4; the mixing temperature is 80-100℃.

4. The method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to claim 1 or 3, characterized in that, In step (2), the particle size of the spherical SiO2 is 200 nm to 1 μm, and the solid content of the spherical SiO2 in solution B is 30% to 50%. And / or, in step (2), the dispersant includes at least one of H3PO3, CTAB, PVP or SDBS, and the amount of dispersant used is 10 to 20% of the mass of the template agent.

5. The method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to claim 1, characterized in that, In step (3), the mass ratio of solution B to solution A is (1.5~2.5):1; And / or, in step (3), the temperature of the stirring treatment is 70-80°C, the stirring speed is 200-400 rpm / min, and the stirring time is 30-60 min.

6. The method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to claim 1, characterized in that, In step (4), the curing process is carried out in a nitrogen-oxygen mixed gas atmosphere with an oxygen content of 5-10% VOL, the flow rate of the mixed gas is 80-100 mL / min, the curing temperature is 200-350℃, the curing time is 1-3 h, and the heating rate is 1-5℃ / min.

7. The method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to claim 1, characterized in that, In step (4), the carbonization process is carried out under a N2 atmosphere with a flow rate of 30-50 mL / min. And / or, in step (4), the carbonization temperature is 500-800℃, the carbonization time is 1-3h, and the heating rate is 3-7℃ / min.

8. The method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to claim 1, characterized in that, In step (5), the concentration of the KOH solution is 20-25%, and the mass ratio of the carbonized sample to KOH is 1:(2-4). And / or, in step (5), the temperature of the stirring and washing is 70-90°C, and the stirring and washing time is 4-6 hours.

9. The method for preparing coal liquefaction pitch-based heteroatom-doped spherical capacitive carbon according to claim 1, characterized in that, In step (5), the temperature of vacuum drying is 70-90°C and the time of vacuum drying is 10-15 hours. And / or, in step (5), the chemical activation treatment is carried out in an N2 atmosphere, the flow rate of N2 is 15-45 mL / min; the temperature of the chemical activation treatment is 750-950℃, the time of the chemical activation treatment is 1-2 h, and the heating rate is 3-7℃ / min.

10. A coal liquefaction pitch-based heteroatom-doped spherical capacitor carbon, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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