Asphalt-based hard carbon negative electrode material, preparation method and application thereof

Abstract

The application provides a pitch-based hard carbon negative electrode material and a preparation method and application thereof, relates to the technical field of sodium ion battery manufacturing, and the pitch-based hard carbon negative electrode material takes low-softening-point pitch as a hard carbon precursor, is acidified by phosphoric acid, is pre-oxidized, and is high-temperature carbonized to obtain a pitch-based hard carbon negative electrode material with high capacity; the preparation method is mature in preparation process and is suitable for industrial production; compared with a traditional process, the pitch no longer needs to have a high softening point.In addition, the low-softening-point pitch is acidified by phosphoric acid in the application; in addition to the improvement of the softening point, a high polymer with a P-O / C-P functional group is introduced into the pitch, heteroatom doping is realized, and the capacity of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery manufacturing technology, and in particular to an asphalt-based hard carbon anode material, its preparation method, and its application. Background Technology

[0002] With the widespread application of electric vehicles and smart electronic devices, the demand for lithium will increase significantly. However, due to limited and unevenly distributed resources, the price of lithium materials has risen, increasing battery costs. Therefore, developing high-performance and low-cost lithium-based electrochemical energy storage devices has become an urgent priority. In recent years, sodium-ion batteries have shown great potential in large-scale energy storage applications due to their superior low-temperature performance and advanced safety features. The abundant sodium reserves on Earth also give them a significant cost advantage. Currently, the main anode materials for sodium-ion batteries are carbon-based, titanium-based, organic, and alloy materials. However, non-carbon-based materials exhibit problems such as volume expansion, poor stability, and poor conductivity during cycling, limiting their practical application. Carbon-based anode materials for sodium-ion batteries differ significantly from those for lithium-ion batteries, primarily due to the larger ionic radius of sodium ions. Traditional graphite anode materials widely used in lithium-ion batteries suffer from difficulties in effectively storing sodium ions because their interlayer spacing is smaller than the diameter of sodium ions.

[0003] Hard carbon anode materials have attracted much attention due to their stable macromolecular structure under high-current charge-discharge conditions, and their excellent safety performance promises applications in the electric vehicle field. Therefore, developing hard carbon anode materials with higher sodium storage efficiency, lower cost, and better stability is crucial for the large-scale application of sodium-ion batteries.

[0004] Currently, the main method for preparing asphalt-based hard carbon is high-temperature pre-oxidation treatment. This method is limited to asphalt with a high softening point (>240℃). Asphalt with a low softening point will melt during the pre-oxidation process, making it impossible for oxygen-containing functional groups to be inserted.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One of the objectives of this invention is to provide a method for preparing pitch-based hard carbon anode materials, so as to at least solve one of the technical problems existing in the prior art.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] This invention provides a method for preparing pitch-based hard carbon anode material, comprising the following steps:

[0009] A. Using asphalt as a precursor, acidification with concentrated phosphoric acid yields acidified asphalt.

[0010] B. The acidified asphalt is heated in an aerobic atmosphere to undergo pre-oxidation, thereby obtaining a pre-oxidized material;

[0011] C. The pre-oxidized material is subjected to high-temperature carbonization treatment to obtain pitch-based hard carbon anode material;

[0012] The softening point of the asphalt is 50–200℃.

[0013] Furthermore, the asphalt is selected from one of natural asphalt, petroleum asphalt, shale asphalt, and coal tar pitch;

[0014] Preferably, the particle size of the asphalt is less than 100 μm.

[0015] Furthermore, the concentration of the concentrated phosphoric acid is 70–90 wt%.

[0016] Furthermore, the acidification temperature is 100–200°C, and the acidification time is 4–11 hours;

[0017] Preferably, the acidification heating rate is 0.5–5 °C / min;

[0018] Preferably, acidification is carried out under stirring.

[0019] Furthermore, the acidification process also includes: cooling to room temperature, removing excess phosphoric acid by filtration or centrifugation, and then drying the precipitate to obtain acidified asphalt;

[0020] Preferably, the drying temperature is 70–90°C, the drying time is 10–15 hours, and the drying environment is a vacuum or air.

[0021] Furthermore, the pre-oxidation temperature is 280–300°C, and the pre-oxidation time is 6–10 hours;

[0022] Preferably, the heating rate of the pre-oxidation is 0.5 to 5 °C / min.

[0023] Furthermore, the carbonization temperature is 1100–1600°C, and the carbonization time is 1.5–3 hours;

[0024] Preferably, the heating rate of the carbonization is 1–10 °C / min;

[0025] Preferably, the carbonization atmosphere is an inert atmosphere, preferably one or more of Ar, N2 and He.

[0026] The present invention also provides a pitch-based hard carbon anode material prepared by the above-described preparation method;

[0027] Preferably, the interlayer spacing of the asphalt-based hard carbon anode material is 0.37–0.4 nm.

[0028] The present invention also provides the application of the above-mentioned pitch-based hard carbon anode material in the preparation of sodium-ion batteries.

[0029] In addition, the present invention also provides a sodium-ion battery comprising the above-mentioned pitch-based hard carbon anode material.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The asphalt-based hard carbon anode material of the present invention uses low softening point asphalt as a hard carbon precursor, and obtains a high-capacity asphalt-based hard carbon anode material through phosphoric acid acidification, pre-oxidation and high-temperature carbonization; the preparation method is mature and suitable for industrial production. Compared with the traditional process, it no longer requires the asphalt to have a high softening point, breaking the limitation of asphalt type.

[0032] 2. The asphalt material used in this invention has a high degree of industrialization and is a byproduct of petroleum and coal, therefore its cost is relatively low;

[0033] 3. This invention uses phosphoric acid to acidify low softening point asphalt, which not only increases the softening point but also introduces PO / CP functional groups into the asphalt, achieving heteroatom doping and improving battery capacity. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1a This is a high-magnification scanning electron microscope image of the hard carbon material obtained in Example 7 of the present invention;

[0036] Figure 1b for Figure 1a The elemental surface distribution representation diagram of the corresponding region in the middle, from left to right, shows the three elements: C, O, and P.

[0037] Figure 2a The first three GCD (constant current charge-discharge) curves of the hard carbon negative electrode in sodium-ion battery application of Example 7 of the present invention;

[0038] Figure 2b The first three GCD (constant current charge-discharge) curves of the carbon negative electrode in sodium-ion battery application of Comparative Example 1 of this invention are shown.

[0039] Figure 3a The hard carbon materials used in Examples 1, 5, 6, and 7 of this invention are in the range of 400–4000 cm⁻¹. -1 Fourier transform infrared spectra within the range;

[0040] Figure 3b The hard carbon materials used in Examples 1, 5, 6, and 7 of this invention are in the range of 500–1100 cm⁻¹ -1 Fourier transform infrared spectrum within the range. Detailed Implementation

[0041] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0043] According to one aspect of the present invention, a method for preparing a pitch-based hard carbon anode material is provided, comprising the following steps:

[0044] A. Using asphalt as a precursor, acidification with concentrated phosphoric acid yields acidified asphalt.

[0045] B. The acidified asphalt is heated in an aerobic atmosphere to undergo pre-oxidation, thereby obtaining a pre-oxidized material;

[0046] C. The pre-oxidized material is subjected to high-temperature carbonization treatment to obtain pitch-based hard carbon anode material;

[0047] The softening point of the asphalt is 50-200℃, and it is solid at room temperature.

[0048] The pitch-based hard carbon anode material of this invention uses low-softening-point pitch as a hard carbon precursor. Through phosphoric acid acidification, pre-oxidation, and high-temperature carbonization, a high-capacity pitch-based hard carbon anode material is obtained. This preparation method is mature and suitable for industrial production. Compared with traditional processes, it no longer requires the pitch to have a high softening point. Specifically, by using phosphoric acid to acidify the low-softening-point pitch, in addition to increasing the softening point, it also introduces PO / CP functional groups into the pitch, achieving heteroatom doping and improving battery capacity.

[0049] In some preferred embodiments, the asphalt is selected from one of natural asphalt, petroleum asphalt, shale asphalt, and coal tar pitch. The asphalt material used in this embodiment is a by-product of petroleum and coal, and has a low cost.

[0050] Preferably, before acidification, the asphalt is crushed to a particle size of less than 100 μm to improve acidification efficiency.

[0051] In some preferred embodiments, the concentrated phosphoric acid concentration is 70–90 wt%, for example, but not limited to 70 wt%, 75 wt%, 80 wt%, 85 wt%, or 90 wt%. When the concentrated phosphoric acid used is within the above range, it has excellent dehydrating properties, which can help remove moisture from the pitch, improve the reaction process, and potentially increase the purity of the product. This is particularly important for the synthesis of hard carbon materials, as the presence of moisture can introduce undesirable porosity and defects in the subsequent high-temperature carbonization step.

[0052] In some preferred embodiments, the acidification temperature is 100–200°C, for example, but not limited to 100°C, 120°C, 150°C, 180°C, or 200°C; the acidification time is 4–11 hours, for example, but not limited to 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or 11 hours; the acidification heating rate is 0.5–5°C / min, for example, but not limited to 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, or 5°C / min. When acidification is performed under the above conditions, the organic molecules in the asphalt undergo a certain degree of cross-linking, which helps to form a more robust carbonaceous structure. In sodium-ion batteries, this structure is advantageous for maintaining good electrochemical stability and cycle performance.

[0053] Preferably, in order to further improve the acidification efficiency, the acidification reaction is carried out with stirring in an oil bath.

[0054] In some preferred embodiments, the acidification process further includes: cooling to room temperature, removing excess phosphoric acid by filtration or centrifugation, and then drying the precipitate to obtain acidified bitumen.

[0055] The drying temperature is 70–90°C, for example, but not limited to 70°C, 75°C, 80°C, 85°C, or 90°C; the drying time is 10–15 hours, for example, but not limited to 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, or 15 hours; the drying environment is a vacuum or air to avoid the influence of heteroatoms in the environment on the structure of the hard carbon material.

[0056] In some preferred embodiments, the pre-oxidation temperature is 280–300°C, for example, but not limited to 280°C, 285°C, 290°C, 295°C, or 300°C; the pre-oxidation time is 6–10 hours, for example, but not limited to 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours; the pre-oxidation heating rate is 0.5–5°C / min, for example, but not limited to 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, or 5°C / min. When the above conditions are selected for pre-oxidation, it helps to introduce a certain degree of oxides (such as carboxyl groups, hydroxyl groups, etc.), which helps to improve the reactivity of asphalt and promote subsequent carbonization reactions.

[0057] In some preferred embodiments, the carbonization temperature is 1100–1600°C, for example, but not limited to 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, or 1600°C; the carbonization time is 1.5–3 hours, for example, but not limited to 1.5 hours, 2 hours, 2.5 hours, or 3 hours, preferably 2 hours; the carbonization heating rate is 1–10°C / min, for example, but not limited to 1°C / min, 2°C / min, 5°C / min, 8°C / min, or 10°C / min. Selecting the above conditions for carbonization helps to obtain a uniform carbonization reaction and reduces structural inhomogeneity caused by excessively high local temperatures. It can promote the uniformity of the pore structure and the orderliness of the microstructure.

[0058] Preferably, the carbonization atmosphere is an inert atmosphere, preferably one or more of Ar, N2 and He.

[0059] According to a second aspect of the present invention, a pitch-based hard carbon anode material prepared by the above-described preparation method is also provided. This pitch-based hard carbon anode material, prepared by a specific preparation method of the present invention, has an interlayer spacing of 0.37–0.4 nm, effectively stores sodium ions, and exhibits high capacity.

[0060] In addition to the beneficial effects of the pitch-based hard carbon anode material provided by the present invention, a third aspect of the present invention also provides the application of the above-mentioned pitch-based hard carbon anode material in the preparation of sodium-ion batteries.

[0061] According to a fourth aspect of the present invention, a sodium-ion battery is also provided, comprising the above-described pitch-based hard carbon anode material.

[0062] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0063] Example 1

[0064] The reaction was carried out in an oil bath equipped with a magnetic stirrer and a temperature sensor. The heating medium selected for the oil bath was dimethyl silicone oil. 20g of petroleum asphalt particles with a softening point of 135℃ were used as raw material. 50mL of concentrated phosphoric acid (85wt%) was added, and the mixture was stirred evenly in a glass bottle. The mixture was then transferred to an oil bath and stirred with a magnetic stirrer at 150℃ and 800rpm for 6 hours. After the reaction was completed, the system was allowed to cool naturally to room temperature. Excess phosphoric acid was removed by filtration, and the mixture was washed with a large amount of water. The precipitate was then dried under vacuum at 80℃ for 12 hours to obtain acidified asphalt. The softening point of the acidified asphalt was measured to be 215℃.

[0065] The acidified asphalt is placed in a tube furnace with an air atmosphere, heated to 300°C at a rate of 5°C / min and held for 10 hours, and then cooled to room temperature to obtain pre-oxidized asphalt.

[0066] The pre-oxidized asphalt material is placed in a tube furnace under N2 atmosphere and heated to 1200℃ at a rate of 5℃ / min, then held at that temperature for 2 hours. After cooling to room temperature, the asphalt-based hard carbon anode material is obtained.

[0067] An anode material based on pitch-based hard carbon was used to fabricate the anode, sodium was used as the cathode, and the electrolyte was 1 mol NaClO4 dissolved in EC:DMC (1:1). A glass fiber (GF / A) membrane was used for electrochemical testing at 30 mA g. -1 The initial discharge specific capacity at the current density is 376.85 mAh g. -1 .

[0068] Example 2

[0069] The reaction was carried out in an oil bath equipped with a magnetic stirrer and a temperature sensor. The heating medium selected for the oil bath was dimethyl silicone oil. 20g of petroleum asphalt particles with a softening point of 135℃ were used as raw material. 50mL of concentrated phosphoric acid (85wt%) was added, and the mixture was stirred evenly in a glass bottle. The mixture was then transferred to an oil bath and stirred with a magnetic stirrer at 150℃ and 800rpm for 6 hours. After the reaction was completed, the system was allowed to cool naturally to room temperature. Excess phosphoric acid was removed by filtration, and the mixture was washed with a large amount of water. The precipitate was then dried under vacuum at 80℃ for 12 hours to obtain acidified asphalt. The softening point of the acidified asphalt was measured to be 215℃.

[0070] The acidified asphalt is placed in a tube furnace with an air atmosphere, heated to 300°C at a rate of 5°C / min and held for 2 hours, and then cooled to room temperature to obtain pre-oxidized asphalt.

[0071] The pre-oxidized asphalt material is placed in a tube furnace under N2 atmosphere and heated to 1200℃ at a rate of 5℃ / min, then held at that temperature for 2 hours. After cooling to room temperature, the asphalt-based hard carbon anode material is obtained.

[0072] An anode material based on pitch-based hard carbon was used to fabricate the anode, sodium was used as the cathode, and the electrolyte was 1 mol NaClO4 dissolved in EC:DMC (1:1). A glass fiber (GF / A) membrane was used for electrochemical testing at 30 mA g. -1 The initial discharge specific capacity at the current density is 241.81 mAh g. -1 .

[0073] Example 3

[0074] The reaction was carried out in an oil bath equipped with a magnetic stirrer and a temperature sensor. The heating medium selected for the oil bath was dimethyl silicone oil. 20g of petroleum asphalt particles with a softening point of 135℃ were used as raw material. 50mL of concentrated phosphoric acid (85wt%) was added, and the mixture was stirred evenly in a glass bottle. The mixture was then transferred to an oil bath and stirred with a magnetic stirrer at 150℃ and 800rpm for 6 hours. After the reaction was completed, the system was allowed to cool naturally to room temperature. Excess phosphoric acid was removed by filtration, and the mixture was washed with a large amount of water. The precipitate was then dried under vacuum at 80℃ for 12 hours to obtain acidified asphalt. The softening point of the acidified asphalt was measured to be 215℃.

[0075] The acidified asphalt is placed in a tube furnace with an air atmosphere, heated to 300°C at a rate of 5°C / min and held for 10 hours, and then cooled to room temperature to obtain pre-oxidized asphalt.

[0076] The pre-oxidized asphalt material is placed in a tube furnace under N2 atmosphere and heated to 1300℃ at a rate of 5℃ / min, then held at that temperature for 2 hours. After cooling to room temperature, the asphalt-based hard carbon anode material is obtained.

[0077] An anode material based on pitch-based hard carbon was used to fabricate the anode, sodium was used as the cathode, and the electrolyte was 1 mol NaClO4 dissolved in EC:DMC (1:1). A glass fiber (GF / A) membrane was used for electrochemical testing at 30 mA g. -1 The initial discharge specific capacity at current density is 329 mAh g. -1 .

[0078] Example 4

[0079] The reaction was carried out in an oil bath equipped with a magnetic stirrer and a temperature sensor. The heating medium selected for the oil bath was dimethyl silicone oil. 20g of petroleum asphalt particles with a softening point of 135℃ were used as raw material. 50mL of concentrated phosphoric acid (85wt%) was added, and the mixture was stirred evenly in a glass bottle. The mixture was then transferred to an oil bath and stirred with a magnetic stirrer at 150℃ and 800rpm for 6 hours. After the reaction was completed, the system was allowed to cool naturally to room temperature. Excess phosphoric acid was removed by filtration, and the mixture was washed with a large amount of water. The precipitate was then dried under vacuum at 80℃ for 12 hours to obtain acidified asphalt. The softening point of the acidified asphalt was measured to be 215℃.

[0080] The acidified asphalt is placed in a tube furnace with an air atmosphere, heated to 300°C at a rate of 5°C / min and held for 10 hours, and then cooled to room temperature to obtain pre-oxidized asphalt.

[0081] The pre-oxidized asphalt material is placed in a tube furnace under N2 atmosphere and heated to 1400℃ at a rate of 5℃ / min, then held at that temperature for 2 hours. After cooling to room temperature, the asphalt-based hard carbon anode material is obtained.

[0082] An anode material based on pitch-based hard carbon was used to fabricate the anode, sodium was used as the cathode, and the electrolyte was 1 mol NaClO4 dissolved in EC:DMC (1:1). A glass fiber (GF / A) membrane was used for electrochemical testing at 30 mA g. -1 The initial discharge specific capacity at the current density is 324.7 mAh g. -1 .

[0083] Example 5

[0084] The reaction was carried out in an oil bath equipped with a magnetic stirrer and a temperature sensor. The heating medium selected for the oil bath was dimethyl silicone oil. 5g of petroleum asphalt particles with a softening point of 135℃ were used as raw material. 10mL of concentrated phosphoric acid (85wt%) was added, and the mixture was stirred evenly in a glass bottle before being transferred to the oil bath. The mixture was stirred with a magnetic stirrer at 200℃ and 800rpm for 4 hours. After the reaction was completed, the system was allowed to cool naturally to room temperature. Excess phosphoric acid was removed by filtration, and the mixture was washed with a large amount of water. The precipitate was then dried under vacuum at 80℃ for 12 hours to obtain acidified asphalt. The softening point of the acidified asphalt was measured to be 281℃.

[0085] The acidified asphalt is placed in a tube furnace with an air atmosphere, heated to 300°C at a rate of 5°C / min and held for 10 hours, and then cooled to room temperature to obtain pre-oxidized asphalt.

[0086] The pre-oxidized asphalt material is placed in a tube furnace under N2 atmosphere and heated to 1200℃ at a rate of 5℃ / min, then held at that temperature for 2 hours. After cooling to room temperature, the asphalt-based hard carbon anode material is obtained.

[0087] An anode material based on pitch-based hard carbon was used to fabricate the anode, sodium was used as the cathode, and the electrolyte was 1 mol NaClO4 dissolved in EC:DMC (1:1). A glass fiber (GF / A) membrane was used for electrochemical testing at 30 mA g. -1 The initial discharge specific capacity at the current density is 376.07 mAh g. -1 .

[0088] Example 6

[0089] The reaction was carried out in an oil bath equipped with a magnetic stirrer and a temperature sensor. The heating medium selected for the oil bath was dimethyl silicone oil. 5g of petroleum asphalt particles with a softening point of 135℃ were used as raw material and pulverized to a particle size of less than 100μm. 10mL of concentrated phosphoric acid (85wt%) was added, and the mixture was stirred evenly in a glass bottle before being transferred to an oil bath. The mixture was stirred with a magnetic stirrer at 200℃ and 800rpm for 4 hours. After the reaction was completed, the system was allowed to cool naturally to room temperature. Excess phosphoric acid was removed by filtration, and the mixture was washed with a large amount of water. The precipitate was then dried under vacuum at 80℃ for 12 hours to obtain acidified asphalt. The softening point of the acidified asphalt was measured to be 346℃.

[0090] The acidified asphalt is placed in a tube furnace with an air atmosphere, heated to 300°C at a rate of 5°C / min and held for 10 hours, and then cooled to room temperature to obtain pre-oxidized asphalt.

[0091] The pre-oxidized asphalt material is placed in a tube furnace under N2 atmosphere and heated to 1200℃ at a rate of 5℃ / min, then held at that temperature for 2 hours. After cooling to room temperature, the asphalt-based hard carbon anode material is obtained.

[0092] An anode material based on pitch-based hard carbon was used to fabricate the anode, sodium was used as the cathode, and the electrolyte was 1 mol NaClO4 dissolved in EC:DMC (1:1). A glass fiber (GF / A) membrane was used for electrochemical testing at 30 mA g. -1 The initial discharge specific capacity at the current density is 407.34 mAh g. -1 .

[0093] Example 7

[0094] The reaction was carried out in an oil bath equipped with a magnetic stirrer and a temperature sensor. The heating medium selected for the oil bath was dimethyl silicone oil. 5g of petroleum asphalt particles with a softening point of 135℃ were used as raw material and pulverized to a particle size of less than 100μm. 10mL of concentrated phosphoric acid (85wt%) was added, and the mixture was stirred evenly in a glass bottle before being transferred to an oil bath. Stirring was continued for 11 hours at 200℃ and 800rpm using a magnetic stirrer. After the reaction was completed, the system was allowed to cool naturally to room temperature. Excess phosphoric acid was removed by filtration, and the mixture was washed with a large amount of water. The precipitate was then dried under vacuum at 80℃ for 12 hours to obtain acidified asphalt. The softening point of the acidified asphalt was measured to be 413℃.

[0095] The acidified asphalt is placed in a tube furnace with an air atmosphere, heated to 300°C at a rate of 5°C / min and held for 10 hours, and then cooled to room temperature to obtain pre-oxidized asphalt.

[0096] The pre-oxidized asphalt material is placed in a tube furnace under N2 atmosphere and heated to 1200℃ at a rate of 5℃ / min, then held at that temperature for 2 hours. After cooling to room temperature, the asphalt-based hard carbon anode material is obtained.

[0097] An anode material based on pitch-based hard carbon was used to fabricate the anode, sodium was used as the cathode, and the electrolyte was 1 mol NaClO4 dissolved in EC:DMC (1:1). A glass fiber (GF / A) membrane was used for electrochemical testing at 30 mA g. -1 The initial discharge specific capacity at the current density is 421.86 mAh g⁻¹.

[0098] Example 8

[0099] The difference between this embodiment and Embodiment 7 is that the softening point of the petroleum asphalt particles is 83°C.

[0100] Electrochemical tests were performed at 30 mAg. -1 The initial discharge specific capacity at the current density is 346.71 mAh g. -1 .

[0101] Example 9

[0102] The difference between this embodiment and Embodiment 7 is that the concentration of concentrated phosphoric acid is 90 wt%.

[0103] Electrochemical tests were performed at 30 mA g -1 The initial discharge specific capacity at the current density is 453.6 mAh g. -1 .

[0104] Example 10

[0105] The difference between this embodiment and Embodiment 7 is that the concentration of concentrated phosphoric acid is 65 wt%.

[0106] Electrochemical tests were performed at 30 mAg. -1 The initial discharge specific capacity at the current density is 324.57 mAh g. -1 .

[0107] Example 11

[0108] The difference between this embodiment and Embodiment 7 is that the mixture is stirred for 11 hours in an oil bath using a magnetic stirrer at 100°C and 800 rpm.

[0109] Electrochemical tests were performed at 30 mAg. -1 The initial discharge specific capacity at the current density is 387.64 mAh g. -1 .

[0110] Example 12

[0111] The difference between this embodiment and Embodiment 7 is that the acidified asphalt is placed in a tube furnace with an air atmosphere, heated to 280°C at a rate of 0.5°C / min and held for 6 hours, and then cooled to room temperature to obtain pre-oxidized asphalt.

[0112] Electrochemical tests were performed at 30 mAg. -1 The initial discharge specific capacity at the current density is 386.87 mAh g. -1 .

[0113] Comparative Example 1

[0114] 5g of petroleum asphalt with a softening point of 135℃ was placed in a tube furnace under an Ar atmosphere, and the temperature was increased to 1400℃ at a rate of 5℃ / min and held for 3 hours. After cooling to room temperature, the carbon anode material was obtained.

[0115] The carbon anode material obtained by this method exhibits performance at 30 mA g. -1 The initial discharge specific capacity at the current density is 247.82 mAh g. -1 In the GCD curve, the capacity is entirely provided by the slope region, with no plateau region.

[0116] Comparative Example 2

[0117] The difference between this comparative example and Example 7 is that the softening point of the petroleum asphalt particles is 260°C.

[0118] Electrochemical tests were performed at 30 mAg. -1 The initial discharge specific capacity at the current density is 305.87 mAh g. -1 .

[0119] Experimental Example 1

[0120] The electrochemical performance testing methods for sodium-ion batteries used in the above embodiments and comparative examples are as follows:

[0121] Electrode sheet preparation: The negative electrode active material, conductive agent Super P, and binder (aqueous or organic) are mixed in a ratio of 7:2:1 or 8:1:1. N-methylpyrrolidone or water is added to prepare a uniform slurry, which is then manually coated onto carbon-coated copper foil. After vacuum drying at 80℃ or 100℃ for 12 hours, the slurry is cut into circular electrode sheets with a diameter of 1.2cm for later use.

[0122] Battery testing: The half-cell was assembled using a CR2032 button cell casing. In a glove box filled with argon gas and containing water / oxygen content less than or equal to 0.01ppm, the positive electrode casing was removed first, the cut electrode sheet was placed in the center of the positive electrode casing, and then 100μL of electrolyte was added. After the glass fiber separator was placed in, another 100μL of electrolyte was added. Then, the sodium metal sheet, gasket, spring sheet, and negative electrode casing were placed in sequence. Finally, the assembled battery was sealed using a battery sealing machine and left to stand for 6 hours for later use.

[0123] Experimental Example 2

[0124] To save on experimental costs, this experimental example uses Example 7, which has better electrochemical performance test results, as an example for testing. Figure 1a The image shown is a high-magnification transmission electron micrograph of the hard carbon material in Example 7, demonstrating that the hard carbon material with abundant closed-pore structure was successfully synthesized by this method. Figure 1b for Figure 1a The elemental distribution map of the corresponding region shows C, O, and P elements in that order. The elemental distribution map shows that P is uniformly distributed in hard carbon, and its content is much lower than that of C and O elements, confirming that P has been successfully doped into hard carbon materials.

[0125] Experimental Example 3

[0126] To save on experimental costs, this experimental example uses Example 7, which has better electrochemical performance test results, as an example for testing. Figure 2a The first three constant current charge-discharge curves of the hard carbon anode in Example 7 for sodium-ion battery applications show that the hard carbon material can withstand 30 mAg. -1 The initial discharge specific capacity at the current density is 421.86 mAh g⁻¹, with an initial efficiency of 59.56%. Its plateau capacity (discharge voltage less than 0.1V) contribution rate is 43.29%, corresponding to the abundant porous structure in the hard carbon material. Figure 2b Comparative Example 1 shows the first three constant current charge-discharge curves of the negative electrode in sodium-ion battery applications. The carbon negative electrode material has an initial discharge specific capacity of 346.95 mAh g-1 at a current density of 30 mA g-1, with an initial efficiency of 65.32%. In the graph, the capacity is entirely provided by the ramp region, with no plateau region, indicating that the phosphoric acid acidification and pre-oxidation treatment successfully increased the interlayer density of the carbon material graphite, thereby improving the capacity of the negative electrode material.

[0127] Experiment Example 4

[0128] Figure 3a Examples 1, 5, 6, and 7 describe hard carbon materials used in applications with a thickness of 400–4000 cm⁻¹. -1 With 500~1100cm -1 Fourier transform infrared spectra within the range, the results show that the infrared measurements include 3038 cm⁻¹. -1 and 740-870cm -1 The aromatic CH stretching vibration peak at 1170 cm⁻¹ -1 The COC stretching vibration peak at 1700 cm⁻¹ and 1700 cm⁻¹ -1 The nearby C=O stretching vibration peak. Additionally, at 2930 cm⁻¹... -1 2850cm -1 and 1370cm -1 The peaks at 500 cm⁻¹ are associated with CH₂ stretching and bending vibrations (in-plane), respectively. Besides common carbon- and oxygen-containing functional groups, peaks at 500 cm⁻¹ also appear. -1Clear signals containing P functional groups were observed on both sides; Figure 3b When the range was magnified, a clear CP bond signal was observed, which gradually increased with the softening point, indicating that phosphoric acid acidification successfully introduced CP bonds into the hard carbon material. Meanwhile, the acidified pitch in Example 7 showed a strong PO bond signal.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an asphalt-based hard carbon anode material, characterized in that, Includes the following steps: A. Using asphalt as a precursor, acidification is carried out with concentrated phosphoric acid at a temperature of 100–200 °C to obtain acidified asphalt; the concentration of the concentrated phosphoric acid is 70–90 wt%, and the acidification time is 4–11 h. B. The acidified asphalt is heated in an aerobic atmosphere to undergo pre-oxidation, thereby obtaining a pre-oxidized material; C. The pre-oxidized material is subjected to high-temperature carbonization treatment to obtain pitch-based hard carbon anode material; The softening point of the asphalt is 50~200 ℃; During acidification, the organic molecules in asphalt undergo cross-linking to a certain extent.

2. The preparation method according to claim 1, characterized in that, The asphalt is selected from one of the following: natural asphalt, petroleum asphalt, shale asphalt, and coal tar pitch.

3. The preparation method according to claim 1, characterized in that, The particle size of the asphalt is less than 100 μm.

4. The preparation method according to claim 1, characterized in that, The acidification heating rate is 0.5–5 °C / min.

5. The preparation method according to claim 1, characterized in that, Acidification is carried out under stirring.

6. The preparation method according to claim 1, characterized in that, After acidification, the process also includes: cooling to room temperature, removing excess phosphoric acid by filtration or centrifugation, and then drying the precipitate to obtain acidified bitumen.

7. The preparation method according to claim 6, characterized in that, The drying temperature is 70~90℃, the drying time is 10~15 h, and the drying environment is a vacuum or air.

8. The preparation method according to claim 1, characterized in that, The pre-oxidation temperature is 280~300 ℃, and the pre-oxidation time is 6~10 h.

9. The preparation method according to claim 1, characterized in that, The heating rate for the pre-oxidation is 0.5–5 °C / min.

10. The preparation method according to claim 1, characterized in that, The carbonization temperature is 1100–1600℃, and the carbonization time is 1.5–3 h.

11. The preparation method according to claim 1, characterized in that, The carbonization heating rate is 1–10 °C / min.

12. The preparation method according to claim 1, characterized in that, The carbonization atmosphere is an inert atmosphere.

13. The preparation method according to claim 1, characterized in that, The carbonization atmosphere is one or more of Ar, N2, and He.

14. A pitch-based hard carbon anode material prepared by the preparation method according to any one of claims 1 to 13.

15. The pitch-based hard carbon anode material according to claim 14, characterized in that, The interlayer spacing of the asphalt-based hard carbon anode material is 0.37~0.4 nm.

16. The application of the pitch-based hard carbon anode material according to claim 14 or 15 in the preparation of sodium-ion batteries.

17. A sodium-ion battery, characterized in that, Includes the pitch-based hard carbon anode material as described in claim 14 or 15.

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