Asphalt-based mesoporous carbon and preparation method and application thereof

Abstract

The application belongs to the field of battery materials, and discloses a pitch-based mesoporous carbon and a preparation method and application thereof. The pitch-based mesoporous carbon has multiple pores, the average pore diameter of the pores is 2-5 nm, and the ratio of the pore volume of the pores with a pore diameter of 0.5-5 nm to the pore volume of all the pores is greater than or equal to 90%. Compared with the porous carbon in the prior art which has a wide pore diameter distribution and a low proportion of micropores and mesopores, the pitch-based mesoporous carbon provided by the application has a narrower pore diameter distribution and a significantly higher enrichment degree of micropores and mesopores. The high-proportion, narrow-distribution micropore and mesopore structure can provide efficient and rapid transmission channels for lithium ions, improve the rate performance of the material, effectively buffer volume expansion, improve the structural stability, and avoid problems such as low utilization and easy collapse of the structure caused by excessively large pores, so that the material has excellent ion transmission efficiency, cycle stability and structural integrity when used as a negative electrode material.

Description

Technical Field

[0001] This invention belongs to the field of battery materials, and relates to a negative electrode material, specifically to a pitch-based mesoporous carbon and its preparation method and application. Background Technology

[0002] In recent years, with the rapid development of lithium-ion batteries towards higher energy density and longer cycle life, silicon-carbon anode materials, with their advantages such as high theoretical specific capacity, have become an important research direction and industrial hotspot for replacing traditional graphite anodes. Silicon-carbon materials, by loading silicon active materials into pitch-based mesoporous carbon, can alleviate the severe volume expansion of silicon during charging and discharging to a certain extent, improving electrode structural stability and electrochemical performance, and have shown broad application prospects in fields such as power batteries and energy storage batteries. However, the pore structure parameters of pitch-based mesoporous carbon directly determine the silicon loading state, ion transport efficiency, and structural support capacity, and remain a key factor restricting further improvement in the overall performance of silicon-carbon materials.

[0003] Currently, the preparation of porous pitch-based mesoporous carbon mainly relies on traditional activation methods, hard template methods, soft template methods, and self-templating methods. Among these, the activation method, as the mainstream mass production process, uses biomass, resin, coal, etc., as carbon sources. After high-temperature carbonization, pores are formed by etching with activators such as KOH and CO2. Although this method is low-cost and easy to scale up, the etching effect of the activator is random, making it difficult to precisely control the formation position and size of the pores. This results in a very wide pore size distribution, with micropores, mesopores, and macropores mixed together, and the average pore size often exceeding 20 nm. Hard template methods and soft template methods introduce template agents such as SiO2, molecular sieves, and surfactants to regulate the pore structure. Although this improves the controllability of pore size, the size distribution of the template agent itself is limited, and the uniformity of carbon source deposition along the thickness direction is difficult to control, still failing to avoid the problem of a wide pore size distribution. At the same time, these methods also suffer from the disadvantages of complex processes and high costs. The self-templating method uses MOFs / COFs as precursors and forms pitch-based mesoporous carbon after high-temperature carbonization. Although the pore size accuracy is relatively high, the yield is extremely low and the cost is high due to the synthesis characteristics of the precursors, making it difficult to achieve industrial application. Overall, the core limitation of the existing preparation process is the lack of precise control over the pore formation process, which leads to pitch-based mesoporous carbon generally exhibiting a wide pore size distribution and large pore size.

[0004] Pitch-based mesoporous carbon with excessively wide pore size distribution and large pore dimensions exhibits significant performance defects when applied to silicon-carbon materials. The excessively large and uneven pores fail to effectively bind and support silicon particles, easily exacerbating silicon volume deformation and structural pulverization during charge-discharge cycles, leading to decreased electrode integrity. Simultaneously, the loose and disordered pore structure hinders rapid and stable lithium-ion transport, increasing electrode polarization, reducing the material's rate performance and cycle stability, and thus severely impacting the overall electrochemical performance of silicon-carbon materials. Summary of the Invention

[0005] In view of the defects and deficiencies of the existing technology, the present invention provides, in a first aspect, a pitch-based mesoporous carbon; in a second aspect, a silicon-carbon material; in a third aspect, a method for preparing pitch-based mesoporous carbon; in a fourth aspect, a method for preparing silicon-carbon material; and in a fifth aspect, a battery.

[0006] Firstly, the pitch-based mesoporous carbon contains multiple channels, the average pore size of which is 2-5 nm, the pore volume of channels with a pore size of 0.5-5 nm is V1, and the total pore volume is V. 总 V1∶V 总 ≥90%.

[0007] Preferably, the total pore volume of the pitch-based mesoporous carbon is 0.5~1.5 cm³. 3 / g.

[0008] Preferably, the Dv50 of the pitch-based mesoporous carbon is 1~20μm.

[0009] Further preferably, the Dv50 of the pitch-based mesoporous carbon is 7~10μm.

[0010] Preferably, the pitch-based mesoporous carbon has a diameter spacing of 0.5 to 2.0.

[0011] Further preferably, the pitch-based mesoporous carbon has a diameter spacing of 0.7~1.2.

[0012] Preferably, the pitch-based mesoporous carbon contains a metal element M, which is any one or both of Mg and Al.

[0013] Preferably, the content of the M metal element is 2000~15000ppm.

[0014] Preferably, the morphology of the pitch-based mesoporous carbon is any one or more of blocky, spherical, or near-spherical shapes.

[0015] In a second aspect, the present invention provides a silicon-carbon material comprising the pitch-based mesoporous carbon, silicon, and a carbon coating layer as described in the first aspect, wherein the silicon is distributed in the pores of the pitch-based mesoporous carbon, and the carbon coating layer covers at least a portion of the surface of the particles formed by the pitch-based mesoporous carbon and the silicon.

[0016] Preferably, the silicon-carbon material contains 30% to 70% silicon by mass.

[0017] Further preferably, the silicon-carbon material contains 45% to 55% silicon by mass.

[0018] Preferably, the dynamic specific gravity of the silicon-carbon material is 0.7~20cm. 2 / g.

[0019] More preferably, the dynamic specific surface area of ​​the silicon-carbon material is 0.7~5cm. 2 / g.

[0020] Thirdly, the present invention provides a method for preparing pitch-based mesoporous carbon, comprising the following steps: Step 1: Add ammonium persulfate, emulsified asphalt, and water-soluble template agent to water to obtain a mixture; Step 2: Heat and stir the mixture, then dry it to obtain the intermediate material; Step 3: After crushing the intermediate material, heat-treat it under a nitrogen atmosphere to obtain a solid material; Step 4: The solid material is crushed, removed from the template, and washed in sequence to obtain the asphalt-based mesoporous carbon.

[0021] Preferably, in step 1, the mass ratio of ammonium persulfate, emulsified asphalt, and water-soluble template agent is 1:(1~2.5):(1~2.5), and the solid content of the emulsified asphalt is 5wt%~40wt%.

[0022] Preferably, in step 1, the ratio of the sum of the masses of ammonium persulfate, emulsified asphalt, and water-soluble template agent to the mass of water is (5wt%~50wt%):1.

[0023] Preferably, in step 1, the water-soluble template agent is any one or more of magnesium lactate, magnesium citrate, magnesium chloride, magnesium sulfate, aluminum lactate, aluminum citrate, and aqueous silica sol.

[0024] Further preferred, in step 1, the water-soluble template agent is any one or more of magnesium chloride, magnesium sulfate, aluminum lactate, and water-based silica sol.

[0025] Preferably, in step 1, when the template agent is selected from magnesium lactate, magnesium citrate, aluminum lactate, or aluminum citrate, hydrochloric acid is added to adjust the pH value of the mixture to 1-3.

[0026] Preferably, in step 2, the heating temperature is 20~80℃, the stirring rate is 50~500rpm, and the stirring time is 1~30h.

[0027] Preferably, in step 2, the drying temperature is 80~180℃.

[0028] Preferably, in step 3, the intermediate material is crushed using an airflow crushing process, and the particle Dv50 of the crushed material is 7~10μm.

[0029] Preferably, step 3, after crushing the intermediate material and before heat treatment, includes a spheroidizing process, in which the crushed solid particles are put into heat transfer oil and heated at 150~300℃ for 3~30 hours, and then filtered to obtain the final product.

[0030] Preferably, the mass ratio of solid particles to heat transfer oil is (5~30):100.

[0031] Preferably, in step 3, the heat treatment includes two stages: the first stage is held at 200~550℃ for 1~10h; the second stage is held at 600~1500℃ for 1~10h.

[0032] Further optimization is made in step 3, where the heat treatment temperature in the first stage is 300~400℃ and the heat treatment temperature in the second stage is 850~1100℃.

[0033] Preferably, in step 4, the solid material is crushed using an airflow crushing process, and the crushed particles have a Dv50 of 8~9μm, Dmax < 22μm, and diameter < 1.

[0034] Preferably, in step 4, the crushed solid material is soaked in hydrochloric acid solution at 20~90℃ for 4~24h, and then washed with pure water 2~4 times to obtain the asphalt-based mesoporous carbon.

[0035] Preferably, the concentration of the hydrochloric acid solution is 0.2~2 mol / L, and the mass ratio of the solid material to the hydrochloric acid solution is (0.05~0.5):1.

[0036] Fourthly, the present invention provides a method for preparing a silicon-carbon material, comprising the following steps: Step 1: The pitch-based mesoporous carbon obtained in the first aspect or the pitch-based mesoporous carbon obtained by the preparation method provided in the third aspect is subjected to gas-phase chemical reaction to precipitate silica, thereby obtaining an intermediate product. Step 2: Carbon coating of the intermediate product is carried out by gas-phase chemical process to obtain the silicon-carbon material.

[0037] Fifthly, the present invention provides a battery comprising the silicon-carbon material described in the second aspect.

[0038] Compared with the prior art, the present invention has the following significant advantages: (1) The average pore size of the pitch-based mesoporous carbon of the present invention is 2~5nm, and the ratio of the pore volume of the 0.5~5nm channel to the pore volume of all channels is ≥90%. Compared with the porous carbon in the prior art with a wide pore size distribution and a low proportion of micropores and mesopores, the pitch-based mesoporous carbon provided by the present invention has a narrower pore size distribution and a significantly higher enrichment of micropores and mesopores. This high proportion and narrow distribution of micropores and mesopores can provide an efficient and fast transport channel for lithium ions, improve the rate performance of the material, effectively buffer volume expansion and improve structural stability, and avoid problems such as low utilization rate and easy structural collapse caused by excessively large channels. This makes the material have excellent ion transport efficiency, cycle stability and structural integrity when used as a negative electrode material.

[0039] (2) By introducing Mg and Al metal elements into pitch-based mesoporous carbon, the present invention can, on the one hand, further regulate the narrow distribution of micropores and mesopores of 0.5~5nm by means of the pore-forming effect of metal compounds during carbonization, thereby increasing the proportion of micropores and mesopores; on the other hand, the small amount of residual Mg and Al elements can optimize the interfacial conductivity and ion transport efficiency during electrochemical processes, while enhancing the structural rigidity of the carbon skeleton and alleviating the volume deformation during charging and discharging, so that the material can maintain high mesoporous order while having better cycle stability and rate performance.

[0040] (3) This invention uses emulsified asphalt as carbon source and ammonium persulfate as oxidant and dopant to achieve uniform molecular-level dispersion of carbon source precursor and template agent in aqueous phase. No organic solvent or complex pre-modification is required. The process is mild, green and low cost. Molecular-level dispersion ensures regular and uniform pore structure, and can synergistically regulate active sites on material surface, thus possessing both excellent pore structure performance and reactivity. Attached Figure Description

[0041] Figure 1 The DFT pore size distribution curve of the pitch-based mesoporous carbon obtained in step 4 of Example 1 is shown. Figure 2 Here is a SEM image of the silicon-carbon material prepared in Example 1; Figure 3 TEM image of the silicon carbide material prepared in Example 1; Figure 4 The image shows the XRD pattern of the silicon-carbon material prepared in Example 1. Figure 5 This is a SEM image of the silicon-carbon material prepared in Example 4. Detailed Implementation

[0042] The present invention provides the following specific technical solutions.

[0043] In a first aspect, the present invention provides a pitch-based mesoporous carbon, wherein the pitch-based mesoporous carbon has a plurality of channels distributed therein, the average pore size of the channels is 2-5 nm, the pore volume of the channels with a pore size of 0.5-5 nm is V1, and the total pore volume is V. 总 V1∶V 总 ≥90%.

[0044] Research has revealed that existing technologies such as hard template, soft template, and self-templating lack precise control over the pore formation process. This results in pitch-based mesoporous carbon materials exhibiting a wide pore size distribution and excessively large pore size. The excessively large and uneven pores are unable to effectively bind and support silicon particles, which can exacerbate silicon volume deformation and structural pulverization during charge-discharge cycles, leading to a decrease in electrode integrity. At the same time, the loose and disordered pore structure is not conducive to the rapid and stable transport of lithium ions, which increases electrode polarization, reduces the rate performance and cycle stability of the material, and thus seriously affects the overall electrochemical performance of silicon-carbon materials.

[0045] This invention provides a pitch-based mesoporous carbon with a small average pore size of only 2-5 nm. The ratio of the pore volume of the pores with a pore size of 0.5-5 nm to the total pore volume is ≥90%. The pore size distribution is highly concentrated and the pore structure is highly uniform, which avoids the problem of wide and uneven pore size in traditional materials. It can provide a stable and smooth channel for ion transport and form an effective physical confinement effect for loaded active substances, significantly improving the structural stability and application performance of the material.

[0046] Preferably, the total pore volume of the pitch-based mesoporous carbon is 0.5~1.5 cm³. 3 / g.

[0047] Preferably, the Dv50 of the pitch-based mesoporous carbon is 1~20μm.

[0048] Research has shown that controlling the Dv50 of pitch-based mesoporous carbon within the range of 1–20 μm ensures that the material particles are of moderate size and uniformly distributed. This avoids the problems of excessively fine particles causing agglomeration, poor flowability, and difficulty in electrode compaction during processing, as well as excessively large particles causing rough electrode surfaces and excessively long ion transport paths. The moderate particle size effectively improves the dispersion stability of the slurry and the uniformity of electrode coating, while optimizing the contact interface between the material and the electrolyte, shortening the ion transport distance, and balancing processing performance and electrochemical kinetics, thus significantly improving the overall performance and process adaptability of the composite material.

[0049] Further preferably, the Dv50 of the pitch-based mesoporous carbon is 7~10μm.

[0050] Research has shown that controlling the Dv50 of pitch-based mesoporous carbon within the narrow range of 7~10μm results in a more moderate particle size and more uniform distribution. This avoids problems such as slurry agglomeration, roller sticking, and uneven coating caused by excessive fine powder, and also prevents surface defects and local stress concentration on the electrode caused by large particles.

[0051] Preferably, the pitch-based mesoporous carbon has a diameter spacing of 0.5 to 2.0.

[0052] Research has shown that by further controlling and optimizing the spacing of pitch-based mesoporous carbon, the uniformity of particle size can be improved, which can effectively avoid the adverse effects of the coexistence of large particles and fine powder. Narrow particle size distribution can significantly improve the stability and coating smoothness of electrode slurry, improve the compaction consistency of electrode sheets, reduce local stress unevenness and ion transport differences, and thus improve the structural stability and cycle reliability of materials in electrochemical applications.

[0053] Further preferably, the pitch-based mesoporous carbon has a diameter spacing of 0.7~1.2.

[0054] Preferably, the pitch-based mesoporous carbon contains a metal element M, which is any one or both of Mg and Al.

[0055] Research has shown that introducing one or both of the metal elements Mg and Al into pitch-based mesoporous carbon can, on the one hand, regulate the pore structure during carbonization, assisting in the formation of uniform and regular 0.5–5 nm micropores and mesopores, which is beneficial for stabilizing the pore size distribution and increasing the 0.5–5 nm pore volume ratio, ensuring a uniform and ordered pore structure. On the other hand, the presence of metal elements can enhance the structural strength and mechanical stability of the carbon matrix, better resisting volume deformation during charge and discharge after silicon loading, and inhibiting electrode structure pulverization. Simultaneously, these metal elements can optimize the conductivity and interfacial properties of carbon materials, reduce lithium-ion transport impedance, reduce electrode polarization, and further improve the rate performance and cycle stability of silicon-carbon composites. Furthermore, Mg and Al are widely available and inexpensive, and do not introduce toxic or harmful components, offering the dual advantages of structural regulation and improved electrochemical performance. The residual metals have high surface energy and can act as condensation nuclei for silicon vapor, promoting uniform silicon deposition within the pores.

[0056] Preferably, the content of the M metal element is 2000~15000ppm.

[0057] Research has shown that the aforementioned optimal range is sufficient to maintain a continuous and stable metal-carbon interface structure within the carbon framework, improving the mesopores' resistance to collapse during subsequent processing and use; it also prevents excessive metal from clogging the 2-5 nm mesopore channels, thus ensuring a high mesopore ratio and pore unobstructed flow. Simultaneously, this residual level provides uniform and appropriate amounts of basic or Lewis acid sites on the carbon matrix surface, enhancing the material's adsorption affinity for polar molecules or acidic gases and imparting additional pseudocapacitive contributions or catalytic activity.

[0058] Preferably, the morphology of the pitch-based mesoporous carbon is any one or more of blocky, spherical, or near-spherical shapes.

[0059] In a second aspect, the present invention provides a silicon-carbon material comprising the pitch-based mesoporous carbon, silicon, and a carbon coating layer as described in the first aspect, wherein the silicon is distributed in the pores of the pitch-based mesoporous carbon, and the carbon coating layer covers at least a portion of the surface of the particles formed by the pitch-based mesoporous carbon and the silicon.

[0060] Research has shown that using pitch-based mesoporous carbon as a carrier, as described in the first aspect, can confine silicon within matching pores, effectively restricting the volume expansion of silicon during charging and discharging, inhibiting silicon particle pulverization and electrode structure collapse, and ensuring the integrity of the electrode structure. At the same time, the uniformly distributed narrow-aperture pores provide a stable and smooth transport path for lithium ions, reducing electrode polarization and improving ion transport efficiency and reaction kinetics. This fundamentally solves the problem of poor electrochemical performance of silicon-carbon materials caused by the wide and uneven pore size distribution of traditional pitch-based carbon carriers.

[0061] Preferably, the silicon-carbon material contains 30% to 70% silicon by mass.

[0062] Research has shown that controlling the silicon content within the optimal range of 30% to 70% ensures that silicon-carbon materials have a high theoretical capacity to meet the application requirements of high-energy-density batteries. At the same time, it avoids the problems of structural pulverization and rapid capacity decay caused by excessive volume expansion due to excessive silicon content. Furthermore, it forms a good synergy with the pitch-based mesoporous carbon support and carbon coating layer, taking into account the material's reversible capacity, structural stability, and cycle performance, thus achieving an optimal balance between high capacity and long cycle life for silicon-carbon materials.

[0063] Further preferably, the silicon-carbon material contains 45% to 55% silicon by mass.

[0064] Preferably, the dynamic specific gravity of the silicon-carbon material is 0.7~20cm. 2 / g.

[0065] In practical applications, the dynamic specific surface area of ​​silicon-carbon materials is tested using dynamic flow methods (such as continuous flow chromatography), calculated by measuring the dynamic adsorption behavior of the material for a specific gas. This parameter reflects the effective contact area of ​​silicon-carbon materials under dynamic conditions, and is a different concept and testing method from the static BET specific surface area of ​​porous carbon.

[0066] Research has shown that the above-mentioned optimal specific surface area range is moderate, which can provide sufficient reaction sites for lithium ion insertion and extraction, ensuring good ion transport and reaction kinetics, while avoiding problems such as increased electrolyte side reactions and reduced first coulombic efficiency caused by excessive specific surface area. At the same time, it is compatible with the pore structure of pitch-based mesoporous carbon and the volume effect of loaded silicon, which helps to improve electrode interface stability, reduce polarization, and thus optimize the cycle stability and rate performance of silicon-carbon materials.

[0067] More preferably, the dynamic specific surface area of ​​the silicon-carbon material is 0.7~5 cm⁻¹. 2 / g.

[0068] Thirdly, the present invention provides a method for preparing pitch-based mesoporous carbon, comprising the following steps: Step 1: Add ammonium persulfate, emulsified asphalt, and water-soluble template agent to water to obtain a mixture; Step 2: Heat and stir the mixture, then dry it to obtain the intermediate material; Step 3: After crushing the intermediate material, heat-treat it under a nitrogen atmosphere to obtain a solid material; Step 4: The solid material is crushed, removed from the template, and washed in sequence to obtain the asphalt-based mesoporous carbon.

[0069] Research has revealed that existing technologies typically use organic solvents to dissolve asphalt and employ inorganic templates insoluble in these solvents to prepare carbon skeletons using a hard template method. Due to phase separation between the asphalt carbon source and the hard template, uniform molecular-level composite formation is impossible. The template exists only as solid particles mechanically dispersed in the asphalt solution, resulting in poor dispersion uniformity and difficulty in precisely controlling pore size during subsequent carbonization. This leads to a wide pore size distribution, poor pore connectivity, and a high proportion of large pores. Furthermore, template removal is difficult, easily causing pore collapse and blockage. The wide pore size distribution of the carbon skeleton is detrimental to effectively confining and supporting silicon particles, resulting in poor suppression of volume expansion and structural pulverization during charging and discharging. It also fails to provide a stable and unobstructed short-range transport channel for lithium ions, leading to a significant decrease in the structural stability, rate performance, and cycle stability of the subsequent silicon-carbon composite material, making it difficult to meet the application requirements of high-capacity lithium-ion batteries.

[0070] To improve production line safety and increase production efficiency, further research revealed that this process uses water as a medium and avoids flammable and explosive organic solvents, eliminating safety hazards such as solvent evaporation and explosion at the source, significantly improving the safety of large-scale production. Simultaneously, ammonium persulfate is used as a surface treatment agent, greatly improving the dispersibility of emulsified asphalt in water. Combined with a water-soluble template agent, this achieves uniform molecular-level dispersion of the carbon source precursor and the template agent, effectively avoiding the phase separation problem of traditional hard template methods. Relying on the molecularly uniformly dispersed template agent to precisely limit the pore growth size and distribution, it is possible to efficiently control and stably obtain a small-pore mesoporous structure with an average pore size concentrated in the 2-5 nm range. Furthermore, ammonium persulfate improves asphalt dispersibility, resulting in a loose and uniform carbon skeleton structure with good pore connectivity after carbonization. The aqueous solution can quickly penetrate into the pores to fully dissolve the metal oxides (which are the carbonized template agents), eliminating the need for highly corrosive reagents or prolonged high-temperature treatment. Therefore, template removal is gentler, faster, and more thorough, while also preventing pore collapse, blockage, or structural damage. In other words, this process is simple, the conditions are mild, and the post-processing is easy. Template removal is easier and less likely to cause pore collapse and blockage. While improving the uniformity of the product pore structure and electrochemical performance, it significantly improves production efficiency and product consistency, making it more suitable for industrial continuous production.

[0071] Preferably, in step 1, the mass ratio of ammonium persulfate, emulsified asphalt, and water-soluble template agent is 1:(1~2.5):(1~2.5), and the solid content of the emulsified asphalt is 5wt%~40wt%.

[0072] Preferably, in step 1, the ratio of the sum of the masses of ammonium persulfate, emulsified asphalt, and water-soluble template agent to the mass of water is (5wt%~50wt%):1.

[0073] Preferably, in step 1, the water-soluble template agent is any one or more of magnesium lactate, magnesium citrate, magnesium chloride, magnesium sulfate, aluminum lactate, aluminum citrate, and aqueous silica sol.

[0074] Further preferred, in step 1, the water-soluble template agent is any one or more of magnesium chloride, magnesium sulfate, aluminum lactate, and water-based silica sol.

[0075] Further optimization involves adding hydrochloric acid to adjust the pH of the mixture to 1-3 when magnesium lactate, magnesium citrate, aluminum lactate, or aluminum citrate are selected as template agents in step 1.

[0076] Research revealed that when magnesium lactate, magnesium citrate, aluminum lactate, or aluminum citrate are used as template agents, they may not completely dissolve at room temperature. Therefore, hydrochloric acid is added to adjust the solubility of the template agent. After adding hydrochloric acid, magnesium citrate undergoes an acid-dissolution reaction, dissociating into soluble citric acid and magnesium ions, thus achieving uniform molecular-level dispersion of the template agent in the system. Simultaneously, ammonium persulfate exhibits improved stability in an acidic environment, preventing premature decomposition and allowing for full utilization of its oxidative modification effect. The system is stirred until it reaches a homogeneous and stable state, yielding a mixture.

[0077] Preferably, in step 2, the heating temperature is 20~80℃, the stirring rate is 50~500rpm, and the stirring time is 1~30h.

[0078] Further optimization is that in step 2, the heating temperature is 55~80℃.

[0079] Research has shown that mixing raw materials at a suitable temperature can improve the dispersion uniformity of each raw material component, activate the oxidation of ammonium persulfate, achieve controllable demulsification of emulsified asphalt, improve the dispersibility of emulsified asphalt in the mixture, and ensure that the water-soluble template agent is uniformly dispersed in the emulsified asphalt matrix, thus ensuring the orderly and controllable final mesoporous carbon channel structure.

[0080] Preferably, in step 2, the drying temperature is 80~180℃.

[0081] Preferably, in step 3, the intermediate material is crushed using an airflow crushing process, and the crushed particles have a Dv50 of 7~10μm.

[0082] Preferably, step 3, after crushing the intermediate material and before heat treatment, includes a spheroidizing process. The crushed solid particles are put into heat transfer oil, heated to 150~300℃ for 3~30 hours, and then filtered to obtain the final product.

[0083] Preferably, in step 3, the heat treatment includes two stages: the first stage is held at 200~550℃ for 1~10h; the second stage is held at 600~1500℃ for 1~10h.

[0084] Research has shown that, using this segmented heat treatment process, during the heating process in step 2, ammonium persulfate initiates mild cross-linking of the emulsified asphalt, only increasing the softening point without complete curing. The initial heating to 200-550℃ during carbonization allows the asphalt to fully soften and achieve good fluidity, fully filling the gaps and internal voids of the template agent, achieving a tight fit between the carbon source and the template, laying the structural foundation for the subsequent formation of uniform and regular channels. Continuing to heat to 600-1500℃ for high-temperature carbonization promotes the full carbonization of the asphalt carbon source, molecular structure rearrangement, and the formation of a stable carbon skeleton. This ensures the carbon matrix possesses suitable structural strength and conductivity while precisely preserving the 2-5nm uniform mesoporous structure defined by the template agent, preventing channel collapse or deformation. Ultimately, this yields asphalt-based mesoporous carbon with uniform channel distribution, stable structure, and excellent electrochemical performance.

[0085] Further optimization is made in step 3, where the heat treatment temperature in the first stage is 300~400℃ and the heat treatment temperature in the second stage is 850~1100℃.

[0086] Preferably, in step 4, the solid material is crushed using an airflow crushing process, and the crushed particles have a Dv50 of 7~9μm, Dmax < 22μm, and diameter < 1.

[0087] Preferably, in step 4, the crushed solid material is soaked in hydrochloric acid solution at 20-90°C for 4-24 hours, and then washed with pure water 2-4 times to obtain the asphalt-based mesoporous carbon.

[0088] Studies have shown that using a single acid solution is less effective at removing metal oxides than using a composite acid system, leaving a small amount of metal oxides in the carbon framework. These residual metal oxides can serve as heterogeneous nucleation sites during subsequent silicon infiltration, inducing uniform nucleation and growth of silicon within the pores. This promotes a tightly bonded interface between the silicon phase and the carbon matrix, achieving uniform loading and stable anchoring of silicon within the mesoporous channels. It also inhibits the aggregation and shedding of silicon particles during charging and discharging, ultimately significantly improving the structural stability and cycle reliability of silicon-carbon materials.

[0089] Preferably, the concentration of the hydrochloric acid solution is 0.2~2 mol / L, and the mass ratio of the solid material to the hydrochloric acid solution is (0.05~0.5):1.

[0090] Research has shown that controlling the concentration of hydrochloric acid solution within the range of 0.2~2 mol / L of water-soluble template agent can achieve mild and controllable etching of the metal oxides generated by the template agent conversion. This concentration range can effectively unblock the main pores and ensure the smooth flow of the mesoporous structure, while retaining an appropriate amount of metal oxides in the carbon skeleton as nucleation sites for subsequent silicon infiltration. This balances the integrity of the pore structure and the interface composite effect, thereby improving the structural stability and electrochemical performance of silicon-carbon materials.

[0091] Fourthly, the present invention provides a method for preparing a silicon-carbon material, comprising the following steps: Step 1: The pitch-based mesoporous carbon obtained in the first aspect or the pitch-based mesoporous carbon obtained by the preparation method provided in the third aspect is subjected to gas-phase chemical reaction to precipitate silica, thereby obtaining an intermediate product. Step 2: Carbon coating of the intermediate product is carried out by gas-phase chemical process to obtain the silicon-carbon material.

[0092] In practical applications, vapor-phase chemical reaction silicon deposition typically employs fluidized bed silicon infiltration and fluidized bed carbon coating processes, as follows: The silica infiltration process was carried out sequentially using a fluidized bed reactor: first, pitch-based mesoporous carbon was added to the reactor, forming a stable fluidized system under the action of a carrier gas. A silicon source gas was then introduced at high temperature, allowing silicon vapor and active silicon groups to diffuse to all exposed surfaces of the carbon skeleton (including the inner walls of the pores and the outer surfaces of the particles) and uniformly deposit to form a silicon phase. The silica infiltration temperature was 420–500 °C; the silicon source gas was SiH4-N2, with a SiH4 content of 20 vol%–30 vol%, and the deposition time was 1–24 h.

[0093] Carbon coating was performed using a fluidized bed process: After silicon infiltration, the particles were kept in a fluidized state and acetylene gas was introduced. After high-temperature pyrolysis, a continuous and dense carbon coating layer was formed on the entire surface of the silicon phase and carbon skeleton. The carbon coating temperature was 550~650℃; the carbon source gas was C2H2-N2, with a C2H2 content of 15%~25%; and the carbon coating time was 1~24h.

[0094] Fluidized bed technology allows silicon and carbon source precursors to fully contact the material, achieving uniform loading of silicon on the inner and outer surfaces of the carbon skeleton, while obtaining a fully coated surface carbon structure, effectively avoiding particle agglomeration, and significantly improving the compositional uniformity and interfacial bonding stability of silicon-carbon composite materials.

[0095] Fifthly, the present invention provides a battery comprising the silicon-carbon material described in the second aspect.

[0096] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0097] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0098] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0099] Example 1: A method for preparing a silicon-carbon material includes the following steps: Step 1: Weigh 100g of water, add 8g of ammonium persulfate, 50g of emulsified asphalt with a solid content of 30% and 10g of magnesium citrate, and add 0.5M hydrochloric acid to adjust the pH of the reaction system to 2. Mix well to obtain the mixture.

[0100] Step 2: Stir the above mixture at 80℃ and 200rpm for 12 hours, then heat it to 120℃ for drying to remove moisture and obtain intermediate material.

[0101] Step 3: The intermediate material is initially crushed into coarse powder with a Dv50 of 1 mm, transferred to a crucible, and subjected to segmented heat treatment under a nitrogen atmosphere: the temperature is increased to 350℃ at 5℃ / min and held for 3 hours to soften and flow the asphalt to fully fill the voids; the temperature is further increased to 1000℃ and held for 3 hours to complete high-temperature carbonization, so that the carbon source structure of the asphalt is rearranged to form a carbon skeleton, and a solid material is obtained.

[0102] Step 4: The solid material is crushed by airflow to a Dv50 of 8 μm, Dmax < 22 μm, and diameter < 1; then the obtained powder is placed in 7 times its volume of 1 mol / L hydrochloric acid solution and soaked at 80℃ for 2 hours, and then washed 3 times with pure water to obtain pitch-based mesoporous carbon.

[0103] Step 5: The obtained asphalt-based mesoporous carbon is put into a fluidized bed and subjected to silicon infiltration treatment and acetylene carbon coating treatment in sequence to obtain the silicon-carbon material.

[0104] Figure 1 The image shows the DFT pore size distribution curve of the pitch-based mesoporous carbon obtained in step 4 of Example 1. This material exhibits a narrow and concentrated pore size distribution, dominated by micropores and mesopores: the differential curve shows a main peak for micropores near 0.5 nm, while a significant secondary peak for mesopores exists at 2-3 nm, with no obvious macropore distribution; the integral pore volume curve indicates that the pore volume is mainly contributed by channels of 0.5-10 nm, with a high proportion of mesopores. This structure combines the high specific surface area characteristics of micropores with the buffer space of mesopores, providing sufficient ion transport channels and volume expansion buffer space for the subsequent uniform loading of silicon.

[0105] Analysis using NLDFT method Figure 1 The data obtained from the analysis are shown in Table 1.

[0106] Table 1. Pore volume statistics of the pitch-based mesoporous carbon obtained in step 4 of Example 1. Depend on Figure 1 As shown in Table 1, the carbon framework prepared by the process provided by the present invention has a highly concentrated pore structure between micropores (0.3~2nm) and small mesopores (2~5nm), which together account for 94.87% of the pore volume, while macropores and mesopores larger than 5nm are very rare.

[0107] The total pore volume of the solid material prepared in step 3 of Example 1, calculated by nitrogen physical adsorption (BET) combined with the NLDFT model, is 0.60 mL / g, and the total volume of all pores is 1.1986 mL / g. This is a high pore volume level, which theoretically can support a very high content of silicon while providing sufficient buffer space for the volume expansion of silicon.

[0108] Figure 2 The image shows a SEM image of the silicon-carbon material prepared in Example 1. Figure 2 It can be seen that the particles have regular morphology, are irregularly shaped, have uniform particle size distribution, and no obvious agglomeration. The particle surface is smooth and intact, with no obvious cracks or damage, indicating that the material structure has good stability. Moreover, the carbon coating layer is continuous and uniform, which is beneficial to improving the electrode processing performance and structural stability during cycling.

[0109] Figure 3 This is a TEM image of the silicon-carbon material prepared in Example 1. Figure 3 It can be seen that the material matrix is ​​a typical amorphous soft carbon structure, with no obvious silicon crystal phase agglomeration or long-range ordered lattice stripes, indicating that silicon is uniformly dispersed in the carbon skeleton at the nanoscale. The carbon matrix has abundant nanoscale pores, and the loose and uniform structure provides sufficient buffer space for the volume expansion of silicon, while shortening the lithium ion diffusion path and improving the rate performance and cycle stability of the material.

[0110] Figure 4 The image shows the XRD pattern of the silicon-carbon material prepared in Example 1. Figure 4 As can be seen, the XRD pattern of the silicon-carbon material prepared in Example 1 exhibits typical characteristics of amorphous carbon: a broad peak appears at 2θ of 20°~25°, corresponding to the (002) crystal plane diffraction of soft carbon, indicating that the carbon matrix is ​​an amorphous structure with a low degree of graphitization, belonging to soft carbon material; at the same time, no obvious crystalline silicon characteristic diffraction peaks (such as 2θ of 28.4° and 47.3°) appear in the pattern, indicating that silicon is uniformly dispersed in the carbon skeleton in the form of amorphous or ultra-nanocrystalline, without forming obvious silicon crystal phase agglomeration, which is beneficial to alleviate the volume expansion of silicon and improve the cycling stability of the material.

[0111] Example 2: A method for preparing a silicon-carbon material includes the following steps: Step 1: Weigh 100g of water, add 8g of ammonium persulfate, 40g of emulsified asphalt with a solid content of 20% and 8g of magnesium chloride, and mix evenly to obtain the mixture.

[0112] Step 2: Stir the above mixture at 200 rpm for 12 hours at room temperature, then heat it to 80°C for drying to remove moisture and obtain intermediate material.

[0113] Step 3: The intermediate material is initially crushed into coarse powder with a Dv50 of 1 mm, transferred to a crucible, and subjected to segmented heat treatment under a nitrogen atmosphere: the temperature is increased to 200℃ at 5℃ / min and held for 6 hours to soften and flow the asphalt to fully fill the voids; the temperature is further increased to 600℃ and held for 6 hours to complete high-temperature carbonization, so that the carbon source structure of the asphalt is rearranged to form a carbon skeleton, and a solid material is obtained.

[0114] Step 4: The solid material is crushed by airflow to a Dv50 of 8 μm, Dmax < 22 μm, and diameter < 1; then the obtained powder is placed in 7 times the volume of 0.5 mol / L hydrochloric acid solution and soaked at 20℃ for 24 h, and then washed with pure water 3 times to obtain pitch-based mesoporous carbon.

[0115] Step 5: The obtained asphalt-based mesoporous carbon is put into a fluidized bed and subjected to silicon infiltration treatment and acetylene carbon coating treatment in sequence to obtain the silicon-carbon material.

[0116] Example 3: A method for preparing a silicon-carbon material includes the following steps: Step 1: Weigh 100g of water, add 8g of ammonium persulfate, 50g of emulsified asphalt with a solid content of 40% and 15g of aluminum lactate, and mix evenly to obtain the mixture.

[0117] Step 2: Stir the above mixture at 50℃ and 200rpm for 15 hours, then heat it to 120℃ for drying to remove moisture and obtain intermediate material.

[0118] Step 3: The intermediate material is initially crushed into coarse powder with a Dv50 of 1 mm, transferred to a crucible, and subjected to segmented heat treatment under a nitrogen atmosphere: the temperature is increased to 200℃ at 5℃ / min and held for 6 hours to soften and flow the asphalt to fully fill the voids; the temperature is further increased to 600℃ and held for 6 hours to complete high-temperature carbonization, so that the carbon source structure of the asphalt is rearranged to form a carbon skeleton, and a solid material is obtained.

[0119] Step 4: The solid material is crushed by airflow to a Dv50 of 8 μm, Dmax < 22 μm, and diameter < 1; then the obtained powder is placed in 7 times the volume of 0.5 mol / L hydrochloric acid solution and soaked at 20℃ for 24 h, and then washed with pure water 3 times to obtain pitch-based mesoporous carbon.

[0120] Step 5: The obtained asphalt-based mesoporous carbon is put into a fluidized bed and subjected to silicon infiltration treatment and acetylene carbon coating treatment in sequence to obtain the silicon-carbon material.

[0121] Example 4: A method for preparing a silicon-carbon material includes the following steps: Step 1: Weigh 100g of water, add 8g of ammonium persulfate, 50g of emulsified asphalt with a solid content of 30% and 10g of magnesium citrate, and add 0.5M hydrochloric acid to adjust the pH of the reaction system to 2. Mix well to obtain the mixture.

[0122] Step 2: Stir the above mixture at 80℃ and 200rpm for 12 hours, then heat it to 120℃ for drying to remove moisture and obtain intermediate material.

[0123] Step 3: The intermediate material is initially crushed into coarse powder with a Dv50 of 1 mm, transferred to a crucible, and subjected to segmented heat treatment under a nitrogen atmosphere: the temperature is increased to 200℃ at 5℃ / min and held for 6 hours to soften and flow the asphalt to fully fill the voids; the temperature is further increased to 600℃ and held for 6 hours to complete high-temperature carbonization, so that the carbon source structure of the asphalt is rearranged to form a carbon skeleton, and a solid material is obtained.

[0124] Step 4: The solid material is crushed by airflow to a Dv50 of 8 μm, Dmax < 22 μm, and diameter < 1. The resulting solid particles are then heated in heat transfer oil at 250°C for 6 hours, cooled and allowed to stand for solid-liquid separation. The resulting powder is then added to 7 times its volume of 0.5 mol / L hydrochloric acid solution and soaked at 20°C for 24 hours. Finally, it is washed three times with pure water to obtain asphalt-based mesoporous carbon.

[0125] Step 5: The obtained asphalt-based mesoporous carbon is put into a fluidized bed and subjected to silicon infiltration treatment and acetylene carbon coating treatment in sequence to obtain the silicon-carbon material.

[0126] Figure 5 The image shows a SEM image of the silicon-carbon material prepared in Example 4. Figure 5 As can be seen from the figure, the material particles are regularly spherical with smooth surfaces and fine wrinkles. The overall particle size distribution is uniform and narrow, with no obvious agglomeration. The high sphericity of the particles indicates that the heat transfer oil spheroidization process effectively achieves the spheroidization modification of carbon materials, which can improve the tap density and electrode processing performance of the material. At the same time, it is beneficial to optimize the electrolyte wettability and improve the cycle stability and rate performance of silicon-carbon anodes.

[0127] Example 5: A method for preparing a silicon-carbon material includes the following steps: Step 1: Weigh 100g of water, add 8g of ammonium persulfate, 160g of emulsified asphalt with a solid content of 5% and 8g of aluminum lactate, and mix evenly to obtain the mixture.

[0128] Step 2: Stir the above mixture at 55℃ and 200rpm for 12 hours, then heat it to 120℃ for drying to remove moisture and obtain intermediate material.

[0129] Step 3: The intermediate material is initially crushed into coarse powder with a Dv50 of 1 mm, transferred to a crucible, and subjected to segmented heat treatment under a nitrogen atmosphere: the temperature is increased to 550℃ at 5℃ / min and held for 3 hours to soften and flow the asphalt to fully fill the voids; the temperature is further increased to 1500℃ and held for 6 hours to complete high-temperature carbonization, so that the carbon source structure of the asphalt is rearranged to form a carbon skeleton, and a solid material is obtained.

[0130] Step 4: The solid material is crushed by airflow to a Dv50 of 8 μm, Dmax < 22 μm, and diameter < 1; then the obtained powder is placed in 7 times its volume of 2 mol / L hydrochloric acid solution and soaked at 60℃ for 24 h, and then washed 3 times with pure water to obtain pitch-based mesoporous carbon.

[0131] Step 5: The obtained asphalt-based mesoporous carbon is put into a fluidized bed and subjected to silicon infiltration treatment and acetylene carbon coating treatment in sequence to obtain the silicon-carbon material.

[0132] Comparative Example 1: A method for preparing a silicon-carbon material includes the following steps: Step 1: Weigh 100g of pyridine, 50g of emulsified asphalt with a solid content of 30% and 10g of magnesium citrate, and mix them evenly to obtain the mixture.

[0133] Step 2: After stirring the above mixture at 80℃ and 200rpm for 12 hours, dry it to remove moisture and obtain intermediate material.

[0134] Step 3: The intermediate material is initially crushed into coarse powder with a Dv50 of 1 mm, transferred to a crucible, and subjected to segmented heat treatment under a nitrogen atmosphere: the temperature is increased to 350℃ at 5℃ / min and held for 3 hours to soften and flow the asphalt to fully fill the voids; the temperature is further increased to 1000℃ and held for 3 hours to complete high-temperature carbonization, so that the carbon source structure of the asphalt is rearranged to form a carbon skeleton, and a solid material is obtained.

[0135] Step 4: The solid material is crushed by airflow to a Dv50 of 8 μm, Dmax < 22 μm, and diameter < 1; then the obtained powder is placed in 7 times the volume of 1 mol / L hydrochloric acid solution and soaked at 80℃ for 2 hours, and then washed 3 times with pure water to obtain pitch-based mesoporous carbon.

[0136] Step 5: The obtained asphalt-based mesoporous carbon is put into a fluidized bed and subjected to silicon infiltration treatment and acetylene carbon coating treatment in sequence to obtain the silicon-carbon material.

[0137] Comparative Example 2: A method for preparing a silicon-carbon material includes the following steps: Step 1: Weigh 100g of water, add 8g of ammonium persulfate, 50g of emulsified asphalt with a solid content of 30% and 10g of magnesium citrate, and add 0.5M hydrochloric acid to adjust the pH of the reaction system to 2. Mix well to obtain the mixture.

[0138] Step 2: After stirring the above mixture at 80°C for 12 hours, dry it to remove moisture and obtain intermediate material.

[0139] Step 3: The intermediate material is initially crushed into coarse powder with a Dv50 of 1 mm, transferred to a crucible, and subjected to segmented heat treatment under a nitrogen atmosphere: the temperature is increased to 1000℃ at 5℃ / min and held for 3 hours to complete high-temperature carbonization, so that the carbon source structure of the asphalt is rearranged to form a carbon skeleton, and a solid material is obtained.

[0140] Step 4: The solid material is crushed by airflow to a Dv50 of 8 μm, Dmax < 22 μm, and diameter < 1; then the obtained powder is placed in 7 times the volume of 1 mol / L hydrochloric acid solution and soaked at 80℃ for 2 hours, and then washed 3 times with pure water to obtain pitch-based mesoporous carbon.

[0141] Step 5: The obtained asphalt-based mesoporous carbon is put into a fluidized bed and subjected to silicon infiltration treatment and acetylene carbon coating treatment in sequence to obtain the silicon-carbon material.

[0142] Comparative Example 3: A method for preparing a silicon-carbon material includes the following steps: Step 1: Weigh 100g of water, add 8g of ammonium persulfate, 50g of emulsified asphalt with a solid content of 30% and 10g of magnesium citrate, and add 0.5M hydrochloric acid to adjust the pH of the reaction system to 2. Mix well to obtain the mixture.

[0143] Step 2: After stirring the above mixture at 80℃ and 200rpm for 12 hours, dry it to remove moisture and obtain intermediate material.

[0144] Step 3: The intermediate material is initially crushed into coarse powder with a Dv50 of 1 mm, transferred to a crucible, and subjected to segmented heat treatment under a nitrogen atmosphere: the temperature is increased to 1000℃ at 5℃ / min and held for 3 hours to complete high-temperature carbonization, so that the carbon source structure of the asphalt is rearranged to form a carbon skeleton, and a solid material is obtained.

[0145] Step 4: The solid material is crushed by airflow to a Dv50 of 8 μm, Dmax < 22 μm, and diameter < 1. The resulting powder is then placed in a mixed acid solution of 7 times its volume (the mixed acid solution is prepared by mixing 0.5 M HCl and 0.5 M HF in a volume ratio of 1:3), soaked at 80 °C for 2 h, and then washed 3 times with pure water to obtain pitch-based mesoporous carbon.

[0146] Step 5: The obtained asphalt-based mesoporous carbon is put into a fluidized bed and subjected to silicon infiltration treatment and acetylene carbon coating treatment in sequence to obtain the silicon-carbon material.

[0147] Comparative Example 4: A method for preparing a silicon-carbon material includes the following steps: Step 1: Weigh 100g of water, add 50g of emulsified asphalt with a solid content of 30% and 10g of magnesium citrate, and add 0.5M hydrochloric acid to adjust the pH of the reaction system to 2. Mix well to obtain the mixture.

[0148] Steps 2 through 5 are the same as in Example 1.

[0149] The asphalt-based mesoporous carbon prepared in Examples 1-5 and Comparative Examples 1-4 were passed through a 200-mesh sieve and then subjected to the following tests.

[0150] Micropore analysis: Tested using a Bester specific surface area analyzer; Powder resistivity testing: After compacting the asphalt-based mesoporous carbon powder with a pressure of 4.0 MPa, the powder resistivity was measured using an ST2722-SD four-terminal powder resistivity tester. Metal content testing method: ICP-OES was used to test the metal content; the test data are shown in Table 2.

[0151] Table 2 Performance parameters of pitch-based mesoporous carbon obtained in Examples 1-5 and Comparative Examples 1-4 Examples 1-5 describe the preparation of asphalt-based mesoporous carbon through ammonium persulfate oxidation modification in an aqueous system, with the template agent dispersed in water. Following segmented heat treatment, precise crushing, and targeted acid washing, the resulting carbon exhibits significant comprehensive advantages: pore volumes are consistently maintained between 0.80 and 0.92 cm³. 3 The surface area is relatively high, with an average pore size concentrated in the mesoporous range of 3.2~4.0 nm, and a static specific surface area of ​​1002~1312 cm³. 2 / g, powder resistivity is only 45~55mΩ The metal residue (magnesium or aluminum) is controlled within a reasonable range (8900~11000ppm), which ensures the regularity and connectivity of the mesoporous structure, providing sufficient space for subsequent silicon infiltration, and also has good conductivity. At the same time, the moderate metal residue does not have a negative impact on the core performance of the material. The spheroidization treatment in Example 4 further optimizes the particle morphology and structural stability, and as a whole, it meets the comprehensive requirements of composite silicon-carbon anode for pore structure, conductivity and dispersibility.

[0152] Comparative Example 1 used pyridine as the organic solvent and did not use a strong oxidant. A clear comparison of the data from Example 1 and Comparative Example 1 shows that the pore volume of Example 1 is much higher than that of Comparative Example 1, the pore size distribution is narrower and more concentrated, the static specific surface area is significantly better than that of Comparative Example 1, and the powder resistivity is significantly lower than that of Comparative Example 1. This suggests that while existing technologies using organic solvents can promote asphalt dispersion, they cannot achieve uniform dispersion of the template agent, leading to significant phase separation during preparation and affecting the pore size distribution. In contrast, the oxidative modification of ammonium persulfate in the aqueous system can improve the hydrophilicity and dispersion stability of the asphalt, while the solubilizing effect of hydrochloric acid ensures uniform dispersion of the template agent. Together, these two factors construct a regular mesoporous structure, thereby optimizing the material's electrical conductivity.

[0153] Example 1 employed a segmented heat treatment process, while Comparative Example 2 did not undergo low-temperature segmented treatment. Data shows that Example 1 exhibited a narrower and more controllable pore size distribution, with a significantly higher static specific surface area than Comparative Example 1. Although Comparative Example 2 had a slightly higher pore volume, its pore size distribution was disordered and its static specific surface area was insufficient, while its electrical conductivity was comparable to Example 1. This indicates that the low-temperature stage (350℃) heat preservation is crucial in segmented heat treatment: this process allows the asphalt to fully soften and flow, uniformly filling the gaps in the template, avoiding direct high-temperature carbonization that leads to rapid decomposition and shrinkage of the asphalt, which in turn causes pore structure collapse or uneven pore size. Comparative Example 2, lacking a low-temperature dispersion and filling step, had a slightly higher pore volume but larger and wider pore size distribution, failing to form a regular mesoporous structure. This would affect the uniformity and stability of silicon loading during subsequent silicon infiltration.

[0154] Example 1 used hydrochloric acid washing, which retained a suitable amount of magnesium, while Comparative Example 3 used a mixed acid of hydrochloric acid and hydrofluoric acid to almost completely remove the magnesium. Both examples have similar pore structure parameters, but the powder resistivity of Example 1 is only 50 mΩ. cm, far superior to the 500mΩ of Comparative Example 3. cm. This indicates that moderate retention of Mg in pitch-based mesoporous carbon is beneficial for maintaining the structural strength and good conductivity of the carbon skeleton, reducing impedance and improving electrode stability; while excessive acid washing to remove all metals may damage the carbon material structure and conductive network, leading to a significant decrease in conductivity, demonstrating the positive effect of appropriate Mg residue on material structure and conductivity.

[0155] Comparing Example 1 and Comparative Example 4 demonstrates that the addition of ammonium persulfate is key to achieving excellent pore structure and electrical conductivity. Example 1 utilizes ammonium persulfate to oxidize and modify emulsified asphalt, achieving uniform dispersion of the carbon precursor and template agent in the aqueous phase. After carbonization, an ideal mesoporous carbon framework with high pore volume, high specific surface area, and concentrated pore size is formed, resulting in a powder resistivity as low as 50 mΩ·cm. In contrast, Comparative Example 4, lacking the addition of ammonium persulfate, did not modify the asphalt, leading to a collapsed pore structure, large pore size, a sharp decrease in specific surface area, and a significant deterioration in electrical conductivity.

[0156] Using the silicon-carbon materials obtained in Examples 1-4 and Comparative Examples 1-3 as negative electrode active materials, negative electrode sheets were prepared respectively. The negative electrode sheets were used to prepare CR2032 coin cells using conventional methods, and the electrical performance of the cells was tested.

[0157] Particle size testing: Malvern 3000 was used for testing, and the particle size distribution was calculated as (Dv90 - Dv10) / Dv50. Silicon content test: Place silicon carbide powder of mass M1 in a muffle furnace and calcine it in air atmosphere for 3 hours to obtain the remaining mass M2. Soak the remaining powder in 2M alkaline solution at 80℃ for 2 hours. Dry the remaining precipitate and weigh it to obtain mass M3. The silicon content result is: 0.4674×(M3-M2) / M1×100%, where 0.4674 is the conversion factor of Si from SiO2 (Si / SiO2=28 / 60≈0.4674).

[0158] Preparation of the negative electrode (working electrode): Silicon-carbon material, Super P, SBR, and CMC were mixed evenly in deionized water at a mass ratio of 90:5:3:2. The solid content was adjusted to about 50%, and the mixture was coated onto copper foil. After vacuum drying at 80℃ for 12 h, the mixture was rolled and punched to obtain a circular negative electrode with a diameter of 14 mm. The active material loading was controlled at 3.5~4.5 mg / cm³. 2 .

[0159] Half-cell assembly: Assemble CR2032 coin cells in a glove box, using lithium metal sheets as the counter electrode, polypropylene microporous membranes as the separator, and LiPF6 dissolved in a mixture of ethyl carbonate (EC) and diethyl carbonate (DEC) (volume ratio EC∶DEC=1∶1), with a LiPF6 concentration of 1mol / L.

[0160] The battery was tested for charge and discharge using the LAND battery testing system.

[0161] Cyclic specific capacity and initial efficiency test: After the CR2032 coin cell was left to stand for 6 hours, it was discharged at 0.1C to 0.005V, and the specific capacity was recorded as Q1; then it was discharged at a constant voltage of 0.005V until the current cutoff was 0.01C, and the specific capacity was recorded as Q2; after standing for 5 minutes, it was charged at a constant current of 0.1C to 0.8V, and the specific capacity was recorded as Q3; after standing for 5 minutes, it was charged at a constant current of 0.1C to 1.5V, and the specific capacity was recorded as Q4; after standing for 5 minutes, it was discharged at a constant current of 1.0C to 0.005V, and the specific capacity was recorded as Q5; after standing for 2 hours, the thickness of the negative electrode sheet was measured sequentially, and the average value was recorded as h1. Another coated and dried electrode sheet was taken, and the thickness of the negative electrode sheet at 5 points was measured, and the average value was recorded as h2. The initial lithium delithiation specific capacity is the specific capacity (or mass specific capacity) of the electrode material, and the ratio of the initial lithium delithiation capacity to the initial lithium insertion capacity is the initial coulombic efficiency of the battery.

[0162] 0.8V first efficiency = Q3 / (Q1+Q2)×100%; 1.5V initial efficiency = (Q3 + Q4) / (Q1 + Q2) × 100%; 1C rate discharge retention rate = Q5 / (Q3+Q4)×100%; Lithium intercalation expansion ratio = (h2-h1) / h1×100%; Capacity retention test: Three cells were taken, allowed to stand for 5 minutes, then discharged at 0.1C constant current and constant voltage to 0.005V, allowed to stand for 5 minutes, discharged at 0.02C to 0.005V, and charged at 0.1C constant current and constant voltage to 1.5V; allowed to stand for 5 minutes, then discharged at 0.25C to 0.005V; allowed to stand for 5 minutes, then charged at 0.25C constant current to 1.5V, and cycled 50 times at a rate of 0.25C. The specific capacity of the 50th cycle was divided by the charging capacity of the 1st cycle, and multiplied by 100% to calculate the specific capacity retention rate; the test data are shown in Table 3.

[0163] Table 3. Silicon content of silicon-carbon materials prepared in Examples 1-5 and Comparative Examples 1-4, and electrochemical data of batteries composed of silicon-carbon materials. The silicon-carbon materials prepared in Examples 1-5 exhibit both high capacity and high initial efficiency, excellent rate capability and cycle retention, and controllable expansion. Among them, Example 1 shows more uniform pore size and more regular pore walls, resulting in the best overall electrochemical performance. This demonstrates that the preparation process provided by this invention can achieve better dispersion of carbon source precursors and template agents, thereby producing uniform pore distribution, narrow pore size distribution, and a high proportion of micropores and mesopores. This results in higher consistency of silicon-carbon during charge and discharge, uniform expansion of silicon-carbon, and stronger stress buffering.

[0164] Comparing Examples 1 and 4, it can be seen that the spherical shape of the material has little impact on the material performance, only showing a lower performance in the first effect. This may be due to the smaller relative contact area of ​​the spheres under the same formulation. However, the spherical shape gives the material higher consistency, thus further reducing the full-fill expansion ratio.

[0165] Comparative analysis of the data from Example 1 and Comparative Example 1 revealed that Comparative Example 1 used pyridine instead of water as a solvent and did not add ammonium persulfate, lacking a strong oxidant for the oxidative modification of the asphalt. This resulted in insufficient formation of oxygen-containing functional groups in the carbon precursor to effectively complex magnesium ions, and consequently, the inability to generate a uniform and abundant mesoporous structure after carbonization. This poorly developed carbon framework could not provide sufficient silicon deposition sites during subsequent silicon infiltration, resulting in a silicon content of only 35.1% (compared to 51.1% in Example 1), leading to a V0.8. The specific capacity (1300 vs 1787.8 mAh / g) and the first-charge efficiency at 0.8V (78.1% vs 86.1%) are significantly lower. At the same time, due to the lack of mesoporous buffer space, the volume expansion of silicon particles during charging and discharging cannot be effectively contained, and the damage to the electrode structure is aggravated. Therefore, the 1C rate (53.1% vs 66.0%) and specific capacity retention (70.1% vs 95.2%) are significantly worse than those of Example 1, and the full-charge expansion ratio (69.1% vs 62.1%) is also higher.

[0166] Comparative analysis of the data from Example 1 and Comparative Example 2 revealed that Comparative Example 2 omitted the low-temperature holding stage in the carbonization process, directly raising the temperature to 1000℃ at 5℃ / min and holding it for 3 hours. This one-step carbonization process resulted in the asphalt rapidly heating and solidifying before fully filling the internal voids of the particles when it softened and flowed at around 350℃, failing to form a continuous and dense carbon skeleton and a uniform mesoporous network. Although the silicon content (48.6%) was not significantly different from that of Example 1 (51.1%), the specific capacity (1) was 0.8V. The specific capacity retention (700mAh / g) and first-charge efficiency (85.1%) are also quite close. However, due to poor connectivity of the pore structure and insufficient pore wall strength, it cannot effectively buffer the volume expansion of silicon during cycling, resulting in stress concentration and structural collapse inside the electrode. Therefore, the specific capacity retention (76.1% vs 95.2%) is significantly reduced, the full charge expansion ratio (80.1% vs 59.1%) is greatly increased, and the 1C rate performance (52.1% vs 66.0%) is also significantly degraded due to the obstructed ion transport channels.

[0167] Comparative analysis of the data from Example 1 and Comparative Example 3 showed that Comparative Example 3 had a similar silicon content (50.9% vs 51.1%), Dv50, and pitch to Example 1. The specific capacity (1781.2 mAh / g) and first-efficiency (85.2%) were also comparable to those of Example 1 (86.1%). The specific capacity retention (93.1%) was slightly lower than that of Example 1, but the difference was not significant. However, Comparative Example 3 used a mixed acid of HF and HCl (volume ratio 3:1) in the pickling step. The mixed acid used in Comparative Example 3 almost completely removed magnesium, resulting in a significant decrease in rate performance. This indicates that an appropriate amount of residual Mg / Al metal can optimize the conductivity and interface characteristics of carbon materials and improve rate performance.

[0168] Comparative analysis of the data from Example 1 and Comparative Example 4 revealed that the oxidative modification effect of ammonium persulfate has a decisive influence on the electrochemical performance of silicon-carbon materials. In Example 1, the addition of ammonium persulfate achieved oxidative modification of asphalt and uniform dispersion with the template agent in the aqueous phase. After carbonization, an ideal carbon framework with high pore volume, high specific surface area, and concentrated pore size (micropores + small mesopores) was formed, providing ample deposition sites and volume expansion buffer space for silicon. Therefore, the silicon content reached 51.1%, the specific capacity at 0.8V reached 1787.8 mAh / g, the first-charge efficiency at 0.8V was 86.1%, the 1C rate retention rate reached 66.0%, the specific capacity retention rate after 50 cycles reached 95.2%, and the full-charge expansion ratio was controlled at 59.1%. In contrast, Comparative Example 4, lacking ammonium persulfate and with unmodified asphalt, suffered from a collapsed pore structure, large pore size (10.0 nm), and extremely low specific surface area after carbonization. This resulted in an inability to effectively load and confine silicon nanoparticles, leading to a silicon content of only 37.1%, a low 0.8V specific capacity of 1005 mAh / g, a first-charge efficiency of only 72.1%, and significantly deteriorated rate performance and cycle stability (1C rate retention of only 43.1% and cycle retention of only 68.1%). Furthermore, the lack of mesoporous buffer space prevented the effective containment of silicon volume expansion, resulting in a full-charge expansion ratio as high as 90.1%. These data clearly demonstrate that the oxidative modification effect of ammonium persulfate is a crucial prerequisite for constructing a high-performance mesoporous carbon framework, achieving high silicon loading, and ensuring the excellent electrochemical performance of silicon-carbon anodes.

[0169] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A pitch-based mesoporous carbon, characterized in that, The pitch-based mesoporous carbon contains multiple channels, the average pore size of which is 2-5 nm, the pore volume of channels with a pore size of 0.5-5 nm is V1, and the total pore volume is V. 总 V1∶V 总 ≥90%.

2. The pitch-based mesoporous carbon as described in claim 1, characterized in that, The total pore volume of the pitch-based mesoporous carbon is 0.5~1.5 cm³. 3 / g; the Dv50 of the pitch-based mesoporous carbon is 1~20μm; the diameter of the pitch-based mesoporous carbon is 0.5~2.

0.

3. The pitch-based mesoporous carbon as described in claim 1, characterized in that, The pitch-based mesoporous carbon contains a metal element M, which is any one or both of Mg and Al; the content of the metal element M is 2000~15000ppm.

4. A silicon-carbon material, characterized in that, The invention comprises as described in any one of claims 1 to 3, pitch-based mesoporous carbon, silicon, and a carbon coating layer, wherein the silicon is distributed in the pores of the pitch-based mesoporous carbon, and the carbon coating layer covers at least a portion of the surface of the particles formed by the pitch-based mesoporous carbon and the silicon.

5. The silicon-carbon material as described in claim 4, characterized in that, The silicon-carbon material contains 30% to 70% silicon by mass; the dynamic specific gravity of the silicon-carbon material is 0.7 to 20 cm⁻¹. 2 / g.

6. A method for preparing pitch-based mesoporous carbon, characterized in that, Includes the following steps: Step 1: Add ammonium persulfate, emulsified asphalt, and water-soluble template agent to water to obtain a mixture; Step 2: Heat and stir the mixture, then dry it to obtain the intermediate material; Step 3: After crushing the intermediate material, heat-treat it under a nitrogen atmosphere to obtain a solid material; Step 4: The solid material is crushed, removed from the template, and washed in sequence to obtain the asphalt-based mesoporous carbon.

7. The method for preparing pitch-based mesoporous carbon as described in claim 6, characterized in that, In step 1, the mass ratio of ammonium persulfate, emulsified asphalt, and water-soluble template agent is 1:(1~2.5):(1~2.5); the solid content of emulsified asphalt is 5wt%~40wt%. The ratio of the total mass of ammonium persulfate, emulsified asphalt, and water-soluble template agent to the mass of water is (5wt%~50wt%):1; the water-soluble template agent is any one or more of magnesium lactate, magnesium citrate, magnesium chloride, magnesium sulfate, aluminum lactate, aluminum citrate, and water-based silica sol. In step 2, the heating temperature is 20~80℃; the stirring speed is 50~500rpm; the stirring time is 1~30h; and the drying temperature is 80~180℃. In step 3, the intermediate material is crushed using an airflow crushing process, and the particle Dv50 of the crushed particles is 7~10μm; the heat treatment includes two stages: the first stage is held at 200~550℃ for 1~10h; the second stage is held at 600~1500℃ for 1~10h. In step 4, the crushed solid material is placed in hydrochloric acid solution and soaked at 20~90℃ for 4~24h, and then washed with pure water 2~4 times to obtain the asphalt-based mesoporous carbon; the concentration of hydrochloric acid solution is 0.2~2mol / L; the mass ratio of solid material to hydrochloric acid solution is 0.05~0.

5.

8. The method for preparing pitch-based mesoporous carbon as described in claim 6 or 7, characterized in that, The water-soluble template agent is any one or more of magnesium chloride, magnesium sulfate, aluminum lactate, and water-based silica sol.

9. A method for preparing a silicon-carbon material, characterized in that, Includes the following steps: Step 1: The pitch-based mesoporous carbon according to any one of claims 1 to 3 or the pitch-based mesoporous carbon prepared by the preparation method according to any one of claims 6 to 8 is subjected to gas-phase chemical reaction to precipitate silica, thereby obtaining an intermediate product; Step 2: Carbon coating of the intermediate product is carried out by gas-phase chemical process to obtain the silicon-carbon material.

10. A battery comprising the silicon-carbon material according to any one of claims 4 to 5 or the silicon-carbon material prepared by the preparation method according to claim 9.

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