A method for preparing coal tar pitch-based porous carbon for electric double-layer capacitors

Abstract

A method for preparing coal tar pitch-based porous carbon for double-layer capacitors belongs to the field of new energy material preparation technology. The preparation method includes the following steps: thoroughly mixing coal tar pitch and phenolic resin powder, and pre-carbonizing under inert gas protection to obtain a pre-carbonized product; grinding and mixing the obtained pre-carbonized product with potassium hydroxide, and then subjecting it to high-temperature carbonization and activation under inert gas protection, followed by post-treatment to obtain coal tar pitch-based porous carbon. This invention uses coal tar pitch as a carbon source and phenolic resin as an additional carbon source and template to prepare a soft and hard carbon composite material, effectively controlling the specific surface area and pore distribution of the obtained porous carbon material, with a specific surface area of ​​1663.68~2606.56 m². 2 .g ‑1 The mesoporosity ranges from 32.52% to 63.58%. When used as an electrode material for electric double-layer capacitors, it achieves a maximum specific capacitance of 324.6 F / g. ‑1 @1 A g ‑1 It has high specific capacitance, low charge transfer resistance and excellent cycling and rate performance.

Description

Technical Field

[0001] This invention relates to a method for preparing coal tar pitch-based porous carbon for use in electric double-layer capacitors, belonging to the field of new energy material preparation technology. Background Technology

[0002] Supercapacitors, as a novel charge storage device combining the advantages of ordinary capacitors and batteries, possess characteristics such as long cycle stability, fast charge and discharge rates, high energy conversion efficiency, and a wide operating temperature range. Supercapacitors include electric double-layer capacitors, pseudocapacitors, and hybrid capacitors. Electric double-layer capacitors consist of two porous carbon electrodes with high surface areas. Ions from the electrolyte are adsorbed onto the electrode surface, and the number of oppositely charged ions accumulating on the electrode surface is proportional to the applied voltage, forming the so-called "electric double layer." The charge storage mechanism of a pure electric double-layer capacitor is a non-Radida reaction, meaning that no charge or mass transfer loss occurs at the electrode-electrolyte interface during charging and discharging; energy storage is purely electrostatic. Therefore, it does not harm the integrity and stability of the electrodes and exhibits better cycle performance.

[0003] Porous carbon possesses advantages such as low cost, large specific surface area, good chemical stability, and high electrical conductivity, and is considered the most promising electrode material for double-layer capacitors. Currently, porous carbon materials used in supercapacitors are mainly prepared through the synthesis of organic polymers, fossil fuels, and biomass, with the raw materials for synthesizing organic polymers also derived from non-renewable resources such as fossil fuels. Coal tar pitch, a byproduct of the coal chemical industry, is a heavy residue after the distillation of coal tar, accounting for more than 55% of its mass. It has advantages such as high carbon content, low ash content, stable source, and good thermoplasticity, and is widely available and inexpensive, making it suitable as a precursor for the commercial and industrial preparation of various functional carbon materials. To improve the performance of supercapacitors, extensive optimization studies have been conducted on the physicochemical properties of porous carbon electrodes, such as specific surface area and pore structure. Layered porous carbon with micropores / mesopores / macropores is an ideal electrode material for supercapacitors, where micropores provide active surfaces for charge storage, mesopores serve as ion transfer channels, and macropores act as electrolyte reservoirs. Therefore, how to effectively control the specific surface area and pore structure of porous carbon is an urgent problem to be solved in order to make it an excellent electrode material for double-layer capacitors. Summary of the Invention

[0004] To obtain high-performance electrode materials for electric double-layer capacitors, the present invention aims to provide a method for preparing coal tar pitch-based porous carbon for supercapacitors. This preparation method is simple, low-cost, and requires minimal equipment. The prepared material, when used as an electrode sheet for electric double-layer capacitors, exhibits high specific capacitance and good rate performance.

[0005] To achieve the aforementioned objectives and address the problems existing in the prior art, the technical solution adopted by this invention is: a method for preparing coal tar pitch-based porous carbon for supercapacitors, comprising the following steps:

[0006] (1) Mix 200-300 mesh coal tar powder and 200-300 mesh phenolic resin powder to obtain a mixture, with a mass ratio of coal tar powder to phenolic resin powder of (2-5):1;

[0007] (2) Take the mixture and pre-carbonize it in a tube furnace under an argon atmosphere at 300℃-400℃ for 1-3 hours to obtain the pre-carbonized product;

[0008] (3) Grind and mix the pre-carbonized product and potassium hydroxide evenly, and then perform high-temperature carbonization and activation under argon protection, raising the temperature from room temperature to 800°C. o C-900 o C, keep at a constant temperature for 1-3 hours, then cool to room temperature to obtain the carbonized and activated product;

[0009] The mass ratio of the pre-carbonized product to potassium hydroxide is 1:(1~5).

[0010] (4) The carbonization activation product solution was acidified to neutral in deionized water; after washing, centrifugation and drying, pitch-based porous carbon was obtained.

[0011] The mixing method of coal tar pitch powder and phenolic resin powder is as follows: coal tar pitch powder and phenolic resin powder are added to an organic solvent and ultrasonically treated.

[0012] The mixing method for coal tar pitch powder and phenolic resin powder is as follows: Place the coal tar pitch powder and phenolic resin powder in the grinding jar of a planetary ball mill, and mix at 350-550 rpm. -1 Ball milling at high speed.

[0013] The pitch-based porous carbon is used as an electrode material for electric double-layer capacitors.

[0014] Furthermore, the preparation method specifically includes the following steps:

[0015] Step 1: Grind the high softening point asphalt from Meishan Steel and sieve it through a 200-mesh screen. Preliminarily pulverize the thermosetting phenolic resin at 1000 r / min. -1 Ball milling for 2 hours yielded 300-mesh phenolic resin powder. Coal tar pitch and phenolic resin powder were mixed at a 3:1 ratio using various methods, including dissolving the pitch with N,N-dimethylformamide (DMF) and ultrasonic dispersion at 350 rpm. -1 and 550 r min -1The mixture was ball-milled for 12 h using a planetary ball mill. 2 g of the resulting mixture was then pre-carbonized in a tube furnace under argon atmosphere at 300 °C for 2 h, with a heating rate of 5 °C / min. -1 .

[0016] Step 2: Thoroughly grind and mix the pre-carbonized product obtained in Step 1 with potassium hydroxide, and then perform high-temperature carbonization and activation under argon protection, starting from room temperature and increasing by 5°C. o C min -1 The heating rate increased to 850 o C, keep at a constant temperature for 2 h, cool to room temperature to obtain the product, wherein the mass ratio of the pre-carbonized product to potassium hydroxide is 1:1~6.

[0017] Step 3: Dissolve the carbonized activated product obtained in Step 2 in 40 ml of deionized water, and incubate at 5000 rpm. -1 After centrifugation, the material is dissolved again and a small amount of diluted hydrochloric acid is added until neutral. After washing with deionized water and centrifugation 2-3 times, the precipitate is dried in an oven at 80 ℃ to obtain coal tar pitch-based porous carbon.

[0018] The coal tar pitch-based porous carbon prepared by the above method is used as an electrode material for electric double-layer capacitors.

[0019] Compared with existing technologies, the present invention has the following advantages:

[0020] (1) Amorphous porous carbon with short-range ordered structures derived from hard carbon, such as phenolic resin, has a large specific surface area, which helps to provide high capacitance and thus high energy density of devices. Graphite carbon materials with long-range ordered structures derived from soft carbon, such as coal tar pitch, can meet the requirements of high conductivity and further lead to good power density. This invention combines the excellent properties of the above two carbon materials to prepare a soft and hard carbon composite material with coal tar pitch and phenolic resin as carbon sources. As an electrode material for electric double-layer capacitors, it has high specific capacitance, low charge transfer resistance, and excellent cycling and rate performance.

[0021] (2) Traditional template methods require additional template removal, which increases costs and causes pollution. This invention uses thermosetting phenolic resin that decomposes into carbon at high temperatures as a carbon source and template, avoiding the use of additional acid or alkali to remove the template, reducing costs and pollution, and effectively controlling the specific surface area and pore distribution of the obtained porous carbon material.

[0022] (3) The preparation method is simple to operate and low in cost. It can provide high-performance double-layer capacitor electrode materials and realize the efficient, clean and high-value-added utilization of coal tar by-products, namely coal pitch and waste thermosetting phenolic resin. Attached Figure Description

[0023] Figure 1 The coal tar pitch-based porous carbon prepared in Examples 2, 4, 5 and 6 is in 1A g -1 Constant current charge-discharge diagram under current density.

[0024] Figure 2 These are electrochemical impedance spectroscopy diagrams of the coal tar pitch-based porous carbon prepared in Examples 2, 4, 5, and 6.

[0025] Figure 3 The graphs show the constant current charge-discharge diagrams of the coal tar pitch-based porous carbon prepared in Example 6 at different current densities.

[0026] Figure 4 This is a specific capacity diagram of the coal tar pitch-based porous carbon prepared in Example 6, calculated at different current densities. Detailed Implementation

[0027] The present invention will be further described below with reference to the embodiments.

[0028] A method for preparing coal tar pitch-based porous carbon for double-layer capacitors, comprising the following steps: 1. Thoroughly mixing coal tar pitch and phenolic resin powder, and pre-carbonizing under inert gas protection to obtain a pre-carbonized product; 2. Grinding and mixing the obtained pre-carbonized product with potassium hydroxide, and then performing high-temperature carbonization and activation treatment under inert gas protection to obtain a product; 3. Acid washing, water washing, centrifugation, and drying of the obtained product to obtain coal tar pitch-based porous carbon.

[0029] Furthermore, a method for preparing coal tar pitch-based porous carbon for supercapacitors includes the following steps:

[0030] (1) Mix 200-300 mesh coal tar powder and 200-300 mesh phenolic resin powder to obtain a mixture, with a mass ratio of coal tar powder to phenolic resin powder of (2-5):1;

[0031] (2) Take the mixture and pre-carbonize it in a tube furnace under an argon atmosphere at 300℃-400℃ for 1-3 hours to obtain the pre-carbonized product;

[0032] (3) Grind and mix the pre-carbonized product and potassium hydroxide evenly, and then perform high-temperature carbonization and activation under argon protection, raising the temperature from room temperature to 800°C. o C-900 o C, keep at a constant temperature for 1-3 hours, then cool to room temperature to obtain the carbonized and activated product;

[0033] The mass ratio of the pre-carbonized product to potassium hydroxide is 1:(1~6).

[0034] (4) The carbonization activation product solution was acidified to neutral in deionized water; after washing, centrifugation and drying, pitch-based porous carbon was obtained.

[0035] The mixing method of coal tar pitch powder and phenolic resin powder is as follows: coal tar pitch powder and phenolic resin powder are added to an organic solvent and ultrasonically treated.

[0036] The mixing method for coal tar pitch powder and phenolic resin powder is as follows: Place the coal tar pitch powder and phenolic resin powder in the grinding jar of a planetary ball mill, and mix at 350-550 rpm. -1 Ball milling at high speed. Example 1

[0037] High softening point pitch from Meishan Steel was ground and sieved through a 200-mesh sieve. 2 g of coal tar pitch powder was pre-carbonized in a tube furnace under argon atmosphere at 300 °C for 2 h, with a heating rate of 5 °C / min. -1 The obtained pre-carbonized product and potassium hydroxide were thoroughly ground and mixed evenly, and then subjected to high-temperature carbonization and activation under argon protection, with the temperature increasing from room temperature in increments of 5 °C / min. -1 The heating rate increased to 850 o C, kept at a constant temperature for 2 h, then cooled to room temperature to obtain the product. The mass ratio of the pre-carbonized product to potassium hydroxide was 1:1. The obtained carbonized activated product was dissolved in 40 ml of deionized water and incubated at 5000 r / min. -1 After centrifugation, the material is dissolved again and a small amount of diluted hydrochloric acid is added until neutral. After washing with deionized water and centrifugation 2-3 times, the precipitate is dried in an oven at 80°C to obtain coal tar pitch-based porous carbon.

[0038] Take 10 mg of the above-mentioned coal tar pitch-based porous carbon, and mix it with carbon black and 0.6 wt% polytetrafluoroethylene solution in anhydrous ethanol at a mass ratio of 8:1:1. Sonicate the mixture for 20 min to disperse and mix it evenly. Dry it in an oven at 80 ℃, place it on a smooth titanium sheet, and repeatedly roll it to bind it into a block shape. Press it into a uniform thin sheet using a roller press, and then use a punch to make a 10 mm disc. Use 16 mm nickel foam as the current collector, and press the sheet at 12 MPa for 10 s to ensure full contact between the electrode material and the nickel foam, thus preparing a supercapacitor electrode sheet. Use 50 mL of 6 mol / L potassium hydroxide aqueous solution as the electrolyte, a platinum sheet as the counter electrode, and Hg / HgO as the reference electrode for electrochemical performance testing. The material exhibits typical double-layer capacitance characteristics, with a capacitance of 1 A g. -1 The specific capacitance at the current density is 162.0 F g. -1 . Example 2

[0039] High softening point pitch from Meishan Steel was ground and sieved through a 200-mesh sieve. 2 g of coal tar pitch powder was pre-carbonized in a tube furnace under argon atmosphere at 300 °C for 2 h, with a heating rate of 5 °C / min.-1 The obtained pre-carbonized product and potassium hydroxide were thoroughly ground and mixed evenly, and then subjected to high-temperature carbonization and activation under argon protection, with the temperature increasing from room temperature in increments of 5°C / min. -1 The heating rate increased to 850 o C, kept at a constant temperature for 2 h, then cooled to room temperature to obtain the product. The mass ratio of the pre-carbonized product to potassium hydroxide was 1:3. The obtained carbonized activated product was dissolved in 40 ml of deionized water and incubated at 5000 r / min. -1 After centrifugation, the material was dissolved twice and diluted with a small amount of hydrochloric acid until neutral. After 2-3 washes with deionized water and centrifugation, the precipitate was dried in an oven at 80 °C to obtain coal tar pitch-based porous carbon (denoted as SC). The obtained pitch-based porous carbon has a density of 2,282.25 μm. 2 .g -1 It has a high specific surface area and a mesoporosity of 46.84%. Figure 1 The GCD curves in the figure show that the coal tar pitch-based porous carbon obtained in Example 2 has typical double-layer capacitance characteristics and a high specific capacitance at 1 A g. -1 The specific capacitance reaches 268.3 F g at the given current density. -1 , Figure 2 The electrochemical impedance spectroscopy indicates that the material has low charge transfer resistance and ion migration resistance. Example 3

[0040] High softening point pitch from Meishan Steel was ground and sieved through a 200-mesh sieve. 2 g of coal tar pitch powder was pre-carbonized in a tube furnace under argon atmosphere at 300 °C for 2 h, with a heating rate of 5 °C / min. -1 The obtained pre-carbonized product and potassium hydroxide were thoroughly ground and mixed evenly, and then subjected to high-temperature carbonization and activation under argon protection, with the temperature increasing from room temperature in increments of 5 °C / min. -1 The heating rate increased to 850 o C, kept at a constant temperature for 2 h, then cooled to room temperature to obtain the product. The mass ratio of the pre-carbonized product to potassium hydroxide was 1:5. The obtained carbonized activated product was dissolved in 40 ml of deionized water and incubated at 5000 r / min. -1 After centrifugation, the material was dissolved again and diluted with a small amount of hydrochloric acid until neutral. After 2-3 washes with deionized water and centrifugation, the precipitate was dried in an oven at 80 °C to obtain coal tar pitch-based porous carbon. The material exhibits typical double-layer capacitance characteristics, with a capacitance of 1 A g. -1 The specific capacitance at the current density is 213.0 F g. -1 . Example 4

[0041] High softening point asphalt from Meishan Steel was ground and sieved through a 200-mesh sieve. Thermosetting phenolic resin was initially pulverized and then subjected to a 1000 rpm process.-1 Ball milling for 2 hours yielded 300-mesh phenolic resin powder. 1.5 g of coal tar pitch was dissolved in 20 ml of DMF, and 0.5 g of the 300-mesh phenolic resin powder was mixed in and ultrasonically treated for 1 hour, then dried in an oven at 70 °C. 2 g of the resulting mixture was pre-carbonized in an argon-atmosphere tube furnace at 300 °C for 2 hours, with a heating rate of 5 °C / min. -1 The obtained pre-carbonized product and potassium hydroxide were thoroughly ground and mixed evenly, and then subjected to high-temperature carbonization and activation under argon protection, with the temperature decreasing from room temperature in increments of 5 °C / min. -1 The heating rate increased to 850 o C, kept at a constant temperature for 2 h, then cooled to room temperature to obtain the product. The mass ratio of the pre-carbonized product to potassium hydroxide was 1:3. The obtained carbonized activated product was dissolved in 40 ml of deionized water and incubated at 5000 rpm. -1 After centrifugation, the material was dissolved again and a small amount of diluted hydrochloric acid was added dropwise until neutral. After washing with deionized water and centrifuging 2-3 times, the precipitate was dried in an oven at 80 ℃ to obtain coal tar pitch-based porous carbon (SHC). -DMF The obtained porous carbon has a specific surface area of ​​1,663.68 m². 2 .g -1 The mesoporosity is 32.52%. Figure 1 The constant current charge-discharge curves show the coal tar pitch-based porous carbon obtained in Example 4 at 1 A g. -1 It has 239.4 F g at a current density. -1 Specific capacitance, Figure 2 The electrochemical impedance spectroscopy results show that the charge transfer resistance is also higher than that of Example 2. Example 5

[0042] High softening point asphalt from Meishan Steel was ground and sieved through a 200-mesh sieve. Thermosetting phenolic resin was initially pulverized and then subjected to a 1000 rpm process. -1 Ball milling for 2 hours yielded 300-mesh phenolic resin powder. Coal tar pitch and phenolic resin powder were mixed at a 3:1 mass ratio and placed in the grinding jar of a planetary ball mill. The mixture was then milled at 350 r / min. -1 The mixture was ball-milled at a rotation speed of 12 h. 2 g of the resulting mixture was then pre-carbonized in a tube furnace under argon atmosphere at 300 °C for 2 h, with a heating rate of 5 °C / min. -1 The obtained pre-carbonized product and potassium hydroxide were thoroughly ground and mixed evenly, and then subjected to high-temperature carbonization and activation under argon protection, with the temperature decreasing from room temperature in increments of 5 °C / min. -1 The heating rate increased to 850 oC, kept at a constant temperature for 2 h, then cooled to room temperature to obtain the product. The mass ratio of the pre-carbonized product to potassium hydroxide was 1:3. The obtained carbonized activated product was dissolved in 40 ml of deionized water and heated at 5000 r / min. -1 After centrifugation, the material was dissolved again and a small amount of diluted hydrochloric acid was added dropwise until neutral. After washing with deionized water and centrifuging 2-3 times, the precipitate was dried in an oven at 80 ℃ to obtain coal tar pitch-based porous carbon (SHC). -350 r min -1 The obtained porous carbon has a specific surface area of ​​2,494.65 m². 2 .g -1 The mesoporosity was 51.07%, which is higher than that of Example 2, both in terms of specific surface area and mesoporosity. Figure 1 The constant current charge-discharge curves show that the specific capacitance of the coal tar pitch-based porous carbon obtained in Example 5 is 292.6 F / g. -1 , Figure 2 The electrochemical impedance spectroscopy results show that the charge transfer resistance is smaller compared to Example 2. Example 6

[0043] High softening point asphalt from Meishan Steel was ground and sieved through a 200-mesh sieve. Thermosetting phenolic resin was initially pulverized and then subjected to a 1000 rpm process. -1 Ball milling for 2 hours yielded 300-mesh phenolic resin powder. Coal tar pitch and phenolic resin powder were mixed at a 3:1 mass ratio and placed in the grinding jar of a planetary ball mill, then milled at 550 r / min. -1 The mixture was ball-milled at a rotation speed of 12 h. 2 g of the resulting mixture was then pre-carbonized in a tube furnace under argon atmosphere at 300 °C for 2 h, with a heating rate of 5 °C / min. -1 The obtained pre-carbonized product and potassium hydroxide were thoroughly ground and mixed evenly, and then subjected to high-temperature carbonization and activation under argon protection, with the temperature decreasing from room temperature in increments of 5 °C / min. -1 The heating rate increased to 850 o C, kept at a constant temperature for 2 h, then cooled to room temperature to obtain the product. The mass ratio of the pre-carbonized product to potassium hydroxide was 1:3. The obtained carbonized activated product was dissolved in 40 ml of deionized water and heated at 5000 r / min. -1 After centrifugation, the material was dissolved again and a small amount of diluted hydrochloric acid was added dropwise until neutral. After washing with deionized water and centrifuging 2-3 times, the precipitate was dried in an oven at 80 ℃ to obtain coal tar pitch-based porous carbon (SHC). -550r min -1 The obtained porous carbon has a specific surface area of ​​2,606.56 m². 2 .g -1 The mesoporosity is 63.58%, which is a significant increase in specific surface area and mesoporosity compared to Example 2. Figure 3The figures for the galvanostatic charge-discharge curves of the coal tar pitch-based porous carbon material obtained in Example 6 at different current densities are shown. The results indicate that the galvanostatic charge-discharge curves exhibit good symmetry at different current densities, suggesting that the electrode material possesses typical double-layer capacitance characteristics. The calculated values ​​at 1 A g... -1 The specific capacitance at the current density is as high as 324.6 F g. -1 . Figure 2 The electrochemical impedance spectroscopy also shows that its charge transfer resistance is the lowest. Figure 4 The graphs show the specific capacitance performance calculated under different current densities. The results show that the electrode material has good rate performance.

Claims

1. A method for preparing coal tar pitch-based porous carbon for supercapacitors, characterized in that, Includes the following steps: (1) A mixture is obtained by mixing 200-300 mesh coal tar powder with 200-300 mesh thermosetting phenolic resin powder, with a mass ratio of coal tar powder to phenolic resin powder of (2-5):1; (2) Take the mixture and pre-carbonize it in a tube furnace under an argon atmosphere at 300℃-400℃ for 1-3 hours to obtain the pre-carbonized product; (3) Grind and mix the pre-carbonized product and potassium hydroxide evenly, and carry out high-temperature carbonization and activation under argon protection. The temperature is raised from room temperature to 800℃-900℃, kept at a constant temperature for 1-3 hours, and then cooled to room temperature to obtain the carbonized and activated product. The mass ratio of the pre-carbonized product to potassium hydroxide is 1:(1~5). (4) Dissolve the carbonization and activation product in deionized water and acidify it to neutral; After washing, centrifugation, and drying, pitch-based porous carbon was obtained; The mixing method for coal tar pitch powder and phenolic resin powder is as follows: Place the coal tar pitch powder and phenolic resin powder in the grinding jar of a planetary ball mill, and mix at 350-550 r / min. 1 Ball milling at high speed.

2. The application of the pitch-based porous carbon prepared by the method according to claim 1, characterized in that: The pitch-based porous carbon is used as an electrode material for electric double-layer capacitors.

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