Coke, negative electrode material and lithium-ion battery

Abstract

Provided in the present application are a coke, a negative electrode material, and a lithium ion battery. The coke provided in the present application has a hydrogen mass content of H%, an oxygen mass content of O%, and a high-temperature weight loss rate of V%, and satisfies 2≤V*O / H≤6, which helps to regulate the coking depth of the coke, so that the coke can reduce the difficulty of graphitization while maintaining good processing performance. The obtained negative electrode material has few grain boundary defects in the structure and high capacity, which help to improve the structural stability of the negative electrode material during high-rate charging and discharging, thereby improving the rate performance.

Description

Coke, anode materials and lithium-ion batteries Cross-references to related applications

[0001] This application claims priority to Chinese patent application filed on December 16, 2024, with application number 202411850889.2 and entitled "Coke and its preparation method, negative electrode material and lithium-ion battery". Technical Field

[0002] This invention relates to the field of negative electrode material technology, and more specifically, to a coke, a negative electrode material, and a lithium-ion battery. Background Technology

[0003] Artificial graphite is one of the mainstream anode materials for lithium-ion batteries. It is prepared from coke raw materials through a series of processes, including high-temperature graphitization. The coke raw materials used mainly include needle coke, petroleum coke, pitch coke, and isotropic coke. With the rapid development of the new energy industry, the performance requirements for graphite anode materials are becoming increasingly stringent, such as ultra-high capacity graphite anode materials, graphite anode materials that balance high capacity and high rate, and ultra-long cycle life graphite anode materials. In the field of power batteries, graphite anode materials that balance high capacity and high rate are currently the mainstream direction in the market, with rapidly growing demand, and coke raw materials are a key component in this process.

[0004] The layered structure of graphite dictates that lithium ions can only be inserted from the end faces of the graphite and then transport and diffuse within the graphite. Generally, the larger the graphite crystal size and the higher the degree of graphitization, the higher the capacity. However, larger graphite crystal sizes and higher degrees of graphitization also lead to greater graphite orientation, resulting in longer lithium ion transport paths, which is detrimental to rate performance. The microstructure of coke feedstock is fundamental to the formation of graphite crystals, and controlling the microstructure of coke largely determines the size and degree of graphitization of the graphite crystals. Furthermore, the stability of the graphite structure is also a crucial factor affecting rate performance. Improving the stability of the graphite structure requires high graphitization, low internal defect stress, minimal lithium ion diffusion resistance, and small volume changes in the graphite structure. High graphitization can be achieved by increasing the anisotropic structure content of the coke. For example, some researchers have prepared high-capacity needle coke with high streamline structure content by blending and modulating feedstock oils, achieving a specific capacity exceeding 355 mAh / g after graphitization. Low graphite crystal size and orientation can be achieved by reducing the anisotropic structure size of coke. Researchers have also developed an isotropic coke suitable for high-rate synthetic graphite, prepared by flash distillation of low-temperature coal tar to obtain the desired flash material, followed by coking in an inert atmosphere. The resulting synthetic graphite meets the 6C charging constant current ratio requirement of ≥80%, but has a low capacity of only 335–340 mAh / g. Other researchers have adjusted the microstructure of coke to achieve macroscopic isotropy for fast charging and achieved high capacity by doping with silicon oxide or nano-silicon, but the resulting anode material has an initial efficiency of ≤88%. However, in real-world applications, simply adjusting the size of the coke's microstructure has limited effect on balancing the capacity and rate performance of the anode material. Further research on coke raw materials is needed to develop graphite anode materials that can achieve both high capacity and high rate performance. Summary of the Invention

[0005] The main objective of this invention is to provide a coke, a negative electrode material, and a lithium-ion battery to solve the problem that coke in the prior art cannot be used to prepare a negative electrode material that achieves both high capacity and high rate of change.

[0006] To achieve the above objectives, according to one aspect of the present invention, a coke is provided, comprising carbon, hydrogen, oxygen, nitrogen and sulfur, wherein the mass content of hydrogen is H%, the mass content of oxygen is O%, the high-temperature weight loss rate of the coke is V%, and 2≤V*O / H≤6.

[0007] According to a second aspect of the present invention, a negative electrode material is provided, comprising graphite, which satisfies at least one of the following characteristics:

[0008] (1) The raw materials for the negative electrode material contain the coke provided in the first aspect above;

[0009] (2) The preparation method of the negative electrode material includes: carbonizing and graphitizing the coke provided in the first aspect in sequence to obtain the negative electrode material.

[0010] According to a third aspect of the invention, a lithium-ion battery is also provided, which includes the negative electrode material as provided in the second aspect above.

[0011] By applying the technical solution of this application, the mass content of hydrogen (H%) and the mass content of oxygen (O%) in this application satisfy 2≤V*O / H≤6 with the high-temperature weight loss rate of coke raw material (V%). This helps to control the coking depth of the coke, so that the coke can maintain good processing performance while reducing the difficulty of graphitization. This is conducive to obtaining a negative electrode material with fewer grain boundary defects and higher capacity, which in turn helps to improve the structural stability of the negative electrode material during high-rate charge and discharge processes and improve rate performance. Attached Figure Description

[0012] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0013] Figure 1 shows a schematic diagram of the polarization structure of the coke raw material of the negative electrode material provided in Embodiment 2 of the present invention. Detailed Implementation

[0014] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0015] As analyzed in the background section of this application, existing coke can increase its graphitization degree by increasing the content of anisotropic structures, reduce the size and orientation of graphite crystals by decreasing the size of anisotropic structures, and achieve high capacity by doping with silicon oxide or nano-silicon. However, in applications, simply controlling the microstructure and size of the coke is insufficient to develop graphite materials that balance high capacity and high rate of return. To address this issue, this application provides a coke and its preparation method, a graphite anode material, and a lithium-ion battery.

[0016] In a first typical embodiment of this application, a coke is provided, which includes carbon, hydrogen, oxygen, nitrogen and sulfur, wherein the mass content of hydrogen is H (%), the mass content of oxygen is O (%), the high-temperature weight loss rate of the coke is V (%), and 2≤V*O / H≤6.

[0017] In this application, the high-temperature weight loss rate of coke refers to the weight loss rate V (%) of the material after the coke is heated to 1200°C at a heating rate of 10°C / min under nitrogen or inert atmosphere and the volatile gases are discharged.

[0018] In this application, the mass content of hydrogen (H%), the mass content of oxygen (O%), and the high-temperature weight loss rate (V%) of the coke raw material satisfy 2≤V*O / H≤6. This helps to control the coking depth of the coke, so that the coke can maintain good processing performance while reducing the difficulty of graphitization. This results in fewer grain boundary defects and higher capacity in the obtained graphite anode material, which in turn helps to stabilize the structure of the graphite anode material during high-rate charge and discharge processes, thereby improving the rate performance.

[0019] When V*O / H < 2, it indicates that the coke has a low degree of graphitization, contains few functional groups, side chains, and side groups, and has a low oxygen content (%) or a low high-temperature weight loss rate (%). This results in less gas being generated during graphitization, which is not conducive to the orderly rearrangement of carbon layers during graphitization. Consequently, the resulting anode material has a low degree of graphitization, few lithium intercalation sites, and low capacity.

[0020] When V*O / H > 6, it indicates that the coke has a low degree of graphitization and contains many functional groups, side chains, and side groups, especially a high content of aliphatic chains with functional groups. The presence of these functional groups and side chains will hinder the graphitization process, prevent the growth and orderly arrangement of carbon layers, resulting in low graphitization degree and many defects in the prepared anode material. The reduction of lithium storage sites leads to low capacity and low rate performance after graphitization.

[0021] Typically, but not limitingly, in this application, V*O / H is a range of values ​​consisting of 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, or any two of these values, or other values ​​within that range.

[0022] In some embodiments, controlling the hydrogen content (H%) of the coke to be between 3.4% and 4.51% helps to regulate the coking depth of the coke raw material, thereby reducing the difficulty of graphitizing the coke raw material and obtaining graphite anode materials with high graphitization degree and high capacity.

[0023] In some embodiments, hydrogen exists primarily in the form of functional groups, side chain groups, etc., and its existence form can be one or more combinations of methyl (-CH3), methylene (-CH2), methine (-CH), carboxyl (-COOH), hydroxyl (-OH), etc., so as to generate more hydrogen-containing gas during the coking process, promote the orderly rearrangement of carbon layers during graphitization, improve the degree of graphitization, and thus improve the capacity and rate performance of the prepared graphite anode material.

[0024] In some embodiments, controlling the oxygen content (O%) of the coke to be between 0.8% and 1.8% is more conducive to adjusting the coking depth of the coke raw material, and thus more conducive to obtaining graphite anode materials with high graphitization degree and high capacity.

[0025] In some embodiments, oxygen may exist in one or more combinations of phenolic groups (CO), aromatic ether groups (Ar-CO), alkyl ethers (-COC-), carboxyl groups (C=O), etc., to facilitate the generation of more carbon-containing gases during the coking process, promote the orderly rearrangement of carbon layers during graphitization, improve the degree of graphitization, and thus improve the capacity and rate performance of the prepared graphite anode material.

[0026] In some embodiments, controlling the sulfur content S (%) to be ≤4.0% is beneficial for controlling the amount of SO2 volatilized during graphitization, thereby improving the orderliness of the formed graphite anode material. In particular, when S (%) is ≤2.5%, it is even more beneficial for improving the orderliness of the formed graphite anode material.

[0027] The sulfur content was tested using the Eltra CS-i carbon-sulfur analyzer from Germany.

[0028] In some embodiments, sulfur exists primarily in the forms of pyrite-type sulfur, thiophene-type sulfur, and sulfoxide-type sulfur. Based on the total mass of sulfur, the proportion of pyrite-type sulfur is ≤5%, the proportion of thiophene-type sulfur is 40%-80%, and the proportion of sulfoxide-type sulfur is 20%-60%. This facilitates the generation of more sulfur-containing gases during coking, promotes the orderly rearrangement of carbon layers during graphitization, increases the degree of graphitization, and thereby improves the capacity and rate performance of the prepared graphite anode material.

[0029] Sulfur-containing groups were tested using a Thermo Fisher K-Alpha X-ray photoelectron spectrometer, but other models of X-ray photoelectron spectrometers can also be used; no specific method is specified here.

[0030] In some embodiments, the nitrogen content (N%) of the coke is controlled to be ≤2.5% to control the volatilization of NO and NO2 during the graphitization process, thereby increasing the coking depth and making it more conducive to obtaining graphite anode materials with high graphitization degree. In particular, when N≤2.0%, it is more conducive to obtaining graphite anode materials with high capacity.

[0031] In some embodiments, nitrogen may exist in one or more of the following forms: pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen, in order to generate more nitrogen-containing gas during coking, promote the orderly rearrangement of carbon layers during graphitization, improve the degree of graphitization, and thus improve the capacity and rate performance of the prepared graphite anode material.

[0032] In some embodiments, the high-temperature weight loss rate V (%) is 7.5-11.5%. The volatile gases produced by the coke provided in this application at high temperature (1200°C) mainly include one or more of the following gases: SO2, H2S, NO, NO2, CO, CO2, H2O, hydrocarbons, etc.

[0033] Typical, but not limiting, the mass content of hydrogen in coke, H (%), is 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.51%, or any range of two values ​​or other values ​​within that range; the mass content of oxygen, O (%), is 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, or any range of two values ​​or other values ​​within that range; and the high-temperature weight loss rate, V (%), is 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, or any range of two values ​​or other values ​​within that range.

[0034] In this application, the mass content of hydrogen (H%), oxygen (O%), and nitrogen (N%) were all tested using an Eltra ONH-2000 oxygen-nitrogen-hydrogen analyzer from Germany.

[0035] Hydrogen-containing groups were tested using a WQF-530 Fourier transform infrared spectrometer, but other models of Fourier transform infrared spectrometers can also be used; no limitation is made here.

[0036] Oxygen-containing and nitrogen-containing groups were tested using a Thermo Fisher K-Alpha X-ray photoelectron spectrometer. Other models of X-ray photoelectron spectrometers may also be used, and no limitation is made here.

[0037] The high-temperature weight loss rate V (%) was tested using a Hitachi STA3000 synchronous thermogravimetric analyzer. The test conditions were heating to 1200℃ at 10℃ / min under nitrogen or inert atmosphere. After heating, the weight loss rate V (%) of the material was calculated.

[0038] In some embodiments, the coke also includes ash elements, which include one or more ash elements such as iron, nickel, aluminum, calcium, vanadium, cobalt, zinc, manganese, sodium, potassium, copper, chromium, magnesium, and silicon. The total mass content of ash is ≤0.6%, and preferably the content of each individual ash element is ≤200ppm.

[0039] The ash element content was measured using a PerkinElmer ICP 2100 inductively coupled plasma atomic emission spectrometer. Other models of inductively coupled plasma atomic emission spectrometers may also be used, and no limitation is made here.

[0040] In some embodiments, the microstructure of coke includes streamlined structure, lamellar structure, isotropic structure, uncoked structure, and mosaic structure.

[0041] In some specific embodiments, the volume percentage of the sheet-like structure is P (%), the volume percentage of the streamlined structure is M (%), 80% ≤ P + M ≤ 95%, and 1 ≤ M / P ≤ 2.

[0042] The streamlined structure of coke is more conducive to obtaining graphite structures with high graphitization and high order, which is beneficial to capacity. However, because lithium ions mainly enter the graphite interior from the end face during battery charging and discharging, excessive order leads to a long lithium ion transport distance. Lithium ions are prone to aggregation or lithium deposition at the end face, thus hindering lithium ion transport. Furthermore, excessive order can cause excessive graphite expansion, which is detrimental to the stability of the graphite structure. The order of sheet-like structures is lower than that of streamlined structures, and combining them with streamlined structures is more conducive to balancing the capacity and rate performance of graphite anode materials.

[0043] The microstructure of the aforementioned coke was tested using a Carl Zeiss Axio Scope A1 polarizing microscope. Quantitative analysis of the polarized structure was performed under a 20X objective lens. The polarizer was fixed on an automatic displacement platform with pre-set forward, backward, left, and right movement distances. The distances for both forward, backward, left, and right movements were 200 μm. During testing, the automatic displacement platform moved the polarizer in a pre-set sequence. The microstructure characteristics under the cursor were observed at each position. A total of 300 positions were analyzed to count the type and quantity of polarized microstructures and calculate the volumetric content of each microstructure. The definition of polarized microstructure was based on the industry standard YB / T 077-2017, "Determination of Optical Structure of Coke". A lamellar structure refers to a microstructure with a length and width of approximately ≥10 μm in the isochromatic region (i.e., anisotropic unit) under the objective lens, which alternately displays red, yellow, and green colors when the stage is rotated. The streamlined isochromatic regions (i.e., anisotropic units) under the microscope have a width of <10μm and a length of ≥10μm, resembling tissues flowing in one direction or arranged in parallel bundles. When the stage is rotated, red, yellow, and green colors appear alternately.

[0044] Typically, but not limitingly, in this application, P+M is a range of values ​​consisting of 80%, 82%, 85%, 88%, 90%, 92%, 95%, or any two of these values, or other values ​​within that range; M / P is a range of values ​​consisting of 1, 1.1, 1.2, 1.5, 1.6, 1.8, 2, or any two of these values, or other values ​​within that range.

[0045] In some specific embodiments, the volume percentage P (%) of the lamellar structure in the coke is 20%-50%, and the volume percentage M (%) of the streamlined structure is 30%-80%, which is more conducive to the preparation of graphite anode materials that take into account both high capacity and excellent rate performance. In particular, when the volume percentage P (%) of the lamellar structure is 30%-45% and the volume percentage M of the streamlined structure is 45%-70%, it is more conducive to the preparation of graphite anode materials with higher capacity and better rate performance.

[0046] Typical, but not limiting, the volume percentage P of lamellar structures in coke is 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any two of these values, or other values ​​within that range; the volume percentage M of streamlined structures is 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any two of these values, or other values ​​within that range.

[0047] In some specific embodiments, the volume percentage of isotropic structures in the coke microstructure is ≤10%, preferably ≤5%, in order to further improve the capacity and rate performance of the graphite anode material prepared from the coke.

[0048] In some specific embodiments, the volume percentage of uncoked structures in the coke microstructure is ≤5%, preferably ≤3%, to further improve the capacity and rate performance of the graphite anode material prepared from the coke.

[0049] In some specific embodiments, the volume of the embedded structure in the coke is ≤10%, preferably ≤5%, to further improve the capacity and rate performance of the graphite anode material prepared from the coke.

[0050] In some embodiments, the true density of the char is 1.36-1.43 g / cm³. 3 This contributes to the preparation of high-capacity graphite anode materials, especially when the true density of coke is 1.39-1.42 g / cm³. 3 At this time, it is more conducive to preparing highly graphitized and high-capacity graphite anode materials.

[0051] True density is the ratio of a substance's mass to its true volume under specified conditions. True density is an inherent physical property of an object; it reflects the density of the substance and is independent of the object's shape, size, and state.

[0052] The true density of the above-mentioned coke was tested using a 3H-2000TD true density meter.

[0053] Typical, but not limiting, true density of ker is 1.36 g / cm³. 31.37g / cm 3 1.38g / cm 3 1.39 g / cm 3 1.40 g / cm 3 1.41 g / cm 3 1.42g / cm 3 1.43 g / cm 3 Or a range of values ​​consisting of any two numerical values, or other values ​​within that range.

[0054] In some embodiments, the surface and interior of the foam are porous, and the shape of the pores includes any one or more combinations of irregular circles, ellipses, and elongated shapes.

[0055] In some embodiments, the fracture surface of the coke after being broken is sharp or irregular.

[0056] In some embodiments, the cross-section of the coke is covered with holes, and the cross-section surface of the coke will produce fluorescence when illuminated with an ultraviolet flashlight.

[0057] In a second typical embodiment of this application, a method for preparing the coke of the above-mentioned graphite anode material is also provided. The preparation method includes the following steps: Step S1, mixing graphene oxide and concentrated sulfuric acid for activation to obtain graphene oxide activated material; Step S2, nano-sizing the graphene oxide activated material to obtain graphene oxide nanomaterial; Step S3, mixing the graphene oxide nanomaterial, raw material oil A, and raw material oil B at 150-300℃ by ultrasonic stirring to obtain mixed oil; Step S4, coking the mixed oil to obtain coke raw material for the graphite anode material; wherein, raw material oil A includes heavy oil remaining after crude oil has been extracted into light oil products through distillation, and the heavy oil includes any one or a mixture of two or more of atmospheric residue, vacuum residue, and heavy asphalt; raw material oil B includes high aromatic content oil obtained by refining atmospheric and vacuum residue or heavy asphalt, and the high aromatic content oil includes any one or a mixture of two or more of deconsolidated oil slurry, cracked tar, thermal cracking residue, and catalytic oil slurry.

[0058] The method for preparing coke feedstock for graphite anode materials provided in this application involves uniformly mixing graphene oxide nanomaterials, feedstock oil A, and feedstock oil B through heating and ultrasonic stirring to obtain coking feedstock oil with moderate reactivity. During the coking reaction, highly active graphene oxide nanomaterials are used to promote the uniform and rapid growth of the mesophase, which helps to generate a good mesophase structure while reducing the formation of structures with excessively large size and high orientation. This allows for the control of the content and size of the structure, resulting in coke with moderate hydrogen mass content H (%), oxygen mass content O (%), and high-temperature weight loss rate V (%), where 2 ≤ V*O / H ≤ 6, thus meeting the requirements of high-capacity, high-rate graphite anode materials.

[0059] In some embodiments, in step S1 above, graphene oxide prepared by the Hummer method and concentrated sulfuric acid (purity ≥98%) are mixed at a mass ratio of 1:2-10 and activated at a heating temperature of 60-120°C for 1-5 hours to obtain activated graphene oxide material.

[0060] The mass ratio of graphene oxide to concentrated sulfuric acid can be 1:2, 1:4, 1:6, 1:8, 1:10, or any two of these values ​​within a range, or other values ​​within that range. This can be understood as the higher the amount of concentrated sulfuric acid added, the higher the activation level of the graphene oxide, the more oxygen-containing functional groups and defects are introduced, and the more active sites are created. Regulating the activation level of graphene oxide in conjunction with the subsequent properties of the feedstock and the coking reaction helps to obtain coking feedstock that meets the requirements of 80% ≤ P + M ≤ 95% and 1 ≤ M / P ≤ 2.

[0061] The activation temperature can be 60℃, 70℃, 80℃, 100℃, 110℃, 120℃, or any range of two values, or other values ​​within that range. It can be understood that the activation reaction intensifies with increasing temperature.

[0062] The activation time can be 1h, 2h, 3h, 4h, 5h, or any range of two values, or other values ​​within that range. This can be understood as the degree of activation of graphene oxide increasing with increasing activation time.

[0063] In some embodiments, in step S2 above, the activated graphene oxide material is nano-sized using a nano-mill to reduce its size to the nanoscale, thereby obtaining graphene oxide nanomaterials.

[0064] The particle size D50 of the aforementioned graphene oxide nanomaterial is preferably 100-800 nm to facilitate the preparation of graphite anode materials with uniform particle size. Specifically, the D50 of the graphene oxide nanomaterial can be 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, or any two of these values, or other values ​​within this range. This application does not impose any restrictions on this value.

[0065] In some embodiments, in step S3 above, the mass ratio of raw material oil A to raw material oil B is 95-50:5-50, specifically it can be 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40 or any two values ​​within a range or other values ​​within that range.

[0066] In some embodiments, in step S3 above, the total mass ratio of raw material oil A and raw material oil B to the mass ratio of graphene oxide nanomaterial is 100:1-3. Specifically, the amount of graphene oxide nanomaterial can be 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2 parts, or any two of these values ​​within a range, or other values ​​within that range.

[0067] The compositional distribution of the coking feedstock oil can be achieved either by mixing feedstock oil A and feedstock oil B in a certain proportion, or by adding aromatic compounds to the residue oil.

[0068] In some embodiments, in step S3 above, the ultrasonic stirring speed is 50-200 r / min, the ultrasonic stirring temperature is 150-300℃, the ultrasonic stirring time is 0.5-3 h, and the ultrasonic frequency during ultrasonic stirring is 10-40 kHz.

[0069] The ultrasonic stirring speed can be 50 r / min, 80 r / min, 100 r / min, 120 r / min, 150 r / min, 180 r / min, 200 r / min or any two of these values ​​or other values ​​within that range; the ultrasonic stirring temperature can be 150℃, 180℃, 200℃, 220℃, 250℃, 280℃, 300℃ or any two of these values ​​or other values ​​within that range; the ultrasonic stirring time can be 0.5h, 0.8h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h or any two of these values ​​or other values ​​within that range.

[0070] In some embodiments, the asphaltene content of feedstock oil A is ≤3% by mass, specifically it can be a range of 1%, 1.5%, 2%, 2.5%, 3%, or any two of these values, or other values ​​within that range.

[0071] In some embodiments, the mass content of gum in raw material oil A is 20%-50%, specifically it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any two values ​​within a range or other values ​​within that range.

[0072] In some embodiments, the aromatic content of the feedstock oil A is 20%-50% by mass, specifically 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any two of these values ​​or other values ​​within that range.

[0073] In some embodiments, the mass content of saturated fraction of feedstock oil A is 10%-40%, specifically it can be 10%, 15%, 20%, 25%, 30%, 35%, 40% or any two values ​​within a range or other values ​​within that range.

[0074] In some implementations, the density (at 20℃) of feedstock oil A is 1-1.05 g / cm³. 3 Specifically, it could be 1.01 g / cm³. 3 1.015g / cm 3 1.02g / cm 3 1.025g / cm 3 1.03 g / cm 3 1.035g / cm 3 1.04 g / cm 3 1.045g / cm 3 1.05g / cm 3 Or a range of values ​​consisting of any two numerical values, or other values ​​within that range.

[0075] In some embodiments, the sulfur content of feedstock oil A is 1.5%-2.3% by mass, specifically it can be 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3% or any two of these values ​​or other values ​​within that range.

[0076] In some embodiments, the asphaltene content of the feedstock oil B is ≤1.5% by mass, specifically it can be a range of 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, or any two of these values, or other values ​​within that range.

[0077] In some embodiments, the gum content of the feedstock oil B is ≤15%, specifically it can be 5%, 7%, 9%, 11%, 13%, 15%, or any two of these values ​​or other values ​​within that range.

[0078] In some embodiments, the aromatic content of the feedstock oil B is ≥70% by mass, specifically it can be 0%, 75%, 80%, 85%, 90%, 95% or any two of these values ​​or other values ​​within that range.

[0079] In some embodiments, the mass content of saturated fraction of feedstock oil B is ≤15%, specifically it can be 5%, 7%, 9%, 11%, 13%, 15%, or any two of these values ​​or other values ​​within that range.

[0080] In some embodiments, the sulfur content of feedstock oil B is 0.5%-1.5% by mass, specifically it can be 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5% or any two of these values ​​or other values ​​within that range.

[0081] In some embodiments, the density (at 20°C) of feedstock oil B is 1.08-1.2 g / cm³. 3 Specifically, it could be 1.08 g / cm³. 3 1.09 g / cm 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 Or a range of values ​​consisting of any two numerical values, or other values ​​within that range.

[0082] In some embodiments, in step S4 above, the coking reaction is carried out under inert gas protection at a pressure of 0.1-0.3 MPa, such as 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, or any two of these values ​​or other values ​​within that range.

[0083] In some embodiments, the entire coking process is divided into three stages. Specifically, step S4 includes: a first stage, controlling the heating rate at 5-10℃ / min to raise the mixed oil from room temperature to 260-300℃, and holding the temperature for 30-60 seconds; a second stage, controlling the heating rate at 1-3℃ / min to continue heating to 380-420℃, and holding the temperature for 10-60 seconds; and a third stage, controlling the heating rate at 3-7℃ / min to continue heating to 490-510℃ to carry out the coking reaction, holding the temperature for 1-24 hours, and then cooling to obtain coke raw material. By controlling the heating rate, holding time, and pressure in the three stages, the degree of coking of the coke is improved, thereby increasing the capacity and rate performance of the graphite anode material.

[0084] The heating rate in the first stage can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, or any two of these values ​​within a range, or other values ​​within that range.

[0085] The temperature in the first stage mentioned above can be 260℃, 270℃, 280℃, 290℃, 300℃, or any two of these values, or other values ​​within that range.

[0086] The isothermal time for the first stage can be 30s, 40s, 50s, 60s, or any range of two values, or other values ​​within that range.

[0087] The heating rate in the second stage can be 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, or any two of these values ​​within a range, or other values ​​within that range.

[0088] The heating rate in the third stage can be 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, or any two of these values ​​within a range, or other values ​​within that range.

[0089] The temperature for the coking reaction in the third stage mentioned above is 490℃, 493℃, 495℃, 498℃, 500℃, 502℃, 505℃, 510℃, or any two of these values, or other values ​​within that range; the holding time for the coking reaction is 1h, 2h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 24h, or any two of these values, or other values ​​within that range.

[0090] In a third typical embodiment of this application, a negative electrode material is provided, the negative electrode material comprising graphite, the raw material of which contains the coke provided in the first typical embodiment described above.

[0091] Specifically, the method for preparing the negative electrode material includes: sequentially carbonizing and graphitizing the coke provided in the first typical embodiment to obtain the negative electrode material.

[0092] The negative electrode material provided in this application uses coke with a moderate mass content of hydrogen (H) and oxygen (O) and a high-temperature weight loss rate (V) as raw material, and 2≤V*O / H≤6, thus possessing the characteristics of fewer crystal defects, high capacity, high stability and high rate capability, and has a broader prospect in lithium-ion batteries.

[0093] In some embodiments, the carbonization temperature is 1000-1500°C and the carbonization time is 10-15 hours to further improve the carbonization efficiency of the coke.

[0094] In some embodiments, the graphitization temperature is 2800-3200℃ and the graphitization time is 2-5h, so as to further improve the preparation efficiency of graphite anode materials.

[0095] Specifically, the carbonization temperature is 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, or any two of these values, or other values ​​within that range; the carbonization time is 10h, 11h, 12h, 13h, 15h, or any two of these values, or other values ​​within that range; the graphitization temperature is 2800℃, 2900℃, 3000℃, 3100℃, 3200℃, or any two of these values, or other values ​​within that range; the graphitization time is 2h, 3h, 4h, 5h, or any two of these values, or other values ​​within that range.

[0096] In the fourth typical embodiment of this application, a lithium-ion battery is provided, which includes the negative electrode material provided in the third typical embodiment above, thereby possessing high capacity and excellent rate performance.

[0097] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0098] It should be noted that in the following examples and comparative examples, "%" refers to "wt%".

[0099] Example 1

[0100] This embodiment provides a method for preparing coke, including the following steps:

[0101] (1) Graphene oxide prepared by the Hummer method and concentrated sulfuric acid (purity ≥98%) were added together in a round-bottom flask at a mass ratio of 1:3. The round-bottom flask was then placed in a heating reactor at 80°C for secondary deep activation for 3 hours to obtain activated graphene oxide material.

[0102] (2) The graphene oxide activated material was nano-sized by using an ultra-nano milling machine to reduce the size to D50 of 500±50nm, thus obtaining graphene oxide nanomaterials.

[0103] (3) Graphene oxide nanomaterials and raw material oils A and B were added to an ultrasonic stirrer at a mass ratio of 1:80:20. The mixture was ultrasonically stirred at 230℃, a stirring speed of 100 r / min, and an ultrasonic frequency of 20 kHz for 1 hour to obtain a mixed oil. The density of raw material oil A was 1.01 g / cm³. 3 The sulfur content is 1.8%, the asphaltene content is 2%, the resin content is 35%, the aromatic content is 30%, and the saturated content is 33%; the density of feedstock oil B is 1.1 g / cm³. 3It contains 1.0% sulfur, 1% asphaltene, 6% resin, 85% aromatics, and 8% saturated compounds.

[0104] (4) The mixed oil is added to a reaction vessel protected by nitrogen for coking reaction. The pressure inside the reaction vessel is controlled at 0.2 MPa. The entire coking process is carried out in three stages. In the first stage, the temperature of the mixed oil is raised from room temperature to 280°C by controlling the heating rate of 5°C / min and held at the temperature for 45s. In the second stage, the temperature is raised to 400°C by controlling the heating rate of 2°C / min and held at the temperature for 30s. In the third stage, the temperature is raised to 498°C by controlling the heating rate of 5°C / min and carried out coking reaction for 12 hours. After the coking reaction is completed, the coke is obtained by cooling.

[0105] Example 2

[0106] This embodiment provides a coke whose preparation method differs from that of Embodiment 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed in a mass ratio of 1:5, the reaction temperature is 90℃, and the reaction time is 4h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 1.5:70:30; in step (4), the final coking reaction temperature in the third stage is increased to 500℃, and the reaction duration is increased to 16h.

[0107] Example 3

[0108] This embodiment provides a coke whose preparation method differs from that of Embodiment 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed in a mass ratio of 1:5, the reaction temperature is 90℃, and the reaction time is 4h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 1.5:60:40; in step (4), the final coking reaction temperature in the third stage is increased to 500℃, and the reaction duration is increased to 16h.

[0109] Example 4

[0110] This embodiment provides a coke whose preparation method differs from that of Embodiment 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed in a mass ratio of 1:5, the reaction temperature is 90℃, and the reaction time is 4h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 1.5:65:35; in step (4), the final coking reaction temperature in the third stage is increased to 500℃, and the reaction duration is increased to 20h.

[0111] Example 5

[0112] This embodiment provides a coke whose preparation method differs from that of Embodiment 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed at a mass ratio of 1:10, the reaction temperature is 100℃, and the reaction time is 5h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 1.5:70:30; in step (4), the final coking reaction temperature in the third stage is increased to 500℃, and the reaction duration is increased to 20h.

[0113] Example 6

[0114] This embodiment provides a coke whose preparation method differs from that of Embodiment 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed at a mass ratio of 1:10, the reaction temperature is 100℃, and the reaction time is 5h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 1.5:70:30; in step (4), the final coking reaction temperature in the third stage is increased to 490℃, and the reaction duration is increased to 20h.

[0115] Example 7

[0116] This embodiment provides a coke whose preparation method differs from that of Embodiment 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed at a mass ratio of 1:10, the reaction temperature is 100℃, and the reaction time is 5h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 2:70:30; in step (4), the final coking reaction temperature in the third stage is increased to 490℃, and the reaction duration is increased to 20h.

[0117] Example 8

[0118] This embodiment provides a coke whose preparation method differs from that of Embodiment 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed at a mass ratio of 1:10, the reaction temperature is 100℃, and the reaction time is 5h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 2:70:30; in step (4), the final coking reaction temperature in the third stage is increased to 502℃, and the reaction duration is increased to 20h.

[0119] Example 9

[0120] This embodiment provides a coke whose preparation method differs from that of Embodiment 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed at a mass ratio of 1:10, the reaction temperature is 110℃, and the reaction time is 5h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 2:65:35; in step (4), the final coking reaction temperature in the third stage is increased to 500℃, and the reaction duration is increased to 20h.

[0121] Example 10

[0122] This embodiment provides a coke whose preparation method differs from that of Example 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed in a mass ratio of 1:8, the reaction temperature is 110℃, and the reaction time is 5h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 2:70:30; in step (4), the final coking reaction temperature in the third stage is increased to 500℃, and the reaction duration is increased to 16h.

[0123] Example 11

[0124] This embodiment provides a coke whose preparation method differs from that of Embodiment 1: in step (1), graphene oxide and concentrated sulfuric acid (purity ≥98%) are mixed in a mass ratio of 1:8, the reaction temperature is 110℃, and the reaction time is 5h; in step (3), the mass ratio of graphene oxide nanomaterials to raw material oil A and raw material oil B is 2:60:40; in step (4), the final coking reaction temperature in the third stage is increased to 505℃, and the reaction duration is increased to 14h.

[0125] Example 12

[0126] This embodiment provides a coke, the preparation method of which differs from that of Embodiment 1 in that: in step (3), the mass ratio of graphene oxide nanomaterial, raw material oil A and raw material oil B is 3:60:40.

[0127] Example 13

[0128] This embodiment provides a coke, the preparation method of which differs from that of Embodiment 1: in step (3), the mass ratio of graphene oxide nanomaterial, raw material oil A and raw material oil B is 1.5:95:5.

[0129] Example 14

[0130] This embodiment provides a coke, the preparation method of which differs from that of Embodiment 1: in step (3), the mass ratio of graphene oxide nanomaterial, raw material oil A and raw material oil B is 1.5:50:50.

[0131] Example 15

[0132] This embodiment provides a coke, the preparation method of which differs from that of Embodiment 1: In step (4), the pressure inside the reactor is controlled to be 0.1 MPa. In the first stage, the heating rate is controlled to be 7℃ / min to raise the mixed oil from room temperature to 260℃ and hold the temperature for 60s. In the second stage, the heating rate is controlled to be 3℃ / min to continue raising the temperature to 420℃ and hold the temperature for 10s. In the third stage, the heating rate is controlled to be 7℃ / min to continue raising the temperature to 500℃ for coking reaction, the duration of which is 12h. After the coking reaction is completed, the coke is obtained by cooling and extruding the coke raw material.

[0133] Example 16

[0134] This embodiment provides a coke, the preparation method of which differs from that of Embodiment 1: In step (4), the pressure inside the reactor is controlled to be 0.3 MPa. In the first stage, the heating rate is controlled to be 3℃ / min to raise the mixed oil from room temperature to 300℃ and hold the temperature for 30s. In the second stage, the heating rate is controlled to be 1℃ / min to continue raising the temperature to 380℃ and hold the temperature for 60s. In the third stage, the heating rate is controlled to be 3℃ / min to continue raising the temperature to 500℃ for coking reaction, the duration is 1h. After the coking reaction is completed, the coke is obtained by cooling and coke discharge.

[0135] Comparative Example 1

[0136] This comparative example provides a coke, the preparation method of which differs from that of Example 1 in that the mass ratio of graphene oxide nanomaterial, raw material oil A and raw material oil B in step (3) is 0.5:60:40.

[0137] Comparative Example 2

[0138] This comparative example provides a coke whose preparation method differs from that of Example 1 in that the mass ratio of graphene oxide nanomaterial, raw material oil A, and raw material oil B in step (3) is 5:60:40.

[0139] Comparative Example 3

[0140] This comparative example provides a coke, the preparation method of which differs from that of Example 1 in that step (4) controls the pressure inside the reactor to be 0.05 MPa.

[0141] Comparative Example 4

[0142] This comparative example provides a coke whose preparation method differs from that of Example 1. In step (4), the coking process is carried out in two stages. In the first stage, the heating rate is controlled at 5°C / min to raise the mixed oil from room temperature to 280°C and hold the temperature for 45s. In the second stage, the heating rate is controlled at 2°C / min to continue raising the temperature to 498°C for coking reaction, which lasts for 12h. After the coking reaction is completed, the coke is obtained by cooling and coking.

[0143] Comparative Example 5

[0144] This comparative example provides a coke, the preparation method of which differs from Example 1 in that the coking process in step (4) is carried out in two stages. In the first stage, the heating rate is controlled at 2℃ / min to raise the mixed oil from room temperature to 400℃ and hold the temperature for 40s. In the second stage, the heating rate is controlled at 5℃ / min to continue raising the temperature to 498℃ for coking reaction, and the duration is 12h. After the coking reaction is completed, the coke is obtained by cooling and coking.

[0145] Comparative Example 6

[0146] This comparative example provides a coke, the preparation method of which differs from that of Example 1 in that pure raw material oil B is used in step (3), and the final coking reaction temperature in the third stage of step (4) is increased to 495°C to prepare the coke raw material.

[0147] Comparative Example 7

[0148] This comparative example provides a coke, the preparation method of which differs from that of Example 1. In step (3), pure raw material oil A is used, and in step (4), the final coking reaction temperature in the third stage is increased to 505°C to prepare the coke raw material.

[0149] Comparative Example 8

[0150] This comparative example provides a coke, the preparation method of which differs from that of Example 1. The coking process in step (4) is as follows: the mixed oil is heated from room temperature to 500°C by controlling the heating rate of 5°C / min and kept at a constant temperature for 12 hours.

[0151] The hydrogen content, oxygen content, volatile matter, lamellar structure content, streamline structure content, and true density of the coke provided in the above embodiments and comparative examples were tested, and the results are shown in Table 1 below.

[0152] The coke provided in the above embodiments and comparative examples was pulverized, and the median particle size D50 of the pulverized material was 11±1μm. The pulverized material was carbonized at 1150℃ for 12h, and then graphitized at 3000℃ for 3h. The resulting material was dispersed and sieved to finally obtain a graphite anode material with a D50 of 11±1μm.

[0153] The average particle size D50, specific capacity, first efficiency, and rate capability of the above-mentioned graphite anode materials were tested, and the results are shown in Table 2 below.

[0154] Test method:

[0155] (1) Test methods for the mass content of hydrogen (H%), oxygen (O%), and nitrogen (N%) in char:

[0156] The tests were conducted using an Eltra ONH-2000 oxygen, nitrogen, and hydrogen analyzer from Germany. Coke samples were coarsely and finely ground, then passed through a 325-mesh sieve. The sieved material was encapsulated in a nickel capsule and placed in the sample chamber of the analyzer. Gas was then introduced for testing. High-purity nitrogen was used for hydrogen content testing, while high-purity helium was used for oxygen and nitrogen content testing. Ordinary nitrogen was used as the driving gas. The pressure of high-purity nitrogen and high-purity helium was 0.2–0.4 MPa, and the pressure of ordinary nitrogen was 0.4–0.6 MPa.

[0157] (2) Test method for sulfur content (S%) in coke:

[0158] The carbon-sulfur analyzer was Eltra CS-i from Germany. The coke sample was coarsely and finely ground, then passed through a 325-mesh sieve and placed in a small crucible specifically designed for the equipment. A tungsten-tin-iron multi-element flux was added, and the analysis was conducted under high-purity oxygen conditions.

[0159] (3) Test method for total ash element content in coke:

[0160] The tests were performed using a PerkinElmer ICP 2100 inductively coupled plasma atomic emission spectrometer. The coke samples were coarsely and finely ground, then passed through a 325-mesh sieve. The sieved material was dissolved and diluted with aqua regia before being placed in the instrument for testing.

[0161] (4) Test method for high-temperature weight loss rate V (%) of coke:

[0162] The test was conducted using a Hitachi STA3000 simultaneous thermogravimetric analyzer. The test conditions were: heating to 1200°C at a rate of 10°C / min under nitrogen or inert atmosphere. After heating, the weight loss rate V (%) of the material was calculated.

[0163] (5) Test methods for determining the volume percentage of lamellar structures and streamlined structures in the microstructure of char:

[0164] The microstructure of the aforementioned coke was tested using a Carl Zeiss Axio Scope A1 polarizing microscope. Quantitative analysis of the polarizing structure was performed under a 20X objective lens. During testing, the polarizer was moved sequentially, and the types and quantities of polarizing microstructures in 300 randomly selected regions were analyzed to calculate the volume percentage of lamellar and streamlined structures. Following the YB / T 077-2017 standard for the determination of optical microstructure of coke, powder coke was used for testing. If lamellar coke was used, it was broken down and powder coke meeting the standard requirements was selected. Lamellar structures refer to structures with isochromatic regions (i.e., anisotropic units) under the objective lens having a length and width of approximately ≥10 μm, exhibiting alternating red, yellow, and green colors when the stage is rotated. Streamlined structures have isochromatic regions (i.e., anisotropic units) with a width <10 μm and a length ≥10 μm, appearing as if flowing in one direction or arranged in parallel bundles, exhibiting alternating red, yellow, and green colors when the stage is rotated, and include fibrous and streamlined structures. When performing quantitative analysis, each image will have a "+" scale in the center. Based on the definition of the structure, determine the type of the structure below the "+" scale. Move the position of the polarizer in sequence to determine and count the structure, and finally calculate the proportion of sheet-like structures and streamlined structures.

[0165] (6) Method for testing the true density of joules:

[0166] The true density was tested using a 3H-2000TD true density meter. The coke sample was crushed, finely ground, and sieved. The sample was taken from a 325-mesh sieve for testing. The test gas was helium.

[0167] (7) Test method for median particle size D50 of graphite anode materials:

[0168] The particle size distribution range of the graphite anode material was tested using a Malvern 3000 laser particle size analyzer, and the particle size was the cumulative volume distribution.

[0169] (8) Test method for the first-week coulombic efficiency of lithium-ion coin cell half-cell capacity:

[0170] The graphite anode material, carboxymethyl cellulose (CMC), conductive carbon black (SP), and styrene-butadiene rubber (SBR) prepared in the examples and comparative examples were mixed uniformly at a mass ratio of 95:1.5:1.5:2. The resulting slurry was prepared into a honey paste, uniformly coated on copper foil, and vacuum dried at 130°C to obtain the electrode sheet. The electrode sheet, lithium sheet, electrolyte (1 mol / L LiPF6EC:EMC:DMC = 1:1:1), and Celgard 2400 separator were assembled into a 2016-type coin cell, and the first-week coulombic efficiency was tested. The charge / discharge regime is as follows: ① Discharge at 0.1C to 0.01V, maintain constant voltage for 5 hours; charge at 0.1C to 1.5V; ② Discharge at 0.2C to 0.01V, maintain constant voltage at 0.01C; charge at 0.2C to 1.5V; ③ Discharge at 0.2C to 0.01V, maintain constant voltage at 0.01C; charge at 2C to 1.5V, then charge at 0.2C to 1.5V; ④ Discharge at 0.2C to 0.01V, maintain constant voltage at 0.01C; charge at 0.2C to 1.5V; ⑤ Discharge at 1C to 0.01V, maintain constant voltage at 0.01C; charge at 0.2C to 1.5V; ⑥ Discharge at 2C to 0.01V.

[0171] (9) Test method for rate performance of lithium-ion button half-cells:

[0172] The graphite anode materials prepared in each embodiment and comparative example were used as active materials. They were mixed in a mass ratio of active material: conductive carbon black: CMC: SBR = 95.3:1.5:1.4:1.8, and coated onto copper foil using deionized water as the solvent. The coating surface density was 6.5 ± 0.1 mg / cm². After vacuum drying at 90°C, the electrode sheet was obtained and rolled to a compaction density of 1.50 ± 0.02 g / cc. The electrode sheet, lithium foil, electrolyte (1 mol / L LiPF6, EC:EMC:DMC = 1:1:1), and Celgard 2400 separator were assembled into a 2016-type coin cell. The coin cell was subjected to rate performance testing at 25 ± 2°C, and the charge / discharge specific capacity and coulombic efficiency at 0.1C, 0.2C, 1C, and 2C were obtained. Rate testing conditions: ① Discharge to 0.01V at 0.1C, maintain constant voltage to 0.01C, then charge to 1.5V at 0.1C; ② Discharge to 0.01V at 0.2C, maintain constant voltage to 0.01C, then charge to 1.5V at 0.2C; ③ Discharge to 0.01V at 1C, maintain constant voltage to 0.01C, then charge to 1.5V at 0.2C; ④ Discharge to 0.01V at 2C, maintain constant voltage to 0.01C, then charge to 1.5V at 0.2C. The 2C / 0.2C discharge capacity retention rate can be calculated by dividing the 2C discharge capacity by the 0.2C discharge capacity.

[0173] The test results are shown in Tables 1 and 2.

[0174] Table 1. Test results of coke feedstocks prepared in each embodiment and comparative example.

[0175] Table 2. Test results of the anode materials prepared in each embodiment and comparative example.

[0176] Figure 1 is a microscopic photograph of the internal structure of the foam provided in Example 2. As can be seen from Figure 1, the foam provided in Example 2 has a lamellar structure and a streamlined structure, and the two structures account for ≥80% of the tissue structure.

[0177] As can be seen from the data in Examples 1-4, the parameters for controlling the hydrogen content, oxygen content, and high-temperature weight loss rate V of the coke raw material in this application are 2≤V*O / H≤6, maintaining a suitable degree of coking, reducing the content of impurity elements, and facilitating graphitization. In particular, Example 2, the lithium battery prepared from the negative electrode material obtained therein has a capacity of 355.5 mAh / g and a 2C / 0.2C capacity retention rate of 37.7%, which also maintains a high level, and is superior in terms of capacity and rate performance.

[0178] Compared to Example 1, Examples 5-11 improved the activation degree of graphene oxide by adjusting the activation reaction temperature, reaction time, and the proportion of concentrated sulfuric acid. The degree of graphene oxide reaction was relatively higher than in Example 1. Simultaneously, by adjusting the raw material ratio and coking reaction conditions, the prepared coke satisfied 2≤V*O / H≤6, and the graphitized anode material still exhibited good capacity and rate performance. However, the capacity and rate performance of Examples 5-11 were lower than in Example 1. This is because the increased activation degree of graphene oxide and the increase in functional groups led to enhanced coke activity, resulting in more cross-linked or heterostructured structures and increased instability of the coking reaction. This caused the 2≤V*O / H≤6 value to deviate from the central value, thus reducing the capacity and rate performance of the anode material formed after graphitization.

[0179] Compared with Example 1, Examples 15-16 show that although the hydrogen content, oxygen content, and high-temperature weight loss rate V of the coke have increased, they still meet the condition 2≤V*O / H≤6. However, due to the deterioration of the structure, the capacity and rate of the resulting negative electrode material have decreased.

[0180] Based on examples 1-16, when the obtained coke satisfies 2≤V*O / H≤6, the lithium battery prepared from the negative electrode material formed by it has a capacity of 347-356.9mAh / g and a rate of 29.1-37.7, thus achieving excellent capacity and rate performance.

[0181] Compared with Comparative Examples 1 and 2, the amount of graphene oxide added in Comparative Example 1 was too low, while the amount of graphene oxide added in Comparative Example 2 was too high. As shown in Table 2, the amount of graphene oxide added too low will result in V*O / H≥6, while the amount added too high will result in V*O / H≤2. This is because when the amount of graphene oxide added is too low, the coking reaction proceeds slowly, resulting in incomplete reaction and too much residual organic components. When the amount of graphene oxide added is too high, the coking reaction is intensified, especially the non-uniformity of the coking reaction, which leads to serious structural deterioration, thus exhibiting poor capacity and rate performance.

[0182] Compared with Comparative Example 3, Comparative Example 3 had a lower pressure inside the reactor, which led to faster oil and gas removal, but the coking time was insufficient, resulting in a higher hydrogen content and V*O / H≤2, thus exhibiting poor capacity and rate performance.

[0183] Compared with Comparative Examples 4-5, Comparative Examples 4 and 5 used a two-stage heating method. In Comparative Example 4, the heating time was shortened, resulting in insufficient heating of the feed oil and a low degree of coking (V*O / H≥6). In contrast, Comparative Example 5 had an excessively high heating temperature in the first stage, leading to localized coking and uneven heating of the feed oil. This resulted in an excessively high degree of localized coking (V*O / H≤2) and affected the growth of lamellar and streamlined structures in the microstructure, resulting in poor capacity performance of the coked anode material.

[0184] In Comparative Example 6, the high aromatic content of feedstock oil B is conducive to the formation and fusion of the mesophase, ultimately resulting in more and larger streamlined structures with a high degree of structural order. However, due to the lack of use with feedstock oil A, the low coking temperature resulted in V*O / H = 6.55 > 6. A larger V*O / H value indicates a lower degree of coking in the coke, with higher internal O and hydrogen content. High O and H content indicates a higher content of functional groups, side chains, and side groups within the coke feedstock, especially a high content of aliphatic chains with functional groups. The presence of these functional group side chains hinders the graphitization process, impeding the growth and orderly arrangement of carbon layers. This results in a low degree of graphitization, more defects, and fewer lithium storage sites in the coke feedstock of Comparative Example 6, leading to a low capacity after graphitization. However, due to the high content of streamlined structures and fewer lithium-ion insertion pathways, the beneficial effects of low graphitization and high defect content on rate performance are weakened, resulting in poor rate performance of the anode material formed after graphitization.

[0185] In Comparative Example 7, feedstock A contains high levels of asphaltenes and gums, which are conducive to the formation of mosaic and small-sized streamlined structures, thus promoting the formation of large mesophase structures. However, it also exhibits low aromatic content, high coking temperature, and vigorous reaction. Furthermore, due to the lack of coordination with feedstock B, the resulting large-sized streamlined structures are few, while small lamellar, mosaic, and isotropic structures are abundant, with an S / P ratio of 0.9, leading to low capacity after graphitization. Additionally, V*O / H = 1.362, indicating excessively low O and H content, which is detrimental to the orderly rearrangement of carbon layers during graphitization, resulting in low graphitization degree, few lithium intercalation sites, and low capacity.

[0186] Compared with Comparative Example 8, Example 1 uses a one-stage heating method, which directly heats the coking temperature, resulting in uneven coking and low coking uniformity. The resulting coke has a V*O / H ≥ 6, leading to poor capacity and rate performance.

[0187] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A type of coke, characterized in that, The coke comprises carbon, hydrogen, oxygen, nitrogen, and sulfur, wherein the mass content of hydrogen is H%, the mass content of oxygen is 0%, the high-temperature weight loss rate of the coke is V%, and 2≤V*O / H≤6.

2. The coke according to claim 1, characterized in that, The focal point satisfies: 2≤V*O / H≤5; or 3≤V*O / H≤6; or, The value of V*O / H is a range of 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, or any two of these values.

3. The coke according to claim 1, characterized in that, The focal point satisfies at least one of the following characteristics: (1) The mass content of hydrogen element H% is 3.4%-4.51%; (2) The hydrogen element exists in at least one of the following forms: methyl, methylene, methine, carboxyl, and hydroxyl. (3) The mass content of oxygen element (O%) is 0.8%-1.8%; (4) The oxygen element exists in at least one of the following forms: phenolic group, aromatic ether group, alkyl ether group, and carbonyl group.

4. The coke according to claim 3, characterized in that, The focal point satisfies: 3.4% ≤ H% ≤ 4.0%; or 3.8% ≤ H% ≤ 4.51%; or, The S4 value is a range of 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.51%, or any two values.

5. The coke according to claim 3, characterized in that, The focal point satisfies: 0.8％≤O％≤1.5％； or 1.0% ≤ 0% ≤ 1.8%; or, The S4 value is a range of 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, or any two of these values.

6. The coke according to claim 1, characterized in that, The focal point satisfies at least one of the following characteristics: (1) The mass content of sulfur element is S%, S%≤4.0%; (2) The mass content of sulfur element is S%, S%≤2.5%; (3) The sulfur element exists in the form of pyrite sulfur, thiophene sulfur and sulfoxide sulfur; wherein, based on the total mass of sulfur element, the mass percentage of pyrite sulfur is ≤5%, the mass percentage of thiophene sulfur is 40%-80%, and the mass percentage of sulfoxide sulfur is 20%-60%.

7. The coke according to claim 1, characterized in that, The focal point satisfies at least one of the following characteristics: (1) The mass content of nitrogen element is N%, N% ≤ 2.5%; (2) The mass content of nitrogen element is N%, N% ≤ 2.0%; (3) The nitrogen element exists in at least one of pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen.

8. The coke according to claim 1, characterized in that, The focal point satisfies at least one of the following characteristics: (1) The high-temperature weight loss rate V% is 7.5%-11.5%; (2) The volatile gases produced by the char at 1200°C include at least one of SO2, H2S, NO, NO2, CO, CO2, H2O, and hydrocarbons; (3) The coke also includes ash elements, which include at least one of iron, nickel, aluminum, calcium, vanadium, cobalt, zinc, manganese, sodium, potassium, copper, chromium, magnesium, and silicon. (4) The coke also includes ash elements, which include at least one of iron, nickel, aluminum, calcium, vanadium, cobalt, zinc, manganese, sodium, potassium, copper, chromium, magnesium and silicon; and the content of each of the ash elements is ≤200ppm, and the total mass content of the ash elements is ≤0.6%.

9. The coke according to claim 8, characterized in that, The focal point satisfies: 7.5% ≤ V% ≤ 10.0%; or 9.0% ≤ V% ≤ 11.5%; or, V% is a range of values, including 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, or any two of these values.

10. The coke according to any one of claims 1 to 9, characterized in that, The microstructure of the coke includes at least one of the following: isotropic structure, uncoked structure, mosaic structure, streamlined structure, and lamellar structure, and the microstructure of the coke satisfies at least one of the following characteristics: (1) The volume percentage of the sheet-like structure is P%, and the volume percentage of the streamlined structure is M%, wherein 80%≤P+M≤95%, and 1≤M / P≤2; (2) The volume percentage of the sheet-like structure is P%, and P% is 20%-50%; (3) The volume percentage of the sheet-like structure is P%, and P% is 30%-40%; (4) The volume percentage of the streamlined structure is M%, and M% is 30%-80%; (5) The volume percentage of the streamlined structure is M%, and M% is 45%-70%; (6) The volume percentage of the sheet-like structure is P%, and the volume percentage of the streamlined structure is M%, where P+M is a range of 80%, 82%, 85%, 88%, 90%, 92%, 95% or any two of these values, and M / P is a range of 1, 1.1, 1.2, 1.5, 1.6, 1.8, 2 or any two of these values.

11. The coke according to any one of claims 1 to 9, characterized in that, The microstructure of the coke includes at least one of the following: isotropic structure, uncoked structure, mosaic structure, streamlined structure, and lamellar structure, and the microstructure of the coke satisfies at least one of the following characteristics: (1) The volume percentage of the isotropic structure is ≤10%; (2) The volume percentage of the isotropic structure is ≤5%; (3) The volume percentage of the uncoked structure is ≤5%; (4) The volume percentage of the uncoked structure is ≤3%; (5) The volume ratio of the inlay structure is ≤10%; (6) The volume ratio of the inlay structure is ≤5%.

12. The coke according to any one of claims 1 to 9, characterized in that, The focal point satisfies at least one of the following characteristics: (1) The true density of the char is 1.36 g / cm³. 3 -1.43g / cm 3 ; (2) The true density of the char is 1.39 g / cm³. 3 -1.42g / cm 3 .

13. The coke according to any one of claims 1 to 9, characterized in that, The focal point satisfies at least one of the following characteristics: (1) The surface and interior of the coke are porous, and the shape of the pores includes at least one of irregular circles, ellipses and elongated shapes; (2) The fracture surface after the coke is broken is sharp or irregular; (3) The cross-section of the coke is full of holes and produces fluorescence under ultraviolet light.

14. A negative electrode material, characterized in that, The negative electrode material comprises graphite, and the negative electrode material satisfies at least one of the following characteristics: (1) The raw material of the negative electrode material contains coke as described in any one of claims 1 to 13; (2) The method for preparing the negative electrode material includes: sequentially carbonizing and graphitizing the coke according to any one of claims 1 to 13 to obtain the negative electrode material.

15. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode material as described in claim 14.

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