Asphalt-based hard carbon precursor, hard carbon material as well as preparation method and application of asphalt-based hard carbon precursor and hard carbon material

Abstract

The invention belongs to the technical field of battery materials, and particularly relates to an asphalt-based hard carbon precursor, a hard carbon material and a preparation method and application of the asphalt-based hard carbon precursor and the hard carbon material. According to the method, protonic acid or lewis acid of a specific type and dosage is used as a catalyst to be mixed with the asphalt powder, and the reaction is carried out in an oxygen-containing atmosphere at a proper temperature, so that the synergistic promotion of oxidation and cross-linking is realized, the cross-linking activation energy of oxygen-containing functional groups is remarkably reduced, oxygen-containing active sites generated by asphalt oxidation are quickly and fully utilized, and the service life of the asphalt is prolonged. Therefore, the precursor with high oxygen content, stable cross-linked structure and good thermal stability is obtained. After the precursor is carbonized, the pitch-based hard carbon material with excellent electrochemical performance can be prepared, and the pitch-based hard carbon material is suitable for being used as a battery negative electrode material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of battery materials, and more particularly relates to a pitch-based hard carbon precursor, a hard carbon material and a preparation method and application thereof. BACKGROUND

[0002] Hard carbon material is considered to be a potential negative electrode material for sodium-ion batteries due to its abundant defects, large interlayer spacing and good structural stability. Although traditional biomass-based hard carbon (such as coconut shell, walnut shell, etc.) has a wide range of raw material sources, the uncontrollability of its origin and composition leads to poor consistency of the final hard carbon product, which is difficult to meet the stringent requirements of large-scale battery production for material uniformity.

[0003] As a byproduct of petroleum or coal chemical industry, pitch has the advantages of high carbon content, stable source and low price, and is an ideal precursor of carbon materials. However, pitch is prone to graphitization to form soft carbon during direct high-temperature carbonization, which has small interlayer spacing and few defects, resulting in low sodium storage capacity and poor kinetic performance. Therefore, the pitch precursor usually needs to be pre-oxidized to increase its crosslinking degree and inhibit the ordered growth of graphitized microcrystals, so as to obtain a hard carbon structure with abundant closed pores and large interlayer spacing.

[0004] Traditional pitch pre-oxidation processes mainly fall into two categories: one is air oxidation method, which directly heats pitch to a certain temperature (200℃-400℃) in an air atmosphere for oxidation. This method is simple, but the oxidation efficiency is low, the reaction time is long, and the pitch is prone to foaming and swelling due to the volatilization of light components during oxidation, resulting in poor processability and low product yield. The other is chemical oxidation / acidification method, such as patent document CN119409161A, which uses a large amount of concentrated nitric acid or concentrated sulfuric acid to oxidize pitch at a low temperature (50℃-70℃) to obtain a strongly oxidizing acidified pitch. After acidification, the residual acid needs to be removed by washing and drying, which has the problems of complicated post-treatment process, high environmental pressure, etc. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to provide a pitch-based hard carbon precursor, a hard carbon material and a preparation method and application thereof, which aims to solve the problems of low oxidation efficiency, complicated process, high cost, poor processability, the need for washing and drying, etc. post-treatment of the existing pitch pre-oxidation process, and the low sodium storage capacity of the prepared hard carbon material.

[0006] To achieve the above-mentioned purpose, in a first aspect, the present application provides a preparation method of a pitch-based hard carbon precursor, comprising the following steps: mixing pitch powder and catalyst uniformly, and then performing oxidative crosslinking under an oxygen-containing atmosphere to obtain a pitch-based hard carbon precursor; The catalyst is a protonic acid or a Lewis acid, and the amount of the catalyst is 0.5% to 5% of the mass of the pitch powder; The temperature of the oxidative crosslinking is 250°C to 350°C, and the time of the oxidative crosslinking is 1h to 8h.

[0007] Preferably, the protonic acid is one or more of p-toluenesulfonic acid, sulfuric acid, nitric acid, and phosphoric acid.

[0008] Preferably, the Lewis acid is one or more of aluminum trichloride, ferric chloride, and zinc chloride.

[0009] Preferably, the pitch powder has a median particle size of 1μm to 20μm and a maximum particle size of no more than 50μm.

[0010] Preferably, the pitch has a softening point of no less than 150°C.

[0011] In a second aspect, the present application provides a pitch-based hard carbon precursor prepared by the above method.

[0012] Preferably, the pitch-based hard carbon precursor has an oxygen content of 20wt% to 35wt%.

[0013] In a third aspect, the present application provides a pitch-based hard carbon material prepared by carbonization of the pitch-based hard carbon precursor.

[0014] Preferably, the carbonization is performed in a vacuum environment or a protective atmosphere, wherein the protective atmosphere comprises at least one of nitrogen, argon, neon, helium, xenon, and krypton.

[0015] Preferably, the carbonization is performed at a temperature of 1100°C to 1400°C for a time of 1h to 8h.

[0016] In a fourth aspect, the present application provides a battery anode material comprising the pitch-based hard carbon material.

[0017] Overall, the above technical solutions conceived by the present application have the following technical advantages compared with the prior art: (1) The preparation method of the asphalt-based hard carbon precursor provided by the application adopts one-step catalytic oxidation crosslinking process, mixes a specific type and amount of protonic acid or Lewis acid as a catalyst with asphalt powder, and then performs oxidation crosslinking under an oxygen-containing atmosphere and a suitable temperature window. This method realizes the synergistic promotion of asphalt oxidation and crosslinking reaction, significantly reduces the activation energy of the crosslinking reaction between oxygen-containing functional groups, enables the active sites generated by asphalt oxidation to be quickly and fully utilized, thereby obtaining an asphalt-based hard carbon precursor with high oxygen content and stable crosslinking structure. After the reaction is completed, no post-treatment steps such as washing and drying are required. Compared with traditional multi-step oxidation or strong acid oxidation processes, this method greatly shortens the process flow, reduces energy consumption and raw material cost, and fundamentally avoids the generation of acid-containing wastewater, thereby significantly reducing environmental pressure and post-treatment cost while exhibiting outstanding economic and environmental benefits, and is suitable for large-scale production.

[0018] (2) By adjusting the type, amount and oxidation crosslinking temperature of the catalyst, the oxygen content and oxidation crosslinking degree of the asphalt-based hard carbon precursor can be controlled, and the pore structure and electrochemical performance of the final asphalt-based hard carbon material can be optimized. This process has good repeatability and is suitable for the stable preparation of high-performance asphalt-based hard carbon materials with good consistency, meeting the stringent requirements of the battery industry for the uniformity of negative electrode materials.

[0019] (3) The high-content and crosslinking structure asphalt-based hard carbon precursor prepared by the method has excellent thermal stability and good processability. During the carbonization process, oxygen atoms gradually and gradually escape in the form of gas, forming abundant closed pore structures in the carbon layer. This closed pore structure provides sufficient sodium storage active sites, so that the prepared asphalt-based hard carbon material has high reversible capacity and good initial efficiency, and the overall electrochemical performance is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the charge-discharge curve of the button cell assembled by Example 1, Example 4 and Comparative Example 1 of the application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the application more clear and explicit, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0022] In the description of the application, it should be understood that the term "and / or" is a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. The symbol " / " in this paper represents the relationship of or in the associated objects, for example, A / B represents A or B.

[0023] In the description of the embodiments of the present application, the word "exemplary" or "for example" is used to mean serving as an example, instance, or illustration. Any embodiment or design described as "exemplary" or "for example" should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the embodied examples are presented as illustrative of the present application. The word "exemplary" or "for example" is used in the description of the embodiments of the present application to mean serving as an example, instance, or illustration. Any embodiment or design described as "exemplary" or "for example" should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the embodied examples are presented as illustrative of the present application.

[0024] In the description of the embodiments of the present application, "a plurality of" means two or more, unless otherwise specified.

[0025] The conventional asphalt pre-oxidation process is usually complicated, which requires acid washing treatment of asphalt first, then washing and drying to remove residual acid, and then oxidation. The oxidation efficiency of this process is very low, and the generated oxygen-containing polar functional groups are less, resulting in insufficient cross-linking degree. In the subsequent heating carbonization process, light components are easily volatilized to cause material foaming and expansion, resulting in poor processing performance and low yield. Therefore, the prior art has to use complex processes such as multiple gradient heating oxidation to ensure the oxidation degree, which is complicated and high in cost. In view of this problem, patent document CN119409161A proposes an improved scheme, which uses a large amount of strong oxidizing acid such as concentrated nitric acid and concentrated sulfuric acid to treat asphalt at a relatively large temperature of 50-70°C. The concentrated acid used is both a reaction medium and a strong oxidizing agent, which can perform strong oxidation while acidifying, thereby eliminating the separate acidification and oxidation steps in the traditional process. However, this method is essentially a low-temperature acidification / oxidation process that relies on high concentration and high dosage of strong acid. Since a large amount of strong acid is used, it inevitably introduces serious post-treatment problems: a large amount of water needs to be consumed for washing to remove residual acid, thereby generating a large amount of acid-containing wastewater, increasing environmental pressure and production cost. Therefore, it is of great significance to develop a process with less acid dosage, no need for post-treatment, and high efficiency of asphalt oxidation and cross-linking, for simplifying the production process, reducing cost and environmental load, and improving product performance consistency.

[0026] Based on this, the present application provides a preparation method of an asphalt-based hard carbon precursor, which comprises the following steps: Mixing the asphalt powder with the catalyst uniformly, and then performing oxidation and cross-linking under an oxygen-containing atmosphere to obtain an asphalt-based hard carbon precursor; The catalyst is a protonic acid or a Lewis acid, and the dosage of the catalyst is 0.5%-5% of the mass of the asphalt powder. The temperature of the oxidation and cross-linking is 250-350°C, and the time of the oxidation and cross-linking is 1-8h.

[0027] In some embodiments, the protonic acid is one or more of p-toluenesulfonic acid, sulfuric acid, nitric acid, and phosphoric acid.

[0028] In some embodiments, the Lewis acid is one or more of aluminum trichloride, ferric chloride, and zinc chloride.

[0029] The inventors have found through experiments that by using a specific kind of protonic acid or Lewis acid as a catalyst, and performing oxidative crosslinking of pitch powder in an oxygen-containing atmosphere and a suitable temperature window, the activation energy of crosslinking reactions between oxygen-containing functional groups can be significantly reduced, thereby greatly improving the utilization efficiency of oxygen and the crosslinking rate and degree of functional groups. This allows the oxygen-containing polar groups formed in the initial stage of oxidation (about 50°C to 200°C) of pitch molecules to be fully retained and effectively crosslinked, thereby improving the thermal stability of the pitch, inhibiting the escape of light components, and improving the processability. The obtained precursor has a high oxygen content, and these oxygen atoms gradually escape in the form of gas during the subsequent high-temperature carbonization process, forming abundant closed pore structures between carbon layers, thereby significantly improving the sodium storage capacity of the final hard carbon material.

[0030] Compared with existing pitch pre-oxidation processes, the present application achieves synergistic enhancement of the oxidation and crosslinking processes through catalytic oxidative crosslinking, thereby simplifying the process, reducing costs, and effectively improving the processability of pitch-based hard carbon precursors and the electrochemical performance of the final hard carbon.

[0031] In some embodiments, the temperature of the oxidative crosslinking is 250°C to 350°C. Specifically, the temperature of the oxidative crosslinking can be 250°C, 280°C, 300°C, 320°C, 350°C, etc.

[0032] In some embodiments, the pitch powder has a median particle size of 1 μm to 20 μm and a maximum particle size of not more than 50 μm. For example, the pitch powder can have a median particle size of 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, etc. The pitch powder with such a particle size can be uniformly oxidized and crosslinked in an oxygen-containing atmosphere in the presence of the catalyst.

[0033] It can be understood that the type of pitch is not particularly limited in the present application and can be selected from, but is not limited to, coal tar pitch, petroleum pitch, ethylene tar pitch, and heavy aromatic hydrocarbon pitch, etc. In some embodiments, the pitch has a softening point of not less than 150°C, and preferably 150°C to 300°C. The pitch with such a softening point will not flow and foam during the oxidative crosslinking process, thereby sticking to the equipment and affecting the processability, etc.

[0034] In some embodiments, the oxygen-containing atmosphere includes, but is not limited to, oxygen, air, etc.

[0035] In another aspect, the present application also provides a pitch-based hard carbon precursor prepared by the above preparation method.

[0036] In some embodiments, the oxygen content of the asphalt-based hard carbon precursor is 20wt% to 35wt%. For example, the oxygen content can be 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, 32wt%, 35wt%, or the like.

[0037] The preparation method provided by the present application can produce an asphalt-based hard carbon precursor with a high oxygen content, which directly leads to the carbonized product of the precursor showing significant advantages in closed pore structure and electrochemical performance. Based on the above-mentioned precursor, the present application further provides an asphalt-based hard carbon material, which is prepared by carbonizing the above-mentioned asphalt-based hard carbon precursor.

[0038] In some embodiments, the carbonization is carried out in a vacuum environment or a protective atmosphere. The protective atmosphere includes at least one of nitrogen, argon, neon, helium, xenon, or krypton.

[0039] In some embodiments, the carbonization temperature is 1100°C to 1400°C, and the carbonization time is 1h to 8h.

[0040] The asphalt-based hard carbon material provided by the present application has high reversible capacity, excellent initial efficiency, and good electrochemical performance, and is suitable for use as a battery anode material. Based on the above-mentioned asphalt-based hard carbon material, the present application further provides a battery anode material, which comprises the above-mentioned asphalt-based hard carbon material.

[0041] In some embodiments, the battery anode material includes a lithium ion battery anode material, a sodium ion battery anode material.

[0042] In another aspect, the present application also provides a battery anode material, which comprises the above-mentioned battery anode material.

[0043] In some embodiments, the battery includes a lithium ion battery, a sodium ion battery.

[0044] It should be understood that materials similar to or the same as the types, models, qualities, properties, or functions of the reagents and instruments used in the following examples can be used to implement the present application. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, and the like used in the following examples can be obtained from commercial channels unless otherwise specified.

[0045] The following are examples and comparative examples: Example 1 The preparation method of the asphalt-based hard carbon material provided in this embodiment includes the following steps: Step one: crush and sieve the asphalt raw material with a softening point of 250°C to obtain an asphalt powder with a particle size D50 of 7μm.

[0046] Step two: mix the above asphalt powder with catalyst, wherein the catalyst is p-toluene sulfonic acid, and the amount of p-toluene sulfonic acid is 2% of the mass of the asphalt powder, then heat the mixture to 300℃ in air atmosphere and keep for 4h for oxidation crosslinking, to obtain an asphalt-based hard carbon precursor.

[0047] Step three: place the above asphalt-based hard carbon precursor in a tube furnace, heat to 1300℃ in nitrogen atmosphere and keep for 2h for carbonization treatment, to obtain an asphalt-based hard carbon material.

[0048] Example 2 The preparation method of the asphalt-based hard carbon material provided in this example is the same as that in Example 1, except that in step one, the amount of catalyst is 5% of the mass of the asphalt powder.

[0049] Example 3 The preparation method of the asphalt-based hard carbon material provided in this example is the same as that in Example 1, except that in step one, the amount of catalyst is 0.5% of the mass of the asphalt powder.

[0050] Example 4 The preparation method of the asphalt-based hard carbon material provided in this example is the same as that in Example 1, except that in step two, the oxidation crosslinking temperature is 350℃.

[0051] Example 5 The preparation method of the asphalt-based hard carbon material provided in this example is the same as that in Example 1, except that in step one, the amount of catalyst is 0.5% of the mass of the asphalt powder; and in step two, the oxidation crosslinking temperature is 350℃.

[0052] Example 6 The preparation method of the asphalt-based hard carbon material provided in this example is the same as that in Example 1, except that in step two, the oxidation crosslinking temperature is 350℃; and in step three, the carbonization temperature is 1100℃.

[0053] Example 7 The preparation method of the asphalt-based hard carbon material provided in this example is the same as that in Example 1, except that in step two, the catalyst is concentrated nitric acid with a mass fraction of 68% (the amount of catalyst is calculated according to the mass of HNO3).

[0054] Example 8 The preparation method of the asphalt-based hard carbon material provided in this example is the same as that in Example 1, except that in step two, the catalyst is AlCl3.

[0055] Example 9 The preparation method of the asphalt-based hard carbon material provided in this example is the same as that in Example 1, except that in step two, the oxidation crosslinking temperature is 250℃.

[0056] Comparative Example 1 The preparation method of the pitch-based hard carbon material provided in this comparative example is the same as that in Example 1, except that there is no catalyst in step two.

[0057] Comparative Example 2 The preparation method of the pitch-based hard carbon material provided in this comparative example is the same as that in Example 1, except that in step two, the catalyst is HCl.

[0058] Comparative Example 3 The preparation method of the pitch-based hard carbon material provided in this comparative example is the same as that in Example 1, except that in step two, the catalyst is CuCl2.

[0059] Comparative Example 4 The preparation method of the asphalt-based hard carbon material provided in this comparative example is the same as that in Example 1, except that in step two, the amount of catalyst used is 0.3% of the mass of the asphalt powder.

[0060] Comparative Example 5 The preparation method of the asphalt-based hard carbon material provided in this comparative example is the same as that in Example 1, except that in step two, the amount of catalyst used is 7% of the mass of the asphalt powder.

[0061] Comparative Example 6 The preparation method of the pitch-based hard carbon material provided in this comparative example is the same as that in Example 1, except that the temperature of oxidative crosslinking in step two is 100°C.

[0062] Performance testing: (1) The oxygen content of the asphalt-based hard carbon precursors prepared in each example and comparative example was determined by an elemental analyzer; the volatile content of the asphalt-based hard carbon precursors prepared in each example and comparative example was determined by referring to the standard method of GB / T 212-2008.

[0063] (2) Electrochemical performance of pitch-based hard carbon material: Pitch-based hard carbon material, binder polyvinylidene fluoride and conductive carbon black were mixed in a mass ratio of 92:4:4 to form a slurry, which was uniformly coated on aluminum foil and dried to form an electrode sheet. A sodium metal sheet was used as the counter electrode, a glass fiber film was used as the separator, and a mixed solution of 1 mol / L NaPF6 and ethylene carbonate (EC): dimethyl carbonate (DEC) = 1:1 vol.% was used as the electrolyte. The cells were assembled into coin cells in an argon glove box. The cells were discharged to 0V at 0.1C (nominal capacity 200mA / g) and then charged to 2.5V for the first charge-discharge test. The first discharge capacity and the first charge capacity (i.e., reversible capacity) were obtained. The first efficiency was calculated from the first discharge capacity and the first charge capacity. The median voltage was obtained from the voltage corresponding to half of the first discharge capacity.

[0064] The performance test results are shown in Table 1. Figure 1 As shown.

[0065] Table 1. Performance data of pitch-based hard carbon precursors and pitch-based hard carbon materials prepared in each embodiment and comparative example.

[0066] By comparing the data of the examples and comparative examples in Table 1, it can be seen that the pitch-based hard carbon precursor prepared by the method of this application has a high oxygen content (20wt%~35wt%) and suitable volatile matter (30wt%~45wt%). The reversible capacity of the final pitch-based hard carbon materials all reach more than 285mAh / g, and even exceeds 320mAh / g. Figure 1 Compared to existing bitumen oxidation processes, this application simplifies the process flow and reduces costs while significantly improving the processing performance of bitumen-based hard carbon precursors and the electrochemical performance of hard carbon products.

[0067] In contrast, Comparative Example 1, which did not use a catalyst, had an oxygen content of only 16.9% in its pitch-based hard carbon precursor, and the reversible capacity of the final pitch-based hard carbon material was only 279.9 mAh / g. Comparative Examples 2 and 3, which used hydrochloric acid and copper chloride as catalysts, only slightly increased the oxygen content of the pitch-based hard carbon precursor, still failing to achieve high-capacity hard carbon materials. The reason for this may be that when pitch is heated in an oxygen-containing atmosphere, oxygen-containing polar functional groups are generated on the pitch surface. Without a catalyst or with an unsuitable catalyst, the efficiency of further cross-linking reactions between these functional groups is low. A large number of active sites are not effectively utilized and escape with the light components, resulting in insufficient oxidative cross-linking and thus affecting the capacity of the hard carbon product.

[0068] Further analysis revealed that when the catalyst dosage was too low (0.3% of the mass of asphalt powder in Comparative Example 4), the bonding between oxygen-containing polar functional groups was insufficient, resulting in limited performance improvement. When the dosage was too low (7% of the mass of asphalt powder in Comparative Example 5), although the oxygen content of the asphalt-based hard carbon precursor increased significantly, excessive cross-linking may have damaged the stability of the carbon skeleton, leading to a decrease in both the capacity and initial efficiency of the asphalt-based hard carbon material.

[0069] The specific type of catalyst introduced in this application plays a key promoting role in oxidative crosslinking, significantly enhancing the bonding between oxygen-containing polar functional groups and enabling the formation of a stable three-dimensional crosslinked network within a suitable temperature range. This process not only effectively fixes more oxygen atoms into the pitch-based hard carbon precursor structure, increasing oxygen content, enhancing thermal stability, and improving processing performance, but also creates favorable conditions for subsequent carbonization. During the high-temperature carbonization stage, these oxygen atoms can be gradually removed, thereby forming abundant closed-pore structures in the carbon layer. These closed pores provide ample sodium storage active sites, resulting in the final hard carbon exhibiting excellent sodium storage capacity.

[0070] In summary, this application achieves efficient promotion and controllable conditions for the asphalt oxidation crosslinking process by introducing specific types and appropriate amounts of catalysts. It has the advantages of simple process, low cost and environmental friendliness, and provides a foundation for obtaining high-performance hard carbon materials.

[0071] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a pitch-based hard carbon precursor, characterized by, The method comprises the following steps: mixing the pitch powder with a catalyst, and then performing oxidative crosslinking under an oxygen-containing atmosphere to obtain a pitch-based hard carbon precursor; the catalyst is a protonic acid or a Lewis acid, and the amount of the catalyst is 0.5% to 5% of the mass of the pitch powder; the temperature of the oxidative crosslinking is 250°C to 350°C, and the time of the oxidative crosslinking is 1h to 8h.

2. The production method according to claim 1, characterized by, the protonic acid is one or more of p-toluenesulfonic acid, sulfuric acid, nitric acid, and phosphoric acid.

3. The production method according to claim 1, characterized by, the Lewis acid is one or more of aluminum trichloride, ferric chloride, and zinc chloride.

4. The method of claim 1, wherein, the pitch powder has a median particle size of 1μm to 20μm and a maximum particle size of not more than 50μm; and / or the pitch has a softening point of not less than 150°C.

5. An asphalt-based hard carbon precursor, characterized by, The pitch-based hard carbon material is prepared by the method of any one of claims 1 to 4.

6. The pitch-based hard carbon precursor according to claim 5, wherein the pitch-based hard carbon precursor has an oxygen content of 20wt% to 35wt%.

7. A pitch-based hard carbon material, characterized in that, The pitch-based hard carbon material is prepared by carbonization treatment of the pitch-based hard carbon precursor of claim 5 or 6.

8. The pitch-based hard carbon material according to claim 7, wherein The carbonization treatment is performed in a vacuum environment or a protective atmosphere, and the protective atmosphere comprises at least one of nitrogen, argon, neon, helium, xenon, and krypton.

9. The pitch-based hard carbon material of claim 7, wherein, The temperature of the carbonization is 1100°C to 1400°C, and the time of the carbonization is 1h to 8h.

10. A battery anode material, characterized by, The battery anode material comprises the pitch-based hard carbon material of any one of claims 7 to 9.

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