A lignite resin-based nitrogen-doped porous carbon material and a preparation method thereof

Abstract

This invention discloses a nitrogen-doped porous carbon material based on lignite resin and its preparation method, comprising the following steps: 1) mixing an ethanol solution of a nitrogen source and lignite resin under heating to obtain a mixed solution I; 2) mixing the mixed solution I obtained in step 1) with an ethanol solution of an organic salt under heating to obtain a mixed solution II of lignite resin, nitrogen source, and organic salt; 3) drying and curing the mixed solution II obtained in step 2) to obtain a carbonization precursor; 4) carbonizing the carbonization precursor obtained in step 3) at high temperature under an inert atmosphere, followed by washing and drying to obtain a nitrogen-doped porous carbon material. The entire process of this invention is relatively simple, the reaction conditions are mild, and it is environmentally friendly. The prepared carbon material has a well-developed pore structure, a high specific surface area, and good electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of carbon material preparation technology, specifically to a nitrogen-doped porous carbon material based on lignite resin and its preparation method. Background Technology

[0002] Due to their abundant pore structure and high specific surface area, porous carbon materials have wide applications in daily life and industrial production, such as the absorption of harmful gases, adsorption of pollutants, and gas storage and separation. Judging from the literature reports of the past fifteen years, especially the last five, the research progress of porous carbon materials in the field of catalysis is accelerating, and the scope of applications is expanding. Furthermore, due to their large specific surface area, research on porous carbon materials as electrode materials for supercapacitors as backup power sources and memory backup devices is also deepening. Known porous carbon materials include activated carbon (AC), activated carbon fiber (ACF), carbon molecular sieves (CMS), and carbon nanotubes (CNTs), which were developed in the 1990s, and more recently, graphene.

[0003] CN110015663 A discloses a method for preparing porous carbon materials based on phenolic resin and its application. Phenolic resin and potassium hydroxide, a traditional activator, are mixed in a certain proportion and then carbonized at high temperature. After washing and drying, porous carbon materials are obtained. This method is simple and easy to operate and implement. However, the traditional activator used is corrosive to the equipment, and the washing process consumes a large amount of aqueous solution and generates a lot of alkaline waste liquid, which is not environmentally friendly.

[0004] CN114516635 A discloses a method for preparing nitrogen-doped porous carbon materials based on coal-based humic acid. This invention uses weathered coal humic acid as the carbon material, potassium-based metal compounds as pore expanders, and urea as a nitrogen source. First, the humic acid is pretreated, and then porous carbon materials are obtained through mechanical stirring, drying, and carbonization. This process is relatively simple and takes into account the characteristics of nitrogen doping. However, this method uses inorganic salts as pore expanders, and the resulting product has a relatively simple pore structure, which affects the electrochemical performance of the carbon material.

[0005] CN110817385 A discloses a method for preparing porous carbon materials based on thermosetting resins. This invention employs an organic polymer phase separation carbonization method, in which a boron source is added to a mixture containing thermosetting resin, organic solvent, and curing agent. The mixture is then heated and cured to obtain the porous carbon material. The thermosetting resin serves as the carbon source, the organic solvent as the pore-forming agent, and the boron source as the complexing agent. The material prepared by this method has a well-developed pore structure, but the process conditions are complex and the experimental cycle is long. Summary of the Invention

[0006] In view of this, the main objective of the present invention is to provide a nitrogen-doped porous carbon material based on lignite resin and its preparation method. The entire process is relatively simple, the reaction conditions are mild and environmentally friendly, and the carbon material prepared has a well-developed pore structure, a high specific surface area and good electrochemical performance.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a method for preparing nitrogen-doped porous carbon materials based on lignite resin, comprising the following steps:

[0008] 1) The ethanol solution of the nitrogen source and the lignite resin were stirred and mixed evenly under heating to obtain mixed solution I;

[0009] 2) Mix the mixed solution I obtained in step 1) with the ethanol solution of the organic salt under heating and stirring until homogeneous to obtain the mixed solution II of lignite resin, nitrogen source and organic salt;

[0010] 3) Dry and solidify the mixed solution II obtained in step 2) to obtain the carbonization precursor;

[0011] 4) The carbonization precursor obtained in step 3) is placed in an inert atmosphere for high-temperature carbonization, washed and dried to obtain nitrogen-doped porous carbon material.

[0012] According to the method of the present invention, the nitrogen source in step 1) is selected from one or a mixture of several of urea, 1,5-naphthyldiamine, o-phenylenediamine, and p-phenylenediamine.

[0013] According to the method of the present invention, the stirring under heating state in step 1) is: stirring at 65-75°C for 20-40 minutes.

[0014] According to the method of the present invention, the mass ratio of lignite resin and nitrogen source in step 1) is 1:0.5 to 3, preferably 1:1 to 2.

[0015] In a specific implementation, the method for preparing the nitrogen source ethanol solution includes: mixing the nitrogen source and ethanol solution in a mass ratio of 1:1 to 4 and stirring at 65 to 75°C for 10 to 15 minutes to obtain a uniformly mixed nitrogen source solution.

[0016] According to the method of the present invention, the stirring under heating state in step 2) is: stirring at 65-75°C for 1-2 hours.

[0017] According to the method of the present invention, the organic salt in step 2) is selected from one or a mixture of several of sodium sorbate, potassium sorbate, sodium acetate, sodium propionate, sodium butyrate, and sodium ethoxide.

[0018] According to the method of the present invention, the mass ratio of lignite resin to organic salt in step 2) is 1:0.5 to 3, preferably 1:1 to 2.

[0019] In a specific implementation, the method for preparing the ethanol solution of the organic salt includes: mixing the organic salt and the ethanol solution in a mass ratio of 1:1 to 4, and stirring at 65 to 75°C for 10 to 15 minutes to make them evenly mixed to obtain the ethanol solution of the organic salt.

[0020] The lignite resin described in this article is a byproduct of lignite wax production. It is inexpensive and readily available. Lignite resin is rich in oxygen-containing functional groups and has a high acid value, which is conducive to the introduction of nitrogen sources and the expansion of pores by organic salts. Furthermore, it has a high content of asphaltenes and gums, and a low content of metals and ash, making it suitable for use as an electrode material after carbonization.

[0021] According to the method of the present invention, the drying and curing in step 3) is: drying and curing at 80-100°C for 8-10 hours.

[0022] According to the method of the present invention, the inert atmosphere in step 4) is one or a mixture of nitrogen, helium and argon, under normal pressure.

[0023] According to the method of the present invention, the high-temperature carbonization in step 4) is as follows: the carbonization temperature is 700-1200℃, preferably 800-1000℃; the carbonization time is 1-6h, preferably 2-4h; and the heating rate is 2-10℃ / min.

[0024] According to the method of the present invention, the washing and drying in step 4) are: washing with ethanol 3 to 6 times and drying at 80 to 100°C.

[0025] In another aspect, the present invention provides a nitrogen-doped porous carbon material based on lignite resin prepared by the above method, with a pore volume of 0.75–1.32 cm³. 3 / g, specific surface area is 290~470m² 2 / g.

[0026] In another aspect, the present invention provides the application of nitrogen-doped porous carbon materials based on lignite resin prepared by the above method as electrode materials for supercapacitors.

[0027] Compared with existing technologies, this invention has the following advantages: It broadens the application range of lignite resin, fully utilizing its high asphaltenes and gum content, abundant oxygen-containing functional groups, and especially its high acid value, which provides more active sites for nitrogen source introduction, increasing the nitrogen content of the product and improving its electrochemical performance. Furthermore, lignite resin has a long carbon chain and good miscibility with non-polar substances. By selecting inexpensive and readily available ethanol as the nitrogen source and activator solvent, and by easily dispersing the components in organic solvents, with ethanol serving as the dispersant for the entire preparation system, and organic salts and amines soluble in ethanol acting as activators and nitrogen sources respectively, the three components can fully contact and mix, which also facilitates pore expansion and nitrogen source introduction, improving the material's electrochemical performance. The nitrogen-doped porous carbon material prepared by this invention has a well-developed pore structure and a high specific surface area, with a pore volume of 0.75–1.32 cm³. 3 / g, specific surface area is 290~470m² 2 When used as an electrode material for supercapacitors, the specific capacitance is 210–340 F / g, and after 1000 charge-discharge cycles, the capacity retention rate is greater than 95%, demonstrating both high specific capacitance and high capacity retention rate.

[0028] Therefore, compared with existing carbon material preparation methods, the raw materials (carbon source, nitrogen source, activator) of this invention are widely available, inexpensive and readily available. In particular, the industrial by-product lignite resin can be used as a carbon source, which can turn waste into treasure, making the entire preparation process have good economic and social benefits. Moreover, the reaction conditions are mild and environmentally friendly, and the preparation process cycle is short, which is conducive to industrial application and can be widely used in the field of electrode materials or energy storage. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments. However, the present invention is not limited to the listed embodiments, but should also include equivalent improvements and modifications of the technical solutions defined in the appended claims of the present invention.

[0030] The endpoints and any values ​​of the ranges disclosed herein 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] In the following examples and comparative examples:

[0032] (1) Main raw materials

[0033] The lignite resin used in this invention is a dark brown solid with an acid value of 45-50, a saponification value of 80-100, and an ash content of ≤0.5wt%.

[0034] Unless otherwise specified, all other raw materials used in this invention are commercially available and are analytical grade reagents.

[0035] (2) Characterization and testing

[0036] The prepared carbon material was mixed with polyvinylidene fluoride binder and acetylene black in a mortar at a ratio of 8:1:1, and ethanol solution was added dropwise to mix thoroughly. The mixture was then repeatedly rolled into a uniform sheet on a tablet press, and the sheet was pressed onto a stainless steel mesh to obtain a working electrode made of lignite resin-based nitrogen-doped porous carbon material. A three-electrode testing system was used, with Hg / HgO as the reference electrode and a platinum electrode sheet as the counter electrode. 6 mol / L KOH was used as the electrolyte to test the cyclic voltammetric characteristics of the prepared carbon material, and the specific capacitance was calculated according to formula ①. When determining the cyclic stability of the prepared carbon material, two electrode sheets with uniform pore size were prepared according to the above pressing method, and a polypropylene film was used as the diaphragm. These sheets were pressed into a circular stainless steel button-type capacitor shell, with nickel foam as the current collector and 6 mol / L KOH as the electrolyte. The cyclic stability was measured, and the corresponding energy density and power density were calculated according to formulas ② and ③.

[0037] Electrochemical performance testing was performed using a CHI660A electrochemical workstation from Shanghai Chenhua Instruments Co., Ltd. For cyclic voltammetry testing, the voltage range of the three-electrode system was -0.8 to 0.2 V, and the scan rate was 5 mV / s. Cyclic stability testing was performed using a BT4 electrochemical analyzer from Arbin Instruments, USA. The charge-discharge voltage range of the two-electrode system was 0 to 1 V, the current density was 1 A / g, and 1000 constant current charge-discharge cycles were conducted. The test results for power density, energy density, and capacity retention are shown in Table 1.

[0038] ①The specific capacitance (mass capacitance) of a material can be calculated from the cyclic voltammetry diagram. The calculation formula is as follows:

[0039]

[0040] For the formula for calculating specific capacitance, ∫|i|dv represents the integral area of ​​the cyclic volt-ampere curve (m²). 2 ); v is the scan rate (V / s); ΔU is the scan voltage window (V); m is the effective mass of the electrode sheet (g).

[0041] ② Energy density Ed=I·ΔU·Δt / (m1+m2);

[0042] ③Power density Pd=3600·Ed / Δt.

[0043] Where I is the discharge current (A); Δt is the time for a complete discharge (s); (m1+m2) is the sum of the effective masses of the two electrodes (g); and ΔU is the voltage window (V).

[0044] By comparing the specific capacitance C1 calculated after 1000 constant current charge-discharge cycles with the specific capacitance C2 calculated at the start of the charge-discharge cycle, the decay of the capacitor's specific capacitance after multiple consecutive charge-discharge cycles can be obtained.

[0045] The following examples illustrate the nitrogen-doped porous carbon material based on lignite resin and its preparation method according to the present invention.

[0046] Example 1

[0047] 50g of urea and 100g of ethanol solution were mixed and mechanically stirred at 70°C for 10 minutes to obtain a uniform urea solution. 50g of lignite resin was added to the urea solution and mechanically stirred at 70°C for 30 minutes to obtain a mixture of urea and lignite resin. 50g of sodium acetate and 100g of ethanol solution were mixed and mechanically stirred at 70°C for 10 minutes to obtain a sodium acetate solution. The mixture of urea and lignite resin was then mixed with the sodium acetate solution and mechanically stirred at 70°C for 1 hour to obtain a mixture of lignite resin, urea, and sodium acetate. The above mixture was then... The mixture was transferred to an oven and dried at 80°C for 8 hours to obtain the dried carbonized precursor. The carbonized precursor was then carbonized at 800°C for 4 hours under a N2 atmosphere. After the furnace had completely cooled, the carbonized material was removed and washed five times with ethanol at a volume three times that of the carbonized material. It was then dried in an oven at 90°C to obtain the final nitrogen-doped porous carbon material. The nitrogen-doped porous carbon material was used to prepare electrode sheets of uniform size and thickness. The corresponding electrochemical performance was tested in a 6 mol / L KOH electrolyte, and the results are shown in Table 1.

[0048] Example 2

[0049] The method of Example 1 was followed, except that 50g of sodium acetate was replaced with an equal mass of sodium propionate, and the results are shown in Table 1.

[0050] Example 3

[0051] The method of Example 1 was followed, except that 50g of sodium acetate was replaced with 100g of sodium sorbate, and the results are shown in Table 1.

[0052] Example 4

[0053] The method of Example 1 was followed, except that 50g of urea was replaced with 100g of urea, and the results are shown in Table 1.

[0054] Example 5

[0055] The method of Example 1 was followed, except that 50g of urea was replaced with 50g of p-phenylenediamine, and the results are shown in Table 1.

[0056] Example 6

[0057] The method of Example 1 was followed, except that the carbonization temperature was changed from 800°C to 1000°C, and the results are shown in Table 1.

[0058] Example 7

[0059] The method of Example 1 was followed, except that the carbonization time was changed from 4 hours to 2 hours, and the results are shown in Table 1.

[0060] Example 8

[0061] The method of Example 1 was followed, except that 50g of sodium acetate and 100g of ethanol were replaced with 150g of sodium ethoxide and 150g of ethanol. The results are shown in Table 1.

[0062] Example 9

[0063] The method of Example 1 was followed, except that 50g of urea and 100g of ethanol were replaced with 150g of urea and 150g of ethanol. The results are shown in Table 1.

[0064] Example 10

[0065] The method of Example 1 was followed, except that 50g of sodium acetate was replaced with 25g of sodium acetate, and the results are shown in Table 1.

[0066] Example 11

[0067] The method of Example 1 was followed, except that 50g of urea was replaced with 25g of urea, and the results are shown in Table 1.

[0068] Example 12

[0069] The method of Example 1 was followed, except that the carbonization temperature was changed from 800°C to 700°C, and the results are shown in Table 1.

[0070] Example 13

[0071] The method of Example 1 was followed, except that the carbonization temperature was changed from 800°C to 1200°C, and the results are shown in Table 1.

[0072] Example 14

[0073] The method of Example 1 was followed, except that the carbonization time was changed from 4 hours to 1 hour, and the results are shown in Table 1.

[0074] Comparative Example 1

[0075] 50g of sodium acetate and 100g of ethanol solution were mixed and mechanically stirred at 70℃ for 10min to obtain an organic salt solution. 50g of lignite resin was added to the organic salt solution and mechanically stirred at 70℃ for 1h to obtain a mixture of lignite resin and sodium acetate. The mixture was transferred to an oven and dried and cured at 80℃ for 8h to obtain the dried carbonization precursor. The carbonization precursor was carbonized at high temperature in a N2 atmosphere at 800℃ for 4h. After the furnace had completely cooled, the carbonized material was removed and washed five times with ethanol at a volume three times that of the carbonized material. It was then dried in an oven at 90℃ to obtain the final nitrogen-doped porous carbon material. The nitrogen-doped porous carbon material was used to prepare electrode sheets of uniform size and thickness. The corresponding electrochemical performance was tested in a 6mol / L KOH electrolyte, and the results are shown in Table 1.

[0076] Comparative Example 2

[0077] 50g of urea and 100g of ethanol solution were mixed and mechanically stirred at 70℃ for 10min to obtain a uniform urea solution. 50g of lignite resin was added to the urea solution and mechanically stirred at 70℃ for 1h to obtain a mixture of urea and lignite resin. The mixture was transferred to an oven and dried and cured at 80℃ for 8h to obtain the dried carbonization precursor. The carbonization precursor was carbonized at high temperature in a N2 atmosphere at 800℃ for 4h. After the furnace had completely cooled, the carbonized material was removed and washed five times with ethanol at a volume three times that of the carbonized material. It was then dried in an oven at 90℃ to obtain the final nitrogen-doped porous carbon material. The nitrogen-doped porous carbon material was used to prepare electrode sheets of uniform size and thickness. The corresponding electrochemical performance was tested in a 6mol / L KOH electrolyte, and the results are shown in Table 1.

[0078] Comparative Example 3

[0079] 50g of lignite resin was mechanically stirred at 90℃ for 30min to obtain a lignite resin liquid. 50g of sodium acetate and 50g of urea were added to the lignite resin liquid and mechanically stirred at 90℃ for 1h to obtain a mixture of organic salt, urea, and lignite resin. The mixture was transferred to an oven and cured at 90℃ for 8h to obtain a carbonization precursor. The carbonization precursor was carbonized at high temperature in a N2 atmosphere at 800℃ for 4h. After the furnace was completely cooled, the carbonized material was removed and washed five times with an ethanol aqueous solution with a volume of 3 times that of the carbonized material. It was then dried in an oven at 90℃ to obtain the final nitrogen-doped porous carbon material. The nitrogen-doped porous carbon material was used to prepare electrode sheets of uniform size and thickness. The corresponding electrochemical performance was tested in a 6mol / L KOH electrolyte. The results are shown in Table 1.

[0080] Comparative Example 4

[0081] 50g of melamine and 100g of ethanol solution were mixed and mechanically stirred at 70℃ for 10 minutes to obtain a mixed solution of melamine and ethanol. 50g of lignite resin was added to the melamine and ethanol mixture and mechanically stirred at 70℃ for 30 minutes to obtain mixture I containing melamine and lignite resin. 50g of sodium tartrate and 100g of ethanol solution were mixed and mechanically stirred at 70℃ for 10 minutes to obtain mixture II containing sodium tartrate and ethanol. Mixture I and mixture II were combined and mechanically stirred at 70℃ for 1 hour to obtain a mixture containing lignite resin and melamine. A mixture of sodium tartrate and ethanol was prepared. The mixture was then transferred to an oven and dried at 80°C for 8 hours to obtain the dried carbonized precursor. The carbonized precursor was then carbonized at 800°C for 4 hours under a N2 atmosphere. After the furnace had completely cooled, the carbonized material was removed and washed five times with ethanol at a volume three times that of the carbonized material. The material was then dried in an oven at 90°C to obtain the final nitrogen-doped porous carbon material. The nitrogen-doped porous carbon material was used to prepare electrode sheets of uniform size and thickness. The corresponding electrochemical performance was tested in a 6 mol / L KOH electrolyte, and the results are shown in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] As can be seen from the data in Table 1 above, the method of the present invention for preparing nitrogen-doped porous carbon materials based on lignite resin uses ethanol-soluble amines and organic salts as nitrogen sources and activators, respectively, with ethanol as a dispersant to mix the three components uniformly. First, lignite resin and amines are mixed at a specific mass ratio (1:1–2). Then, this mixture is mixed with a certain mass (lignite resin to organic salt mass ratio of 1:1–2) of organic salt to obtain a uniformly mixed solution, which is then cured to obtain a carbonization precursor. Carbonization is carried out at a specific carbonization temperature (800–1000℃) for a certain time (2–4 h). The prepared carbon material has a well-developed pore structure, a high specific surface area, and good electrochemical performance (see specific capacitance, power density, energy density, and capacity retention data). Comparative Example 1 differs from Example 1 mainly in that no nitrogen source was introduced, and the results confirm that the pore structure and electrochemical performance of the product could not reach a satisfactory level. Comparative Example 2 differs from Example 1 primarily in that it did not use an organic salt as an activator. The results confirmed that the prepared material had lower pore volume and specific surface area, and its electrochemical performance was weaker than that of Example 1. Comparative Example 3 differs from Example 1 primarily in that it did not use ethanol as a dispersant in the entire reaction system. As a result, the pore structure and electrochemical performance of the prepared material did not reach a satisfactory level. Comparative Example 4 differs from Example 1 primarily in that it used melamine (insoluble in ethanol) as the nitrogen source and sodium tartrate as the organic salt. As a result, the pore structure and electrochemical performance of the prepared material did not reach a superior level. Compared to Example 1, Examples 8, 9, and 13 differed in the amount of organic salt, nitrogen source, or carbonization temperature. The resulting product performance improvement was less significant than in Example 1, and system energy consumption increased to some extent. Increased organic salt content facilitated macroporous structure formation, but reduced specific surface area, hindering specific capacitance increase. Higher nitrogen content increased pseudocapacitance, thus increasing specific capacitance, but decreased capacitance retention. Higher carbonization temperature promoted graphitization, increasing conductivity and reducing pore size and electrolyte ion transport resistance, but reduced surface nitrogen content, hindering nitrogen source introduction and specific capacitance increase. Examples 10, 11, 12, and 14, compared to Example 1, differed in the amount of organic salt, urea, carbonization temperature, or carbonization time. The resulting materials exhibited less developed pore structures and inferior electrochemical performance compared to Example 1.

[0086] The experimental results of Examples 1-14 show that Examples 1-7, compared with other examples, simultaneously meet the following conditions: organic salts and amines soluble in ethanol are selected as activators and nitrogen sources, respectively; in the mixture of ethanol, lignite resin, organic salt, and amine, the mass ratio of lignite resin to organic salt is 1:1 to 1:2, and the mass ratio of lignite resin to amine is 1:1 to 1:2; after the above-mentioned ethanol solution containing carbon source, activator, and nitrogen source is mixed evenly, it is cured in an oven for a period of time; after curing, the carbonization precursor obtained is carbonized at a temperature of 800-1000℃ and a carbonization time of 2-4h under an inert atmosphere; the lignite resin-based nitrogen-doped porous carbon material prepared by the above method has the characteristics of well-developed pore structure and excellent electrochemical performance. As shown in other embodiments 8-14, changing any parameter range in the above methods so that it is outside the preferred range of the present invention, or changing the addition and type of raw materials as shown in comparative examples 1-4, lacking any one of nitrogen source, organic salt activator and ethanol dispersant, will prevent the prepared nitrogen-doped porous carbon material from achieving optimal performance. It can be seen that the selection of raw materials and their preferred dosage, the setting of carbonization parameters and other factors, as well as the mutual cooperation between the factors in the above methods of embodiments 1-7 of the present invention, all play a key role in achieving the effect of the present invention.

[0087] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are within the spirit and scope of the present invention.

Claims

1. A method for preparing nitrogen-doped porous carbon materials based on lignite resin, characterized in that: Includes the following steps: 1) The ethanol solution of the nitrogen source and the lignite resin were stirred and mixed evenly under heating to obtain mixed solution I; 2) Mix the mixed solution I obtained in step 1) with the ethanol solution of the organic salt under heating and stirring until homogeneous to obtain a mixed solution II of lignite resin, nitrogen source and organic salt; wherein the organic salt is selected from one or a mixture of several of sodium sorbate, potassium sorbate, sodium acetate, sodium propionate, sodium butyrate and sodium ethoxide. 3) Dry and solidify the mixed solution II obtained in step 2) to obtain the carbonized precursor; 4) The carbonization precursor obtained in step 3) is placed in an inert atmosphere for high-temperature carbonization, washed and dried to obtain nitrogen-doped porous carbon material.

2. The method for preparing nitrogen-doped porous carbon material according to claim 1, characterized in that: The nitrogen source mentioned in step 1) is selected from one or a mixture of several of urea, 1,5-naphthyldiamine, o-phenylenediamine, and p-phenylenediamine.

3. The method for preparing nitrogen-doped porous carbon material according to claim 1, characterized in that: The stirring under heating conditions described in step 1) is: stirring at 65~75℃ for 20~40 minutes; and / or, the stirring under heating conditions described in step 2) is: stirring at 65~75℃ for 1~2 hours.

4. The method for preparing nitrogen-doped porous carbon material according to claim 1 or 2, characterized in that: The mass ratio of lignite resin and nitrogen source in step 1) is 1:0.5~3.

5. The method for preparing nitrogen-doped porous carbon material according to claim 4, characterized in that: The mass ratio of lignite resin and nitrogen source in step 1) is 1:1~2.

6. The method for preparing nitrogen-doped porous carbon material according to claim 1, characterized in that: The mass ratio of lignite resin to organic salt in step 2) is 1:0.5~3.

7. The method for preparing nitrogen-doped porous carbon material according to claim 6, characterized in that: The mass ratio of lignite resin to organic salt in step 2) is 1:1~2.

8. The method for preparing nitrogen-doped porous carbon material according to claim 1, characterized in that: The drying and curing process described in step 3) is as follows: drying and curing at 80~100℃ for 8~10 hours.

9. The method for preparing nitrogen-doped porous carbon material according to claim 1, characterized in that: The high-temperature carbonization described in step 4) is as follows: carbonization temperature is 700~1200℃; carbonization time is 1~6h; and heating rate is 2~10℃ / min.

10. The method for preparing nitrogen-doped porous carbon material according to claim 9, characterized in that: The high-temperature carbonization described in step 4) is as follows: carbonization temperature is 800~1000℃; carbonization time is 2~4h.

11. A nitrogen-doped porous carbon material based on lignite resin prepared by the method of any one of claims 1-10.

12. The application of the nitrogen-doped porous carbon material based on lignite resin prepared by the method of any one of claims 1-10, as an electrode material for a supercapacitor.

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