Hard carbon anode materials and their preparation methods, nitrogen-containing asphalt coatings, sodium-ion batteries

Abstract

This application applies to the field of new energy materials technology, providing hard carbon anode materials and their preparation methods, nitrogen-containing asphalt coatings, and sodium-ion batteries. The method includes: nitrogen-doping asphalt to obtain nitrogen-containing asphalt coatings; uniformly mixing pre-carbonized biomass powder with the nitrogen-containing asphalt coatings; and sintering the resulting mixed powder to obtain the hard carbon anode material. By doping the asphalt with nitrogen, the asphalt exhibits a larger carbon interlayer spacing after high-temperature sintering, providing sodium storage sites and facilitating rapid sodium ion migration. This improves the material's initial charge-discharge efficiency and hydrophobicity without affecting specific capacity and rate performance. Furthermore, the pre-carbonization of biomass allows for the uniform adsorption of small coating particles onto the main material. The highly graphitized coating layer formed during high-temperature sintering exhibits stronger hydrophobicity and fewer defect sites, transforming the open-pore structure into a closed-pore structure, thereby improving its initial charge-discharge efficiency, specific capacity, and cycle performance as a sodium battery anode.

Description

Technical Field

[0001] This application belongs to the field of new energy materials technology, and in particular relates to a hard carbon anode material and its preparation method, nitrogen-containing asphalt coating, and sodium-ion battery. Background Technology

[0002] Biomass-based hard carbon boasts advantages such as wide availability of raw materials, low cost, and high specific capacity, making it the most promising anode material for sodium-ion batteries. However, its performance is still limited by its relatively low initial charge-discharge efficiency. Biomass contains abundant oxygen, and its derived hard carbon inevitably contains a large number of oxygen-containing functional groups, exhibiting good hydrophilicity. Since anodes are generally fabricated using aqueous slurries, water absorption by the material can lead to the generation of large amounts of gas during battery cycling, impairing battery cycle life and posing safety hazards.

[0003] Existing technologies employ asphalt coating of negative electrode powder to further improve electrochemical performance and reduce material hydrophilicity. However, asphalt carbonization at lower temperatures results in numerous defects, failing to meet the requirements for improving initial charge-discharge efficiency. High-temperature sintering leads to high graphitization, hindering rapid sodium ion insertion and significantly negatively impacting the material's specific capacity and rate performance. Furthermore, direct carbon coating results in powder agglomeration and uneven coating. Summary of the Invention

[0004] In view of this, the present application provides a method for preparing hard carbon anode material, which aims to solve the problems of existing methods for coating anode powder with asphalt, such as powder agglomeration, uneven coating, inability to meet the requirements for improving the first charge and discharge efficiency, and significant negative impact on the specific capacity and rate performance of the material.

[0005] The first aspect of this application provides a method for preparing a hard carbon anode material, including:

[0006] Nitrogen-added asphalt is treated to obtain nitrogen-containing asphalt coatings;

[0007] The pre-carbonized biomass powder is mixed evenly with the nitrogen-containing asphalt coating, and the resulting mixed powder is sintered to obtain a hard carbon anode material.

[0008] In one possible implementation of the first aspect, the nitrogen-doping treatment of asphalt to obtain a nitrogen-containing asphalt coating includes:

[0009] After the asphalt is crushed, it is treated with plasma to obtain a nitrogen-containing asphalt coating.

[0010] In the plasma treatment, the nitrogen gas flow rate is 40-100 mL / min, the power is 200-300 W, the reaction temperature is 25-300 ℃, and the treatment time is 1-2 h.

[0011] In another possible implementation of the first aspect, the nitrogen-doping treatment of the asphalt to obtain a nitrogen-containing asphalt coating includes:

[0012] The asphalt is mixed with a nitrogen source and then subjected to heat treatment to obtain a nitrogen-containing asphalt coating.

[0013] The nitrogen source content is 2-10%, the heat treatment temperature is 200-280℃, and the heat treatment time is 3-6h.

[0014] In another possible implementation of the first aspect, the nitrogen-doping treatment of the asphalt to obtain a nitrogen-containing asphalt coating includes:

[0015] The asphalt is mixed with a nitrogen source and then ball-milled, or the asphalt is ball-milled in a nitrogen-containing gas atmosphere to obtain a nitrogen-containing asphalt coating; wherein the nitrogen source content is 2-10%; when the nitrogen source content is 2-5%, the ball milling time is 6-24h; when the nitrogen source content is 5-10%, the ball milling time is 6-12h.

[0016] The second aspect of this application provides a hard carbon anode material, which is prepared by the preparation method of the hard carbon anode material described in the first aspect above.

[0017] A third aspect of this application provides a nitrogen-containing bitumen coating as described in the first aspect above.

[0018] A fourth aspect of this application provides a sodium-ion battery, characterized in that the sodium-ion battery includes the hard carbon anode material described in the second aspect above.

[0019] The method for preparing hard carbon anode material provided in this application involves nitrogen doping of asphalt, resulting in a larger carbon interlayer spacing after high-temperature sintering. This provides sodium storage sites and facilitates the rapid migration of sodium ions, improving the initial charge-discharge efficiency and hydrophobicity of the material without affecting specific capacity and rate performance. Furthermore, the pre-carbonized biomass precursor has abundant open pore structure and a large specific surface area. High-speed mixing with the coating material further promotes the uniform adsorption of small particles of the coating material on the host material, reducing powder agglomeration. During high-temperature sintering, the abundant carbon and hydrogen elements in the asphalt can reduce the oxygen-containing functional groups in the pre-carbonized precursor, forming a highly graphitized coating layer with stronger hydrophobicity and fewer defect sites. At the same time, it transforms the open pore structure into a closed pore structure, improving the initial charge-discharge efficiency, specific capacity, and cycle performance of the material as a sodium-ion battery anode. Attached Figure Description

[0020] Figure 1 The first charge-discharge curve of the hard carbon anode material provided in Comparative Example 1 of this application;

[0021] Figure 2 The first charge-discharge curve of the hard carbon anode material provided in Comparative Example 2 of this application;

[0022] Figure 3 The first charge-discharge curve of the hard carbon anode material provided in Comparative Example 3 of this application;

[0023] Figure 4 This is the first charge-discharge curve of the hard carbon anode material provided in Example 1 of this application;

[0024] Figure 5 This is the first charge-discharge curve of the hard carbon anode material provided in Example 7 of this application;

[0025] Figure 6 The first charge-discharge curve of the hard carbon anode material provided in Example 12 of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] This application provides a method for preparing a hard carbon anode material, including the following steps:

[0028] Step S1: Nitrogen-doped asphalt is used to obtain nitrogen-containing asphalt coating.

[0029] In this embodiment, asphalt is rapidly pulverized and then subjected to nitrogen doping treatment to obtain a nitrogen-containing asphalt coating; the particle size distribution D of the pulverized asphalt... 50 The nitrogen doping range is 0.2–2 μm. Nitrogen doping methods include, but are not limited to, plasma treatment, chemical doping, and physical-mechanical doping.

[0030] Preferably, the plasma nitrogen doping treatment method is as follows: after the asphalt is crushed, it is placed in a plasma chamber, and high-purity nitrogen is introduced at a gas flow rate of 40-100 mL / min, with a power of 200-300 W, a reaction temperature of 25-300℃, a heating rate of 2-5℃ / min, and plasma treatment is carried out for 1-2 hours to obtain a nitrogen-containing asphalt coating. The plasma instrument used in the embodiments of this application is a FURNACE 1200.

[0031] Preferably, the chemical nitrogen doping treatment method involves mixing asphalt with a nitrogen-containing compound and then subjecting it to heat treatment to obtain a nitrogen-containing asphalt coating. The nitrogen source content is preferably 2-10%, i.e., the mass ratio of asphalt to the nitrogen-containing compound is 10:(0.2-1); the nitrogen-containing compound can be urea, ammonium carbonate, ammonium nitrate, etc.; the heat treatment temperature is 200-280℃, and the heat treatment time is 3-6 hours.

[0032] Preferably, the physical-mechanical nitrogen doping treatment method involves mixing asphalt with a nitrogen-containing compound and then ball milling it, or ball milling the asphalt under a nitrogen-containing gas atmosphere to obtain a nitrogen-containing asphalt coating. The nitrogen source is a nitrogen-containing compound or a nitrogen-containing gas, with the nitrogen source amount preferably being 2-10%, i.e., the mass ratio of asphalt to the nitrogen-containing compound is 10:(0.2-1). The nitrogen-containing compound can be urea, ammonium carbonate, ammonium nitrate, etc., and the nitrogen-containing gas can be nitrogen, ammonia, etc. During ball milling, the ball-to-material ratio is (500-200):50, and the ball milling speed is 400-600 r / min. When the nitrogen source amount is 2-5%, the ball milling time is 6-24 h; when the nitrogen source amount is 5-10%, the ball milling time is 6-12 h.

[0033] It is worth noting that this application, by first treating the asphalt with nitrogen before subsequent coating treatment, avoids damaging the coating layer compared to coating first and then nitrogen doping, and better protects the hard carbon material itself. This application achieves nitrogen doping through the aforementioned plasma treatment, chemical doping, or physical-mechanical doping methods, resulting in a larger carbon interlayer spacing after high-temperature sintering of the asphalt. This provides sodium storage sites and facilitates the rapid migration of sodium ions, improving the material's initial charge-discharge efficiency and hydrophobicity without affecting specific capacity and rate performance.

[0034] During plasma treatment, when the nitrogen source content increases from 2% to 15%, or the gas flow rate gradually increases from 40 mL / min to 150 mL / min, or the plasma power gradually increases from 200 W to 400 W, or the treatment temperature gradually increases from 25℃ to 400℃, or the treatment time gradually increases from 1 h to 4 h, the nitrogen content of the hard carbon gradually increases, the uniformity of the coating thickness deteriorates, and the disorder becomes too large, resulting in a gradual decrease in the initial coulombic efficiency of the obtained product and a gradual deterioration in the hydrophobic properties. Therefore, the gas flow rate is preferably 40-100 mL / min, the power is preferably 200-300 W, the temperature is preferably 25-300℃, and the time is preferably 1-2 h.

[0035] During the chemical nitrogen doping process, when the nitrogen source amount increases from 2% to 15%, or the temperature increases from 200℃ to 400℃, or the treatment time increases from 3h to 12h, the nitrogen content of hard carbon gradually increases, the uniformity of the coating thickness deteriorates, and the disorder becomes too large, resulting in a gradual decrease in the initial coulombic efficiency of the obtained product and a gradual deterioration in hydrophobic properties. Therefore, the nitrogen source amount is preferably 2%-10%, the temperature is preferably 200℃-280℃, and the treatment time is preferably 3-6h.

[0036] During the physical ball milling process, when the nitrogen source content increases from 2% to 15%, or when the nitrogen source content is 5-10%, and the processing time increases from 6h to 24h, the nitrogen content of the hard carbon gradually increases, the uniformity of the coating thickness deteriorates, and the disorder becomes too large, resulting in a gradual decrease in the initial coulombic efficiency of the obtained product and a gradual deterioration in the hydrophobic properties. Therefore, the nitrogen source content is preferably 2%-10%; when the nitrogen source content is 5-10%, the processing time is preferably 6-12h.

[0037] Step S2: Mix the pre-carbonized biomass powder with the nitrogen-containing asphalt coating material evenly, and sinter the resulting mixed powder to obtain hard carbon anode material.

[0038] In this embodiment, the mass ratio of the pre-carbonized biomass powder to the nitrogen-containing asphalt coating is 10:(0.2-1). Structural characterization shows that the coating thickness of the negative electrode material is 0.2–100 nm.

[0039] In this embodiment of the application, before the step of uniformly mixing the pre-carbonized biomass powder with the nitrogen-containing asphalt coating and sintering the resulting mixed powder to obtain the hard carbon anode material, the method includes: placing the biomass in an inert gas atmosphere and pre-carbonizing it at a temperature of 400-800℃ for 2-6 hours, followed by crushing. The biomass can be bamboo or wood, etc. Although this embodiment uses bamboo as an example, it should not be used to limit the scope of protection of this application. Those skilled in the art can conceive of using other biomass materials to replace the bamboo in the embodiment. The inert gas can be argon or nitrogen, and the heating rate can be 2-5℃ / min; the particle size distribution D50 of the crushed pre-carbonized biomass is 5-10 μm. The pre-carbonized biomass precursor has a rich open pore structure and a large specific surface area, which is more conducive to the uniform adsorption of small particles of the coating under high-speed mixing and reduces powder agglomeration.

[0040] In this embodiment, the sintering treatment of the obtained mixed powder to obtain a hard carbon anode material includes: placing the mixed powder in an inert gas atmosphere and sintering it at a temperature of 1100–1500°C for 2–6 hours to obtain the hard carbon anode material. The inert gas can be argon or nitrogen, and the heating rate can be 2–10°C / min. During the high-temperature sintering process, the abundant carbon and hydrogen elements in the asphalt can reduce the oxygen-containing functional groups in the pre-carbonized precursor, forming a highly graphitized coating layer with stronger hydrophobicity and fewer defect sites. Simultaneously, it transforms the open-pore structure into a closed-pore structure, improving the material's initial charge-discharge efficiency, specific capacity, and cycle performance.

[0041] The following detailed description of nitrogen-containing asphalt coatings, hard carbon anode materials, and sodium-ion batteries uses specific embodiments, as shown below. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; and the materials and reagents used are commercially available unless otherwise specified.

[0042] Example 1

[0043] The preparation method of nitrogen-containing asphalt coating and hard carbon anode material provided in this embodiment includes the following steps:

[0044] Step S1: Take 100g of dried bamboo, remove the skin, mechanically crush it into powder, pass it through a 100-mesh sieve, and dry it in a forced-air drying oven at 80℃ for 12 hours to obtain bamboo powder precursor.

[0045] Step S2: The bamboo powder obtained in step S1 is pre-carbonized in a box furnace at a carbonization temperature of 600℃, a heating rate of 100℃ / h, a holding time of 2h, and an argon atmosphere. After natural cooling, about 30g of pre-carbonized precursor is obtained.

[0046] Step S3: The pre-carbonized precursor obtained in step S2 is crushed at high speed to control the particle size distribution D50 to 5 μm.

[0047] Step S4: Crush the petroleum asphalt at high speed and control the particle size distribution D50 to 2um.

[0048] Step S5: Place the asphalt obtained in step S4 into the plasma chamber, introduce high-purity nitrogen at a rate of 40 mL / min, and maintain the plasma power at 200 W for 2 hours at 280 °C to obtain nitrogen-containing asphalt coating.

[0049] Step S6: Take 20g of the precarbonized precursor prepared in step S3 and 1g of the nitrogen-containing asphalt coating obtained in step S5 and mix them at high speed.

[0050] Step S7: The mixed powder obtained in step S5 is sintered at high temperature in a tube furnace at a temperature of 1300℃, a heating rate of 100℃ / h, an argon atmosphere, and a holding time of 2h. After natural cooling, hard carbon anode material is obtained.

[0051] Example 2

[0052] The experimental procedure was the same as in Example 1, but the plasma chamber was kept at room temperature.

[0053] Example 3

[0054] The experimental procedure was the same as in Example 1, but high-purity nitrogen was introduced at a rate of 100 mL / min.

[0055] Example 4

[0056] The experimental procedure was the same as in Example 1, but the plasma power was 300W.

[0057] Example 5

[0058] The experimental procedure was the same as in Example 1, but the plasma holding time was 1 hour.

[0059] Example 6

[0060] The experimental procedure was the same as in Example 1, but high-purity nitrogen was introduced at a rate of 80 mL / min.

[0061] Example 7

[0062] The experimental procedure is the same as in Example 1, but the plasma cavity temperature is kept at 200°C.

[0063] Example 8

[0064] The preparation method of nitrogen-containing asphalt coating and hard carbon anode material provided in this embodiment includes the following steps:

[0065] Step S1: Take 100g of dried bamboo, remove the skin, mechanically crush it into powder, pass it through a 100-mesh sieve, and dry it in a forced-air drying oven at 80℃ for 12 hours to obtain bamboo powder precursor.

[0066] Step S2: The bamboo powder obtained in step S1 is pre-carbonized in a box furnace at a carbonization temperature of 600℃, a heating rate of 100℃ / h, a holding time of 2h, and an argon atmosphere. After natural cooling, about 30g of pre-carbonized precursor is obtained.

[0067] Step S3: The pre-carbonized precursor obtained in step S2 is crushed at high speed to control the particle size distribution D50 to 5 μm.

[0068] Step S4: Mix petroleum asphalt and urea at a mass ratio of 50:1, place them in a ball mill jar, with a ball-to-material ratio of 250:50, and ball mill for 12 hours. After ball milling, remove the mixture and crush it at high speed. The particle size distribution D50 is 2 μm.

[0069] Step S5: Take 20g of the precarbonized precursor prepared in step S3 and 1g of the nitrogen-containing asphalt coating obtained in step S4 and mix them at high speed.

[0070] Step S6: The mixed powder obtained in step S5 is sintered at high temperature in a tube furnace at a temperature of 1300℃, a heating rate of 100℃ / h, an argon atmosphere, and a holding time of 2h. After natural cooling, hard carbon anode material is obtained.

[0071] Example 9

[0072] The experimental procedure was the same as in Example 8, but petroleum asphalt and urea were mixed at a mass ratio of 20:1.

[0073] Example 10

[0074] The experimental procedure was the same as in Example 8, but petroleum asphalt and urea were mixed at a mass ratio of 10:1.

[0075] Example 11

[0076] The experimental procedure was the same as in Example 9, but the ball milling time was 6 hours.

[0077] Example 12

[0078] The experimental procedure was the same as in Example 9, but the ball milling time was 24 hours.

[0079] Example 13

[0080] The preparation method of nitrogen-containing asphalt coating and hard carbon anode material provided in this embodiment includes the following steps:

[0081] Step S1: Take 100g of dried bamboo, remove the skin, mechanically crush it into powder, pass it through a 100-mesh sieve, and dry it in a forced-air drying oven at 80℃ for 12 hours to obtain bamboo powder precursor.

[0082] Step S2: The bamboo powder obtained in step S1 is pre-carbonized in a box furnace at a carbonization temperature of 600℃, a heating rate of 100℃ / h, a holding time of 2h, and an argon atmosphere. After natural cooling, about 30g of pre-carbonized precursor is obtained.

[0083] Step S3: The pre-carbonized precursor obtained in step S2 is crushed at high speed to control the particle size distribution D50 to 5 μm.

[0084] Step S4: Mix petroleum asphalt and urea at a mass ratio of 50:1, heat-treat in a tube furnace under an argon atmosphere for 3 hours at a temperature of 280℃ and a heating rate of 5℃ / min, and then crush at high speed after natural cooling. The particle size distribution D50 is 2μm.

[0085] Step S5: Take 20g of the precarbonized precursor prepared in step S2 and 1g of the nitrogen-containing asphalt coating obtained in step S4 and mix them at high speed.

[0086] Step S6: The mixed powder obtained in step S5 is sintered at high temperature in a tube furnace at a temperature of 1300℃, a heating rate of 100℃ / h, an argon atmosphere, and a holding time of 2h. After natural cooling, hard carbon anode material is obtained.

[0087] Example 14

[0088] The experimental procedure was the same as in Example 8, but petroleum asphalt and urea were mixed at a mass ratio of 20:1.

[0089] Example 15

[0090] The experimental procedure was the same as in Example 8, but petroleum asphalt and urea were mixed at a mass ratio of 10:1.

[0091] Example 16

[0092] The experimental steps are the same as in Example 14, but the heat treatment time is 6 hours.

[0093] Example 17

[0094] The experimental procedure is the same as in Example 14, but the heat treatment temperature is 250℃.

[0095] Example 18

[0096] The experimental procedure is the same as in Example 14, but the heat treatment temperature is 200℃.

[0097] Example 19

[0098] The experimental steps are the same as in Example 1, but step S6 is: take 20g of the precarbonized precursor prepared in step S3 and mix it at high speed with 0.4g of the nitrogen-containing asphalt coating obtained in step S5.

[0099] Example 20

[0100] The experimental steps are the same as in Example 1, but step S6 is: take 20g of the precarbonized precursor prepared in step S3 and 2g of the nitrogen-containing asphalt coating obtained in step S5 and mix them at high speed.

[0101] Comparative Example 1

[0102] The preparation method of the hard carbon anode material provided in this embodiment includes the following steps:

[0103] Step S1: Take 100g of dried bamboo, remove the skin, mechanically crush it into powder, pass it through a 100-mesh sieve, and dry it in a forced-air drying oven at 80℃ for 12 hours to obtain bamboo powder precursor.

[0104] Step S2: The bamboo powder obtained in step S1 is pre-carbonized in a box furnace at a carbonization temperature of 600℃, a heating rate of 100℃ / h, a holding time of 2h, and an argon atmosphere. After natural cooling, about 35g of pre-carbonized precursor is obtained.

[0105] Step S3: The pre-carbonized precursor obtained in step S2 is sintered at high temperature in a tube furnace at 1300℃, with an argon atmosphere, a heating rate of 100℃ / h, a holding time of 2h, and natural cooling to obtain approximately 25g of hard carbon anode material.

[0106] Step S4: The hard carbon anode material obtained in step S3 is crushed at high speed to control the particle size distribution D50 to 5 μm.

[0107] Comparative Example 2

[0108] The preparation method of the hard carbon anode material provided in this embodiment includes the following steps:

[0109] Step S1: Take 100g of dried bamboo, remove the skin, mechanically crush it into powder, pass it through a 100-mesh sieve, and dry it in a forced-air drying oven at 80℃ for 12 hours to obtain bamboo powder precursor.

[0110] Step S2: The bamboo powder obtained in step S1 is pre-carbonized in a box furnace at a carbonization temperature of 600℃, a heating rate of 100℃ / h, a holding time of 2h, and an argon atmosphere. After natural cooling, about 35g of pre-carbonized precursor is obtained.

[0111] Step S3: The pre-carbonized precursor obtained in step S2 is sintered at high temperature in a tube furnace at a temperature of 1300℃, a heating rate of 100℃ / h, an argon atmosphere, and a holding time of 2h. After natural cooling, approximately 25g of hard carbon material is obtained.

[0112] Step S4: The hard carbon material obtained in step S3 is crushed at high speed, and the particle size distribution D50 is controlled to be 5 μm.

[0113] Step S5: Crush the petroleum asphalt at high speed and control the particle size distribution D50 to 2um.

[0114] Step S6: Take 20g of the precarbonized precursor prepared in step S4 and 1g of the asphalt obtained in step S5 and mix them at high speed.

[0115] Step S7: The mixed powder obtained in step S6 is sintered at high temperature in a tube furnace at 800℃, with a heating rate of 100℃ / h, an argon atmosphere, and a holding time of 2h. After natural cooling, hard carbon anode material is obtained.

[0116] Comparative Example 3

[0117] The preparation method of the hard carbon anode material provided in this embodiment includes the following steps:

[0118] Step S1: Take 100g of dried bamboo, remove the skin, mechanically crush it into powder, pass it through a 100-mesh sieve, and dry it in a forced-air drying oven at 80℃ for 12 hours to obtain bamboo powder precursor.

[0119] Step S2: The bamboo powder obtained in step S1 is pre-carbonized in a box furnace at a carbonization temperature of 600℃, a heating rate of 100℃ / h, a holding time of 2h, and an argon atmosphere. After natural cooling, about 30g of pre-carbonized precursor is obtained.

[0120] Step S3: The pre-carbonized precursor obtained in step S2 is crushed at high speed to control the particle size distribution D50 to 5 μm.

[0121] Step S4: Crush the petroleum asphalt at high speed and control the particle size distribution D50 to 2um.

[0122] Step S5: Take 20g of the precarbonized precursor prepared in step S3 and 1g of the asphalt obtained in step S4 and mix them at high speed.

[0123] Step S6: The mixed powder obtained in step S5 is sintered at high temperature in a tube furnace at a temperature of 1300℃, a heating rate of 100℃ / h, an argon atmosphere, and a holding time of 2h. After natural cooling, hard carbon anode material is obtained.

[0124] Comparative Example 4

[0125] The experimental procedure was the same as in Example 1, but the plasma chamber temperature was kept at 400°C.

[0126] Comparative Example 5

[0127] The experimental procedure was the same as in Example 1, but high-purity nitrogen was introduced at a rate of 150 mL / min.

[0128] Comparative Example 6

[0129] The experimental procedure was the same as in Example 1, but the plasma power was 400W.

[0130] Comparative Example 7

[0131] The experimental procedure was the same as in Example 1, but the plasma holding time was 4 hours.

[0132] Comparative Example 8

[0133] The experimental procedure was the same as in Example 10, but the ball milling time was 24 hours.

[0134] Comparative Example 9

[0135] The experimental procedure was the same as in Example 9, but petroleum asphalt and urea were mixed at a mass ratio of 5:1.

[0136] Comparative Example 10

[0137] The experimental procedure was the same as in Example 14, but petroleum asphalt and urea were mixed at a mass ratio of 5:1.

[0138] Comparative Example 11

[0139] The experimental procedure was the same as in Example 14, but the heat treatment time was 12℃.

[0140] Comparative Example 12

[0141] The experimental procedure was the same as in Example 14, but the heat treatment temperature was 400℃.

[0142] Comparative Example 13

[0143] The experimental steps are the same as in Example 2, but step S6 is: take 20g of the precarbonized precursor prepared in step S3 and 3g of the nitrogen-containing asphalt coating obtained in step S5 and mix them at high speed.

[0144] Five groups of samples were randomly selected from the hard carbon anode materials prepared in Examples 1-20 and Comparative Examples 1-13, respectively. The thickness of the coating layer and the carbon layer spacing of the coating layer were measured by transmission electron microscopy (TEM) for 2 mg of each group. The results are shown in Table 1-2.

[0145] Table 1

[0146]

[0147]

[0148] Table 2

[0149]

[0150] Furthermore, the hard carbon anode materials prepared in Examples 1-20 and Comparative Examples 1-13 were used as active materials for the preparation of sodium-ion batteries: 184 mg of carbon material powder, 6 mg of conductive carbon black, 6 mg of 2% (w / w) carboxymethyl cellulose solution, and 17.5 mg of 40% (w / w) styrene-butadiene rubber were weighed according to a mass ratio of 92%:3%:1.5%:3.5%. An appropriate amount of deionized water was added, and the mixture was stirred for 20 min until a uniform slurry was formed. The slurry was then uniformly coated onto the surface of a copper (Cu) foil using a 100 μm scraper. The slurry was dried in a 105°C forced-air drying oven for 2 h. The Cu foil containing the active material was then cut into circular anode sheets and transferred to a glove box for later use. The simulated battery assembly was carried out in a MIKROUNA glove box filled with Ar atmosphere. The prepared carbon material electrode was used as the negative electrode, the commercial electrolyte 1.0 mol / L NaPF6 / EC:DMC (1:1) (V:V) was used as the electrolyte, and a Na metal sheet was used as the counter electrode. A 2016 coin cell was assembled. The battery performance test results are shown in Table 3-6.

[0151] in, Figure 1-3 The first charge-discharge curves of the hard carbon anode materials provided in Comparative Examples 1-3 are shown in Figures 4-6, respectively.

[0152] Table 3

[0153]

[0154]

[0155] Table 4

[0156]

[0157] Table 5

[0158]

[0159] Table 6

[0160]

[0161] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0162] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a hard carbon negative electrode material, characterized by, The preparation method of the hard carbon negative electrode material comprises the following steps: nitrogen-doped asphalt is obtained, and the pre-carbonized biomass powder and the nitrogen-doped asphalt coating are uniformly mixed; the obtained mixed powder is sintered to obtain the hard carbon negative electrode material; the mass ratio of the pre-carbonized biomass powder to the nitrogen-doped asphalt coating is 10:(0.2-1); The nitrogen-doped asphalt coating is obtained by any one of the following methods: Method one: the asphalt is crushed and then subjected to plasma treatment to obtain the nitrogen-doped asphalt coating; in the plasma treatment, the nitrogen gas flow rate is 40-100 mL / min, the power is 200-300 W, the reaction temperature is 25-300 DEG C, and the treatment time is 1-2 h; Method two: the asphalt is mixed with a nitrogen source and then subjected to heat treatment to obtain the nitrogen-doped asphalt coating; the amount of the nitrogen source is 2-10%, the heat treatment temperature is 200-280 DEG C, and the heat treatment time is 3-6 h; Method three: the asphalt is mixed with a nitrogen source and then subjected to ball milling, or the asphalt is subjected to ball milling in a nitrogen-containing gas atmosphere to obtain the nitrogen-doped asphalt coating; the amount of the nitrogen source is 2-10%; when the amount of the nitrogen source is 2-5%, the ball milling time is 6-24 h, and when the amount of the nitrogen source is 5-10%, the ball milling time is 6-12 h.

2. The method for preparing the hard carbon anode material according to claim 1, characterized in that, Before the step of mixing the pre-carbonized biomass powder with the nitrogen-doped asphalt coating and uniformly mixing the mixture, the biomass is crushed after being pre-carbonized at a temperature of 400-800 DEG C for 2-6 h in an inert gas atmosphere.

3. The method for preparing the hard carbon anode material according to claim 1, characterized in that, The sintering treatment of the mixed powder to obtain the hard carbon negative electrode material comprises the following steps: the mixed powder is placed in an inert gas atmosphere and sintered at a temperature of 1100-1500 DEG C for 2-6 h to obtain the hard carbon negative electrode material.

4. A hard carbon negative electrode material, characterized by, The hard carbon negative electrode material is prepared by the preparation method of the hard carbon negative electrode material according to any one of claims 1-3.

5. A sodium-ion battery, characterized in that, The sodium ion battery comprises the hard carbon negative electrode material according to claim 4.

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