An aromatic ether compound oxidized modified pitch-based hard carbon and a preparation method and application thereof

Abstract

The application provides an aromatic ether compound oxidized modified asphalt-based hard carbon and a preparation method and application thereof, and belongs to the technical field of battery materials, and aims to solve the technical problems of difficult structure regulation of asphalt-based hard carbon and low initial coulomb efficiency.The preparation method of the asphalt-based hard carbon comprises the following steps: S1, uniformly mixing asphalt raw materials with aromatic ether compounds, and then performing cross-linking polymerization reaction in an oxidizing atmosphere to form high-softening-point modified asphalt; and S2, performing gradient pre-oxidation and carbonization treatment on the high-softening-point modified asphalt obtained in S1 to obtain an asphalt-based hard carbon negative electrode material.The stable carbon precursor skeleton is constructed from the molecular level through the cross-linking polymerization mediated by aromatic ether molecules, the carbon microstructure is precisely regulated by combining gradient pre-oxidation, the specific surface area of the material can be effectively reduced, the electrolyte side reaction can be reduced, the initial coulomb efficiency of the obtained hard carbon can reach more than 85%, the reversible capacity can reach more than 360 mAh / g, and the obtained hard carbon has excellent sodium storage capacity and initial coulomb efficiency.

Description

Technical Field

[0001] This invention belongs to the technical field of battery materials, and particularly relates to an asphalt-based hard carbon. Background Technology

[0002] With the development of new energy storage technologies, sodium-ion batteries are considered an important alternative to lithium-ion batteries due to their abundant raw material resources, low cost, and high safety. Among these, hard carbon, with its low sodium intercalation potential, high reversible capacity, and good cycle stability, has become a research hotspot for sodium-ion battery anode materials. Pitch-based hard carbon, with its high carbonization rate, mature carbonization process, and tunable structure, is widely regarded as a promising source of carbon anodes for industrialization.

[0003] The preparation of hard carbon materials using pitch as a precursor still faces key challenges, including insufficient structural control, strong dependence on process methods, and poor environmental adaptability. For example, patent CN106159198A uses modified pitch pyrolysis to prepare carbon materials, but lacks an effective framework control mechanism, resulting in disordered carbon layer stacking and poor structural uniformity. While CN115259135A improves the pore structure through an oxidation strategy, the resulting high specific surface area enhances electrolyte side reactions, reduces initial coulombic efficiency, and results in high irreversible capacity. CN117142457A employs a multi-stage pyrolysis strategy to construct the pore structure, which enhances sodium ion storage performance to some extent, but the process is complex, and the batch-to-batch stability of the product is poor, making it difficult to meet industrial requirements. Therefore, there is an urgent need to develop a novel structural regulation pathway based on molecular cross-linking reactions to achieve carbon layer structure regulation and thus improve electrochemical performance. Summary of the Invention

[0004] To address the technical problems of difficult structural control and low initial coulombic efficiency of asphalt-based hard carbon, this invention proposes an aromatic ether compound-modified asphalt-based hard carbon, its preparation method, and its application. A high thermal stability precursor is constructed by cross-linking and polymerization of aromatic ether molecules with asphalt. Combined with gradient pre-oxidation, the carbon microstructure is precisely controlled, achieving a balance between high initial coulombic efficiency and high reversible capacity.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A method for preparing oxidatively modified pitch-based hard carbon using aromatic ether compounds includes the following steps:

[0007] S1 crosslinking polymerization modification: The asphalt raw material and aromatic ether compounds are mixed evenly in proportion, placed in a reaction device, and crosslinking polymerization reaction is carried out under an oxidizing atmosphere. After the reaction is completed, the material is cooled and discharged to obtain high softening point modified asphalt.

[0008] S2 Gradient Pre-oxidation and Carbonization: The high softening point modified asphalt obtained in step S1 is subjected to gradient pre-oxidation treatment, followed by high-temperature carbonization treatment under an inert atmosphere, and then cooled to obtain asphalt-based hard carbon material.

[0009] Further, in step S1, the mass ratio of the asphalt raw material to the aromatic ether compound is 100:(1-20).

[0010] Further, the aromatic ether compound is an aromatic ether compound whose molecular structure contains at least one aromatic ring and at least one ether bond. Preferably, the aromatic ether compound is selected from at least one of phenyl ether, diphenyl ether, biphenyl ether, anisole, 1,2-dimethoxybenzene, p-phenylenediether, and trimethoxybenzene.

[0011] Furthermore, the asphalt raw material is selected from at least one of coal-based asphalt and petroleum-based asphalt. Preferably, the asphalt raw material is at least one of medium- and low-temperature coal tar pitch, high-temperature coal tar pitch, coal tar, petroleum asphalt, and mesophase asphalt.

[0012] Furthermore, in step S1, the temperature of the crosslinking polymerization reaction is 250-330℃, the reaction holding time is 2-10h, and the heating rate is 2-5℃ / min.

[0013] Further, in step S1, the oxidizing atmosphere is at least one of air, oxygen, oxygen-enriched air, and oxygen-containing inert gas mixture; preferably, it is an air atmosphere.

[0014] Furthermore, in step S2, the gradient pre-oxidation treatment is carried out in an oxidizing atmosphere, using a multi-stage gradient heating mode, and pre-oxidation is completed by segmented holding within a temperature range of 180-400℃, with a heating rate of 2-5℃ / min.

[0015] Preferably, the specific steps of the gradient pre-oxidation are as follows: heating to 180-220℃ at a heating rate of 2-5℃ / min and holding for 1-5 hours, then heating to 300-400℃ at the same rate and holding for 2-6 hours.

[0016] Furthermore, in step S2, the carbonization treatment temperature is 1100-1500℃, the holding time is 1-5h, and the heating rate is 2-5℃ / min.

[0017] Furthermore, the inert atmosphere is at least one of nitrogen, argon, and helium; preferably high-purity nitrogen or high-purity argon.

[0018] The present invention also provides oxidative modified bitumen with aromatic ether compounds prepared by step S1 above.

[0019] The present invention also provides an aromatic ether compound oxidative modified pitch-based hard carbon prepared by the above preparation method.

[0020] The present invention also provides the application of the above-mentioned aromatic ether compound oxidatively modified pitch-based hard carbon as a negative electrode material in sodium-ion batteries.

[0021] This invention further provides a sodium-ion battery, wherein the negative electrode active material is asphalt-based hard carbon modified by the above-mentioned aromatic ether compound oxidation. Preferably, the electrolyte of the sodium-ion battery is a system of sodium salt dissolved in a carbonate mixed solvent; more preferably, the electrolyte is 1 mol·L⁻¹. - 1 NaPF6 dissolved in a mixed solvent of EC and DEC in a volume ratio of 1:1, the operating voltage window of the battery is 0.01-2.5V.

[0022] The beneficial effects of this invention are:

[0023] (1) This invention introduces aromatic ether compounds to conduct molecular-level cross-linking polymerization reactions with the active components in asphalt under thermal oxidation conditions, thereby constructing a stable three-dimensional cross-linking network in the asphalt system, significantly improving the softening point and thermal stability of asphalt, effectively suppressing the melting flow and disordered pyrolysis of asphalt during carbonization, and realizing the precise design of carbon skeleton structure from the perspective of molecular precursors.

[0024] (2) This invention combines gradient pre-oxidation process, which further solidifies the cross-linked structure of the precursor by segmented heating oxidation, and directionally induces the orderly stacking and structural evolution of carbon layers during carbonization. While optimizing the sodium storage carbon structure, it avoids the problem of high specific surface area caused by excessive oxidation, effectively reduces the specific surface area of ​​the material, reduces the side reaction between the electrolyte and the carbon surface, and achieves the simultaneous improvement of high reversible sodium storage capacity and high first coulombic efficiency.

[0025] (3) The preparation process of this invention is simple and highly controllable, requiring no complex equipment or harsh reaction conditions. The heat treatment process is directly compatible with existing industrial production platforms for carbon materials, and the product has good batch stability, demonstrating significant potential for large-scale application and promotion. The resulting hard carbon material has an initial coulombic efficiency of over 85% and a reversible capacity of over 360 mAh / g, exhibiting excellent comprehensive electrochemical performance. Attached Figure Description

[0026] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a scanning electron microscope (SEM) image of the pitch-based hard carbon prepared in Example 1 of the present invention;

[0028] Figure 2 The X-ray diffraction (XRD) pattern of the pitch-based hard carbon prepared in Example 1 of this invention. Detailed Implementation

[0029] 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.

[0030] Assembly and electrochemical performance testing of the half-cell: Hard carbon, conductive carbon black, SBR binder, and CMC thickener were weighed at a mass ratio of 80:10:7.5:2.5 and thoroughly stirred with deionized water to prepare a uniform negative electrode slurry free of solid particles. The slurry was mixed using a planetary mixer at 360 r / min for 120 min. After coating the electrode sheets, it was dried in a vacuum environment at 80℃ for 8 h. Circular electrode sheets with a diameter of 12 mm were cut for battery assembly, and the electrode areal density was controlled at 5~6 mg·cm³. -2 Using a sodium metal sheet as the counter electrode and glass fiber GF / A as the diaphragm, 1 mol·L -1 NaPF6 diethylene glycol dimethyl ether pure solution (NP-005) was used as the electrolyte for coin cell assembly. After battery assembly, the cells were allowed to stand for 12 hours before electrochemical charge-discharge testing was conducted. The test regime was constant current charge-discharge mode with a current density of 30 mA·g. -1 (Approximately 0.1C), constant current discharge cutoff voltage 0.01V, constant current charging cutoff voltage 2.5V.

[0031] Example 1

[0032] An aromatic ether compound is used to oxidize and modify pitch-based hard carbon. The preparation steps are as follows:

[0033] S1 crosslinking polymerization modification: Coal tar pitch and phenyl ether are mixed evenly at a mass ratio of 10:1 and added to a sealed stainless steel reactor. Air is introduced and maintained in the air atmosphere. The temperature is raised to 300℃ at a heating rate of 2℃ / min and held for 6 hours to carry out the crosslinking polymerization reaction. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain high softening point modified asphalt.

[0034] S2 Gradient Pre-oxidation and Carbonization: The above-mentioned high softening point modified asphalt was placed in a tube furnace and heated to 280°C at a heating rate of 2°C / min in an air atmosphere, held for 3 hours, and then heated to 320°C and held for 3 hours to complete the gradient pre-oxidation treatment; then the atmosphere was switched to high-purity nitrogen and heated to 1300°C at a heating rate of 3°C / min, held for 2 hours for high-temperature carbonization, and after natural cooling to room temperature, asphalt-based hard carbon material was obtained.

[0035] Electrochemical performance testing showed that the initial coulombic efficiency of the hard carbon material obtained in this embodiment was 89.4%, and the reversible capacity was 382 mAh / g.

[0036] Example 2

[0037] An aromatic ether compound is used to oxidize and modify pitch-based hard carbon. The preparation steps are as follows:

[0038] S1 crosslinking polymerization modification: Coal tar pitch and diphenyl ether are mixed evenly at a mass ratio of 100:1 and added to a sealed stainless steel reactor. Air is introduced and maintained in the air atmosphere. The temperature is raised to 330°C at a heating rate of 4°C / min and held for 2 hours to carry out the crosslinking polymerization reaction. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain high softening point modified asphalt.

[0039] S2 Gradient Pre-oxidation and Carbonization: The above-mentioned high softening point modified asphalt was placed in a tube furnace and heated to 200°C at a heating rate of 2°C / min in an air atmosphere, held for 3 hours, and then heated to 350°C and held for 4 hours to complete the gradient pre-oxidation treatment; then the atmosphere was switched to high-purity nitrogen and heated to 1500°C at a heating rate of 3°C / min, held for 2 hours for high-temperature carbonization, and then naturally cooled to room temperature to obtain asphalt-based hard carbon material.

[0040] Electrochemical performance testing showed that the initial coulombic efficiency of the hard carbon material obtained in this embodiment was 87.4%, and the reversible capacity was 370 mAh / g.

[0041] Example 3

[0042] An aromatic ether compound is used to oxidize and modify pitch-based hard carbon. The preparation steps are as follows:

[0043] S1 crosslinking polymerization modification: Coal tar pitch and diphenyl ether are mixed evenly at a mass ratio of 10:1 and added to a sealed stainless steel reactor. Air is introduced and maintained in the atmosphere. The temperature is raised to 280°C at a heating rate of 5°C / min and held for 5 hours to carry out the crosslinking polymerization reaction. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain high softening point modified asphalt.

[0044] S2 Gradient Pre-oxidation and Carbonization: The above-mentioned high softening point modified asphalt was placed in a tube furnace and heated to 200°C at a heating rate of 2°C / min in an air atmosphere, held for 3 hours, and then heated to 350°C and held for 4 hours to complete the gradient pre-oxidation treatment; then the atmosphere was switched to high-purity nitrogen and heated to 1500°C at a heating rate of 3°C / min, held for 2 hours for high-temperature carbonization, and then naturally cooled to room temperature to obtain asphalt-based hard carbon material.

[0045] Electrochemical performance testing showed that the reversible capacity of the hard carbon material obtained in this embodiment was 375 mAh / g.

[0046] Example 4

[0047] An aromatic ether compound is used to oxidize and modify pitch-based hard carbon. The preparation steps are as follows:

[0048] S1 crosslinking polymerization modification: Coal tar pitch and anisole are mixed evenly at a mass ratio of 5:1, added to a sealed stainless steel reactor, air is introduced and maintained in an air atmosphere, the temperature is raised to 300℃ at a heating rate of 5℃ / min, and held at the temperature for 2 hours to carry out the crosslinking polymerization reaction. After the reaction is completed, it is naturally cooled to room temperature to obtain high softening point modified asphalt.

[0049] S2 Gradient Pre-oxidation and Carbonization: The above-mentioned high softening point modified asphalt was placed in a tube furnace and heated to 260°C at a heating rate of 5°C / min in an air atmosphere, held for 3 hours, and then heated to 330°C and held for 4 hours to complete the gradient pre-oxidation treatment; then the atmosphere was switched to high-purity argon and heated to 1400°C at a heating rate of 3°C / min, held for 2 hours for high-temperature carbonization, and then naturally cooled to room temperature to obtain asphalt-based hard carbon material.

[0050] Electrochemical performance testing showed that the initial coulombic efficiency of the hard carbon material obtained in this embodiment was 88.2%, and the reversible capacity was 387 mAh / g.

[0051] Example 5

[0052] An aromatic ether compound is used to oxidize and modify pitch-based hard carbon. The preparation steps are as follows:

[0053] S1 crosslinking polymerization modification: Coal tar pitch and p-phenylenediether are mixed evenly at a mass ratio of 100:1 and added to a sealed stainless steel reactor. Air is introduced and maintained in an air atmosphere. The temperature is increased to 300℃ at a heating rate of 2℃ / min and held at the temperature for 2 hours to carry out the crosslinking polymerization reaction. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain high softening point modified asphalt.

[0054] S2 Gradient Pre-oxidation and Carbonization: The above-mentioned high softening point modified asphalt was placed in a tube furnace and heated to 280°C at a heating rate of 4°C / min in an air atmosphere, held for 2 hours, and then heated to 310°C and held for 8 hours to complete the gradient pre-oxidation treatment; then the atmosphere was switched to high-purity argon and heated to 1300°C at a heating rate of 4°C / min, held for 4 hours for high-temperature carbonization, and then naturally cooled to room temperature to obtain asphalt-based hard carbon material.

[0055] Electrochemical performance testing showed that the initial coulombic efficiency of the hard carbon material obtained in this embodiment was 87.1%, and the reversible capacity was 381 mAh / g.

[0056] Example 6

[0057] An aromatic ether compound is used to oxidize and modify pitch-based hard carbon. The preparation steps are as follows:

[0058] S1 crosslinking polymerization modification: Coal tar pitch, p-phenylenediol and 1,2-dimethoxybenzene are mixed evenly at a mass ratio of 100:1:9 and added to a sealed stainless steel reactor. Air is introduced and maintained in an air atmosphere. The temperature is increased to 310°C at a heating rate of 2°C / min and held at this temperature for 6 hours to carry out the crosslinking polymerization reaction. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain high softening point modified asphalt.

[0059] S2 Gradient Pre-oxidation and Carbonization: The high softening point modified asphalt was placed in a tube furnace and heated to 250°C at a rate of 3°C / min in air atmosphere, held for 2 hours, and then further heated to 310°C and held for 4 hours to complete the gradient pre-oxidation treatment. Subsequently, the temperature was switched to a high-purity nitrogen atmosphere and heated to 1300°C at a rate of 3°C / min, held for 4 hours for high-temperature carbonization. After natural cooling to room temperature, asphalt-based hard carbon material was obtained. The surface of the obtained hard carbon is as follows... Figure 1 SEM results showed that the pitch-based hard carbon consisted of irregularly broken, blocky particles with micron-sized particles, smooth cross-sections, and abundant intergranular spaces, providing space for electrolyte wetting and ion diffusion. The material surface lacked regular graphite flakes, initially exhibiting low graphitization characteristics. The microcrystalline structure of the obtained hard carbon is as follows: Figure 2 As shown, the XRD spectrum shows only two broad diffuse diffraction peaks at 23° and 43°, corresponding to the (002) and (100) crystal planes of the carbon material, respectively. There are no sharp crystalline phase peaks, which confirms that the pitch-based carbon material is mainly amorphous, with disordered carbon layer stacking and small crystallite size. The typical hard carbon microstructure can provide a large number of sodium storage active sites, making it suitable for sodium-ion battery anode applications.

[0060] Electrochemical performance testing showed that the initial coulombic efficiency of the hard carbon material obtained in this embodiment was 89.3%, and the reversible capacity was 392 mAh / g.

[0061] Comparative Example 1

[0062] An aromatic ether compound is used to oxidize and modify pitch-based hard carbon. The preparation steps are as follows:

[0063] S1 Pretreatment: Coal tar pitch is added to a sealed stainless steel reactor, air is introduced and maintained in the atmosphere, the temperature is increased to 300℃ at a rate of 2℃ / min, and the reaction is carried out for 6 hours. After the reaction is completed, it is naturally cooled to room temperature to obtain unmodified pitch.

[0064] S2 Gradient Pre-oxidation and Carbonization: The unmodified asphalt was placed in a tube furnace and heated to 280°C at a heating rate of 2°C / min in an air atmosphere, held for 3 hours, and then heated to 320°C and held for 3 hours to complete the gradient pre-oxidation treatment. Then, the temperature was switched to a high-purity nitrogen atmosphere and heated to 1300°C at a heating rate of 3°C / min, held for 2 hours for high-temperature carbonization. After naturally cooling to room temperature, asphalt-based hard carbon material was obtained.

[0065] Electrochemical performance testing showed that the initial coulombic efficiency of the hard carbon material obtained in this embodiment was 76.2%, and the reversible capacity was 210 mAh / g.

[0066] Table 1. Test results of the performance of pitch-based hard carbon sodium anode.

[0067]

[0068] As shown in Table 1, the aromatic ether compounds oxidatively modified pitch-based hard carbon prepared by the method of the present invention can achieve an initial coulombic efficiency of over 85% and a reversible capacity of over 360 mAh / g. It has both excellent sodium storage capacity and initial coulombic efficiency, and can be used as a high-performance anode material in sodium-ion batteries.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing pitch-based hard carbon modified by the oxidation of aromatic ether compounds, characterized in that, Includes the following steps: S1: After the asphalt raw material is mixed evenly with aromatic ether compounds, a cross-linking polymerization reaction is carried out in an oxidizing atmosphere to form a modified asphalt with a high softening point. S2: The high softening point modified asphalt obtained in S1 is subjected to gradient pre-oxidation and carbonization treatment to obtain asphalt-based hard carbon anode material.

2. The method for preparing aromatic ether compound oxidatively modified pitch-based hard carbon according to claim 1, characterized in that, The mass ratio of the asphalt raw material to the aromatic ether compound is 100:(1-20).

3. The method for preparing aromatic ether compound oxidatively modified pitch-based hard carbon according to claim 2, characterized in that, The aromatic ether compound is any one or a combination of phenyl ether, diphenyl ether, biphenyl ether, anisole, 1,2-dimethoxybenzene, p-phenylenediether, and trimethoxybenzene.

4. The method for preparing aromatic ether compound oxidatively modified pitch-based hard carbon according to claim 3, characterized in that, The asphalt is coal tar pitch or petroleum asphalt.

5. The method for preparing aromatic ether compound oxidatively modified pitch-based hard carbon according to any one of claims 1-4, characterized in that, The crosslinking polymerization reaction is carried out at a temperature of 250-330℃ for 2-10 hours.

6. The method for preparing aromatic ether compound oxidatively modified pitch-based hard carbon according to claim 5, characterized in that, The gradient pre-oxidation treatment is carried out in an oxidizing atmosphere and adopts a multi-stage gradient heating mode, with segmented heat preservation within a temperature range of 180-400℃ to complete the pre-oxidation.

7. The method for preparing aromatic ether compound oxidatively modified pitch-based hard carbon according to claim 6, characterized in that, The specific steps of the gradient pre-oxidation are as follows: heat to 180-220℃ at a heating rate of 2-5℃ / min and hold for 1-5 hours, then heat to 300-400℃ at the same rate and hold for 2-6 hours.

8. The method for preparing aromatic ether compound oxidatively modified pitch-based hard carbon according to claim 1, characterized in that, The carbonization process is carried out in an inert gas atmosphere at a temperature of 1100-1500℃, a reaction time of 1-5h, and a heating rate of 2-5℃ / min.

9. Aromatic ether compound oxidatively modified pitch-based hard carbon prepared by the method of any one of claims 1-8.

10. The application of the aromatic ether compound oxidatively modified pitch-based hard carbon sodium-ion battery anode material according to claim 9.

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