A porous graphite material and its preparation method

Abstract

The present invention discloses a porous graphite material and a preparation method thereof, belonging to the technical field of graphite materials. The preparation method includes: respectively grinding calcined pitch coke, pitch and dry starch to obtain aggregate powder, binder and bulking agent; kneading the aggregate powder and the bulking agent with the binder respectively to obtain a first paste and a first coated material, grinding the first paste and the first coated material again to obtain a second paste and a second coated material, mixing the two to obtain pressed powder, subjecting the pressed powder to isostatic pressing to obtain a green body, and then performing roasting and graphitization treatment to obtain the porous graphite material. The porous graphite material obtained by the present invention has a high porosity, uniform pore distribution, controllable pore size, high material strength, high open porosity, excellent performance indicators, and is environmentally friendly and pollution-free in the production process.

Description

Technical Field

[0001] The present invention relates to the technical field of graphite materials, and particularly to the technical field of porous graphite materials. Background Art

[0002] Porous graphite materials have a special pore structure, with a large specific surface area and a high porosity. They can be used as electrode materials for energy storage devices such as supercapacitors and lithium-ion batteries, carrier materials for catalysts, adsorption materials for wastewater and waste gas treatment, processing materials for air bearing, control materials for the growth of silicon carbide semiconductor crystals, etc., and have important application values. Currently, the existing porous graphite materials generally have disadvantages such as uneven pore distribution, many internal defects, and low mechanical strength, and cannot meet the applications in high-end fields such as semiconductors and air cushions. Summary of the Invention

[0003] Aiming at the defects of the prior art, the purpose of the present invention is to provide a new porous graphite material and its preparation method. The preparation method can precisely control the pore size, pore size distribution, and porosity of the material. The obtained porous graphite material has high mechanical strength, narrow pore size distribution, uniform pore distribution, and no internal defects, filling the gap of high-performance porous graphite materials.

[0004] The technical solution of the present invention is as follows:

[0005] A preparation method of a porous graphite material, which includes:

[0006] (1) Grinding calcined pitch coke to obtain aggregate powder, grinding asphalt to obtain binder, and grinding dry starch to obtain bulking agent;

[0007] (2) Kneading the aggregate powder with the first part of the binder to obtain the first paste, and kneading the bulking agent with the second part of the binder to obtain the first coating material;

[0008] (3) Grinding the first paste to obtain the second paste, and grinding the first coating material to obtain the second coating material;

[0009] (4) Mixing the second paste with the second coating material to obtain pressed powder;

[0010] (5) Isostatically pressing the pressed powder to obtain a green body;

[0011] (6) Baking the green body to obtain a porous carbon material;

[0012] (7) Graphitizing the porous carbon material to obtain a porous graphite material.

[0013] In the above technical solution of the present invention, the calcined pitch coke after grinding is used as the aggregate, which can play a significant role in enhancing the material. After the finer binder grinding particles are fully and evenly mixed with the aggregate powder and the bulking agent through kneading, they can be evenly coated on the surface of the aggregate powder or the bulking agent during the melting process, enhancing the bonding strength between the aggregate powder or the bulking agent particles. The aggregate powder and the bulking agent are respectively kneaded with the binder. After re-grinding, a good binder coating can be formed on the surface of the second paste and the second coating material, and the affinity between the particles is stronger, which can significantly enhance the strength of the final material.

[0014] In the above technical solution of the present invention, the selected bulking agent has a low residual carbon rate and can form good pores after roasting. By controlling the particle size of the bulking agent, pores with corresponding sizes can be accurately obtained. Generally, a narrower particle size distribution of the bulking agent can obtain a narrower pore size distribution.

[0015] The above technical solution of the present invention adopts a secondary grinding process, which can precisely control the second paste particles and the second coating material particles, make them fully mixed, and make the pressed powder components after mixing uniform. Subsequently, through isostatic pressing, the uniformity of the pore distribution inside the material can be guaranteed. At the same time, the bulking agent particles can be evenly distributed in the material, generating uniform pores and pore channels during the roasting process, and enabling the decomposition products of the binder and the bulking agent to be discharged smoothly, significantly reducing the probability of defects generated inside the material.

[0016] According to some preferred embodiments of the present invention, the D50 particle size of the aggregate powder is 15 - 20 μm.

[0017] According to some preferred embodiments of the present invention, the D50 particle size of the binder is 8 - 12 μm.

[0018] According to some preferred embodiments of the present invention, the D50 particle size of the bulking agent is 20 - 50 μm.

[0019] According to some preferred embodiments of the present invention, the D50 particle size of the second paste is 50 - 150 μm.

[0020] According to some preferred embodiments of the present invention, the D50 particle size of the second coating material is 20 - 70 μm.

[0021] In the above preferred embodiments of the present invention, by controlling the size and distribution of the particle sizes of each component, not only can the particles of each component be made more uniform, but also the uniformity inside the material and the uniformity of the pore distribution can be improved, reducing the generation of defects. Among them, by controlling the size and distribution of the bulking agent particles, the purpose of controlling the pore size and distribution can be achieved.

[0022] According to some preferred embodiments of the present invention, in the first paste, the mass content ratio of the aggregate powder to the first part of the binder is 50-65%:50-35%.

[0023] According to some preferred embodiments of the present invention, in the first coating material, the mass content ratio of the bulking agent to the second part of the binder is 75-85%:25-15%.

[0024] According to some preferred embodiments of the present invention, in the pressed powder, the mass content ratio of the second paste to the second coating material is 30-65%:70-35%.

[0025] According to some preferred embodiments of the present invention, the ash content of the calcined pitch coke is ≤0.3%, the moisture content is ≤0.1%, the volatile content is ≤0.5%, and the carbon content is ≥99%.

[0026] According to some preferred embodiments of the present invention, the ash content of the asphalt is ≤0.2%, the moisture content is ≤0.2%, the quinoline insoluble content is ≤5%, and the softening point is 110-125°C.

[0027] According to some preferred embodiments of the present invention, the kneading for obtaining the first paste includes: dry-mixing the aggregate powder until the dry-mixing temperature reaches above 180°C, then adding the first part of the binder, and performing wet-mixing at 220-250°C for 1-2 hours, and then cooling to obtain the first paste.

[0028] According to some preferred embodiments of the present invention, the kneading for obtaining the first coating material includes: dry-mixing the bulking agent until the dry-mixing temperature reaches above 220°C, then adding the second part of the binder, and performing wet-mixing at 220-240°C for 0.5-1 hour, and then cooling to obtain the first coating material.

[0029] According to some preferred embodiments of the present invention, the volatile content of the first paste obtained after kneading is 12-15%.

[0030] According to some preferred embodiments of the present invention, the mixing of the second paste and the second coating material includes: adding the second paste and the second coating material to a V-type mixer and mixing for 1-1.5 hours.

[0031] According to some preferred embodiments of the present invention, the isostatic pressing includes: loading the pressed powder into a rubber membrane sleeve, sealing it and evacuating, and then performing pressing by an isostatic press.

[0032] According to some preferred embodiments of the present invention, the pressure of the isostatic pressing is 130-150 MPa.

[0033] According to some preferred embodiments of the present invention, the roasting includes: loading the green body into a roasting crucible filled with yellow sand, and then roasting in a roasting furnace.

[0034] According to some preferred embodiments of the present invention, the roasting includes: heating from room temperature to 200 °C at a heating rate of 10-20 °C / h under 4.0-4.5 Mpa, then heating from 200 °C to 350 °C at a heating rate of 2-4 °C / h, then heating from 350 °C to 550 °C at a heating rate of 3-5 °C / h, heating from 550 °C to 750 °C at a heating rate of 6-8 °C / h, heating from 750 °C to 950 °C at a heating rate of 8-12 °C / h, holding at 950 °C for 6-12 h, then cooling from 950 °C to 600 °C at a cooling rate of 30-50 °C / h, and then naturally cooling to room temperature.

[0035] According to some preferred embodiments of the present invention, the graphitization treatment includes: heating from room temperature to 750 °C at a heating rate of 80-120 °C / h, heating from 750 °C to 1350 °C at a heating rate of 50-80 °C / h, heating from 1350 °C to 1600 °C at a heating rate of 30-50 °C / h, heating from 1600 °C to 1900 °C at a heating rate of 15-30 °C / h, heating from 1900 °C to 2400 °C at a heating rate of 50-80 °C / h, and holding for 4-6 h, and then naturally cooling.

[0036] The above hot-pressing roasting scheme of the present invention can effectively improve the coking value of the binder and enhance the material strength. At the same time, during the key temperature stage of the decomposition of the bulking agent and the binder, it slowly heats up at a lower heating rate, which can reduce the temperature difference inside the material, make the interior of the roasted material more uniform, and also avoid the generation of defects.

[0037] The present invention further provides a porous graphite material prepared according to the above preparation method.

[0038] This porous graphite material has a uniform microstructure, a high open porosity, and the porosity can be adjusted within a large range of 30-50%. At the same time, the pores penetrate and communicate with each other.

[0039] According to some preferred embodiments of the present invention, by adjusting the particle size and proportion of the bulking agent, the pore diameter of the obtained porous graphite material is 5-55 μm and the flexural strength is greater than 35 MPa.

[0040] The present invention has the following beneficial effects:

[0041] The bulking agent used in the present invention is a biomass material, which is cheap, has significant economic advantages, and there is no environmental pollution in the production process;

[0042] The preparation method of the present invention can precisely control the pore size, pore size distribution, and porosity of the obtained porous graphite material;

[0043] The porous graphite material obtained by the present invention has high mechanical strength, narrow pore size distribution, uniform pore distribution, and no internal defects. Description of the Drawings

[0044] Figure 1 It is a process flow chart for the preparation of the porous graphite material in the examples.

[0045] Figure 2 It is a SEM image of the porous graphite material obtained in Example 1.

[0046] Figure 3 It is a SEM image of the porous graphite material obtained in Example 2.

[0047] Figure 4 It is a SEM image of the porous graphite material obtained in Example 3. Detailed Embodiments

[0048] The technical solutions in the present invention will be further described below in conjunction with the embodiments and drawings of the present invention. The following described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] Example 1

[0050] Refer to the attached Figure 1 , and prepare the porous graphite material through the following steps:

[0051] (1) Grind the raw materials, including:

[0052] Grind the calcined pitch coke with an ash content of 0.25%, a moisture content of 0.05%, a volatile content of 0.32%, and a carbon content of 99.4% to obtain aggregate powder A with a D50 particle size of 20 μm;

[0053] Grind the pitch with an ash content of 0.15%, a moisture content of 0.12%, a quinoline insoluble content of 3.8%, and a softening point of 118°C to obtain binder B with a D50 particle size of 10 μm;

[0054] Grind the starch with a moisture content of 0.06% dried at 120°C to obtain bulking agent C with a D50 particle size of 45 μm;

[0055] (2) Knead, including:

[0056] Weigh aggregate powder A and binder B with masses of 63% and 37% respectively. Add aggregate powder A to a kneader for dry mixing. When the dry mixing temperature reaches 185°C, add binder B for wet mixing. The wet mixing time is 2 h, and the wet mixing temperature is 220 - 250°C. After discharging and cooling, paste D is obtained, and its volatile content is 12.4%.

[0057] Weigh bulking agent C and binder B with masses of 85% and 15% respectively. Add bulking agent C to a kneader for dry mixing. When the dry mixing temperature reaches 225°C, add binder B for wet mixing. The wet mixing time is 0.5 h, and the wet mixing temperature is 220 - 240°C. After discharging and cooling, coated material E is obtained.

[0058] (3)Secondary grinding, including:

[0059] Grind paste D to obtain paste powder E with a D50 particle size of 145 μm.

[0060] Grind coated material E to obtain coated powder F with a D50 particle size of 65 μm.

[0061] (4)Mixing:

[0062] Weigh paste powder E and coated powder F with masses of 40% and 60% respectively, and add them to a V-type mixer for mixing for 1.5 h to obtain pressed powder H.

[0063] (5)Green body forming:

[0064] Load pressed powder H into a rubber membrane sleeve, seal it, evacuate it, and then press it in an isostatic press to obtain green body K. The isostatic pressure is 140 MPa.

[0065] (6)Baking:

[0066] Load green body K into a baking crucible, fill the crucible with yellow sand for protection, and bake it in a baking furnace at a pressure of 4.0 MPa to obtain porous carbon M. The baking process is as follows: heat from room temperature to 200°C at a heating rate of 20°C / h, heat from 200°C to 350°C at a heating rate of 3°C / h, heat from 350°C to 550°C at a heating rate of 4°C / h, heat from 550°C to 750°C at a heating rate of 8°C / h, heat from 750°C to 950°C at a heating rate of 12°C / h, hold at 950°C for 8 h, and then cool from 950°C to 600°C at a cooling rate of 45°C / h, and then cool naturally to room temperature.

[0067] (7)Graphitization:

[0068] The porous carbon M is loaded into a vacuum graphitization furnace for graphitization treatment to obtain the porous graphite material S. The process of graphitization treatment is as follows: heating from room temperature to 750 °C at a heating rate of 115 °C / h, heating from 750 °C to 1350 °C at a heating rate of 75 °C / h, heating from 1350 °C to 1600 °C at a heating rate of 50 °C / h, heating from 1600 °C to 1900 °C at a heating rate of 30 °C / h, heating from 1900 °C to 2400 °C at a heating rate of 70 °C / h, and holding for 6 h, followed by natural cooling.

[0069] The obtained porous graphite material is characterized by its microstructure, and the SEM image obtained is as attached Figure 2 shown. It can be seen that the material has well-developed pores inside, a narrow pore size distribution, larger pore sizes are formed by larger blowing agents, the average pore size is 55 microns, channels are formed between pores, and the particles are tightly connected, enabling the material to maintain high mechanical strength.

[0070] Example 2

[0071] Referring to the attachment Figure 1 , the porous graphite material is prepared through the following steps:

[0072] (1) Grinding the raw materials, including:

[0073] Grinding the calcined pitch coke with an ash content of 0.25%, a moisture content of 0.05%, a volatile content of 0.32%, and a carbon content of 99.4% to obtain the aggregate powder A with a D50 particle size of 15 μm;

[0074] Grinding the pitch with an ash content of 0.15%, a moisture content of 0.12%, a quinoline insoluble content of 3.8%, and a softening point of 118 °C to obtain the binder B with a D50 particle size of 10 μm;

[0075] Grinding the starch with a moisture content of 0.06% dried at 120 °C to obtain the blowing agent C with a D50 particle size of 25 μm;

[0076] (2) Kneading, including:

[0077] Weigh the aggregate powder A and the binder B with masses of 55% and 45% respectively. Add the aggregate powder A to a kneader for dry mixing. When the dry mixing temperature reaches 185 °C, add the binder B for wet mixing. The wet mixing time is 1 h, and the wet mixing temperature is 220 - 250 °C. After discharging and cooling, the paste D is obtained, and its volatile content is 14.7%;

[0078] Weigh the bulking agent C and the binder B with masses of 75% and 25% respectively. Add the bulking agent C to the kneader for dry mixing. When the dry mixing temperature reaches 225°C, add the binder B for wet mixing. The wet mixing time is 0.5 h, and the wet mixing temperature is 220 - 240°C. After taking out of the pot and cooling, obtain the coated material E;

[0079] (3)Secondary grinding, including:

[0080] Grind the paste D to obtain the paste powder E with a D50 particle size of 55 μm;

[0081] Grind the coated material E to obtain the coated powder F with a D50 particle size of 32 μm;

[0082] (4)Mixing:

[0083] Weigh the paste powder E and the coated powder F with masses of 60% and 40% respectively, add them to a V-type mixer and mix for 1.5 h to obtain the pressed powder H;

[0084] (5)Green body forming:

[0085] Put the pressed powder H into a rubber membrane sleeve, seal it and evacuate, then put it into an isostatic press for molding to obtain the green body K. The isostatic pressure is 150 MPa;

[0086] (6)Roasting:

[0087] Put the green body K into a roasting crucible, fill the crucible with yellow sand for protection, and roast it in a roasting furnace under a pressure of 4.5 MPa to obtain the porous carbon M. The roasting process is as follows: heat from room temperature to 200°C at a heating rate of 10°C / h, heat from 200°C to 350°C at a heating rate of 2°C / h, heat from 350°C to 550°C at a heating rate of 3°C / h, heat from 550°C to 750°C at a heating rate of 6°C / h, heat from 750°C to 950°C at a heating rate of 8°C / h, keep it at 950°C for 12 h, then cool from 950°C to 600°C at a cooling rate of 30°C / h, and then cool naturally to room temperature;

[0088] (7)Graphitization:

[0089] Put the porous carbon M into a vacuum graphitization furnace for graphitization treatment to obtain the porous graphite material S. The graphitization treatment process is as follows: heat from room temperature to 750°C at a heating rate of 80°C / h, heat from 750°C to 1350°C at a heating rate of 50°C / h, heat from 1350°C to 1600°C at a heating rate of 30°C / h, heat from 1600°C to 1900°C at a heating rate of 15°C / h, heat from 1900°C to 2400°C at a heating rate of 50°C / h, and keep it at 2400°C for 6 h, then cool naturally.

[0090] The obtained porous graphite material was characterized microstructurally, and the SEM images obtained are as shown in the appendix Figure 3 It can be seen that the smaller blowing agent particles inside the material form smaller pore diameters. The average pore diameter is 30 μm, the particle and pore size distributions are uniform, and the combination between particles is tighter.

[0091] Example 3

[0092] Refer to the appendix Figure 1 , and a porous graphite material was prepared through the following steps:

[0093] (1) Grinding the raw materials, including:

[0094] The calcined pitch coke with an ash content of 0.25%, a moisture content of 0.05%, a volatile content of 0.32%, and a carbon content of 99.4% was ground to obtain aggregate powder A with a D50 particle size of 18 μm;

[0095] The pitch with an ash content of 0.15%, a moisture content of 0.12%, a quinoline insoluble content of 3.8%, and a softening point of 118°C was ground to obtain binder B with a D50 particle size of 10 μm;

[0096] The starch with a moisture content of 0.06% dried at 120°C was ground to obtain blowing agent C with a D50 particle size of 30 μm;

[0097] (2) Kneading, including:

[0098] Weigh aggregate powder A and binder B with masses of 60% and 40% respectively. Add aggregate powder A to the kneader for dry mixing. When the dry mixing temperature reaches 185°C, add binder B for wet mixing. The wet mixing time is 1.5 h, and the wet mixing temperature is 220 - 250°C. After discharging from the pot and cooling, paste D is obtained, and its volatile content is 13.8%;

[0099] Weigh blowing agent C and binder B with masses of 80% and 20% respectively. Add blowing agent C to the kneader for dry mixing. When the dry mixing temperature reaches 225°C, add binder B for wet mixing. The wet mixing time is 1 h, and the wet mixing temperature is 220 - 240°C. After discharging from the pot and cooling, coating material E is obtained;

[0100] (3) Secondary grinding, including:

[0101] Grind paste D to obtain paste powder E with a D50 particle size of 100 μm;

[0102] Grind coating material E to obtain coating powder F with a D50 particle size of 45 μm;

[0103] (4) Mixing:

[0104] Weigh paste powder E and coating powder F with masses of 45% and 55% respectively, add them to a V-type mixer and mix for 1.5 h to obtain compacted powder H;

[0105] (5)Green body forming:

[0106] Put the compacted powder H into a rubber membrane sleeve, seal it and evacuate it, then put it into an isostatic press for molding to obtain a green body K, and the isostatic pressure is 145 MPa;

[0107] (6)Roasting:

[0108] Put the green body K into a roasting crucible, fill the crucible with yellow sand for protection, and roast it in a roasting furnace at a pressure of 4.3 MPa to obtain porous carbon M. The roasting process is as follows: heat from room temperature to 200 °C at a heating rate of 10 °C / h, heat from 200 °C to 350 °C at a heating rate of 3 °C / h, heat from 350 °C to 550 °C at a heating rate of 4 °C / h, heat from 550 °C to 750 °C at a heating rate of 7 °C / h, heat from 750 °C to 950 °C at a heating rate of 10 °C / h, hold at 950 °C for 10 h, then cool from 950 °C to 600 °C at a cooling rate of 40 °C / h, and then cool naturally to room temperature;

[0109] (7)Graphitization:

[0110] Put the porous carbon M into a vacuum graphitization furnace for graphitization treatment to obtain a porous graphite material S. The graphitization treatment process is as follows: heat from room temperature to 750 °C at a heating rate of 100 °C / h, heat from 750 °C to 1350 °C at a heating rate of 65 °C / h, heat from 1350 °C to 1600 °C at a heating rate of 40 °C / h, heat from 1600 °C to 1900 °C at a heating rate of 20 °C / h, heat from 1900 °C to 2400 °C at a heating rate of 60 °C / h, and hold for 4 h, then cool naturally.

[0111] Perform microstructure characterization on the obtained porous graphite material, and the SEM image obtained is as shown in the appendix Figure 4 It can be seen that the surface of the sample block is polished flat, and the internal micropore distribution of the material can be directly observed. The pore diameter is between that of Example 1 and Example 2, and the average pore diameter is 40 microns.

[0112] Detect the performance parameters of the porous graphite materials obtained in Examples 1-3, and the results are shown in Table 1:

[0113] Table 1

[0114]

[0115] It can be seen that the size of the average pore diameter is related to the size of the bulking agent particle size. The larger the bulking agent particles, the larger the pore diameter inside the material. The compressive strength and flexural strength of the material are affected by the fineness of the aggregate particles. Reducing the aggregate particles is beneficial to improving the mechanical strength of the material.

[0116] It should be noted that the above are only the preferred embodiments of the present invention, and they should not limit the protection scope of the technical solution of the present invention. Any modifications made by those of ordinary skill in the art to the technical solutions described in the foregoing embodiments and any equivalent replacements of technical features within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a porous graphite material, characterized in that, It includes: (1) Grinding calcined pitch coke to obtain aggregate powder, grinding asphalt to obtain binder, and grinding dry starch to obtain bulking agent; (2) Kneading the aggregate powder with the first part of the binder to obtain the first paste, and kneading the bulking agent with the second part of the binder to obtain the first coating material; (3) Grinding the first paste to obtain the second paste, and grinding the first coating material to obtain the second coating material; (4) Mixing the second paste with the second coating material to obtain pressed powder; (5) Isostatic pressing the pressed powder to obtain a green body; (6) Baking the green body to obtain a porous carbon material; (7) Graphitizing the porous carbon material to obtain a porous graphite material; wherein, the D50 particle size of the aggregate powder is 15μm; the D50 particle size of the binder is 10μm; the D50 particle size of the bulking agent is 25μm; the D50 particle size of the second paste is 55μm; the D50 particle size of the second coating material is 32μm; in the first paste, the mass content ratio of the aggregate powder to the first part of the binder is 55%:45%; in the first coating material, the mass content ratio of the bulking agent to the second part of the binder is 75%:25%; in the pressed powder, the mass content ratio of the second paste to the second coating material is 60%:40%.

2. The preparation method according to claim 1, characterized in that, Wherein, The kneading for obtaining the first paste includes: dry mixing the aggregate powder until the dry mixing temperature reaches above 180°C, then adding the first part of the binder, and performing wet mixing at 220 - 250°C for 1 - 2h, and then cooling to obtain the first paste. The volatile content of the first paste obtained after kneading is 12 - 15%.

3. The preparation method according to claim 1, characterized in that, The kneading for obtaining the first coating material includes: dry mixing the bulking agent until the dry mixing temperature reaches above 220°C, then adding the second part of the binder, and performing wet mixing at 220 - 240°C for 0.5 - 1h, and then cooling to obtain the first coating material.

4. The preparation method according to claim 1, characterized in that The pressure of the isostatic pressing is 130 - 150MPa.

5. The preparation method according to claim 1, characterized in that, The isostatic pressing includes: sealing the pressed powder in a rubber membrane sleeve and evacuating it, and then pressing it with an isostatic press.

6. The preparation method according to claim 1, wherein, The obtaining of the pressed powder includes: adding the second paste and the second coating material into a V-type mixer and mixing for 1 - 1.5h.

7. The preparation method according to claim 1, characterized in that, The baking includes: loading the green body into a baking crucible filled with yellow sand, and then baking it in a baking furnace.

8. The preparation method according to claim 1, wherein The baking includes: under a pressure of 4.0 - 4.5MPa, heating from room temperature to 200°C at a heating rate of 10 - 20°C / h, then heating from 200°C to 350°C at a heating rate of 2 - 4°C / h, then heating from 350°C to 550°C at a heating rate of 3 - 5°C / h, heating from 550°C to 750°C at a heating rate of 6 - 8°C / h, heating from 750°C to 950°C at a heating rate of 8 - 12°C / h, holding at 950°C for 6 - 12h, then cooling from 950°C to 600°C at a cooling rate of 30 - 50°C / h, and then naturally cooling to room temperature.

9. The preparation method according to claim 1, wherein The graphitization treatment includes: heating from room temperature to 750°C at a heating rate of 80 - 120°C / h, heating from 750°C to 1350°C at a heating rate of 50 - 80°C / h, heating from 1350°C to 1600°C at a heating rate of 30 - 50°C / h, heating from 1600°C to 1900°C at a heating rate of 15 - 30°C / h, heating from 1900°C to 2400°C at a heating rate of 50 - 80°C / h, holding for 4 - 6 h, and then naturally cooling down.

10. A porous graphite material prepared by the preparation method according to any one of claims 1 - 9.

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