Preparation method of sodium ion battery hard carbon material

Abstract

The invention relates to a sodium ion battery hard carbon material preparation method, which comprises: (S1) uniformly mixing an asphalt substance and a heteroatom-rich organic matter to obtain a mixed precursor I; (S2) carrying out heat treatment on the mixed precursor in an oxidizing atmosphere, cooling, and wrapping the heteroatom-rich organic matter in the asphalt melting process to obtain a mixed precursor II; and (S3) calcining, cooling, grinding, washing and drying the mixed precursor II in an inert atmosphere or a hydrocarbon atmosphere to obtain the amorphous sodium ion battery negative electrode material. The negative electrode material obtained by the preparation method disclosed by the invention has high capacity and high energy density, a carbon material which is low in cost, simple in preparation process, adjustable in disorder degree, high in carbon yield and suitable for large-scale production is provided, and the carbon material is applied to the sodium ion secondary battery as the negative electrode material.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a method for preparing a hard carbon material for sodium-ion batteries. Background Technology

[0002] With the gradual depletion of fossil fuels, the development and utilization of new energy carriers are receiving increasing attention. Secondary batteries, as a primary chemical energy storage device, play a crucial role in this field. Replacing fossil fuels with electricity as the main energy source for transportation will significantly reduce greenhouse gas emissions. Improving various power grid systems by integrating them with renewable energy sources such as wind, solar, and geothermal energy will greatly enhance the efficiency of renewable energy utilization. Sodium-ion batteries, with their advantages of abundant, widely distributed, and low-cost sodium resources, compensate for the limitations of lithium-ion batteries, such as scarce resources, uneven distribution, and high costs, and have received widespread attention and extensive research in recent years. Developing high-performance electrode materials is crucial for the commercialization of sodium-ion batteries. To date, the development of some positive electrode materials has largely met application requirements, but negative electrode materials still constrain the practical application of sodium-ion batteries.

[0003] Among the reported sodium-ion battery anode materials, amorphous carbon materials have become the most promising anode materials due to their relatively low sodium storage potential, high sodium storage capacity, and good cycle stability. Fossil mineral precursors have significant advantages in the preparation of amorphous carbon materials, as they are inexpensive, have huge domestic reserves, and offer high carbonization yields, possessing strong commercial potential. However, the amorphous carbon materials obtained after calcination have high structural order and low porosity, which reduces the capacity in the low-voltage region, leading to a decrease in the overall battery energy density.

[0004] Taking pitch-based carbon materials as an example, during pitch pyrolysis, the main component, asphaltenes, polymerizes and rearranges into sheet-like aromatic fused ring structures, which then stack into sheets under van der Waals forces. Further heating increases the order and density of the carbon material, eventually transforming it into highly ordered graphite, which is unfavorable for sodium ion storage. We propose using heteroatom-rich organic compounds as pore-forming additives. During pyrolysis, these functionally rich organic molecules can decompose and release a large number of small molecules, thereby achieving in-situ etching of the carbon layer and forming pores. Unlike conventional pore-forming methods, this method does not require the introduction of difficult-to-remove inorganic oxides, thus eliminating the need for removal in subsequent steps. This simplifies the process and achieves "carbon-to-carbon, carbon-enhanced carbon," significantly improving the economy and sustainability of the preparation process. Simultaneously, air-atmosphere oxidation of asphaltenes polymerizes into randomly oriented mesophase carbon, inhibiting the ordered rearrangement of the carbon layer during calcination of pitch-based precursors. Overall, this improves the capacity in the low-pressure plateau region, promoting its large-scale application as a negative electrode in sodium-ion batteries. Summary of the Invention

[0005] To address the issue that the electrochemical performance of existing asphalt-based hard carbon anode materials cannot meet the demands of industrial batteries, this invention provides a sodium-ion battery anode material, its preparation method, and its application. It utilizes abundant and inexpensive fossil industrial waste products such as coal tar pitch, petroleum pitch, and mesophase pitch as raw materials. The materials undergo heat treatment in an oxidizing atmosphere to crosslink and polymerize with asphaltenes, inhibiting the polymerization and rearrangement of asphaltenes to form layered mesophase pitch. Furthermore, at least one oxygen-rich organic compound selected from biomass (camellia shells, pine cones, crustacean exoskeletons such as shrimp shells, and banana peels), polymers (urea-formaldehyde resin, epoxy resin), and small organic molecules (urea, citric acid, and potassium / sodium / magnesium citrate) is used. Through pyrolysis, volatile small molecules are formed, creating closed micropores and defects in the crosslinked polymerized carbon pitch, thus facilitating sodium-ion storage. This approach balances high capacity and high energy density, proposing a low-cost, simple-process, tunable-disorder, high-carbon-yield carbon material suitable for large-scale production, which is then applied as an anode material in sodium-ion secondary batteries.

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a sodium-ion battery anode material, comprising the following steps:

[0007] (S1) Mix asphalt-based substances with heteroatom-rich organic matter evenly to obtain mixed precursor I;

[0008] (S2) The mixed precursor is pressed into sheets, heat-treated in an oxidizing atmosphere, cooled and cooled, and the mixed precursor II is obtained by encapsulating the atom-rich organic matter during the asphalt melting process.

[0009] (S3) Mixed precursor II is calcined, cooled, ground, washed and dried under an inert atmosphere or a hydrocarbon atmosphere to obtain an amorphous sodium-ion battery anode material.

[0010] Further, in step (S1), the asphalt-like substance includes one or more mixtures of coal tar pitch, petroleum pitch, natural pitch, and mesophase pitch; the heteroatom-rich organic matter is selected from at least one of biomass (camellia shell, straw, coconut shell, crustacean exoskeleton such as shrimp shell, pine cone powder), polymers (epoxy resin, phenolic resin), and small organic molecules (urea, citric acid, and potassium / sodium / magnesium citrate); the mass ratio of the asphalt-like precursor to the heteroatom-rich organic matter is 1:0.5-1.

[0011] Furthermore, in step (S1), the asphalt-like substance is a mixture with asphaltene as the main component. In particular, the viscosity-average molecular weight range of the asphaltene is preferably 2000-5000 g / mol. This will limit the softening point of the asphalt to a certain extent, which is lower than the oxidation temperature of asphaltene and oxygen-rich organic matter. At the same time, it cannot volatilize in large quantities before softening. This places high demands on the composition and molecular weight of the asphalt, requiring it to fully soften and coat the biomass before oxidation.

[0012] Furthermore, the epoxy resin is a bisphenol A type epoxy resin or a glycidyl ester type epoxy resin, which has a high thermal decomposition temperature.

[0013] Further, in step (S1), the heteroatom-rich organic compound is a mixture of biomass, polymers and small organic molecules; preferably, the mass ratio of biomass, polymers and small organic molecules is 1:0.3-0.5:0.1-0.2.

[0014] The inventors discovered that a heteroatom-rich organic compound, formulated in a specific ratio of the three substances mentioned above, can form a richer pore structure when used as a pore modifier. Firstly, the organic compound rich in functional groups, especially oxygen-containing functional groups, can decompose into small gaseous molecules containing carbon dioxide at high temperatures. Under the high-temperature conditions of pyrolysis, these molecules react with the carbon layer inside the pitch-based hard carbon material, creating pores, defects, and heteroatom groups. This increases the defect rate on the surface and pore surfaces of the pitch-based carbon material. By increasing the work function of the carbon layer, it facilitates the reversible adsorption and storage of sodium metal clusters, thereby improving the electrochemical performance of the resulting negative electrode material. The heteroatom-rich organic compound, as described above, helps achieve a richer pore structure during subsequent pyrolysis. This is because different heteroatom-rich organic compounds release different types of small molecules during pyrolysis, resulting in varying etching effects on the pitch-based intermediate coke. For example, urea-formaldehyde resin releases nitrogen-containing compounds from organic matter, which is beneficial for micropore formation and contributes to rate performance and slope capacity. Cellulose biomass, on the other hand, releases large amounts of carbon dioxide, which helps in macropore formation and improves plateau capacity. Furthermore, different organic materials undergo pyrolysis at different temperatures, releasing small molecules. The impact of these small molecules on pore structure formation varies at different temperatures, thus allowing for more precise control of the pore structure.

[0015] Furthermore, the method for achieving uniform mixing in steps (S1) and (S2) includes, but is not limited to, ball milling, mechanical pulverization, and high-speed mixer, with ball milling being preferred. The process parameters for ball milling are well known in the art. In one specific embodiment of the present invention, uniform mixing is achieved through ball milling, with the following process parameters: adding 50-100 wt% water to the material, a ball-to-material ratio of 10-20:1, a rotation speed of 500-1000 rpm, and a milling time of 10-15 hours.

[0016] Further, in step (S2), the oxidizing atmosphere is at least one of air, oxygen, and ozone; the heat treatment is to first slowly heat to 150-200℃ and hold for 1-2 hours, and then rapidly heat to 300-350℃ and hold for 2-5 hours.

[0017] The slow heating rate is 1-3℃ / min, and the rapid heating rate is 5-10℃ / min. The initial slow heating and short holding time facilitates the complete melting of the asphaltene, allowing it to coat the surface of the organic matter in a bounding form, thus achieving a uniform core-shell structure. The second rapid holding time is to fully oxidize the asphaltene, depleting its H atoms and inhibiting subsequent molten rearrangement, which is beneficial for forming a uniform cross-linked structure. The step-like two-stage heating process helps the asphaltene to fully melt and encapsulate the atom-rich organic matter and bring it into contact with oxygen, thereby forming a uniform coated assembly and a uniform and disordered cross-linked structure. This will help to cross-link and pyrolyze the asphaltene molecules into short-range cross-linked graphite domains during the subsequent calcination process, and to bend them to form a closed-cell structure that facilitates sodium ion storage. Conversely, if the heating rate is too fast, the cross-linking copolymerization and asphaltene flow will be insufficient. This will cause the asphaltene in some areas to directly condense into mesophase carbon microspheres with ordered polymer sheets, or lead to a high degree of separation between the oxygen-containing organic pore-forming agent and the asphaltene. Subsequent high-temperature calcination will generate long-range ordered and tightly stacked graphene layers. At the same time, the small molecules formed by the decomposition of the pore-forming agent cannot contact the asphalt-based carbon. The resulting structure is not conducive to the storage of sodium ions. On the contrary, if the biomass rate is too slow, it may lead to the oxidation of biomass before the asphalt softens, resulting in too little residual biomass mass to play its value in subsequent processes.

[0018] Further, in step (S3), the inert atmosphere is argon, and the hydrocarbon is at least one selected from methane, ethane, propane, butane, ethylene, acetylene, and toluene. Preferably, calcination is performed in a hydrocarbon atmosphere, which is beneficial for improving the electrochemical performance of the negative electrode material; the calcination is carried out by heating to 1000-1600℃ at a heating rate of 5-10℃ / min for 5-10 hours.

[0019] Furthermore, in step (S3), after grinding and before washing, there is an acid washing step. Acid washing involves placing the material in acid and stirring for 10-24 hours to remove any possible excess impurities. The washing is performed by rinsing with water, and the drying is done in an oven or under vacuum. The acid is selected from at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid.

[0020] The sodium-ion battery anode material prepared by this invention has an irregular blocky morphology and features structural characteristics of curved graphite microcrystals of different sizes and closed pores. This invention uses asphalt-based precursor raw materials, which are inexpensive and readily available. After dispersion and mixing with oxygen-rich organic molecules, heat treatment is performed to cause isotropic crosslinking of the asphalt polymer, preventing the formation of mesophase carbon microspheres from asphaltene. Taking advantage of the difference in pyrolysis behavior between oxygen-rich organic materials and asphaltene, further pyrolysis causes the pore-forming agent to decompose and generate small molecules that etch the asphalt-based carbon material, forming a porous structure in situ. After cooling to room temperature, acid washing is performed to remove the metal impurities, resulting in a hard carbon material for sodium-ion battery anodes with high and low voltage capacities.

[0021] The sodium-ion battery anode material obtained by this invention exhibits an irregular morphology with a particle size of 1-20 μm and d 002 The value is between 0.36 and 0.40 nm.

[0022] Secondly, embodiments of the present invention provide a negative electrode sheet for a sodium-ion battery, comprising: a current collector, a binder coated on the current collector, and a sodium-ion battery negative electrode material prepared by the above-described preparation method.

[0023] Thirdly, the present invention provides a sodium-ion secondary battery, comprising a negative electrode sheet made of sodium-ion battery negative electrode material obtained by the above preparation method.

[0024] This invention provides a sodium-ion battery anode material based on carbon materials and pitch, its preparation method, and its application. Using abundant and inexpensive pitch / coal as raw materials, and common, low-cost sulfur-containing compounds and alkali metals / alkaline earth metals as activators, it achieves both high capacity and high energy density. It proposes an amorphous carbon material that is low-cost, simple to prepare, has adjustable disorder, high carbon yield, and is suitable for large-scale production, and applies it as an anode material in sodium-ion secondary batteries. Sodium-ion secondary batteries using this invention's anode material exhibit high operating voltage and energy density, excellent rate performance, stable cycle performance, and good safety performance. They can be used not only as power sources for mobile devices and electric vehicles, but also as energy storage devices for renewable energy generation, smart grid peak shaving, distributed power stations, backup power supplies, or communication base stations. Attached Figure Description

[0025] Figure 1 The thermal differential scanning spectroscopy-mass spectrometry-chromatograms are obtained during the pyrolysis process of Example 1 and Comparative Example 1 of this invention.

[0026] Figure 2 It is the pyrolysis gas component obtained by thermal differential scanning spectroscopy-mass spectrometry in step S3 of Example 1;

[0027] Figure 3 This is a SEM image of the amorphous carbon anode material obtained in Example 1;

[0028] Figure 4 High-resolution transmission electron microscope (HRTEM) images of the hard carbon materials obtained in Comparative Example 1 and Example 1;

[0029] Figure 5 XRD pattern of the composite carbon material provided in Example 1;

[0030] Figure 6 The SAXS spectra provided in Embodiment 1 and Comparative Example 1 of the present invention;

[0031] Figure 7 The constant current charge-discharge curves of a sodium-ion battery provided in Embodiment 1, Comparative Examples 1 and 2 of the present invention are shown. Detailed Implementation

[0032] The amorphous carbon anode material for a fossil mineral-based sodium-ion battery described in this invention will be further described below with reference to specific embodiments and accompanying drawings. However, it should be understood that the scope of protection of this invention is not limited to the following embodiments.

[0033] 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.

[0034] Example 1

[0035] (S1) Weigh 1 part by mass of coal tar pitch powder (sieved through 200 mesh), 1 part by mass of biomass (camellia shell), and 2 parts by mass of water (equal to the mass of the above materials). Mix them and place them in a ball mill jar. Control the ball-to-material ratio to be 20:1. Set the ball mill speed to 500 rpm and the forward and reverse rotation modes. Ball mill for 10 hours. Place the mixture in an oven to dry and grind it into a fine powder. Vacuum dry to obtain mixed precursor I.

[0036] (S2) Place the mixed precursor I in a muffle furnace and calcine it at a heating rate of 2℃ / min. After heating to 200℃, hold it for 1 hour. Then heat it at a heating rate of 10℃ / min until it cools to 350℃ and holds it at room temperature for 4 hours. After cooling to room temperature, the mixed precursor II is obtained.

[0037] Figure 1 These are the infrared spectra of the crosslinked modified asphalt obtained in Example 1 and Comparative Example 1. It can be seen that the intermediate modified by oxidative crosslinking with oxygen-rich organic additives is very different in terms of functional groups compared with the intermediate of asphalt that directly self-polymerizes (Comparative Example 1) and forms an ordered layered stacked mesophase. A large number of oxygen-containing functional groups also appear in the spectra, indicating that functional group changes occur during asphalt copolymerization, and its directional rearrangement structure is also altered.

[0038] (S3) Grind the mixed precursor II, sieve it through a 200-mesh sieve, place it in a high-temperature tube furnace, and introduce a mixed hydrocarbon gas atmosphere of toluene and acetylene in a volume ratio of 1:1. Heat the mixture to 1500℃ at a rate of 10℃ / min, hold it at that temperature for 5 hours, cool it to room temperature, grind it, put it into a hydrochloric acid solution and stir for 24 hours, wash it with deionized water, and dry it to obtain the amorphous carbon anode material.

[0039] Figure 2 The diagram shows the gas release during the S3 process in Example 1. It can be seen that the direct pyrolysis of asphalt mainly releases large hydrocarbon molecules, while the gas release is greatly reduced after oxidative cross-linking. At the same time, the embedded biomass releases a large number of small molecules during pyrolysis, which changes the pore structure of the carbon material.

[0040] Figure 3 The image shows the SEM image of the amorphous carbon anode material obtained in Example 1. It can be seen that the carbon anode material obtained by calcination has an irregular morphology and a particle size of 1-20 μm.

[0041] Figure 4 High-resolution transmission electron microscopy (HRTEM) images of the hard carbon materials obtained in Comparative Example 1 and Example 1 show that the modified material possesses bent and closed local graphite domains, and it also forms a large number of closed-pore structures. This is closely related to the improvement in the capacity of the low-pressure plateau region. The formation of closed pores provides favorable conditions for the precipitation of sodium metal clusters inside the hard carbon, without affecting the diffusion of sodium ions in the anode material. High-temperature calcination reduces the formation of oxygen-containing functional groups and defects on the surface by the activator, eliminating its influence on the coulombic efficiency of the material. This structure is completely different from the carbon material obtained by direct calcination of pitch. Furthermore, the hard carbon sample of Example 3, obtained by a pore-forming agent composed of various oxygen-containing organic compounds, has richer pores, which will lead to a higher plateau capacity.

[0042] Figure 5 The XRD patterns of the carbon materials obtained in Example 1 (PBOC), Comparative Example 1 (POC), and Comparative Example 2 (PC) of this invention show that the amorphous carbon anode obtained by cross-linking activation of sodium ions has increased amorphousness compared to the carbon material obtained by direct calcination. The modified carbon material has a larger interlayer spacing and lower crystallinity, indicating that the average packing degree of graphite domains has decreased. The short-range ordered graphite domains are more conducive to forming a closed microporous structure when they cross-link with each other, thereby effectively storing sodium ion clusters in the low-pressure plateau region.

[0043] (S4) The obtained amorphous carbon negative electrode material, conductive additive SP, and binder CMC / SBR are mixed in a weight ratio of 94:2:4, dissolved in water, and stirred to obtain a uniform slurry. The slurry is then uniformly coated on carbon-coated aluminum foil using a 50μm scraper, dried, and sliced ​​to obtain the negative electrode sheet.

[0044] Example 2

[0045] The other operating steps are the same as in Example 1, except that in step (S1), the coal tar pitch powder is replaced with sulfurized pitch blocks.

[0046] Example 3

[0047] The other operating steps are the same as in Example 1, except that in step (S1), the camellia husk biomass is replaced with phenolic resin PF131.

[0048] Example 4

[0049] The other operating steps are the same as in Example 1, except that in step (S1), the camellia shell biomass is replaced with a mixture of phenolic resin PF131 and potassium citrate in a mass ratio of 3:1.

[0050] Example 5

[0051] The other operating steps are the same as in Example 1, except that in step (S1), the camellia shell biomass is replaced with sodium citrate.

[0052] Example 6

[0053] The other operating steps are the same as in Example 1, except that in step (S1), the biomass of camellia shell is replaced by a mixture of camellia shell, phenolic resin PF131 and potassium citrate in a mass ratio of 1:0.5:0.2.

[0054] Example 7

[0055] The other operating steps are the same as in Example 1, except that in step (S1), the camellia oleifera shell biomass is replaced by a mixture of camellia oleifera shell, bisphenol A epoxy resin E41 and potassium citrate in a mass ratio of 1:0.3:0.1.

[0056] Example 8

[0057] The other operating steps are the same as in Example 6, except that step (S2) is as follows: the mixed precursor I is placed in a muffle furnace and calcined at a heating rate of 2°C / min. After heating to 250°C, it is held at that temperature for 1 hour. Then, the temperature is increased at a rate of 5°C / min until it is cooled to 300°C. It is held at that temperature for 5 hours until it reaches room temperature. After cooling to room temperature, the mixed precursor II is obtained.

[0058] Example 9

[0059] The other operating steps are the same as in Example 6, except that step (S2) is as follows: the mixed precursor I is placed in a muffle furnace and calcined at a heating rate of 5°C / min. After heating to 350°C, it is held at that temperature for 5 hours and then cooled to room temperature to obtain the mixed precursor II.

[0060] Example 10

[0061] The other operating steps are the same as in Example 6, except that step (S2) is as follows: the mixed precursor I is placed in a muffle furnace and calcined at a heating rate of 10°C / min. After heating to 200°C, it is held at that temperature for 1 hour. Then, the temperature is increased at a rate of 2°C / min until it is cooled to 350°C. It is held at that temperature for 4 hours until it reaches room temperature. After cooling to room temperature, the mixed precursor II is obtained.

[0062] Example 11

[0063] The other operating steps are the same as in Example 1, except that in step (S2), the heating rate of oxidation is changed to 0.5 / min.

[0064] Example 12

[0065] The other operating steps are the same as in Example 1, except that the steps of stirring in hydrochloric acid solution for 24 hours and washing with deionized water in step (S3) are omitted.

[0066] Example 13

[0067] The other operating steps are the same as in Example 1, except that the steps of stirring in hydrochloric acid solution for 24 hours and washing with deionized water in step (S3) are omitted.

[0068] Example 14

[0069] The other operating steps are the same as in Example 1, except that in step (S3), the calcination temperature is changed from 1500℃ to 1300℃.

[0070] Example 15

[0071] The other operating steps are the same as in Example 1, except that in step (S3), the calcination temperature is changed from 1500℃ to 1000℃.

[0072] Comparative Example 1

[0073] The coal tar pitch is directly calcined at 1500℃.

[0074] Comparative Example 2

[0075] The other conditions are the same as in Example 1, except that no oxygen-rich organic molecules are added in step (S1).

[0076] Figure 6 The SAXS spectra provided in Embodiment 1 and Comparative Example 1 and Comparative Example 2 of the present invention; from Figure 5 The SAXS spectra of the carbon materials before and after modification were analyzed and fitted using the following model:

[0077]

[0078] Where q is the scattering vector, A and B are proportional to the total volume of the large and small pores, and D is the constant background scattering.

[0079] Since parameter B is proportional to the total micropore volume in the carbon material, a quantitative comparison of the porosity can be obtained by comparing the B values ​​of Example 1 and Comparative Example 1. Furthermore, the Guinier plateau near q = 0.1 indicates that the carbon material obtained in Example 1 possesses a large number of microporous structures, while Comparative Example 1 does not exhibit a Guinier plateau in the range of q = 0.01-1, meaning it lacks microporous structures of 1-10 nm. It can be seen that, compared to directly calcined pitch materials, the functional group-modified, in-situ small molecule pyrolysis-based hard carbon material exhibits higher porosity and internal surface area. The newly formed pores facilitate the adsorption and deposition of sodium ions and sodium clusters on its inner surface.

[0080] Application examples Electrochemical performance testing

[0081] The dried negative electrode sheet was assembled into a coin cell with a sodium metal negative electrode, a carboxylic acid cellulose membrane, and EC / DEC / 1M NaPF6 electrolyte. The cell was then placed on a LAND test platform for testing, yielding the first cycle curve shown in Table 1. Within the voltage range of 0.001–2V, the cell was first activated for 5 cycles at a current density of 20 mA / g, followed by charge-discharge cycling.

[0082] Figure 7 The first-cycle charge-discharge curves of Example 1 are presented. Compared with the direct calcination of Comparative Example 1, the modified carbon material exhibits a significantly improved capacity and a distinct plateau-slope composite curve, indicating a change in the main sodium storage mechanism.

[0083] The electrochemical performance of the negative electrode materials obtained in the above embodiments and comparative examples is listed in Table 1 below:

[0084] Table 1 Electrochemical performance data

[0085]

[0086]

[0087] The test results of the half-cells in Table 1 for each embodiment show that after cross-linking and activating fossil mineral precursors such as pitch, the low-pressure plateau capacity of the amorphous carbon anode in the sodium-ion battery is significantly improved, and the specific capacity is also further improved. For example, in Example 6, the carbon anode material has a capacity of 380 mAh g / g. -1 Total capacity up to 258mAh g -1The modified example exhibits a low-pressure plateau capacity, while the unmodified comparative example 1 has a specific capacity of only 65 mAh / g, with almost no low-pressure plateau. It is worth noting that the crosslinking activation conditions need to be properly controlled; by controlling the activation conditions, the optimal carbon layer structure and the maximum specific capacity can be obtained.

[0088] This invention provides an application of fossil mineral-based pyrolytic amorphous carbon material in sodium-ion batteries. Its contribution to the prior art lies in leveraging the characteristic of releasing a large number of small molecules during pyrolysis due to its high proportion of heteroatoms. This, combined with fossil mineral pyrolysis, increases the porosity of the generated carbon material while inhibiting long-range ordered rearrangement of the carbon layer. This leads to localized cross-linking and closure of graphite domains, forming closed pores, enhancing sodium-ion storage in the low-pressure region, and significantly improving the electrochemical performance of the sodium-ion battery. It is understood that while the various embodiments of this invention have described the invention in detail with specific electrolytes, separators, current collectors, active materials, binders, conductive additives, etc., these descriptions are merely for fulfilling legal requirements and illustrating the composition of sodium-ion batteries. This invention is not limited to the given embodiments. Any modifications, equivalent substitutions, and improvements made using this specification within the spirit and principles of this invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this invention.

Claims

1. A method for preparing a sodium-ion battery anode material, characterized in that, Includes the following steps: (S1) Mix asphalt-based substances with heteroatom-rich organic matter evenly to obtain mixed precursor I; (S2) The mixed precursor is pressed into sheets, heat-treated in an oxidizing atmosphere, cooled and cooled, and the mixed precursor II is obtained by encapsulating the atom-rich organic matter during the asphalt melting process. (S3) Mixed precursor II is calcined, cooled, ground, washed and dried under an inert atmosphere or a hydrocarbon atmosphere to obtain an amorphous sodium-ion battery anode material.

2. The preparation method according to claim 1, characterized in that, In step (S1), the asphalt-like substance includes one or more mixtures of coal tar pitch, petroleum pitch, natural pitch, and mesophase pitch; the heteroatom-rich organic matter is selected from at least one of biomass (camellia shell, straw, coconut shell, crustacean exoskeleton such as shrimp shell, pine cone powder), polymers (epoxy resin, phenolic resin), and small organic molecules (urea, citric acid, and potassium / sodium / magnesium citrate); the mass ratio of the asphalt-like precursor to the heteroatom-rich organic matter is 1:0.5-1.

3. The preparation method according to claim 1, characterized in that, In step (S1), the asphalt-like substance is a mixture with asphaltene as the main component, and the viscosity-average molecular weight range of the asphaltene is preferably 2000-5000 g / mol.

4. The preparation method according to claim 1, characterized in that, In step (S1), the heteroatom-rich organic matter is a combination of biomass, polymers, and small organic molecules.

5. The preparation method according to claim 3, characterized in that, The mass ratio of biomass, polymers, and small organic molecules is 1:0.3-0.5:0.1-0.

2.

6. The preparation method according to claim 1, characterized in that, The methods for uniform mixing in steps (S1) and (S2) include ball milling, mechanical crushing, and high-speed mixer; ball milling is preferred, with the following process parameters: 50-100 wt% water added to the material, ball-to-material ratio of 10-20:1, rotation speed of 500-1000 rpm, and ball milling time of 10-15 h.

7. The preparation method according to claim 1, characterized in that, In step (S2), the oxidizing atmosphere is at least one of air, oxygen, and ozone; the heat treatment is to first slowly heat to 150-200℃ and hold for 1-2 hours, and then rapidly heat to 300-350℃ and hold for 2-5 hours; preferably, the heating rate of the slow heating is 1-3℃ / min, and the heating rate of the rapid heating is 5-10℃ / min.

8. The preparation method according to claim 1, characterized in that, In step (S3), the inert atmosphere is argon, and the hydrocarbon is at least one of methane, ethane, propane, butane, ethylene, acetylene, and toluene; preferably, calcination is carried out in a hydrocarbon atmosphere; the calcination is carried out by heating to 1000-1600°C at a heating rate of 5-10°C / min and calcining for 5-10 hours.

9. The preparation method according to claim 1, characterized in that, In step (S3), after grinding and before washing, there is an acid washing step, in which the material is placed in acid and stirred for 10-24 hours.

10. A sodium-ion battery anode material, characterized in that, The sodium-ion battery negative electrode material is prepared by the method described in any one of claims 1-9, wherein the particle size of the sodium-ion battery negative electrode material is 1-20 μm, and d 002 The value is between 0.36 and 0.40 nm.

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