Preparation method for carbonaceous material, carbonaceous material and use

Abstract

The present disclosure relates to the technical field of carbon materials, and particularly relates to a preparation method for a carbonaceous material, the carbonaceous material and a use. A carbonized material formed by a biomass material is sintered at a high temperature in a chlorodifluoromethane atmosphere, and in this process, chlorodifluoromethane is decomposed to generate tetrafluoroethene and hydrogen chloride gas, tetrafluoroethylene can generate octafluorocyclobutane, and octafluorocyclobutane can react with silicon dioxide to generate silicon tetrafluoride, carbon dioxide and carbon; and the generated hydrogen chloride gas can react with metal impurities at a high temperature to generate metal chloride. By means of the preparation method provided by the present disclosure, metal impurities such as iron and calcium can be removed while silicon dioxide is removed, acid pickling and alkali washing processes are not needed, and waste liquid treatment is not involved.

Description

Preparation method of carbonaceous material, carbonaceous material and application thereof Technical Field

[0001] The present disclosure belongs to the technical field of carbon materials, and in particular relates to a preparation method of a carbonaceous material, a carbonaceous material and an application thereof. Background Art

[0002] Lithium-ion batteries, with their high energy density, high efficiency, and light weight, have been widely used in portable electronic devices. However, the scarcity and uneven distribution of lithium resources on Earth make lithium-ion batteries relatively expensive for future energy storage systems, especially in large-scale energy storage applications. Sodium-ion batteries, as an ideal alternative to lithium-ion batteries, have attracted widespread attention due to their abundant sodium reserves and similar electrochemical mechanisms to lithium-ion batteries. However, because the radius of sodium ions is 55% larger than that of lithium ions, commercial graphite anodes cannot reversibly insert and extract sodium ions, posing a significant challenge to the development of sodium-ion batteries.

[0003] To this end, researchers have conducted extensive research in an effort to identify promising sodium-ion battery anode materials. Currently developed sodium-ion battery anode materials primarily include titanium-based oxides, transition metal borates, metal sulfides, carbon materials, and their composites. Among these, carbonaceous materials have attracted considerable attention due to their low preparation cost, highly tunable physicochemical structure, and low pollution. Among these carbonaceous materials, hard carbon, due to its unique structure of long-range disorder and short-range order, exhibits high reversible capacity and good cycling stability at low operating voltages, making it an extremely attractive anode material for sodium-ion batteries.

[0004] The raw materials of hard carbon mainly include biomass materials, minerals and artificial organic matter. Among them, rice husk, as a biomass material, has the advantages of wide availability and low price, which can realize the preparation of low-cost hard carbon negative electrode. However, due to the high silica content in rice husk (about 15wt%-20wt%), it will affect the capacity and initial efficiency of hard carbon, and it is often necessary to remove silicon from it. At present, silicon dioxide in rice husk is generally removed by hydrofluoric acid or alkaline washing. These desiliconization methods all involve waste liquid treatment, and the yield of the obtained hard carbon is low, which greatly increases the production cost.

[0005] Therefore, there is an urgent need to develop an economical and environmentally friendly silicon removal method to promote the industrial application of biomass rice husk-based hard carbon.

[0006] In view of this, the present disclosure is proposed.

[0007] Summary of the Invention

[0008] The purpose of the present disclosure includes providing a preparation method of a carbonaceous material, a carbonaceous material and its application, aiming to provide a more economical and environmentally friendly method while achieving the removal of silicon dioxide and metal impurities.

[0009] In order to achieve the above-mentioned purpose of the present disclosure, the following technical solutions can be adopted:

[0010] In a first aspect, the solution provided by the present disclosure includes a method for preparing a carbonaceous material, comprising: sintering a carbonized material formed from a biomass material at a high temperature in a difluorochloromethane atmosphere;

[0011] The sintering temperature of the high temperature sintering is 1000°C-1500°C.

[0012] In some embodiments of the present disclosure, the sintering temperature of the high temperature sintering is 1100°C-1300°C.

[0013] In some embodiments of the present disclosure, the sintering time of high temperature sintering is 2 hours to 6 hours.

[0014] In some embodiments of the present disclosure, the sintering time of high temperature sintering is 3 hours to 5 hours.

[0015] In some embodiments of the present disclosure, the flow rate of chlorodifluoromethane per 100 g of carbonized material is 1 L / min-3 L / min.

[0016] In some embodiments of the present disclosure, the preparation process of the carbonized material includes: pre-carbonizing the biomass material, mixing it with an organic carbon source and an organic solvent to obtain a mixture, and drying the mixture to form an in-situ coating of the organic carbon source.

[0017] In some embodiments of the present disclosure, the biomass material is rice husk.

[0018] In some embodiments of the present disclosure, the carbonization temperature of the pre-carbonization is 500° C.-700° C., and the carbonization time is 1 hour-4 hours.

[0019] In some embodiments of the present disclosure, pre-carbonization is performed under an inert atmosphere.

[0020] In some embodiments of the present disclosure, the organic carbon source is selected from at least one of phenolic resin, sucrose, and glucose.

[0021] In some embodiments of the present disclosure, the organic carbon source is a phenolic resin.

[0022] In some embodiments of the present disclosure, the mass ratio of the pre-carbonized material to the organic carbon source is (3-7):1.

[0023] In some embodiments of the present disclosure, the mass ratio of the total amount of the pre-carbonized material and the organic carbon source to the organic solvent is (0.8-1.0):1.

[0024] In some embodiments of the present disclosure, the organic solvent is selected from at least one of ethanol, methanol, isopropanol, and acetone.

[0025] In some embodiments of the present disclosure, during the drying of the mixed material, the drying temperature is controlled to be 80° C.-100° C., and the drying time is controlled to be 20 h-30 h.

[0026] In some embodiments of the present disclosure, after pre-carbonization is completed, ball milling is performed to obtain a powdered material, and then the powdered material is mixed with an organic carbon source and an organic solvent, and the Dv50 of the powdered material is 4 μm-6 μm.

[0027] In some embodiments of the present disclosure, the ball mill speed is controlled to be 450 r / min-600 r / min, the ball-to-material ratio is 8-12:1, and the ball milling time is 3 h-8 h.

[0028] In some embodiments of the present disclosure, after high-temperature sintering, the obtained sintered material is sequentially subjected to water washing to remove impurities and high-temperature carbonization.

[0029] In some embodiments of the present disclosure, the carbonization temperature of the high-temperature carbonization is 1300° C.-1700° C., and the carbonization time is 8 h-12 h.

[0030] In some embodiments of the present disclosure, high-temperature carbonization is performed under an inert atmosphere.

[0031] In some embodiments of the present disclosure, water washing and impurity removal includes water washing, solid-liquid separation and drying performed in sequence.

[0032] In a second aspect, the solution provided by the present disclosure also includes a carbonaceous material prepared by the preparation method in any of the above embodiments.

[0033] In some embodiments of the present disclosure, the carbonaceous material is hard carbon.

[0034] In some embodiments of the present disclosure, the specific surface area of ​​the carbonaceous material is 0.9 m 2 / g-2.0m 2 / g, true density is 1.702g / cm 3 -1.825g / cm 3 .

[0035] In a third aspect, the solution provided by the present disclosure also includes a negative electrode sheet, which is prepared using the carbonaceous material in any of the above embodiments as the negative electrode active material.

[0036] In a fourth aspect, the solution provided by the present disclosure also includes a sodium ion battery, comprising the negative electrode plate in the above embodiment.

[0037] In a fifth aspect, the solution provided by the present disclosure also includes an electrical device, including the sodium ion battery in the above embodiment.

[0038] The carbonized material formed from biomass is sintered at high temperature in a difluorochloromethane atmosphere. During this process, the difluorochloromethane decomposes to produce tetrafluoroethylene gas and hydrogen chloride gas. The tetrafluoroethylene, in turn, produces octafluorocyclobutane, which reacts with silicon dioxide to produce silicon tetrafluoride, carbon dioxide, and carbon. The resulting hydrogen chloride gas reacts with metal impurities at high temperatures to produce metal chlorides. The preparation method provided by this disclosure can remove metal impurities such as iron and calcium while removing silicon dioxide, without the need for acid and alkali washing processes and waste liquid disposal.

[0039] In addition, the present invention discloses a method for reacting octafluorocyclobutane produced by the decomposition product of difluorochloromethane with silicon dioxide to generate silicon tetrafluoride gas, carbon dioxide gas, and carbon. While removing silicon dioxide, carbon can also be deposited, thereby improving the yield of the product and reducing costs. The deposited carbon reduces the pore size inside the material, converting the mesopores into micropores. Such micropores not only provide sufficient sodium storage sites, but also help reduce the charge transfer impedance, thereby improving the electrochemical performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0041] FIG1 is a flow chart of the impurity removal step in the preparation method provided by the present disclosure;

[0042] FIG2 is an overall process flow chart of the preparation method provided by the present disclosure;

[0043] FIG3 is an XRD diagram of the rice husk carbonized material obtained after the rice husk raw material is burned;

[0044] FIG4 is an XRD pattern of the sample obtained after the rice husk carbonized material was sintered at high temperature in a difluorochloromethane atmosphere, washed with water, filtered, and dried in Example 1 of the present disclosure;

[0045] FIG5 is an XRD diagram of the sample obtained after alkali washing, water washing, filtration and drying of the rice husk carbonized material in Comparative Example 1 of the present disclosure. DETAILED DESCRIPTION

[0046] The embodiments of the present disclosure will be described in detail below with reference to the examples. However, those skilled in the art will appreciate that the following examples are intended only to illustrate the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, the experiments were performed under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0047] The endpoints of the ranges and any values ​​disclosed in this disclosure are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0048] The present disclosure provides a method for preparing a carbonaceous material. Referring to FIG. 1 , the method includes sintering a carbonized material formed from a biomass material at a high temperature in a difluorochloromethane atmosphere.

[0049] It should be noted that during the sintering process, difluorochloromethane decomposes to produce tetrafluoroethylene gas and hydrogen chloride gas. Tetrafluoroethylene in turn produces octafluorocyclobutane, which reacts with silicon dioxide to produce silicon tetrafluoride, carbon dioxide, and carbon, thereby removing silicon dioxide and simultaneously depositing carbon. In addition, the generated hydrogen chloride gas reacts with metal impurities (such as iron and calcium) at high temperatures to produce metal chlorides. Most of the generated metal chlorides are converted into gas and discharged. Some metal chlorides with higher boiling points can also be separated from the carbon material by water washing, eliminating the need for an acid washing process and obtaining a low-ash carbon material through a one-step sintering process.

[0050] Specifically, referring to FIG. 2 , the present disclosure provides a method for preparing a carbonaceous material, which may include the following steps:

[0051] S1. Pre-carbonization

[0052] The biomass material is pre-carbonized to obtain a carbonized primary material. The biomass material may be, but is not limited to, rice husk.

[0053] Specifically, rice husk is a commercially available product. Rice husk refers to the outer shell of rice grains and is rich in cellulose, lignin, and silica, while having low fat and protein content. During the pre-carbonization process, the cellulose, hemicellulose, and lignin in the rice husk decompose, resulting in the carbonized rice husk material.

[0054] In some embodiments, the carbonization temperature of the pre-carbonization is 500° C. to 700° C., and the carbonization time is 1 hour to 4 hours to fully decompose cellulose, hemicellulose, and lignin. Specifically, the carbonization temperature of the pre-carbonization can be 500° C., 550° C., 600° C., 650° C., 700° C., etc., and the carbonization time can be 1 hour, 2 hours, 3 hours, 4 hours, etc.

[0055] In some embodiments, the pre-carbonization is performed under an inert atmosphere to prevent interference from oxygen. The inert atmosphere may be nitrogen, argon, etc., and may be performed in a box furnace.

[0056] S2, ball milling

[0057] After the pre-carbonization is completed, the carbonized raw material is ball-milled to obtain a powder material. The Dv50 of the powder material is 4 μm-6 μm, such as 4 μm, 5 μm, 6 μm, etc.

[0058] In some embodiments, the ball mill speed is controlled to be 450 r / min-600 r / min, the ball-to-material ratio is 8-12:1, and the ball milling time is 3 h-8 h. By precisely controlling the operating parameters of the ball mill, the particle size of the powdered material meets the requirements.

[0059] Specifically, the ball mill can be a planetary ball mill, and the ball mill speed can be controlled to 450r / min, 500r / min, 550r / min, 600r / min, etc.; the ball-to-material ratio can be 8:1, 9:1, 10:1, 11:1, 12:1, etc., and the ball milling time can be 3h, 4h, 5h, 6h, 7h, 8h, etc.

[0060] S3, carbon coating

[0061] A powdered material is mixed with an organic carbon source and an organic solvent to form a mixture. During the mixing and stirring process, the organic carbon source dissolves in the organic solvent and adheres to the surface of the rice husk carbonized material along with the organic solvent. The mixture is dried. During the drying process, the organic solvent evaporates, while the organic carbon source in the organic solvent precipitates and in-situ coats the surface of the powdered material, resulting in a carbonized material with a carbon coating layer.

[0062] In some embodiments, the organic carbon source is selected from at least one of phenolic resin, sucrose, and glucose, and may be any one or more of the above, preferably phenolic resin. Carbon coating with phenolic resin can further improve the electrochemical performance of the resulting carbon material.

[0063] In some embodiments, the mass ratio of the pre-carbonized material (or the powdered material obtained in S2) to the organic carbon source is (3-7):1. By controlling the amount of the organic carbon source, the final product can have better electrochemical performance. Specifically, the mass ratio of the pre-carbonized material (or the powdered material obtained in S2) to the organic carbon source can be 3:1, 4:1, 5:1, 6:1, 7:1, etc.

[0064] Furthermore, the amount of organic solvent used is not limited, as long as it can fully dissolve the organic carbon source. Generally, the organic solvent needs to cover the solid material after addition. In some embodiments, the mass ratio of the total amount of the pre-carbonized material and the organic carbon source to the organic solvent is (0.8-1.0):1, such as 0.8:1, 0.9:1, 1.0:1, etc.

[0065] In some embodiments, the organic solvent is selected from at least one of ethanol, methanol, isopropanol and acetone, and may be any one or more of the above, preferably ethanol.

[0066] In some embodiments, during the drying process of the mixed material, the drying temperature is controlled to be 80° C.-100° C. and the drying time is controlled to be 20 hours-30 hours to fully volatilize the organic solvent and form a uniform carbon coating layer. Specifically, the drying temperature can be 80° C., 85° C., 90° C., 95° C., 100° C., etc., and the drying time can be 20 hours, 23 hours, 25 hours, 27 hours, 30 hours, etc.

[0067] S4, high temperature sintering

[0068] The carbonized material formed from the biomass material is sintered at a high temperature in a difluorochloromethane atmosphere. The carbonized material may be the carbonized material with the coating layer obtained in S3 or the material obtained after only pre-carbonization.

[0069] Among them, the sintering temperature of high-temperature sintering is 1000℃-1500℃, preferably 1100℃-1300℃; the sintering time of high-temperature sintering is 2h-6h, preferably 3h-5h. The decomposition temperature of difluorochloromethane is lower than the above temperature, and difluorochloromethane can be quickly decomposed at a higher temperature; the reaction of octafluorocyclobutane produced after decomposition with silica is a gas-solid reaction, which needs to be controlled within the above range. Compared with the methods of directly removing silica such as alkali solution and HF acid, the method provided by the present disclosure not only removes silica but also carries out carbon deposition, which can improve the yield of the product and thus reduce production costs.

[0070] Specifically, the carbonized material is placed in a graphite crucible and placed in a box furnace for high-temperature sintering. The sintering temperature can be controlled to be 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, etc., and the sintering time can be 2h, 3h, 4h, 5h, 6h, etc.

[0071] In some embodiments, the flow rate of difluorochloromethane per 100 g of carbonized material is 1 L / min-3 L / min (e.g., 1.0 L / min, 1.5 L / min, 2.0 L / min, 2.5 L / min, 3.0 L / min, etc.), and the amount of difluorochloromethane is controlled to allow the silica to react fully.

[0072] It should be added that compared with the method of removing silica with alkaline solution, the gas-solid reaction method provided by the present disclosure is carried out under high temperature conditions, so its reaction rate is faster and the silicon removal effect is better. In addition, the reaction products generated are all gases except carbon, and no wastewater treatment is involved, so it is more green and environmentally friendly.

[0073] S5, water washing and impurity removal

[0074] After high-temperature sintering, the obtained sintered material is washed with water to remove impurities, so as to remove metal chlorides that cannot be volatilized under high-temperature conditions.

[0075] In some embodiments, water washing and impurity removal includes sequentially performing water washing, solid-liquid separation, and drying to obtain a low-ash sample. Water washing can be performed multiple times with pure water, such as three or more times. Solid-liquid separation can be performed by suction filtration, which is convenient and allows the metal chloride to be fully dissolved and filtered along with the pure water. After solid-liquid separation, the resulting solid material is dried at any temperature, as long as sufficient moisture is removed. The drying temperature can be 80°C-100°C, and the drying time can be 20-30 hours.

[0076] S6, high temperature carbonization

[0077] The low-ash sample obtained in step S5 is carbonized at high temperature to prepare a hard carbon material.

[0078] In some embodiments, the carbonization temperature of the high-temperature carbonization is 1300° C. to 1700° C., and the carbonization time is 8 hours to 12 hours to fully carbonize the material. Specifically, the carbonization temperature of the high-temperature carbonization can be 1300° C., 1400° C., 1500° C., 1600° C., 1700° C., etc., and the carbonization time can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc.

[0079] In some embodiments, the high-temperature carbonization is performed under an inert atmosphere to prevent oxygen from affecting the carbonization process. The inert gas may be, but is not limited to, nitrogen, argon, etc.

[0080] The embodiments of the present disclosure also provide a carbonaceous material prepared by the above-mentioned preparation method. The prepared carbonaceous material has a low impurity content. Since carbon deposition is performed during the impurity removal process, the deposited carbon reduces the pore size inside the material, converting the mesopores into micropores. While providing sufficient sodium storage sites, such micropores are also beneficial to reducing the charge transfer impedance, thereby improving the electrochemical performance of the material.

[0081] In some embodiments, the carbonaceous material is hard carbon, and the hard carbon negative electrode material is obtained after high-temperature carbonization in S6.

[0082] In some embodiments, the specific surface area of ​​the carbonaceous material is 0.9 m 2 / g-2.0m 2 / g, true density is 1.702g / cm 3 -1.825g / cm 3 During the preparation process of the carbonaceous material provided by the present disclosure, the surface of the carbonized material is coated with an organic carbon source such as a phenolic resin, and then the silicon dioxide in the inner layer material is removed by a gas-solid reaction during high-temperature sintering to obtain a negative electrode material with a large internal pore volume. This negative electrode material has a low specific surface area but contains a large number of internal pores as active sites for sodium storage, thereby exhibiting excellent first efficiency and capacity performance.

[0083] The present disclosure also provides a negative electrode sheet, which is prepared using the carbonaceous material described in any of the above embodiments as the negative electrode active material. The negative electrode sheet is obtained by mixing the negative electrode active material with an organic binder, a conductive agent, and other raw materials to obtain a negative electrode slurry, and then applying the negative electrode slurry to a negative electrode current collector to form a coating. Due to the improved performance of the negative electrode active material, the performance of the negative electrode sheet is improved.

[0084] The embodiments of the present disclosure also provide a sodium ion battery, which includes the negative electrode plate in the above embodiment and may also include a positive electrode plate, an electrolyte, a separator, etc. to form a complete sodium ion battery.

[0085] The embodiments of the present disclosure further provide an electrical device, including the sodium ion battery in the above embodiment, and may also include an electrical appliance, wherein the sodium ion battery is used to power the electrical appliance, and the specific type of the electrical appliance is not limited.

[0086] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0087] Example 1

[0088] This embodiment provides a method for preparing a carbonaceous material, comprising the following steps:

[0089] (1) The rice husk raw material (brand: Shijiazhuang Guangchuan, product number: 0309, type: DDGS feed) was heated to 600°C in a box furnace under a nitrogen atmosphere and kept warm for 2 hours to obtain the rice husk carbonized material.

[0090] The XRD pattern of the rice husk carbonized material is shown in Figure 3. As can be seen from Figure 3, the rice husk carbonized material contains a large amount of SiO2. The JCPDS No. 01-085-0797 in the figure represents the standard card of SiO2.

[0091] (2) The rice husk carbonized material obtained in step (1) was ball-milled using a planetary ball mill at a ball mill speed of 520 r / min, a ball-to-material ratio of 10:1, and a ball milling time of 5 h to obtain a powdered rice husk carbonized material.

[0092] (3) The powdered rice husk carbonized material obtained in step (2) and phenolic resin were added to a beaker at a mass ratio of 5:1. Alcohol was added to the beaker until the alcohol covered the mixture. The mass ratio of the total amount of the powdered rice husk carbonized material and phenolic resin to the alcohol was controlled to be 0.9:1. The mixture was then stirred using a blender. After stirring for 1 hour, the beaker containing the mixture and alcohol was placed in a drying oven to dry to obtain a coated sample. The drying temperature was controlled to be 90°C and the drying time was controlled to be 24 hours.

[0093] (4) 100 g of the coated sample obtained in step (3) was placed in a graphite crucible and placed in a box furnace, and the temperature was raised to 1200° C. in a difluorochloromethane atmosphere and kept warm for 4 h. The flow rate of difluorochloromethane was 2 L / min.

[0094] (5) The sintered sample obtained in step (4) was washed three times with pure water, and then filtered. The solid material obtained by filtration was dried at a temperature of 90° C. and a drying time of 24 h to obtain a low-ash sample.

[0095] The XRD pattern of the sample obtained after high-temperature sintering in a difluorochloromethane atmosphere, washing, filtration and drying is shown in Figure 4. As shown in Figure 4, the rice husk carbonized material after high-temperature sintering no longer contains SiO2 and other metal impurities.

[0096] (6) The low-ash sample obtained in step (5) was heated to 1500° C. in a carbonization furnace under a nitrogen atmosphere and kept at this temperature for 10 h, thereby obtaining a hard carbon negative electrode material.

[0097] Example 2

[0098] Compared with Example 1, the only difference is that in step (3), the mass ratio of the rice husk carbonized material to the phenolic resin is 3:1.

[0099] Example 3

[0100] Compared with Example 1, the only difference is that in step (3), the mass ratio of the rice husk carbonized material to the phenolic resin is 7:1.

[0101] Example 4

[0102] Compared with Example 1, the only difference is that the sintering temperature in the difluorochloromethane atmosphere in step (4) is 1000°C.

[0103] Example 5

[0104] Compared with Example 1, the only difference is that the sintering temperature in the difluorochloromethane atmosphere in step (4) is 1400°C.

[0105] Example 6

[0106] Compared with Example 1, the only difference is that the sintering time in the difluorochloromethane atmosphere in step (4) is 2 hours.

[0107] Example 7

[0108] Compared with Example 1, the only difference is that the sintering time in the difluorochloromethane atmosphere in step (4) is 6 hours.

[0109] Comparative Example 1

[0110] This comparative example provides a method for preparing a carbonaceous material, which uses an existing alkaline washing method to remove silicon dioxide, and the other steps are roughly the same as those in Example 1. The specific steps are as follows:

[0111] (1) The rice husk raw material was heated to 600°C in a box furnace under a nitrogen atmosphere and kept at this temperature for 2 h to obtain the rice husk carbonized material.

[0112] (2) The rice husk carbonized material obtained in step (1) was ball-milled using a planetary ball mill at a ball mill speed of 520 r / min, a ball-to-material ratio of 10:1, and a ball milling time of 5 h to obtain a powdered rice husk carbonized material.

[0113] (3) The powdered rice husk carbonized material obtained in step (2) and phenolic resin were added to a beaker at a mass ratio of 5:1. Alcohol was added to the beaker until the alcohol covered the mixture. The mass ratio of the total amount of the powdered rice husk carbonized material and phenolic resin to the alcohol was controlled to be 0.9:1. The mixture was then stirred using a blender. After stirring for 1 hour, the beaker containing the mixture and alcohol was placed in a drying oven to dry to obtain a coated sample. The drying temperature was controlled to be 90°C and the drying time was controlled to be 24 hours.

[0114] (4) The coated sample obtained in step (3) was reacted in a 6 mol / L NaOH solution for 6 h at a reaction temperature of 90°C.

[0115] (5) The powder after alkali washing is washed with water and filtered with a suction filter until the pH changes from alkaline to neutral, and then dried to obtain a sample after removing silica.

[0116] The XRD pattern of the sample obtained in step (5) is shown in FIG5 . As shown in FIG5 , the rice husk carbonized material still contains SiO 2 after alkaline washing with NaOH solution.

[0117] (6) The rice husk carbonized material powder after impurities removal was heated to 1500°C in a carbonization furnace under a nitrogen atmosphere and kept warm for 10 hours to obtain a hard carbon negative electrode material.

[0118] Comparative Example 2

[0119] This comparative example provides a method for preparing a carbonaceous material without performing an impurity removal step. The specific steps are as follows:

[0120] (1) The rice husk raw material was heated to 600°C in a box furnace under a nitrogen atmosphere and kept at this temperature for 2 h to obtain the rice husk carbonized material.

[0121] (2) The rice husk carbonized material obtained in step (1) was ball-milled using a planetary ball mill at a ball mill speed of 520 r / min, a ball-to-material ratio of 10:1, and a ball milling time of 5 h to obtain a powdered rice husk carbonized material.

[0122] (3) The powdered rice husk carbonized material was heated to 1500°C in a carbonization furnace under a nitrogen atmosphere and kept at this temperature for 10 h, thereby obtaining a hard carbon negative electrode material.

[0123] Test Example 1

[0124] The ash content of the carbonized materials of Examples 1-7 and Comparative Examples 1-2 before and after impurity removal and the true density and specific surface area after carbonization were tested respectively. The hard carbon negative electrode materials of Examples 1-7 and Comparative Examples 1-2 were assembled into button-type batteries, and their first charge specific capacity and first coulombic efficiency were tested. The results are shown in Table 1.

[0125] The working electrode is made by mixing the active material, conductive carbon, and sodium carboxymethyl cellulose in a mass ratio of 95:2:3 in deionized water and then coating the mixture on copper foil. A sodium sheet is used as the counter electrode. The electrolyte is 1 mol / L NaClO4 dissolved in a mixed solvent of EC (ethylene carbonate) / PC (propylene carbonate) (the volume ratio of EC to PC is 1:1) and 5 wt% FEC (fluoroethylene carbonate) is added. The diaphragm is made of glass fiber. The assembly of the button cell is carried out in a glove box with oxygen and water content below 1 ppm. The electrochemical performance test of the battery is carried out on an electrochemical workstation. The test voltage is 0.01-2.0 V and the current density is 30 mA / g. The test results are shown in Table 1:

[0126] Table 1: Anode material performance test results

[0127] As can be seen from Table 1, the negative electrode material prepared by the preparation method provided in the present disclosure has higher first efficiency and capacity, and has a lower specific surface area and true density, indicating that the material prepared in the present disclosure has a lower specific surface area but contains a large number of internal pores as active sites for sodium storage, and therefore exhibits excellent first efficiency and capacity performance. Industrial Applicability

[0128] The present invention utilizes a carbonized material formed from biomass materials and undergoes high-temperature sintering in a difluorochloromethane atmosphere. This process removes both silicon dioxide and metallic impurities such as iron and calcium, without the need for acid and alkali washing, and without wastewater treatment. The method provided by the present invention requires only a high-temperature sintering step, eliminating acid and alkali washing steps, making it easy to operate, more environmentally friendly, and economical, with excellent industrial applicability.

Claims

1. A method for preparing a carbonaceous material, characterized in that: include: The carbonized material formed by the biomass material is sintered at high temperature in a difluorochloromethane atmosphere; Wherein, the sintering temperature of the high temperature sintering is 1000°C-1500°C.

2. The preparation method according to claim 1, characterized in that: The sintering temperature of the high temperature sintering is 1100°C-1300°C.

3. The preparation method according to claim 1 or 2, characterized in that: The sintering time of the high temperature sintering is 2h-6h.

4. The preparation method according to claim 3, characterized in that: The sintering time of the high temperature sintering is 3h-5h.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The flow rate of chlorodifluoromethane per 100g of the carbonized material is 1L / min-3L / min.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The preparation process of the carbonized material includes: pre-carbonizing the biomass material, mixing it with an organic carbon source and an organic solvent to obtain a mixture, and drying the mixture to form an in-situ coating on the organic carbon source.

7. The preparation method according to claim 6, characterized in that: The biomass material is rice husk.

8. The preparation method according to claim 6 or 7, characterized in that: The carbonization temperature of the pre-carbonization is 500° C.-700° C., and the carbonization time is 1 h-4 h.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The pre-carbonization is carried out under an inert atmosphere.

10. The preparation method according to any one of claims 6 to 9, characterized in that: The organic carbon source is selected from at least one of phenolic resin, sucrose and glucose.

11. The preparation method according to claim 10, characterized in that: The organic carbon source is phenolic resin.

12. The preparation method according to any one of claims 6 to 11, characterized in that: The mass ratio of the pre-carbonized material to the organic carbon source is (3-7):

1.

13. The preparation method according to any one of claims 6 to 12, characterized in that: The mass ratio of the total amount of the pre-carbonized material and the organic carbon source to the organic solvent is (0.8-1.0):

1.

14. The preparation method according to any one of claims 6 to 13, characterized in that: The organic solvent is selected from at least one of ethanol, methanol, isopropanol and acetone.

15. The preparation method according to any one of claims 6 to 14, characterized in that: During the drying of the mixture, the drying temperature is controlled to be 80° C.-100° C. and the drying time is controlled to be 20 h-30 h.

16. The preparation method according to any one of claims 6 to 15, characterized in that: After the pre-carbonization is completed, ball milling is performed to obtain a powdery material, and then the powdery material is mixed with the organic carbon source and the organic solvent. The Dv50 of the powdery material is 4 μm-6 μm.

17. The preparation method according to claim 16, characterized in that: During the ball milling process, the ball mill speed is controlled at 450r / min-600r / min, the ball-to-material ratio is 8-12:1, and the ball milling time is 3h-8h.

18. The preparation method according to any one of claims 1 to 17, characterized in that: After the high-temperature sintering, the obtained sintered material is sequentially subjected to water washing to remove impurities and high-temperature carbonization.

19. The preparation method according to claim 18, characterized in that: The carbonization temperature of the high-temperature carbonization is 1300° C.-1700° C., and the carbonization time is 8 h-12 h.

20. The preparation method according to claim 19, characterized in that: The high temperature carbonization is carried out under an inert atmosphere.

21. The preparation method according to any one of claims 18 to 20, characterized in that: The water washing and impurity removal comprises water washing, solid-liquid separation and drying which are performed in sequence.

22. A carbonaceous material, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 21.

23. The carbonaceous material according to claim 22, characterized in that The carbonaceous material is hard carbon.

24. The carbonaceous material according to claim 22 or 23, characterized in that: The specific surface area of ​​the carbonaceous material is 0.9 m 2 / g-2.0m 2 / g, true density is 1.702g / cm 3 -1.825g / cm 3 .

25. A negative electrode plate, characterized in that: The negative electrode is prepared by using the carbonaceous material described in any one of claims 22 to 24 as the negative electrode active material.

26. A sodium ion battery, characterized in that: Including the negative electrode sheet as described in claim 25.

27. An electrical device, characterized in that: Including the sodium ion battery as described in claim 26.

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