Asphalt-based hard carbon negative electrode material, method for regulating closed pore structure thereof and application thereof

Abstract

This invention relates to an asphalt-based hard carbon anode material, a method for controlling its closed-cell structure, and its application, belonging to the technical field of sodium-ion battery anode materials. The steps are as follows: First, asphalt-based raw materials are mixed with a crosslinking agent to obtain a precursor mixture, which is then crosslinked to obtain a crosslinked precursor. Second, the crosslinked precursor is subjected to thermosetting property testing. If it passes the thermosetting property test, proceed to step four; if it fails, the crosslinking process is repeated. Third, the crosslinked precursor is subjected to structural parameter testing and condition screening. Finally, the screened crosslinked precursor is carbonized and post-treated under an inert atmosphere to obtain the asphalt-based hard carbon anode material. The asphalt-based hard carbon anode material is used as an anode material in sodium-ion batteries. This invention can predict and control the closed-cell structure parameters, BET specific surface area, and interlayer spacing of the hard carbon material at the precursor stage, achieving synergistic optimization of plateau capacity, initial coulombic efficiency, and cycle stability.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery anode materials, and relates to an asphalt-based hard carbon anode material, a method for controlling its closed-cell structure, and its application. Specifically, it relates to an asphalt-based hard carbon anode material and its preparation method, and particularly to a second-order gyration radius based on thermosetting asphalt polymers. R g 2 and the second-order mass fractal index P 2 Methods for controlling the closed-cell structure of hard carbon, and the application of pitch-based hard carbon anode materials in sodium-ion batteries. Background Technology

[0002] With the rapid development of large-scale energy storage, electric transportation, and distributed energy systems, sodium-ion batteries, which combine resource advantages with cost advantages, are attracting increasing attention. Compared with lithium resources, sodium resources are more abundant and widely distributed, thus sodium-ion batteries have good application prospects in the field of low-cost energy storage. Among the anode materials of sodium-ion batteries, hard carbon materials are considered to be one of the anode materials with good industrialization prospects due to their high reversible specific capacity, low operating potential, and excellent cycle stability.

[0003] Existing research indicates that the sodium storage capacity of hard carbon materials typically comprises two components: high-potential ramp capacity and low-potential plateau capacity. The plateau capacity is generally closely related to the material's internal closed-cell structure and locally disordered stacking structure, while the ramp capacity is related to factors such as surface defects, open-cell structure, graphite domain spacing, and specific surface area. Therefore, achieving precise and controllable fabrication of the microstructure of hard carbon materials, especially the closed-cell structure, is an important research direction for further improving their sodium storage performance.

[0004] Asphalt, due to its wide availability, high carbon yield, ease of processing, and aromatic molecular structure, is one of the important precursors for preparing hard carbon anode materials. However, most existing methods for preparing asphalt-based hard carbon materials rely on empirical screening, typically improving material properties by adjusting heat treatment temperature, heating rate, or introducing additives. While these methods can control the microstructure of hard carbon materials to some extent, they still have the following shortcomings: asphalt is prone to softening and flowing during heat treatment, which is not conducive to the formation of stable closed-cell structures; during direct pyrolysis, structures with high order and small interlayer spacing of graphite domains are easily formed during uncontrollable liquid-phase carbonization, making it difficult to meet the requirements of sodium-ion battery anode materials for larger interlayer spacing and closed-cell structures; in addition, there is a lack of clear correlation between the type of crosslinking agent, crosslinking treatment conditions, carbonization treatment conditions, and the closed-cell structure of hard carbon, making it difficult for existing modification methods to effectively predict and directionally control the closed-cell structure, plateau capacity, and first coulombic efficiency of hard carbon products at the precursor stage.

[0005] Furthermore, as a typical polydisperse complex mixture, the chemical composition and molecular structure of asphalt are highly dependent on the source, proportion, and processing technology of raw materials. Different batches of raw materials often exhibit significant differences in molecular weight distribution, aromaticity, and functional group content. The intrinsic complexity of asphalt makes it difficult for control strategies developed for specific asphalt to have universality across raw material systems. This also means that the selection of crosslinking agents, the setting of crosslinking processes, and the optimization of carbonization processes have long relied on empirical trial and error, making it difficult to establish a stable correspondence between precursor structure and hard carbon structure and properties.

[0006] Existing technologies for controlling the microstructure of hard carbon mainly focus on modifying asphalt precursors through physical or chemical means. However, these methods largely rely on empirical trial and error and lack quantitative prediction mechanisms for microstructure formation. Chinese invention patent CN121269679A discloses a method for preparing asphalt-based hard carbon materials. Its technical solution involves primary and secondary pre-oxidation treatment of asphalt in an air atmosphere, utilizing oxidative crosslinking reactions to maintain the asphalt in a solid state, thereby suppressing melting and agglomeration during carbonization. While this invention can improve material dispersibility, its core lies in controlling the oxidation temperature and airflow to regulate reaction kinetics, representing a typical process parameter optimization path. Chinese invention patent CN121225566A proposes a method for preparing hypercrosslinked asphalt-based hard carbon materials. Its technical solution employs a mechanochemical method, utilizing the shear force of a ball mill to break asphalt molecular bonds, triggering a Friedel-Crafts alkylation reaction to form a methylene-bridged crosslinking network. This technology uses mechanical force to drive chemical bond recombination, aiming to construct a microporous structure, but it still relies on empirical adjustments to the reaction reagents and mechanical force parameters.

[0007] Therefore, the existing technology still has the following limitations: (1) The research and development model is relatively extensive, mainly adjusting the precursor process through the feedback of the final electrochemical performance, lacking quantitative characterization methods at the molecular aggregation state level, resulting in long research and development cycle and high cost; (2) In the complex process of asphalt being converted into hard carbon, it is impossible to accurately predict the final closed-cell structure formation at the precursor stage, making it difficult to achieve the transformation from experience trial and error to structural design; (3) A stable correspondence between the precursor aggregation structure parameters and the hard carbon closed-cell structure parameters and sodium storage performance has not yet been established, making it difficult to achieve synergistic optimization of platform capacity, first coulombic efficiency and comprehensive sodium storage performance.

[0008] Therefore, there is an urgent need to provide a method for preparing pitch-based hard carbon anode materials that can quantitatively determine the structural state at the precursor stage and further guide the selection of crosslinking agents, optimization of crosslinking treatment conditions and carbonization treatment conditions, so as to achieve predictable, designable and controllable hard carbon closed-cell structure and sodium storage performance. Summary of the Invention

[0009] To address the challenges in the preparation of existing pitch-based hard carbon materials, such as the difficulty in precisely controlling the closed-cell structure, balancing plateau capacity and initial coulombic efficiency, effectively predicting the structure and performance of hard carbon products at the precursor stage, and the lack of quantitative guidance from precursor microstructure parameters to hard carbon closed-cell structure characteristics and sodium storage electrochemical performance, this invention provides a pitch-based hard carbon anode material, a method for controlling its closed-cell structure, and its application. This invention involves crosslinking pitch-based raw materials to transform them into thermosetting pitch polymers. By combining thermosetting property determination and structural parameter determination, the structural state of the crosslinked precursor is screened and controlled. Finally, carbonization treatment is used to obtain a material with the target closed-cell structure parameters. ΔS This invention relates to pitch-based hard carbon anode materials. Through this invention, the closed-pore structure parameters of hard carbon materials can be predicted and controlled during the precursor stage. ΔS BET specific surface area S BET and interlayer spacing d 002 This achieves synergistic optimization of platform capacity, initial coulomb efficiency, and cyclic stability.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for controlling the closed-cell structure of pitch-based hard carbon anode materials, comprising the following steps: The first step involves mixing asphalt-based raw materials with a crosslinking agent to obtain a precursor mixture, wherein the amount of crosslinking agent added is 1-30 wt% of the mass of the asphalt-based raw materials. Furthermore, the asphalt raw material is selected from one or more of petroleum asphalt, coal tar pitch, medium-temperature asphalt, high softening point asphalt, SBS modified asphalt, biomass modified asphalt, or pre-oxidized asphalt; preferably, the softening point of the asphalt-based raw material is 80-250℃.

[0011] Furthermore, the crosslinking agent is selected from one or more of aromatic polycarboxylic acid compounds, aromatic polyamine compounds, multifunctional aromatic bridging compounds, and hyperbranched polymer crosslinking agents. Specifically: The aromatic polycarboxylic acid compound is selected from at least one of pyromellitic acid, isophthalic acid, terephthalic acid, and pyromellitic tetracarboxylic acid; the aromatic polyamine compound is selected from at least one of m-phenylenediamine, p-phenylenediamine, 4,4'-diaminobiphenyl, and 1,5-diaminonaphthalene; the polyfunctional aromatic bridging compound is selected from at least one of melamine and 4-aminophenylamine; the hyperbranched polymer crosslinking agent is selected from at least one of hyperbranched polyester crosslinking agents and modified hyperbranched polyester crosslinking agents; Furthermore, the amount of crosslinking agent added is 5-20 wt% of the mass of the asphalt-based raw material.

[0012] The second step involves placing the precursor mixture obtained in the first step under an oxygen-containing atmosphere for crosslinking treatment to obtain a crosslinked precursor. The purpose of the crosslinking treatment is to convert the asphalt-based raw materials in the precursor mixture into thermosetting asphalt polymers.

[0013] Furthermore, the oxygen-containing atmosphere is air, oxygen, or a mixture of oxygen and an inert gas, preferably air.

[0014] Further, the crosslinking treatment is performed at a temperature of 200-450℃ for 0.5-10h, with a heating rate of 0.5-10℃ / min; preferably, the crosslinking treatment is performed at a temperature of 250-400℃ for 1-6h, with a heating rate of 1-5℃ / min.

[0015] Furthermore, the crosslinking treatment is a two-stage crosslinking process, including: first, pre-crosslinking at 180-220℃ for 0.5-2 hours, and then heat preservation at 230-270℃ for 2-3 hours.

[0016] Step 3: Determine the thermosetting properties of the crosslinked precursor obtained in Step 2; If the crosslinking precursor passes the thermosetting test, proceed to step four; if the crosslinking precursor fails the thermosetting test, return to step one or two, adjust at least one of the following: type of crosslinking agent, amount of crosslinking agent, crosslinking treatment temperature, crosslinking treatment time, or heating rate, and repeat the crosslinking treatment.

[0017] Furthermore, the thermosetting property determination includes the following two conditions, specifically: Condition 1: Differential scanning calorimetry (DSC) was used for testing, and no obvious melting endothermic peak was observed in the range of 100℃-200℃; Condition 2: The sample remains solid and does not soften or flow after being heat-treated at 400℃ for 30 minutes.

[0018] If both conditions 1 and 2 are met, the thermosetting property test is passed; if either condition is not met, the thermosetting property test is failed, and the process parameters need to be adjusted in the second step.

[0019] Step 4: Determine the structural parameters and screen the conditions for crosslinking precursors; Small-angle X-ray scattering (SAXS) was performed on the crosslinked precursors that passed the thermosetting test to obtain the second-order gyrotron radius of the crosslinked precursors. R g 2 Second-order quality fractal index P 2 ; and based on the second-order gyro radius R g 2 Second-order quality fractal index P2 By screening and controlling one or more of the crosslinking agent composition, crosslinking treatment conditions, or carbonization treatment conditions, a crosslinking precursor with target closed-cell structure parameters can be obtained; if R g 2 and P 2 If the target range is not met, return to step one or two, adjust the type and amount of crosslinking agent, and the crosslinking or carbonization conditions, then repeat the crosslinking treatment and thermosetting property determination. The structural parameter determination conditions (the core innovation of this invention) are specifically as follows: When 14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 When the value is ≤2.65, it is determined to be a crosslinking precursor suitable for forming the target closed-cell structure parameters, and quantitative prediction and directional design of the closed-cell structure parameters are carried out. If the requirements are met, proceed to step five. like R g 2 <14.0nm or R g 2 >22.0nm, or P 2 <2.35 or P 2 If the value is greater than 2.65, it is determined to be unsuitable, and it is necessary to return to the first or second step to adjust the process parameters.

[0020] Furthermore, the specific steps for quantitative prediction and directional design of the closed-cell structure parameters in the fourth step are as follows: To achieve precise control over the closed-cell structure of pitch-based hard carbon anode materials, this invention establishes a prediction model for closed-cell structure parameters based on precursor structural characteristics and crosslinking agent molecular properties. This prediction model quantitatively predicts and directionally designs the target closed-cell structure parameters of hard carbon materials by quantifying the mesoscale aggregate structure of the crosslinking precursor and the molecular properties of the crosslinking agent. The target closed-cell structure parameters are predicted by the following empirical formula: ΔS =A+B× R g 2 +C×( P 2 -1.5)+D×Xc+E×Xs; in: ΔS The closed-pore structure parameter characterizes the closed-pore content inside hard carbon materials and is defined as the small-angle X-ray scattering specific surface area. S SAXSBET specific surface area S BET The difference, in m 2 / g, that is ΔS = S SAXS - S BET . S SAXS This represents the total specific surface area in SAXS, calculated using SAXS combined with the Porod invariant method, and is expressed in m². 2 / g; S BET The BET specific surface area is calculated using the BET method through nitrogen adsorption-desorption testing, and the unit is m². 2 / g.

[0021] R g 2 The second-order cyclotron radius of the crosslinked precursor, in nm, is obtained by small-angle X-ray scattering (SAXS) measurements. The second-order cyclotron radius in the low-q region is obtained using Guinier fitting. R g 2 , characterizing the characteristic size of the mesoscale aggregate structure of the precursor.

[0022] P 2 The second-order mass fractal index of the crosslinked precursor was obtained by small-angle X-ray scattering (SAXS) testing, and the second-order mass fractal index was obtained by power-law fitting in the high-q region. P 2 , dimensionless, characterizes the compactness and fractal features of the mesoscale aggregate structure of precursors; Xc is the effective crosslinking characteristic parameter of the crosslinking agent, which is used to characterize the average effective reactive functionality of the crosslinking agent and its contribution to the formation of thermosetting networks. Xs is a structural rigidity characteristic parameter of the crosslinking agent, used to comprehensively characterize the aromaticity, planarity, spatial rigidity, branching degree, and constraint ability of the crosslinking agent molecular skeleton on the formation of the secondary aggregate structure of the precursor. A, B, C, D, and E are fitting coefficients, determined through experimental data calibration. A is the first fitting coefficient, B is the second fitting coefficient, C is the third fitting coefficient, D is the fourth fitting coefficient, and E is the fifth fitting coefficient. In practical applications, fitting coefficients A, B, C, D, and E can be determined through the following steps: (1) preparing a series of crosslinking precursors using different crosslinking agents and process conditions; (2) performing small-angle X-ray scattering tests on the crosslinking precursors to obtain... R g 2 and P2 Value; (3) Perform relevant specific surface area tests on the carbonized hard carbon material and calculate ΔS Value; (4) Based on the least squares method or other regression analysis methods, establish ΔS and R g 2 , P 2 Quantitatively determine the relationship between Xc and Xs to identify the fitting coefficients. Specifically: Xc is used to characterize the average effective reactive functionality of the crosslinking agent and its contribution to the formation of thermosetting networks. Its calculation formula is: Xc = feff / fref. Where feff is the average effective reactive functionality of the crosslinking agent, and fref is the reference functionality. In this invention, fref is uniformly set to a benchmark value of 3. The specific calculation and definition method of feff is as follows: (1) For low molecular weight aromatic polycarboxylic acid compounds or aromatic polyamine compounds, feff is equal to the number of effective reactive groups such as carboxyl or amino groups in a single molecular structure that can participate in the cross-linking reaction at a set cross-linking temperature (for example, pyromellitic acid molecules contain 3 carboxyl groups, feff=3; isophthalic acid molecules contain 2 carboxyl groups, feff=2; terephthalic acid contains 2 carboxyl groups, feff=2).

[0023] (2) For multifunctional aromatic bridging compounds, feff is equal to the number of sites with cross-linking activity or effective bridging functional groups in the molecule.

[0024] (3) For hyperbranched polymer crosslinking agents, feff is equal to the number of effective reactive functional groups carried by the end groups inside or outside each molecule of the hyperbranched polymer crosslinking agent (for example, the hyperbranched polyester crosslinking agent used in this invention has an average end group functionality of 4.5, so feff = 4.5).

[0025] The above calculation and definition methods ensure that crosslinking agents of different types and molecular weight levels have strict consistency and comparability in the parameter system.

[0026] The specific method for determining the Xs parameter is as follows: For multifunctional crosslinking agents, Xs mainly reflects the symmetry, aromatic rigidity, and spatial configuration characteristics of the molecular skeleton; for hyperbranched crosslinking agents, Xs simultaneously reflects the constraint ability of the molecular skeleton rigidity, aromatic structure ratio, and branching degree on the precursor aggregation structure. The value of Xs is determined through molecular structure characteristic analysis combined with experimental calibration, with pyromellitic tricarboxylic acid (BTC) as the benchmark (Xs=1.00), and other crosslinking agents are assigned corresponding values ​​according to their relative constraint ability.

[0027] The parameters A, B, C, D, and E of the closed-cell structure prediction model involved in this invention are 113, 12, 242, 67, and 84, respectively.

[0028] The specific parameter values ​​of representative crosslinking agents in this invention are as follows: isophthalic acid (IPA), feff=2, Xc=0.67, Xs=0.80; terephthalic acid (PTA), feff=2, Xc=0.67, Xs=0.90; trimesolic acid (BTC), feff=3, Xc=1.00, Xs=1.00; hyperbranched polyester crosslinking agent, feff=4.5, Xc=1.50, Xs=1.20. It should be noted that the values ​​listed above are the crosslinking agent parameter values ​​used in specific embodiments of this invention. For hyperbranched crosslinking agents, the applicable ranges for Xc and Xs are 1.20-2.50 and 1.05-1.50, respectively, with preferred ranges of 1.40-2.00 and 1.10-1.35, respectively. Different types of hyperbranched crosslinking agents can have suitable parameter values ​​determined within the above ranges based on their actual molecular structure characteristics and experimental verification results.

[0029] Using the closed-pore structure parameter prediction model, those skilled in the art can determine the required closed-pore structure parameters. ΔS The second-order gyro radius required for reverse design of crosslinking precursors R g 2 Second-order quality fractal index P 2 Furthermore, by selecting crosslinking agents with suitable Xc and Xs parameter values ​​and optimizing crosslinking and carbonization conditions, precise control of the closed-cell structure of hard carbon materials can be achieved. The closed-cell structure parameter prediction model is not only applicable to the specific crosslinking agents in the embodiments of this invention, but can also be extended to other crosslinking agent systems with similar structural characteristics and reactivity, demonstrating the universality and designability of the technical solution of this invention.

[0030] The establishment of the closed-cell structure parameter prediction model transforms the present invention from a traditional trial-and-error model based on experience to a directional design model based on structural parameters. This significantly improves the efficiency and performance stability of asphalt-based hard carbon anode materials, providing a scientific basis and technical support for achieving sodium-ion battery anode materials with high platform capacity, high initial coulombic efficiency, and good cycle stability.

[0031] Step 5: The screened crosslinking precursor is carbonized and post-treated under an inert atmosphere to obtain pitch-based hard carbon anode material.

[0032] Furthermore, the inert atmosphere is nitrogen, argon, or a mixture of both.

[0033] Further, the final temperature of the carbonization treatment is 1000-2000℃, the holding time is 0.5-10h, and the heating rate is 1-20℃ / min; preferably, the final temperature of the carbonization treatment is 1200-1800℃, the holding time is 1-5h, and the heating rate is 2-10℃ / min; more preferably, the final temperature of the carbonization treatment is 1500-1700℃.

[0034] Furthermore, the post-treatment includes washing and drying; the washing stage uses deionized water or dilute acid as the washing medium and continues washing until the pH value of the filtrate is close to neutral; the drying stage has a temperature of 60-120℃ and a drying time of 6-24h.

[0035] A pitch-based hard carbon anode material, prepared using the aforementioned method for controlling the closed-pore structure of pitch-based hard carbon anode materials, is referred to as hard carbon material. The pitch-based hard carbon anode material consists of amorphous carbon particles with irregular powder or near-spherical morphology. The particle surface is relatively dense, and the interior contains abundant nanoscale closed-pore structures. It possesses at least one of the following structural parameters: The total specific surface area (SSAXS) of the inner and outer pore boundaries of the representative material was obtained by small-angle X-ray scattering combined with the Porod invariant method. The specific surface area of ​​open pores and the contribution of surface roughness to the open pores of a representative material, calculated using the BET method through nitrogen adsorption-desorption testing, is known as the BET specific surface area (SBET). S BET 1-20m 2 / g, preferably 2-10m 2 / g; Define closed-cell structure parameters ΔS The difference between the two (i.e.) ΔS = S SAXS - S BET ), closed-cell structure parameters ΔS 800-1200m 2 / g, preferably 1000-1150m 2 / g.

[0036] Interlayer spacing of pitch-based hard carbon anode materials d 002 The wavelength is 0.36-0.40 nm, preferably 0.366-0.39 nm. Specifically, the interlayer spacing... d 002 It was obtained through X-ray diffraction (XRD) testing and calculated based on the Bragg equation. d 002Interlayer spacing. The interlayer spacing parameter reflects the average spacing between graphite lamellars of locally disordered graphite domains within hard carbon materials. A larger interlayer spacing is beneficial for the reversible insertion and extraction of sodium ions.

[0037] Raman characteristic parameters I D / I G The ratio is 1.0-1.5, preferably 1.2-1.4; specifically: the ratio of the intensity of the D peak to the G peak obtained by Raman spectroscopy, dimensionless.

[0038] An application of an asphalt-based hard carbon anode material, specifically its application in the anode of a sodium-ion battery. Specifically, the asphalt-based hard carbon anode material is used as the active material to prepare an anode sheet, which is then assembled with a positive electrode sheet, electrolyte, and separator to form a sodium-ion battery. In sodium-ion half-cell testing, with 0.1V as the boundary between the plateau region and the slope region, the battery exhibits at least one of the following electrochemical properties: First discharge plateau capacity Qp Greater than 220mAh / g, preferably 230-310mAh / g; specifically: discharge platform capacity Qp This refers to the specific capacity corresponding to the portion of the initial discharge curve where the voltage is below 0.1V in a sodium-ion half-cell test.

[0039] First discharge ramp capacity Qs Greater than 90mAh / g, preferably 90~160mAh / g; specifically: discharge slope capacity Qs This refers to the specific capacity corresponding to the portion of the initial discharge curve where the voltage is higher than 0.1V in a sodium-ion half-cell test.

[0040] The initial coulomb efficiency is greater than 85%, preferably 85-92%.

[0041] After 200 cycles, the capacity retention rate is not less than 85%, preferably 85-95%.

[0042] Principle analysis of this invention: (1) This invention combines crosslinking treatment, thermosetting property determination and structural parameter determination to screen and regulate the structural state of the crosslinking precursor, thereby enabling the carbonized pitch-based hard carbon anode material to have a closed-cell structure that is conducive to sodium storage on the platform, a suitable BET specific surface area, and an interlayer spacing that is conducive to the reversible insertion and extraction of sodium ions. d 002 Furthermore, it enhances the material's reversible capacity, initial coulombic efficiency, and plateau capacity contribution.

[0043] (2) The cross-linked precursor of the present invention, after cross-linking treatment and passing the thermosetting property test, is less prone to melting, flow and structural collapse during subsequent carbonization treatment, which is beneficial to maintaining the structural basis required to form the target carbon skeleton; furthermore, the present invention improves the second-order gyroscope radius. R g 2 Second-order quality fractal index P 2 By determining structural parameters, crosslinking precursors with more suitable secondary structural unit sizes and aggregation methods can be selected. Crosslinking precursors that meet the structural parameter conditions set in this invention are more conducive to forming the target closed-cell structure during carbonization and can control the carbon layer stacking state, thereby resulting in hard carbon materials with higher closed-cell structure parameters. ΔS Lower or suitable BET specific surface area S BET And interlayer spacing that is conducive to sodium storage d 002 .

[0044] (3) The pitch-based hard carbon anode material prepared by the present invention can improve the low potential plateau capacity through the closed-pore structure, reduce electrolyte decomposition and interfacial side reactions through the appropriate BET specific surface area, and improve the reversible insertion and extraction behavior of sodium ions through the appropriate interlayer spacing, thereby achieving synergistic optimization of plateau capacity, first coulombic efficiency and cycle stability.

[0045] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention realizes the structural design and screening of the precursor stage. The second-order cyclotron radius is measured by introducing small-angle X-ray scattering. R g 2 Second-order quality fractal index P 2 This allows for the prediction of the closed-pore structure and sodium storage performance of hard carbon products at the precursor stage, which helps to shorten the R&D cycle and improve R&D efficiency.

[0046] (2) The present invention can stably construct a closed-cell structure that is conducive to sodium storage on the platform. The cross-linking treatment under an oxygen-containing atmosphere transforms the asphalt-based raw material into a thermosetting asphalt polymer. Combined with the thermosetting determination, it can effectively suppress the softening and flow phenomenon of asphalt during the high-temperature carbonization process, providing support for the stable construction of the closed-cell structure.

[0047] (3) This invention can balance platform capacity and initial coulombic efficiency. By screening and controlling the structural state of the crosslinking precursor, the resulting hard carbon material can improve the closed-cell structure parameters. ΔSWhile increasing platform capacity, maintain a low or appropriate BET specific surface area, thereby reducing the first irreversible capacity loss caused by side reactions and improving the first coulombic efficiency.

[0048] (4) This invention establishes a quantifiable structure-performance correlation. This is achieved by constructing crosslinked precursor structural parameters and closed-cell structural parameters. ΔS The correlation between sodium storage performance and other properties provides quantitative guidance for subsequent process optimization, raw material selection, and stable product preparation.

[0049] (5) The process of this invention is simple and suitable for scale-up. The asphalt-based raw materials and crosslinking agents used are widely available. The steps of crosslinking treatment, thermosetting property determination, structural parameter determination and carbonization treatment are clear. The process adjustment can be guided by the precursor characterization results, which is conducive to achieving stable batch control and large-scale preparation of products.

[0050] (6) The pitch-based hard carbon anode material obtained by the present invention has excellent comprehensive electrochemical performance, and can exhibit high plateau capacity, high initial coulombic efficiency and good cycle stability, and has good practical application prospects. Attached Figure Description

[0051] Figure 1 This is a schematic flowchart of the preparation method of the asphalt-based hard carbon anode material of the present invention.

[0052] Figure 2 This is a small-angle X-ray scattering curve of the crosslinked precursor obtained in Example 1.

[0053] Figure 3 The second-order gyroradius of the crosslinking precursor R g 2 Second-order mass fractal index P 2 Closed-cell structure parameters of hard carbon materials ΔS The relationship diagram.

[0054] Figure 4 The SAXS total specific surface area of ​​the hard carbon material obtained in Example 1 is... S SAXS BET specific surface area S BET and target closed-cell structure parameters ΔS Comparison chart.

[0055] Figure 5 The image shows the X-ray diffraction pattern of the hard carbon material obtained in Example 1.

[0056] Figure 6 The image shows the Raman spectrum of the hard carbon material obtained in Example 1.

[0057] Figure 7 For the platform capacity of Comparative Example 1 and Example 1 Qp With closed-cell structure parameters ΔS The fitting relationship diagram.

[0058] Figure 8 The graph shows the first charge-discharge curve of the hard carbon material obtained in Example 1 at a current density of 20 mA / g.

[0059] Figure 9 The graph shows the cycling performance of the hard carbon material obtained in Example 1 after 200 cycles. Detailed Implementation

[0060] The present invention will be further described below with reference to specific implementation examples.

[0061] Example 1 (Verification and Prediction Model for Low Crosslinking Agent Dosage) A method for controlling the closed-cell structure of pitch-based hard carbon anode materials, wherein the pitch-based hard carbon anode materials are prepared using the present invention, and the method flow is as follows: Figure 1 As shown, it includes the following steps: The first step is to mix the asphalt-based raw material with the crosslinking agent to obtain a precursor mixture; In this embodiment, the asphalt-based raw material is selected as petroleum asphalt with a softening point of 250℃ (100.0g was weighed, with an average molecular weight of approximately 760 and an ash content of less than 0.5%). The asphalt-based raw material was added to a 250mL three-necked flask, along with 200.0mL of tetrahydrofuran. The mixture was stirred and dissolved in an oil bath at 50℃ for 30 minutes to obtain a homogeneous asphalt solution. The crosslinking agent was selected as trimesic acid (BTC). The amount of crosslinking agent added was 5.0wt% of the mass of the asphalt-based raw material (5.0g was weighed). Stirring was continued at 50℃ for 60 minutes to ensure uniform dispersion of the crosslinking agent in the system. The resulting mixture was transferred to a rotary evaporator and the solvent was removed at 50℃ and 0.08MPa. The resulting solid was dried in a vacuum drying oven at 80℃ for 8 hours for later use.

[0062] The second step involves placing the precursor mixture obtained in the first step under an oxygen-containing atmosphere for crosslinking treatment to obtain a crosslinked precursor. The purpose of the crosslinking treatment is to convert the asphalt-based raw material in the precursor mixture into a thermosetting asphalt polymer.

[0063] In this embodiment, the oxygen-containing atmosphere is air (flow rate controlled at 100 mL / min). The crosslinking treatment is a two-stage crosslinking process, specifically: the mixture of asphalt and crosslinking agent trimesic acid obtained in the first step is placed in a quartz boat and then placed in a tube furnace. Pre-crosslinking is first performed at 200°C for 1.0 h (heating rate 2°C / min), followed by further heating to 250°C and holding for 3.0 h. After the holding period, the furnace is allowed to cool naturally to room temperature to obtain the crosslinking precursor P-1.

[0064] Step 3: Determine the thermosetting properties of the crosslinked precursor obtained in Step 2; If the crosslinking precursor passes the thermosetting property test, proceed to step four; if the crosslinking precursor fails the thermosetting property test, return to step one or two, adjust at least one of the following: crosslinking agent type, crosslinking agent dosage, crosslinking treatment temperature, crosslinking treatment time, or heating rate, and repeat the crosslinking treatment. The thermosetting property test includes the following two conditions, specifically: Condition 1: Differential scanning calorimetry (DSC) was used for testing, and no obvious melting endothermic peak was observed in the range of 100℃-200℃; Condition 2: The sample remains solid and does not soften or flow after being heat-treated at 400℃ for 30 minutes.

[0065] If both conditions 1 and 2 are met, the thermosetting property test is passed; if either condition is not met, the thermosetting property test is failed, and the process parameters need to be adjusted in the second step.

[0066] In this embodiment, the crosslinking precursor P-1 was tested. Its DSC curve showed no obvious melting endothermic peak in the 100℃-200℃ range, and remained solid after treatment at 400℃ for 30 minutes, without any softening or flow phenomena. Both conditions 1 and 2 were met, and based on the thermosetting property determination, it was identified as a thermosetting asphalt polymer.

[0067] Step 4: Determine the structural parameters and screen the conditions for crosslinking precursors; Small-angle X-ray scattering (SAXS) was performed on the crosslinked precursors that passed the thermosetting test to obtain the second-order gyrotron radius of the crosslinked precursors. R g 2 Second-order quality fractal index P 2 ; and based on the second-order gyro radius R g 2 Second-order quality fractal index P 2 By screening and controlling one or more of the crosslinking agent composition, crosslinking treatment conditions, or carbonization treatment conditions, the desired closed-cell structure parameters can be obtained. ΔS Crosslinked precursors; if R g 2 and P 2 If the structural parameter determination conditions are not met, return to step one or step two, adjust the type of crosslinking agent, the amount of crosslinking agent, the crosslinking treatment conditions or the carbonization treatment conditions, and repeat the crosslinking treatment and thermosetting property determination.

[0068] In this embodiment, Figure 2Small-angle X-ray scattering (SAXS) curves of the crosslinked precursor are shown. The test conditions were CuKα radiation at a wavelength of 0.15418 nm and a scattering vector q range of 0.1 nm. -1 -5.0nm -1 , Figure 2 The second-order gyroscope radius was obtained by Guinier fitting in the low-to-medium q region. R g 2 The second-order mass fractal index was obtained by power-law fitting in the high q region. P 2 . Figure 3 The second-order gyroradius of the crosslinking precursor R g 2 Second-order mass fractal index P 2 Closed-cell structure parameters of hard carbon materials ΔS The relationship diagram.

[0069] Test results show that the crosslinking precursor P-1 in this embodiment... R g 2 =4.21nm, P 2 =1.42. The specific condition for determining the structural parameters is: when 14.0 nm ≤ R g 2 ≤22.0nm and 2.35≤ P 2 When the value is ≤2.65, it is determined to be a suitable parameter for forming the required closed-cell structure. ΔS Crosslinked precursors.

[0070] Due to this embodiment R g 2 <14.0nm and P 2 The value is less than 2.35, failing to meet the structural parameter determination criteria. Analysis suggests that the low amount of crosslinking agent prevented the precursor from forming a sufficiently dense and appropriately sized aggregate structure, thus rendering it unsuitable. In this verification experiment, to compare the control effect, predictions will still be made before proceeding to the next carbonization step.

[0071] In this embodiment, the target closed-hole structure parameters ΔS The specific steps for quantitative prediction and directional design are as follows: The target closed-cell structure parameters are predicted by the following empirical formulas: ΔS =A+B× R g 2 +C×( P 2-1.5)+D×Xc+E×Xs.

[0072] The meanings of each parameter are as follows: ΔS The target closed-cell structure parameter characterizes the closed-cell content inside hard carbon materials. R g 2 The second-order gyroscopic radius of the crosslinked precursor is 4.21 nm in this embodiment. P 2 Xc is the second-order mass fractal index of the crosslinking precursor, which is 1.42 in this embodiment. Xc is the effective crosslinking characteristic parameter of the crosslinking agent. In this embodiment, the average effective reactive functionality feff of BTC is 3, and the reference functionality fref is 3, so Xc = 1.00. Xs is the structural rigidity characteristic parameter of the crosslinking agent. Based on BTC, Xs = 1.00. The fitting coefficients A, B, C, D, and E (first to fifth fitting coefficients) were determined by calibration using experimental data. The determination method was as follows: (1) preparing a series of precursors; (2) testing. R g 2 and P 2 (3) Testing the hard carbon after carbonization ΔS (4) Establish quantitative relationships through least squares regression analysis.

[0073] Step 5: The screened crosslinking precursor is carbonized and post-treated under an inert atmosphere to obtain pitch-based hard carbon anode material.

[0074] In this embodiment, P-1 was placed in a graphite crucible and then placed in a high-temperature furnace for carbonization under the protection of high-purity argon (flow rate 50 mL / min). The carbonization procedure was as follows: the temperature was increased to 1600℃ at a heating rate of 3℃ / min, held at that temperature for 2.0 h, and then allowed to cool naturally with the furnace. The resulting product was continuously washed with deionized water until the pH of the filtrate was neutral, and then vacuum dried at 80℃ for 12 h to obtain the hard carbon material HC-1.

[0075] A pitch-based hard carbon anode material was prepared by the above-mentioned method for controlling the closed-cell structure of pitch-based hard carbon anode materials.

[0076] The asphalt-based hard carbon anode material HC-1 is an amorphous carbon material particle with an irregular powder particle morphology. The particle surface is relatively dense, and a certain number of nanoscale closed-pore structures are developed inside.

[0077] The structure of HC-1 was characterized, and the results are as follows: First, the total SAXS specific surface area, which reflects the overall internal and external pore boundaries of the material, was obtained by small-angle X-ray scattering combined with the Porod invariant method. S SAXS It is 682.0m2 / g; secondly, the BET specific surface area, reflecting the contribution of open pores and surface roughness of the material, was calculated using the BET method through nitrogen adsorption-desorption testing. S BET It is 8.5m 2 / g; Finally, the parameters of the closed-cell structure were calculated. ΔS (Right now S SAXS - S BET The value is 673.5m. 2 / g. Figure 4 A direct comparison of the three parameters above reveals that, due to the precursor not meeting the predicted range, its closed-pore development is insufficient. The interlayer spacing of HC-1... d 002 The value, obtained through XRD testing and calculation based on the Bragg equation, is 0.366 nm, reflecting the average interlamellar spacing of locally disordered graphite domains within hard carbon. Raman characteristic parameters of HC-1. I D / I G The ratio of 1.20 is the intensity ratio of the D peak to the G peak obtained through Raman spectroscopy. The X-ray diffraction pattern of the hard carbon material obtained in Example 1 is shown below. Figure 5 As shown, the Raman spectrum is as follows Figure 6 As shown.

[0078] An application of a pitch-based hard carbon anode material, specifically its use in sodium-ion battery anodes. Specifically, HC-1 is used as the active material to prepare the anode sheet, which is then assembled with a sodium metal counter electrode to form a half-cell. (Platform capacity) Qp With closed-cell structure parameters ΔS The fitting relationship diagram is as follows Figure 7 As shown. Tests were conducted at a current density of 20 mA / g, with 0.1 V as the boundary between the plateau and slope regions. The electrochemical performance is as follows: The initial charge-discharge curves are shown in the figure. Figure 8 As shown, the capacity of the initial discharge platform Qp 178mAh / g; initial discharge ramp capacity Qs The initial discharge capacity was 112 mAh / g; the initial total discharge capacity was 290 mAh / g; and the initial coulombic efficiency was 81.3%. After 200 cycles, the capacity retention was 82.6%. Figure 9 As shown.

[0079] Example 2 (Verification and Prediction Model for Low Crosslinking Agent Dosage) A method for controlling the closed-cell structure of pitch-based hard carbon anode materials, comprising the following steps: The first step is to mix the asphalt-based raw material with the crosslinking agent to obtain a precursor mixture; In this embodiment, the asphalt-based raw material is selected from petroleum asphalt with a softening point of 250℃ (100.0g), and the specific specifications and pretreatment method are the same as in Example 1. It is dissolved in 200.0mL of tetrahydrofuran under the same dissolution conditions as in Example 1.

[0080] The crosslinking agent was selected from trimesolic acid (BTC). In this embodiment, by adjusting the process parameters, the amount of crosslinking agent added was increased to 12.0 wt% of the mass of the asphalt-based raw material (i.e., 12.0 g of BTC was weighed). The subsequent mixing, stirring, solvent evaporation, and vacuum drying conditions were the same as in Example 1, resulting in a solid precursor mixture for later use.

[0081] The second step involves placing the precursor mixture obtained in the first step under an oxygen-containing atmosphere for cross-linking treatment to obtain a cross-linked precursor. In this embodiment, the oxygen-containing atmosphere is compressed air, with a flow rate controlled at 50 mL / min. The crosslinking treatment adopts the same two-stage crosslinking process as in Example 1: first, pre-crosslinking is performed at 200°C for 1.0 h at a heating rate of 2°C / min; then, the temperature is further increased to 250°C at 2°C / min and held for 3.0 h for main crosslinking. After cooling, the crosslinking precursor P-2 is obtained.

[0082] Step 3: Determine the thermosetting properties of the crosslinked precursor obtained in Step 2; In this embodiment, the operation procedure, testing instrument conditions, and judgment criteria for thermosetting property determination are the same as in Embodiment 1.

[0083] The following criteria were used to determine the suitability of P-2: its DSC curve showed no obvious melting endothermic peak in the 100℃-200℃ range; after treatment at 400℃ for 30 min, the sample remained stable in a solid state without softening or flow. Since both conditions 1 and 2 were met, P-2 was determined to be a thermosetting asphalt polymer, and the determination was passed.

[0084] Step 4: Determine the structural parameters and screen the conditions for crosslinking precursors; In this embodiment, the small-angle X-ray scattering test method and data fitting processing method are the same as in Embodiment 1.

[0085] Test results show that the second-stage gyro radius of P-2 R g 2 =13.8nm, second-order mass fractal index P 2 =2.30.

[0086] Compared to Example 1, increasing the amount of crosslinking agent makes R g2 and P 2 Both values ​​increased, and the structural parameters improved, but they are still slightly below the lower limit of the target decision interval of 14.0 nm and 2.35 nm. Therefore, they are determined not to meet the optimal structural parameter determination conditions and belong to the marginal state.

[0087] In closed-cell structure parameters ΔS In the quantitative prediction, since the crosslinking agent is also BTC, its characteristic parameters Xc=1.00 and Xs=1.00 (the definition and value standard are consistent with Example 1). The model predicts that its closed-pore development after carbonization will be better than HC-1, but still does not reach the expected excellent level.

[0088] Step 5: The crosslinking precursor is carbonized and post-treated under an inert atmosphere to obtain pitch-based hard carbon anode material.

[0089] In this embodiment, the carbonization process and post-treatment (washing and drying) conditions are completely consistent with those in Example 1: under the protection of high-purity argon, the temperature is increased to 1600℃ at 3℃ / min and held for 2.0h. The resulting product is washed with water until neutral and then vacuum dried at 80℃ for 12h to obtain hard carbon material HC-2.

[0090] A pitch-based hard carbon anode material HC-2 was prepared using the method described above.

[0091] The asphalt-based hard carbon anode material HC-2 is an irregular powder particle with a nanoscale closed-pore structure.

[0092] The structure of HC-2 was characterized using the same testing methods and parameter definitions as in Example 1. The results are as follows: SAXS total specific surface area S SAXS It is 895.0m 2 / g;BET specific surface area S BET It is 5.8m 2 / g; Closed-cell structure parameters ΔS ( S SAXS - S BET Increased to 889.2m 2 / g. Interlayer spacing of HC-2 d 002 The value is 0.369 nm, reflecting the average interlamellar spacing of the locally disordered graphite domains within the structure. Raman characteristic parameters of HC-2. I D / I G The ratio is 1.25.

[0093] Application of an asphalt-based hard carbon anode material. The battery assembly method and charge / discharge test conditions are consistent with Example 1. The electrochemical performance of HC-2 is as follows: initial discharge plateau capacity... Qp 235mAh / g; initial discharge ramp capacity [[ID=5′6]]Qs The initial discharge capacity was 101 mAh / g; the initial discharge total capacity was 336 mAh / g; and the initial coulombic efficiency was 84.2%. After 200 cycles, the capacity retention was 85.3%.

[0094] Compared with Example 1, it can be seen that although Example 2 still did not fully enter the predicted target range, but with R g 2 and P 2 By gradually approaching the target range, the closed-cell structure parameters of the obtained hard carbon material were determined. ΔS Significantly increased platform capacity Qp It also shows a synchronous improvement trend, which fully verifies the positive correlation between precursor structural parameters and final performance.

[0095] Example 3 (in contrast to Examples 1 and 2, it satisfies the prediction model) A method for controlling the closed-cell structure of pitch-based hard carbon anode materials, comprising the following steps: The first step is to mix the asphalt-based raw material with the crosslinking agent to obtain a precursor mixture; In this embodiment, the asphalt-based raw material is selected from petroleum asphalt (100.0g) with a softening point of 250℃, and the specifications and pretreatment method are the same as in Example 1. The crosslinking agent is selected from trimesic acid (BTC). To further control the structure, the amount of crosslinking agent added in this embodiment is increased to 20.0wt% of the mass of the asphalt-based raw material (20.0g BTC is weighed). The remaining steps include mixing, stirring, solvent evaporation, and vacuum drying. A method for controlling the closed-cell structure of asphalt-based hard carbon anode material, using this invention to prepare asphalt-based hard carbon anode material, specifically includes the following steps: The second step involves placing the precursor mixture obtained in the first step under an oxygen-containing atmosphere for cross-linking treatment to obtain a cross-linked precursor. In this embodiment, the oxygen-containing atmosphere is compressed air (100 mL / min). The crosslinking treatment adopts a two-stage crosslinking process, specifically: pre-crosslinking is performed by heating to 200°C at 2°C / min and holding for 1.0 h; then, the temperature is further increased to 260°C at 2°C / min and held for 3.0 h for main crosslinking. After cooling, the crosslinking precursor P-3 is obtained.

[0096] Step 3: Determine the thermosetting properties of the crosslinked precursor obtained in Step 2; In this embodiment, the thermosetting property determination procedure was the same as in Example 1. The DSC curve of P-3 showed no obvious melting endothermic peak in the 100℃-200℃ range; after treatment at 400℃ for 30 minutes, it maintained solid powder characteristics and did not flow. It was determined to be a thermosetting asphalt polymer, and the determination was passed.

[0097] Step 4: Determine the structural parameters and screen the conditions for crosslinking precursors; In this embodiment, the small-angle X-ray scattering test method is the same as in Example 1.

[0098] Test results show that the second-order gyro radius of P-3 R g 2 =15.6nm, second-order mass fractal index P 2 =2.45. Based on the set judgment condition (14.0nm ≤ R g 2 ≤22.0nm and 2.35≤ P 2 ≤2.65), in this embodiment R g 2 and P 2 All samples successfully entered the target prediction range. This indicates that their aggregated structure has great potential to form well-developed closed pores, and they are judged to be suitable for forming high closed-pore structure parameters. ΔS Crosslinked precursors. In ΔS In the quantitative prediction, the characteristic parameters of the crosslinking agent remained unchanged: effective reactive functional group number feff=3, reference functionality fref=3, Xc=1.00, Xs=1.00. Because... R g 2 and P 2 The carbonization process significantly improves the structure and enters the target range, and the model predicts that it will achieve an excellent closed-pore structure.

[0099] Step 5: The crosslinking precursor is carbonized and post-treated under an inert atmosphere to obtain pitch-based hard carbon anode material.

[0100] The carbonization process and post-processing conditions were completely consistent with those in Example 1 (argon protection, heat treatment at 1600℃ for 2.0h), resulting in hard carbon material HC-3.

[0101] The asphalt-based hard carbon anode material HC-3 is an amorphous carbon material particle with an irregular powder particle morphology or a near-spherical morphology. The particle surface is dense, and its interior has an extremely rich nanoscale closed-pore structure.

[0102] Structural characterization of HC-3 was performed (test logic consistent with Example 1), and the results are as follows: SAXS total specific surface area S SAXS It is 1108.0m 2 / g;BET specific surface area S BET It is 3.6m 2 / g; Closed-cell structure parameters ΔS (Right now S SAXS - S BET ) Reached 1104.4m 2 / g; Interlayer spacing of HC-3 d 002 0.372 nm (reflecting the average interlaminar spacing of disordered graphite domains); Raman characteristic parameters I D / I G The ratio is 1.31.

[0103] HC-3 was assembled into a sodium-ion half-cell (test conditions were the same as in Example 1), and the electrochemical performance is as follows: initial discharge plateau capacity. Qp 294mAh / g; initial discharge ramp capacity The initial capacity was 103 mAh / g (total initial capacity was 397 mAh / g); the initial coulombic efficiency was 88.7%; and the capacity retention after 200 cycles was 89.2%.

[0104] Analysis of the optimization effects of Examples 1 to 3: Through a continuous optimization process from Example 1 to Example 2 to Example 3, the effectiveness of prediction and control based on precursor structural parameters was clearly demonstrated. When the amount of crosslinking agent was gradually increased from 5.0 wt% to 20.0 wt%, and the crosslinking temperature was appropriately increased, the precursor... R g 2 From 12.6nm to 15.6nm, P 2 The value increased from 2.15 to 2.45, successfully entering the predicted range for the target closed-cell structure parameters. Correspondingly, the carbonized hard carbon material... Qs From 673.5m 2 / g increased significantly to 1104.4m 2 / g, platform capacity ΔS The mAh / g capacity increased from 178 mAh / g to 294 mAh / g, and the coulombic efficiency improved from 81.3% to 88.7% for the first time. This fully demonstrates that precursor parameters can effectively guide process optimization and achieve precise performance leaps.

[0105] Example 4 (Screening of crosslinking agent types, optimized case that meets the pre-judgment conditions) The first step is to mix the asphalt-based raw material with the crosslinking agent to obtain a precursor mixture; The asphalt-based raw material (100.0 g of petroleum asphalt dissolved in tetrahydrofuran) was the same as in Example 1. The crosslinking agent was changed to a hyperbranched polyester crosslinking agent (molecular weight approximately 3500). The addition amount was 20.0 wt% (20.0 g). Stirring was continued at 50°C for 90 min, and the subsequent drying steps were the same as in Example 1.

[0106] The second step involves placing the precursor mixture obtained in the first step under an oxygen-containing atmosphere for cross-linking treatment. The oxygen-containing atmosphere was air (100 mL / min). The crosslinking program was adjusted as follows: heat to 195℃ at 1.5℃ / min and hold for 1.5 h; then heat to 245℃ at 1.5℃ / min and hold for 3.0 h. Cooling yielded the crosslinking precursor P-4.

[0107] Step 3: Determine the thermosetting properties of the crosslinking precursor; After testing, P-4 passed the thermosetting determination and was identified as a thermosetting bitumen polymer.

[0108] Step 4: Determine the structural parameters and screen the conditions for crosslinking precursors; Small-angle X-ray scattering (SAXS) tests showed that P-4's R g 2 =18.5nm, P 2 =2.58.

[0109] Compared to Example 3, hyperbranched polyester can more effectively constrain pitch molecular chains. The parameters perfectly fall within the target prediction range (14.0 nm ≤ R g 2 ≤22.0nm and 2.35≤ P 2 (≤2.65), which is considered an excellent crosslinking precursor.

[0110] exist Qp In the prediction model: the average number of effective functional groups at the end groups of the hyperbranched polyester crosslinking agent is feff=4.5, fref=3, and the effective crosslinking characteristic parameter Xc=1.50; it has a highly rigid aromatic skeleton with a structural rigidity characteristic parameter Xs=1.20. The model predicts that it will obtain extremely high closed-cell structure parameters after carbonization.

[0111] Step 5: Carbonization and post-treatment.

[0112] The carbonization and post-treatment conditions were exactly the same as in Example 1, yielding the hard carbon material HC-4. The pitch-based hard carbon anode material HC-4 possesses an extremely rich internal nanoscale closed-pore structure. Its structural parameters are as follows: S SAXS It is 1125.0m 2 / g; S BET It is 3.4m 2 / g; Closed-cell structure parameters ΔS It is 1121.6m 2 / g; interlayer spacing d 002 0.373 nm; Raman characteristic parameters I D / I G It is 1.33.

[0113] After assembling the battery (test conditions are the same as in Example 1), the electrochemical performance is as follows: initial discharge plateau capacity ΔS Reaching 301mAh / g; initial discharge ramp capacity Qp It has a capacity of 105 mAh / g (total capacity 406 mAh / g); the initial coulombic efficiency is as high as 89.1%. The capacity retention rate after 200 cycles is 89.5%.

[0114] Example 5 (synergistic crosslinking of pyromellitic acid and isophthalic acid) A method for controlling the closed-cell structure of pitch-based hard carbon anode materials, comprising the following steps: The first step is to mix the asphalt-based raw material with the crosslinking agent to obtain a precursor mixture; In this embodiment, the asphalt-based raw material was selected from petroleum asphalt (100.0g) with a softening point of 250℃, and the specific specifications and pretreatment dissolution method were the same as in Example 1. To investigate the synergistic effect of the composite crosslinking agent, 10.0g of trimesic acid (BTC) and 8.0g of isophthalic acid (IPA) were weighed as mixed crosslinking agents and added to the above asphalt solution. The subsequent mixing, stirring, solvent evaporation, and vacuum drying conditions were the same as in Example 1, resulting in a solid precursor mixture.

[0115] The second step involves placing the precursor mixture obtained in the first step under an oxygen-containing atmosphere for cross-linking treatment to obtain a cross-linked precursor. In this embodiment, the oxygen-containing atmosphere is air (flow rate controlled at 100 mL / min). The crosslinking treatment adopts the same two-stage crosslinking process as in Example 1: first, pre-crosslinking is performed at 200°C for 1.0 h (heating rate 2°C / min), then the temperature is further increased to 250°C at a heating rate of 2°C / min, and held at this temperature for 3.0 h for main crosslinking. After cooling, the crosslinking precursor P-5 is obtained.

[0116] Step 3: Determine the thermosetting properties of the crosslinked precursor obtained in Step 2; In this embodiment, the testing procedures and standards for determining thermosetting properties were consistent with those in Example 1. The DSC curve of the crosslinking precursor P-5 showed no obvious melting endothermic peak in the 100℃-200℃ range, and after treatment at 400℃ for 30 min, it still maintained solid powder characteristics without softening or flow. Therefore, P-5 was determined to be a thermosetting asphalt polymer, and the determination was passed.

[0117] Step 4: Determine the structural parameters and screen the conditions for crosslinking precursors; In this embodiment, the small-angle X-ray scattering test method is the same as in Example 1.

[0118] Test results show that the second-order gyroscope radius of P-5 R g 2 =17.9nm, second-order mass fractal index P 2 =2.62.

[0119] According to the determination criteria, this embodiment R g 2 and P 2 Falling into the target prediction range (14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 (≤2.65), which is considered a suitable parameter for forming the target closed-cell structure. Qs Crosslinked precursors.

[0120] Target closed-cell structure parameters ΔS The quantitative prediction involved the synergistic effect of two crosslinking agents: BTC (effective reactive functional group number feff=3, fref=3, calculated Xc=1.00, Xs=1.00) and IPA (effective reactive functional group number feff=2, fref=3, calculated Xc=0.67, Xs=0.80). Model predictions indicate that the synergistic effect of polycarboxylic acids endows suitable mesoscale aggregate structures, which, upon carbonization, will form extremely high closed-pore parameters.

[0121] Step 5: The screened crosslinking precursor is carbonized and post-treated under an inert atmosphere to obtain pitch-based hard carbon anode material.

[0122] In this embodiment, the carbonization process and post-processing conditions are completely consistent with those in Example 1 (argon protection, final temperature of 1600℃ for 2.0h, water washing and drying at 80℃) to obtain hard carbon material HC-5.

[0123] The asphalt-based hard carbon anode material HC-5 is an amorphous carbon material particle with irregular powder particle morphology or quasi-spherical morphology. The particle surface is relatively dense, and its interior has an extremely rich nanoscale closed-pore structure.

[0124] Structural characterization of HC-5 was performed (the test parameter definition logic is consistent with Example 1), and the results are as follows: the total SAXS specific surface area reflecting the overall internal and external pore boundaries of the material. S SAXS It is 1190.0m 2 / g; BET specific surface area reflecting the contribution of material open pores and surface roughness. S BET It is 3.6m 2 / g; Closed-cell structure parameters ΔS (Right now S SAXS - S BET The value is 1186.4m. 2 / g. Interlayer spacing d 002 The Raman characteristic parameters are 0.378 nm. I D / I G The ratio is 1.33.

[0125] HC-5 was assembled into a sodium-ion half-cell (battery preparation and testing conditions were the same as in Example 1), exhibiting the following electrochemical performance: initial discharge plateau capacity. ΔS 297mAh / g; initial discharge ramp capacity Qp The initial discharge capacity was 102 mAh / g (total initial discharge capacity was 399 mAh / g); the initial coulombic efficiency was 88.7%; and the capacity retention after 200 cycles was 89.4%.

[0126] Product Description and Results Analysis: After synergistic crosslinking with BTC and IPA, the crosslinking precursor formed a highly suitable secondary aggregate structure ( R g 2 =17.9nm, P 2=2.62), completely entering the target prediction range. This indicates that the polycarboxylic acid crosslinking agent promotes the formation of a more stable crosslinking network between asphalt molecules under an oxygen-containing atmosphere, which not only inhibits melt flow but also facilitates the evolution into a rich internal closed-pore structure during high-temperature carbonization, thereby achieving high plateau capacity and high initial coulombic efficiency.

[0127] Example 6 (Synergistic crosslinking of terephthalic acid and isophthalic acid) The first step is to mix the asphalt-based raw material with the crosslinking agent to obtain a precursor mixture; The asphalt-based raw material (100.0 g of petroleum asphalt dissolved in tetrahydrofuran) was the same as in Example 1. The crosslinking agent was changed to a mixture of 12.0 g of terephthalic acid (PTA) and 6.0 g of isophthalic acid (IPA). Subsequent mixing and drying operations were the same as in Example 1.

[0128] The second step involves placing the precursor mixture obtained in the first step under an oxygen-containing atmosphere for cross-linking treatment. The oxygen-containing atmosphere was air (100 mL / min). This embodiment employed a single-stage crosslinking process, specifically: heating to 260°C at a rate of 2°C / min; holding at 260°C for 3.0 h; and cooling to obtain the crosslinking precursor P-6.

[0129] Step 3: Determine the thermosetting properties of the crosslinking precursor; Tests (standards consistent with Example 1) showed that P-6 had no obvious melting endothermic peak and did not experience flow collapse, thus passing the thermosetting property test.

[0130] Step 4: Determine the structural parameters and screen the conditions for crosslinking precursors; Small-angle X-ray scattering (SAXS) analysis revealed that the crosslinking precursor P-6... R g 2 =14.8nm, P 2 =2.38. The value falls within the target prediction range of this invention (14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 ≤2.65) exist Qs In the prediction model, PTA (effective functional group number feff=2, fref=3, calculated Xc=0.67, Xs=0.90) and IPA (feff=2, Xc=0.67, Xs=0.80) work synergistically. The prediction results indicate that the closed-pore parameters after carbonization will be higher, but slightly lower than those in Example 5.

[0131] Step 5: Carbonization and post-treatment.

[0132] The carbonization and post-treatment conditions were exactly the same as in Example 1, resulting in hard carbon material HC-6.

[0133] The hard carbon material HC-6 is an irregular powder particle with a nanoscale closed-pore structure, and its parameters (defined as in Example 1) are as follows: S SAXS It is 1032.0m 2 / g; S BET It is 4.1m 2 / g; Closed-cell structure parameters ΔS It is 1027.9m 2 / g; interlayer spacing d 002 0.369 nm; Raman characteristic parameters I D / I G It is 1.27.

[0134] Electrochemical performance test results (test conditions same as in Example 1): Initial discharge plateau capacity ΔS 276mAh / g; initial discharge ramp capacity Qp It has a capacity of 98 mAh / g (total capacity 374 mAh / g); initial coulombic efficiency of 87.9%; and capacity retention of 87.1% after 200 cycles.

[0135] Product Description and Results Analysis: Compared with Example 5, different combinations of aromatic polycarboxylic acids altered the precursor aggregation structure (P-6 was at the lower limit of the predicted range), resulting in a slight decrease in the final closed-pore development degree and plateau capacity. However, due to the still high... Qs and lower S BET It still achieved a synergistic balance between platform capacity and initial coulomb efficiency.

[0136] Example 7 (synergistic crosslinking of pyromellitic acid and melamine) The first step is to mix the asphalt-based raw material with the crosslinking agent; The asphalt-based raw material (100.0g petroleum asphalt) was treated in the same manner as in Example 1. The crosslinking agent was changed to 8.0g trimesic acid (BTC) and 6.0g melamine. The mixing and drying process was the same as in Example 1.

[0137] The second step is to perform cross-linking treatment in an oxygen-containing atmosphere; Air flow rate: 100 mL / min. Crosslinking program adjusted as follows: heat to 190℃ at 2℃ / min, hold for 1.0 h; then heat to 240℃ at 2℃ / min, hold for 2.5 h. Cool to obtain crosslinking precursor P-7.

[0138] Step 3: Thermosetting property determination; After testing (standards consistent with Example 1), P-7 passed the thermosetting property test.

[0139] Step 4: Structural parameter determination and condition screening; Small-angle X-ray scattering (SAXS) tests showed that P-7's R g 2 =15.2nm, P 2 =2.41. Fully entered the target prediction range.

[0140] exist ΔS In the prediction model: BTC (feff=3, Xc=1.00, Xs=1.00); melamine, as a multifunctional bridging compound, has 3 primary amines with effective reactions, and its effective reactive functional groups are feff=3, fref=3, and Xc=1.00, Xs=1.05 are calculated.

[0141] Step 5: Carbonization and post-treatment.

[0142] The carbonization final temperature in this embodiment was lowered: under argon protection, the temperature was increased to 1550°C at a rate of 3°C / min and held for 2.5 hours. Post-treatment washing and drying were performed as in Example 1 to obtain hard carbon material HC-7.

[0143] The structural parameters of the hard carbon material HC-7 (defined as in Example 1) are as follows: S SAXS It is 1065.0m 2 / g; S BET 3.8m 2 / g; Closed-cell structure parameters ΔS It is 1061.2m 2 / g; interlayer spacing d 002 0.371 nm; Raman characteristic parameters I D / I G It is 1.30.

[0144] Electrochemical performance test results (test conditions same as in Example 1): Initial discharge plateau capacity ΔS 287mAh / g; initial discharge ramp capacity Qp It has a capacity of 101 mAh / g (total capacity 388 mAh / g); initial coulombic efficiency of 88.2%; and capacity retention of 88.7% after 200 cycles.

[0145] Product Description and Results Analysis: The synergistic use of polycarboxylic acids and multifunctional bridging compounds also resulted in aggregate structures conforming to the predicted range. The introduction of melamine increased nitrogen in the cross-linked network, but the main aggregate structure characteristics ( R g 2 =15.2nm, P 2 =2.41) Excellent, with outstanding electrochemical performance, verifying the universality of this prediction method for different types of crosslinking agent combinations.

[0146] Example 8 (Synergistic crosslinking of pyromellitic acid and hyperbranched polyester) The first step is to mix the asphalt-based raw material with the crosslinking agent; The asphalt-based raw material (100.0g of petroleum asphalt) was treated in the same manner as in Example 1. The crosslinking agent was changed to 8.0g of trimesic acid (BTC) and 12.0g of hyperbranched polyester crosslinking agent. The mixture was stirred at 50°C for 90 minutes. Subsequent drying operations were the same as in Example 1.

[0147] The second step is to perform cross-linking treatment in an oxygen-containing atmosphere; Air flow rate: 100 mL / min. Crosslinking procedure: heat to 200℃ at 2℃ / min and hold for 1.0 h; then heat to 250℃ at 2℃ / min and hold for 3.0 h. Cool to obtain crosslinking precursor P-8.

[0148] Step 3: Thermosetting property determination; Tests (standards consistent with Example 1) showed that P-8 had no obvious melting endothermic peak and did not flow, thus passing the thermosetting property test.

[0149] Step 4: Structural parameter determination and condition screening; Small-angle X-ray scattering (SAXS) tests showed that P-8's R g 2 =19.8nm, P 2 =2.55. This falls within the target prediction range of this invention (14.0nm ≤ R g 2 ≤22.0nm and 2.35≤ P 2 The upper-middle range of ≤2.65).

[0150] exist Qs The prediction model incorporates parameters from two crosslinking agents: BTC (feff=3, Xc=1.00, Xs=1.00) and hyperbranched polyester (feff=4.5, Xc=1.50, Xs=1.20).

[0151] Step 5: Carbonization and post-treatment.

[0152] The carbonization and post-treatment conditions were exactly the same as in Example 1, resulting in hard carbon material HC-8. The structural parameters of the hard carbon material HC-8 (defined as in Example 1) are as follows: S SAXS It is 1118.0m 2 / g; S BET 3.5m 2 / g; Closed-cell structure parameters ΔS It is 1114.5m 2 / g; interlayer spacing d 002 0.372 nm; Raman characteristic parameters I D / I G It is 1.32.

[0153] Electrochemical performance test results (test conditions same as in Example 1): Initial discharge plateau capacity ΔS 298mAh / g; initial discharge ramp capacity Qp It has a capacity of 104 mAh / g (total capacity 402 mAh / g); initial coulombic efficiency of 89.0%; and capacity retention of 89.3% after 200 cycles.

[0154] Product Description and Results Analysis: The synergistic use of polycarboxylic acids and hyperbranched crosslinking agents combines the advantages of both crosslinking mechanisms. Aggregate structure parameters ( R g 2 =19.8nm, P 2 =2.55) indicates that the synergistic crosslinking strategy can further optimize the precursor aggregation structure, thereby achieving precise control of the closed-pore structure.

[0155] Example 9 (Synchronous preparation of pitch-based hard carbon anode material using multiple types of crosslinking agents) The first step is to mix the asphalt-based raw material with the crosslinking agent; The asphalt-based raw material (100.0g petroleum asphalt) was treated in the same manner as in Example 1. The crosslinking agent was changed to a ternary combination of 6.0g trimesic acid (BTC), 4.0g isophthalic acid (IPA), and 10.0g hyperbranched polyester crosslinking agent. The mixture was stirred at 50°C for 90 minutes. Subsequent drying procedures were the same as in Example 1.

[0156] The second step is to perform cross-linking treatment in an oxygen-containing atmosphere; Air flow rate: 100 mL / min. Crosslinking procedure: heat to 200℃ at 2℃ / min and hold for 1.0 h; then heat to 250℃ at 2℃ / min and hold for 3.0 h. Cool to obtain crosslinking precursor P-9.

[0157] Step 3: Thermosetting property determination; After testing (standards consistent with Example 1), P-9 passed the thermosetting property test.

[0158] Step 4: Structural parameter determination and condition screening; Small-angle X-ray scattering (SAXS) tests showed that P-9's R g 2 =20.2nm, P 2 =2.58. This falls within the upper-middle range of the target prediction interval of this invention.

[0159] exist Qs The prediction model incorporates parameters from three crosslinking agents: BTC (feff=3, Xc=1.00, Xs=1.00); IPA (feff=2, Xc=0.67, Xs=0.80); and hyperbranched polyester (feff=4.5, Xc=1.50, Xs=1.20).

[0160] Step 5: Carbonization and post-treatment.

[0161] The carbonization and post-treatment conditions were exactly the same as in Example 1, resulting in hard carbon material HC-9. The structural parameters of the hard carbon material HC-9 (defined as in Example 1) are as follows: S SAXS It is 1122.0m 2 / g; S BET 3.3m 2 / g; Closed-cell structure parameters ΔS It is 1118.7m 2 / g. Interlayer spacing d 002 0.373 nm; Raman characteristic parameters I D / I G It is 1.33.

[0162] Electrochemical performance test results (test conditions same as in Example 1): Initial discharge plateau capacity ΔS 305mAh / g; initial discharge ramp capacity Qp It has a capacity of 106 mAh / g (total capacity 411 mAh / g); initial coulombic efficiency of 89.5%; and capacity retention of 89.8% after 200 cycles.

[0163] Product Description and Results Analysis: This embodiment uses three different types of crosslinking agents in combination, and the resulting hard carbon material HC-9 exhibits the best overall performance (platform capacity 305 mAh / g, initial coulombic efficiency 89.5%). This demonstrates that by rationally designing the crosslinking agent combination, the precursor parameters ( R g 2 =20.2nm, P 2 Achieving an optimal balance (=2.58) allows for precise control over the microstructure and electrochemical performance of hard carbon. Guided by the predictive-control method, the preparation process is more efficient and precise, avoiding numerous trial-and-error experiments.

[0164] Example 10 (Low crosslinking agent dosage and low temperature carbonization) A method for controlling the closed-cell structure of pitch-based hard carbon anode materials, comprising the following steps: The first step is to mix the asphalt-based raw material with the crosslinking agent to obtain a precursor mixture; In this embodiment, the asphalt-based raw material was selected from petroleum asphalt (100.0g) with a softening point of 250℃, and the specific specifications and pretreatment method were the same as in Example 1. The crosslinking agent was selected from pyromellitic acid. In this embodiment, to verify the lower limit of protection, the amount of crosslinking agent added was set to 1.0wt% of the mass of the asphalt-based raw material (i.e., 1.0g of pyromellitic acid was weighed). The subsequent mixing, stirring, and drying conditions were the same as in Example 1, resulting in a precursor mixture.

[0165] The second step involves placing the precursor mixture obtained in the first step under an oxygen-containing atmosphere for cross-linking treatment. In this embodiment, the oxygen-containing atmosphere was air (100 mL / min). The crosslinking treatment adopted the same two-stage process as in Example 1: first, pre-crosslinking was performed at 200°C for 1.0 h, and then the temperature was maintained at 250°C for 3.0 h. After cooling, the crosslinking precursor P-10 was obtained.

[0166] Step 3: Determine the thermosetting properties of the crosslinked precursor obtained in Step 2; Tests (standards consistent with Example 1) showed that P-10 had no obvious melting endothermic peak in the range of 100℃-200℃ and remained solid at 400℃, thus it was determined to be a thermosetting asphalt polymer and passed the determination.

[0167] Step 4: Determine the structural parameters and screen the conditions for crosslinking precursors; Small-angle X-ray scattering (SAXS) analysis revealed the second-order cyclotron radius of the crosslinked precursor P-10. R g 2 =14.1nm, second-order mass fractal indexP 2 =2.36.

[0168] The value falls exactly within the lower limit of the target prediction range of this invention (14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 (≤2.65), is considered suitable.

[0169] exist Qs In the prediction model, pyromellitic acid contains four effective reactive carboxyl groups, i.e., the number of effective reactive functional groups feff=4, and the reference standard fref=3. The calculated effective crosslinking characteristic parameter Xc=1.33; its structural rigidity characteristic parameter Xs=1.10. The model prediction shows that although the amount added is low, due to the high functionality of the crosslinking agent, it can still induce the formation of an aggregate structure that meets the basic requirements.

[0170] Step 5: The screened crosslinking precursors are carbonized and post-treated under an inert atmosphere.

[0171] In this embodiment, to verify the lower limit of the carbonization temperature, the final carbonization temperature was set to 1000℃, and the holding time was 2.0h. The post-processing conditions were the same as in Example 1, resulting in hard carbon material HC-10. The structural parameters of the hard carbon material HC-10 (defined as in Example 1) are as follows: S SAXS It is 845.0m 2 / g; S BET It is 15.2m 2 / g; Closed-cell structure parameters ΔS 829.8m 2 / g. Interlayer spacing d 002 0.385 nm; Raman characteristic parameters I D / I G It is 1.45.

[0172] Electrochemical performance test results (test conditions same as in Example 1): Initial discharge plateau capacity ΔS 232mAh / g; initial discharge ramp capacity Qp It has a capacity of 125 mAh / g (total capacity 357 mAh / g); the initial coulombic efficiency is 82.1%.

[0173] Product Description and Result Analysis: This embodiment demonstrates the guiding value of the predictive mechanism of this invention under extremely low addition conditions. Even with an addition amount of only 1.0 wt%, as long as the precursor parameters ( Rg 2 and P 2 It can enter the predicted range (14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 (≤2.65), through model inverse guidance, materials with a platform capacity exceeding 220mAh / g can still be obtained at a low-temperature carbonization of 1000℃.

[0174] Example 11 (High crosslinking agent dosage, high-temperature crosslinking and high-temperature carbonization) The first step is to mix the asphalt-based raw material with the crosslinking agent; The asphalt-based raw material (100.0g of petroleum asphalt) was treated in the same manner as in Example 1. The crosslinking agent was selected from cyanuric acid. To verify the upper limit, the addition amount was set at 30.0wt% (i.e., 30.0g of cyanuric acid was weighed). The mixing and drying procedures were the same as in Example 1.

[0175] The second step is to perform cross-linking treatment in an oxygen-containing atmosphere; The crosslinking procedure was as follows: the temperature was increased to 200℃ at a rate of 2℃ / min and held for 1.0 h; then the temperature was increased to 450℃ and held for 3.0 h. The crosslinking precursor P-11 was obtained.

[0176] Step 3: Thermosetting property determination; After testing (standards consistent with Example 1), P-11 passed the thermosetting property test.

[0177] Step 4: Structural parameter determination and condition screening; Small-angle X-ray scattering (SAXS) analysis revealed that the crosslinking precursor P-11... R g 2 =21.8nm, P 2 =2.64. This falls within the upper limit of the target prediction range (14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 ≤2.65).

[0178] exist Qs In the prediction model, cyanuric acid has a feff of 3, and Xc = 1.00 and Xs = 1.00 are calculated. The extremely high addition amount and crosslinking temperature result in an extremely dense aggregate structure with a huge size.

[0179] Step 5: Carbonization and post-treatment.

[0180] This embodiment verifies the upper limit of carbonization temperature. Under argon protection, the temperature is increased to 2000℃ at a rate of 5℃ / min and held for 2.0h. Post-treatment washing and drying are the same as in Example 1, yielding hard carbon material HC-11.

[0181] The structural parameters of the hard carbon material HC-11 (defined as in Example 1) are as follows: S SAXS It is 1162.0m 2 / g; S BET It is 2.1m 2 / g; Closed-cell structure parameters ΔS It is 1159.9m 2 / g. Interlayer spacing d 002 0.362 nm; Raman characteristic parameters I D / I G It is 1.15.

[0182] Electrochemical performance test results (test conditions same as in Example 1): Initial discharge plateau capacity ΔS 282mAh / g; initial discharge ramp capacity Qp It has a capacity of 82 mAh / g (total capacity 364 mAh / g); the initial coulombic efficiency is 86.5%.

[0183] Product Description and Results Analysis: This example verifies that even with a high addition of 30.0 wt% and high-temperature crosslinking at 450℃, the precursor still maintains excellent aggregated state characteristics. Even after ultra-high temperature carbonization at 2000℃, relying on the stable three-dimensional network constructed in the early stage, it still retains an extremely high content of nanoscale closed pores. Qs =1159.9m 2 / g), thus maintaining a high platform capacity. This fully demonstrates the universality of the technical solution of the present invention across a wide range of process parameters.

[0184] Example 12 (Modified hyperbranched polyester crosslinking agent) The first step is to mix the asphalt-based raw material with the crosslinking agent; The asphalt-based raw material (100.0 g of petroleum asphalt) was treated in the same manner as in Example 1. The crosslinking agent was selected from modified hyperbranched polyester. The addition amount was 15.0 wt%. The subsequent mixing and drying steps were the same as in Example 1.

[0185] The second step is to perform cross-linking treatment in an oxygen-containing atmosphere; The crosslinking temperature was set at 330℃ and held for 3.0 h. The crosslinking precursor P-12 was obtained.

[0186] Step 3: Thermosetting property determination; After testing (standards consistent with Example 1), P-12 passed the thermosetting property test.

[0187] Step 4: Structural parameter determination and condition screening; Small-angle X-ray scattering (SAXS) tests showed that P-12's R g 2 =19.2nm, P 2 =2.56, which meets the prediction model range (14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 ≤2.65).

[0188] exist ΔS In the prediction model, the average end-group functionality of the modified hyperbranched polyester was determined to be feff=5.2, and Xc=1.73 was calculated. Due to the introduction of more rigid aromatic rings, its structural rigidity characteristic parameter was set to Xs=1.35. The model predicts that it will exhibit excellent pore-closure control effect after carbonization.

[0189] Step 5: Carbonization and post-treatment.

[0190] The carbonization final temperature was 1600℃, and the holding time was 2.0 h. Post-treatment washing and drying were the same as in Example 1, yielding hard carbon material HC-12. The structural parameters of the hard carbon material HC-12 are as follows: S SAXS It is 1138.0m 2 / g; S BET 3.2m 2 / g; Closed-cell structure parameters ΔS It is 1134.8m 2 / g; interlayer spacing d 002 0.372 nm; Raman characteristic parameters I D / I G It is 1.32.

[0191] Electrochemical performance test results: First discharge plateau capacity ΔS 299mAh / g; initial discharge ramp capacity Qp It has a capacity of 104 mAh / g and an initial coulombic efficiency of 89.2%.

[0192] Product Description and Results Analysis: Experimental results show that high functionality (feff=5.2) and high rigidity framework not only help to form ideal precursor parameters, but also significantly improve the electrochemical properties of the final hard carbon material, further expanding the industrial application value of this invention.

[0193] Comparative Example 1 (Preparation of pitch-based carbon materials by direct carbonization without the addition of crosslinking agents) To highlight the necessity of the crosslinking treatment and structure determination in this invention, this comparative example demonstrates the preparation process of traditional direct pyrolysis: The first step is precursor preparation; 100.0g of petroleum asphalt with a softening point of 250℃ was weighed as raw material and directly loaded into a quartz boat. No crosslinking agent or solvent was added in this comparative example.

[0194] The second step is the heat treatment process (corresponding to the crosslinking treatment in Example 1). A quartz boat filled with petroleum bitumen was placed in a tube furnace and heated in an air atmosphere at a flow rate of 100 mL / min. The specific procedure was as follows: the temperature was increased to 250 °C at a rate of 2 °C / min and held for 3.0 h. After the treatment, the sample was removed and found to have softened significantly and flowed, adhering locally to the bottom and sidewalls of the quartz boat to form irregular molten agglomerates.

[0195] Step 3: Thermosetting property determination; DSC testing was performed on the air-treated samples (test conditions were the same as in Example 1), and a clear melting endothermic peak was observed in the range of 100℃-200℃. Further treatment at 400℃ for 30 min resulted in significant softening, flow, and adhesion of the samples, preventing them from maintaining a stable solid state. Therefore, the samples failed the thermosetting test and are classified as thermoplastic materials.

[0196] Step 4: Structural parameter determination and condition screening; Because the sample failed to form a stable thermosetting polymer network, it underwent melt rearrangement during heating, failing to maintain stable secondary aggregate structure characteristics. Therefore, it was impossible to use it as a precursor. R g 2 and P 2 Structural parameters are predicted and controlled. In this comparative example, this step is skipped and the material is directly carbonized to verify the final performance.

[0197] Step 5: Carbonization and post-treatment.

[0198] The molten agglomerate sample was transferred to a graphite crucible and carbonized under high-purity argon protection (flow rate 150 mL / min). The specific procedure was as follows: the temperature was increased to 1600℃ at a rate of 3℃ / min, held for 2.0 h, and then cooled to room temperature in the furnace. The resulting sample was washed three times with deionized water until neutral, and then vacuum dried at 80℃ for 12 h to obtain carbon material C-1.

[0199] The carbon material C-1 appears as black, irregular, blocky fragments. After crushing, the particles are unevenly distributed, with localized dense molten areas, making it impossible to form the well-developed closed-pore particles described in this invention.

[0200] Structural characterization of C-1 was performed (the test parameter definition logic is consistent with Example 1), and the results are as follows: SAXS total specific surface area S SAXS Only 412.0m 2 / g;BET specific surface area S BET It is 18.6m 2 / g; Closed-cell structure parameters Qs Only 393.4m 2 / g; interlayer spacing d 002 0.365 nm; Raman characteristic parameters I D / I G It is 1.11.

[0201] Assembled into a sodium-ion half-cell (test conditions same as in Example 1): First discharge plateau capacity ΔS Only 96mAh / g; initial discharge ramp capacity Qp The initial capacity was 142 mAh / g (total initial discharge capacity was 238 mAh / g); the initial coulombic efficiency was only 72.8%; after 200 cycles, the capacity retention dropped to 73.5%.

[0202] Product Description and Results Analysis: Without the addition of a crosslinking agent, petroleum asphalt undergoes significant softening and flow during heat treatment, preventing the precursor from maintaining a stable solid structure. During subsequent carbonization, the material experiences local rearrangement and densification, resulting in extremely insufficient development of the closed-cell structure and an increase in open surfaces. This demonstrates that the introduction of a crosslinking agent and the construction of a thermosetting precursor are prerequisites for achieving the high closed-cell structure of this invention, and that the predictive model of this invention is not applicable to such thermoplastic materials.

[0203] Comparative Example 2 (Preparation of pitch-based carbon materials using monofunctional benzoic acid as an additive) The first step is to mix the asphalt-based raw materials with additives; The asphalt-based raw material (100.0 g of petroleum asphalt) was treated in the same manner as in Example 1. 18.0 g of monofunctional carboxylic acid—benzoic acid—was added as an additive. Stirring was continued at 50°C for 60 min. Subsequent solvent evaporation and vacuum drying conditions were the same as in Example 1.

[0204] The second step is to process it in an oxygen-containing atmosphere; Air flow rate: 100 mL / min. The treatment procedure was as follows: heat to 250 °C at a rate of 2 °C / min, hold for 3.0 h. Cool to obtain the treated sample P-C2.

[0205] Step 3: Thermosetting property determination; DSC testing and a 400℃ heat treatment test (standard same as Example 1) showed that P-C2 still exhibited a clear melting endothermic peak in the 100℃-200℃ range, and the sample softened and partially flowed at 400℃. The sample could not be identified as a thermosetting asphalt polymer and failed the test.

[0206] Step 4: Determining structural parameters; Because a thermosetting structure could not be formed, it was impossible to obtain data with predictive value. R g 2 and P 2 .

[0207] Analysis based on the characteristic parameter definition logic of this invention: Monofunctional benzoic acid contains only one reactive carboxyl group, meaning its effective reactive functional group number feff = 1. Since feff < 2, it cannot construct an effective three-dimensional network structure with multi-point crosslinking between asphalt molecules, and can only play a role in end-group blocking or limited grafting. Therefore, it is not suitable for the closed-cell prediction model of this invention.

[0208] Step 5: Carbonization and post-treatment.

[0209] The carbonization and post-treatment conditions were exactly the same as in Example 1 (heating at 1600℃ for 2.0h), resulting in carbon material C-2.

[0210] The obtained carbon material C-2 has poorly developed internal closed-pore structure. The structural characterization results are as follows: SAXS total specific surface area S SAXS Only 486.0m 2 / g;BET specific surface area S BET Relatively high, at 16.2m 2 / g; Closed-cell structure parameters Qs (Right now S SAXS - S BET Only 469.8m2 / g. Interlayer spacing d 002 0.363 nm; Raman characteristic parameters I D / I G It is 1.13.

[0211] The battery test results are as follows: First discharge plateau capacity ΔS 149mAh / g; initial discharge ramp capacity Qp It has a capacity of 136 mAh / g (total capacity 285 mAh / g); initial coulombic efficiency of 77.9%; and capacity retention of 78.4% after 200 cycles.

[0212] Product Description and Results Analysis: Although monofunctional benzoic acid can react with asphalt to some extent, the precursor retains its thermoplasticity due to a lack of multi-point crosslinking ability (feff=1). The resulting carbon material C-2... Qs The results are significantly lower than those in the examples, indicating that monofunctional compounds cannot form a stable precursor network that can be used for prediction, and therefore cannot achieve the structural regulation effect required by the present invention.

[0213] Comparative Example 3 (Preparation of pitch-based carbon materials by crosslinking aliphatic dicarboxylic acids) The first step is to mix the asphalt-based raw material with the crosslinking agent to obtain a precursor mixture; In this comparative example, the asphalt raw material pretreatment method was the same as in Example 1. Then, 18.0 g of aliphatic dicarboxylic acid—adipic acid—was added as a crosslinking agent. Stirring was continued at 50°C for 60 min. Subsequent solvent evaporation and vacuum drying conditions were the same as in Example 1, yielding a precursor mixture.

[0214] The second step is to perform cross-linking treatment in an oxygen-containing atmosphere; Air flow rate: 100 mL / min. A single-stage crosslinking procedure was used: temperature increased to 250 °C at 2 °C / min, and held for 3.0 h. After cooling, the crosslinking precursor P-C3 was obtained.

[0215] Step 3: Thermosetting property determination; After DSC testing and 400℃ treatment test (judgment criteria are the same as in Example 1), P-C3 showed no obvious melting endothermic peak and remained solid without flowing, thus it was determined to pass the thermosetting property test.

[0216] Step 4: Structural parameter determination and condition screening; Small-angle X-ray scattering (SAXS) analysis revealed the second-order cyclotron radius of the crosslinked precursor P-C3. R g 2 =11.5nm, second-order mass fractal index P2 =2.10.

[0217] According to the determination criteria set by the present invention (14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 (≤2.65), the parameters of P-C3 are significantly low and not within the target prediction range, so it is judged as unsuitable.

[0218] In closed-cell structure parameters [[ID=′11]]ΔS Analysis of the predictive model shows that adipic acid contains two effectively reactive carboxyl groups, i.e., the number of effective reactive functional groups feff=2 and fref=3, and the calculated effective crosslinking characteristic parameter Xc=0.67. However, due to its aliphatic long chain nature, adipic acid has extremely low structural rigidity characteristic parameter (Xs=0.40). Model predictions indicate that the interaction between its flexible segments and the aromatic components of pitch is weak, making it difficult to form sufficiently large and dense secondary aggregate structures, thus severely limiting the development of closed pores after carbonization.

[0219] Step 5: Carbonization and post-treatment.

[0220] The carbonization and post-treatment conditions were exactly the same as in Example 1 (argon protection, 1600℃ for 2.0h, water washing and drying at 80℃) to obtain carbon material C-3. Although carbon material C-3 possesses an irregular powder particle morphology, the development of its internal closed-pore structure is significantly limited. The structural characterization results (parameter definitions are the same as in Example 1) are as follows: SAXS total specific surface area S SAXS It is 824.0m 2 / g;BET specific surface area S BET It is 9.8m 2 / g; Closed-cell structure parameters ΔS (Right now S SAXS - S BET Only 814.2m 2 / g. Interlayer spacing d 002 0.366 nm; Raman characteristic parameters I D / I G It is 1.19.

[0221] Electrochemical performance test results (test conditions same as in Example 1): Initial discharge plateau capacity ΔS Only 196mAh / g; initial discharge ramp capacity QpThe initial discharge capacity was 115 mAh / g (total initial discharge capacity was 311 mAh / g); the initial coulombic efficiency was 81.7%; and the capacity retention after 200 cycles was 82.3%.

[0222] Product Description and Results Analysis: Although this comparative example introduced a crosslinking agent and successfully prepared a thermosetting precursor, the precursor parameters (…) were affected by the high flexibility of the aliphatic segments. R g 2 =11.5nm, P 2 =2.10) is far from meeting the standard (14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 ≤2.65). The resulting carbon material C-3 Qs Both the platform capacity and the actual capacity are far lower than those in the embodiments of this invention. This demonstrates the decisive influence of the molecular structural rigidity (Xs) of the crosslinking agent on the precursor aggregation structure, further verifying the scientific validity and guiding value of the prediction range of this invention.

[0223] Comparative Example 4 (Preparation of pitch-based carbon materials by crosslinking aromatic diamines alone) The first step is to mix the asphalt-based raw material with the crosslinking agent; The asphalt-based raw material (100.0 g of petroleum asphalt) was treated in the same manner as in Example 1. The crosslinking agent was changed to 18.0 g of m-phenylenediamine (an aromatic polyamine compound). The mixture was stirred at 50°C for 60 min. Subsequent drying procedures were the same as in Example 1.

[0224] The second step is to perform cross-linking treatment in an oxygen-containing atmosphere; Air flow rate: 100 mL / min. Processing procedure: heat to 250 °C at 2 °C / min, hold for 3.0 h. Cool to obtain crosslinking precursor P-C4.

[0225] Step 3: Thermosetting property determination; Tests (with the same criteria as in Example 1) showed that the DSC curve of P-C4 had no obvious melting endothermic peak, and it remained solid after treatment at 400℃, thus passing the thermosetting property test.

[0226] Step 4: Structural parameter determination and condition screening; Small-angle X-ray scattering (SAXS) analysis revealed the second-order cyclotron radius of the crosslinked precursor P-C4. R g 2 =13.2nm, second-order mass fractal index P 2 =2.25.

[0227] Although the parameters are close to the lower limit of the target prediction range of this invention (14.0 nm and 2.35), they have not yet fully met the target (14.0 nm ≤ R g 2 ≤22.0nm and 2.35≤ P 2 If the value is ≤2.65, it is considered an edge non-compliant state.

[0228] exist ΔS In the prediction model, m-phenylenediamine has two effective primary amino groups, with an effective reactive functional group number feff=2. Compared to the reference standard fref=3, the calculated Xc=0.67. As an aromatic small molecule, its structural rigidity characteristic parameter Xs=0.85. The model predicts its performance is acceptable, but it cannot reach the extremely high closed-cell level of the optimal synergistic crosslinking state.

[0229] Step 5: Carbonization and post-treatment.

[0230] The carbonization and post-treatment conditions were exactly the same as in Example 1, yielding carbon material C-4. The structural parameters of the carbon material C-4 (defined as in Example 1) are as follows: S SAXS It is 928.0m 2 / g; S BET It is 6.8m 2 / g; Closed-cell structure parameters ΔS It is 921.2m 2 / g; interlayer spacing d 002 0.367 nm; Raman characteristic parameters I D / I G It is 1.23; Electrochemical performance test results (test conditions same as in Example 1): Initial discharge plateau capacity ΔS 224mAh / g; initial discharge ramp capacity Qp The initial discharge capacity was 109 mAh / g (total initial discharge capacity was 333 mAh / g); the initial coulombic efficiency was 83.8%; and the capacity retention after 200 cycles was 84.5%.

[0231] Product Description and Results Analysis: This comparative example uses aromatic diamine as a single crosslinking agent to prepare a thermosetting precursor. R g 2 and P 2 Approaching the target prediction range, therefore its QsWhile the platform capacity is better than Comparative Example 3, it is still significantly lower than the core successful embodiments of this invention (such as Examples 6 and 11). This indicates that a single type of conventional low-functionality (feff=2) crosslinking agent has an upper limit limitation in its structural control capability and cannot simultaneously achieve the optimal synergy of high closed-cell structural parameters and high platform capacity. In contrast, this invention achieves superior overall performance through multi-crosslinking agent synergy or high-functionality hyperbranched crosslinking, combined with rigorous screening of the predicted range.

[0232] Summary of the effects and data of the embodiments and comparative examples of this invention: Through the systematic comparison of Examples 1-12 (including optimization cases for process parameters and crosslinking agent types) and Comparative Examples 1-4, the significant advantages of the present invention in regulating the microstructure of hard carbon and improving sodium storage performance can be clearly seen. The following is a comprehensive comparative analysis of key performance indicators and prediction mechanisms: Examples 1-5 fully demonstrate the core innovation of this invention: based on precursor mesoscale aggregation structure parameters ( R g 2 , P 2 The experimental data shows that: (The text abruptly ends here, likely due to an incomplete sentence or a formatting error.) (1) The current drive body structural parameters have not reached the target range set by this invention (i.e.) R g 2 <14.0nm or P 2 When <2.35), as in Examples 1, 2, 4 and Comparative Examples 3, 4, the closed-pore structure development of the final hard carbon product is not ideal, and its closed-pore structure parameters are... ΔS Generally below 900m 2 / g, initial discharge plateau capacity ΔS It is difficult to exceed 250mAh / g.

[0233] (2) When the amount and type of crosslinking agent are adjusted or the crosslinking process is optimized, the precursor parameters are made to enter the target prediction range (14.0 nm ≤ R g 2 ≤22.0nm and 2.35≤ P 2 When ≤2.65), as in Examples 3, 5 and Examples 6-11, the final product's Qp S All can be kept stable at 1000m 2 / g or more, and platform capacity Δ All exceed 275mAh / g.

[0234] This result fully proves Rg 2 and P 2 As a predictive indicator, its scientific nature and extremely high accuracy provide a quantitative basis for the rational design of hard carbon materials.

[0235] Summary of the technical advantages of this invention: The core contribution of this invention lies in establishing a quantitative prediction chain from "precursor mesoscale aggregate state" to "final product closed-cell performance". Through the complete logic of "discovering substandard parameters → theoretically predicting poor performance → targeted process adjustment → obtaining excellent materials" shown in the examples, it is proved that: (1) the parameters of the second-level aggregate structure of the precursor ( R g 2 , P 2 ) and the degree of hard carbon closed-pore development Qp There is a rigorous physicochemical correlation. (2) Through the established prediction model, unqualified batches can be eliminated in the precursor stage, guiding the scientific screening and ratio optimization of crosslinking agents. (3) This invention successfully solves the pain point of "invisible and uncontrollable" closed-cell structure in the preparation of pitch-based hard carbon, and realizes the technical leap from "experience trial and error" to "structural design".

[0236] Industrial application value: The predictive-control method proposed in this invention can significantly shorten the R&D cycle and reduce energy and raw material waste caused by indiscriminate carbonization. Experimental statistics show that after applying this method, the R&D cycle of new products can be shortened by more than 60%, and the batch stability of products can be improved by more than 35%. This provides solid technical support for the large-scale and stable preparation of asphalt-based hard carbon anode materials for high-performance sodium-ion batteries.

[0237] In the specific embodiments of the present invention described above, based on the experimental data of the examples and comparative examples, the closed-cell structure parameters... ΔS With platform capacity ΔS They exhibit a strong positive correlation. With the parameters of the closed-cell structure... Qp ΔS The improvement in [the specific parameters] leads to a corresponding increase in the sodium storage capacity of the material at its low potential plateau. The correlations described herein are used to illustrate the relationship between the crosslinking precursor structural parameters, the hard carbon closed-cell structural parameters, and the sodium storage performance in the technical solution of this invention. They should not be construed as limiting the scope of protection of this invention, which is defined by the technical solution described in the claims.

Claims

1. A method for controlling the closed-cell structure of pitch-based hard carbon anode material, wherein the pitch-based hard carbon anode material is prepared using the method, characterized in that... Specifically, the following steps are included: The first step involves mixing asphalt-based raw materials with a crosslinking agent to obtain a precursor mixture, wherein the amount of crosslinking agent added is 1-30 wt% of the mass of the asphalt-based raw materials. The second step involves placing the precursor mixture obtained in the first step under an oxygen-containing atmosphere for crosslinking treatment to obtain a crosslinked precursor. The crosslinking treatment temperature is 200-450℃ and the time is 0.5-10h. Step 3: Determine the thermosetting properties of the crosslinked precursor obtained in Step 2; If the crosslinking precursor passes the thermosetting test, proceed to step four; If the crosslinking precursor fails the thermosetting test, return to step one or step two and adjust at least one of the following: type of crosslinking agent, amount of crosslinking agent, crosslinking treatment temperature, crosslinking treatment time, or heating rate, and repeat the crosslinking treatment. Step 4: Determine the structural parameters and screen the conditions for crosslinking precursors; Small-angle X-ray scattering (SAXS) was performed on the crosslinked precursors that passed the thermosetting test to obtain the second-order gyrotron radius of the crosslinked precursors. R g 2 Second-order quality fractal index P 2 ; and based on the second-order gyro radius R g 2 Second-order quality fractal index P 2 Screening and controlling one or more of the crosslinking agent composition or crosslinking treatment conditions to obtain a crosslinking precursor with target closed-cell structure parameters; like R g 2 and P 2 If the target range is not met, return to step one or two, adjust the type of crosslinking agent, the amount of crosslinking agent, or the crosslinking treatment conditions, and repeat the crosslinking treatment and thermosetting property determination; the specific conditions for determining structural parameters are as follows: When 14.0nm≤ R g 2 ≤22.0nm and 2.35≤ P 2 When the value is ≤2.65, it is determined to be a crosslinking precursor suitable for forming the target closed-cell structure parameters, and quantitative prediction and directional design of the closed-cell structure parameters are carried out. If the requirements are met, proceed to step five. like R g 2 <14.0nm or R g 2 >22.0nm, or P 2 <2.35 or P 2 If the value is greater than 2.65, it is deemed unsuitable, and you need to return to step one or step two. Step 5: The screened crosslinking precursor is subjected to carbonization and post-treatment under an inert atmosphere to obtain pitch-based hard carbon anode material; The final temperature of the carbonization treatment is 1000-2000℃, the holding time is 0.5-10h, and the heating rate from room temperature to the carbonization temperature is 1-20℃ / min.

2. The method for controlling the closed-cell structure of pitch-based hard carbon anode material according to claim 1, characterized in that, In the method: In the first step: the asphalt raw material is selected from one or more of petroleum asphalt, coal tar pitch, medium-temperature asphalt, high softening point asphalt, SBS modified asphalt, biomass modified asphalt, or pre-oxidized asphalt; the crosslinking agent is selected from one or more of aromatic polycarboxylic acid compounds, aromatic polyamine compounds, multifunctional aromatic bridging compounds, and hyperbranched polymer crosslinking agents; specifically: the aromatic polycarboxylic acid compound is selected from at least one of trimellitic acid, isophthalic acid, terephthalic acid, and trimellitic tetracarboxylic acid; the aromatic polyamine compound is selected from at least one of m-phenylenediamine, p-phenylenediamine, 4,4'-diaminobiphenyl, and 1,5-diaminonaphthalene; the multifunctional aromatic bridging compound is selected from at least one of melamine and 4-aminophenylamine; the hyperbranched polymer crosslinking agent is selected from at least one of hyperbranched polyester crosslinking agents and modified hyperbranched polyester crosslinking agents; the amount of crosslinking agent added is 5-20 wt% of the mass of the asphalt-based raw material. In the second step: the oxygen-containing atmosphere is air, oxygen, or a mixture of oxygen and an inert gas; the heating rate is 0.5-10℃ / min; the crosslinking treatment temperature is 250-400℃, and the time is 1-6h; The thermosetting property determination in the third step includes the following two conditions: Condition 1: When tested by differential scanning calorimetry, no obvious melting endothermic peak appears in the range of 100℃-200℃; Condition 2: After heat treatment at 400℃ for 30 minutes, it still remains solid and does not soften or flow. If both conditions 1 and 2 are met, the thermosetting property test is passed; if either condition is not met, the thermosetting property test is failed, and the process parameters need to be adjusted in the second step.

3. The method for controlling the closed-cell structure of pitch-based hard carbon anode material according to claim 2, characterized in that, In the second step: The oxygen-containing atmosphere is air; The crosslinking treatment is a two-stage crosslinking process, which includes: first, pre-crosslinking at 180-220℃ for 0.5-2 hours, and then heat preservation at 230-270℃ for 2-3 hours.

4. The method for controlling the closed-cell structure of pitch-based hard carbon anode material according to claim 3, characterized in that, The specific steps for the quantitative prediction and directional design of the closed-cell structure parameters in the fourth step are as follows: To achieve precise control over the closed-cell structure of pitch-based hard carbon anode materials, a prediction model for closed-cell structure parameters based on precursor structural characteristics and crosslinking agent molecular properties was established. This model quantitatively predicts and directionally designs the target closed-cell structure parameters of hard carbon materials by quantifying the mesoscale aggregation structure of the crosslinking precursor and the molecular properties of the crosslinking agent. The target closed-cell structure parameters are predicted using the following empirical formula: ΔS =A+B× R g 2 +C×( P 2 -1.5)+D×Xc+E×Xs; in: ΔS The closed-pore structure parameter characterizes the closed-pore content inside hard carbon materials and is defined as the small-angle X-ray scattering specific surface area. S SAXS BET specific surface area S BET The difference, in m 2 / g, that is ΔS = S SAXS - S BET ; S SAXS This represents the total specific surface area of ​​SAXS, in m². 2 / g; S BET This represents the specific surface area of ​​BET, in meters. 2 / g; R g 2 is the second-order gyroscopic radius of the crosslinking precursor, in nm; P 2 is the second-order mass fractal index of the crosslinking precursor, which is dimensionless; Xc is the effective crosslinking characteristic parameter of the crosslinking agent; Xs is a structural rigidity characteristic parameter of the crosslinking agent; A, B, C, D, and E are fitting coefficients, determined through experimental data calibration. A is the first fitting coefficient, B is the second fitting coefficient, C is the third fitting coefficient, D is the fourth fitting coefficient, and E is the fifth fitting coefficient. The fitting coefficients A, B, C, D, and E are determined through the following steps: First, different crosslinking precursors were prepared using different crosslinking agents and crosslinking treatment conditions; second, small-angle X-ray scattering (SAXS) tests were performed on the crosslinking precursors to obtain... R g 2 and P 2 Value; secondly, relevant specific surface area tests were performed on the hard carbon material, and the values ​​were calculated. ΔS Value; subsequently, based on the least squares method or other regression analysis methods, establish ΔS and R g 2 , P 2 Quantitative relationship between Xc and Xs, and determine each fitting coefficient; Based on the closed-cell structure parameter prediction model, according to the required closed-cell structure parameters ΔS The second-order gyro radius required for reverse design of crosslinking precursors R g 2 Second-order quality fractal index P 2 The Xc and Xs parameters of the crosslinking agent were determined, and the treatment conditions were optimized to achieve precise control over the closed-cell structure of hard carbon materials.

5. The method for controlling the closed-cell structure of pitch-based hard carbon anode material according to claim 4, characterized in that, Specifically: In the fourth step: The method for determining Xc is as follows: Xc = feff / fref; where feff is the average effective reactive functionality of the crosslinking agent, and fref is the reference functionality, with a value of 3; the specific calculation and definition method for feff is as follows: For low-molecular-weight aromatic polycarboxylic acid compounds or aromatic polyamine compounds, feff is equal to the number of effective reactive carboxyl or amino groups in a single molecule that can participate in the cross-linking reaction at a given cross-linking temperature; For multifunctional aromatic bridging compounds, feff equals the number of cross-linking sites or effective bridging functional groups in the molecule. For hyperbranched polymer crosslinking agents, feff equals the average number of effective reactive functional groups carried by the internal or external end groups of each molecule of the hyperbranched polymer crosslinking agent.

6. The method for controlling the closed-cell structure of pitch-based hard carbon anode material according to claim 5, characterized in that, In the fifth step: The inert atmosphere is nitrogen, argon, or a mixture of both. The final temperature of the carbonization treatment is 1200-1800℃, the holding time is 1-5h, and the heating rate is 2-10℃ / min; The post-treatment includes washing and drying; the washing stage uses deionized water or dilute acid as the washing medium; the drying stage has a temperature of 60-120℃ and a drying time of 6-24h.

7. A pitch-based hard carbon anode material, characterized in that, The asphalt-based hard carbon anode material is prepared using the method for controlling the closed-pore structure of the asphalt-based hard carbon anode material according to any one of claims 1-6; the asphalt-based hard carbon anode material is an amorphous carbon material particle with an irregular powder particle morphology or a near-spherical morphology, the particle surface is dense, and its interior has a nanoscale closed-pore structure, having at least one of the following structural parameters: Calculate the specific surface area of ​​the opening, i.e., the BET specific surface area (SBET). S BET 1-20m 2 / g; Closed-cell structure parameters ΔS 800-1200m 2 / g; Interlayer spacing of pitch-based hard carbon anode materials d 002 The wavelength is 0.36-0.40 nm. Raman characteristic parameters I D / I G The ratio is 1.0-1.5, dimensionless.

8. The pitch-based hard carbon anode material according to claim 7, characterized in that, The structural parameters of the pitch-based hard carbon anode material are adjusted as follows: Specific surface area of ​​openings S BET 2-10m 2 / g; Closed-cell structure parameters ΔS 1000-1150m 2 / g; Interlayer spacing of pitch-based hard carbon anode materials d 002 The wavelength is 0.366-0.39 nm. Raman characteristic parameters I D / I G The ratio is 1.2-1.4, dimensionless.

9. The application of the pitch-based hard carbon anode material according to claim 7 or 8, characterized in that, The application of the asphalt-based hard carbon anode material in sodium-ion battery anodes; specifically: using the asphalt-based hard carbon anode material as the active material to prepare anode sheets, which are then assembled with cathode sheets, electrolytes, and separators to form a sodium-ion battery; in sodium-ion half-cell testing, with 0.1V as the boundary between the plateau region and the slope region, it possesses at least one of the following electrochemical properties: First discharge plateau capacity Qp It is 230-310mAh / g; First discharge ramp capacity Qs Greater than 90mAh / g; The initial coulomb efficiency is greater than 85%; After 200 cycles, the capacity retention rate is no less than 85%.

10. The application of the pitch-based hard carbon anode material according to claim 9, characterized in that, The electrochemical performance is as follows: First discharge plateau capacity Qp The capacity is 230~310mAh / g; First discharge ramp capacity Qs The capacity is 90~160mAh / g; The initial coulomb efficiency is 85-92%. After 200 cycles, the capacity retention rate is 85-95%.

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