A method for preparing coal tar pitch-based porous hard carbon and its application

Abstract

This invention relates to a method for preparing and applying coal tar pitch-based porous hard carbon, belonging to the field of carbon material preparation technology. The invention uses coal tar pitch as raw material. After hydrothermal treatment of coal tar pitch and boric acid, followed by stirring and drying, the material is activated first with an alkali and then with an acid. While adjusting the pH, the surface is eroded to generate more pores, increasing the specific surface area of ​​the material. The coal tar pitch-based porous hard carbon prepared by this invention, as an electrode material, can increase battery capacity, improve battery cycle life and stability, and enhance the electrochemical performance of hard carbon. Its specific capacity is more than twice that of the theoretical specific capacity of traditional graphite. This invention provides new ideas and methods for coal tar pitch processing, expands the application of coal tar pitch in the energy storage field, reduces production costs, and facilitates practical application and large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation technology, specifically relating to a method for preparing coal tar pitch-based porous hard carbon and its application. Background Technology

[0002] Coal tar pitch is a heavy component in high-temperature coal tar, a byproduct of the coking industry. Its composition and structure are very complex, with the vast majority consisting of polycyclic aromatic hydrocarbons and their derivatives. It has a carbon content of up to about 90% and is characterized by high aromaticity, high degree of condensation, and high toxicity.

[0003] Currently, the processing of coal tar pitch suffers from problems such as low technological integration, severe environmental damage, and low product added value. Hard carbon is a type of amorphous carbon that is difficult to graphitize even above 2500℃, and is named for its high mechanical hardness. Common hard carbon pyrolysis precursors are some artificial polymers and sugars, such as phenolic resins, glucose, sucrose, furfural, and cellulose. Compared with graphite, hard carbon has a larger interlayer spacing and more micropores, resulting in more ion insertion and extraction active sites. It has a higher specific capacity when used in battery anodes and capacitors, making it an ideal energy storage material. Coal tar pitch-based hard carbon is a porous carbon material with a low degree of graphitization, exhibiting short-range order but long-range disorder and a disordered layered structure. Currently, the preparation of hard carbon using coal tar pitch as a precursor is complex and costly, and it does not offer significant advantages over commercial graphite in terms of price and performance, hindering its practical application. Summary of the Invention

[0004] The purpose of this invention is to achieve targeted control of the material structure through hydrothermal and acid-base treatment, while reducing production costs and improving its performance in energy storage applications.

[0005] To achieve the purpose of this invention, this invention uses various acids and bases as structure regulators and coal tar pitch as a carbon source to prepare coal tar pitch-based porous carbon.

[0006] A method for preparing coal tar pitch-based porous hard carbon includes the following steps:

[0007] S1: Coal tar pitch and boric acid are placed in a hydrothermal reactor and mixed with water and ethanol to obtain a mixed solution. After hydrothermal reaction, the solution is naturally cooled to room temperature.

[0008] S2: Stir and dry the mixed solution. After the water and ethanol evaporate, put the residue into a tube furnace and heat it to 190-210°C in air at a rate of 4-6°C / min and keep it at that temperature for 2-4 hours to obtain the mixture.

[0009] S3: Take out the mixture, mix and grind it with potassium hydroxide, put it into a tube furnace, heat it to 700-900℃ in a nitrogen atmosphere at a rate of 4-6℃ / min, and hold it for 2-4 hours; let it cool naturally to room temperature and take out the sample.

[0010] S4: The sample after ball milling is placed in sodium hydroxide solution and stirred. After stirring, the sample is collected by vacuum filtration. Then, it is placed in dilute hydrochloric acid or acetic acid and stirred. After stirring, the sample is collected by vacuum filtration and washed with deionized water until neutral. The sample is then vacuum dried to remove moisture, and asphalt-based porous hard carbon is obtained.

[0011] Furthermore, the mass ratio of coal tar pitch to boric acid in S1 is 4 to 2:1; the volume ratio of water to ethanol is 2:8, 3:7, 2:3 or 5:5.

[0012] Furthermore, the hydrothermal reaction in S1 is carried out at a temperature of 80–150 °C for 12 hours.

[0013] Furthermore, S3 grinding is performed using a mortar and pestle or a ball mill, grinding and mixing until there are no obvious particles.

[0014] Furthermore, the mass ratio of the mixture described in S3 to potassium hydroxide is 1:3.

[0015] Furthermore, in S4, the ball mill speed is 400–800 r / min, the ball-to-material ratio is 20:1, and the ball milling time is 6–12 h.

[0016] Furthermore, the stirring temperature described in S4 is 20–50°C, and the stirring time is 6–12 hours.

[0017] Furthermore, the concentration of sodium hydroxide solution, dilute hydrochloric acid, or acetic acid used in S5 and S6 is 0.5–1.5 mol / L.

[0018] The application of coal tar pitch-based porous hard carbon prepared by the above method as an electrode material in sodium-ion or lithium-ion batteries.

[0019] Compared with the prior art, the present invention uses inexpensive and readily available coal tar pitch as raw material. After hydrothermal treatment and stirring and drying, the coal tar pitch is first activated by mixing with potassium hydroxide, and then treated with dilute hydrochloric acid or acetic acid to create pores and activate surface functional groups, thereby improving the internal pore structure of the material. The innovative use of alkali and acid for activation, while adjusting the pH, erodes the surface to give it a larger specific surface area.

[0020] The method of first activating with strong alkali and then with strong acid removes ash from the material and generates more pores to increase the specific surface area of ​​the material compared with other activation methods. The advantages of rich pore structure and specific surface area are: (1) Increase the lithium ion diffusion rate: The pore structure can provide more ion storage space and is conducive to the diffusion of ions inside the material; the richer the pore structure, the larger the specific surface area, which can improve the ion transport rate in the material, thereby improving the charge and discharge performance of the battery; (2) Increase the ion storage capacity: The increase of pore structure and specific surface area can improve the capacity of the material, because more ions can be adsorbed on the pore wall or embedded in the pore structure, thereby increasing the battery capacity; (3) Improve the electrode stability: The pore structure can alleviate the volume expansion problem of hard carbon materials during ion insertion / extraction, reduce the structural damage and capacity decay of electrode materials, thereby improving the cycle life and stability of the battery, and improving the electrochemical performance of hard carbon. Its specific capacity is more than twice that of the theoretical specific capacity of traditional graphite, providing new ideas and methods for coal tar pitch processing, opening up the application of coal tar pitch in the field of energy storage, reducing production costs, and facilitating practical application and large-scale production. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the preparation process of coal tar pitch-based porous hard carbon according to the present invention.

[0022] Figure 2 SEM images of the materials (N1-H1) prepared in Example 1;

[0023] Figure 3 The XRD pattern of the material (N1-H1) prepared in Example 1;

[0024] Figure 4 The Raman spectra of the materials (N1-H1) prepared in Example 1;

[0025] Figure 5 The nitrogen adsorption-desorption curves of the material (N1-H1) prepared in Example 1 are shown.

[0026] Figure 6 The first charge-discharge cycle of the lithium-ion battery assembled with the material (N1-H1) prepared in Example 1 at a current density of 100 mAh / g;

[0027] Figure 7 The graph shows lithium-ion batteries assembled from materials (N1-H1) prepared in Example 1 at different rate.

[0028] Figure 8 The diagram shows sodium-ion batteries assembled with materials (N1-H1) prepared in Example 1 at different rate. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for preparing coal tar pitch-based porous hard carbon (N1-H1), such as... Figure 1 As shown, it includes the following steps:

[0032] 1) Weigh 1g of coal tar pitch and 0.5g of boric acid and dissolve them in 20ml of water and 30ml of ethanol. After mixing evenly, place the mixture in a hydrothermal reactor and hydrothermally treat it at 80℃ for 12h. Then, let it cool naturally to room temperature.

[0033] 2) Stir and dry the mixed solution at 50°C to evaporate all the solvent. Place the residue in a tube furnace and heat it to 200°C in air at a rate of 5°C / min and hold it at that temperature for 3 hours. Then let it cool naturally to room temperature to obtain the mixture.

[0034] 3) Place the mixture and 3g of potassium hydroxide in a grinder and grind until all the potassium hydroxide is broken down into no obvious particles. After mixing evenly, transfer it to a tube furnace and heat it to 800℃ at a rate of 5℃ / min in a nitrogen atmosphere, and keep it at that temperature for 3 hours. Allow it to cool naturally to room temperature, take out the sample and weigh it.

[0035] 3) Use a ball mill to ball mill the corundum balls and the sample with a ball-to-material ratio of 20:1 at 600 r / min for 12 h.

[0036] 4) Dissolve the ball-milled sample in 100 mL (1 mol / L) sodium hydroxide solution and stir for 12 h. Collect the sample by filtration.

[0037] Dissolve the sample again in 100 mL (1 mol / L) hydrochloric acid solution and stir for 12 h. Collect the sample by filtration and wash with deionized water until neutral.

[0038] 5) Place the collected samples in a vacuum drying oven and dry them at a constant temperature of 60℃ for 12 hours to prepare the hard carbon anode material (N1-H1) for the battery. Figure 2 SEM images of the materials (N1-H1) prepared in this embodiment; Figure 3 The XRD pattern of the material (N1-H1) prepared in this embodiment; Figure 4 The Raman spectra of the materials (N1-H1) prepared in this embodiment; Figure 5 The nitrogen adsorption-desorption curves of the material (N1-H1) prepared in this embodiment are shown.

[0039] The application of coal tar pitch-based porous hard carbon prepared by the above method as an electrode material in sodium-ion batteries. Figure 6 The first charge-discharge cycle of the lithium-ion battery assembled with the material (N1-H1) prepared in this embodiment at a current density of 100 mAh / g was performed.

[0040] Figure 7 The graph shows the different rate capability of the lithium-ion battery assembled from the materials (N1-H1) prepared in this embodiment. Figure 8 The diagram shows the different rate capability diagrams of sodium-ion batteries assembled with the materials (N1-H1) prepared in this embodiment.

[0041] Example 2

[0042] A method for preparing coal tar pitch-based porous hard carbon (N1-C1) includes the following steps:

[0043] Based on Example 1, keeping other conditions unchanged, step 4) involves dissolving the ball-milled sample in 100 mL (1 mol / L) sodium hydroxide solution and stirring for 12 h. The sample is then collected by filtration; subsequently, it is dissolved in 100 mL (1 mol / L) acetic acid solution and stirred for 12 h. The sample is collected by filtration and washed with deionized water until neutral.

[0044] Example 3

[0045] A method for preparing coal tar pitch-based porous hard carbon (NO.5-H1) includes the following steps:

[0046] Based on Example 1, keeping other conditions unchanged, step 4) involves dissolving the ball-milled sample in 100 mL (0.5 mol / L) sodium hydroxide solution and stirring for 12 h. The sample is then collected by filtration; subsequently, it is dissolved in 100 mL (1 mol / L) hydrochloric acid solution and stirred for 12 h. The sample is collected by filtration and washed with deionized water until neutral.

[0047] Example 4

[0048] A method for preparing coal tar pitch-based porous hard carbon (NO.5-Cl) includes the following steps:

[0049] Based on Example 1, keeping other conditions unchanged, step 4) involves dissolving the ball-milled sample in 100 mL (0.5 mol / L) sodium hydroxide solution and stirring for 12 h. The sample is then collected by filtration; subsequently, it is dissolved in 100 mL (1 mol / L) acetic acid solution and stirred for 12 h. The sample is collected by filtration and washed with deionized water until neutral.

[0050] Example 5

[0051] A method for preparing coal tar pitch-based porous hard carbon (B3-N1-C1) includes the following steps:

[0052] Based on Example 1, keeping other conditions unchanged, step 1) is to weigh 1g of coal tar pitch and 0.3g of boric acid, dissolve them in 20ml of water and 30ml of ethanol, mix them evenly, place them in a hydrothermal reactor, and hydrothermally treat them at 80℃ for 12h, and then naturally cool them to room temperature.

[0053] Example 6

[0054] A method for preparing coal tar pitch-based porous hard carbon (N1-O) includes the following steps:

[0055] Based on Example 1, keeping other conditions unchanged, 4) is to wash the ball-milled balls with deionized water.

[0056] Example 7

[0057] A method for preparing coal tar pitch-based porous hard carbon (N1-O-H1) includes the following steps:

[0058] Based on Example 1, keeping other conditions unchanged, 4) the ball-milled sample was dissolved in 100 mL (1 mol / L) hydrochloric acid solution and stirred for 12 h. The sample was collected by filtration and washed with deionized water until neutral.

[0059] Example 8

[0060] A method for preparing coal tar pitch-based porous hard carbon (N1-OHH1-O) includes the following steps:

[0061] Based on Example 1, keeping other conditions unchanged, 4) the ball-milled sample was first dissolved in 100 mL (1 mol / L) sodium hydroxide solution and stirred for 12 h. The sample was collected by filtration and washed with deionized water until neutral.

[0062] Example 9

[0063] A method for preparing coal tar pitch-based porous hard carbon (N1-H1-OHH1) includes the following steps:

[0064] Based on Example 1, keeping other conditions unchanged, 4) the ball-milled sample was first dissolved in 100 mL (1 mol / L) hydrochloric acid solution and stirred for 12 h. The sample was then collected by filtration; then dissolved in 100 mL (1 mol / L) sodium hydroxide solution and stirred for 12 h. The sample was collected by filtration and washed with deionized water until neutral.

[0065] Table 1 shows the specific surface area, porosity, and average pore size of the materials prepared in Examples 1-9, and Table 2 shows the capacity of lithium / sodium-ion batteries assembled with the materials prepared in Examples 1-9 at different current densities.

[0066] <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Porosity (cm 3 / g)]]> Average pore size (nm) Example 1 2203.6213 1.20382 2.5548 Example 2 1865.1654 1.06981 2.5149 Example 3 2152.3680 1.16595 2.5494 Example 4 1798.6545 0.98512 2.5648 Example 5 2187.6591 1.18791 2.5561 Example 6 1581.6143 0.83317 2.5358 Example 7 1535.2647 0.91141 2.7009 Example 8 1271.0796 0.72247 2.5628 Example 9 1344.0733 0.69919 2.6358

[0067] Table 1

[0068]

[0069]

[0070] Table 2

Claims

1. A method for preparing coal tar pitch-based porous hard carbon, characterized in that: Includes the following steps: S1: Coal tar pitch and boric acid are placed in a hydrothermal reactor and mixed with water and ethanol to obtain a mixed solution. After hydrothermal reaction, the solution is naturally cooled to room temperature. S2: Stir and dry the mixed solution. After the water and ethanol evaporate, put the residue into a tube furnace and heat it to 190-210°C in air at a rate of 4-6°C / min and keep it at that temperature for 2-4 hours to obtain the mixture. S3: Take out the mixture, mix and grind it with potassium hydroxide, put it into a tube furnace, heat it to 700~900℃ in a nitrogen atmosphere at a rate of 4~6℃ / min, and hold it for 2~4h; let it cool naturally to room temperature and take out the sample; S4: The sample after ball milling is placed in sodium hydroxide solution and stirred. After stirring, the sample is collected by vacuum filtration. Then, it is placed in dilute hydrochloric acid or acetic acid and stirred. After stirring, the sample is collected by vacuum filtration and washed with deionized water until neutral. The sample is then vacuum dried to remove moisture and obtain asphalt-based porous hard carbon. The mass ratio of coal tar pitch to boric acid in S1 is 4 to 2:1; the volume ratio of water to ethanol is 2:8, 3:7, 2:3 or 5:

5. The hydrothermal reaction in S1 is carried out at a temperature of 80~150℃ for 12 hours. The ball mill in S4 operates at a speed of 400-800 r / min, a ball-to-material ratio of 20:1, and a milling time of 6-12 h.

2. The method for preparing coal tar pitch-based porous hard carbon according to claim 1, characterized in that: S3 grinding uses a mortar and pestle or a ball mill to grind and mix until there are no obvious particles.

3. The method for preparing coal tar pitch-based porous hard carbon according to claim 1, characterized in that: The mass ratio of the mixture described in S3 to potassium hydroxide is 1:

3.

4. The method for preparing coal tar pitch-based porous hard carbon according to claim 1, characterized in that: The stirring temperature described in S4 is 20~50℃, and the stirring time is 6~12h.

5. The method for preparing coal tar pitch-based porous hard carbon according to claim 1, characterized in that: The sodium hydroxide solution, dilute hydrochloric acid, or acetic acid used in S4 has a concentration of 0.5~1.5 mol / L.

6. The application of coal tar pitch-based porous hard carbon prepared by the preparation method according to any one of claims 1-5 as an electrode material in sodium-ion or lithium-ion batteries.

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