Preparation method of asphalt-based hard carbon negative electrode material

Abstract

The application discloses a preparation method of a pitch-based hard carbon negative material in the technical field of batteries, and comprises the following steps: step 1) taking pitch and carbon material, and transferring to a mixing device to obtain a mixture; step 2) pre-oxidation: transferring the mixture to an oxidation furnace, introducing air, gradient heating, completing oxidation, and obtaining pre-oxidized material; and step 3) carbonization treatment: transferring the pre-oxidized material to a carbonization furnace, and performing carbonization treatment to obtain a hard carbon negative material. The application has a large specific surface area and is rich in medium and large pores, can realize high dispersion and isolation of pitch, improves the oxidation efficiency of pitch, and especially solves the softening and melting problem of pitch with a medium and low softening point, thereby paving the way for commercialization of the pitch-based hard carbon.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method for preparing a hard carbon anode material. Background Technology

[0002] Commercially available sodium-ion batteries typically use hard carbon as the anode material, and the mainstream hard carbon supplied in the market currently uses biomass as the carbon source. These carbon sources contain a large amount of ash, making it difficult to control product consistency. Controlling ash content during the production of hard carbon and porous carbon also increases costs. Asphalt has a low ash content and advantages such as wide availability and stable raw materials. However, the production of asphalt-based hard carbon has encountered bottlenecks, mainly in the pre-oxidation process. Insufficient asphalt pre-oxidation leads to softening and melting, causing rearrangement of the graphitized carbon layers in the hard carbon material structure, inducing the formation of soft carbon from the asphalt. This results in a lower specific capacity of the obtained hard carbon, and these phenomena are particularly pronounced for asphalt with a low softening point.

[0003] CN202610153553.3 describes the synthesis of modified asphalt using asphalt as a precursor material, with the addition of solvents, crosslinking agents, and catalysts. The modified asphalt is then carbonized to obtain a hard carbon material. The hard carbon material has a large interlayer spacing and high disorder, and is accompanied by defects and closed pores, which is beneficial for the reversible storage of sodium ions and improves the electrochemical performance of sodium-ion batteries. However, the proposed scheme is relatively complex and will result in higher costs.

[0004] CN202511797250.7 describes the synthesis of hard carbon products using medium-temperature coal tar-based pitch. The process involves hydrogenation under high temperature and pressure, followed by the introduction of Lewis acid catalysts and modifiers, and two pre-oxidation processes. This makes the process complex and carries a high risk of inconsistent mass production.

[0005] CN202211548671.2 uses high-pressure air instead of water and solvents, and the asphalt is oxidized under supercritical conditions, which is superior to conventional air oxidation and oxidant processes. However, this process is suitable for natural asphalt, petroleum asphalt, shale asphalt or coal tar pitch with a softening point ≥240℃.

[0006] In summary, the current industry practice of using ultra-high temperature asphalt as a precursor for hard carbon, or employing highly complex processes, prevents the large-scale production of asphalt-based hard carbon. Therefore, there is an urgent need to develop a hard carbon synthesis method that can cover a wider range of softening points, particularly suitable for inexpensive medium- and low-temperature asphalt. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing asphalt-based hard carbon anode materials. This method introduces carbon materials into asphalt, which possess a large specific surface area and abundant meso- and macroporous structures. This allows for high dispersion and isolation of the asphalt, improving the efficiency of asphalt oxidation. It also forms abundant oxygen functional groups within the asphalt structure, increasing interlayer spacing. Furthermore, during the later carbonization process, numerous channels are formed within the asphalt, enhancing sodium storage capacity. This method is widely applicable, simple to operate, and suitable for asphalt with different softening point ranges. In particular, it solves the softening and melting problem of asphalt with medium- and low-temperature softening points, paving the way for the commercialization of asphalt-based hard carbon.

[0008] The objective of this invention is achieved as follows:

[0009] A method for preparing an asphalt-based hard carbon anode material includes the following steps:

[0010] Step 1) Take asphalt and carbon materials, transfer them to a mixing device, and obtain a mixture.

[0011] Step 2) Pre-oxidation: Transfer the mixture to an oxidation furnace, introduce air, and gradually increase the temperature to complete the oxidation and obtain a pre-oxidized material;

[0012] Step 3) Carbonization treatment: Transfer the pre-oxidized material to a carbonization furnace for carbonization treatment to obtain hard carbon anode material.

[0013] Furthermore, the asphalt mentioned in step 1) is coal tar pitch or petroleum asphalt; the particle size D50 of the asphalt ranges from 1 to 100 μm.

[0014] Furthermore, the carbon material mentioned in step 1) is obtained from a carbon source through processing, the processing of which includes:

[0015] The pretreatment process optimizes the specific surface area and pore size of the carbon source by introducing pore-forming agents or acid-base etching strategies;

[0016] The activation process includes physical activation or chemical activation. Physical activation uses water vapor and carbon dioxide at high temperatures, while chemical activation uses potassium hydroxide, phosphoric acid, sodium bicarbonate, and potassium bicarbonate at medium to high temperatures.

[0017] The carbonization process involves heat-treating a carbon source at a certain temperature, causing some components in the carbon source to volatilize or decompose, thus transforming it into a carbon material with a certain specific surface area and pore size distribution.

[0018] Further, in step 1), the carbon material is selected from one of the following: resin-based, walnut shell-based, coconut shell-based, coal-based, pitch-based, apricot shell-based, lychee wood-based, bamboo-based, and starch-based; the particle size D50 of the carbon material ranges from 1 to 15 μm; and the specific surface area of ​​the carbon material ranges from 50 to 2500 μm.2 / g; the average pore size of the carbon material is 2-300nm.

[0019] Furthermore, in step 1), the mass ratio of asphalt to carbon materials in the mixture is 100:1 to 100:50; the mixing equipment in step 1) is at least one of ball mill, sand mill, mixing kettle, mixer, rotary kiln, and ribbon mill; the mixing equipment has a mixing function to achieve the purpose of powder mixing.

[0020] Furthermore, the oxidation furnace in step 2) is at least one of a tubular furnace, a box furnace, a stirred tank, and a fluidized bed; the oxidation furnace in step 2) is equipped with an air intake unit for introducing air, and the air intake unit is at least one of a ventilator, a blower, and an air compressor.

[0021] Furthermore, step 2) of the gradient heating includes at least two temperature control stages; the first temperature control stage has a temperature range of 150-280℃, which is determined according to the asphalt softening point and is not lower than the asphalt softening point; the second temperature control stage has a temperature range of 300-350℃; the heating rate of each temperature control stage in step 2) is 1-3℃ / min; the duration of each temperature control stage in step 2) is 1-20h.

[0022] Furthermore, the temperature range for the carbonization treatment in step 3) is 1200-1400℃; the heating rate for the carbonization treatment in step 3) is 1-5℃ / min; and the carbonization treatment time for step 3) is 1-10h.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. By utilizing carbon materials with high specific surface area and medium to large pores, a high degree of dispersion and isolation of asphalt can be achieved. Combined with the optimization of the oxidation process, the contact efficiency between oxygen molecules in the air and the asphalt surface can be effectively improved, promoting the deep oxidation of asphalt, forming abundant oxygen functional groups, increasing the interlayer spacing, and forming a large number of channels during the later carbonization process, thereby improving the sodium storage capacity.

[0025] 2. The source of carbon materials is not limited by the type of material and can be asphalt, coal, biomass, and resin, etc.

[0026] 3. This method is simple to operate, widely applicable, and suitable for asphalt with different softening point ranges. In particular, it solves the technical problem of synthesizing hard carbon from asphalt with a medium-low temperature softening point. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is a photograph of the pre-oxide material obtained in Example 1 of this invention.

[0029] Figure 2 This is a photograph of the pre-oxide material obtained in Comparative Example 1 of this invention.

[0030] Figure 3 This is a SEM image of the carbon material used in Example 1 of this invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1: This example provides a method for preparing coal tar pitch-based hard carbon material, including the following steps: (1) Mixing: Take 3000g of coal tar pitch (softening point 120℃, particle size D50=1μm) and 600g of carbon material (resin-based, spherical, particle size D50=5μm, specific surface area 300m2 / g, average pore size 300nm), transfer to a ball mill, and ball mill at 300rpm for 30min to obtain a mixture. (2) Pre-oxidation: Load part of the mixture into a semi-circular graphite boat, transfer to a tube furnace, introduce air through an air compressor, heat to 150℃ at 1℃ / min, hold at 15h, heat to 300℃ at 1℃ / min, oxidize for 15h to obtain a pre-oxidized material. (3) Carbonization treatment: Transfer the pre-oxidized material to a box furnace, heat to 1200℃ at 1℃ / min, hold for 2h, and then cool naturally to room temperature to obtain a hard carbon material, code HC-1.

[0033] Example 2: This example provides a method for preparing coal tar pitch-based hard carbon material, including the following steps: (1) Mixing: Take 3000g of coal tar pitch (softening point 145℃, particle size D50=5μm) and 525g of carbon material (walnut shell base, irregular shape, particle size D50=7.5μm, specific surface area 2200m2 / g, average pore size 3nm), transfer to a sand mill, grind at 300rpm for 30min to obtain a mixture. (2) Pre-oxidation: Load the mixture into a graphite sagger, transfer to a box furnace, introduce air through a blower, heat to 160℃ at 2℃ / min, hold at 10h, heat to 310℃ at 2℃ / min, oxidize for 5h to obtain a pre-oxidized material. (3) Carbonization treatment: Transfer the pre-oxidized material to a box furnace, heat to 1250℃ at 2℃ / min, hold for 3h, then cool naturally to room temperature to obtain a hard carbon material, code HC-2.

[0034] Example 3: This example provides a method for preparing coal tar pitch-based hard carbon material, including the following steps: (1) Mixing: Take 3000g of coal tar pitch (softening point 190℃, particle size D50=7.5μm) and 450g of carbon material (coconut shell base, irregular shape, particle size D50=10μm, specific surface area 1800m2 / g, average pore size 6nm), transfer to a sand mill, grind at 300rpm for 30min to obtain a mixture. (2) Pre-oxidation: Load the mixture into a graphite sagger, transfer to a box furnace, introduce air through a blower, heat to 220℃ at 3℃ / min, hold at 8h, heat to 320℃ at 3℃ / min, oxidize for 3h to obtain a pre-oxidized material. (3) Carbonization treatment: Transfer the pre-oxidized material to a box furnace, heat to 1300℃ at 3℃ / min, hold for 4h, then cool naturally to room temperature to obtain a hard carbon material, code HC-3.

[0035] Example 4: This example provides a method for preparing a petroleum asphalt-based hard carbon material, including the following steps: (1) Mixing: Take 3000g of petroleum asphalt (softening point 210℃, particle size D50=10μm) and 375g of carbon material (coal-based, irregular shape, particle size D50=12.5μm, specific surface area 1500m2 / g, average pore size 20nm), transfer to a stirring vessel, stir at 100rpm for 1h to obtain a mixture. (2) Pre-oxidation: Load the mixture into a rotary kiln, introduce air through a blower, heat to 240℃ at 3℃ / min, hold at 2h, heat to 330℃ at 1℃ / min, oxidize for 2h to obtain a pre-oxidized material. (3) Carbonization treatment: Transfer the pre-oxidized material to a box furnace, heat to 1350℃ at 4℃ / min, hold for 5h, and then cool naturally to room temperature to obtain a hard carbon material, code HC-4.

[0036] Example 5: This example provides a method for preparing a petroleum asphalt-based hard carbon material, including the following steps: (1) Mixing: Take 3000g of petroleum asphalt (softening point 230℃, particle size D50=50μm) and 300g of carbon material (asphalt-based, irregular shape, particle size D50=15μm, specific surface area 1000m2 / g, average pore size 50nm), transfer to a mixer, stir at 500rpm for 0.5h to obtain a mixture. (2) Pre-oxidation: Load the mixture into a fluidized bed, introduce air through a fan, heat to 260℃ at 1℃ / min, hold at 2h, heat to 340℃ at 2℃ / min, oxidize for 3h to obtain a pre-oxidized material. (3) Carbonization treatment: Transfer the pre-oxidized material to a box furnace, heat to 1400℃ at 5℃ / min, hold for 6h, and then cool naturally to room temperature to obtain a hard carbon material, code HC-5.

[0037] Example 6: This example provides a method for preparing a petroleum asphalt-based hard carbon material, including the following steps: (1) Mixing: Take 3000g of petroleum asphalt (softening point 260℃, particle size D50=100μm) and 600g of carbon material (apricot shell base, irregular shape, particle size D50=5μm, specific surface area 2500m2 / g, average pore size 2nm), transfer to a rotary kiln, stir at 50rpm for 1h to obtain a mixture. (2) Pre-oxidation: Introduce air through a ventilator, heat to 280℃ at 1℃ / min, hold at 2h, heat to 350℃ at 1℃ / min, oxidize for 3h to obtain a pre-oxidized material. (3) Carbonization treatment: Transfer the pre-oxidized material to a box furnace, heat to 1450℃ at 4℃ / min, hold for 4h, and then cool naturally to room temperature to obtain a hard carbon material, code HC-6.

[0038] Example 7: This example provides a method for preparing coal tar pitch-based hard carbon material, including the following steps: (1) Mixing: Take 3000g of coal tar pitch (softening point 225℃, particle size D50=10μm) and 300g of carbon material (lychee wood base, irregular shape, particle size D50=5μm, specific surface area 2200m2 / g, average pore size 4nm), transfer to a rotary kiln, stir at 50rpm for 2h to obtain a mixture. (2) Pre-oxidation: Introduce air through a fan, heat to 250℃ at 1℃ / min, hold at 3h, heat to 350℃ at 2℃ / min, oxidize for 2h to obtain a pre-oxidized material. (3) Carbonization treatment: Transfer the pre-oxidized material to a box furnace, heat to 1280℃ at 5℃ / min, hold for 7h, and then cool naturally to room temperature to obtain a hard carbon material, code HC-7.

[0039] Example 8: This example provides a method for preparing coal tar pitch-based hard carbon material, including the following steps: (1) Mixing: Take 3000g of coal tar pitch (softening point 190℃, particle size D50=5μm) and 600g of carbon material (bamboo-based, irregular shape, particle size D50=7.5μm, specific surface area 2500m2 / g, average pore size 2nm), transfer to a ribbon mill, stir at 100rpm for 1h to obtain a mixture. (2) Pre-oxidation: Introduce air through a blower, heat to 220℃ at 1℃ / min, hold at 3h, heat to 325℃ at 2℃ / min, oxidize for 2h to obtain a pre-oxidized material. (3) Carbonization treatment: Transfer the pre-oxidized material to a box furnace, heat to 1320℃ at 2℃ / min, hold for 2h, and then cool naturally to room temperature to obtain a hard carbon material, code HC-8.

[0040] Example 9: This example provides a method for preparing coal tar pitch-based hard carbon material, including the following steps: (1) Mixing: Take 3000g of coal tar pitch (softening point 140℃, particle size D50=5μm) and 600g of carbon material (starch-based, spherical, particle size D50=5μm, specific surface area 1500m2 / g, average pore size 5nm), transfer to a ribbon mill, stir at 100rpm for 1h to obtain a mixture. (2) Pre-oxidation: Introduce air through a blower, heat to 180℃ at 1℃ / min, hold at 5h, heat to 350℃ at 2℃ / min, oxidize for 2h to obtain a pre-oxidized material. (3) Carbonization treatment: Transfer the pre-oxidized material to a box furnace, heat to 1300℃ at 2℃ / min, hold for 2h, and then cool naturally to room temperature to obtain a hard carbon material, code HC-9.

[0041] Comparative Example 1: The difference from Example 1 is that the resin-based carbon material in step (1) is removed, while the rest of the preparation methods and parameters are the same as in Example 1, that is, the asphalt is directly pre-oxidized and carbonized to obtain hard carbon material, code HCC-1.

[0042] Comparative Example 2: The difference from Example 1 is that the type of carbon material in step (1) is changed, and carbon material (resin-based, spherical, particle size D50=500μm, specific surface area 2500m2 / g, average pore size 1nm) is used. The rest of the preparation method and parameters are the same as in Example 1, and hard carbon material with code HCC-2 is obtained.

[0043] Comparative Example 3: The difference from Example 1 is that the type of carbon material in step (1) is changed, and carbon material (resin-based, spherical, particle size D50=5μm, specific surface area 10m2 / g, average pore size 20nm) is used. The rest of the preparation method and parameters are the same as in Example 1, and hard carbon material with code HCC-3 is obtained.

[0044] Comparative Example 4: The difference from Example 1 is that the content of resin-based carbon material in step (1) is reduced to 30g, while the rest of the preparation methods and parameters are the same as in Example 1, resulting in hard carbon material with code HCC-4.

[0045] Comparative Example 5: The difference from Example 1 is that the two temperature control steps in step (1) are changed to one temperature control step. The temperature control step of "heating to 150°C at 1°C / min and holding at that temperature for 5 hours" is removed. The rest of the preparation method and parameters are the same as in Example 1, and hard carbon material with the code HCC-5 is obtained.

[0046] Interlayer spacing test:

[0047] The interlayer spacing of hard carbon in the examples and comparative examples was analyzed by TEM testing.

[0048] Battery assembly and testing:

[0049] The asphalt-based hard carbon material, conductive carbon black, and sodium carboxymethyl cellulose prepared in the examples and comparative examples were mixed in a mass ratio of 90:5:5. Styrene-butadiene rubber and deionized water were added to prepare a slurry, which was stirred for 5 hours and then coated onto copper foil. The slurry was dried in a vacuum drying oven at 80°C for 10 hours. The resulting electrode was used as the negative electrode, and a sodium metal sheet was used as the positive electrode. The electrolyte was 0.8M NaPF6 / DIGLYME (100 Vol%), and the separator was a glass fiber optic GF / D separator. The cells were assembled into CR2032 button cells in an argon-filled glove box. The cells were charged and discharged at 0.1C, with a voltage window range of 0.01V-3.0V. The specific capacity and first-efficiency test results of the hard carbon are shown in Table 1.

[0050] Table 1 shows the electrochemical performance test results of the hard carbon material prepared in this invention.

[0051]

[0052] Depend on Figure 1 and Figure 2 The comparison shows that adding resin-based carbon materials before pre-oxidation during the synthesis of hard carbon from low-softening-point asphalt effectively solidifies the asphalt. Without the addition of carbon materials, insufficient pre-oxidation of the asphalt leads to softening and melting.

[0053] Figure 3The image shows a SEM image of the resin-based carbon material used in Example 1. It can be seen that the resin-based carbon material has a spherical morphology, a surface rich in porous structures, and a relatively large pore size of approximately 300 nm. The addition of this resin-based carbon material with a high specific surface area and medium to large pores enables high dispersion and isolation of asphalt during the pre-oxidation process. This effectively enhances the ability of oxygen molecules in the air to diffuse into the asphalt surface, promoting deep oxidation of the asphalt, forming abundant oxygen functional groups, and facilitating asphalt cross-linking.

[0054] As shown in the test results of Examples 1 to 9 in Table 1, the asphalt-based hard carbon synthesized using the method of this patent achieves a specific capacity of 290-320 mAh / g and an initial efficiency of over 90%, which is comparable to the performance of currently commercially available mainstream hard carbon. Furthermore, this method is universally applicable, suitable for both coal tar pitch and petroleum asphalt, and effective for asphalts with different softening points. The source of the introduced carbon material is not limited by the type of material and can be asphalt, coal, biomass, or resin-based materials, etc.

[0055] A comparison of Example 1 and Comparative Example 1 shows that if the carbon material of this patent is removed, i.e., hard carbon is synthesized directly using low softening point asphalt, the asphalt pre-oxidation is insufficient, resulting in softening and melting. This leads to the rearrangement of the graphitized carbon layers in the hard carbon material structure, inducing the asphalt to form soft carbon. Consequently, the specific capacity and initial efficiency of the obtained hard carbon are both low. By introducing carbon material into the asphalt, the pre-oxidation process is facilitated, allowing a large number of oxygen atoms to enter the asphalt structure, achieving oxygen doping, increasing the interlayer spacing, and also facilitating the formation of more closed pores during carbonization, thereby improving the sodium storage capacity of the asphalt-based hard carbon.

[0056] As can be seen from the comparison between Example 1 and Comparative Example 2, if the particle size of the carbon material used is too large, even if the specific surface area of ​​the material is large, it cannot guarantee the uniform mixing of the asphalt and carbon materials, which will reduce the degree of contact between the two, resulting in poor pre-oxidation effect and thus affecting the performance of asphalt-based hard carbon.

[0057] As can be seen from the comparison between Example 1 and Comparative Example 3, if the specific surface area of ​​the carbon material used is too low, the effective contact area between the asphalt and the carbon material cannot be guaranteed, resulting in poor pre-oxidation effect and affecting the performance of asphalt-based hard carbon.

[0058] As can be seen from the comparison between Example 1 and Comparative Example 4, if the amount of carbon material added is too low, it cannot provide enough contact sites between the asphalt and the carbon material, resulting in poor pre-oxidation effect of the asphalt and affecting the performance of asphalt-based hard carbon.

[0059] As can be seen from the comparison between Example 1 and Comparative Example 5, removing the first stage of temperature control also affects the hard carbon performance. This is because the purpose of the first stage of temperature control is to allow the asphalt to be more evenly dispersed and isolated between the carbon material particles, thus ensuring that the asphalt is oxidized more effectively.

[0060] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing an asphalt-based hard carbon anode material, characterized in that, Includes the following steps: Step 1) Take asphalt and carbon materials, transfer them to a mixing device, and obtain a mixture. Step 2) Pre-oxidation: Transfer the mixture to an oxidation furnace, introduce air, and gradually increase the temperature to complete the oxidation and obtain a pre-oxidized material; Step 3) Carbonization treatment: Transfer the pre-oxidized material to a carbonization furnace for carbonization treatment to obtain hard carbon anode material.

2. The method for preparing an asphalt-based hard carbon anode material according to claim 1, characterized in that, The asphalt mentioned in step 1) is coal tar pitch or petroleum asphalt; the particle size D50 of the asphalt is in the range of 1-100μm.

3. The method for preparing an asphalt-based hard carbon anode material according to claim 1 or 2, characterized in that, The carbon material mentioned in step 1) is obtained from a carbon source through processing. The processing includes: The pretreatment process optimizes the specific surface area and pore size of the carbon source by introducing pore-forming agents or acid-base etching strategies; The activation process includes physical activation or chemical activation. Physical activation uses water vapor and carbon dioxide at high temperatures, while chemical activation uses potassium hydroxide, phosphoric acid, sodium bicarbonate, and potassium bicarbonate at medium to high temperatures. The carbonization process involves heat-treating a carbon source at a certain temperature, causing some components in the carbon source to volatilize or decompose, thus transforming it into a carbon material with a certain specific surface area and pore size distribution.

4. A method for preparing an asphalt-based hard carbon anode material according to claim 1 or 2, characterized in that, Step 1) The carbon material is selected from one of the following: resin-based, walnut shell-based, coconut shell-based, coal-based, pitch-based, apricot shell-based, lychee wood-based, bamboo-based, and starch-based; the particle size D50 of the carbon material ranges from 1 to 15 μm; and the specific surface area of ​​the carbon material ranges from 50 to 2500 μm. 2 / g; the average pore size of the carbon material is 2-300nm.

5. A method for preparing an asphalt-based hard carbon anode material according to claim 1 or 2, characterized in that, Step 1) The mass ratio of asphalt to carbon materials in the mixture is 100:1 to 100:50; Step 1) The mixing equipment is at least one of ball mill, sand mill, mixing kettle, mixer, rotary kiln, and ribbon mill; the mixing equipment has a mixing function to achieve the purpose of powder mixing.

6. A method for preparing an asphalt-based hard carbon anode material according to claim 1 or 2, characterized in that, Step 2) The oxidation furnace is at least one of the following: tube furnace, box furnace, stirred tank, fluidized bed; Step 2) The oxidation furnace is equipped with an air inlet unit for introducing air, and the air inlet unit is at least one of the following: fan, blower, air compressor.

7. A method for preparing an asphalt-based hard carbon anode material according to claim 1 or 2, characterized in that, Step 2) The gradient heating includes at least two temperature control stages; the first temperature control stage has a temperature range of 150-280℃, which is determined according to the asphalt softening point and is not lower than the asphalt softening point; the second temperature control stage has a temperature range of 300-350℃; the heating rate of each temperature control stage in Step 2) is 1-3℃ / min; the duration of each temperature control stage in Step 2) is 1-20h.

8. A method for preparing a pitch-based hard carbon anode material according to claim 1 or 2, characterized in that, The carbonization temperature range in step 3) is 1200-1400℃; the heating rate in step 3) is 1-5℃ / min; and the carbonization time in step 3) is 1-10h.

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