Catalytic graphitization method and application

Abstract

The invention belongs to the technical field of high value-added utilization of coal resources and artificial graphite, and particularly discloses a catalytic graphitization method and application, the method comprises the following steps: crushing an amorphous carbon material and a catalyst, uniformly mixing, and calcining to obtain a mixture; wherein the catalyst comprises limestone; and cooling the mixture, transferring the cooled mixture into a high-temperature graphitization furnace, and carrying out segmented graphitization calcination to obtain the artificial graphite negative electrode material. By adopting the Ca element (alkaline earth metal)-containing catalyst and the segmented graphitization calcination process, the graphitization time is remarkably shortened, the graphitization yield is improved, the technological process is stable and controllable, and the electrochemical performance of the product is improved. Meanwhile, toxic and harmful substances are not used in the whole process of the method, and the green production requirement is met.

Description

Technical Field

[0001] This invention relates to the fields of high-value utilization of coal resources and artificial graphite technology, and particularly to a method and application of catalytic graphitization. Background Technology

[0002] Graphite materials possess excellent electrical and thermal conductivity, as well as a high melting point and chemical stability, making them widely used in numerous fields such as chemical engineering, metallurgy, electronics, machinery, electrical engineering, and aerospace. Artificial graphite materials are generally obtained by heat-treating pyrolytic carbon at temperatures above 2400℃. Finding ways to obtain carbon materials with a high degree of graphitization at lower temperatures is of great significance for reducing production costs, improving production efficiency, and extending equipment lifespan.

[0003] Depending on their source, graphite can be divided into natural graphite and artificial graphite. Compared to natural graphite, artificial graphite has a wider range of sources and fewer impurities and defects, making it the main source for preparing lithium-ion anode materials. Artificial graphite is produced by graphitizing certain carbon materials under high-temperature conditions. It can be made from needle coke, pitch coke, mesophase carbon microspheres, pitch, etc. Currently, most artificial graphite is produced from needle coke. In recent years, the supply of needle coke has fallen short of demand, and its price has continued to rise, leading to an increase in the cost of lithium-ion batteries. Patent CN101880042A discloses artificial graphite microspheres for preparing lithium-ion battery anodes and its preparation method. The graphite microspheres are prepared using pitch and other raw materials, achieving a high degree of graphitization, but the process is cumbersome and complex. Patent CN108383116A discloses artificial graphite anode materials, their preparation methods, and lithium-ion anodes. It uses needle coke and other raw materials for granulation and carbonization to obtain artificial graphite with good rate performance, but its graphitization degree is low. Patent CN116514118B discloses a method for catalytic graphitization of petroleum calcined coke and its application. However, the catalyst used is one or more of the following: Fe, Co, Ni, Fe2O3, Al2O3, B2O3, B4C, SiC, and SiO2. Due to the significant problem of metal residue, it is difficult to completely remove these metals after graphitization. Residual impurities significantly reduce the electrochemical performance and stability of the graphite product. Furthermore, some catalysts are easily volatilized at high temperatures or react with carbon to form other compounds, resulting not only in catalyst loss but also the introduction of new impurities. Summary of the Invention

[0004] In view of the above-mentioned problems, this invention provides a method and application for catalytic graphitization. This invention employs a catalyst containing Ca (alkaline earth metal) and a segmented graphitization calcination process, significantly shortening the graphitization time, increasing the graphitization yield, ensuring a stable and controllable process, and improving the electrochemical performance of the product. Furthermore, the method does not use any toxic or harmful substances throughout the entire process, meeting the requirements of green production.

[0005] To address the above problems, the present invention provides a method for catalytic graphitization, comprising the following steps:

[0006] S1. Amorphous carbon material and catalyst are pulverized and mixed, and then calcined to obtain a mixture; wherein the catalyst includes limestone;

[0007] S2. After cooling the mixture, it is transferred to a high-temperature graphitization furnace and then subjected to segmented graphitization and calcination to obtain artificial graphite anode material.

[0008] It should be noted that the core of the catalytic effect of the Ca-containing catalyst in this invention lies in its ability to effectively reduce the key energy barrier in the graphitization process of amorphous carbon materials. It can significantly weaken the binding energy of C–H bonds, promote hydrogen removal, and thus expose more active carbon atoms available for reconstruction. Simultaneously, the presence of Ca lowers the migration energy barrier of carbon atoms in the nascent carbon network, enabling carbon atoms to migrate more quickly and in a more ordered manner to the graphite lattice growth front. The synergy of these two processes facilitates the continuous generation of new sp... 2 Hybridized carbon active sites and the construction of extended carbon six-membered ring networks provide kinetic advantages, thereby accelerating the lateral growth and vertically ordered stacking of graphene sheets.

[0009] Preferably, the catalyst further includes quicklime.

[0010] It should be noted that during the graphitization process, Ca promotes the migration and rearrangement of carbon atoms in amorphous carbon materials, accelerating the ordering of graphite sheet structure, which is the key to the product obtaining excellent electrochemical performance.

[0011] Preferably, the content of the catalyst is 0.5-3 wt% of the amorphous carbon material; the amorphous carbon material includes at least one of petroleum coke, pitch coke, and anthracite.

[0012] Preferably, in step S1, the particles with a particle size of -74μm obtained by crushing account for 90-100wt% of the total particles.

[0013] It should be noted that most of the particles obtained from the crushing process are below 200 mesh. The purpose of this particle size range is to ensure that the material has sufficient specific surface area and reactivity in subsequent processing, thereby ensuring that the reaction proceeds fully.

[0014] Preferably, in step S1, the calcination temperature is 600-800℃ and the time is 1 hour.

[0015] It should be noted that the calcination temperature should preferably be controlled between 600-800℃. This range is established for two purposes: (1) it needs to be higher than the boiling point of most organic impurities (usually below 600℃) to ensure that they are fully volatilized and removed; (2) it needs to be strictly lower than the thermal decomposition initiation temperature of calcium carbonate (usually above 800℃) so as to completely preserve the structure of the catalyst precursor and provide the necessary conditions for the subsequent catalytic graphitization process.

[0016] Preferably, in step S1, the calcination is carried out in an inert atmosphere, which is either argon or nitrogen.

[0017] Preferably, in step S2, the segmented graphitization calcination specifically involves: first holding at 2400-2500℃ for 1-3 hours, and then raising the temperature to 2600-2700℃ and holding for 0.5-2 hours.

[0018] It should be noted that during the first stage of segmented graphitization calcination, the Ca-containing catalyst plays a dual role as a catalyst: (1) by promoting the migration and rearrangement of carbon atoms in amorphous carbon materials, it significantly accelerates the ordering process of graphite sheet structure, which is the structural basis for the excellent electrochemical performance of the final product; (2) the catalytic activity of the Ca-containing catalyst effectively reduces the apparent temperature required for the graphitization reaction, thereby achieving energy saving. During the second stage of segmented graphitization calcination, the Ca element in the catalyst is fully removed through volatilization, thereby avoiding its adverse effects on the electrochemical performance and long-term stability of the product as an impurity residue.

[0019] Preferably, in step S2, the segmented graphitization calcination is carried out in an inert atmosphere, which is either argon or nitrogen.

[0020] Based on the same inventive concept, the present invention also provides an artificial graphite anode material, which is prepared by any of the preparation methods described above.

[0021] Based on the same inventive concept, the present invention also provides the application of the above-mentioned artificial graphite anode material in lithium-ion batteries.

[0022] The principle of this invention:

[0023] This invention uses a mixture of limestone and quicklime as a catalyst, playing multiple roles in the graphitization process: CaCO3 decomposes and releases CO2 at temperatures above 800℃, generating nano-CaO with high catalytic activity. The CO2 gas produced during this decomposition process can activate amorphous carbon materials in micro-regions, forming more active sites. Meanwhile, the pre-added CaO provides catalytic activity at even lower temperatures. The two work together to dynamically supplement and synergize active sites during the reaction. The newly generated CaO and the existing CaO act on the carbon structure, lowering the carbon atom migration barrier through chemical adsorption and other methods, promoting the nucleation and ordered stacking of six-membered carbon rings, and driving the growth of graphite crystallites. In the process design, the calcination treatment in step S1 (600-800℃) not only achieves uniform mixing of amorphous carbon materials and catalyst but also removes residual volatile impurities from the raw materials, providing a structurally clean precursor for subsequent graphitization. The segmented graphitization calcination process employs a segmented heating strategy: In the first stage, the Ca element in the catalyst promotes the directional growth and orderly stacking of graphite sheets, achieving efficient graphitization at a lower temperature; in the second stage, the temperature continues to rise so that the Ca component that has completed its catalytic function can be fully volatilized and removed, avoiding any impurities remaining in the final product.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) This invention introduces limestone and quicklime, causing limestone (CaCO3) to decompose at >800℃, generating nano-sized CaO and releasing CO2. This nano-CaO possesses high surface energy and high active site density, and can significantly weaken the bond energies of CH and CC bonds through surface adsorption and electron transfer, reducing the energy required for carbon atoms to escape the disordered structure; simultaneously, it provides a "low-barrier pathway" for carbon atom migration, promoting sp... 2 The formation and expansion of carbon networks;

[0026] (2) The introduction of the catalytic system of the present invention enables graphitization to be carried out efficiently at relatively low temperatures, significantly reducing energy consumption and production costs. The catalytic effect of the catalyst significantly reduces the apparent activation energy of carbon atom rearrangement. The graphitization process, which originally required >2800℃, can be completed efficiently in the range of 2400-2600℃. The reduction in reaction temperature directly reduces energy input and alleviates the thermal corrosion and thermal stress damage to the graphitization furnace lining and heating elements caused by high temperature, thus extending the service life of the equipment.

[0027] (3) The entire process of this invention does not require the use of toxic or harmful chemicals. The catalyst raw materials are natural limestone and quicklime. No harmful gases such as sulfur or nitrogen oxides are produced during the reaction. After the catalyst completes its catalytic function, it is effectively removed at high temperature in the second stage through sublimation or gas-phase reaction (such as generating Ca vapor), avoiding the residue of metal impurities. This process does not introduce other chemical reagents and achieves purification only through physical heating. No harmful residues are produced, which meets the requirements of clean production and sustainable development.

[0028] (4) The raw materials of the present invention are readily available, the process is stable and the conditions are controllable. By separating the two stages of “catalytic graphitization” and “catalyst removal”, it provides a flexible and stable operating window for temperature control, time setting and atmosphere management in industrial production. It is easy to implement in large-scale continuous graphitization furnaces and has good prospects for technology transfer and market competitiveness. Attached Figure Description

[0029] Figure 1 The images shown are HRTEM images of the graphite products obtained in Example 1 and Comparative Example 1 of the present invention; wherein, (a) is Example 1; and (b) is Comparative Example 1.

[0030] Figure 2 Here is a SEM image of the graphite product obtained in Example 1 of this invention;

[0031] Figure 3 This is a SEM image of the graphite product obtained in Comparative Example 2 of this invention;

[0032] Figure 4 The first charge-discharge curves of batteries were prepared for the graphite products obtained in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0033] To make the present invention easier to understand, specific embodiments are described below to further illustrate the invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved herein can be purchased commercially or obtained by known methods.

[0034] To address the technical problems mentioned in the background section, this invention provides a method and application for catalytic graphitization.

[0035] The following examples and comparative models further illustrate this point.

[0036] Example 1

[0037] A method for catalytic graphitization includes the following steps:

[0038] (1) Take 1 kg of petroleum coke produced by a domestic factory, and add a composite catalyst with a total mass of 0.8% of the petroleum coke mass to the petroleum coke. The composite catalyst is made of limestone and quicklime mixed at a mass ratio of 3:1. Crush the above raw materials until the proportion of particles with a particle size of less than 200 mesh reaches 90%. After mixing evenly, place them in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, with the target temperature set at 800℃ for 1 hour. After holding at the temperature, cool.

[0039] (2) The calcined material is mixed evenly again and transferred to a graphitization furnace for graphitization under a protective atmosphere (argon). The specific procedure is as follows: first, the temperature is raised to 2400℃ and held for 2 hours, then the temperature is raised to 2600℃ and held for 1 hour. After the holding is completed, the temperature is cooled to room temperature to obtain the final graphite product (coke-based graphite).

[0040] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.038.

[0041] Example 2

[0042] A method for catalytic graphitization includes the following steps:

[0043] (1) Take 1 kg of petroleum coke produced by a domestic factory, and add a composite catalyst with a total mass of 0.8% of the petroleum coke mass to the petroleum coke. The composite catalyst is made of limestone and quicklime mixed at a mass ratio of 2:1. Crush the above raw materials until the proportion of particles smaller than 200 mesh reaches 90%. After mixing evenly, place them in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, with the target temperature set at 800℃ for 1 hour. After holding at the temperature, cool.

[0044] (2) The calcined material is mixed evenly again and transferred to a graphitization furnace for graphitization under a protective atmosphere (argon). The specific procedure is as follows: first, the temperature is raised to 2400℃ and held for 2 hours, then the temperature is raised to 2600℃ and held for 1 hour. After the holding is completed, the temperature is cooled to room temperature to obtain the final graphite product (coke-based graphite).

[0045] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.047.

[0046] Example 3

[0047] A method for catalytic graphitization includes the following steps:

[0048] (1) Take 1 kg of petroleum coke, the same as in Example 1, add 1.0 wt% limestone to the petroleum coke, and crush the mixture until the proportion of particles smaller than 200 mesh reaches 90%, and place it in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, the target temperature is set at 800℃, 1 h, and after the heat preservation is completed, it is cooled;

[0049] (2) The cooled material is transferred to a graphitization furnace and graphitized under a protective atmosphere (argon). The specific procedure is as follows: first, the temperature is raised to 2400℃ and held for 2 hours, then the temperature is raised to 2600℃ and held for 1 hour. After the holding is completed, the material is cooled to room temperature to obtain the final graphite product (coke-based graphite).

[0050] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.049.

[0051] Comparative Example 1

[0052] A method for catalytic graphitization includes the following steps:

[0053] (1) Take 1 kg of the same petroleum coke as in Example 1, crush it until the proportion of particles smaller than 200 mesh reaches 90%, and place it in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, with the target temperature set at 800℃ for 1 hour, followed by cooling after the heat preservation is completed;

[0054] (2) The cooled material is transferred to a graphitization furnace and graphitized under a protective atmosphere (argon). The specific procedure is as follows: first, the temperature is raised to 2400℃ and held for 2 hours, then the temperature is raised to 2600℃ and held for 1 hour. After the holding is completed, the material is cooled to room temperature to obtain the final graphite product (coke-based graphite).

[0055] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.106.

[0056] Comparative Example 2

[0057] A method for catalytic graphitization includes the following steps:

[0058] (1) Take 1 kg of petroleum coke produced by a domestic factory, add quicklime with a total mass of 0.8% of the petroleum coke mass to the petroleum coke, crush the above raw materials until the proportion of particles with a particle size of less than 200 mesh reaches 90%, mix evenly, and place in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, the target temperature is set at 800℃, 1h, and after the heat preservation is completed, it is cooled;

[0059] (2) The calcined material is mixed evenly again and transferred to a graphitization furnace for graphitization under a protective atmosphere (argon). The specific procedure is as follows: first, the temperature is raised to 2400℃ and held for 2 hours, then the temperature is raised to 2600℃ and held for 1 hour. After the holding is completed, the temperature is cooled to room temperature to obtain the final graphite product (coke-based graphite).

[0060] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.045.

[0061] Comparative Example 3

[0062] A method for catalytic graphitization includes the following steps:

[0063] (1) Take 1 kg of the same petroleum coke as in Example 1, add 0.8 wt% calcium silicate to the petroleum coke, and crush the mixture until the proportion of particles smaller than 200 mesh reaches 90%, and place it in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, the target temperature is set at 1000℃, and the process lasts for 1 hour. After the heat preservation is completed, the mixture is cooled.

[0064] (2) The cooled material is transferred to a graphitization furnace and graphitized under a protective atmosphere. The specific procedure is as follows: first, the temperature is raised to 2400℃ and held for 2 hours, then the temperature is raised to 2600℃ and held for 1 hour. After the holding is completed, the material is cooled to room temperature to obtain the final graphite product (coke-based graphite).

[0065] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.084.

[0066] Comparative Example 4

[0067] A method for catalytic graphitization includes the following steps:

[0068] (1) Take 1 kg of petroleum coke produced by a domestic factory, and add a composite catalyst with a total mass of 1.0% of the petroleum coke mass to the petroleum coke. The composite catalyst is made of limestone and quicklime mixed in a mass ratio of 3:1. Crush the above raw materials until the proportion of particles with a particle size of less than 200 mesh reaches 90%. After mixing evenly, place them in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, with the target temperature set at 800℃ for 1 hour. After holding at the temperature, cool.

[0069] (2) The calcined material is mixed again and transferred to a graphitization furnace for graphitization under a protective atmosphere (argon). The specific procedure is as follows: heat up to 2400℃ and hold for 3 hours. After holding, cool to room temperature to obtain the final graphite product (coke-based graphite).

[0070] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.057.

[0071] Comparative Example 5

[0072] A method for catalytic graphitization includes the following steps:

[0073] (1) Take 1 kg of petroleum coke produced by a domestic factory, and add a composite catalyst with a total mass of 1.0% of the petroleum coke mass to the petroleum coke. The composite catalyst is made of limestone and quicklime mixed in a mass ratio of 3:1. Crush the above raw materials until the proportion of particles with a particle size of less than 200 mesh reaches 90%. After mixing evenly, place them in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, with the target temperature set at 800℃ for 1 hour. After holding at the temperature, cool.

[0074] (2) The calcined material is mixed again and transferred to a graphitization furnace for graphitization under a protective atmosphere (argon). The specific procedure is as follows: heat up to 2500℃ and hold for 3 hours. After holding, cool to room temperature to obtain the final graphite product (coke-based graphite).

[0075] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.043.

[0076] Comparative Example 6

[0077] A method for catalytic graphitization includes the following steps:

[0078] (1) Take 1 kg of petroleum coke produced by a domestic factory, and add a composite catalyst with a total mass of 1.0% of the petroleum coke mass to the petroleum coke. The composite catalyst is made of limestone and quicklime mixed in a mass ratio of 3:1. Crush the above raw materials until the proportion of particles with a particle size of less than 200 mesh reaches 90%. After mixing evenly, place them in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, with the target temperature set at 800℃ for 1 hour. After holding at the temperature, cool.

[0079] (2) The calcined material is mixed again and transferred to a graphitization furnace for graphitization under a protective atmosphere (argon). The specific procedure is as follows: heat up to 2600℃ and hold for 3 hours. After holding, cool to room temperature to obtain the final graphite product (coke-based graphite).

[0080] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.040.

[0081] Comparative Example 7

[0082] A method for catalytic graphitization includes the following steps:

[0083] (1) Take 1 kg of petroleum coke produced by a domestic factory, and add a composite catalyst with a total mass of 1.2% of the petroleum coke mass to the petroleum coke. The composite catalyst is made of limestone and quicklime mixed in a mass ratio of 3:1. Crush the above raw materials until the proportion of particles with a particle size of less than 200 mesh reaches 90%. After mixing evenly, place them in a tube furnace for calcination. The calcination process is carried out under an argon protective atmosphere, with the target temperature set at 800℃ for 1 hour. After holding at the temperature, cool.

[0084] (2) The calcined material is mixed again and transferred to a graphitization furnace for graphitization under a protective atmosphere (argon). The specific procedure is as follows: heat up to 2600℃ and hold for 3 hours. After holding, cool to room temperature to obtain the final graphite product (coke-based graphite).

[0085] The purity of the prepared coke-based graphite is greater than 99.99%. The prepared coke-based graphite was subjected to Raman testing, and the defect density ID / IG was calculated to be 0.045.

[0086] Performance testing and results analysis:

[0087] The graphite products prepared in Example 1 and Comparative Example 1 were analyzed by high-resolution transmission electron microscopy (HRTEM), and the results are as follows: Figure 1 As shown. By Figure 1As can be seen, the graphite product prepared in Example 1 exhibits clear, continuous, and long-range ordered graphite lattice fringes. The images show a crystal structure with highly consistent orientation, numerous stacked layers, and very few defects, indicating that the graphite product of Example 1 has an excellent degree of graphitization. In contrast, the graphite product prepared in Comparative Example 1 (without catalyst) shows short-range, disordered, and discontinuous lattice fringes, with obvious grain boundaries, dislocations, and amorphous regions. This further illustrates the feasibility of the present invention.

[0088] The graphite products prepared in Example 1 and Comparative Example 2 were analyzed by scanning electron microscopy (SEM), and the results are as follows: Figure 2-3 As shown. By Figure 2 As can be seen, the graphite product prepared in Example 1 exhibits a highly developed and uniform porous sheet network structure; the product consists of a large number of interconnected graphene microsheets with clear edges and uniform thickness, forming open, interconnected three-dimensional pores; this structure benefits from the in-situ activation and pore-expanding effect of CO2 gas generated by the decomposition of calcium carbonate, combined with the catalytic rearrangement effect of CaO, which jointly optimizes the microstructure of the carbon skeleton. Figure 3 It can be seen that the graphite product prepared in Comparative Example 2 (catalyst: quicklime) mainly consists of dense particles with uneven size and smooth surface, with indistinct lamellar structure and significantly lower porosity than that in Example 1. Figure 2 This indicates that, in the absence of in-situ activation by CO2, the catalytic function of CaO alone can promote the graphitization rearrangement of carbon atoms, but it is difficult to effectively reconstruct the precursor carbon skeleton, resulting in a low specific surface area and underdeveloped pore structure of the product. Figure 2 and Figure 3 The comparison reveals the synergistic advantages of the composite catalyst of this invention. This invention not only lowers the graphitization energy barrier through CaO, but also achieves in-situ activation and pore formation of the carbon skeleton through CO2 from limestone decomposition, thereby obtaining graphite products with superior microstructure (high specific surface area, abundant pores, and open lamellars). This lays the structural foundation for its excellent electrochemical performance (such as ion transport rate and electrolyte wettability).

[0089] The graphite products prepared in Examples 1-3 and Comparative Examples 1-7 were used as active materials to prepare electrode sheets according to a mass ratio of active material: polyvinylidene fluoride (PVDF): conductive carbon black = 7:2:1. Specifically, the above components were thoroughly ground and mixed, and N-methylpyrrolidone (NMP) was added to form a uniform slurry, which was then coated onto a copper foil current collector. The slurry was then vacuum dried at 353 K for 12 h and cut into circular electrode sheets with a diameter of 14 mm. Battery assembly was completed in an argon atmosphere glove box (water and oxygen content <0.01 ppm). A CR2025 coin cell battery case was used, with a lithium metal sheet as the counter electrode and a 1 M LiPF6 DMC / EC / EMC (volume ratio 1:1:1) mixed solution (containing 1% VC) as the electrolyte. Circular electrode sheets were placed in sequence, 70 μL of electrolyte was added, a separator was laid, and lithium sheets and nickel mesh were placed before sealing. After assembly, the cells were allowed to stand for 12 h before testing. The results are shown in Table 1 below (the first charge-discharge curves of the corresponding batteries of Example 1 and Comparative Example 1 are shown in Figure 4).

[0090] Table 1:

[0091]

[0092] As shown in Table 1, the initial coulombic efficiency of the batteries prepared from the graphite products obtained in Examples 1-2 and Comparative Examples 5-6 is superior to that of currently commercially available graphite materials (93%). This indicates that the composite catalyst (limestone + quicklime) and its combination with segmented graphitization and calcination of the present invention can effectively improve the reversible capacity and interfacial stability of the graphite anode material during the first charge-discharge process. Therefore, the present invention demonstrates significant market competitiveness and industrial application potential while improving the key electrochemical performance of the product. Comparative Examples 5-6 used a single temperature for graphitization (2500℃ and 2600℃, respectively). The results showed that at 2500℃, the petroleum coke was basically graphitized, but the Ca element was not effectively removed; however, when the temperature was increased to 2600℃, the Ca element was fully removed. This proves that the catalytic effect and subsequent removal of Ca need to be completed in different temperature ranges, thus verifying the scientific validity and necessity of the segmented heating process adopted in the present invention (such as completing catalytic graphitization at a lower temperature first, and then raising it to a higher temperature to remove Ca).

[0093] As can be seen from the comparison between Example 1 and Comparative Example 1 in Table 1, under catalyst-free conditions, significant graphitization of petroleum coke typically requires temperatures above 2800°C to obtain sufficient driving force for atomic migration. Although the highest temperature used in Comparative Example 1 (2600°C) is high, it is still below the intrinsic transformation temperature. Therefore, carbon atoms cannot obtain sufficient rearrangement energy, resulting in a slow and incomplete graphitization process. This indicates that under this heating procedure, without the participation of a catalyst, the temperature of the reaction system has not yet reached the temperature necessary for significant graphitization of petroleum coke. The catalyst can weaken the C-C bonds through surface adsorption and provide low-energy migration pathways for carbon atoms, thereby increasing the effective migration rate of carbon atoms by several orders of magnitude at the same temperature.

[0094] As can be seen from the comparison between Example 1 and Comparative Example 3 in Table 1, Comparative Example 3, which uses calcium silicate as a catalyst, exhibits poor graphitization effect, indicating that this component is detrimental to the graphitization process of petroleum coke. This is because calcium silicate has a stable structure and is not easily decomposed or releases highly catalytically active free calcium species (such as atomic Ca or CaO) within the graphitization temperature range, thus making it difficult to effectively reduce the activation energy of carbon atom rearrangement. Furthermore, some calcium silicate may react with carbon at high temperatures to generate inert impurities such as silicon carbide (SiC), or its solid particles may hinder the continuous growth of graphite crystallites, thereby introducing defects and disrupting the orderly stacking of graphite layers.

[0095] As can be seen from the comparison between Example 3 and Comparative Examples 2-3 in Table 1, quicklime as a catalyst (Comparative Example 2) has a better catalytic effect than calcium silicate (Comparative Example 3) but weaker than limestone (Example 3). This is because the crystal surface of CaO (especially specific crystal faces) can provide a local structural template effect for the planar arrangement of aromatic carbon rings, inducing the directional nucleation of six-membered carbon rings on its surface, catalyzing the dehydrogenation and aromatization reactions of aliphatic chains or cycloalkane structures in petroleum coke, and providing more sps for subsequent graphitization. 2 Carbon structural unit. In Example 3, limestone was used as a catalyst, and its mechanism of action is as follows: the main component of limestone, calcium carbonate, undergoes thermal decomposition above 800°C, generating highly dispersed nano-calcium oxide (CaO) and releasing carbon dioxide (CO2). The newly generated nano-CaO has high surface energy and abundant catalytic active sites, which can effectively adsorb carbon atoms, significantly reducing the activation energy of carbon atom migration and graphite lattice formation, thereby promoting the graphitization process. At the same time, the CO2 generated by decomposition can act as a weak oxidant at high temperatures, selectively reacting with some disordered carbon or impurities in petroleum coke, playing a role in in-situ purification and microporous expansion. This process not only improves the purity of the raw materials but also increases the effective specific surface area and reactive active sites of the carbon material, creating a more favorable physical structural basis for the subsequent ordered rearrangement of carbon atoms.

[0096] Furthermore, when CaO is added to limestone as a catalyst (Example 2), not only is the catalytic effect more significant, but the overall performance of the final graphite product is also improved simultaneously. The added CaO can act as a "seed" or "anchor," providing a substrate for the attachment and growth of nano-CaO generated by the decomposition of CaCO3, which helps maintain the dispersion and stability of the catalytic sites and prevents them from becoming deactivated due to high-temperature agglomeration.

[0097] Depend on Figure 4 As can be seen from the comparison of the first-cycle charge-discharge curves of the batteries prepared from the graphite products of Example 1 and Comparative Example 1, Example 1 of the present invention exhibits significantly higher specific capacity during both the first-cycle discharge and charging processes. More importantly, its voltage hysteresis between charge and discharge curves is smaller, indicating lower polarization; and the two curves overlap earlier, meaning a significant reduction in irreversible capacity loss and a substantial improvement in first-cycle coulombic efficiency. This directly demonstrates the key role of the catalyst and process described in this invention in improving the electrochemical reversibility of graphite anode materials and reducing first-cycle lithium loss, laying a performance foundation for its practical application.

[0098] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for catalytic graphitization, characterized in that, Includes the following steps: S1. Amorphous carbon material and catalyst are pulverized and mixed, and then calcined to obtain a mixture; wherein the catalyst includes limestone; S2. After cooling the mixture, it is transferred to a high-temperature graphitization furnace and then subjected to segmented graphitization and calcination to obtain artificial graphite anode material.

2. The method for catalytic graphitization according to claim 1, characterized in that, The catalyst also includes quicklime.

3. The method for catalytic graphitization according to claim 1 or 2, characterized in that, The catalyst content is 0.5-3 wt% of the amorphous carbon material; the amorphous carbon material includes at least one of petroleum coke, pitch coke, and anthracite.

4. The method for catalytic graphitization according to claim 1, characterized in that, In step S1, particles with a diameter of -74μm obtained from crushing account for 90-100wt% of the total particles.

5. The method for catalytic graphitization according to claim 1, characterized in that, In step S1, the calcination temperature is 600-800℃ and the time is 1 hour.

6. The method for catalytic graphitization according to claim 1, characterized in that, In step S1, the calcination is carried out in an inert atmosphere, which is either argon or nitrogen.

7. The method for catalytic graphitization according to claim 1, characterized in that, In step S2, the segmented graphitization calcination specifically involves: first holding at 2400-2500℃ for 1-3 hours, then raising the temperature to 2600-2700℃ and holding for 0.5-2 hours.

8. The method for catalytic graphitization according to claim 1, characterized in that, In step S2, the segmented graphitization calcination is carried out in an inert atmosphere, which is either argon or nitrogen.

9. A synthetic graphite anode material, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.

10. The application of the artificial graphite anode material according to claim 9 in lithium-ion batteries.

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