Preparation method of artificial graphite, artificial graphite and secondary battery

Abstract

The invention provides a preparation method of artificial graphite, the artificial graphite and a secondary battery. The preparation method of the artificial graphite comprises the steps that a coke raw material is crushed and then subjected to first heat treatment to obtain a calcined material, the sulfur content of the coke raw material is Xwt.%, the final temperature of the first heat treatment is Y DEG C, and Y = BX + k; shaping and graphitizing the calcined material to obtain a first precursor; the first precursor and first solid asphalt are mixed and then granulated to obtain a second precursor, the softening point of the first solid asphalt is 150-250 DEG C, the final temperature of granulation is not higher than 600 DEG C, and the ratio of 2 # Dv01 to 1 # Dv01 is 1.5-1.8; and carbonizing the second precursor, scattering, screening and demagnetizing. According to the preparation method, the final temperature in the heat treatment process is determined according to the sulfur content in the coke raw material, so that the waste of processing cost is avoided, and the influence on the material performance is avoided. And the carbon structure of the desulfurized graphite is repaired by combining specific asphalt and controlling the particle size of particles in graphitization and granulation so as to avoid the influence of sulfur reduction on the performance of the material.

Description

Technical Field

[0001] This invention relates to the field of new energy material preparation technology, and in particular to a method for preparing artificial graphite and its artificial graphite and secondary batteries. Background Technology

[0002] Artificial graphite is widely used in secondary batteries due to its excellent cycle stability; however, currently produced artificial graphite usually contains some sulfur. The reasons for this are mainly as follows.

[0003] (1) Derived from raw materials Artificial graphite is typically made from coke raw materials such as petroleum coke. These raw materials are formed from the remains of ancient organisms and contain sulfur. Their sulfur content is usually between 0.5% and 5 wt.%, or even higher, resulting in artificial graphite with a high sulfur content.

[0004] (2) Derived from coating materials such as asphalt Because graphite materials have poor compatibility with electrolytes, graphite sheet peeling is prone to occur during charge and discharge due to co-intercalation of solvated lithium ions, leading to an increase in irreversible capacity and consequently a decrease in cycle performance and rate capability. Therefore, a coating layer is usually constructed on the graphite surface to reduce side reactions with the electrolyte and promote the formation of a stable electrode interface. This coating is mostly made of bitumen, which serves as a binder and impregnating agent during graphite molding. Bitumen is a residue from coal tar distillation; coal is a fossil fuel and is also rich in sulfur. The sulfur content of bitumen is typically around 0.5% to 1.5%. During graphite roasting and graphitization, bitumen carbonizes, and most of its sulfur content remains in the final graphite product.

[0005] (3) Caused by oxidation Traditionally, coating graphite and bitumen is done using a physical mixing and heating method, which easily leads to uneven coating thickness, poor repeatability, and significant batch-to-batch differences in electrochemical performance. Furthermore, the weak interaction between graphite and the carbon shell makes the coating prone to lifting and peeling after carbonization, affecting cycle stability. To improve the bonding between the graphite matrix and the coating material, the industry has also used sulfuric acid to oxidize the graphite matrix before coating. During oxidation, sulfuric acid molecules forcibly insert into the interlayer structure of the graphite. Even after subsequent washing, neutralization, and drying, it is difficult to completely remove 100% of the sulfate ions from the interlayers. These residual sulfur become impurities in the final artificial graphite.

[0006] The residual sulfur in artificial graphite reacts with impurity metals (such as iron and nickel) in the graphite at high temperatures to form low-melting-point sulfides, which greatly affects the high-temperature performance of artificial graphite. The presence of sulfur impurities also seriously interferes with its electron transport. Furthermore, during the graphitization process, sulfur escapes in gaseous form (such as CS2), leaving tiny pores and defects inside the material, which leads to a decrease in the density of graphite and damages the mechanical properties and structural integrity of the material.

[0007] Therefore, sulfur reduction needs to be considered in the preparation of artificial graphite. Whether it is mixing coke raw materials such as petroleum coke with raw materials such as asphalt and then calcining them at high temperature before molding, or using high temperature treatment during graphitization, although it can reduce sulfur well, it not only generates a lot of energy consumption and high production costs, but also excessive sulfur reduction (such as long-term high-temperature calcination) will lead to carbon layer cracking, increase specific surface area, and decrease capacity.

[0008] Therefore, how to effectively reduce sulfur content without causing high energy consumption and obtain artificial graphite with high mechanical and electrochemical properties is a topic that the industry needs to consider. Summary of the Invention

[0009] In view of the above problems, the purpose of this invention is to provide a method for preparing artificial graphite and the artificial graphite and secondary batteries thereof. The preparation method of this invention comprehensively considers the relationship between the sulfur content in the coke feedstock and the heat treatment temperature. The sulfur content in the coke feedstock is used to determine the endpoint temperature during the heat treatment process, avoiding waste of processing costs and minimizing impact on material properties. Furthermore, specific asphalt and particle size control during graphitization and granulation are combined to repair the carbon structure of the desulfurized graphite to avoid the impact of sulfur reduction on material properties.

[0010] To achieve the above objectives, the first aspect of the present invention provides a method for preparing artificial graphite, comprising the steps of: (I) The coke raw material is crushed and subjected to a first heat treatment to obtain calcined material. The sulfur content of the coke raw material is X wt.%, and the final temperature of the first heat treatment is Y °C, satisfying the relationship Y=BX+k, with an error of ±10, where X is 1.5~3.0, B is a calculation coefficient with a value range of 50~200, and k is a calculation constant with a value range of 200~400; (II) The calcined material is shaped and graphitized to obtain a first precursor, wherein the Dv01 of the first precursor is 1#Dv01; (III) The first precursor and the first solid asphalt are mixed and granulated to obtain the second precursor. The softening point of the first solid asphalt is 150~250℃, and the final temperature of the granulation is not higher than 600℃. The Dv01 of the second precursor is 2#Dv01, and the ratio of 2#Dv01 to 1#Dv01 is 1.5~1.8. (IV) The second precursor is carbonized and then broken up, sieved and demagnetized.

[0011] In the preparation method of this invention, the coke raw material undergoes a first heat treatment to reduce sulfur content. Considering the relationship between the sulfur content in the coke raw material and the heat treatment temperature, the final temperature Y during the heat treatment process is determined using the formula Y=BX+k, based on the sulfur content in the coke raw material. This avoids wasting processing costs and prevents the impact of excessively high temperatures on the performance of the material particles. In granulation, a first solid asphalt with a softening point of 150~250℃ is selected as the coating agent, and the final granulation temperature does not exceed 600℃. At this low granulation temperature, the asphalt with a lower softening point exhibits good high-temperature fluidity and reaches a metastable viscosity at lower temperatures. It can bind the first precursor fine powder, achieving both coating and granulation purposes, improving the orderliness of the carbon layer, modifying the surface morphology of graphitized products, and avoiding subsequent processing problems caused by asphalt coking at high temperatures. After carbonization, the asphalt coating layer exhibits superior density, further reducing surface defects and thus improving the electrochemical performance of the material. Controlling the particle size during graphitization and granulation to ensure the ratio of 2#Dv01 to 1#Dv01 is 1.5~1.8 effectively controls the generation of fine powder and large particles, resulting in denser secondary particles after granulation. This significantly improves the tap density of artificial graphite, reducing voids and defects during granulation and minimizing the impact of porosity and defects caused by desulfurization on material properties. Therefore, determining the endpoint temperature during heat treatment by controlling the sulfur content in the coke feedstock avoids wasted processing costs and the negative impact of excessive desulfurization on material properties. Combined with specific asphalt and particle size control during graphitization and granulation, the carbon structure of desulfurized graphite can be repaired to prevent the negative effects of desulfurization on material properties.

[0012] As one technical solution of the present invention, Y is 500~900 and X is 1.5~3.0.

[0013] As a technical solution of the present invention, the difference between 2#Dv01 and 1#Dv01 is 1~2μm.

[0014] As one technical solution of the present invention, 1#Dv01 is 2~4μm and 2#Dv01 is 3~6μm.

[0015] As one technical solution of the present invention, the coke raw material is selected from at least one of needle coke, calcined needle coke, petroleum coke, calcined petroleum coke and isotropic coke.

[0016] As one technical solution of the present invention, the volatile matter content of the coke raw material is 5-15%.

[0017] As a technical solution of the present invention, the particle size of the calcined material after shaping satisfies the following: Dv01 > 2μm, Dv10 is 4~6μm, Dv50 is 8~12μm, Dv90 is 19~23μm, and Dv99 < 30μm.

[0018] As a technical solution of the present invention, the heating rate of the first heat treatment is 1~10℃ / min, and the holding time of the first heat treatment is 1~4h.

[0019] As a technical solution of the present invention, an inert gas is introduced in the first heat treatment, and the flow rate of the inert gas is >1L / min.

[0020] As one technical solution of the present invention, the graphitization temperature is 2900~3200℃, and the degree of graphitization after graphitization is 92~98%.

[0021] As a technical solution of the present invention, the particle size of the first precursor satisfies the following: Dv10 is 4~6μm, Dv50 is 9~14μm, Dv90 is 19~25μm, and Dv99 is <32μm.

[0022] As a technical solution of the present invention, the Dv50 of the first solid asphalt is 2~5μm. As a technical solution of the present invention, the residual carbon value of the first solid asphalt is 50~70 wt.%.

[0023] As one technical solution of the present invention, the mass ratio of the first precursor to the first solid asphalt is 100:3~6.

[0024] As a technical solution of the present invention, the mixing time of the first precursor and the first solid asphalt is 0.5~2.0h.

[0025] As one technical solution of the present invention, the final temperature of granulation is 400~600℃, the heating rate is 1~5℃ / min, the holding time at the final temperature is 1~6h, and the rotation speed is 10~30Hz. As a technical solution of the present invention, the particle size of the second precursor is Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99 < 35μm.

[0026] As one technical solution of the present invention, the final temperature of carbonization is 1000~1200℃, the heating rate is 1~10℃ / min, the holding time at the final temperature is 2~3h, and the total carbonization time is 12~14h. As a technical solution of the present invention, an inert gas is introduced during the granulation process, and the flow rate of the inert gas is >1L / min.

[0027] As a technical solution of the present invention, an inert gas is introduced during the carbonization process, and the flow rate of the inert gas is >1L / min.

[0028] As a technical solution of the present invention, the shaped material and the second solid asphalt are mixed and then graphitized, wherein the second solid asphalt accounts for 0.1 to 1.0% of the mass of the material.

[0029] As one technical solution of the present invention, the Dv50 of the second solid asphalt is 2~6μm. As one technical solution of the present invention, the softening point of the second solid asphalt is 200~300℃.

[0030] As one technical solution of the present invention, the residual carbon value of the second solid asphalt is 60~80 wt.%.

[0031] A second aspect of the present invention provides an artificial graphite with a tap density ≥ 1.0 g / cm³. 3 It comprises a graphite core and an amorphous carbon layer covering the graphite core. This synthetic graphite has a high tap density, which improves the processing performance of the subsequent negative electrode.

[0032] As one technical solution of the present invention, Dv10 is 6~8μm.

[0033] As one technical solution of the present invention, Dv50 is 11~14μm.

[0034] As one technical solution of the present invention, Dv90 is 22~25μm.

[0035] As one technical solution of the present invention, Dv99 is 30~40μm.

[0036] As one technical solution of the present invention, the amorphous carbon layer accounts for 2-6% of the mass of the artificial graphite.

[0037] As one technical solution of the present invention, the specific surface area is 1.4~1.6m². 2 / g.

[0038] As one technical solution of the present invention, the initial discharge capacity is ≥352mAh / g.

[0039] As one technical solution of the present invention, the initial coulombic efficiency is ≥92%.

[0040] As one technical solution of the present invention, the 3C discharge capacity retention rate is ≥80%.

[0041] A third aspect of the present invention provides a secondary battery comprising a positive electrode material, a separator, an electrolyte, and a negative electrode material, wherein the negative electrode material comprises the aforementioned artificial graphite. Attached Figure Description

[0042] Figure 1 The image shows the artificial graphite prepared in Example 1 magnified 1000 times using a scanning electron microscope.

[0043] Figure 2 The image shows the artificial graphite prepared in Example 1 magnified 3000 times using a scanning electron microscope.

[0044] Figure 3 The image shows the artificial graphite prepared in Comparative Example 1 magnified 1000 times using a scanning electron microscope.

[0045] Figure 4 The image shows the artificial graphite prepared in Comparative Example 1 magnified 3000 times using a scanning electron microscope. Detailed Implementation

[0046] The artificial graphite of this invention can be used alone or in combination with other negative electrode active materials (such as natural graphite, silicon-oxygen materials, silicon-carbon materials, soft carbon and / or hard carbon, etc.). Artificial graphite can be applied in secondary batteries, which include positive electrode materials, separators, electrolytes, and negative electrode materials. The positive electrode material includes layered oxide series lithium-ion positive electrode materials or olivine-type lithium-ion positive electrode materials. Layered oxide series lithium-ion positive electrode materials can be lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide. Olivine-type lithium-ion positive electrode materials can be lithium iron phosphate or lithium manganese iron phosphate. The separator can be a polyethylene or polypropylene separator. The electrolyte may include lithium salts, non-aqueous organic solvents, and conventional additives. The lithium salt may be selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate-borate), lithium difluorophosphate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium lower aliphatic carboxylic acids, lithium difluorobis(oxalate-phosphate), lithium bis(fluorosulfonyl)imide, lithium chloroborane, and lithium tetraphenylborate. The non-aqueous organic solvent is selected from at least one of γ-butyrolactone, γ-valerolactone, δ-valerolactone, methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, propyl propionate, butyl propionate, ethylene carbonate, propylene carbonate, butyl carbonate, methyl pentyl carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, propylene carbonate, 1,3-dioxane, 1,4-dioxane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2-trifluoromethyltetrahydrofuran, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. The additive may be at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfite, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,4-butanesulfonate lactone, and vinyl sulfate.

[0047] The artificial graphite of this invention can be used as a negative electrode active material in secondary batteries, with an initial discharge capacity ≥352 mAh / g. Examples, but not limited to, 352 mAh / g, 353 mAh / g, 354 mAh / g, 355 mAh / g, 356 mAh / g, 357 mAh / g, 358 mAh / g, 359 mAh / g, and 360 mAh / g. The initial coulombic efficiency ≥92%, examples, but not limited to, 92%, 93%, 94%, and 95%. The 3C discharge capacity retention rate ≥80%, examples, but not limited to, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, and 90%.

[0048] The artificial graphite of this invention comprises a graphite core and an amorphous carbon layer coating the graphite core. The amorphous carbon layer is formed by coating with pitch, and the mass percentage of the amorphous carbon layer in the artificial graphite is 2-6%. For example, the mass percentage may be, but is not limited to, 2%, 3%, 4%, 5%, or 6%. The tap density is ≥1.0 g / cm³. 3 As an example, it can be, but is not limited to, 1.0 g / cm³. 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 Dv10 has a diameter of 6–8 μm, but is not limited to 6 μm, 7 μm, or 8 μm. Dv50 has a diameter of 11–14 μm, but is not limited to 11 μm, 12 μm, 13 μm, or 14 μm. Dv90 has a diameter of 22–25 μm, but is not limited to 22 μm, 23 μm, 24 μm, or 25 μm. Dv99 has a diameter of 30–40 μm, but is not limited to 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, or 40 μm. The specific surface area is 1.4–1.6 m². 2 / g, as an example, can be, but is not limited to, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g.

[0049] The method for preparing artificial graphite according to the present invention may include the following steps.

[0050] (I) The coke raw material is crushed and then subjected to a first heat treatment to obtain calcined material.

[0051] (II) The calcined material is shaped and graphitized to obtain the first precursor.

[0052] (III) The first precursor and the first solid asphalt are mixed and granulated to obtain the second precursor.

[0053] (IV) The second precursor is carbonized and then broken down, sieved and demagnetized.

[0054] In step (I), the coke raw material is selected from at least one of needle coke, calcined needle coke, petroleum coke, calcined petroleum coke, and isotropic coke. The volatile matter content of the coke raw material is low, ranging from 5% to 15%. Examples, but not limited to, are 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, and 15%. The coke raw material is usually in block form and can be crushed using a jaw crusher and subjected to a first heat treatment in a continuous reactor to remove water, volatile matter, and sulfur, achieving a removal rate of up to 85% for impurities such as water and volatile matter.

[0055] The sulfur content of the coke feedstock is X wt.%, and the final temperature of the first heat treatment is Y℃. By testing the desulfurization of coke feedstocks with different sulfur contents at high temperatures, the sulfur content at different stages above 500℃ was statistically analyzed. A linear fit was then performed on the sulfur content and calcination temperature, initially confirming that they satisfy the relationship Y=BX+k, with an error of ±10 for Y. B is a calculation coefficient ranging from 50 to 200, and k is a calculation constant ranging from 200 to 400. Determining the final temperature Y in the heat treatment process by using the sulfur content in the coke feedstock avoids wasting processing costs and prevents the adverse effects of excessively high temperatures on the performance of the material particles. As one technical solution of the present invention, X is 1.5~3.0, and Y is 500~900. For example, X can be, but is not limited to, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0, and Y can be, but is not limited to, 500, 550, 600, 650, 700, 750, 800, 850, or 900. The heating rate of the first heat treatment is 1~10℃ / min. For example, the heating rate can be, but is not limited to, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min. The holding time for the first heat treatment is 1 to 4 hours, and for example, it can be, but is not limited to, 1 hour, 2 hours, 3 hours, or 4 hours. An inert gas is introduced during the first heat treatment, and the flow rate of the inert gas is >1 L / min. The inert atmosphere is selected from nitrogen, argon, helium, and neon, and the flow rate can be, but is not limited to, 2 L / min, 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, or 10 L / min.

[0056] In step (II), the calcined material can be processed by a mechanical mill and a shaping machine to obtain shaped material. The particle size after shaping meets the following requirements: Dv01 > 2μm, Dv10 is 4~6μm, Dv50 is 8~12μm, Dv90 is 19~23μm, and Dv99 < 30μm.

[0057] After shaping and before graphitization, a small amount of second solid asphalt can be selectively added to prevent powder spraying of the graphitized material and to improve the graphitization yield. The second solid asphalt and the shaped material can be mixed in a batch mixer and then transferred to a box furnace for graphitization. The second solid asphalt accounts for 0.1% to 1.0% of the material mass, and for example, it can be, but is not limited to, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0%. The Dv50 of the second solid asphalt is 2 to 6 μm, and for example, it can be, but is not limited to, 2 μm, 3 μm, 4 μm, 5 μm, or 6 μm. The softening point of the second solid asphalt is 200~300℃. For example, the softening point may be, but is not limited to, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, and 300℃. The residual carbon value of the second solid asphalt is 60~80 wt.%. For example, the residual carbon value may be, but is not limited to, 60 wt.%, 62 wt.%, 64 wt.%, 66 wt.%, 68 wt.%, 70 wt.%, 72 wt.%, 74 wt.%, 76 wt.%, 78 wt.%, and 80 wt.%. The graphitization temperature is 2900~3200℃. For example, it may be, but is not limited to, 2900℃, 3000℃, 3100℃, and 3200℃. The degree of graphitization after graphitization is 92-98%, and for example, it may be, but is not limited to, 92%, 93%, 94%, 95%, 96%, 97%, and 98%. Graphitization is carried out under an inert gas atmosphere with a flow rate >1 L / min. The inert atmosphere is selected from nitrogen, argon, helium, and neon, and the flow rate may be, but is not limited to, 2 L / min, 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, and 10 L / min. The pressure for graphitization is atmospheric pressure to a slightly positive pressure of 0.08 MPa. After graphitization, a first precursor is obtained, and the Dv01 of the first precursor is 1#Dv01, which has a size of 2-4 μm, and for example, it may be, but is not limited to, 2 μm, 3 μm, and 4 μm. The particle size of the first precursor satisfies the following conditions: Dv10 is 4~6μm, Dv50 is 9~14μm, Dv90 is 19~25μm, and Dv99 is <32μm.

[0058] In step (III), the softening point of the first solid asphalt is 150~250℃, and the final granulation temperature is not higher than 600℃. At the low granulation temperature (final temperature not higher than 600℃), the first solid asphalt, utilizing its good high-temperature fluidity and ability to reach a metastable viscosity at lower temperatures, can bind the first precursor fine powder, achieving both coating granulation and reducing sulfur volatilization loss, while also improving the orderliness of the carbon layer, modifying the surface morphology of graphitized products, and avoiding subsequent processing problems caused by asphalt coking at high temperatures. The Dv50 of the first solid asphalt is 2~5μm; for example, Dv50 can be, but is not limited to, 2μm, 3μm, 4μm, or 5μm. The softening point of the first solid asphalt can be, but is not limited to, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃. The residual carbon value of the first solid asphalt is 50~70 wt.%, and for example, the residual carbon value may be, but is not limited to, 50 wt.%, 52 wt.%, 54 wt.%, 56 wt.%, 58 wt.%, 60 wt.%, 62 wt.%, 64 wt.%, 66 wt.%, 68 wt.%, or 70 wt.%. The mass ratio of the first precursor to the first solid asphalt is 100:3~6, and for example, it may be, but is not limited to, 100:3, 100:4, 100:5, or 100:6. The mixing time of the first precursor and the first solid asphalt is 0.5~2.0 h, and for example, it may be, but is not limited to, 0.5 h, 1.0 h, or 2.0 h. The final granulation temperature is 400~600℃, the heating rate is 1~5℃ / min, the holding time at the final temperature is 1~6 h, and the rotation speed is 10~30 Hz. Granulation can be performed in a vertical reactor with an inert gas flow rate > 1 L / min. The Dv01 of the second precursor is 2#Dv01, with a particle size of 3~6 μm. Examples include, but are not limited to, 3 μm, 4 μm, 5 μm, and 6 μm. The ratio of 2#Dv01 to 1#Dv01 is 1.5~1.8. Examples include, but are not limited to, 1.5, 1.6, 1.7, and 1.8. The difference between 2#Dv01 and 1#Dv01 is 1~2 μm. Examples include, but are not limited to, 1 μm and 2 μm. The particle size of the second precursor satisfies the following conditions: Dv10 is 7~9 μm, Dv50 is 13~15 μm, Dv90 is 24~28 μm, and Dv99 < 38 μm.

[0059] The carbonization in step (IV) can be carried out in a carbonization roller kiln, with a final carbonization temperature of 1000~1200℃, a heating rate of 1~10℃ / min, a holding time at the final temperature of 2~3h, and a total carbonization time of 12~14h. For example, the final carbonization temperature can be, but is not limited to, 1000℃, 1050℃, 1100℃, 1150℃, or 1200℃. The heating rate can be, but is not limited to, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min. The holding time can be, but is not limited to, 2h or 3h. The total carbonization time can be, but is not limited to, 12h, 13h, or 14h. An inert gas is introduced during carbonization, with a flow rate >1L / min. After carbonization, it can be broken down by grinding with rods, premixed, sieved with a 250-mesh sieve, and demagnetized.

[0060] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting the invention. The embodiments of this invention include descriptions of the technical solution for artificial graphite and the technical solution for the preparation method of artificial graphite.

[0061] Example 1 This embodiment describes a method for preparing artificial graphite, which includes the following steps.

[0062] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 3%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 750℃ according to the relationship Y=150X+300, the heating rate is 5℃ / min, the inert gas (nitrogen, purity ≥ 99.9%, flow rate 3L / min) is used for protection, the pressure is slightly positive 0.05MPa, the stirring speed in the reactor is 30r / min, and the temperature is maintained at 750℃ for 1h to obtain the calcined material.

[0063] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 200℃, Dv50 2~5μm, residual carbon value 60%) in a batch mixer at a spindle speed of 50r / min for 40min. Then it was fed into a box furnace and graphitized at 3000℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.08MPa to achieve a graphitization degree of 94%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0064] (III) The first precursor and solid asphalt (4% of the mass of the first precursor, softening point of 200℃, Dv50 of 2~5μm, and residual carbon value of 60%) were mixed in a batch mixer at a spindle speed of 50r / min for 40min and then fed into a vertical reactor for post-granulation. The temperature was raised to 600℃ at a rate of 4℃ / min under a stirring speed of 25Hz and held for 90min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0065] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1150°C at a rate of 8°C / min. It is then held at this temperature for 2.5 hours under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 14 hours, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0066] The synthesized artificial graphite was subjected to scanning electron microscopy (SEM) analysis. Images at 1000x and 3000x magnification are shown below. Figure 1 and Figure 2 As shown. By Figure 1 Can Figure 2 It can be seen that the artificial graphite has a good morphology and few broken particles and fine powders, indicating that the artificial graphite can effectively avoid problems such as sedimentation, high viscosity, difficulty in sieving, and particle scratches in the subsequent preparation of negative electrode slurry.

[0067] Example 2 This embodiment describes a method for preparing artificial graphite, which includes the following steps.

[0068] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 2.2%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 630℃ according to the relationship Y=150X+300, the heating rate is 5℃ / min, inert gas (nitrogen, purity ≥ 99.9%, flow rate 3L / min) protection is provided, the pressure is slightly positive 0.05MPa, the stirring speed in the reactor is 30r / min, and the temperature is maintained at 630℃ for 2h to obtain the calcined material.

[0069] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 200℃, Dv50 2~5μm, residual carbon value 60%) in a batch mixer at a spindle speed of 50r / min for 40min. Then it was fed into a box furnace and graphitized at 3000℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.08MPa to achieve a graphitization degree of 94%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0070] (III) The first precursor and solid asphalt (5% of the mass of the first precursor, softening point of 150℃, Dv50 of 2~5μm, and residual carbon value of 50%) are mixed in a batch mixer at a spindle speed of 50r / min for 40min and then fed into a vertical reactor for post-granulation. The temperature is raised to 500℃ at a rate of 4℃ / min under a stirring speed of 30Hz and held for 120min to obtain a second precursor with Dv01>3.0μm and Dv10 satisfying: Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0071] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1150°C at a rate of 8°C / min. It is then held at this temperature for 2.5 hours under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 14 hours, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0072] Example 3 This embodiment describes a method for preparing artificial graphite, which includes the following steps.

[0073] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 1.5%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 525℃ according to the relationship Y=150X+300, the heating rate is 5℃ / min, inert gas (nitrogen, purity ≥99.9%, flow rate 3L / min) protection is provided, the pressure is slightly positive 0.05MPa, the stirring speed in the reactor is 30r / min, and the temperature is maintained at 525℃ for 3h to obtain the calcined material.

[0074] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 250℃, Dv50 2~5μm, residual carbon value 70%) in a batch mixer at a spindle speed of 50r / min for 40min. Then it was fed into a box furnace and graphitized at 3000℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.08MPa to achieve a graphitization degree of 94%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0075] (III) The first precursor and solid asphalt (3% of the mass of the first precursor, softening point of 250℃, Dv50 of 2~5μm, and residual carbon value of 70%) were mixed in a batch mixer at a spindle speed of 50r / min for 40min and then fed into a vertical reactor for post-granulation. The temperature was raised to 600℃ at a rate of 4℃ / min under a stirring speed of 20Hz and held for 120min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0076] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1150°C at a rate of 8°C / min. It is then held at this temperature for 2.5 hours under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 14 hours, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0077] Example 4 This embodiment describes a method for preparing artificial graphite, which includes the following steps.

[0078] (I) The lumpy petroleum coke (feed particle size > 40 mm, sulfur content 2%, volatile matter 12%) is crushed into 20-40 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 710 °C according to the relationship Y=180X+350, the heating rate is 5 °C / min, inert gas (nitrogen, purity ≥ 99.9%, flow rate 3 L / min) protection is provided, the pressure is slightly positive 0.08 MPa, the stirring speed in the reactor is 40 r / min, and the temperature is maintained at 710 °C for 2 h to obtain the calcined material.

[0079] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~6μm, Dv50 is 8~10μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 200℃, Dv50 2~5μm, residual carbon value 60%) in a batch mixer at a spindle speed of 60r / min for 40min. Then it was fed into a box furnace and graphitized at 3200℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.05MPa to achieve a graphitization degree of 93%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <30μm.

[0080] (III) The first precursor and solid asphalt (4% of the mass of the first precursor, softening point of 200℃, Dv50 of 2~5μm, and residual carbon value of 60%) were mixed in a batch mixer at a spindle speed of 40r / min for 30min and then fed into a vertical reactor for post-granulation. The temperature was raised to 600℃ at a rate of 4℃ / min under a stirring speed of 25Hz and held for 90min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0081] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1100℃ at a rate of 10℃ / min. It is then held at this temperature for 2.0h under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 12h to obtain high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved by a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0082] Example 5 This embodiment describes a method for preparing artificial graphite, which includes the following steps.

[0083] (I) The lumpy petroleum coke (feed particle size > 40 mm, sulfur content 2%, volatile matter 12%) is crushed into 20-40 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 710 °C according to the relationship Y=180X+350, the heating rate is 8 °C / min, the inert gas (argon, purity ≥ 99.9%, flow rate 5 L / min) is used for protection, the pressure is slightly positive 0.08 MPa, the stirring speed in the reactor is 40 r / min, and the temperature is maintained at 710 °C for 2 h to obtain the calcined material.

[0084] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 200℃, Dv50 2~5μm, residual carbon value 60%) in a batch mixer at a spindle speed of 40r / min for 40min. Then it was fed into a box furnace and graphitized at 3200℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.05MPa to achieve a graphitization degree of 96%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0085] (III) The first precursor and solid asphalt (4% of the mass of the first precursor, softening point of 200℃, Dv50 of 3~5μm, and residual carbon value of 60%) were mixed in a batch mixer at a spindle speed of 45r / min for 30min and then fed into a vertical reactor for post-granulation. The temperature was raised to 600℃ at a rate of 5℃ / min under a stirring speed of 25Hz and held for 90min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0086] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1050°C at a rate of 8°C / min. It is then held at this temperature for 2.0 h under argon protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 12 h, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0087] Example 6 This embodiment describes a method for preparing artificial graphite, which includes the following steps.

[0088] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 3%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 760℃ according to the relationship Y=150X+300, the heating rate is 8℃ / min, the inert gas (nitrogen, purity ≥ 99.9%, flow rate 5L / min) is used for protection, the pressure is slightly positive 0.05MPa, the stirring speed in the reactor is 30r / min, and the temperature is maintained at 750℃ for 1h to obtain the calcined material.

[0089] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.8% of asphalt (softening point 280℃, Dv50 2~4μm, residual carbon value 75%) in a batch mixer at a spindle speed of 50r / min for 40min. Then it was fed into a box furnace and graphitized at 3100℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.09MPa to achieve a graphitization degree of 95%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0090] (III) The first precursor and solid asphalt (3% of the mass of the first precursor, softening point of 200℃, Dv50 of 2~5μm, and residual carbon value of 60%) are mixed in a batch mixer at a spindle speed of 45r / min for 45min and then fed into a vertical reactor for post-granulation. The temperature is raised to 600℃ at a rate of 5℃ / min under a stirring speed of 25Hz and held for 120min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0091] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1100℃ at a rate of 5℃ / min. It is then held at this temperature for 2.0h under argon protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 12h to obtain high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved by a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0092] Example 7 This embodiment describes a method for preparing artificial graphite, which includes the following steps.

[0093] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 3%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 750℃ according to the relationship Y=150X+300, the heating rate is 5℃ / min, the inert gas (nitrogen, purity ≥ 99.9%, flow rate 3L / min) is used for protection, the pressure is slightly positive 0.05MPa, the stirring speed in the reactor is 30r / min, and the temperature is maintained at 750℃ for 1h to obtain the calcined material.

[0094] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2 μm, Dv10 4~5 μm, Dv50 8~11 μm, Dv90 19~20 μm, and Dv99 < 30 μm. Then, it is fed into a box furnace and graphitized at 3000℃ under inert gas (nitrogen, purity ≥ 99.9%) protection and atmospheric pressure to slightly positive pressure 0.08 MPa to achieve a graphitization degree of 94%, resulting in a first precursor with 2.5 μm ≤ Dv01, Dv10 4~5 μm, Dv50 9~11 μm, Dv90 19~20 μm, and Dv99 < 32 μm.

[0095] (III) The first precursor and solid asphalt (4% of the mass of the first precursor, softening point of 200℃, Dv50 of 2~5μm, and residual carbon value of 60%) are mixed in a batch mixer at a spindle speed of 50r / min for 40min and then fed into a vertical reactor for post-granulation. The temperature is raised to 600℃ at a rate of 4℃ / min under a stirring speed of 25Hz and held for 90min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<35μm.

[0096] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1150°C at a rate of 8°C / min. It is then held at this temperature for 2.5 hours under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 14 hours, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0097] Comparative Example 1 This comparative example illustrates a method for preparing artificial graphite, comprising the following steps.

[0098] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 1%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 600℃ (calculated to be 450℃ according to the relationship Y=150X+300), the heating rate is 5℃ / min, inert gas (nitrogen, purity ≥ 99.9%, flow rate 3L / min) is used for protection, the pressure is slightly positive 0.05MPa, the stirring speed in the reactor is 30r / min, and the temperature is maintained at 600℃ for 1h to obtain the calcined material.

[0099] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 200℃, Dv50 2~5μm, residual carbon value 60%) in a batch mixer at a spindle speed of 50r / min for 40min. Then it was fed into a box furnace and graphitized at 3000℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.08MPa to achieve a graphitization degree of 94%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0100] (III) The first precursor and solid asphalt (4% of the mass of the first precursor, softening point of 200℃, Dv50 of 2~5μm, and residual carbon value of 60%) were mixed in a batch mixer at a spindle speed of 50r / min for 40min and then fed into a vertical reactor for post-granulation. The temperature was raised to 600℃ at a rate of 4℃ / min under a stirring speed of 25Hz and held for 90min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0101] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1150°C at a rate of 8°C / min. It is then held at this temperature for 2.5 hours under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 14 hours, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0102] The synthesized artificial graphite was subjected to scanning electron microscopy (SEM) analysis. Images at 1000x and 3000x magnification are shown below. Figure 3 and Figure 4 As shown. By Figure 3 Can Figure 4 It can be seen that the morphology of artificial graphite is not good, and there are some broken particles and fine powder.

[0103] Comparative Example 2 This comparative example illustrates a method for preparing artificial graphite, comprising the following steps.

[0104] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 4%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 800℃ (calculated to be 900℃ according to the relationship Y=150X+300), the heating rate is 5℃ / min, inert gas (nitrogen, purity ≥ 99.9%, flow rate 3L / min) is used for protection, a slight positive pressure of 0.05MPa is maintained, the stirring speed inside the reactor is 30r / min, and the temperature is maintained at 800℃ for 1h to obtain the calcined material.

[0105] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 200℃, Dv50 2~5μm, residual carbon value 60%) in a batch mixer at a spindle speed of 50r / min for 40min. Then it was fed into a box furnace and graphitized at 3000℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.08MPa to achieve a graphitization degree of 94%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0106] (III) The first precursor and solid asphalt (4% of the mass of the first precursor, softening point of 200℃, Dv50 of 2~5μm, and residual carbon value of 60%) were mixed in a batch mixer at a spindle speed of 50r / min for 40min and then fed into a vertical reactor for post-granulation. The temperature was raised to 600℃ at a rate of 4℃ / min under a stirring speed of 25Hz and held for 90min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0107] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1150°C at a rate of 8°C / min. It is then held at this temperature for 2.5 hours under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 14 hours, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0108] Comparative Example 3 This comparative example illustrates a method for preparing artificial graphite, comprising the following steps.

[0109] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 2.2%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 630℃ according to the relationship Y=150X+300, the heating rate is 5℃ / min, inert gas (nitrogen, purity ≥ 99.9%, flow rate 3L / min) protection is provided, the pressure is slightly positive 0.05MPa, the stirring speed in the reactor is 30r / min, and the temperature is maintained at 630℃ for 2h to obtain the calcined material.

[0110] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 200℃, Dv50 2~5μm, residual carbon value 60%) in a batch mixer at a spindle speed of 50r / min for 40min. Then it was fed into a box furnace and graphitized at 3000℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.08MPa to achieve a graphitization degree of 94%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0111] (III) The first precursor and solid asphalt (5% of the mass of the first precursor, softening point of 150℃, Dv50 of 2~5μm, and residual carbon value of 50%) are mixed in a batch mixer at a spindle speed of 50r / min for 40min and then fed into a vertical reactor for post-granulation. The temperature is raised to 700℃ at a rate of 4℃ / min under a stirring speed of 10Hz and held for 240min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0112] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1150°C at a rate of 8°C / min. It is then held at this temperature for 2.5 hours under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 14 hours, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0113] Comparative Example 4 This comparative example illustrates a method for preparing artificial graphite, comprising the following steps.

[0114] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 2.2%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 630℃ according to the relationship Y=150X+300, the heating rate is 5℃ / min, inert gas (nitrogen, purity ≥ 99.9%, flow rate 3L / min) protection is provided, the pressure is slightly positive 0.05MPa, the stirring speed in the reactor is 30r / min, and the temperature is maintained at 630℃ for 2h to obtain the calcined material.

[0115] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 200℃, Dv50 2~5μm, residual carbon value 60%) in a batch mixer at a spindle speed of 50r / min for 40min. Then it was fed into a box furnace and graphitized at 3000℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.08MPa to achieve a graphitization degree of 94%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0116] (III) The first precursor and solid asphalt (5% of the mass of the first precursor, softening point of 150℃, Dv50 of 2~5μm, and residual carbon value of 50%) are mixed in a batch mixer at a spindle speed of 50r / min for 40min and then fed into a vertical reactor for post-granulation. The temperature is raised to 700℃ at a rate of 4℃ / min under a stirring speed of 10Hz and held for 30min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0117] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1150°C at a rate of 8°C / min. It is then held at this temperature for 2.5 hours under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 14 hours, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0118] Comparative Example 5 This comparative example illustrates a method for preparing artificial graphite, comprising the following steps.

[0119] (I) The calcined petroleum coke (feed particle size > 50 mm, sulfur content 3%, volatile matter 10%) is crushed into 10~50 mm pieces by a jaw crusher and then fed into a continuous reactor. The temperature is controlled at 750℃ according to the relationship Y=150X+300, the heating rate is 5℃ / min, the inert gas (nitrogen, purity ≥ 99.9%, flow rate 3L / min) is used for protection, the pressure is slightly positive 0.05MPa, the stirring speed in the reactor is 30r / min, and the temperature is maintained at 750℃ for 1h to obtain the calcined material.

[0120] (II) The calcined material is fed into a mechanical mill and a shaping machine to obtain shaped material. The particle size of the shaped material meets the following requirements: Dv01 > 2μm, Dv10 is 4~5μm, Dv50 is 8~11μm, Dv90 is 19~20μm, and Dv99 < 30μm. The shaped material was mixed with 0.5% asphalt (softening point 200℃, Dv50 2~5μm, residual carbon value 60%) in a batch mixer at a spindle speed of 50r / min for 40min. Then it was fed into a box furnace and graphitized at 3000℃ under inert gas (nitrogen, purity ≥99.9%) protection and atmospheric pressure to slightly positive pressure 0.08MPa to achieve a graphitization degree of 94%, resulting in a first precursor with 2.5μm≤Dv01, Dv10 4~5μm, Dv50 9~11μm, Dv90 19~20μm, and Dv99 <32μm.

[0121] (III) The first precursor and solid asphalt (4% of the mass of the first precursor, softening point of 200℃, Dv50 of 2~5μm, and residual carbon value of 60%) were mixed in a batch mixer at a spindle speed of 50r / min for 40min and then fed into a vertical reactor for post-granulation. The temperature was raised to 750℃ at a rate of 4℃ / min under a stirring speed of 25Hz and held for 90min to obtain a second precursor with Dv01>3.0μm, Dv10 of 7~9μm, Dv50 of 13~15μm, Dv90 of 24~28μm, and Dv99<38μm.

[0122] (IV) The second precursor is fed into a carbonization roller kiln and heated to 1150°C at a rate of 8°C / min. It is then held at this temperature for 2.5 hours under nitrogen protection (purity ≥99.5%). The total heat treatment time in the carbonization roller kiln is 14 hours, yielding high-temperature carbonized material. The high-temperature carbonized material is then broken up by rod milling, and finally premixed, sieved using a 250-mesh sieve, and demagnetized to obtain artificial graphite.

[0123] The tap density of the second precursor in Examples 1-7 and Comparative Examples 1-5 was tested, and its relationship with 2#Dv01 and 1#Dv01 is shown in Table 1. The indoor and electrochemical properties of the artificial graphite prepared in Examples 1-7 and Comparative Examples 1-5 were tested. The testing process is as follows, and the test results are shown in Table 2.

[0124] The specific surface area was measured using a specific surface area analyzer.

[0125] Particle size was measured using a Malvern MS2000 laser particle size analyzer.

[0126] Electrochemical performance testing procedure: The artificial graphite prepared in Examples 1-7 and Comparative Examples 1-5 was dispersed in a beaker containing N-methylpyrrolidone (NMP) solvent at a mass ratio of 7:2:1 with conductive carbon black (SP) and polyvinylidene fluoride (PVDF). The mixture was heated and stirred until fully dissolved, and then stirred for 12 hours to prepare a slurry with good flowability. After uniform mixing, the slurry was uniformly coated onto copper foil to form an electrode. Subsequently, the electrode sheet was dried under vacuum at 60°C for 12 hours to ensure complete evaporation of NMP. Finally, the electrode was rolled and cut into working electrodes with a diameter of 12 mm. The active material mass loading of each electrode was approximately 1.5 mg / cm³. 2 CR2025 coin cells (including positive and negative electrode shells, spring contacts, and gaskets) were assembled. The process was carried out in a glove box filled with inert argon gas, where both water and oxygen content were less than 0.1 ppm. The assembly sequence was: positive electrode shell, working electrode, electrolyte (1M LiPF6, DEC and EC volume ratio 3:2), glass fiber separator, lithium metal sheet, gasket, spring contact, and negative electrode shell. The cells were then packaged using a battery packaging machine. After packaging, they were placed in a 25°C constant temperature chamber for later use. The assembled cells were then tested using a LAND CT 3002A charge / discharge test cabinet to obtain their initial discharge capacity, initial coulombic efficiency, and 3C discharge capacity retention.

[0127] Table 1. Partial performance parameters of the second precursors in Examples 1-7 and Comparative Examples 1-5.

[0128] As shown in Table 1, as the ratio of 2#Dv01 / 1#Dv01 gradually increases, the fine powder content decreases, and the tap density of the second precursor increases accordingly. However, when the ratio of 2#Dv01 / 1#Dv01 exceeds a certain value, the tap density shows a decreasing trend. Taking all factors into consideration, a ratio of 2#Dv01 to 1#Dv01 of 1.5 to 1.8 is selected.

[0129] Table 2 Performance parameters of artificial graphite in Examples 1-7 and Comparative Examples 1-5

[0130] As shown in Table 2, the artificial graphite of Examples 1-7 has better physical and electrochemical properties. This indicates that the preparation method of the present invention determines the endpoint temperature in the heat treatment process by determining the sulfur content in the coke raw material, and then combines it with specific asphalt and particle size control in graphitization and granulation to repair the carbon structure of the desulfurized graphite, thus obtaining artificial graphite with better performance.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing artificial graphite, characterized in that, Including the following steps: (I) The coke raw material is crushed and subjected to a first heat treatment to obtain calcined material. The sulfur content of the coke raw material is X wt.%, and the final temperature of the first heat treatment is Y °C, satisfying the relationship Y=BX+k, with an error of ±10, where X is 1.5~3.0, B is a calculation coefficient with a value range of 50~200, and k is a calculation constant with a value range of 200~400; (II) The calcined material is shaped and graphitized to obtain a first precursor, wherein the Dv01 of the first precursor is 1#Dv01; (III) The first precursor and the first solid asphalt are mixed and granulated to obtain the second precursor. The softening point of the first solid asphalt is 150~250℃, and the final temperature of the granulation is not higher than 600℃. The Dv01 of the second precursor is 2#Dv01, and the ratio of 2#Dv01 to 1#Dv01 is 1.5~1.

8. (IV) The second precursor is carbonized and then broken up, sieved and demagnetized.

2. The method for preparing artificial graphite according to claim 1, characterized in that, Y is 500~900.

3. The method for preparing artificial graphite according to claim 1, characterized in that, The difference between 2#Dv01 and 1#Dv01 is 1~2μm.

4. The method for preparing artificial graphite according to claim 1, characterized in that, 1#Dv01 has a size of 2~4μm, and 2#Dv01 has a size of 3~6μm.

5. The method for preparing artificial graphite according to claim 1, characterized in that, Includes at least one of the following features (1) to (16): (1) The coke raw material is selected from at least one of needle coke, calcined needle coke, petroleum coke, calcined petroleum coke and isotropic coke; (2) The volatile matter content of the coke raw material is 5-15%; (3) The particle size of the calcined material after shaping is: Dv01 > 2μm, Dv10 is 4~6μm, Dv50 is 8~12μm, Dv90 is 19~23μm, and Dv99 is <30μm; (4) The heating rate of the first heat treatment is 1~10℃ / min, and the holding time of the first heat treatment is 1~4h; (5) An inert gas is introduced during the first heat treatment, and the flow rate of the inert gas is >1 L / min; (6) The graphitization temperature is 2900~3200℃, and the degree of graphitization after graphitization is 92~98%; (7) The particle size of the first precursor satisfies: Dv10 is 4~6μm, Dv50 is 9~14μm, Dv90 is 19~25μm, and Dv99 is <32μm; (8) The Dv50 of the first solid asphalt is 2~5μm; (9) The residual carbon value of the first solid asphalt is 50~70 wt.%; (10) The mass ratio of the first precursor to the first solid asphalt is 100:3~6; (11) The mixing time of the first precursor and the first solid asphalt is 0.5~2.0h; (12) The final temperature of the granulation is 400~600℃, the heating rate is 1~5℃ / min, the holding time at the final temperature is 1~6h, and the rotation speed is 10~30Hz. (13) The particle size of the second precursor satisfies: Dv10 is 7~9μm, Dv50 is 13~15μm, Dv90 is 24~28μm, and Dv99 is <35μm; (14) The final temperature of carbonization is 1000~1200℃, the heating rate is 1~10℃ / min, the holding time at the final temperature is 2~3h, and the total carbonization time is 12~14h. (15) An inert gas is introduced during the granulation process, and the flow rate of the inert gas is >1 L / min; (16) An inert gas is introduced during the carbonization process, and the flow rate of the inert gas is >1L / min.

6. The method for preparing artificial graphite according to claim 1, characterized in that, The shaped material is mixed with the second solid asphalt before graphitization, wherein the second solid asphalt accounts for 0.1 to 1.0% of the mass of the material.

7. The method for preparing artificial graphite according to claim 6, characterized in that, Includes at least one of the following features (a) to (c): (a) The Dv50 of the second solid asphalt is 2~6μm; (B) The softening point of the second solid asphalt is 200~300℃; (c) The residual carbon value of the second solid asphalt is 60~80 wt.%.

8. The artificial graphite prepared by the method for preparing artificial graphite according to any one of claims 1 to 7, characterized in that, Tap density ≥ 1.0 g / cm³ 3 It includes a graphite core and an amorphous carbon layer covering the graphite core.

9. The artificial graphite according to claim 8, characterized in that, Includes at least one of the following features (i) to (ix): (i) Dv10 is 6~8μm; (ii) Dv50 is 11~14μm; (iii) Dv90 is 22~25μm; (iv) Dv99 is 30~40μm; (v) The amorphous carbon layer accounts for 2-6% of the mass of the artificial graphite; (vi) Specific surface area is 1.4~1.6m² 2 / g; (vii) Initial discharge capacity ≥ 352 mAh / g; (viii) First Coulomb efficiency ≥ 92%. (ix) 3C discharge capacity retention rate ≥80%.

10. A secondary battery, comprising a positive electrode material, a separator, an electrolyte, and a negative electrode material, characterized in that, The negative electrode material includes the artificial graphite as described in claim 8 or 9.

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