A method for preparing small-domain polarizing structure needle coke based on a harmonic homogeneous oil slurry

Abstract

The application discloses a kind of based on preparation of small domain polarizing structure needle coke of harmonic homogeneous oil slurry method, belongs to carbon material preparation technical field, it is characterized in that comprising the following steps: refined oil slurry component is mixed with rich aromatic harmonic component;Harmonic oil slurry is sent into high-pressure homogenizer and is homogenized to obtain homogenized oil slurry raw material;Homogenized oil slurry raw material is preheated to 450 DEG C and then sent into delayed coking coke tower and is coked to obtain needle coke.The beneficial effects of the present application are: by high-speed shearing homogenization, using strong shear force, friction and cavitation effect, different sources of components in oil slurry are highly uniformly dispersed at molecular level, and the microscopic concentration gradient difference between components is eliminated;The graphite microcrystal formed after graphitization of the needle coke retains a certain degree of anisotropy, i.e., ensures high capacity and first efficiency, and significantly improves the rate performance of the sample.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation technology, and more specifically relates to a method for preparing oil-based needle coke with a small-domain polarization structure, as well as the needle coke prepared by this method and its application in lithium-ion battery anode materials. Background Technology

[0002] Needle coke is a high-end carbon material characterized by high crystallinity, low coefficient of thermal expansion, high electrical conductivity, and easy graphitization. It is widely used in ultra-high power graphite electrodes, lithium-ion battery anode materials, and specialty carbon products. Based on the different raw materials used in its production, needle coke can be divided into two main categories: oil-based needle coke and coal-based needle coke. Oil-based needle coke is mainly produced from catalytic cracking (FCC) slurry oil through a delayed coking process.

[0003] In the existing technology, Firstly, the needle coke raw material obtained by simply undergoing conventional desolidification and desulfurization refining processes still has significant deficiencies in terms of component composition and molecular structure uniformity. During the mesophase formation stage of the subsequent delayed coking process, the different components (aromatics, saturated components, resins, and asphaltenes) in the raw material exhibit significant differences in reactivity during thermal conversion reactions. The reaction rates and condensation pathways of each component are inconsistent, leading to uneven formation, growth, and fusion of mesophase spheres during carbonization. Ultimately, this results in a higher content of fibers and mosaic structures in the polarized light microstructure of the needle coke product. Secondly, during the hydrotreating process of catalytic slurry, while achieving desulfurization, some aromatics are also saturated through the hydrogenation reaction and further converted into aromatics with a large number of alkyl and cycloalkyl side chains. These aromatics with side chains first undergo side chain breaking reactions during the subsequent coking process, generating a large number of small molecule hydrocarbons. These small molecule hydrocarbons continuously escape and cause disturbance to the reaction system, leading to coking and hindering the formation of small-domain polarized structures. Thirdly, in the field of lithium-ion battery anode materials, needle coke can be used as artificial graphite anode material after graphitization. However, after graphitization, the graphite material obtained from traditional needle coke has a high degree of anisotropy. During charging and discharging, lithium ions can only be inserted or extracted from the edge of the graphite layer, resulting in a longer lithium ion migration path and a smaller diffusion coefficient, which seriously affects the rate performance of the graphite anode material. At the same time, the excessively high anisotropic orientation structure can easily cause the electrode to undergo large irreversible expansion in the thickness direction during charge and discharge cycles, which seriously affects the cycle life and safety performance of the battery. Summary of the Invention

[0004] To address the aforementioned problems and overcome the shortcomings of existing technologies, this invention provides a method for preparing needle coke with a small-domain polarizing structure based on a blended homogenized slurry. Through processes such as refining and deconsolidation, directional component blending, and high-pressure homogenization, needle coke with a small-domain polarizing structure is prepared. The graphitized sample of this needle coke exhibits both excellent rate performance and low electrode expansion rate, meeting the requirements of high-end lithium battery anode applications.

[0005] A method for preparing small-domain polarizing needle coke based on blended homogeneous oil slurry includes the following steps: 1. The catalytic cracking (FCC) slurry is treated by a desolidification method to remove the catalyst powder entrained in the slurry and reduce the ash content to below 0.01 wt%. Then, it is subjected to vacuum distillation to separate the light and heavy fractions, and the middle fraction with a distillation range of 400-450℃ is collected as the refined slurry component. 2. The refined oil slurry component is mixed with an aromatic-rich blending component containing a small amount of virgin QI (needle coke raw coke crushing tailings) at a mass ratio of 4:1 to 1:4. The aromatic-rich blending component is selected from at least one of furfural extract oil, reduced-strength oil, and coking wax oil. The aromatic content of the aromatic-rich blending component is ≥80wt%, and the total content of gums and asphaltenes is ≤8wt%. 3. The blended oil slurry is fed into a high-pressure homogenizer for deep homogenization to obtain homogenized oil slurry raw material; 4. The homogenized oil slurry feedstock is preheated to 450℃ and then fed into a delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480~450℃, the operating pressure is 0.4MPa, and the coking cycle is 48h, yielding needle coke.

[0006] The beneficial effects of this invention are: Compared with the prior art, the present invention has the following beneficial effects: 1. Synergistic effect of refining and blending: Precision refining removes ash and undesirable components, directional blending optimizes the ratio of tricyclic / tetracyclic aromatic hydrocarbons, and high-pressure homogenization achieves component uniformity, avoiding disordered growth of the mesophase from the source and laying the foundation for the formation of small-domain polarization structures. 2. The role of homogenization treatment: Through high-speed shear homogenization treatment, the components from different sources in the oil slurry are highly uniformly dispersed at the molecular level by utilizing strong shear force, friction force and cavitation effect, eliminating the differences in microscopic concentration gradient between components. This not only reduces the differences in reactivity of each component in the oil slurry, but also facilitates the uniform nucleation and synchronous growth of mesophase microspheres in the entire reaction system. 3. The unique product structure results in excellent electrochemical performance: The prepared needle-shaped polarizing structure is dominated by small-domain structures with a length and width of <30μm (accounting for ≥80%). The structure is uniform, with clear boundaries, and free of fibrous or disordered structures. Unlike the wide-area streamlined fibrous structure of traditional needle-shaped polarizing structures, the graphite microcrystals formed after graphitization of this needle-shaped polarizing structure retain a certain degree of anisotropy. This ensures high capacity and first-time efficiency, while also providing more exposed layer edges and grain boundaries, increasing the active sites and diffusion channels for lithium-ion insertion / extraction. At the same time, it allows lithium ions to enter the graphite interlayer from more directions, effectively shortening the lithium-ion diffusion path and significantly improving the rate performance of the sample. The small-domain polarizing structure exhibits better structural elasticity during charge-discharge cycling. The boundaries between anisotropic units can effectively buffer the volume changes caused by lithium-ion insertion / extraction, thereby significantly reducing the irreversible thickness expansion of the electrode. Attached Figure Description

[0007] Appendix Figure 1 This is a needle-shaped polarized light image prepared in Example 1 of the present invention; Appendix Figure 2 This is a needle-shaped polarized light image prepared in Example 2 of the present invention; Appendix Figure 3 This is a needle-shaped polarized light image prepared in Example 3 of the present invention; Appendix Figure 4 This is a needle-shaped polarized light image prepared in Comparative Example 1 of the present invention; Appendix Figure 5 This is a needle-shaped polarized light image prepared in Comparative Example 2 of the present invention; Appendix Figure 6 This is a needle-shaped polarized light image prepared in Comparative Example 3 of the present invention; Appendix Figure 7 This is a needle-shaped polarized light image prepared in Comparative Example 4 of the present invention; Appendix Figure 8 This is a needle-shaped polarized light image prepared in Comparative Example 5 of the present invention; Appendix Figure 9 This is a needle-shaped polarized light image prepared in Comparative Example 6 of the present invention; Detailed Implementation

[0008] Specific details in the description of this invention are merely to provide a thorough understanding of the embodiments thereof; however, those skilled in the art should understand that the implementation of this invention is not limited to these details. Furthermore, well-known structures and functions have not been described or shown in detail to avoid obscuring the key points of the embodiments of this invention. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0009] Specific embodiments of the present invention: To better understand the present invention, specific embodiments are described. It is worth emphasizing that the effects of these embodiments are not substantially different from those of various embodiments within the scope of protection of the present invention, including their respective reagents and reagent content ratios. All of them can achieve the effects described in the present invention and solve the above-mentioned problems. Other combinations are not described here. Example 1 (1) Take catalytic cracking slurry (ash content 0.5wt%, sulfur content 0.2wt%, aromatic content 50wt%), and remove solids by conventional filtration separation to reduce the ash content to 0.01wt%. Then perform vacuum distillation, cut and collect the middle fraction with a boiling point range of 400-450℃ to obtain the refined slurry component, which has an aromatic content of 60wt% and a sulfur content of 0.2wt%.

[0010] (2) The refined oil slurry components are mixed with furfural extract oil (aromatic content 85wt%) containing 3% virgin QI (needle coke raw coke crushing tail material) at a mass ratio of 4:1, and then stirred to make them initially mixed.

[0011] (3) Heat the blended oil slurry to 100°C and homogenize it in a high-pressure homogenizer. The operating pressure is 1200 MPa and the time is 6 h, so that the components in the oil slurry can be uniformly dispersed at the molecular level.

[0012] (4) The homogenized oil slurry raw material is preheated to 450°C and then fed into the delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480-450°C, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours to obtain needle coke.

[0013] Example 2 (1) Take catalytic cracking slurry (sulfur content 0.2wt%, ash content 0.5wt%, aromatic content 50wt%), and remove solids by conventional filtration separation to reduce the ash content to 0.01wt%. Then perform vacuum distillation, cut and collect the middle fraction with a boiling point range of 400-450℃ to obtain the refined slurry component, which has an aromatic content of 60wt% and a sulfur content of 0.2wt%.

[0014] (2) The refined oil slurry components are mixed with the first-line oil (aromatic content 80wt%) containing 5% virgin QI (needle coke raw coke crushing tail material) at a mass ratio of 1:1, and then stirred to make it initially mixed.

[0015] (3) Heat the blended oil slurry to 100°C and homogenize it in a high-pressure homogenizer. The operating pressure is 1200 MPa and the time is 6 h, so that the components in the oil slurry can be uniformly dispersed at the molecular level.

[0016] (4) The homogenized oil slurry raw material is preheated to 450°C and then fed into the delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480-450°C, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours to obtain needle coke.

[0017] Example 3 (1) Take catalytic cracking slurry (sulfur content 0.2wt%, ash content 0.5wt%, aromatic content 50wt%), and remove solids by conventional filtration separation to reduce the ash content to 0.01wt%. Then perform vacuum distillation, cut and collect the middle fraction with a boiling point range of 400-450℃ to obtain refined slurry components with an aromatic content of 60wt% and a sulfur content of 0.2wt%.

[0018] (2) The refined oil slurry components are mixed with coking wax oil (aromatic content 82wt%) containing 1% virgin QI (needle coke raw coke crushing tail material) at a mass ratio of 1:4, and then stirred to make them initially mixed.

[0019] (3) Heat the blended oil slurry to 100°C and homogenize it in a high-pressure homogenizer. The operating pressure is 1200 MPa and the time is 6 h, so that the components in the oil slurry can be uniformly dispersed at the molecular level.

[0020] (4) The homogenized oil slurry raw material is preheated to 450°C and then fed into the delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480-450°C, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours to obtain needle coke.

[0021] Comparative Example 1 (1) Take catalytic cracking slurry (sulfur content 0.2wt%, ash content 0.5wt%, aromatic content 50wt%), and remove solids by conventional filtration separation to reduce the ash content to 0.01wt%. Then perform vacuum distillation, cut and collect the middle fraction with a boiling point range of 400-450℃ to obtain the refined slurry component, which has an aromatic content of 60wt% and a sulfur content of 0.2wt%.

[0022] (2) The refined oil slurry components and furfural extract (aromatic content 85wt%) are mixed at a mass ratio of 4:1, and then stirred to make them initially mixed.

[0023] (3) Heat the blended oil slurry to 100°C and homogenize it in a high-pressure homogenizer. The operating pressure is 1200 MPa and the time is 6 h, so that the components in the oil slurry can be uniformly dispersed at the molecular level.

[0024] (4) The homogenized oil slurry raw material is preheated to 450°C and then fed into the delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480-450°C, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours to obtain needle coke.

[0025] Comparative Example 2 (1) Take catalytic cracking slurry (sulfur content 0.2wt%, ash content 0.5wt%, aromatic content 50wt%), and remove solids by conventional filtration separation to reduce the ash content to 0.01wt%. Then perform vacuum distillation, cut and collect the middle fraction with a boiling point range of 400-450℃ to obtain the refined slurry component, which has an aromatic content of 60wt% and a sulfur content of 0.2wt%.

[0026] (2) The refined oil slurry components are mixed with furfural extract oil (aromatic content 85wt%) containing 3% native QI (graphene) at a mass ratio of 4:1, and then stirred to make them initially mixed.

[0027] (3) Heat the blended oil slurry to 100°C and homogenize it in a high-pressure homogenizer. The operating pressure is 1200 MPa and the time is 6 h, so that the components in the oil slurry can be uniformly dispersed at the molecular level.

[0028] (4) The homogenized oil slurry raw material is preheated to 450°C and then fed into the delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480-450°C, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours to obtain needle coke.

[0029] Comparative Example 3 (1) Take catalytic cracking slurry (sulfur content 0.2wt%, ash content 0.5wt%, aromatic content 50wt%), and remove solids by conventional filtration separation to reduce the ash content to 0.01wt%. Then perform vacuum distillation, cut and collect the middle fraction with a boiling point range of 400-450℃ to obtain the refined slurry component, which has an aromatic content of 60wt% and a sulfur content of 0.2wt%.

[0030] (2) The refined oil slurry components are mixed with furfural extract oil (aromatic content 85wt%) containing 3% virgin QI (needle coke raw coke crushing tail material) at a mass ratio of 4:1, and then stirred to mix them.

[0031] (3) The mixed raw materials are preheated to 450°C and then fed into the delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480-450°C, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours to obtain needle coke.

[0032] Comparative Example 4 (1) Take catalytic cracking slurry (sulfur content 0.2wt%, ash content 0.5wt%, aromatic content 50wt%), and remove solids by conventional filtration separation to reduce the ash content to 0.01wt%. Then perform vacuum distillation, cut and collect the middle fraction with a boiling point range of 400-450℃ to obtain the refined slurry component, which has an aromatic content of 60wt% and a sulfur content of 0.2wt%.

[0033] (2) The refined oil slurry components are mixed with furfural extract oil (aromatic content 85wt%) containing 3% virgin QI (needle-shaped coke powder) at a mass ratio of 4:1, and then stirred to mix them.

[0034] (3) The mixed raw materials are preheated to 450°C and then fed into the delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480-450°C, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours to obtain needle coke.

[0035] Comparative Example 5 (1) Take a medium-high sulfur catalytic cracking slurry (sulfur content 2.0wt%, ash content 1.0wt%, aromatic content 60wt%), use conventional vacuum distillation to cut and collect the middle fraction with a boiling point range of 350-500℃, and remove the ash. Then use conventional hydrorefining to reduce the sulfur content, thereby obtaining the refined slurry component with an aromatic content of 75wt% and a sulfur content of 0.4wt%.

[0036] (2) The refined oil slurry components are mixed with furfural extract oil (aromatic content 85wt%) containing 3% virgin QI (needle coke raw coke crushing tail material) at a mass ratio of 4:1, and then stirred to make them initially mixed.

[0037] (3) Heat the blended oil slurry to 100°C and homogenize it in a high-pressure homogenizer. The operating pressure is 1200 MPa and the time is 6 h, so that the components in the oil slurry can be uniformly dispersed at the molecular level.

[0038] (4) The homogenized oil slurry raw material is preheated to 450°C and then fed into the delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480-450°C, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours to obtain needle coke.

[0039] Comparative Example 6 (1) Take a medium-high sulfur catalytic cracking slurry (sulfur content 2.0wt%, ash content 1.0wt%, aromatic content 60wt%), use conventional vacuum distillation to cut and collect the middle fraction with a boiling point range of 350-500℃, and remove the ash. Then use conventional hydrorefining to reduce the sulfur content, thereby obtaining the refined slurry component with an aromatic content of 75wt% and a sulfur content of 0.4wt%.

[0040] (2) The refined oil slurry components are mixed with furfural extract oil (aromatic content 85wt%) containing 3% virgin QI (needle coke raw coke crushing tail material) at a mass ratio of 4:1, and then stirred to make them initially mixed.

[0041] (3) The mixed raw materials are preheated to 450°C and then fed into the delayed coking coke tower for coking reaction. The operating temperature of the coke tower is 480-450°C, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours to obtain needle coke.

[0042] The needle coke prepared in the above embodiments and comparative examples was pulverized using a conventional mechanical mill with a cyclone separator, commonly used in the graphite anode material industry. The pulverized product is characterized by a particle size D. Q =Dv50=15.0±0.5μm; then, under inert atmosphere protection, pre-carbonization and high-temperature graphitization were carried out. The pre-carbonization temperature was 800-1000℃ and the time was 1-2h. The graphitization temperature was 2800-3000℃ and the time was 2-3h, finally obtaining the graphitized sample.

[0043] Electrochemical performance testing: The negative electrode was prepared by dissolving polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) solvent, adding conductive carbon black (Super P), and stirring until homogeneous. Then, a graphitized sample (graphitized sample:PVDF:NMP:SP = 95.0:1.5:1.5:2.0) was added, and the mixture was stirred again until homogenized, completing the slurry preparation. The resulting coin cell was then coated, dried, rolled, die-cut, shaped, and assembled. The electrolyte used was 1M LiPF6 with an EC:DEC:DMC ratio of 1:1:1 (volume ratio). The positive electrode used was a lithium metal sheet. The assembled coin cells were subjected to constant current charge-discharge testing, with a charge-discharge cutoff voltage of 0.005V-2.000V and a charge-discharge program of 0.05C / 1C. Electrode expansion rate testing: The graphite negative electrode was tested using a precision digital thickness gauge with a fixed side pressure.

[0044] The performance of the needle cokes prepared in the above embodiments and comparative examples was tested, and the test performance is shown in Table 1 below. Table 1: Relevant performance indicators of needle coke prepared in different embodiments and comparative examples

[0045]

[0046] As can be seen from the data in Table 1: (1) The needle-shaped focal plane prepared in Example 1 has a polarization structure dominated by small domain structures, and the polarization image is as follows. Figure 1As shown, the sulfur content of the needle coke sample was 0.35%, and the ash content was 0.01%. After being made into a coin cell, it retained >92% of its capacity after 500 cycles at a 5C rate, and the electrode expansion rate was 4.2%. This may be because the small amount of native QI can serve as heterogeneous nuclei for mesophase nucleation, significantly increasing the number of nucleation sites in the system. Under the same reaction conditions, more and smaller mesophase spheres can be generated, which can inhibit the excessive growth of individual spheres from the nucleation stage. In addition, the blending component has an extremely high aromatic content, and the large number of aromatic molecules contained therein can be adsorbed onto the native QI through π-π interactions, thereby inhibiting the aggregation of large molecular aromatic clusters. The high content of aromatics in the component can maintain the overall aromaticity of the reaction system and ensure the orderliness of the mesophase structure. Strictly controlling the total content of resins and asphaltenes can avoid the local enrichment of highly active heavy components in the system and prevent the formation of a large number of mosaic structures due to excessively fast local reaction rates.

[0047] (2) In Comparative Example 1, without the addition of needle-shaped coke raw coke powder tailings, the polarized structure was mainly composed of large-area and fibrous structures, as shown in the polarized image. Figure 4 As shown, with a sulfur content of 0.32% and an ash content of 0.01%, after being manufactured into a coin cell, it retains >82% capacity after 500 cycles at a 5C rate, and the electrode expansion rate is 14.1%. This may be because the lack of needle coke raw coke powder tailings prevented the interruption of the mesophase growth process, resulting in the mesophase developing into a large domain and fibrous structure. This caused the lithium ion insertion and extraction path in the graphitized sample to be too long, the insertion and extraction rate to be too slow, and the rate performance to be too poor. (3) Comparative Example 2 introduces other types of QI: graphene, whose polarization structure is mainly composed of large domain and fibrous structures, and the polarization image is as follows. Figure 5 As shown, the sulfur content of the needle coke sample was 0.38%, and the ash content was 0.02%. After being made into a coin cell, it retained >84% capacity after 500 cycles at a 5C rate, and the electrode expansion rate was 12.0%. This may be due to the poor compatibility between graphene and oil slurry, and the fact that graphene is a single-layer hexagonal honeycomb structure, which cannot effectively interrupt the fusion process of the intermediate phase, resulting in the intermediate phase developing into a large domain structure. This makes the path of lithium ion insertion and extraction in its graphitized sample longer and the extraction rate slower, resulting in poor rate performance. (4) In Comparative Example 3, no homogenization treatment was applied to the components and the components were mixed. The polarized structure was mainly composed of large-area and fibrous structures. The polarized image is as follows: Figure 6 As shown, the sulfur content of the needle coke sample was 0.35%, and the ash content was 0.02%. After being made into a coin cell, it retained >83% capacity after 500 cycles at a 5C rate, and the electrode expansion rate was 12.8%. This may be due to the lack of homogenization treatment for coking raw materials, resulting in severe agglomeration of needle-shaped coke tail material and uneven dispersion. This makes it impossible to effectively interrupt the fusion process of the mesophase, leading to the mesophase developing into a large domain structure. As a result, the path of lithium ions intercalation and deintercalation in the graphitized sample is relatively long, the intercalation and deintercalation rate is slow, and the rate performance is poor. (5) Comparative Example 4 introduced other types of QI: needle-shaped charred coke powder, and no homogenization treatment was applied to the components and the mixture. The polarization structure was mainly composed of large and small domain structures, and the polarization image is as follows. Figure 7 As shown, the sulfur content of the needle coke sample was 0.37%, and the ash content was 0.01%. After being made into a coin cell, it retained >88% capacity after 500 cycles at a 5C rate, and the electrode expansion rate was 8.4%. This may be due to the introduction of needle-shaped coke powder and the lack of homogenization treatment of the coking raw materials. The needle-shaped coke powder is not evenly dispersed and cannot effectively interrupt the fusion process of the mesophase, resulting in the development of the mesophase into large and small domain structures. This makes the path of lithium ion insertion and extraction in its graphitized sample shorter and the insertion and extraction rate faster, resulting in better rate performance. (6) Comparative Example 5 used conventional medium-high sulfur oil slurry for conventional vacuum distillation and hydrorefining processes. The polarized structure was mainly large-area and fibrous structures. The polarized image is shown below. Figure 8 As shown, the sulfur content of the needle coke sample was 0.42%, and the ash content was 0.02%. After being made into a coin cell, it retained >85% capacity after 500 cycles at a 5C rate, and the electrode expansion rate was 10.9%. This may be because the hydrorefining process causes the aromatic side chains to break, generating many small molecular structures. After homogenization, these small molecular structures are more uniformly present in the reaction system, resulting in a coking effect when they overflow during the coking process. This leads to the polarization structure being dominated by fibrous and large domain structures, which makes the path of lithium ion insertion and extraction in the graphitized sample too long and the insertion and extraction rate too slow, resulting in poor rate performance. (7) Comparative Example 6 used conventional medium-high sulfur oil slurry for conventional vacuum distillation and hydrorefining processes. The polarized structure was mainly large-area and fibrous, and the polarized image is as follows: Figure 9 As shown, the sulfur content of the needle coke sample was 0.43%, and the ash content was 0.01%. After being made into a coin cell, it retained >86% capacity after 500 cycles at a 5C rate, and the electrode expansion rate was 10.1%. This may be because the hydrorefining process causes the aromatic side chains to break, generating many small molecular structures. These small molecular structures exist in the reaction system, causing a coking effect when they overflow during the coking process. As a result, the polarization structure is dominated by large domain and fibrous structures, which makes the path of lithium ions intercalation and deintercalation in the graphitized sample too long and the deintercalation rate too slow, resulting in poor rate performance.

[0048] Most importantly: Compared with Comparative Example 6, Comparative Example 5 underwent homogenization treatment, which broke the aggregation of small and large aromatic clusters. This resulted in small molecule structures being uniformly present in the reaction system, making it impossible to form aromatic micro-regions with uniform particle size. The interaction force between large and small molecules was reduced, making small molecules more likely to overflow. This led to a stronger scorching effect during the coking process, resulting in a polarization structure dominated by fibrous and large domain structures. Consequently, the electrochemical performance of the graphitized sample was worse than that of the unhomogenized sample.

[0049] In summary: This invention creatively employs the synergistic effect of refining and blending: precise refining removes ash and undesirable components, directional blending optimizes the ratio of tricyclic / tetracyclic aromatic hydrocarbons, and high-pressure homogenization achieves component uniformity, thus avoiding disordered growth of the mesophase from the source and laying the foundation for the formation of small-domain structure polarized light.

[0050] Building upon the aforementioned principles, this invention further employs a homogenization process: through high-speed shear homogenization, strong shear forces, friction, and cavitation effects are utilized to achieve highly uniform dispersion of components from different sources in the slurry at the molecular level, eliminating microscopic concentration gradient differences between components. This not only reduces the differences in reactivity among components in the slurry but also facilitates the uniform nucleation and synchronous growth of mesophase microspheres throughout the entire reaction system.

[0051] The unique product structure leads to excellent electrochemical performance: the prepared needle-coil polarizing structure is dominated by small-domain structures with a length and width of <30μm (accounting for ≥80%), with uniform structure, clear boundaries, and no fibrous or disordered structures, which is different from the wide-area streamlined fibrous structure of traditional needle coil. The graphite microcrystals formed after graphitization of this needle coil retain a certain degree of anisotropy (ensuring high capacity and first-pass efficiency) and have more exposed layer edges and grain boundaries (increasing active sites and diffusion channels for lithium ion insertion / extraction). At the same time, it allows lithium ions to enter the graphite interlayer from more directions, effectively shortening the lithium ion diffusion path and significantly improving the rate performance of the sample; the small-domain polarizing structure exhibits better structural elasticity during charge-discharge cycling, and the boundaries between anisotropic units can effectively buffer the volume changes caused by lithium ion insertion / extraction, thereby significantly reducing the irreversible thickness expansion of the electrode.

Claims

1. A method for preparing small-domain polarizing needle coke based on blended homogeneous oil slurry, characterized in that... Includes the following steps: (1) The catalytic cracking FCC slurry is treated by a desolidification method, and then subjected to vacuum distillation to separate light and heavy fractions. The middle fraction with a distillation range of 400-450℃ is collected as the refined slurry component. (2) The refined oil slurry component is mixed with an aromatic blending component containing a small amount of needle coke raw coke crushing tailings; (3) The blended oil slurry is fed into a high-pressure homogenizer for homogenization to obtain homogenized oil slurry raw material; (4) After the homogenized oil slurry raw material is preheated to 450°C, it is sent to the delayed coking coke tower for coking reaction to obtain needle coke.

2. The method for preparing small-domain polarizing needle coke based on blended homogeneous slurry according to claim 1, characterized in that... The refined oil slurry component and the aromatic hydrocarbon blending component are mixed at a mass ratio of 4:1 to 1:

4.

3. The method for preparing small-domain polarizing needle coke based on blended homogeneous slurry according to claim 1, characterized in that... The aromatic-rich blending component is at least one of furfural extract oil, reduced-strength oil, and coking wax oil, and the aromatic content of the aromatic-rich blending component is ≥80wt%, and the total content of gums and asphaltenes is ≤8wt%.

4. The method for preparing small-domain polarizing needle coke based on blended homogeneous slurry according to claim 1, characterized in that... The operating temperature of the coke tower is 480–450℃, the operating pressure is 0.4 MPa, and the coking cycle is 48 hours.

5. A method for preparing small-domain polarizing needle coke based on a blended homogeneous slurry according to any one of claims 1-4, characterized in that... The homogenization process was performed under the following conditions: pressure of 1200 MPa and time of 6 hours.

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