A porous carbon material, a preparation method and application thereof

Abstract

The present application relates to the technical field of carbon material, and particularly discloses a kind of porous carbon material and its preparation method and application.The present application uses cheap and easily obtained coal tar as raw material, removes the phenolic light fraction in it by vacuum distillation, realizes the enrichment of heavy component, then the enriched heavy component is sequentially subjected to pre-oxidation, formaldehyde-ethylene urea crosslinking, Al-doped amino grafted nano boron oxide catalytic carbonization, CO2 gradient activation process, and porous carbon material is obtained.The porous carbon material has high conductivity, pore size distribution meeting the requirements of CVD silicon deposition, and stable carbon skeleton, providing a kind of porous carbon material with excellent comprehensive performance for sodium-ion battery, and realizing high-value utilization of coal tar, with broad market prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon materials, in particular to a porous carbon material and a preparation method and application thereof. BACKGROUND

[0002] The coking industry produces a large amount of by-product coal tar in the production process, which is rich in phenols, aromatic hydrocarbons and other high-value organic compounds, and is a good raw material source for preparing functional carbon materials. However, the traditional utilization of coal tar is mainly concentrated in the low-value-added field such as direct combustion, which not only fails to fully realize its resource value, but also produces pollutants in the combustion process, causing serious burden to the environment. Therefore, developing a high-value-added conversion path for coal tar has become a key problem to be solved in the industry.

[0003] In the field of new energy and new materials, CVD (chemical vapor deposition) silicon-carbon materials are widely used in key components such as lithium ion battery anodes due to their excellent electrochemical performance. As the core precursor for preparing CVD silicon-carbon, the performance of porous carbon materials directly determines the final quality of CVD silicon-carbon materials. To meet the preparation needs of CVD silicon-carbon, porous carbon materials need to have high specific surface area, reasonable hierarchical pore structure (especially the proportion of mesopores suitable for silicon deposition) and good electrical conductivity, which puts high requirements on the preparation process of porous carbon materials.

[0004] Currently, coal tar pitch is widely used as raw material to prepare porous carbon materials for silicon-carbon. Although this raw material is derived from coal tar and has certain resource advantages, the existing preparation technology still has many technical bottlenecks in practical application, which makes it difficult to meet the performance requirements of CVD silicon-carbon for porous carbon materials. The specific deficiencies are as follows: the existing technology uses a broad distillation cutting process for the pretreatment of coal tar, such as mixing the coal tar fraction above 360℃, which leads to insufficient enrichment of key active components, resulting in low utilization efficiency of raw materials and resource waste. Moreover, the existing process is difficult to simultaneously control the graphitization degree and pore structure, which makes it difficult for the product to meet the dual requirements of high electrical conductivity and pore size distribution suitable for CVD silicon deposition, affecting the performance stability of the subsequent silicon-carbon material.

[0005] Therefore, it is of great practical significance and industrial value to develop an efficient, environmentally friendly and high-performance method for preparing porous carbon materials for silicon-carbon from coal tar. SUMMARY

[0006] In view of the problems of low raw material utilization rate and inability to meet the dual requirements of high conductivity and pore size distribution required for CVD silicon deposition in the process of preparing porous carbon material for silicon-carbon by using existing coal tar pitch as raw material, the present application provides a kind of porous carbon material and its preparation method and application. The present application realizes the enrichment of heavy components by directional removal of phenolic light fraction in coal tar through vacuum distillation, and then realizes the precise regulation of the conductivity and pore size distribution of porous carbon by sequentially subjecting the enriched heavy components to pre-oxidation, formaldehyde-ethylene urea crosslinking, Al-doped amino grafted nano boron oxide catalytic carbonization, CO2 gradient activation and other processes, which not only realizes the high value utilization of coal tar, but also realizes the precise regulation of the conductivity and pore size distribution of porous carbon, so that the prepared porous carbon has excellent electron transport efficiency and space structure suitable for sodium ion storage, and has wide application prospect in the field of sodium ion battery.

[0007] To solve the above technical problems, the technical scheme provided by the present application is:

[0008] In a first aspect, the present application provides a method for preparing a porous carbon material, comprising the following steps:

[0009] S1, distillation cutting separation of raw coal tar to obtain a phenolic light fraction; adding an alkali solution to the phenolic light fraction, extracting to obtain an oil phase; adjusting the pH of the oil phase to weakly acidic, washing with water, dehydrating to obtain refined coal tar;

[0010] S2, passing air into the refined coal tar, pre-oxidizing by heating to obtain pre-oxidized refined coal tar;

[0011] S3, under the condition of 230℃~270℃, adding ethylene urea and part of formaldehyde into the pre-oxidized refined coal tar, heating to 320℃~380℃, adding the remaining formaldehyde, and crosslinking by heating to obtain crosslinked refined coal tar;

[0012] S4, adding Al-doped amino grafted nano boron oxide to the crosslinked refined coal tar, heating to 350℃~450℃, carbonizing under inert atmosphere, and crushing to obtain a precursor;

[0013] S5, subjecting the precursor to staged activation under CO2 atmosphere to obtain a porous carbon material.

[0014] Compared with the prior art, the preparation method of the porous carbon material provided by the present application first realizes the separation and enrichment of the phenolic light fraction in the raw coal tar through distillation cutting, then removes the phenolic substances by alkaline solution extraction, weak acid pH adjustment and water washing and dehydration, thereby avoiding the interference of the phenolic substances with the subsequent crosslinking and carbonization reactions. Then, the refined coal tar is pre-oxidized and then subjected to ethylene urea-formaldehyde staged crosslinking, the total ethylene urea and part of the formaldehyde are added in the medium-low temperature range first, the ethylene urea is allowed to react with the active sites in the pre-oxidized refined coal tar preferentially, a uniform reaction skeleton is constructed, and part of the formaldehyde is used to form short-chain crosslinking; then, the remaining formaldehyde is added after the temperature is raised to 320-380 DEG C, the reactivity of the aromatic hydrocarbon groups in the coal tar and the formaldehyde is significantly improved at this temperature, and deep crosslinking between aromatic compounds can be realized; in addition, the ethylene urea also avoids excessive polymerization of the formaldehyde through steric hindrance, and the crosslinking uniformity is significantly improved, this uniform crosslinking not only allows the carbon skeleton to shrink uniformly after carbonization, but also is beneficial to the formation of a continuous graphitized carbon skeleton after subsequent carbonization, and improves the conductivity and stress resistance of the porous carbon material.

[0015] The interface bonding force between the conventional catalyst and the organic carbon source is weak, and the catalyst is easy to agglomerate during carbonization, which leads to the formation of over-graphitized blocks in some local areas due to the excessive concentration of the catalyst, and the formation of amorphous carbon in other areas due to the lack of the catalyst, thereby causing uneven conductivity of the porous carbon. The amino groups in the Al-doped amino-grafted nano-boron oxide can be combined with the active groups (such as hydroxyl groups and carboxyl groups) in the crosslinked coal tar through chemical bonds, thereby realizing the uniform dispersion of the catalyst in the crosslinked coal tar matrix and ensuring the consistency of the graphitization reaction rate and degree in each area, so that the graphitized areas of the finally formed porous carbon are in a continuous network distribution, there is no obvious local over or under condition, the electronic transmission path is coherent, and the conductivity stability is significantly improved; in addition, the uniformly dispersed Al-doped amino-grafted nano-boron oxide particles in the crosslinked coal tar can form steric hindrance points, in the subsequent carbonization process, when the carbon source shrinks due to pyrolysis, the nano-boron oxide particles will hinder the excessive shrinkage of the surrounding carbon matrix, forming pores of a certain size around the particles, and the size range of the preliminary pores is directionally adjusted; at the same time, the interface bonding of the amino groups and the carbon source can constrain the shrinkage direction of the carbon matrix during carbonization through interface force, thereby being beneficial to the formation of a regular pore wall structure. This preliminary hierarchical pore structure can be further optimized in terms of mesopore ratio and pore size distribution after being subjected to CO2 staged activation, so as to make the prepared porous carbon material accurately adapt to the needs of CVD silicon deposition or sodium ion deintercalation.

[0016] Further, in S1, the raw coal tar is subjected to vacuum distillation, and a phenolic light fraction of 170-210 DEG C is collected.

[0017] Specifically, in S1, the distillation rate of the phenolic light fraction is 5-10 mL / min.

[0018] Further, in S1, the alkali solution is a NaOH solution with a mass concentration of 15% to 30%.

[0019] Further, in S1, the mass ratio of the phenolic light fraction to the alkali solution is 1: (0.6 to 1.0).

[0020] Further, in S1, the temperature for stirring extraction is 50°C to 70°C, and the time for stirring extraction is 1h to 2h.

[0021] Further, in S1, the weak acidity refers to a pH of 6 to 7.

[0022] Specifically, in S1, a sulfuric acid solution with a mass concentration of 4% to 6% is used to adjust the pH to 6 to 7, and then water washing is performed until no sulfate ions are present in the washing, and vacuum dehydration is performed at 70°C to 90°C and -0.09MPa to -0.095MPa.

[0023] Phenolic substances are easily volatile at high temperatures, causing loss of raw materials, and the volatilized phenolic substances are easily condensed in low-temperature areas of the equipment, forming coke-like deposits that can block the pipeline and affect production continuity. In addition, the hydroxyl group of free phenol is too active, easily causing local over-reaction during cross-linking, forming hard and brittle cross-linked blocks, leading to uneven cross-linking network and inability to build a complete three-dimensional cross-linked structure. Moreover, phenolic substances often combine with a small amount of heterocyclic compounds containing sulfur and nitrogen (such as thiophene and pyridine), increasing the difficulty of subsequent impurity removal. At the same time, phenolic substances are strong polar substances, and excessive presence can break the polarity balance of the oil phase system, causing uneven dispersion of cross-linking agents such as formaldehyde and ethylene urea in the oil phase, further exacerbating local differences in cross-linking reactions, and ultimately affecting the structural uniformity of the porous carbon precursor.

[0024] Through the above steps of distillation cutting, alkali solution extraction, and acid adjustment and water washing, the phenolic substances in coal tar can be effectively separated, so that the residual amount of phenolic substances in refined coal tar is ≤0.5%, avoiding its influence on subsequent cross-linking and carbonization reactions.

[0025] Further, in S2, the flow rate of the air introduced is 150L / min to 250L / min.

[0026] Further, in S2, the temperature for pre-oxidation is 150°C to 250°C, and the time for pre-oxidation is 1h to 3h.

[0027] Further, in S2, the heating rate for pre-oxidation is 4°C / min to 6°C / min.

[0028] The preferred pre-oxidation reaction conditions can cause the refined coal tar to fully undergo oxidation reactions, gradually generating active groups such as hydroxyl groups and carboxyl groups, providing sufficient reaction sites for the combination of ethylene urea and formaldehyde in the cross-linking stage.

[0029] Further, in S3, the total amount of formaldehyde is 5% to 10% of the mass of the pre-oxidized refined coal tar; and the partial formaldehyde is 50% to 80% of the total amount.

[0030] Specifically, in S3, the stirring rate is increased to 300 rpm to 400 rpm, and then the temperature is increased to 320 DEG C to 380 DEG C, and the remaining formaldehyde is added.

[0031] Further, in S3, the ethylene urea is 30 wt% to 50 wt% of the total amount of formaldehyde.

[0032] Further, in S3, the crosslinking reaction time is 2 h to 4 h.

[0033] In the traditional process, unbound free formaldehyde is easily left in the crosslinked product, and is decomposed into CO, H2O and other impurities during subsequent carbonization, destroying the pore structure. The present application improves the crosslinking density and uniformity by the method of staged ethylene urea-formaldehyde crosslinking. In the first stage, part of the formaldehyde and all the ethylene urea are added synchronously at 230 DEG C to 270 DEG C, avoiding excessive local reaction caused by high formaldehyde concentration in the first stage, and the double amino activity of ethylene urea is higher than that of formaldehyde, which can preferentially react with active groups in coal tar to uniformly occupy active sites. In addition, the amino group of ethylene urea can react with formaldehyde molecules, which can uniformly anchor formaldehyde at the active site, avoiding local accumulation or diffusion of formaldehyde, and thus avoiding the problems of local over-crosslinking or insufficient crosslinking. In the second stage, the remaining formaldehyde is added at high temperature, and a uniform ethylene urea-formaldehyde-coal tar preliminary crosslinking network has been formed in the system, so the subsequently added formaldehyde can quickly react with active groups in coal tar and ethylene urea-formaldehyde intermediates to build a long-chain interwoven uniform three-dimensional crosslinking network, providing a structural basis for the construction of stable carbon skeleton in the subsequent carbonization process.

[0034] Further, in S4, the preparation method of the Al-doped amino-grafted nano boron oxide comprises the following steps:

[0035] Step a, dispersing nano boron oxide in an alcohol solvent to obtain a nano boron oxide dispersion liquid;

[0036] The amino silane coupling agent is added to the acid alcohol aqueous solution to obtain an amino silane coupling agent solution;

[0037] Step b, adding the amino silane coupling agent solution to the nano boron oxide dispersion liquid, heating to 60 DEG C to 70 DEG C, and reacting for 2 h to 3 h, then solid-liquid separation, washing and drying to obtain amino-grafted nano boron oxide;

[0038] Step c, adding the amino-grafted nano boron oxide into an aqueous solution of aluminum salt, impregnating, evaporating to dryness, and then calcining at 500-600 DEG C in an air atmosphere, ball milling, to obtain the Al-doped amino-grafted nano boron oxide.

[0039] The Al-doped nano boron oxide can reduce the activation energy of the conversion of aromatic structures in cross-linked coal tar into graphite structures, so that the graphitization reaction can be efficiently started in a low temperature range of 350-450 DEG C. The amino group can react with active groups in the cross-linked coal tar through a chemical bond, thereby improving the compatibility of the nano boron oxide with the coal tar and the dispersion uniformity of the nano boron oxide in the coal tar. Through the catalysis and limiting effect of the Al-doped amino-grafted nano boron oxide, the graphitization degree of the porous carbon is precisely controlled, and a pore structure with a suitable size is constructed, thereby solving the bottleneck problem that the graphitization and pore structure of a traditional catalyst are difficult to be considered simultaneously.

[0040] Further, in step a, the alcohol solvent is anhydrous ethanol; and the volume-to-mass ratio of the alcohol solvent to the nano boron oxide is (100-400) mL:(5-20) g.

[0041] Further, in step a, the preparation of the acidic alcohol aqueous solution comprises the following steps: uniformly mixing alcohol solvent and water in a volume ratio of (10-50):(1-8), and adjusting the pH to 4-5 to obtain the acidic alcohol acid solution.

[0042] Specifically, in step a, after the amino silane coupling agent is added into the acidic alcohol aqueous solution, the solution is stirred at room temperature for 15-20 min to obtain an amino silane coupling agent solution.

[0043] Further, the mass ratio of the amino silane coupling agent to the nano boron oxide is (0.15-1.0):(5-20).

[0044] Specifically, the amino silane coupling agent is KH-550.

[0045] Further, in step b, the mass ratio of the amino-grafted nano boron oxide to the solute in the aqueous solution of aluminum salt is (5-20):(0.1-2).

[0046] Further, in step b, the aqueous solution of aluminum salt is an aluminum nitrate solution, and the concentration of the aqueous solution of aluminum salt is 0.002 g / mL-0.04 g / mL.

[0047] Further, in step b, the temperature is raised to 500-600 DEG C in a programmed manner, and the temperature raising rate is 4 DEG C / min-6 DEG C / min.

[0048] Further, in step b, the carbonization time is 1.5-2.5 h.

[0049] Further, in step b, the rotation speed of the ball mill is 200 rpm-400 rpm, the ball-to-material ratio is (5-10):1, and the ball milling time is 20 min-90 min.

[0050] Further, in S4, the Al-doped amino-grafted nano boron oxide is added in an amount of 1%-3% of the mass of the cross-linked refined coal tar.

[0051] Further, in S4, the carbonization time is 2 h-4 h.

[0052] Further, in S5, the staged activation specifically includes the following steps: heating the precursor to 750 DEG C-850 DEG C for heat preservation and activation for 2 h-4 h, and then heating to 900 DEG C-950 DEG C for heat preservation and activation for 1 h-1.5 h, to obtain the porous carbon material.

[0053] The Al-doped amino-grafted nano boron oxide can not only regulate the graphitization degree in the carbonization process of the carbon source and improve the conductivity of the porous carbon material, but also build a preliminary hierarchical pore structure suitable for subsequent activation in the carbonization process, thereby providing a core support for preparing the porous carbon with high conductivity and reasonable pore size distribution.

[0054] It should be noted that the inert atmosphere in the present application is provided by inert gas. The inert gas can be nitrogen, argon, helium and the like which are conventional in the art.

[0055] In a second aspect, the present application further provides a porous carbon material prepared by the preparation method of the porous carbon material according to any one of the above.

[0056] In a third aspect, the present application further provides a negative electrode comprising the porous carbon material.

[0057] In a fourth aspect, the present application further provides an application of the porous carbon material or the positive electrode in preparing a sodium ion battery.

[0058] In a fifth aspect, the present application further provides a sodium ion battery comprising the porous carbon material or the positive electrode.

[0059] In a sixth aspect, the present application further provides a battery module comprising the sodium ion battery.

[0060] The present application takes cheap and easily available coal tar as raw material, removes phenolic light fraction therefrom by vacuum distillation, realizes enrichment of heavy components, and then realizes the preparation of porous carbon material through pre-oxidation, formaldehyde-ethylene urea cross-linking, Al-doped amino grafted nano boron oxide catalytic carbonization, CO2 gradient activation and the like processes in sequence. The porous carbon material has high conductivity, pore size distribution meeting the requirement of CVD silicon deposition and stable carbon skeleton, and provides a porous carbon material with excellent comprehensive performance for sodium ion batteries, and realizes high value utilization of coal tar, and has wide market prospect. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0062] In order to better illustrate the present application, further example is made by examples below.

[0063] Example 1

[0064] The present application provides a preparation method of porous carbon material, and the specific steps are as follows:

[0065] S1, vacuum distillation is carried out on raw coal tar, and 170℃~210℃ fraction is collected at a distillation rate of 5mL / min to obtain a light fraction containing phenols; a 15% NaOH solution is added to the light fraction containing phenols, the mass of the NaOH solution is 0.8 times the mass of the light fraction containing phenols, stirring extraction is carried out at 60℃ for 1h, after standing and separating, the water phase is separated, the remaining oil phase is neutralized to pH=6.7 with 5% sulfuric acid solution, and washed with water until there is no sulfate ion in the washing liquid, and then vacuum dehydration is carried out at 80℃ and-0.09MPa to obtain refined coal tar, the residual amount of phenolic substances in the refined coal tar is ≤0.5% and the ash content is ≤0.3% detected by HPLC;

[0066] S2, the refined coal tar is transferred into a reaction kettle with stirring, air with a flow rate of 200L / min is introduced, and the temperature is raised to 200℃ at a rate of 5℃ / min, and then the temperature is kept for 2h to obtain pre-oxidized refined coal tar;

[0067] S3, the pre-oxidized refined coal tar is heated to 250℃, 70% of the total amount of formaldehyde and all ethylene urea are added, then the stirring rate is controlled at 300rpm, the temperature is raised to 350℃, the remaining amount of formaldehyde is added, and then the temperature is kept for 3h to obtain cross-linked refined coal tar; wherein the total amount of formaldehyde is 10% of the mass of the pre-oxidized refined coal tar, and the ethylene urea is 40wt% of the total amount of formaldehyde;

[0068] S4. Add 2% by mass of Al-doped amino-grafted nano-B2O3 to the above cross-linked refined coal tar, heat to 400℃, introduce nitrogen gas at a flow rate of 100mL / min, keep warm for 3h, and pulverize to 100 mesh to obtain catalyst precursor.

[0069] S5. The above catalyst precursor is placed in a tube furnace and heated to 800°C for 3 hours under nitrogen protection. Then it is heated to 920°C for 1 hour and cooled to obtain porous carbon material.

[0070] The preparation method of the above-mentioned Al-doped amino-grafted nano-B2O3 includes the following steps:

[0071] Weigh 10g of nano B2O3 and place it in a three-necked flask. Add 200mL of anhydrous ethanol and sonicate for 30min to obtain nano B2O3 dispersion.

[0072] Measure 30 mL of anhydrous ethanol and 5 mL of deionized water, adjust the pH to 4.5 with 37% hydrochloric acid, add 0.4 g of KH550, and stir magnetically for 15 min to obtain a KH550 solution.

[0073] KH550 solution was slowly added dropwise to the nano B2O3 dispersion at a rate of 1 mL / min, while stirring (200 rpm) and reflux were started simultaneously. The temperature was raised to 65℃ and the reaction was maintained at this temperature for 2 h. After the reaction was completed, the mixture was centrifuged at 8000 rpm for 15 min, the supernatant was discarded, the precipitate was washed with anhydrous ethanol, and dried under vacuum at 80℃ for 4 h to obtain amino-grafted nano B2O3.

[0074] Weigh out 1.7g of Al(NO3)3 Add 9H2O to 50mL of deionized water and stir magnetically until completely dissolved to obtain an aluminum nitrate solution. Add 10g of the above-prepared amino-grafted nano-B2O3 to the aluminum nitrate solution and stir at 300rpm for 1h. Then transfer to a rotary evaporator and evaporate to dryness at 50℃ and -0.08MPa. Place in a muffle furnace and heat to 550℃ at a rate of 5℃ / min under air atmosphere, hold for 2.5h, and cool naturally to room temperature. Transfer the powder to a planetary ball mill, add agate balls with a ball-to-material ratio of 8:1, and mill at 300rpm for 30min to obtain Al-doped amino-grafted nano-B2O3.

[0075] Example 2

[0076] This invention provides a method for preparing porous carbon materials, the specific steps of which are as follows:

[0077] S1, the raw coal tar is subjected to vacuum distillation, and a 170℃-210℃ fraction is collected at a distillation rate of 10mL / min to obtain a light fraction containing phenols; a 23% NaOH solution is added to the light fraction containing phenols, the mass of the NaOH solution is 0.7 times the mass of the light fraction containing phenols, the mixture is stirred at 70℃ for 1h, and after standing and separation, the water phase is separated, the remaining oil phase is neutralized to pH=6.5 with a 5% sulfuric acid solution, washed with water until the washing liquid is free of sulfate ions, and dehydrated at 80℃ and -0.09MPa to obtain refined coal tar, wherein the residual amount of phenolic substances is less than or equal to 0.5% and the ash content is less than or equal to 0.3% as detected by HPLC;

[0078] S2, the refined coal tar is transferred into a stirred reaction kettle, air is introduced at a flow rate of 150L / min, and the temperature is raised to 230℃ at a rate of 4℃ / min, and the mixture is kept at 230℃ for 1h to obtain pre-oxidized refined coal tar;

[0079] S3, the pre-oxidized refined coal tar is heated to 230℃, 80% of the total amount of formaldehyde and all ethylene urea are added, and then the stirring rate is controlled at 400rpm, the temperature is raised to 320℃, the remaining formaldehyde is added, and the mixture is kept at 320℃ for 2h to obtain cross-linked refined coal tar; wherein the total amount of formaldehyde is 9% of the mass of the pre-oxidized refined coal tar, and the ethylene urea is 30wt% of the total amount of formaldehyde;

[0080] S4, 1.5% of Al-doped amino-grafted nano-B2O3 by mass is added to the cross-linked refined coal tar, the mixture is heated to 350℃, nitrogen is introduced at a flow rate of 100mL / min, and the mixture is kept at 350℃ for 4h, and then the mixture is pulverized to 100 mesh to obtain a catalyst precursor;

[0081] S5, the catalyst precursor is placed in a tube furnace, heated to 750℃ under nitrogen protection, activated for 4h, then heated to 950℃, activated for 1h, and cooled to obtain a porous carbon material.

[0082] The preparation method of the Al-doped amino-grafted nano-B2O3 includes the following steps:

[0083] 5g of nano-B2O3 is weighed and placed in a three-necked flask, 100mL of anhydrous ethanol is added, and the mixture is ultrasonically dispersed for 30min to obtain a nano-B2O3 dispersion;

[0084] 10mL of anhydrous ethanol and 1mL of deionized water are measured, the pH is adjusted to 4.2 with 37% hydrochloric acid, 0.15g of KH550 is added, and the mixture is magnetically stirred for 15min to obtain a KH550 solution;

[0085] The KH550 solution was slowly added to the nano-B2O3 dispersion liquid at a drop rate of 1 mL / min, while stirring (200 rpm) and condensation reflux were started, the temperature was increased to 60 DEG C, and the reaction was kept for 3 h. After the reaction was completed, the supernatant was discarded by centrifugation at 8000 rpm for 15 min, and the precipitate was washed with anhydrous ethanol and vacuum dried at 80 DEG C for 4 h to obtain the amino-grafted nano-B2O3;

[0086] 0.1 g of Al (NO3)3 9H2O was added to 50 mL of deionized water, and magnetic stirring was performed until complete dissolution to obtain an aluminum nitrate solution; 5 g of the above-prepared amino-grafted nano-B2O3 was added to the aluminum nitrate solution, and stirring was performed at 300 rpm for 1 h, and then the solution was transferred to a rotary evaporator and evaporated to dryness at 50 DEG C and -0.08 MPa. The powder was placed in a muffle furnace, and the temperature was increased to 600 DEG C at a rate of 6 DEG C / min under an air atmosphere. The temperature was kept for 2 h, and the powder was naturally cooled to room temperature. The powder was transferred to a planetary ball mill, and a maroon ball was added. The ball-to-material ratio was 5:1, and the ball milling speed was 200 rpm. The powder was ball milled for 60 min to obtain Al-doped amino-grafted nano-B2O3.

[0087] Example 3

[0088] The embodiment of the present application provides a preparation method of a porous carbon material, and the specific steps are as follows:

[0089] S1, vacuum distillation was performed on the raw coal tar, and a phenolic light fraction was collected at a distillation rate of 6 mL / min at 170 DEG C to 210 DEG C; a 18% NaOH solution was added to the obtained phenolic light fraction, and the mass of the NaOH solution was 0.9 times the mass of the phenolic light fraction. The mixture was stirred and extracted at 50 DEG C for 2 h. After standing and separating the water phase, the remaining oil phase was neutralized to pH=6.4 with a 5% sulfuric acid solution, and washed with water until there was no sulfate ion in the washing liquid. The oil phase was vacuum dehydrated at 80 DEG C and -0.09 MPa to obtain refined coal tar. The residual amount of phenolic substances in the refined coal tar was less than or equal to 0.5% as detected by HPLC, and the ash content was less than or equal to 0.3%;

[0090] S2, the above-prepared refined coal tar was transferred into a reaction kettle with stirring, and air was introduced at a flow rate of 160 L / min. The temperature was increased to 180 DEG C at a rate of 6 DEG C / min, and the temperature was kept for 3 h to obtain pre-oxidized refined coal tar;

[0091] S3, the above-prepared pre-oxidized refined coal tar was heated to 270 DEG C, and 50% of the total amount of formaldehyde and all ethylene urea were added. Then the stirring speed was controlled to be 200 rpm, the temperature was increased to 360 DEG C, the remaining amount of formaldehyde was added, and the temperature was kept for 3 h to obtain crosslinked refined coal tar. The total amount of formaldehyde was 8% of the mass of the pre-oxidized refined coal tar, and the ethylene urea was 35 wt% of the total amount of formaldehyde;

[0092] S4. Add 1% by mass of Al-doped amino-grafted nano-B2O3 to the above cross-linked refined coal tar, heat to 450℃, introduce nitrogen gas at a flow rate of 100mL / min, keep warm for 2h, and pulverize to 100 mesh to obtain catalyst precursor.

[0093] S5. The above catalyst precursor is placed in a tube furnace and heated to 850°C for 2 hours under nitrogen protection. Then it is heated to 900°C for 1.5 hours and cooled to obtain porous carbon material.

[0094] The preparation method of the above-mentioned Al-doped amino-grafted nano-B2O3 includes the following steps:

[0095] Weigh 20g of nano B2O3 and place it in a three-necked flask. Add 400mL of anhydrous ethanol and sonicate for 30min to obtain nano B2O3 dispersion.

[0096] Measure 50 mL of anhydrous ethanol and 8 mL of deionized water, adjust the pH to 4.8 with 37% hydrochloric acid, add 1.0 g of KH550, and stir magnetically for 15 min to obtain a KH550 solution.

[0097] KH550 solution was slowly added dropwise to the nano B2O3 dispersion at a rate of 1 mL / min, while stirring (200 rpm) and reflux were started simultaneously. The temperature was raised to 70 °C and the reaction was maintained at this temperature for 2 h. After the reaction was completed, the mixture was centrifuged at 8000 rpm for 15 min, the supernatant was discarded, the precipitate was washed with anhydrous ethanol, and dried under vacuum at 80 °C for 4 h to obtain amino-grafted nano B2O3.

[0098] Weigh out 2g of Al(NO3)3 Add 9H2O to 50mL of deionized water and stir magnetically until completely dissolved to obtain an aluminum nitrate solution. Add 20g of the above-prepared amino-grafted nano-B2O3 to the aluminum nitrate solution and stir at 300rpm for 1h. Then transfer it to a rotary evaporator and evaporate it to dryness at 50℃ and -0.08MPa. Place it in a muffle furnace and heat it to 500℃ at a rate of 4℃ / min under air atmosphere. Hold it at this temperature for 3h and allow it to cool naturally to room temperature. Transfer the powder to a planetary ball mill, add agate balls with a ball-to-material ratio of 10:1, and mill at 400rpm for 40min to obtain Al-doped amino-grafted nano-B2O3.

[0099] Example 4

[0100] This invention provides a method for preparing porous carbon materials, the specific steps of which are as follows:

[0101] S1, the raw coal tar is subjected to vacuum distillation, and a 170℃-210℃ fraction is collected at a distillation rate of 8mL / min to obtain a phenolic light fraction; a 25% NaOH solution is added to the obtained phenolic light fraction, the mass of the NaOH solution is 0.7 times the mass of the phenolic light fraction, the mixture is stirred at 55℃ for 2h, the water phase is separated after standing and layering, the remaining oil phase is neutralized to pH=6.0 with a 5% sulfuric acid solution, washed with water until the washing liquid is free of sulfate ions, and dehydrated at 80℃ and -0.09MPa vacuum to obtain refined coal tar, wherein the residual amount of phenolic substances in the refined coal tar is less than or equal to 0.5% as detected by HPLC, and the ash content is less than or equal to 0.3%;

[0102] S2, the refined coal tar is transferred into a stirred reaction kettle, air is introduced at a flow rate of 220L / min, and the temperature is raised to 180℃ at a rate of 5℃ / min, and the mixture is kept at 180℃ for 2.5h to obtain pre-oxidized refined coal tar;

[0103] S3, the pre-oxidized refined coal tar is heated to 240℃, 60% of the total amount of formaldehyde and all ethylene urea are added, then the stirring rate is controlled at 280rpm, the temperature is raised to 330℃, the remaining formaldehyde is added, and the mixture is kept at 330℃ for 4h to obtain cross-linked refined coal tar; wherein the total amount of formaldehyde is 5% of the mass of the pre-oxidized refined coal tar, and the ethylene urea is 45wt% of the total amount of formaldehyde;

[0104] S4, 3% of Al-doped amino-grafted nano-B2O3 is added to the cross-linked refined coal tar, the mixture is heated to 380℃, nitrogen is introduced at a flow rate of 100mL / min, and the mixture is kept at 380℃ for 4h, and then the mixture is pulverized to 100 mesh to obtain a catalyst precursor;

[0105] S5, the catalyst precursor is placed in a tube furnace, heated to 780℃ under nitrogen protection, kept at 780℃ for 3h, then heated to 910℃, kept at 910℃ for 1h, and cooled to obtain a porous carbon material.

[0106] The preparation method of the Al-doped amino-grafted nano-B2O3 is the same as that of Example 1, which will not be repeated here.

[0107] Example 5

[0108] The embodiment of the application provides a preparation method of a porous carbon material, and the specific steps are as follows:

[0109] S1, the raw coal tar is subjected to vacuum distillation, and a 170℃-210℃ fraction is collected at a distillation rate of 7mL / min to obtain a phenolic light fraction; a 20% NaOH solution is added to the obtained phenolic light fraction, the mass of the NaOH solution is 1.0 times the mass of the phenolic light fraction, the mixture is stirred at 65℃ for 1h, the water phase is separated after standing and layering, the remaining oil phase is neutralized to pH=6.8 with a 5% sulfuric acid solution, washed with water until the washing liquid is free of sulfate ions, and dehydrated at 80℃ and under a vacuum of-0.09MPa to obtain refined coal tar, wherein the residual amount of phenolic substances in the refined coal tar is less than or equal to 0.5% as detected by HPLC, and the ash content is less than or equal to 0.3%;

[0110] S2, the refined coal tar is transferred into a reaction kettle with stirring, air with a flow rate of 250L / min is introduced, the temperature is raised to 250℃ at a rate of 6℃ / min, and the mixture is kept at 250℃ for 1h to obtain pre-oxidized refined coal tar;

[0111] S3, the pre-oxidized refined coal tar is heated to 260℃, 65% of the total amount of formaldehyde and all ethylene urea are added, then the stirring rate is controlled to be 250rpm, the temperature is raised to 340℃, the remaining amount of formaldehyde is added, and the mixture is kept at 340℃ for 3h to obtain cross-linked refined coal tar; wherein the total amount of formaldehyde is 6% of the mass of the pre-oxidized refined coal tar, and the ethylene urea is 50wt% of the total amount of formaldehyde;

[0112] S4, 2.5% of Al-doped amino-grafted nano-B2O3 by mass of the cross-linked refined coal tar is added to the cross-linked refined coal tar, the mixture is heated to 420℃, nitrogen gas with a flow rate of 100mL / min is introduced, and the mixture is kept at 420℃ for 2h, and then the mixture is pulverized to 100 mesh to obtain a catalyst precursor;

[0113] S5, the catalyst precursor is placed in a tube furnace, heated to 750℃-850℃ under nitrogen protection, activated for 2h-4h, then heated to 900℃-950℃, activated for 1h-1.5h, and cooled to obtain a porous carbon material.

[0114] The preparation method of the Al-doped amino-grafted nano-B2O3 is the same as that of Example 2, and will not be described here again.

[0115] Example 6

[0116] The embodiment of the application provides a preparation method of a porous carbon material, and the specific steps are as follows:

[0117] S1, the raw coal tar is subjected to vacuum distillation, and a 170-210℃ fraction is collected at a distillation rate of 9mL / min to obtain a light fraction containing phenols; a 30% NaOH solution is added to the light fraction containing phenols, the mass of the NaOH solution is 0.6 times the mass of the light fraction containing phenols, and the mixture is stirred at 50℃ for 1h; after standing and separation, the water phase is separated, the remaining oil phase is neutralized to pH=6.2 with a 5% sulfuric acid solution, washed with water until the washing liquid is free of sulfate ions, and dehydrated at 80℃ and -0.09MPa to obtain refined coal tar, wherein the residual amount of phenolic substances is less than or equal to 0.5% and the ash content is less than or equal to 0.3% as determined by HPLC;

[0118] S2, the refined coal tar is transferred into a stirred reaction kettle, and air is introduced at a flow rate of 210L / min, and the temperature is increased to 150℃ at a rate of 4℃ / min, and the mixture is kept at 150℃ for 3h to obtain pre-oxidized refined coal tar;

[0119] S3, the pre-oxidized refined coal tar is heated to 265℃, and 75% of the total amount of formaldehyde and all ethylene urea are added, and then the stirring rate is controlled at 300rpm, and the temperature is increased to 380℃, and the remaining amount of formaldehyde is added, and the mixture is kept at 380℃ for 2h to obtain cross-linked refined coal tar; wherein the total amount of formaldehyde is 7% of the mass of the pre-oxidized refined coal tar, and the ethylene urea is 38wt% of the total amount of formaldehyde;

[0120] S4, 2.3% of Al-doped amino-grafted nano-B2O3 by mass is added to the cross-linked refined coal tar, the mixture is heated to 430℃, nitrogen is introduced at a flow rate of 100mL / min, and the mixture is kept at 430℃ for 2h, and then the mixture is pulverized to 100 mesh to obtain a catalyst precursor;

[0121] S5, the catalyst precursor is placed in a tube furnace, and heated to 810℃ under nitrogen protection, and kept at 810℃ for 3h, and then heated to 930℃ and kept at 930℃ for 1h, and then cooled to obtain a porous carbon material.

[0122] The preparation method of the Al-doped amino-grafted nano-B2O3 is the same as that of Example 3 and will not be repeated here.

[0123] Comparative Example 1

[0124] This comparative example provides a method for preparing a porous carbon material, which is different from Example 1 only in that the Al-doped amino-grafted nano-B2O3 in S4 is replaced with an equal amount of Al-doped carboxyl-grafted nano-B2O3, and the rest is exactly the same, which will not be repeated here.

[0125] The preparation method of the Al-doped carboxyl-grafted nano-B2O3 comprises the following steps:

[0126] 10g of nano-B2O3 is weighed into a three-necked flask, 200mL of anhydrous ethanol is added, and the mixture is ultrasonically dispersed for 30min to obtain a nano-B2O3 dispersion.

[0127] Take 30 mL of anhydrous ethanol and 5 mL of deionized water, adjust the pH to 5.5 with 37% hydrochloric acid, add 0.4 g of KH560, and magnetically stir for 15 min to obtain a KH560 solution;

[0128] Slowly add the KH560 solution to the nano-B2O3 dispersion, and the dropwise rate is 1 mL / min. At the same time, start stirring (speed 200 rpm) and condensation reflux, and heat to 75°C. After reaction for 2 h, centrifuge at 8000 rpm for 15 min, discard the supernatant, wash the precipitate with anhydrous ethanol, and vacuum dry at 80°C for 4 h to obtain carboxyl grafted nano-B2O3.

[0129] Take 1.7 g of Al (NO3) 3 9H2O into 50 mL of deionized water, and magnetically stir until completely dissolved to obtain an aluminum nitrate solution. Add 10 g of the carboxyl grafted nano-B2O3 prepared above to the aluminum nitrate solution, and stir at 300 rpm for 1 h. Then, transfer to a rotary evaporator, evaporate at 50°C and -0.08 MPa to dryness, and place in a muffle furnace. Heat to 550°C at a rate of 5°C / min under an air atmosphere, and heat for 2.5 h. Naturally cool to room temperature, transfer the powder to a planetary ball mill, place in agate balls, and ball mill at a speed of 300 rpm for 30 min to obtain Al-doped carboxyl grafted nano-B2O3.

[0130] Comparative Example 2

[0131] This comparative example provides a preparation method of a porous carbon material, which is different from Example 1 only in that the Al-doped amino grafted nano-B2O3 in S4 is replaced by an equal amount of Al-doped mercapto grafted nano-B2O3, and the rest is exactly the same. Here, no further description is given.

[0132] The preparation method of the Al-doped mercapto grafted nano-B2O3 comprises the following steps:

[0133] Take 10 g of nano-B2O3 and place in a three-necked flask, add 200 mL of anhydrous ethanol, and ultrasonically disperse for 30 min to obtain a nano-B2O3 dispersion;

[0134] Take 30 mL of anhydrous ethanol and 5 mL of deionized water, adjust the pH to 4.3 with 37% hydrochloric acid, add 0.4 g of KH590, and magnetically stir for 15 min to obtain a KH590 solution;

[0135] KH590 solution was slowly added dropwise to the nano B2O3 dispersion at a rate of 1 mL / min, while stirring (200 rpm) and reflux were started simultaneously. The temperature was raised to 70 °C and the reaction was maintained at this temperature for 2 h. After the reaction was completed, the mixture was centrifuged at 8000 rpm for 15 min, the supernatant was discarded, the precipitate was washed with anhydrous ethanol, and the mixture was vacuum dried at 80 °C for 4 h to obtain thiol-grafted nano B2O3.

[0136] Weigh out 1.7g of Al(NO3)3 Add 9H2O to 50mL of deionized water and stir magnetically until completely dissolved to obtain an aluminum nitrate solution. Add 10g of the above-prepared thiol-grafted nano-B2O3 to the aluminum nitrate solution and stir at 300rpm for 1h. Then transfer to a rotary evaporator and evaporate to dryness at 50℃ and -0.08MPa. Place in a muffle furnace and heat to 550℃ at a rate of 5℃ / min under air atmosphere, hold for 2.5h, and cool naturally to room temperature. Transfer the powder to a planetary ball mill, add agate balls with a ball-to-material ratio of 8:1, and mill at 300rpm for 30min to obtain Al-doped thiol-grafted nano-B2O3.

[0137] Comparative Example 3

[0138] This comparative example provides a method for preparing porous carbon materials. The only difference from Example 1 is that the air pre-oxidation step S2 is omitted, and the formaldehyde-vinyl urea composite crosslinking step in S3 is carried out directly. The rest is exactly the same and will not be described again here.

[0139] Comparative Example 4

[0140] This comparative example provides a method for preparing porous carbon materials. The only difference from Example 1 is that the formaldehyde in S3 is added all at once, and ethylene urea is not added. The rest is exactly the same and will not be described again here. The specific steps in S3 are as follows:

[0141] S3, the above pre-oxidized refined coal tar is heated to 250°C, formaldehyde is added, and the temperature is maintained for 3 hours to obtain cross-linked refined coal tar; wherein, the amount of formaldehyde used is 10% of the mass of the pre-oxidized refined coal tar.

[0142] Comparative Example 5

[0143] This comparative example provides a method for preparing porous carbon materials. The only difference from Example 1 is that the Al-doped amino-grafted nano-B2O3 in S4 is replaced with an equal amount of nano-B2O3. The rest is exactly the same and will not be described again here.

[0144] Comparative Example 6

[0145] This comparative example provides a method for preparing porous carbon materials, which differs from Example 1 only in that S5 is replaced with a one-stage activation; the rest is identical. Specifically, S5 is as follows:

[0146] S5, the above catalyst precursor was placed in a tube furnace, and was heated to 900°C under nitrogen protection for 4h, and was cooled to obtain a porous carbon material.

[0147] Comparative Example 7

[0148] This comparative example provides a preparation method of a porous carbon material, which is different from Example 1 only in that the Al-doped amino grafted nano B2O3 in S4 is replaced by an equal amount of nano Fe2O3, and the rest is exactly the same, which will not be repeated here.

[0149] Comparative Example 8

[0150] This comparative example provides a preparation method of a porous carbon material, which is different from Example 1 only in that the Al-doped amino grafted nano B2O3 in S4 is replaced by an equal amount of Al-doped nano B2O3, and the rest is exactly the same, which will not be repeated here.

[0151] The preparation method of the Al-doped nano B2O3 includes the following steps:

[0152] 1.7g of Al (NO3)3 9H2O was added to 50mL of deionized water, and was magnetically stirred until completely dissolved to obtain an aluminum nitrate solution; 10g of nano B2O3 was added to the aluminum nitrate solution, and was stirred at 300rpm for 1h, and then was transferred to a rotary evaporator, and was evaporated to dryness at 50°C and -0.08MPa, and was placed in a muffle furnace, and was heated to 550°C at a rate of 5°C / min under an air atmosphere, and was kept for 2.5h, and was naturally cooled to room temperature, and the powder was transferred to a planetary ball mill, and was placed in agate balls with a ball-to-material ratio of 8:1, and was ball milled at a speed of 300rpm for 30min to obtain Al-doped nano B2O3.

[0153] Comparative Example 9

[0154] This comparative example provides a preparation method of a porous carbon material, which is different from Example 1 only in that the Al-doped amino grafted nano B2O3 in S4 is replaced by an equal amount of amino grafted nano B2O3, and the rest is exactly the same, which will not be repeated here.

[0155] 10g of nano B2O3 was weighed and placed in a three-necked flask, 200mL of anhydrous ethanol was added, and was ultrasonically dispersed for 30min to obtain a nano B2O3 dispersion;

[0156] 30mL of anhydrous ethanol and 5mL of deionized water were measured, and the pH was adjusted to 4.5 with 37% hydrochloric acid, 0.4g of KH550 was added, and was magnetically stirred for 15min to obtain a KH550 solution;

[0157] The KH550 solution is slowly added dropwise into the nano-B2O3 dispersion liquid at a dropwise adding rate of 1 mL / min, while stirring (rotation speed 200 rpm) and condensation reflux are started, the temperature is raised to 65 DEG C, and the reaction is kept for 2 hours, after the reaction is completed, centrifugation is carried out at 8000 rpm for 15 min, the supernatant is discarded, the precipitate is washed with anhydrous ethanol, vacuum drying is carried out at 80 DEG C for 4 hours, and the amino-grafted nano-B2O3 is obtained.

[0158] The specific surface area, pore volume and pore size distribution of the porous carbon materials prepared in the above examples 1 to 6 and comparative examples 1 to 9 are tested by using a nitrogen adsorption / desorption tester (Micromeritics ASAP 2020), and the resistivity of the porous carbon materials is tested by using an impedance analyzer, and the results are shown in Table 1.

[0159] Table 1

[0160]

[0161] It can be known from the results that, in the examples of the present application, the air pre-oxidation, the Al-doped amino-grafted nano-B2O3 as a carbonization catalyst, the staged ethylene urea-formaldehyde crosslinking and the staged activation are the key synergistic process combinations for realizing the breakthrough of the comprehensive performance of the porous carbon material, and are indispensable. Through the preparation method of the porous carbon material provided by the present application, the problem that the dual requirements of high conductivity and the pore size distribution meeting the CVD silicon deposition requirement are difficult to be considered in the prior art are effectively solved, a high-quality carbon matrix is provided for the CVD method for preparing high-performance silicon-carbon composite materials, in addition, the preparation method uses industrial by-product coal tar as raw material, realizes the high-value cyclic utilization of resources, and has important practical value for promoting the synergistic development of new energy industry and circular economy.

[0162] The above only describes the preferred embodiments of the present application and should not be used to limit the present application, and any modification, equivalent replacement or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing porous carbon materials, characterized in that, Includes the following steps: S1, the raw coal tar is distilled and separated to obtain a light fraction containing phenols; an alkaline solution is added to the light fraction containing phenols for extraction to obtain an oil phase; the pH of the oil phase is adjusted to weakly acidic, washed with water, and dehydrated to obtain refined coal tar; S2, Air is introduced into the refined coal tar and the temperature is raised for pre-oxidation to obtain pre-oxidized refined coal tar; S3, at 230℃~270℃, ethylene urea and part of formaldehyde are added to the pre-oxidized refined coal tar, the temperature is raised to 320℃~380℃, the remaining formaldehyde is added, and the temperature is kept warm to carry out the cross-linking reaction to obtain cross-linked refined coal tar. S4, Al-doped amino-grafted nano boron oxide is added to the cross-linked refined coal tar, the temperature is raised to 350℃~450℃, carbonization is carried out under an inert atmosphere, and then pulverized to obtain the precursor. S5, the precursor is activated in stages under a CO2 atmosphere to obtain a porous carbon material.

2. The method for preparing porous carbon materials as described in claim 1, characterized in that, In S2, the air flow rate is 150 L / min to 250 L / min; and / or In S2, the pre-oxidation temperature is 150℃~250℃, and the pre-oxidation time is 1h~3h; and / or In S2, the heating rate of the pre-oxidation is 4℃ / min to 6℃ / min.

3. The method for preparing porous carbon materials as described in claim 1, characterized in that, In S3, the total amount of formaldehyde used is 5% to 10% of the mass of the pre-oxidized refined coal tar; the portion of formaldehyde used is 50% to 80% of the total amount; and / or In S3, the ethylene urea is 30wt%~50wt% of the total formaldehyde; and / or In S3, the cross-linking reaction takes 2 to 4 hours.

4. The method for preparing porous carbon materials as described in claim 1, characterized in that, In S4, the preparation method of the Al-doped amino-grafted boron oxide nanoparticles includes the following steps: Step a: Disperse boron oxide nanoparticles in an alcohol solvent to obtain a boron oxide nanoparticle dispersion; An aminosilane coupling agent is added to an acidic alcohol aqueous solution to obtain an aminosilane coupling agent solution. Step b: Add the aminosilane coupling agent solution to the nano boron oxide dispersion, heat to 60℃~70℃, keep the temperature for 2h~3h, separate the solid and liquid, wash, and dry to obtain amino-grafted nano boron oxide; Step c: The amino-grafted nano boron oxide is added to an aluminum salt aqueous solution, impregnated, evaporated to dryness, and then calcined at 500℃~600℃ in air atmosphere and ball-milled to obtain the Al-doped amino-grafted nano boron oxide.

5. The method for preparing porous carbon materials as described in claim 4, characterized in that, The mass ratio of the aminosilane coupling agent to nano-boron oxide is (0.15~1.0):(5~20); and / or The mass ratio of the amino-grafted nano-boron oxide to the solute in the aluminum salt aqueous solution is (5~20):(0.1~2).

6. The method for preparing porous carbon materials as described in claim 1, characterized in that, In S4, the amount of Al-doped amino-grafted nano-boron oxide added is 1% to 3% of the mass of the cross-linked refined coal tar; and / or In S4, the carbonization time is 2h~4h.

7. The method for preparing porous carbon materials as described in claim 1, characterized in that, In S5, the phased activation specifically includes the following steps: heating the precursor to 750℃~850℃ and holding it at that temperature for 2h~4h, then heating it to 900℃~950℃ and holding it at that temperature for 1h~1.5h to obtain porous carbon material.

8. A porous carbon material, characterized in that, It is prepared by the method for preparing porous carbon materials according to any one of claims 1 to 7.

9. A negative electrode, characterized in that, Including the porous carbon material as described in claim 8.

10. A sodium-ion battery, characterized in that, It includes the porous carbon material of claim 8 or the negative electrode of claim 9.

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