A porous graphite material, a method for producing the same, and use thereof

Abstract

This invention provides a porous graphite material, its preparation method, and its applications. The preparation method includes the following steps: graphitizing biomass raw materials to obtain a graphite material; and activating the graphite material to create pores, thereby obtaining the porous graphite material. In this invention, after graphitizing the biomass raw materials, a composite graphite material structure with "hard carbon" and graphite microcrystal doping is obtained. Furthermore, the activation pore-forming treatment not only promotes the formation of crystalline carbon and the volatilization of volatiles in the composite graphite material structure but also etches the "hard carbon" regions to remove various disordered carbon and carbon-containing compounds, thus obtaining a porous graphite material with a highly developed pore structure, high specific surface area, and excellent electrical conductivity, making it suitable for various fields.

Description

Technical Field

[0001] This invention belongs to the field of porous carbon materials technology, and relates to a porous graphite material, its preparation method and uses. Background Technology

[0002] Carbon materials, with their excellent heat resistance, high thermal conductivity, good chemical inertness, and high electrical conductivity, are widely used in industries such as machinery, electronics, electrical appliances, aerospace, nuclear energy, metallurgy, and chemicals. From diamond and graphite to traditional carbon black, porous carbon, activated carbon, and high-purity graphite, they play a significant role in industrial production and people's daily lives.

[0003] Among various carbonaceous materials, porous carbon materials have highly developed pore structures, large specific surface areas, excellent adsorption functions, and superior electrical conductivity, and are therefore widely used in many fields such as energy storage and conversion, catalysis, and macromolecular adsorption.

[0004] As is well known, renewable natural biomass resources, due to their abundant carbon content, provide a sufficient source of raw materials for the future development and application of carbon materials. As an inevitable result of metabolism and natural biological competition, biomass often possesses naturally optimized multi-channel structures for the absorption and transport of ions and water, making it suitable for the preparation of porous carbon materials.

[0005] In existing technologies, the methods for obtaining porous carbon materials from biomass raw materials mostly involve adding an activator and then impregnating and calcining at high temperatures to obtain porous carbon materials with ultra-high specific surface area. However, these methods do not improve the conductivity of the carbon materials, and the improvement in the specific surface area and pore volume of the obtained porous carbon materials is also limited.

[0006] Therefore, improving the pore volume, specific surface area, and conductivity of biomass-based porous carbon materials is an urgent research topic. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a porous graphite material, its preparation method, and its applications. In this invention, biomass raw materials are graphitized to obtain a composite graphite material structure doped with "hard carbon" and graphite microcrystals. Further, through activation and pore-forming treatment, not only is the formation of crystalline carbon and the volatilization of volatiles in the composite graphite material structure promoted, but the "hard carbon" regions are also etched to remove various disordered carbon and carbon-containing compounds. This results in a porous graphite material with a highly developed pore structure, high specific surface area, and excellent electrical conductivity, making it suitable for various fields.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a porous graphite material, the method comprising the following steps:

[0010] Graphitization of biomass raw materials yields graphite materials;

[0011] The graphite material is activated and pore-forming to obtain the porous graphite material.

[0012] Biomass is the most widely distributed renewable resource in nature. Its main components are lignin, cellulose, and hemicellulose. For example, it can be at least one of the following: pine sawdust, corn stalks, rice stalks, pine bark, birch bark, ginkgo leaves, corn leaves, coconut shells, walnut shells, rice husks, corn cobs, or cotton.

[0013] In this invention, biomass is used as a raw material for graphitization. During the graphitization process, lignin in biomass is easily graphitized, while cellulose and hemicellulose are relatively difficult to graphitize. Therefore, biomass char easily contains "hard carbon" regions after carbonization, resulting in a composite graphite material doped with "hard carbon" and graphite microcrystals. This composite graphite material, through subsequent activation and pore-forming processes, not only promotes the formation of crystalline carbon and the volatilization of volatiles, but also etches the "hard carbon" regions, removing various disordered carbon and carbon-containing compounds, thus obtaining a porous graphite material with a highly developed pore structure. This not only improves the conductivity of the porous graphite material but also increases its specific surface area and pore volume, enabling better applications in energy storage, catalysis, and adsorption fields. Especially in lithium-ion batteries for energy storage, the porous structure in the graphite material can alleviate graphite expansion after lithium charging, increasing battery safety and lifespan. Furthermore, increased porosity is beneficial for Li... + Li metal is deposited to form, thereby increasing battery capacity.

[0014] The present invention does not require the addition of any other additives during the graphitization process; that is, it can be used to graphitize only biomass raw materials.

[0015] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0016] Preferably, the biomass raw materials are pretreated before graphitization.

[0017] Preferably, the pretreatment includes sequentially crushing, screening, washing, and drying the biomass raw materials.

[0018] In this invention, impurities and discoloration can be effectively removed from biomass raw materials through pretreatment.

[0019] Preferably, the graphitization process includes a first processing stage and a second processing stage performed sequentially.

[0020] In this invention, the first treatment stage is mainly used to remove volatiles from biomass raw materials, which is more conducive to the graphitization transformation of materials in the second treatment stage.

[0021] Preferably, the heating rate of the first processing stage is 1 to 10 °C / min, such as 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min or 10 °C / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] It should be noted that the heating stage of the first processing stage in this invention refers to the temperature rise from room temperature (within the range of 20 to 30°C, for example, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30°C) to the heat preservation temperature of the first processing stage.

[0023] Preferably, the holding temperature after the first processing stage is 900-1600℃, such as 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃ or 1600℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In this invention, the holding temperature after the first treatment stage is 900-1600℃. Within this temperature range, the removal of volatiles from biomass raw materials can be better achieved, which is more conducive to the subsequent graphitization transformation.

[0025] Preferably, the holding time after heating in the first processing stage is 0.5 to 1 hour, such as 0.5 hours or 1 hour, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Preferably, the second processing stage includes raising the temperature from the holding temperature of the first processing stage to the graphitization temperature, and then performing a holding treatment at the graphitization temperature.

[0027] Preferably, the heating rate of the second processing stage is 1.5 to 3 °C / min, such as 1.5 °C / min, 2 °C / min, 2.5 °C / min or 3 °C / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] In this invention, during the process of heating from the first processing stage to the graphitization temperature, the heating rate is controlled to 1.5 to 3 °C / min, which is beneficial to the ordering of the graphite microcrystalline structure of the material and the degree of graphitization is better.

[0029] Preferably, the graphitization temperature is 2600–3000℃, such as 2600℃, 2650℃, 2700℃, 2750℃, 2800℃, 2850℃, 2900℃, 2950℃, or 3000℃, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0030] Preferably, the heat treatment time at the graphitization temperature is 1 to 3 hours, such as 1 hour, 2 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the method for activating pore formation includes physical activation or chemical activation, with physical activation being preferred.

[0032] In this invention, a physical activation method is used to create pores in graphite materials, which is more conducive to the removal of "hard carbon" type carbon materials and to obtaining a richer pore structure.

[0033] Preferably, the activator for physical activation includes steam, which includes carbon dioxide steam and / or water steam, preferably water steam.

[0034] This invention uses water vapor as an activator, which can not only promote the formation of crystalline carbon and the volatilization of volatiles in graphite materials, but also etch the "hard carbon" region to remove various disordered carbon and carbon-containing compounds, thereby forming a rich porous structure.

[0035] Preferably, the activation temperature for physical activation is 700–900°C, such as 700°C, 750°C, 800°C, 850°C, or 900°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0036] Preferably, the physical activation time is 2 to 5 hours, such as 2 hours, 3 hours, 4 hours or 5 hours.

[0037] Preferably, during the physical activation process, the amount of graphite material added is 5 to 10g, such as 5g, 6g, 7g, 8g, 9g or 10g, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, during the physical activation process, the flow rate of the steam activator is 1 to 5 mL / min, such as 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min or 5 mL / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] As a preferred technical solution, the preparation method includes the following steps:

[0040] The biomass raw material is heated to 900-1600℃ at a heating rate of 1-10℃ / min and then kept at that temperature for 0.5-1h to complete the first treatment stage.

[0041] Then, the temperature is increased from the holding temperature of 900-1600℃ to the graphitization temperature of 2600-3000℃ at a heating rate of 1.5-3℃ / min, and held for 1-3 hours to complete the second treatment stage and obtain graphite material.

[0042] Graphite material is added to a steam system with a flow rate of 1–5 mL / min and a temperature of 700–900 °C for activation and pore-forming treatment for 2–5 h to obtain porous graphite material.

[0043] It should also be noted that the atmosphere in the graphitization process of the present invention is a conventional carbonization atmosphere, i.e., a protective atmosphere, such as a nitrogen atmosphere and / or an inert gas atmosphere, wherein the inert gas includes argon or helium, etc.

[0044] In a second aspect, the present invention provides a porous graphite material, which is prepared by the preparation method described in the first aspect; the porous graphite material has a porous structure both inside and on the surface.

[0045] The porous graphite material provided by this invention has a well-developed pore structure, a high specific surface area, and excellent electrical conductivity.

[0046] Preferably, the pore size distribution of the porous graphite material is 2 to 5 nm. For example, the endpoint values ​​of the pore volume distribution data range can be 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm, etc., but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the pore volume of the porous graphite material is 0.6–1.0 cm³. 3 / g, for example, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0048] Preferably, the specific surface area of ​​the porous graphite material is ≥800 m². 2 / g, for example 800m 2 / g、810m 2 / g、820m 2 / g、830m 2 / g、840m 2 / g、850m 2 / g、860m 2 / g、870m 2 / g、880m 2 / g、890m 2 / g、900m 2 / g、925m 2 / g、950m 2 / g、975m 2 / g or 1000m 2 / g, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0049] Thirdly, the present invention also provides an use of the porous graphite material as described in the second aspect, the use including using the porous graphite material in the fields of energy storage, catalysis or adsorption.

[0050] The porous graphite material provided by this invention can be used in a variety of fields.

[0051] When porous graphite materials are used in the field of energy storage, they can be used in electrochemical devices, such as new energy batteries, supercapacitors, or chemical sensors; new energy batteries include, but are not limited to, lithium-ion batteries or sodium-ion batteries.

[0052] When the porous graphite material provided by this invention is used in lithium-ion batteries, it can serve as a negative electrode active material for the preparation of the battery's negative electrode sheet. The porous structure can alleviate graphite expansion after lithium charging, increasing battery safety and lifespan. Simultaneously, the increased porosity is beneficial for Li... + Li metal is deposited, thereby increasing the battery capacity.

[0053] When porous graphite materials are used in the field of catalysts, they can serve as catalyst supports and synergistically carry out catalytic reactions with active components.

[0054] When porous graphite materials are used in the field of adsorption, they are used directly as adsorbents.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] In this invention, biomass is used as a raw material for graphitization. During the graphitization process, lignin in biomass is easily graphitized, while cellulose and hemicellulose are relatively difficult to graphitize. Therefore, biomass char easily contains "hard carbon" regions after carbonization, resulting in a composite graphite material doped with "hard carbon" and graphite microcrystals. This composite graphite material, through subsequent activation and pore-forming processes, not only promotes the formation of crystalline carbon and the volatilization of volatiles, but also etches the "hard carbon" regions, removing various disordered carbon and carbon-containing compounds, thus obtaining a porous graphite material with a highly developed pore structure. This not only improves the conductivity of the porous graphite material but also increases its specific surface area and pore volume, enabling better applications in energy storage, catalysis, and adsorption fields. Especially in lithium-ion batteries for energy storage, the porous structure in the graphite material can alleviate graphite expansion after lithium charging, increasing battery safety and lifespan. Furthermore, increased porosity is beneficial for Li... + Li metal is deposited to form, thereby increasing battery capacity. Detailed Implementation

[0057] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms “comprising” and “having” and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0059] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0060] Example 1

[0061] This embodiment provides a porous graphite material, and the preparation method of the porous graphite material is as follows:

[0062] Using coconut shells as biomass raw material, the coconut shells are washed, crushed, and sieved to separate particles with a diameter of less than 40 mesh. After being repeatedly rinsed with clean water and filtered, the coconut shells are dried overnight in an oven at 100°C to obtain dried coconut shell powder.

[0063] Subsequently, the coconut shell powder was placed in a graphitization furnace for the first treatment stage, which included heating from room temperature to 1600°C at a heating rate of 5°C / min, and then holding at that temperature for 30 min.

[0064] After the first treatment stage is completed, the second treatment stage is carried out. The second treatment stage includes: continuing to heat from 1600℃ to the graphitization temperature of 3000℃ at a heating rate of 2℃ / min, holding at the temperature for 2 hours, and then cooling to room temperature to obtain graphite material.

[0065] Then, 10g of graphite material was placed in a tube furnace, and N2 was introduced at 0.2mL / min. After 30min, the temperature was increased to the activation temperature of 700℃ at 5℃ / min. Then, water vapor was introduced for activation at a flow rate of 1mL / min for 2h. Finally, the temperature was lowered to room temperature to obtain porous graphite material with pores on both the interior and surface.

[0066] Example 2

[0067] This embodiment provides a porous graphite material, and the preparation method of the porous graphite material is as follows:

[0068] Using coconut shells as biomass raw material, the coconut shells are washed, crushed, and sieved to separate particles with a diameter of less than 40 mesh. After being repeatedly rinsed with clean water and filtered, the coconut shells are dried overnight in an oven at 100°C to obtain dried coconut shell powder.

[0069] Subsequently, the coconut shell powder was placed in a graphitization furnace for the first treatment stage, which included: heating to 900°C at a rate of 5°C / min and then holding at that temperature for 1.5 hours.

[0070] After the first treatment stage is completed, the second treatment stage is carried out. The second treatment stage includes: continuing to heat from 900℃ to the graphitization temperature of 2600℃ at a heating rate of 1.5℃ / min, holding at the temperature for 3 hours, and then cooling to room temperature to obtain graphite material.

[0071] Then, 10g of graphite material was placed in a tube furnace, and N2 was introduced at 0.2mL / min. After 30min, the temperature was increased to the activation temperature of 900℃ at 5℃ / min. Then, water vapor was introduced for activation at a flow rate of 5mL / min for 5h. Finally, the temperature was lowered to room temperature to obtain porous graphite material with pores on both the interior and surface.

[0072] Example 3

[0073] This embodiment provides a porous graphite material, and the preparation method of the porous graphite material is as follows:

[0074] Using coconut shells as biomass raw material, the coconut shells are washed, crushed, and sieved to separate particles with a diameter of less than 40 mesh. After being repeatedly rinsed with clean water and filtered, the coconut shells are dried overnight in an oven at 100°C to obtain dried coconut shell powder.

[0075] Subsequently, the coconut shell powder was placed in a graphitization furnace for the first treatment stage, which included: heating to 1200℃ at a rate of 10℃ / min and then holding at that temperature for 1 hour.

[0076] After the first treatment stage is completed, the second treatment stage is carried out. The second treatment stage includes: continuing to heat from 1200℃ to the graphitization temperature of 2800℃ at a heating rate of 3℃ / min, holding at the temperature for 1 hour, and then cooling to room temperature to obtain graphite material.

[0077] Then, 10g of graphite material was placed in a tube furnace, and N2 was introduced at 0.2mL / min. After 30min, the temperature was increased to the activation temperature of 800℃ at 10℃ / min. Then, water vapor was introduced for activation at a flow rate of 3mL / min for 3h. Finally, the temperature was lowered to room temperature to obtain porous graphite material with pores on both the interior and surface.

[0078] Example 4

[0079] The difference between this embodiment and Embodiment 1 is that the biomass raw material in this embodiment is corn cob.

[0080] The remaining preparation methods and parameters are consistent with those in Example 1.

[0081] Example 5

[0082] The difference between this embodiment and Embodiment 1 is that in this embodiment, the temperature is directly increased from room temperature to the graphitization temperature of 3000℃ at a heating rate of 2℃ / min, that is, the first treatment stage is not performed.

[0083] The remaining preparation methods and parameters are consistent with those in Example 1.

[0084] Example 6

[0085] The difference between this embodiment and Embodiment 1 is that the heating rate in the second processing stage of this embodiment is 5℃ / min.

[0086] The remaining preparation methods and parameters are consistent with those in Example 1.

[0087] Example 7

[0088] The difference between this embodiment and Embodiment 1 is that the activator in the activation process of this embodiment is carbon dioxide vapor.

[0089] The remaining preparation methods and parameters are consistent with those in Example 1.

[0090] Example 8

[0091] The difference between this embodiment and Embodiment 1 is that the water vapor is added at a flow rate of 0.5 mL / min in this embodiment.

[0092] The remaining preparation methods and parameters are consistent with those in Example 1.

[0093] Example 9

[0094] The difference between this embodiment and Embodiment 1 is that the water vapor is added at a flow rate of 6 mL / min in this embodiment.

[0095] The remaining preparation methods and parameters are consistent with those in Example 1.

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 1 is that the porous carbon material obtained in this comparative example is a non-graphite material.

[0098] In the preparation method, the graphitization temperature is not reached. Instead, the coconut shell powder is placed in a graphitization furnace for the first treatment stage. The first treatment stage includes heating from room temperature to 1600℃ at a heating rate of 5℃ / min, and then holding at that temperature for 30min to obtain the material to be activated.

[0099] The remaining preparation methods and parameters are consistent with those in Example 1.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 1 is that after obtaining the graphite material, this comparative example does not undergo subsequent activation and pore-forming treatment.

[0102] The remaining preparation methods and parameters are consistent with those in Example 1.

[0103] The porous graphite materials (or porous carbon materials) obtained in Examples 1-9 and Comparative Examples 1-2 were tested for graphite yield, pore structure, specific surface area and tap density.

[0104] Graphite material yield: (Output mass / Feed mass) × 100%.

[0105] Pore ​​structure and specific surface area: The adsorption and desorption performance of porous carbon materials were tested according to GB / T 19587-2004. The adsorption medium was N2, and the pore volume, pore size distribution and specific surface area were calculated using the accompanying software.

[0106] Tap density: Tested using a BT-302 tap density meter at 250 times / min for 1000 vibrations.

[0107] The test results are shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111] The porous graphite materials (or porous carbon materials) provided in Examples 1-9 and Comparative Examples 1-2 were used to prepare batteries and test their performance.

[0112] (I) Battery fabrication:

[0113] The porous graphite materials (or porous carbon materials) obtained in Examples 1-9 and Comparative Examples 1-2 were used as negative electrode active materials, respectively. They were mixed at a mass ratio of negative electrode active material:PVDF:SP = 91.6:6.6:1.8, and the mixture was coated onto copper foil using NMP as a solvent. The coating surface density was 6.5 ± 0.1 mg / cm³. 2 After vacuum drying at 90℃, a negative electrode sheet is obtained. The negative electrode sheet is then rolled to a compaction density of 1.65±0.02g / cc. The copper foil is cut into round pieces with a diameter of 14mm using a cutting machine to obtain the negative electrode sheet. A lithium sheet is used as the counter electrode.

[0114] The negative electrode, lithium sheet, electrolyte (0.8 mol / L LiPF6, EC:DMC volume ratio of 1:1) and Celgard 2400 separator are assembled into a coin cell.

[0115] (II) Performance Testing:

[0116] The lithium-ion batteries provided in Examples 1-9 and Comparative Examples 1-2 were tested for capacity and first-efficiency.

[0117] Capacity: The obtained batteries were subjected to constant current charge and discharge tests using Blue Electric testing equipment at 25±2℃. The discharge cutoff voltage was 0.01V and the charge cutoff voltage was 2.5V. The first week of charge and discharge tests were conducted at a current density of 0.1C, and the corresponding charge specific capacity was recorded.

[0118] First-time efficiency: The obtained battery was subjected to constant current charge-discharge testing using a Blue Electric testing device at 25±2℃. The discharge cutoff voltage was 0.01V, and the charge cutoff voltage was 2.5V. The first week of charge-discharge testing was conducted at a current density of 0.1C, and the corresponding charge specific capacity and first-time efficiency were recorded. First-time efficiency = (First charge capacity / First discharge capacity) × 100%.

[0119] The test results are shown in Table 2.

[0120] Table 2

[0121] Capacity (mAh / g) First-efficacy (%) Example 1 430 92.7 Example 2 520 71.6 Example 3 483 89.7 Example 4 442 88.5 Example 5 390 82.0 Example 6 547 62.6 Example 7 382 91.5 Example 8 305 89.6 Example 9 470 68.8 Comparative Example 1 320 52.4 Comparative Example 2 285 88.5

[0122] In summary, this invention involves graphitizing biomass raw materials. During graphitization, lignin in the biomass raw materials is easily graphitized, while cellulose and hemicellulose are relatively more difficult to graphitize. Therefore, biomass char easily contains "hard carbon" regions after carbonization, resulting in a composite graphite material doped with "hard carbon" and graphite microcrystals. This composite graphite material, through subsequent activation and pore-forming processes, not only promotes the formation of crystalline carbon and the volatilization of volatiles, but also etches the "hard carbon" regions, removing various disordered carbon and carbon-containing compounds, thus obtaining a porous graphite material with a highly developed pore structure. This not only improves the conductivity of the porous graphite material but also increases its specific surface area and pore volume, enabling better applications in energy storage, catalysis, and adsorption fields. Especially when used in lithium-ion batteries for energy storage, the porous structure in the graphite material can alleviate graphite expansion, increasing battery safety and lifespan. Simultaneously, increased porosity is beneficial for Li... + Li metal is deposited to form, thereby increasing the battery capacity and resulting in a high-capacity battery.

[0123] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a porous graphite material, characterized in that, The preparation method includes the following steps: Graphitization of biomass raw materials yields graphite materials; The graphite material is activated and pore-forming to obtain the porous graphite material.

2. The preparation method according to claim 1, characterized in that, The biomass raw materials are pretreated before graphitization. Preferably, the pretreatment includes sequentially crushing, screening, washing, and drying the biomass raw materials.

3. The preparation method according to claim 1, characterized in that, The graphitization process includes a first processing stage and a second processing stage performed sequentially.

4. The preparation method according to claim 3, characterized in that, The heating rate of the first treatment stage is 1 to 10 °C / min, the holding temperature after the heating in the first treatment stage is 900 to 1600 °C, and the holding time after the heating in the first treatment stage is 0.5 to 1 h. Preferably, the second processing stage includes raising the temperature from the holding temperature of the first processing stage to the graphitization temperature, and then performing a holding treatment at the graphitization temperature. Preferably, the heating rate in the second processing stage is 1.5–3 °C / min; Preferably, the graphitization temperature is 2600–3000℃, and the heat treatment time at the graphitization temperature is 1–3 hours.

5. The preparation method according to claim 1, characterized in that, The method for activating pore formation includes physical activation or chemical activation, with physical activation being preferred. Preferably, the activator for physical activation includes steam, which includes carbon dioxide vapor and / or water vapor, preferably water vapor; Preferably, the activation temperature of the physical activation is 700–900°C, and the activation time of the physical activation is 2–5 hours. Preferably, during the physical activation process, the amount of graphite material added is 5-10g; Preferably, during the physical activation process, the flow rate of the steam activator is 1–5 mL / min.

6. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: The biomass raw material is heated to 900-1600℃ at a heating rate of 1-10℃ / min and then kept at that temperature for 0.5-1h to complete the first treatment stage. Then, the temperature is increased from the holding temperature of 900-1600℃ to the graphitization temperature of 2600-3000℃ at a heating rate of 1.5-3℃ / min, and held for 1-3 hours to complete the second treatment stage and obtain graphite material. Graphite material is added to a steam system with a flow rate of 1–5 mL / min and a temperature of 700–900 °C for activation and pore-forming treatment for 2–5 h to obtain porous graphite material.

7. A porous graphite material, characterized in that, The porous graphite material is prepared by the preparation method according to any one of claims 1-6; the porous graphite material has a porous structure both inside and on the surface.

8. The porous graphite material according to claim 7, characterized in that, The porous graphite material has a pore size distribution of 2–5 nm; Preferably, the porous graphite material has a pore volume of 0.6 to 1.0 cm 3 / g.

9. The porous graphite material according to claim 7 or 8, characterized in that, The specific surface area of ​​the porous graphite material is ≥800 m². 2 / g.

10. The use of the porous graphite material as described in any one of claims 7-9, characterized in that, The applications include using the porous graphite material in the fields of energy storage, catalysis, or adsorption.

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