High-sulfur petroleum coke-based carbon negative electrode material as well as preparation method and application thereof

Abstract

The invention relates to a high-sulfur petroleum coke-based carbon negative electrode material and a preparation method and application thereof.The non-stoichiometric titanium dioxide-coated carbon negative electrode material is obtained through a one-step reaction, and the preparation method mainly comprises the steps that under the liquid phase condition, a titanium source is dissolved in an organic solvent, particles obtained after high-sulfur petroleum coke is crushed are added, and a titanium dioxide-coated carbon negative electrode material is obtained; the titanium source is uniformly dispersed on the surfaces of particles obtained after the high-sulfur petroleum coke is crushed, and a precursor material with titanium dioxide dispersed on the surfaces of the particles obtained after the high-sulfur petroleum coke is crushed is obtained after drying; the precursor material is calcined for the first time and calcined for the second time, and the carbon negative electrode material with electrochemical catalytic activity is prepared. Compared with the prior art, the conductivity of the coating layer and the whole carbon negative electrode material is effectively improved; on the other hand, the defect center has relatively strong catalytic characteristics, so that the reaction activity of the sulfur element in the carbon negative electrode material can be improved, and the influence on the battery performance is reduced.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a high-sulfur petroleum coke-based carbon anode material, its preparation method, and its application. Background Technology

[0002] The transformation of society's energy structure has led to the widespread application of electrochemical energy storage technologies, represented by lithium-ion batteries, in various commercial energy storage scenarios. However, the Earth's lithium resources are finite and cannot meet all global energy storage needs. Therefore, finding complementary energy storage technologies to lithium-ion batteries has become a focal point of competition among countries in the new energy field. Sodium-ion batteries, similar in principle and structure to lithium-ion batteries, possess advantages such as low cost, excellent high and low temperature performance, and high rate performance, and are considered to have enormous commercial value in the energy storage field. However, the lack of anode materials that balance performance and cost has resulted in slow development of the commercial application of sodium-ion batteries. Therefore, it is urgent to find a sodium-ion battery anode material similar to the graphite anode material of lithium-ion batteries, possessing characteristics such as stable performance, low cost, and easy-to-scale production processes. This is the only way to break through the development bottleneck of large-scale commercial application of sodium-ion batteries.

[0003] Carbon materials possess high conductivity, diverse structures, and excellent chemical and physical properties, making them the optimal anode material for sodium-ion batteries. Carbon materials can be categorized into hard carbon and soft carbon. Hard carbon anode materials, derived from biomass and resins, offer advantages such as high specific capacity, but suffer from low carbon yield, complex processing, and high cost. Soft carbon materials, obtained from materials like pitch, have lower specific capacity. Therefore, developing low-cost, high-specific-capacity, and simple-process carbon anode materials for sodium-ion batteries is of immense value. High-sulfur petroleum coke, a byproduct of crude oil processing, has an annual domestic production capacity exceeding 10 million tons and is extremely inexpensive. Carbon materials derived from it exhibit high specific capacity due to the electrochemical activity of sulfur, but accompanying side reactions lead to low initial coulombic efficiency and poor cycle life, limiting their practical application.

[0004] Chinese patent CN202211148480.7 discloses a method for desulfurizing and modifying medium-to-high sulfur petroleum coke. The method involves mixing and calcining medium-to-high sulfur petroleum coke with a composite treatment agent to achieve desulfurization and modification, yielding a treated material. The treatment agent includes a carrier and an active component composited within the carrier. The active component comprises component A, component B, and component C. Component A is at least one nano-metal particle selected from iron and nickel; component B is at least one nano-metal particle selected from cobalt, molybdenum, potassium, and barium; and component C is boron. The molar ratio of components A, B, and C in the active component is 1:(0.01-0.5):(0.01-0.5). The atmosphere during the calcination stage is an ammonia-containing atmosphere and / or a water vapor-containing atmosphere. The temperature during the calcination stage is 400-800℃. The method for preparing graphite using medium-to-high sulfur petroleum coke and the application of the prepared graphite material in lithium-ion secondary batteries are also discussed. This technical solution is a conventional desulfurization process that utilizes the combined action of ammonia and a composite treatment agent to remove sulfur from high-sulfur petroleum coke. This solution uses sieving to separate the composite treatment agent and the semi-calcined desulfurized petroleum coke; however, due to their similar particle sizes, 100% separation cannot be achieved. Furthermore, the inability to achieve 100% desulfurization results in batch-to-batch instability of the sulfur content in the final material, hindering large-scale production. Therefore, a better technical solution would be one that maintains the electrochemical performance of the carbon material without desulfurization. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art by providing a high-sulfur petroleum coke-based carbon anode material, its preparation method, and its application. This invention allows for the preparation of a sodium-ion battery carbon anode material that combines high capacity and long cycle life without the need for desulfurization of the high-sulfur petroleum coke.

[0006] The objective of this invention can be achieved through the following technical solution: a method for preparing a high-sulfur petroleum coke-based carbon anode material, comprising the following steps:

[0007] S1. Pretreatment of high-sulfur petroleum coke raw material: The high-sulfur petroleum coke raw material is crushed to D50 = 3-6μm, preferably 4μm; then dried in air at 50-200℃ to reduce its water content to below 100ppm; the sulfur content is 3wt% to 10wt%.

[0008] S2. Preparation of titanium-containing solution: The titanium source is one or two of tetrabutyl titanate and isopropyl titanate, and the organic solvent is one or more of anhydrous ethanol, anhydrous methanol, and anhydrous ethylene glycol. The mass ratio of tetrabutyl titanate to organic solvent is 1:10-50, preferably 1:10-25. Finally, anhydrous citric acid is added to the titanium-containing organic solution at a mass ratio of 50-150:1, preferably 100:1, to obtain the titanium-containing solution.

[0009] S3. Titanium dioxide coating: The high-sulfur petroleum coke particles pretreated in step S1 are mixed evenly with the titanium-containing solution obtained in step S2 and then dried. The mass ratio of the titanium-containing solution to the pretreated particles is 0.5-3:100, the drying temperature is 50-200℃, and the drying atmosphere is air. Preferably, the mass ratio is 0.5-2:100 and the drying temperature is 80-150℃.

[0010] S4, First calcination (T1): Place the dried powder from step S3 into a graphite sagger, and heat it to 200-400°C, preferably 300°C, at 2°C / min under oxygen 0.01MPa, hold it at that temperature for 0.5-2 hours, and then let it cool naturally to room temperature.

[0011] S5. Blending and granulation: The cooled granules from step S4 are mixed with high softening point asphalt at a mass ratio of 100:5 to 15, wherein the softening point temperature of the asphalt must be ≥250℃, and the preferred mass ratio is 100:5 to 10. Then, the granules are shaped to D50 = 20-30μm using a blending and coating machine.

[0012] S6. Second calcination (T2): The shaped particles are placed in a graphite sagger and heated to 500-700℃ at a rate of 1-3℃ / min under a nitrogen atmosphere, preferably to 600℃ at a rate of 2℃ / min. Then, the temperature is increased to 900-1200℃ at a rate of 5-15℃ / min, preferably to 900-1200℃ at a rate of 10℃ / min. After holding at this temperature for 4-12 hours, the particles are crushed and graded to D50 = 5-8μm. Then, the particles are demagnetized to obtain the final carbon material.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. This invention obtains a non-stoichiometric titanium dioxide-coated carbon anode material through a one-step reaction. The main process involves dissolving a titanium source in an organic solvent under liquid-phase conditions, adding crushed high-sulfur petroleum coke particles, and uniformly dispersing the titanium source on the surface of the particles. After drying, a precursor material with titanium dioxide dispersed on the surface of the crushed high-sulfur petroleum coke particles is obtained. After the first calcination, this precursor material, under the synergistic effect of titanium dioxide, introduces more oxygen-containing functional groups. During the second calcination, the titanium dioxide on the surface of the precursor material transforms into the rutile phase. Subsequently, at higher temperatures, the titanium dioxide partially loses oxygen, deviating from the stoichiometric ratio (TiO2 = TiO2). 2-x Some oxygen and titanium atoms in TiO2 (+x / 2O2) leave their lattice positions, forming defect centers that possess electrochemical catalytic activity. On one hand, due to the generation of defects, a large number of charge carriers, including electrons and holes, are generated inside TiO2, greatly improving conductivity and thus effectively enhancing the conductivity of the coating layer and the entire carbon anode material. On the other hand, the defect centers possess strong catalytic properties, which can enhance the reactivity of sulfur in the carbon anode material and reduce its impact on battery performance.

[0015] 2. This invention employs a non-stoichiometric titanium dioxide-coated modified high-sulfur petroleum coke-based carbon anode material and its liquid-phase preparation method. Through a soluble titanium salt and a two-stage high-temperature treatment scheme, a carbon anode material with high specific capacity and high first-cycle coulombic efficiency is prepared.

[0016] 3. The carbon material prepared by this invention using petroleum coke as raw material, when used as a negative electrode material for sodium-ion batteries, exhibits a reversible specific capacity of 310.5 mAh / g, a coulombic efficiency of 82.1% in the first cycle, and a capacity retention rate of 99.5% after 50 cycles. In contrast, conventional methods yield sodium-ion battery carbon negative electrode materials with a coulombic efficiency of <70% in the first cycle and a capacity retention rate of <60% after 50 cycles. Furthermore, this technical solution also features a short process, simple operation, low cost, and environmental friendliness. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the physical structure of the carbon material obtained in Example 1.

[0018] Figure 2 This is a scanning electron microscope image of the carbon material obtained in Example 1. Detailed Implementation

[0019] The following examples illustrate the specific steps of the present invention. It should be understood that these examples are merely illustrative and not intended to limit the scope of the invention in any way. Various processes and methods not described in detail in this invention are conventional methods known in the art.

[0020] All raw materials involved in this invention are commercially available products in the field. For example, the high-sulfur petroleum coke raw materials used in the following embodiments have an ash content of <1% and a total transition metal impurity content of <1000ppm.

[0021] Example 1

[0022] A method for preparing a high-sulfur petroleum coke-based carbon anode material includes the following steps:

[0023] S1. Crush high-sulfur petroleum coke (c) into primary particles with a particle size of 3μm, and then dry it until the moisture content is less than 1000ppm.

[0024] S2. Add 2g of tetrabutyl titanate to 48g of anhydrous ethanol, and then add 0.5g of anhydrous citric acid to obtain a titanium-containing organic solution.

[0025] S3. Take 10g of titanium-containing organic solution and mix it evenly with 1000g of dried petroleum coke using a high-efficiency mixer. Then, take it out and dry it at a temperature of 120℃. Collect the evaporated ethanol for reuse.

[0026] S4. The dried powder is placed in a graphite crucible and heated to 300°C at 2°C / min under oxygen at 0.01 MPa. The temperature is maintained for 1 hour and then naturally cooled to room temperature.

[0027] S5. Mix the cooled particles with asphalt with a softening point of 250℃ at a mass ratio of 100:10, and then use a fusion coating machine to shape the particles to D50 = 20μm.

[0028] S6. Place the shaped particles in a graphite crucible and heat to 600℃ at 2℃ / min under a nitrogen atmosphere, then heat to 1050℃ at 10℃ / min and hold at that temperature for 6 hours. After particle crushing and grading to D50 = 5-8μm, demagnetize to obtain the final carbon material. Its structure is as follows: Figure 1 As shown, the middle part is high-sulfur petroleum coke-based amorphous carbon 1, which is coated with non-stoichiometric TiO2. 2-x Coating layer 2, the outermost layer is pitch-based amorphous carbon 3, the scanning electron microscope image of the resulting carbon material is as follows. Figure 2 As shown, the carbon material particles have a smooth surface and a relatively uniform smooth surface layer, indicating that the outermost layer of pitch-based amorphous carbon has achieved a uniform coating effect on the carbon material. On the smooth surface, some nanoscale dispersed TiO₂ can also be observed. 2-x These particles can serve as electrochemical catalytic active centers, thereby enhancing the reactivity of sulfur in carbon anode materials and reducing its impact on battery performance.

[0029] S7. The obtained carbon anode material is mixed with conductive agent Super P, dispersant NaCMC, binder SBR, and ultrapure water (18 MΩ / cm, 25℃) at a mass ratio of 8:1:0.4:0.6:15. The mixture is thoroughly mixed using a dual planetary mixer to obtain anode slurry. The obtained anode material is then coated onto conductive current collector aluminum foil and dried to form anode electrode sheet with an areal density of 6-10 mg / cm³. 2 ;

[0030] S8. In accordance with T / DCB 010—2024 "Technical Requirements for Hard Carbon Anode Materials for Sodium-ion Batteries", CR2032 coin cells were assembled in a dry glove box filled with argon, using the carbon anode electrode as the working electrode, metallic sodium as the counter electrode, 1 mol / L NaPF6 EC / DEC (volume ratio 1:1) as the electrolyte, and glass fiber as the separator. Electrochemical performance tests were conducted at room temperature in the voltage range of 0.001-2.0V, and the charge / discharge test current density was 0.1C.

[0031] Example 2

[0032] Compared with Example 1, the difference is that the particle size of the high-sulfur petroleum coke after crushing is changed to 5μm, while other operations and parameters are the same as in Example 1.

[0033] Example 3

[0034] Compared with Example 1, the difference is that the 10g titanium-containing organic solution in step S3 is replaced with 15g titanium-containing organic solution, and the other operations and parameters are the same as in Example 1.

[0035] Example 4

[0036] Compared with Example 1, the difference is that the 10g titanium-containing organic solution in step S3 is replaced with 20g titanium-containing organic solution, and the other operations and parameters are the same as in Example 1.

[0037] Compared with Example 1, Example 5 differs in that the high-sulfur petroleum coke with a sulfur content of 3wt% is replaced with 4wt%, and the 10g titanium-containing organic solution in step S3 is replaced with 30g titanium-containing organic solution. Other operations and parameters are the same as in Example 1.

[0038] Example 6

[0039] Compared with Example 5, the difference is that the 30g titanium-containing organic solution in step S3 is replaced with 40g titanium-containing organic solution, and the other operations and parameters are the same as in Example 1.

[0040] Example 7

[0041] Compared with Example 1, the difference is that the high-sulfur petroleum coke with a sulfur content of 3wt% is replaced with 5wt%, while other operations and parameters are the same as in Example 6.

[0042] Example 8

[0043] Compared with Example 1, the difference is that 1050°C in step S6 is changed to 950°C, while other operations and parameters are the same as in Example 1.

[0044] Example 9

[0045] Compared with Example 1, the difference is that 1050°C in step S6 is changed to 1150°C, while other operations and parameters are the same as in Example 1.

[0046] Example 10

[0047] Compared with Example 1, the difference is that 1050°C in step S6 is changed to 1250°C, while other operations and parameters are the same as in Example 1.

[0048] Comparative Example 1

[0049] Compared with Example 1, the difference is that no titanium-containing organic solution is added, while other operations and parameters are the same as in Example 1.

[0050] Comparative Example 2

[0051] Compared with Example 1, the difference is that the pre-calcination process at 300°C is not performed (i.e., the first calcination in step S4 is not included), while other operations and parameters are the same as in Example 1.

[0052] Comparative Example 3

[0053] Compared with Example 1, the particle size of the high-sulfur petroleum coke after crushing was changed to 5 μm, and no titanium-containing organic solution was added. Other operations and parameters were the same as in Example 1.

[0054] Comparative Example 4

[0055] Compared with Example 1, the particle size of the high-sulfur petroleum coke after crushing was changed to 5 μm, no titanium-containing organic solution was added, and no pre-calcination process at 300°C was performed. Other operations and parameters were the same as in Example 1.

[0056] Comparative Example 5

[0057] Compared with Example 1, the difference is that the high-sulfur petroleum coke with a sulfur content of 3wt% is replaced with 4wt%, and no titanium-containing organic solution is added. Other operations and parameters are the same as in Example 1.

[0058] Comparative Example 6

[0059] Compared with Example 1, the difference is that the high-sulfur petroleum coke with a sulfur content of 3wt% is replaced with 5wt%, and no titanium-containing organic solution is added. Other operations and parameters are the same as in Example 1.

[0060] The product performance test results obtained from each embodiment and comparative example are shown in Table 1 below:

[0061] Table 1 Test results of the examples and comparative examples

[0062]

[0063]

[0064] As shown in the table above, the high-sulfur petroleum coke-based carbon anode material modified with non-stoichiometric titanium dioxide coating exhibits high specific capacity and high first-cycle coulombic efficiency. On one hand, non-stoichiometric titanium dioxide generates a large number of charge carriers, including electrons and holes, significantly improving conductivity and thus effectively enhancing the conductivity of the coating layer and the entire carbon anode material. On the other hand, non-stoichiometric titanium dioxide possesses strong catalytic properties, which can enhance the reactivity of sulfur in the carbon anode material and reduce its impact on battery performance.

[0065] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0066] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0067] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a high-sulfur petroleum coke-based carbon anode material, characterized in that, Includes the following steps: S1. Pretreatment of high-sulfur petroleum coke raw material: crush the high-sulfur petroleum coke raw material to the target particle size; Then, it is dried in air at 50-200℃ to reduce its water content to below 100ppm, thus obtaining pretreated high-sulfur petroleum coke particles. S2. Preparation of titanium-containing solution: Mix titanium source with organic solvent at a mass ratio of 1:10 to 50, and then add anhydrous citric acid to the obtained titanium-containing organic solution. The mass ratio of titanium-containing organic solution to anhydrous citric acid is 50 to 150:1 to obtain titanium-containing solution. S3, Titanium dioxide coating: The high-sulfur petroleum coke particles pretreated in step S1 are mixed evenly with the titanium-containing solution obtained in step S2 and then dried. S4. First calcination: Place the dried powder from step S3 into a graphite sagger and keep it at a constant temperature of 200-400℃ for 0.5-2 hours; S5. Blending and granulation: Mix the granules obtained in step S4 with high softening point asphalt at a mass ratio of 100:5~15, and then use a blending and coating machine to shape the granules to D50 = 20-30μm. S6. Second calcination: The shaped particles are placed in a graphite sagger and heated to 500-700℃ at a rate of 1-3℃ / min under a nitrogen atmosphere, and then heated to 900-1200℃ at a rate of 5-15℃ / min. After holding at this temperature for 4-12 hours, the particles are crushed and demagnetized to obtain the final carbon material.

2. The method for preparing high-sulfur petroleum coke-based carbon anode material according to claim 1, characterized in that, The target particle size of the high-sulfur petroleum coke feedstock after crushing in step S1 is D50 = 3-6 μm; The sulfur content in the pretreated high-sulfur petroleum coke particles is 3wt% to 10wt%.

3. The method for preparing high-sulfur petroleum coke-based carbon anode material according to claim 1, characterized in that, In step S2, the titanium source is one or both of tetrabutyl titanate and isopropyl titanate. The organic solvent is one or more of anhydrous ethanol, anhydrous methanol, and anhydrous ethylene glycol. The mass ratio of titanium source to organic solvent is 1:10-25; The mass ratio of titanium-containing organic solution to anhydrous citric acid is 100:

1.

4. The method for preparing high-sulfur petroleum coke-based carbon anode material according to claim 1, characterized in that, In step S3, the mass ratio of the titanium-containing organic solution to the pretreated high-sulfur petroleum coke particles is 0.5–3:100, the drying temperature is 50–200°C, and the drying atmosphere is air.

5. The method for preparing high-sulfur petroleum coke-based carbon anode material according to claim 4, characterized in that, The mass ratio of the titanium source to the pretreated high-sulfur petroleum coke particles is 0.5–2:100, and the drying temperature is 80–150°C.

6. The method for preparing high-sulfur petroleum coke-based carbon anode material according to claim 1, characterized in that, Step S4, the first calcination, is carried out under oxygen at 0.01 MPa, with the temperature increased to the calcination temperature at 2 °C / min, and then naturally cooled to room temperature after calcination.

7. The method for preparing high-sulfur petroleum coke-based carbon anode material according to claim 1, characterized in that, In step S5, the mass ratio of the granules obtained from the first calcination to the high softening point asphalt is 100:5 to 10, wherein the softening point temperature of the asphalt is ≥250℃.

8. The method for preparing high-sulfur petroleum coke-based carbon anode material according to claim 1, characterized in that, In step S6, the particle crushing and grading process has a particle size distribution of D50 = 5-8 μm.

9. A high-sulfur petroleum coke-based carbon anode material prepared by the method described in any one of claims 1-8.

10. An application of the high-sulfur petroleum coke-based carbon anode material as described in claim 9, characterized in that, The carbon anode material is used as the anode material for sodium-ion secondary batteries.

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