A petroleum pitch-based hard carbon material, a preparation method and application thereof

Abstract

The application relates to the technical field of batteries, and particularly discloses a petroleum pitch-based hard carbon material and a preparation method and application thereof. The method takes petroleum pitch, a petroleum processing by-product, as a raw material, optimizes precursor components and improves the thermal stability of the precursor components through two-step mixed solvent extraction combined with in-situ pre-crosslinking reaction, then introduces a water-soluble inorganic salt template for melt mixing and pre-oxidation solidification, and finally obtains a hard carbon negative electrode material through water washing to remove the template after transition metal organic complex auxiliary segmented heat treatment, short-time high-temperature pulse treatment and CO2 short-time weak activation. The method solves the problems of complex petroleum pitch components, easy melt agglomeration in the carbonization process and poor structural uniformity from the raw material end, and the obtained material has excellent cycle stability and rate performance, can be simultaneously applied to sodium ion battery and lithium ion battery negative electrode systems, and has wide application prospects in the fields of electrochemical energy storage, new energy vehicles and consumer electronics.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a petroleum pitch-based hard carbon material, its preparation method, and its application. Background Technology

[0002] Hard carbon materials are a class of amorphous carbon materials that are difficult to fully graphitize. They typically possess a disordered carbon framework, localized graphite-like microcrystalline regions, and a certain degree of porous structure. They can be used in both lithium-ion and sodium-ion battery anode systems, demonstrating good application potential in both types of batteries. Currently, the demands for battery performance and cost in consumer electronics, new energy vehicles, and energy storage systems are continuously increasing. As a core component of batteries, the cost control, cycle life, rate performance, and raw material source stability of anode materials directly affect the overall performance and commercialization potential of the battery system. Therefore, developing hard carbon anode materials with lower costs, adjustable structure, and stable performance is of significant practical importance.

[0003] Petroleum bitumen is a heavy byproduct of petroleum processing. Its molecules contain numerous aromatic structures, it has a high carbon residue, and its raw material sources are abundant and stable, making it a promising precursor for hard carbon production. Compared to resin-based or some biomass-based precursors, petroleum bitumen has significant advantages in terms of raw material cost and large-scale supply capacity. Using it as a precursor to prepare hard carbon materials can achieve both low-cost mass production of hard carbon and high-value utilization of petroleum byproducts.

[0004] However, petroleum asphalt itself has a very complex composition, typically containing saturated components, aromatic components, resins, asphaltenes, and a small amount of inorganic ash. These different components exhibit significant differences in molecular weight, solubility, softening behavior, thermal condensation behavior, and residual carbon content. If raw petroleum asphalt is directly used for hard carbon production, the low-molecular-weight, lightweight components are prone to volatilization and loss during heating, or may cause excessive flow of the asphalt. The heavy asphaltenes, on the other hand, are prone to localized agglomeration, resulting in an uneven product structure and ultimately a decline in the electrochemical performance of the hard carbon material.

[0005] Current optimization of the performance of petroleum asphalt-based hard carbon materials largely relies on adjustments to subsequent carbonization processes, activation modification, or surface treatments. These methods fail to fundamentally address issues such as structural inhomogeneity and poor electrochemical performance resulting from complex precursor compositions. Therefore, how to control the composition of petroleum asphalt precursors to obtain hard carbon anode materials with uniform structure and excellent electrochemical performance has become a pressing technical problem in this field. Summary of the Invention

[0006] To address the problems of complex precursor composition in existing petroleum asphalt technologies, and the tendency for direct carbonization to lead to inhomogeneous structure and poor electrochemical performance in hard carbon materials, this invention provides a petroleum asphalt-based hard carbon material, its preparation method, and its applications. This invention regulates the precursor composition by selective solvent stepwise extraction and in-situ pre-crosslinking treatment of petroleum asphalt raw materials. Combined with steps such as template pore formation, transition metal-assisted carbonization, and short-term weak activation, a petroleum asphalt-based hard carbon anode material with uniform structure and excellent electrochemical performance is obtained.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a petroleum asphalt-based hard carbon material, comprising the following steps: S1, the petroleum asphalt raw material is mixed with a first mixed solvent for extraction, and solid-liquid separation is performed to obtain a first insoluble solid phase; wherein, the first mixed solvent includes toluene and n-heptane, and the volume content of n-heptane is greater than that of toluene; S2, the first insoluble solid phase, the second mixed solvent and the free radical initiator are mixed and extracted and in-situ pre-crosslinked under inert or low oxygen conditions. After the reaction is completed, the solid and liquid are separated, the second soluble extractable phase is taken, the solvent is removed, and the refined petroleum asphalt precursor is obtained; wherein, the second mixed solvent includes toluene and n-heptane, and the volume content of toluene is greater than that of n-heptane. S3, the refined petroleum asphalt precursor is heated and softened, and water-soluble inorganic salt template agent is added for melt mixing. The resulting mixture is pre-oxidized in an oxygen-containing atmosphere to solidify the refined petroleum asphalt precursor and obtain a pre-treated precursor. S4, the pretreated precursor is mixed with the transition metal organometallic complex and subjected to segmented heat treatment in an inert atmosphere to obtain a carbonized intermediate product. S5, the carbonization intermediate product is subjected to short-time high-temperature pulse treatment in an inert atmosphere. After the treatment, it is subjected to short-time weak activation treatment in an inert carrier gas containing CO2. Then it is cooled in an inert atmosphere, the water-soluble inorganic salt template agent is removed with water, and it is dried to obtain petroleum asphalt-based hard carbon anode material.

[0008] Compared to existing technologies, the preparation method of petroleum asphalt-based hard carbon materials provided by this invention employs a two-step extraction process with differentiated solvent ratios. First, a mixed solvent with a higher proportion of n-heptane is used to remove low-molecular-weight saturated hydrocarbons and highly mobile light components from the petroleum asphalt, preventing oligomer volatilization or coalescence during subsequent heat treatment and significantly improving the initial softening point and thermal stability of the precursor. Then, a mixed solvent with a higher proportion of toluene, combined with a free radical initiator, completes the pre-crosslinking reaction of asphalt molecules in situ during the extraction process. This achieves extraction of medium-molecular-weight aromatic and resinous components while simultaneously constructing a suitable three-dimensional network structure through in-situ pre-crosslinking, significantly improving the thermal stability and skeletal strength of the precursor. Based on this, a water-soluble inorganic salt template agent is introduced through melt mixing and pre-oxidized and cured, achieving uniform dispersion of the template in the asphalt matrix and stabilizing the precursor structure. Subsequent staged heat treatment with transition metal-organic complexes, high-temperature pulse treatment, and weak carbon dioxide activation treatment further regulate the pore structure, surface state, and interlayer distance of the carbon material, ultimately obtaining a petroleum pitch-based hard carbon anode material with high lithium or sodium storage capacity, good cycle stability, and excellent rate performance.

[0009] Further, in S1, the volume ratio of toluene to n-heptane in the first mixed solvent is 1:2 to 1:5, preferably 1:3.

[0010] The first mixed solvent uses toluene and n-heptane in a volume ratio of 1:2 to 1:5, making the solvent system generally weakly polar. Under this ratio, the solvent has a strong ability to dissolve low-molecular-weight non-polar components in petroleum asphalt, but a low solubility for aromatic components and gums. This is beneficial for selectively removing light components such as saturated hydrocarbons in the first extraction step, while ensuring that aromatic components and gums are fully retained in the first insoluble solid phase, reducing the loss of target components.

[0011] Further, in S1, the mass-to-volume ratio of the petroleum asphalt raw material to the first mixed solvent is 1g:(5~20)mL, preferably 1g:10mL.

[0012] Furthermore, in S1, the extraction temperature is 40℃~80℃, and the extraction time is 1h~4h.

[0013] Preferably, in S1, the extraction temperature is 60°C and the extraction time is 2 hours.

[0014] Within this temperature range, the first mixed solvent exhibits good dissolution kinetics for low-molecular-weight nonpolar components in petroleum asphalt, ensuring the effective dissolution of light components within a short time. Simultaneously, it avoids excessive dissolution and loss of aromatic components and resins, maintaining the enrichment level of the target components in the solid phase.

[0015] In some specific embodiments of the present invention, stirring is performed during the extraction process at a rate of 200 r / min to 500 r / min.

[0016] The purpose of step S1 is to remove some of the low-molecular-weight soluble components in petroleum asphalt, thereby reducing their adverse effects such as melt flow, volatile matter release, and localized agglomeration during subsequent mixing, pre-oxidation, and carbonization processes. This improves the thermal stability and structural uniformity of the asphalt precursor from the raw material end, laying the foundation for a stable reaction in subsequent processes.

[0017] Further, in S2, the volume ratio of toluene to n-heptane in the second mixed solvent is 2:1 to 5:1, preferably 3:1.

[0018] The second mixed solvent uses a toluene to n-heptane volume ratio of 2:1 to 5:1, making the solvent system toluene dominant and significantly more polar than the first step. At this ratio, the solvent exhibits excellent solubility for aromatic components and gums, enabling efficient extraction of the target components retained in the solid phase in the first step into the liquid phase. Simultaneously, the presence of a small amount of n-heptane prevents excessive dissolution of highly polar heavy components, maintaining the selectivity of the extraction system. Complementing the weakly polar solvent with a low toluene ratio in the first step, the two-step extraction achieves the stepwise separation of non-target light components from the target aromatic components in petroleum asphalt.

[0019] Further, in S2, the mass-volume ratio of the first insoluble solid phase to the second mixed solvent is 1g:(5~20)mL, preferably 1g:10mL.

[0020] Furthermore, in S2, the extraction and in-situ pre-crosslinking reaction are carried out at a temperature of 60°C to 85°C for a time of 1.5h to 4h.

[0021] In some specific embodiments of the present invention, stirring is performed during the extraction and in-situ pre-crosslinking reaction, and the stirring rate is 200 r / min to 500 r / min.

[0022] In some specific embodiments of the present invention, after the extraction and in-situ pre-crosslinking reaction are completed, the temperature is maintained at 70℃~90℃ for 0.5h~2h to promote the decomposition of residual free radical initiators.

[0023] Furthermore, in S2, the free radical initiator is an azo radical initiator or a peroxide radical initiator.

[0024] The free radical initiator decomposes under heating conditions to generate free radicals, which initiate a mild pre-crosslinking reaction between aromatic components and gum molecules in the first insoluble solid phase. This moderately increases the molecular weight and softening point of the refined petroleum asphalt precursor, which is beneficial for maintaining structural stability during subsequent pre-oxidation and carbonization processes.

[0025] Specifically, azo radical initiators can be selected from azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, etc. Peroxide radical initiators can be selected from benzoyl peroxide, dilauryl peroxide, dicumyl peroxide, etc.

[0026] Further, in S2, the amount of the free radical initiator added is 0.05% to 0.2% of the mass of the first insoluble solid phase, preferably 0.08% to 0.15%.

[0027] When the initiator dosage is too low, the concentration of free radicals generated by decomposition is insufficient to initiate effective intermolecular bridging between aromatic and resinous molecules, making it difficult to achieve the desired effect of moderately increasing the softening point and char content. When the initiator dosage is too high, excessive cross-linking is likely to occur, leading to a significant increase in the precursor's softening point and poor melt processability, which is detrimental to the subsequent uniform mixing with the template agent. The above-mentioned preferred dosage range can achieve controllable mild pre-cross-linking at a lower initiator dosage, enabling the refined petroleum asphalt precursor to obtain a suitable increase in molecular weight and improved thermal stability, while maintaining good subsequent processing performance.

[0028] It should be noted that the in-situ pre-crosslinking reaction described in this invention is a mild pre-crosslinking. It does not bring the petroleum asphalt to a completely solidified state, nor does it cause large-scale crosslinking of the aromatic ring main structure. Instead, it induces limited intermolecular bridging between the extracted aromatic components and the resinous components in a solution-dispersed state. By controlling the amount of free radical initiator, reaction temperature, and time, the degree of pre-crosslinking is controlled within an appropriate range, moderately increasing the softening point and char residue of the refined petroleum asphalt precursor, enhancing its thermal stability, and avoiding the problem of excessive crosslinking leading to uneven softening and dispersion of the precursor during subsequent melt mixing. This mild pre-crosslinking treatment effectively reduces the risk of excessive flow and component agglomeration of the precursor during subsequent melt mixing and the initial stage of carbonization, which is beneficial to the uniform dispersion of the template agent and the uniformity of the final hard carbon material structure.

[0029] The refined petroleum asphalt precursor obtained in S2 exhibits the following performance characteristics: softening point of 72℃~78℃; 550℃ Concordant char content of 30%~38%; gel permeation chromatography (GPC) analysis shows a number-average molecular weight (Mn) of 450~800 g / mol, a weight-average molecular weight (Mw) of 800~1500 g / mol, and a molecular weight distribution index (PDI) of 1.6~2.0. These molecular weight and distribution characteristics demonstrate that the in-situ pre-crosslinking treatment achieved a mild pre-crosslinking effect, preventing excessive crosslinking of the precursor and loss of processability, while effectively improving the precursor's thermal stability and carbonization performance, providing a homogeneous precursor base for subsequent pre-oxidation, carbonization, and pore-forming processes.

[0030] In some specific embodiments of the present invention, in step S2, the solvent in the second soluble extractable phase is removed by decompression. First, most of the mixed solvent is removed under reduced pressure at 80°C to 120°C, and then the temperature is raised to 250°C to 320°C to remove residual dissolved components and a small amount of volatile components under reduced pressure. Specifically, the pressure used for decompression is -0.08 MPa to -0.10 MPa.

[0031] Furthermore, in S3, the water-soluble inorganic salt template agent is at least one of sodium sulfate, sodium chloride, sodium carbonate, or potassium carbonate.

[0032] During the melt mixing stage, the selected template agent maintains a solid particle form within the softening temperature window of the refined petroleum asphalt precursor and does not react chemically with the asphalt matrix. After mixing, it can be uniformly dispersed in the precursor matrix. In the subsequent pre-oxidation and carbonization stages, the space occupied by the template agent particles is removed by water washing and forms pores in situ, achieving uniform pore formation.

[0033] Compared to asphalt without in-situ pre-crosslinking treatment, the refined petroleum asphalt precursor obtained by in-situ pre-crosslinking treatment in step S2 exhibits appropriately reduced fluidity in the subsequent S3 melt mixing stage. This moderate reduction in fluidity avoids excessive encapsulation of inorganic salt template agent particles by the precursor, which is beneficial for the uniform dispersion of the template agent in the precursor matrix and lays the foundation for the formation of a uniformly distributed pore structure in the subsequent carbonization stage.

[0034] Furthermore, in S3, the amount of water-soluble inorganic salt template agent added is 2% to 8% of the mass of refined petroleum asphalt precursor, preferably 4%.

[0035] The optimal amount of template agent added allows the template agent to be uniformly dispersed and appropriately coated in the precursor matrix. After subsequent carbonization and water washing, a sufficient number of uniformly distributed pore structures can be formed in the carbon skeleton, taking into account both the increase in specific surface area and the maintenance of structural strength.

[0036] Furthermore, in S3, the temperature of the melt mixing is 140℃~180℃, and the mixing time is 20min~40min.

[0037] Preferably, in S3, the temperature of the melt mixing is 160°C and the mixing time is 30 min.

[0038] In some specific embodiments of the present invention, stirring is carried out during the melt mixing process, and the stirring speed is 300 r / min to 800 r / min.

[0039] Furthermore, in S3, the temperature of the pre-oxidation treatment is 200℃~260℃, and the treatment time is 1h~4h.

[0040] Preferably, in S3, the temperature of the pre-oxidation treatment is 220°C and the treatment time is 2 hours.

[0041] Low-temperature pretreatment in an oxygen-containing atmosphere causes moderate solidification of the precursor. This solidification effect effectively inhibits the softening and flow of the precursor during subsequent staged heat treatment, thereby fixing the template agent particles in their initial dispersion positions and preventing template agent migration and local agglomeration caused by the decrease in precursor viscosity. The space occupied by the template agent particles is subsequently transformed into pores after water washing. Because the template agent maintains its initial dispersion state throughout the carbonization process, the resulting hard carbon material exhibits uniform pore size distribution and stable pore structure, providing a regular pore network for ion transport in the electrode material.

[0042] Further, in S4, the transition metal organometallic complex includes at least one of ferrocene, cobalt dicene, or iron acetylacetonate.

[0043] These transition metal organometallic complexes can serve as auxiliary regulating components in the heat treatment process, promoting the condensation process of aromatic structures in the precursor, regulating the stacking state of local carbon layers, and helping to optimize the microcrystalline structure of hard carbon materials.

[0044] Furthermore, in S4, the amount of the transition metal organometallic complex added is 0.1% to 0.3% of the mass of the pretreated precursor.

[0045] Furthermore, in S4, the segmented heat treatment specifically includes the following steps: First, keep warm at 300℃~400℃ for 60min~120min, then keep warm at 380℃~490℃ for 40min~80min, and finally keep warm at 580℃~720℃ for 30min~60min.

[0046] Specifically, in S4, the heating rate of the staged heat treatment step is 1℃ / min to 2℃ / min.

[0047] In this step, since the obtained refined pre-crosslinked asphalt precursor already has a high softening point and weak melt flowability, it is easier to maintain a relatively uniform precursor structure during the segmented heat treatment process. The first stage mainly promotes further softening and initial condensation of the precursor; the second stage is conducive to the local regularization of the aromatic structure and further condensation; the third stage mainly promotes condensation, crosslinking and carbon skeleton fixation.

[0048] Furthermore, in S5, the temperature of the short-time high-temperature pulse treatment is 900℃~1100℃, the holding time of a single pulse treatment is 30s~70s, the number of pulse treatments is 1~3, and the heating and cooling rates are both not less than 50℃ / min.

[0049] This step employs a short-duration high-temperature pulse treatment, rather than the conventional long-duration high-temperature isothermal treatment. The short-duration high-temperature environment can provide energy for local adjustments to the carbon structure, helping to reduce unstable defects and edge active sites within the material. At the same time, due to the shorter duration of the high temperature, the risk of excessive shrinkage of the hard carbon structure and significant changes in the pore structure caused by long-duration high-temperature treatment can be effectively reduced.

[0050] In some specific embodiments, the short-time high-temperature pulse processing is performed twice, specifically including the following steps: The carbonization intermediate product is held at 580℃~720℃, then heated to 900℃~1050℃ and held for 50s~70s, then cooled to 580℃~720℃; then heated to 1000℃~1100℃ and held for 30s~50s, then cooled to 580℃~720℃.

[0051] Further, in S5, the CO2-containing inert carrier gas is a mixture of CO2 and an inert gas, wherein the volume fraction of CO2 is 0.3% to 1.0%, preferably 0.5%.

[0052] Specifically, the inert gas is argon, nitrogen, or a mixture thereof.

[0053] Furthermore, in S5, the temperature of the short-time weak activation treatment is 600℃~800℃, and the treatment time is 10min~15min.

[0054] Preferably, in S5, the temperature of the short-time weak activation treatment is 720℃~780℃, and the treatment time is 12min.

[0055] This process uses CO2 as the activation medium to regulate the surface oxygen-containing functional groups and surface reactivity of hard carbon materials through a mild gas-solid reaction. Unlike traditional strong activation processes, this process does not primarily aim to significantly increase the specific surface area of ​​the material, and has less impact on the bulk pore structure of the carbon material. It can improve the interfacial electrochemical state while reducing the risk of increased irreversible side reactions caused by excessive etching introducing too many defect sites, thus balancing the rate performance and first coulombic efficiency of hard carbon materials.

[0056] In some specific implementations, water-soluble inorganic salt template agents are removed by boiling and washing with deionized water.

[0057] Furthermore, in S5, the drying temperature is 100℃~150℃, and the drying time is 10h~15h.

[0058] In some specific embodiments, the drying process further includes ball milling and sieving. Specifically, the ball milling speed is 200 r / min to 400 r / min, and the milling time is 0.5 h to 2 h. Sieving can be performed using a 100 to 400 mesh screen, preferably a 200 mesh screen.

[0059] It should be noted that the inert atmosphere described in this invention is provided by conventional inert gases in the art, such as nitrogen and argon, and this invention does not impose any special limitations.

[0060] Secondly, the present invention provides a petroleum asphalt-based hard carbon material, which is prepared by the above-mentioned method for preparing petroleum asphalt-based hard carbon material.

[0061] Thirdly, the present invention also provides a negative electrode comprising the aforementioned petroleum pitch-based hard carbon material.

[0062] Because of its uniform pore structure, optimized local carbon layer order, and suitable surface chemical state, this hard carbon material exhibits high reversible capacity and initial coulombic efficiency when used as a negative electrode active material. At the same time, it maintains good electrode structure stability and low capacity decay during cycling.

[0063] The negative electrode is composed of the petroleum asphalt-based hard carbon material as the negative electrode active material, together with a conductive agent, a binder, and a current collector. The conductive agent can be any conventional conductive carbon material in the art, such as acetylene black, Super P, carbon nanotubes, or graphene; the binder can be a composite system of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR), or polyacrylic acid (PAA); the current collector is preferably copper foil or aluminum foil. The negative electrode sheet can be prepared using a conventional slurry coating process in the art, which involves uniformly mixing the petroleum asphalt-based hard carbon material, the conductive agent, and the binder in a certain proportion in a solvent to form a slurry, coating it onto the surface of the current collector, and then drying and rolling it to obtain the negative electrode sheet.

[0064] Fourthly, the present invention provides the application of the above-mentioned petroleum asphalt-based hard carbon material or the aforementioned negative electrode in the preparation of sodium-ion batteries or lithium-ion batteries.

[0065] The hard carbon material provided by this invention, as a negative electrode active material, can be adapted to both sodium-ion batteries and lithium-ion batteries, and can be widely used in many fields such as portable consumer electronics, large-scale electrochemical energy storage power stations, low-speed electric vehicles and new energy vehicles.

[0066] In practical applications, the petroleum asphalt-based hard carbon material of the present invention can be used as the negative electrode active material. It is mixed and dispersed with conductive agent and binder in a certain proportion to prepare negative electrode slurry, which is coated on the surface of current collector. After drying and rolling, negative electrode sheet is obtained. Then, it is assembled with the corresponding positive electrode sheet, electrolyte, separator and battery accessories to obtain sodium-ion battery or lithium-ion battery.

[0067] Fifthly, the present invention also provides a sodium-ion battery comprising the above-mentioned petroleum pitch-based hard carbon material or the above-mentioned negative electrode.

[0068] In addition to the negative electrode made of petroleum pitch-based hard carbon material, the sodium-ion battery also includes conventional components such as a positive electrode, a separator, an electrolyte, and a battery casing. Each component can be made using commercially available materials and manufacturing processes that are mature in the field.

[0069] The positive electrode can be a sodium-containing positive electrode active material known in the art, such as layered transition metal oxides, polyanionic compounds, or Prussian blue compounds. The separator can be a single-layer polypropylene (PP) or polyethylene (PE) membrane, a PP / PE multilayer composite membrane, or a glass fiber separator. The electrolyte is typically prepared by dissolving a sodium salt electrolyte (such as sodium hexafluorophosphate NaPF6) in an organic solvent (such as one or more mixed solvents like ethylene carbonate EC, dimethyl carbonate DMC, and ethyl methyl carbonate EMC), and film-forming additives can be added as needed to further optimize battery performance.

[0070] The assembly form of this sodium-ion battery is not particularly limited. It can be made into button cells, pouch cells, or square or cylindrical hard-shell cells, which can adapt to the specifications and performance requirements of different application scenarios.

[0071] In a sixth aspect, the present invention also provides a lithium-ion battery comprising the above-described petroleum pitch-based hard carbon material or the above-described negative electrode.

[0072] The lithium-ion battery also includes conventional components such as positive electrode, separator, electrolyte and battery casing, and each component can be adapted to existing mature lithium-ion battery material systems and manufacturing processes.

[0073] The positive electrode uses lithium-containing active materials of conventional types in the field, including but not limited to ternary nickel-cobalt-manganese materials. The separator can be made of polypropylene (PP), polyethylene (PE), etc. The electrolyte is typically prepared by dissolving a lithium salt electrolyte in an organic solvent. Common lithium salts include lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI). The organic solvent can be a composite solvent system formed by mixing one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a specific ratio. Film-forming additives and other functional agents can be added to the electrolyte according to actual performance requirements.

[0074] The packaging form of this lithium-ion battery is not particularly limited. It can be made into button cells, pouch cells, square aluminum-cased cells, or cylindrical cells, etc., to meet the application needs of different fields such as consumer electronics, new energy vehicles, and electrochemical energy storage.

[0075] In summary, this invention provides a method for preparing petroleum asphalt-based hard carbon materials. This method uses petroleum asphalt, a byproduct of petroleum processing, as raw material. It optimizes the precursor composition and improves its thermal stability through a two-step mixed solvent extraction combined with an in-situ pre-crosslinking reaction. Subsequently, a water-soluble inorganic salt template is introduced for melt mixing and pre-oxidation curing. Following this, the material undergoes segmented heat treatment assisted by a transition metal-organic complex, short-time high-temperature pulse treatment, and short-time weak activation with CO2. Finally, the template is removed by water washing to obtain the hard carbon anode material. This method solves the problems of complex petroleum asphalt composition, easy melting and agglomeration during carbonization, and poor structural uniformity from the raw material end. The resulting material exhibits excellent cycle stability and rate performance, and can be applied to both sodium-ion and lithium-ion battery anode systems, showing broad application prospects in electrochemical energy storage, new energy vehicles, and consumer electronics. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0077] To better illustrate the present invention, further examples are provided below.

[0078] Example 1 This embodiment provides a method for preparing a petroleum asphalt-based hard carbon material, including the following steps: Step 1: Add the petroleum asphalt raw material to a first mixed solvent consisting of toluene and n-heptane in a volume ratio of 1:3. The ratio of petroleum asphalt raw material to the first mixed solvent is 1g:10mL. Place the above mixture in a 60℃ water bath and stir and extract for 2 hours at a speed of 400r / min. After extraction, let it stand for 30 minutes. The system will separate into layers. Discard the upper first soluble extractable phase and retain the first insoluble solid phase. Step 2: Add a second mixed solvent consisting of toluene and n-heptane in a volume ratio of 3:1 to the first insoluble solid phase. The ratio of the first insoluble solid phase to the second mixed solvent is 1 g: 10 mL. Simultaneously add azobisisobutyronitrile (AIBN) at a concentration of 0.1% of the mass of the first insoluble solid phase. Place the system under a nitrogen atmosphere and carry out extraction and in-situ pre-crosslinking reaction at 70 °C and 400 r / min for 2.5 h. Then, continue to keep the temperature at 80 °C for 1 h to promote the decomposition of residual free radical initiators. After the reaction is completed, let it stand for 30 min, take the upper second soluble extractable phase, filter it through a 0.22 μm filter membrane, and then remove most of the mixed solvent by vacuum at 100 °C. Then, raise the temperature to 300 °C and remove residual dissolved and a small amount of volatile components by vacuum at a pressure of -0.09 MPa. After distillation, cool to room temperature and pulverize to obtain refined petroleum asphalt precursor. Step 3: After heating the above refined petroleum asphalt precursor to a softened state, add anhydrous sodium sulfate at a rate of 4% of the mass of the refined petroleum asphalt precursor. Then, melt-mix the mixture at 160℃ and 600r / min for 30min. After mixing, transfer the resulting mixture into a tube furnace, introduce compressed air at a flow rate of 100mL / min, and pre-oxidize at 220℃ for 2h to obtain the pretreated precursor. Step 4: Add ferrocene to the pretreated precursor. The amount added is 0.15% of the mass of the pretreated precursor. Dry mix for 10 min. Then place the mixture in a tube furnace and introduce high-purity nitrogen at a flow rate of 100 mL / min. Heat to 370℃ at a rate of 1.5℃ / min and hold for 90 min. Then hold at 450℃ for 60 min and finally hold at 650℃ for 45 min. After completion, continue to maintain the nitrogen atmosphere and adjust the nitrogen flow rate to 150 mL / min. Step 5: Rapidly heat from 650℃ to 1000℃, hold for 60s, then rapidly cool to 650℃; then rapidly heat to 1050℃, hold for 45s, then cool to 650℃. The heating and cooling rates should not be less than 50℃ / min. After the short-term high-temperature pulse treatment, switch the atmosphere to a mixture of CO2 and inert gas, with a CO2 volume fraction of 0.5%. Hold at 750℃ for 12min, cool to room temperature under an inert atmosphere, remove the sample, and wash it three times with deionized water for 30min each time. Dry the washed sample under vacuum at 120℃ for 12h, then ball mill at 300r / min for 1h, and sieve through a 200-mesh sieve to obtain petroleum asphalt-based hard carbon material, denoted as HC-A1.

[0079] Example 2 This embodiment provides a method for preparing a petroleum asphalt-based hard carbon material, including the following steps: Step 1: Add the petroleum asphalt raw material to a first mixed solvent consisting of toluene and n-heptane in a volume ratio of 1:2. The ratio of petroleum asphalt raw material to the first mixed solvent is 1g:20mL. Place the above mixture in a 40℃ water bath and stir at 200r / min for 4h. After extraction, let it stand for 30min. The system will separate into layers. Discard the upper first soluble extractable phase and retain the first insoluble solid phase. Step 2: Add a second mixed solvent consisting of toluene and n-heptane in a volume ratio of 4:1 to the first insoluble solid phase. The ratio of the first insoluble solid phase to the second mixed solvent is 1 g: 15 mL. Simultaneously add azobisisobutyronitrile (AIBN) at a concentration of 0.05% of the mass of the first insoluble solid phase. Place the system under a nitrogen atmosphere and carry out extraction and in-situ pre-crosslinking reaction at 85°C and 500 r / min for 1.5 h. Then continue to keep it at 90°C for 0.5 h to promote the decomposition of residual free radical initiator. After the reaction is completed, let it stand for 30 min, take the upper second soluble extract phase, filter it through a 0.22 μm filter membrane, and then remove most of the mixed solvent under reduced pressure at 90°C. Then raise the temperature to 250°C and remove residual dissolved and a small amount of volatile components under reduced pressure at -0.08 MPa. After distillation, cool to room temperature and pulverize to obtain refined petroleum asphalt precursor. Step 3: After heating the above refined petroleum asphalt precursor to a softened state, add anhydrous sodium chloride at a rate of 2% of the mass of the refined petroleum asphalt precursor. Then, melt-mix the mixture at 150°C and 500 r / min for 35 min. After mixing, transfer the resulting mixture to a tube furnace, introduce compressed air at a flow rate of 100 mL / min, and pre-oxidize it at 200°C for 4 h to obtain the pretreated precursor. Step 4: Add cobalt dicene to the pretreated precursor. The amount added is 0.1% of the mass of the pretreated precursor. Dry mix for 10 min. Then place the mixture in a tube furnace and introduce high-purity nitrogen at a flow rate of 100 mL / min. Heat to 350℃ at a rate of 1℃ / min and hold for 70 min. Then hold at 470℃ for 50 min and finally hold at 680℃ for 40 min. After completion, continue to maintain the nitrogen atmosphere and adjust the nitrogen flow rate to 150 mL / min. Step 5: Rapidly raise the temperature from 680℃ to 1020℃, hold for 60s, then rapidly cool to 680℃; then rapidly raise the temperature to 1070℃, hold for 45s, then cool to 680℃. The heating and cooling rates should not be less than 50℃ / min. After the short-term high-temperature pulse treatment, switch the atmosphere to a mixture of CO2 and inert gas, with a CO2 volume fraction of 0.3%. Hold at 800℃ for 10min, cool to room temperature under an inert atmosphere, remove the sample, and wash it three times with deionized water for 30min each time. Dry the washed sample under vacuum at 120℃ for 12h, then ball mill at 300r / min for 1h, and sieve through a 200-mesh sieve to obtain petroleum asphalt-based hard carbon material, denoted as HC-A2.

[0080] Example 3 This embodiment provides a method for preparing a petroleum asphalt-based hard carbon material, including the following steps: Step 1: Add the petroleum asphalt raw material to a first mixed solvent consisting of toluene and n-heptane in a volume ratio of 1:4. The ratio of petroleum asphalt raw material to the first mixed solvent is 1g:15mL. Place the above mixture in an 80℃ water bath and stir and extract for 1h at a speed of 500r / min. After extraction, let it stand for 30min. The system will separate into layers. Discard the upper first soluble extractable phase and retain the first insoluble solid phase. Step 2: Add a second mixed solvent consisting of toluene and n-heptane in a volume ratio of 2:1 to the first insoluble solid phase. The ratio of the first insoluble solid phase to the second mixed solvent is 1 g: 20 mL. Simultaneously add azobisisobutyronitrile (AIBN) at a concentration of 0.2% of the mass of the first insoluble solid phase. Place the system under a nitrogen atmosphere and carry out extraction and in-situ pre-crosslinking reaction at 60 °C and 200 r / min for 4 h. Then, continue to keep the temperature at 70 °C for 2 h to promote the decomposition of residual free radical initiators. After the reaction is completed, let it stand for 30 min, take the upper second soluble extractable phase, filter it through a 0.22 μm filter membrane, and then remove most of the mixed solvent under reduced pressure at 80 °C. Then, raise the temperature to 320 °C and remove residual dissolved and a small amount of volatile components under reduced pressure at -0.10 MPa. After distillation, cool to room temperature and pulverize to obtain refined petroleum asphalt precursor. Step 3: After heating the above refined petroleum asphalt precursor to a softened state, add anhydrous sodium carbonate at a rate of 6% of the mass of the refined petroleum asphalt precursor. Then, melt-mix the mixture at 140℃ and 300r / min for 40min. After mixing, transfer the resulting mixture into a tube furnace, introduce compressed air at a flow rate of 100mL / min, and pre-oxidize it at 260℃ for 1h to obtain the pretreated precursor. Step 4: Add ferrocene to the above pretreated precursor at a rate of 0.2% of the precursor mass. Dry mix for 10 min. Then place the mixture in a tube furnace and introduce high-purity nitrogen at a flow rate of 100 mL / min. Heat to 400℃ at a rate of 2℃ / min and hold for 60 min. Then hold at 490℃ for 40 min and finally hold at 720℃ for 30 min. After completion, continue to maintain the nitrogen atmosphere and adjust the nitrogen flow rate to 150 mL / min. Step 5: Rapidly raise the temperature from 720℃ to 1050℃, hold for 50s, then rapidly cool to 720℃; then rapidly raise the temperature to 1100℃, hold for 30s, then cool to 720℃. The heating and cooling rates should not be less than 50℃ / min. After the short-term high-temperature pulse treatment, switch the atmosphere to a mixture of CO2 and inert gas, with a CO2 volume fraction of 1.0%. Hold at 750℃ for 13min, cool to room temperature under an inert atmosphere, remove the sample, and wash it three times with deionized water for 30min each time. Dry the washed sample under vacuum at 120℃ for 12h, then ball mill at 300r / min for 1h, and sieve through a 200-mesh sieve to obtain petroleum asphalt-based hard carbon material, denoted as HC-A3.

[0081] Example 4 This embodiment provides a method for preparing a petroleum asphalt-based hard carbon material, including the following steps: Step 1: Add the petroleum asphalt raw material to a first mixed solvent consisting of toluene and n-heptane in a volume ratio of 1:5. The ratio of petroleum asphalt raw material to the first mixed solvent is 1g:5mL. Place the above mixture in a 50℃ water bath and stir and extract for 3h at a speed of 300r / min. After extraction, let it stand for 30min. The system will separate into layers. Discard the upper first soluble extractable phase and retain the first insoluble solid phase. Step 2: Add a second mixed solvent consisting of toluene and n-heptane in a volume ratio of 5:1 to the first insoluble solid phase. The ratio of the first insoluble solid phase to the second mixed solvent is 1 g: 5 mL. Simultaneously, add azobisisobutyronitrile (AIBN) at a concentration of 0.15% of the mass of the first insoluble solid phase. Place the system under a nitrogen atmosphere and carry out extraction and in-situ pre-crosslinking reaction at 70°C and 300 r / min for 3 h. Then, continue to keep the temperature at 85°C for 1 h to promote the decomposition of residual free radical initiators. After the reaction is completed, let it stand for 30 min, take the upper second soluble extractable phase, filter it through a 0.22 μm filter membrane, and then remove most of the mixed solvent under reduced pressure at 120°C. Then, raise the temperature to 280°C and remove residual dissolved and a small amount of volatile components under reduced pressure at -0.09 MPa. After distillation, cool to room temperature and pulverize to obtain refined petroleum asphalt precursor. Step 3: After heating the above refined petroleum asphalt precursor to a softened state, add anhydrous potassium carbonate at a rate of 8% of the mass of the refined petroleum asphalt precursor. Then, melt and knead the mixture at 180°C and 800 r / min for 20 min. After kneading, transfer the resulting mixture into a tube furnace, introduce compressed air at a flow rate of 100 mL / min, and pre-oxidize it at 240°C for 2 h to obtain the pretreated precursor. Step 4: Add acetylacetone iron to the above pretreated precursor at a rate of 0.3% of the pretreated precursor mass, dry mix for 10 min, then place the mixture in a tube furnace, introduce high-purity nitrogen at a flow rate of 100 mL / min, heat to 300 °C at a rate of 1 °C / min, hold for 120 min, then hold at 380 °C for 80 min, and finally hold at 580 °C for 60 min. After completion, continue to maintain the nitrogen atmosphere, and adjust the nitrogen flow rate to 150 mL / min. Step 5: Rapidly raise the temperature from 580℃ to 900℃, hold for 70s, then rapidly cool to 580℃; then rapidly raise the temperature to 1000℃, hold for 50s, then cool to 580℃. The heating and cooling rates should not be less than 50℃ / min. After the short-term high-temperature pulse treatment, switch the atmosphere to a mixture of CO2 and inert gas, with a CO2 volume fraction of 0.8%. Hold at 600℃ for 15min, cool to room temperature under an inert atmosphere, remove the sample, and wash it three times with deionized water for 30min each time. Dry the washed sample under vacuum at 120℃ for 12h, then ball mill at 300r / min for 1h, and sieve through a 200-mesh sieve to obtain petroleum asphalt-based hard carbon material, denoted as HC-A4.

[0082] Comparative Example To verify the role and technical effect of each process step in the preparation method of the present invention, the following comparative examples were set up. Except for the process differences that are clearly stated, the selection of raw materials, dosage and other process parameters of each comparative example are consistent with those of Example 1.

[0083] Comparative Example 1 This comparative example provides a method for preparing a petroleum pitch-based hard carbon material, which differs from Example 1 only in that steps one and two are omitted, i.e., untreated petroleum pitch raw material is used directly as the precursor material. The specific steps are as follows: Step 1: After heating the petroleum asphalt raw material to a softened state, add anhydrous sodium sulfate at a rate of 4% of the mass of the petroleum asphalt raw material. Then, melt-mix the mixture at 160℃ and 600r / min for 30min. After mixing, transfer the resulting mixture into a tube furnace, introduce compressed air at a flow rate of 100mL / min, and pre-oxidize it at 220℃ for 2h to obtain the pretreated precursor. Step 2: Add ferrocene to the pretreated precursor, the amount of which is 0.15% of the mass of the pretreated precursor. Dry mix for 10 min, then place the mixture in a tube furnace and introduce high-purity nitrogen at a flow rate of 100 mL / min. Heat to 370°C at a rate of 1.5°C / min and hold for 90 min. Then hold at 450°C for 60 min and finally hold at 650°C for 45 min. After completion, continue to maintain the nitrogen atmosphere and adjust the nitrogen flow rate to 150 mL / min. Step 3: Rapidly raise the temperature from 650℃ to 1000℃, hold for 60s, then rapidly cool to 650℃; then rapidly raise the temperature to 1050℃, hold for 45s, then cool to 650℃. The heating and cooling rates should not be less than 50℃ / min. After the short-term high-temperature pulse treatment, switch the atmosphere to a mixture of CO2 and inert gas, with a CO2 volume fraction of 0.5%. Hold at 750℃ for 12min, cool to room temperature under an inert atmosphere, remove the sample, and wash it three times with deionized water for 30min each time. Dry the washed sample under vacuum at 120℃ for 12h, then ball mill at 300r / min for 1h, and sieve through a 200-mesh sieve to obtain petroleum asphalt-based hard carbon material, denoted as D-A1.

[0084] Comparative Example 2 This comparative example provides a method for preparing a petroleum asphalt-based hard carbon material. The only difference from Example 1 is that step one is omitted and AIBN is not added in step two. The rest is exactly the same and will not be described again here. The obtained petroleum asphalt-based hard carbon material is denoted as D-A2.

[0085] Comparative Example 3 This comparative example provides a method for preparing a petroleum asphalt-based hard carbon material. The only difference from Example 1 is that AIBN is not added in step two. The rest is exactly the same and will not be described again here. The obtained petroleum asphalt-based hard carbon material is denoted as D-A3.

[0086] Comparative Example 4 This comparative example provides a method for preparing a petroleum pitch-based hard carbon material. The only difference from Example 1 is that a two-step extraction is first performed, followed by a separate air pre-oxidation treatment. The specific steps are as follows: Step 1: Same as Example 1; Step 2: Add a second mixed solvent consisting of toluene and n-heptane in a volume ratio of 3:1 to the first insoluble solid phase. The ratio of the first insoluble solid phase to the second mixed solvent is 1 g: 10 mL. Place the system under a nitrogen atmosphere and extract at 70 °C and 400 r / min for 2.5 h. After the reaction is complete, let it stand for 30 min. Take the upper second soluble extract phase and filter it through a 0.22 μm filter membrane. Then, remove most of the mixed solvent from the filtrate under reduced pressure at 100 °C. Then, raise the temperature to 300 °C and remove residual dissolved and a small amount of volatile components under reduced pressure at -0.09 MPa. After distillation, cool to room temperature, pulverize, and then place in a tube furnace. Pass compressed air through the furnace at a flow rate of 100 mL / min and pre-oxidize at 220 °C for 2 h to obtain the refined petroleum asphalt precursor. Steps three through five are the same as in Example 1.

[0087] The resulting petroleum pitch-based hard carbon material is designated as D-A4.

[0088] Comparative Example 5 This comparative example provides a method for preparing a petroleum asphalt-based hard carbon material. The only difference from Example 1 is that step two is omitted, and the first insoluble solid phase is used directly for the third step. The rest is exactly the same and will not be described again here. The petroleum asphalt-based hard carbon material obtained is denoted as D-A5.

[0089] Comparative Example 6 This comparative example provides a method for preparing a petroleum asphalt-based hard carbon material. The only difference from Example 1 is that step one is omitted. The rest is exactly the same and will not be described again here. The obtained petroleum asphalt-based hard carbon material is denoted as D-A6.

[0090] Performance testing 1. Performance testing of refined petroleum asphalt precursors The softening point, residual carbon content, and molecular weight distribution of the refined petroleum asphalt precursors obtained in step two of Examples 1-4 and Step two of Comparative Examples 2-4 and Comparative Examples 6, the petroleum asphalt raw material in Comparative Example 1, and the first insoluble solid phase obtained in step one of Comparative Example 5 were tested. The test results are shown in Table 1.

[0091] The precursor yield is calculated using the following formula: Precursor yield = (Mass of final refined bitumen precursor / Mass of petroleum bitumen feedstock) × 100% The softening point was tested using the ring and ball method.

[0092] The carbon residue rate was tested using the Concordant carbon residue method at a temperature of 550℃.

[0093] Molecular weight distribution was determined by gel permeation chromatography with tetrahydrofuran as the mobile phase. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and molecular weight distribution index (PDI) were recorded.

[0094] Table 1 As shown in Table 1, compared with the untreated petroleum asphalt raw material D-A1, the HC-A1~HC-A4 series precursors obtained by the two-step graded extraction combined with in-situ pre-crosslinking treatment of this invention showed significantly improved softening points and 550℃ char residue, increased number-average molecular weight, and significantly reduced molecular weight distribution index (PDI). This indicates that low-molecular-weight light components and heavy asphaltene impurities were effectively removed, and the homogeneity and thermal stability of the precursor components were greatly improved. A comparison with single-step extraction and the comparative sample without initiator shows that two-step solvent extraction can accurately extract aromatic and resinous components with appropriate molecular weights. The in-situ pre-crosslinking reaction can further increase the softening point of the precursor and inhibit melt flow during subsequent processing. Compared with single air pre-oxidation treatment (Comparative Example 4), in-situ pre-crosslinking in a homogeneous system is more conducive to narrowing the molecular weight distribution and improving the structural homogeneity of the precursor, providing a good foundation for precise structural control in the subsequent carbonization stage.

[0095] 2. Preparation of negative electrode sheet Using the petroleum asphalt-based hard carbon materials obtained in Examples 1-4 and Comparative Examples 1-6 as active materials, negative electrode sheets were prepared according to the following methods: Hard carbon material, conductive carbon black, and polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 90:5:5, with PVDF pre-dissolved in N-methylpyrrolidone to prepare a binder solution. The hard carbon material and conductive carbon black powder were first mixed evenly, and then the PVDF N-methylpyrrolidone solution was added in portions. The mixture was magnetically stirred at 300 rpm for 4 hours to obtain a uniformly dispersed electrode slurry. The resulting slurry was then uniformly coated onto a 12 μm thick copper foil surface, controlling the active material loading in the electrode to be 1.0–1.2 mg / cm³. 2 The coated electrode sheets were first pre-dried in an oven at 80°C for 2 hours to remove most of the N-methylpyrrolidone, and then dried under vacuum at 120°C for 24 hours. After drying, the electrode sheets were punched into round pieces with a diameter of 12 mm for later use.

[0096] 3. Lithium-ion half-cell assembly and testing 3.1 Assembly of button cell Using the prepared negative electrode as the working electrode, and a lithium metal sheet (14 mm in diameter and 0.6 mm in thickness) as the counter electrode and reference electrode, CR2032 coin cells were assembled in a high-purity argon glove box. The water content and oxygen content in the glove box were below 1 ppm. A 12 μm thick polypropylene membrane was used as the separator; the electrolyte was a 1 mol / L LiPF6 solution, and the solvent was a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a 1:1 volume ratio. 45–50 μL of electrolyte was injected into each coin cell.

[0097] 3.2 Electrochemical performance testing The test voltage window for coin cell half-cells is 0.01~2.00V (vs. Li). + / Li). The charging and discharging processes both adopt constant current mode, and the charging and discharging rates are the same.

[0098] The specific testing procedure is as follows: First, activate the material by constant current charge-discharge cycle at 0.1C for 3 cycles, and record the initial discharge capacity and initial charge capacity; then, conduct rate performance testing, using 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C rates for 5 cycles each. After the high-rate test is completed, return to 0.1C rate for 3 cycles to examine the material's capacity recovery capability; finally, conduct a constant current charge-discharge long-cycle test at 1C rate. After 200 cycles, calculate the capacity retention rate by the ratio of the discharge capacity of the 200th cycle to the discharge capacity of the first cycle of the long-cycle test, and evaluate the material's cycle stability.

[0099] The initial Coulomb efficiency is calculated using the following formula: Initial coulombic efficiency = (Initial charge capacity / Initial discharge capacity) × 100% 10C capacity retention is calculated using the following formula: 10C capacity retention rate = (10C discharge capacity / 0.1C discharge capacity) × 100% Capacity retention over 200 laps is calculated using the following formula: Capacity retention rate after 200 cycles = Discharge capacity at 200 cycles / Initial stable discharge capacity at 1C cycle × 100% 4. Sodium-ion half-cell assembly and testing 4.1 Assembly of button cells The negative electrode sheet prepared above was used as the working electrode, and a sodium metal sheet was used as both the counter electrode and the reference electrode. A CR2032 coin cell was assembled in a high-purity argon glove box with both water and oxygen contents less than 1 ppm. The sodium metal sheet had a diameter of 14 mm and a thickness of 0.6 mm; a glass fiber membrane was used; the electrolyte was a 1 mol / L sodium perchlorate (NaClO4) solution, prepared by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 volume ratio; the electrolyte volume for each coin cell was controlled at 45–50 μL.

[0100] 4.2 Electrochemical performance testing All electrochemical tests were performed at room temperature (25±2℃) with a test voltage window of 0.01–2.50 V (relative to Na / Na). + The charging and discharging mode is constant current charging and discharging.

[0101] The specific testing procedure is as follows: First, activate the material by constant current charge-discharge cycle for 3 cycles at a rate of 0.1C, record the initial discharge capacity and initial charge capacity, and calculate the initial coulombic efficiency; then, conduct rate performance testing, cycling for 5 cycles each at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C in sequence, and after the high-rate test is completed, return to the 0.1C rate for 3 cycles to examine the material's capacity recovery capability; finally, conduct a long-term constant current charge-discharge cycle test at a rate of 1C, calculate the capacity retention rate after 200 cycles, and evaluate the material's cycle stability.

[0102] The calculation methods for the initial coulombic efficiency, 10C rate capacity retention, and 200-cycle capacity retention in this test are consistent with the calculation methods for the aforementioned lithium-ion half-cell.

[0103] The test results are shown in Table 2.

[0104] Table 2 Electrochemical test results show that the HC-A1 sample obtained in Example 1 achieved an initial coulombic efficiency of 93.4% in a lithium-ion half-cell, a capacity retention of 88.2% at 10C rate, and a capacity retention of 91.8% after 200 cycles; in a sodium-ion half-cell, it achieved an initial coulombic efficiency of 87.9%, a capacity retention of 84.5% at 10C rate, and a capacity retention of 92.6% after 200 cycles, demonstrating excellent overall electrochemical performance.

[0105] Compared with Comparative Example 1, which was prepared directly from untreated petroleum asphalt, the electrochemical properties of Example 1 were significantly improved. This indicates that the coexistence of low-molecular-weight components and heavy components in petroleum asphalt raw materials reduces the stability of subsequent thermal processing and ultimately degrades the electrochemical performance of hard carbon materials.

[0106] Compared with Comparative Example 2, which only used single-step extraction and had no pre-crosslinking, Example 1 showed a significant performance improvement, indicating that single-step extraction can only remove some insoluble matter and is difficult to achieve the multiple effects of removing low-molecular-weight soluble components, enriching suitable aromatic / colloidal components, and improving the thermal stability of precursors at the same time.

[0107] Compared with Comparative Example 3, which used two-step extraction but did not perform in-situ pre-crosslinking, Example 1 showed improved initial coulombic efficiency, rate performance and cycle retention. This indicates that relying solely on two-step extraction to optimize the precursor components, the precursor is still prone to agglomeration due to its high fluidity during subsequent mixing, pretreatment and carbonization processes. Therefore, it is necessary to combine it with AIBN in-situ mild pre-crosslinking to ensure structural uniformity.

[0108] Compared with Comparative Example 4, which underwent air pre-oxidation after two-step extraction, Example 1 showed better performance, indicating that homogeneous in-situ mild pre-crosslinking during the extraction stage made it easier to achieve uniform control of the precursor's thermal stability compared to air pre-oxidation in the solid / semi-molten state. Although air pre-oxidation can improve the softening point and char residue, the reaction uniformity is not as good as that of mild pre-crosslinking in the solution state.

[0109] Compared with Comparative Example 5, which only underwent the first step of low-toluene extraction, Example 1 showed a significant performance improvement, indicating that simply removing low-molecular-weight soluble components is insufficient to obtain a precursor suitable for hard carbon preparation. It is necessary to further remove heavy insoluble components through a second step of high-toluene solvent extraction, and enrich aromatic and colloidal components.

[0110] Compared with Comparative Example 6, which omitted the first step of extraction, Example 1 showed better performance, verifying the necessity of the first step of low toluene ratio solvent extraction. If low molecular weight soluble components are not removed in advance and high toluene ratio extraction and pre-crosslinking are carried out directly, the precursor component distribution will still be too wide, which is not conducive to improving the performance of the final hard carbon material.

[0111] In summary, this invention precisely controls the component distribution, softening point, carbon residue, and thermal processing stability of petroleum asphalt from the precursor stage by selective solvent stepwise extraction combined with in-situ mild pre-crosslinking of AIBN. The subsequent coupled multi-step process of inorganic salt template-assisted pore formation, segmented heat treatment, short-time high-temperature pulse treatment, and short-time weak CO2 activation can prepare petroleum asphalt-based hard carbon anode materials with excellent comprehensive electrochemical performance.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a petroleum asphalt-based hard carbon material, characterized in that, Includes the following steps: S1, the petroleum asphalt raw material is mixed with a first mixed solvent for extraction, and solid-liquid separation is performed to obtain a first insoluble solid phase; wherein, the first mixed solvent includes toluene and n-heptane, and the volume content of n-heptane is greater than that of toluene; S2, the first insoluble solid phase, the second mixed solvent and the free radical initiator are mixed and extracted and in-situ pre-crosslinked under inert or low oxygen conditions. After the reaction is completed, the solid and liquid are separated, the second soluble extractable phase is taken, the solvent is removed, and the refined petroleum asphalt precursor is obtained; wherein, the second mixed solvent includes toluene and n-heptane, and the volume content of toluene is greater than that of n-heptane. S3, the refined petroleum asphalt precursor is heated and softened, and water-soluble inorganic salt template agent is added for melt mixing. The resulting mixture is pre-oxidized in an oxygen-containing atmosphere to solidify the refined petroleum asphalt precursor and obtain a pre-treated precursor. S4, the pretreated precursor is mixed with the transition metal organometallic complex and subjected to segmented heat treatment in an inert atmosphere to obtain a carbonized intermediate product. S5, the carbonization intermediate product is subjected to short-time high-temperature pulse treatment in an inert atmosphere. After the treatment, it is subjected to short-time weak activation treatment in an inert carrier gas containing CO2. Then it is cooled in an inert atmosphere, the water-soluble inorganic salt template agent is removed with water, and it is dried to obtain petroleum asphalt-based hard carbon anode material.

2. The method for preparing petroleum pitch-based hard carbon material as described in claim 1, characterized in that, In S1, the volume ratio of toluene to n-heptane in the first mixed solvent is 1:2 to 1:5; and / or In S1, the mass-to-volume ratio of the petroleum asphalt raw material to the first mixed solvent is 1 g: (5~20) mL; and / or In S1, the extraction temperature is 40℃~80℃, and the extraction time is 1h~4h.

3. The method for preparing petroleum pitch-based hard carbon material as described in claim 1, characterized in that, In S2, the volume ratio of toluene to n-heptane in the second mixed solvent is 2:1 to 5:1; and / or In S2, the mass-to-volume ratio of the first insoluble solid phase to the second mixed solvent is 1 g: (5~20) mL; and / or In S2, the extraction and in-situ pre-crosslinking reaction are carried out at a temperature of 60℃~85℃ for a time of 1.5h~4h; and / or In S2, the free radical initiator is an azo free radical initiator or a peroxide free radical initiator, and its addition amount is 0.05% to 0.2% of the mass of the first insoluble solid phase.

4. The method for preparing petroleum pitch-based hard carbon material as described in claim 1, characterized in that, In S3, the water-soluble inorganic salt template agent is at least one of sodium sulfate, sodium chloride, sodium carbonate, or potassium carbonate; and / or In S3, the amount of the water-soluble inorganic salt template agent added is 2% to 8% of the mass of the refined petroleum asphalt precursor; and / or In S3, the melt mixing temperature is 140℃~180℃, and the mixing time is 20min~40min; and / or In S3, the temperature of the pre-oxidation treatment is 200℃~260℃, and the treatment time is 1h~4h.

5. The method for preparing petroleum pitch-based hard carbon material as described in claim 1, characterized in that, In S4, the transition metal organometallic complex includes at least one of ferrocene, cobalt cerocene, or iron acetylacetonate; and / or In S4, the amount of the transition metal organometallic complex added is 0.1% to 0.3% of the mass of the pretreated precursor; and / or In S4, the segmented heat treatment specifically includes the following steps: First, keep warm at 300℃~400℃ for 60min~120min, then keep warm at 380℃~490℃ for 40min~80min, and finally keep warm at 580℃~720℃ for 30min~60min.

6. The method for preparing petroleum pitch-based hard carbon material as described in claim 1, characterized in that, In S5, the temperature of the short-time high-temperature pulse treatment is 900℃~1100℃, the holding time of a single pulse treatment is 30s~70s, the number of pulse treatments is 1~3, and the heating and cooling rates are both not less than 50℃ / min; and / or In S5, the CO2-containing inert carrier gas is a mixture of CO2 and an inert gas, wherein the volume fraction of CO2 is 0.3%~1.0%; and / or In S5, the temperature of the short-time weak activation treatment is 600℃~800℃, and the treatment time is 10min~15min.

7. A petroleum bitumen-based hard carbon material, characterized in that, It is prepared by the method for preparing petroleum asphalt-based hard carbon material according to any one of claims 1 to 6.

8. A negative electrode, characterized in that, Includes the petroleum bitumen-based hard carbon material as described in claim 7.

9. A sodium-ion battery, characterized in that, It includes the petroleum asphalt-based hard carbon material of claim 7 or the negative electrode of claim 8.

10. A lithium-ion battery, characterized in that, It includes the petroleum asphalt-based hard carbon material of claim 7 or the negative electrode of claim 8.

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