A heteroatom-doped porous hard carbon negative electrode material, a preparation method therefor, and an application thereof

Abstract

The application relates to the field of alkali metal ion battery negative electrode materials, in particular to a heteroatom-doped porous hard carbon negative electrode material and a preparation method and application thereof. The preparation method comprises the following steps: low-temperature heat treatment of original pitch in an oxygen-containing atmosphere to obtain pre-oxidized pitch; dispersing the pre-oxidized pitch, a functional additive and a hard carbon precursor in a solvent, removing the solvent to obtain a precursor composite; wherein the functional additive is a functional additive integrating crosslinking, pore forming and heteroatom source; high-temperature heat treatment of the precursor composite in a protective atmosphere to obtain the heteroatom-doped porous hard carbon negative electrode material. The heteroatom-doped porous hard carbon negative electrode material prepared by the application can significantly improve the sodium storage specific capacity and the first cycle coulombic efficiency of the material, and simultaneously has excellent cycle stability and rate performance.

Description

Technical Field

[0001] This invention relates to the field of anode materials for alkali metal ion batteries, specifically to a heteroatom-doped porous hard carbon anode material, its preparation method, and its application. Background Technology

[0002] With the rapid development of portable electronic devices and new energy electric vehicles, and the increasing demand for energy storage across various sectors of society, lithium-ion battery production has reached an unprecedented scale. However, lithium resources are scarce and unevenly distributed in the Earth's crust, resulting in my country's current reliance on imports for 80% of its lithium resources. Therefore, the research and commercialization of low-cost, environmentally friendly, and moderately energy-density sodium-ion batteries (SIBs) has attracted significant national attention. The anode material, as the primary sodium storage component of SIBs, directly determines the overall electrochemical performance of the SIB by enabling the insertion and extraction of sodium ions during charging and discharging. Currently, amorphous hard carbon and soft carbon are considered the most promising commercially viable SIB anode materials.

[0003] Hard carbon possesses advantages such as a low sodium intercalation plateau and high capacity, but its lower first-cycle coulombic efficiency, poor cycling stability, and high preparation cost limit its further development. The microstructure of hard carbon directly affects its sodium storage capacity, which in turn largely depends on the choice of precursor materials. Larger interlayer spacing and porous structures provide more channels for sodium ion transport, while also offering more active sites and sodium storage space for ion insertion and extraction. Constructing stable heterostructures coupled with heteroatom doping (such as N, S, P, O, and B) allows for precise control of surface defects, pore structure, interlayer spacing, and ion transport impedance at the heterostructure interface, potentially yielding sodium-ion anode materials that combine performance advantages with economic benefits.

[0004] Currently, the main precursors for hard carbon are biomass-based, resin-based, and bitumen-based. Biomass-based hard carbon suffers from poor product consistency, low carbon yield, and susceptibility to seasonality. Resin-based hard carbon materials exhibit good sodium storage performance, but their raw material costs are high. Bitumen, as a byproduct of the petroleum industry, is an ideal precursor for carbon material preparation due to its low cost and high carbon yield. However, the preparation process of most asphalt-based hard carbon materials is complex. For example, the preparation process of spherical asphalt-based derived hard carbon materials disclosed in patent CN109037603A involves cross-linking oxidation preparation, spray granulation, carbonization, coating and graphitization. The preparation process of porous hard carbon disclosed in patent CN114477130A involves briquetting and acid washing. In addition, asphalt is prone to graphitization during high-temperature carbonization to form highly ordered soft carbon materials. The preparation process of an asphalt-based porous carbon anode material disclosed in patent CN115676804A not only involves spray drying and multiple acid treatments, but its sodium storage behavior is a typical soft carbon structure. After 100 charge-discharge cycles, the capacity retention rate is only about 67%, indicating that the cycle stability of this material is poor.

[0005] Crosslinking and pre-oxidation pretreatment are effective methods to suppress graphitization of asphalt during high-temperature carbonization. Patents CN113735095A and CN113800496A used oxidized asphalt as a carbon source and calcium carbonate and magnesium chloride as pore-forming and crosslinking agents, respectively, to obtain honeycomb-like porous hard carbon materials. However, the first-cycle coulombic efficiencies of these materials were only 75% and 78%, respectively, indicating significant room for improvement and severely impacting the overall energy density of the battery. Patents CN116835566A and CN117228670A used inorganic salts as pore-forming oxidants and template agents to obtain porous hard carbon anode materials, demonstrating good sodium storage performance. However, reports on organic pore-forming and crosslinking agents are very limited. Recently, patent CN117276497A simultaneously used imidazole-based organic crosslinking agents and organic sodium salts to effectively improve the overall sodium storage performance of hard carbon. However, this method involves cross-linking curing, soaking, filtration and secondary carbonization, and the ratio of pitch to resin-based hard carbon precursor in the precursor material is 5:100, which results in high preparation costs and is not conducive to industrial production. Summary of the Invention

[0006] In view of the existing problems, the purpose of this invention is to provide a heteroatom-doped porous hard carbon anode material with both performance and cost advantages, as well as its preparation method and applications. This invention utilizes a specially designed functional additive to regulate the interfacial chemical interaction between pre-oxidized asphalt and the hard carbon precursor, obtaining the porous hard carbon anode material through a one-step heat treatment. The preparation method described in this invention is simple, easily extendable to other systems, and can meet the requirements of practical applications. Moreover, the heteroatom-doped porous hard carbon anode material prepared by this invention can significantly improve the sodium storage specific capacity and first-cycle coulombic efficiency, while also exhibiting excellent cycle stability and rate performance.

[0007] In a first aspect, the present invention provides a method for preparing a heteroatom-doped porous hard carbon anode material, comprising the following steps: Pre-oxidized asphalt is obtained by low-temperature heat treatment of raw asphalt in an oxygen-containing atmosphere; Pre-oxidized asphalt, functional additives, and hard carbon precursors are dispersed in a solvent, and the solvent is removed to obtain a precursor complex; wherein, the functional additives are functional additives that integrate crosslinking, pore formation, and heteroatom origination. Porous hard carbon anode material was obtained by high-temperature heat treatment of the precursor composite in a protective atmosphere.

[0008] Preferably, the original asphalt is any one or a combination of two or more of natural asphalt, coal-based asphalt, petroleum-based asphalt, and mesophase asphalt; the oxygen-containing atmosphere is oxygen or air; or, the oxygen-containing atmosphere is a mixture of oxygen and any one of air and an inert gas; preferably, the inert gas is any one or a combination of two or more of nitrogen, helium, neon, argon, krypton, and radon.

[0009] Preferably, the low-temperature heat treatment is performed at a temperature of 100–500°C for a time of 0.5–10 hours.

[0010] Preferably, the mass ratio of the pre-oxidized asphalt, functional additives and hard carbon precursor is 100:1:1 to 1:100:100, and more preferably 1:(0.1 to 10):(0.1 to 10).

[0011] Preferably, the functional additive is any one or a combination of two or more of urea, thiourea, cyanamide, dicyandiamide, melamine, and cyanuric acid.

[0012] Preferably, the solvent is any one or a combination of two or more of water, ethanol, diethyl ether, toluene, acetonitrile, dichloromethane, chloroform, N,N-dimethylformamide, dimethyl sulfoxide, carbon tetrachloride, xylene, quinoline, and pyridine.

[0013] Preferably, the protective atmosphere is an inert gas, preferably any one or a combination of two or more of nitrogen, helium, neon, argon, krypton, and radon.

[0014] Preferably, the high-temperature heat treatment is performed at a temperature of 1000–1600°C for a duration of 1–6 hours.

[0015] Secondly, the present invention provides a heteroatom-doped porous hard carbon anode material obtained according to any one of the above-described preparation methods. The heteroatom-doped porous hard carbon anode material has a hierarchical porous structure containing macropores, mesopores, and micropores; preferably, the macropores have a diameter of 50–5000 nm, the mesopores have a diameter of 2–50 nm, and the micropores have a diameter of 0.5–1.8 nm.

[0016] Thirdly, the present invention provides the application of heteroatom-doped porous hard carbon anode materials obtained according to any one of the above preparation methods in anode materials for alkali metal ion batteries. The alkali metal ion batteries include, but are not limited to, sodium-ion batteries, potassium-ion batteries, etc.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention prepares heteroatom-doped porous hard carbon anode materials through a simple and effective process, which is beneficial for industrial production.

[0019] 2. This invention controls the interfacial chemical interaction between pre-oxidized asphalt and hard carbon precursor through specially designed functional additives, providing abundant sodium storage active sites and hierarchical porous structure, while maintaining a high first-cycle coulombic efficiency, and exhibiting excellent sodium storage performance.

[0020] 3. The heteroatom-doped porous hard carbon anode material of the present invention exhibits good cycle stability and rate performance, which broadens the application field of asphalt in alkali metal ion batteries.

[0021] In summary, the heteroatom-doped porous hard carbon anode material prepared by the method described in this invention has excellent sodium storage performance and economic advantages, and has great potential for practical application. Attached Figure Description

[0022] Figure 1 This is a SEM image of the heteroatom-doped porous hard carbon anode material prepared according to the present invention; Figure 2 This is a first-cycle charge-discharge curve of the heteroatom-doped porous hard carbon anode material prepared in Example 1 of this invention; Figure 3 This is a long-cycle performance curve of the heteroatom-doped porous hard carbon anode material prepared in Example 1 of this invention; Figure 4This is a rate performance curve of the heteroatom-doped porous hard carbon anode material prepared in Example 1 of this invention. Detailed Implementation

[0023] The present invention is further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0024] This invention discloses a precursor composite consisting of pre-oxidized asphalt, special functional additives, and a hard carbon precursor, which is heat-treated to obtain a heteroatom-doped porous hard carbon anode material. The preparation method of the porous hard carbon anode material of this invention is simple and facilitates industrial production. It not only improves the first-cycle coulombic efficiency and sodium storage capacity of the material, but also exhibits excellent cycle stability and rate performance. The following exemplarily illustrates the preparation method of the heteroatom-doped porous hard carbon anode material of this invention.

[0025] Pre-oxidized asphalt is obtained by low-temperature heat treatment of raw asphalt in an oxygen-containing atmosphere. The raw asphalt can be any one or a combination of two or more of natural asphalt, coal-based asphalt, petroleum-based asphalt, and mesophase asphalt. The oxygen-containing atmosphere is oxygen or air. Alternatively, the oxygen-containing atmosphere is a mixture of any one of oxygen or air and an inert gas. The volume percentage of oxygen or air in the mixed gas can be in the range of 5-100%. Preferably, the inert gas is any one or a combination of two or more of nitrogen, helium, neon, argon, krypton, and radon. The low-temperature heat treatment temperature can be 100–500°C, and the time can be 0.5–10 hours. Low-temperature heat treatment enables pre-oxidation of the asphalt surface.

[0026] Pre-oxidized asphalt can be prepared by the following method: Weigh the raw asphalt into a crucible, and heat it from room temperature to 100–500°C at a rate of 0.5–20°C / min in an oxygen-containing atmosphere, and hold it at this temperature for 0.5–10 hours to obtain pre-oxidized asphalt. After the pre-oxidized asphalt has cooled naturally, it can be ground in an agate mortar and pestle, and the ground powder can be collected.

[0027] Pre-oxidized asphalt, special functional additives, and hard carbon precursor are dispersed in a solvent in a certain proportion. After removing the solvent, a precursor complex is obtained. The solvent can be removed by heating, for example, until the solvent is completely evaporated.

[0028] The mass ratio of the pre-oxidized asphalt, special functional additives, and hard carbon precursor can be in the range of 100:1:1 to 1:100:100. Preferably, the mass ratio of the pre-oxidized asphalt, special functional additives, and hard carbon precursor is 1:(0.1-10):(0.1-10). Controlling the mass ratio of the pre-oxidized asphalt, special functional additives, and hard carbon precursor within the above range can effectively regulate the pore structure and cycling stability of the hard carbon. If the mass ratio of the pre-oxidized asphalt, special functional additives, and hard carbon precursor exceeds the above range, it will lead to a decrease in sodium storage capacity, deterioration of cycling performance, and poor rate performance. More preferably, the mass ratio of the pre-oxidized asphalt, special functional additives, and hard carbon precursor is 1:(0.1-5):(0.1-5).

[0029] The special functional additive is characterized by its precisely designed and regulated cross-linked network structure, and the presence of multiple functional groups, such as amino, hydroxyl, and carboxyl groups. It can function as a cross-linking agent, a pore-forming agent, and also achieve heteroatom doping. Therefore, the functional additive integrates cross-linking, pore-forming, and heteroatom origination. For example, the functional additive may be any one or a combination of two or more of urea, thiourea, cyanamide, dicyanamide, melamine (trimer), and cyanuric acid.

[0030] For example, the functional additive is urea. Urea is rich in amino groups, which can achieve full cross-linking of the heterogeneous interface between pitch and hard carbon precursor. At high temperatures, it can generate volatile gases such as ammonia, which is beneficial for the formation of porous structures. In addition, urea can also serve as a nitrogen source to achieve in-situ co-doping of nitrogen, thereby adjusting the interlayer spacing and electronic structure of carbon materials.

[0031] Salt oxides, such as permanganates, ferrates, persulfates, percarbonates, or carbonates, can function as pore-forming and oxidizing agents, but they lack cross-linking properties. The functional additives selected in this application not only achieve pore-forming but also undergo thermal polymerization during heat treatment to form a cross-linked network rich in functional groups. This allows for the construction of a stable heterogeneous interface within the precursor complex through chemical cross-linking. Conversely, inorganic salt oxides, lacking abundant functional groups, cannot achieve these functions.

[0032] Similarly, imidazole or thiazole crosslinking agents, such as 4-methylimidazolium, dimethylnitroimidazole, 2-n-butyl-4-chloro-5-carboxymethylimidazolium, 2-n-propyl-4-methyl-6-carboxybenzimidazole, 1,2'-bis(2-chlorophenyl)-tetraphenylbiimidazole, bimidazole, oximidazolium, etc., although they have crosslinking effects, due to their limited nitrogen content, only a few volatile gases escape during high-temperature processes, thus limiting their pore-forming function and hindering the improvement of rate performance.

[0033] Therefore, the introduction of the functional additive crosslinking agent of the present invention has multiple functions: (1) it can enhance the interaction between asphalt molecules, inhibit their graphitization process at high temperature, and increase the interlayer spacing of hard carbon microcrystals; (2) it can obtain a stable heterogeneous interface, thereby improving the cycle stability of hard carbon materials; (3) it can also act as a pore-forming agent and introduce heteroatoms, which is conducive to the generation of hierarchical pore structures and the introduction of abundant sodium storage active sites.

[0034] The hard carbon precursor is a carbon material containing oxygen-containing groups. For example, the hard carbon precursor includes, but is not limited to, any one or a combination of two or more of glucose, sucrose, fructose, polyacrylonitrile, phenolic resin, epoxy resin, polyethylene terephthalate, polyfurfuryl alcohol, lignin, and cellulose.

[0035] It should be noted that although the prior art mentions the use of melamine resin as a hard carbon precursor, the melamine resin does not play a role in crosslinking, pore formation, or the introduction of heteroatoms.

[0036] The solvent is any one or a combination of two or more of the following: water, ethanol, diethyl ether, toluene, acetonitrile, dichloromethane, chloroform, N,N-dimethylformamide, dimethyl sulfoxide, carbon tetrachloride, xylene, quinoline, and pyridine. Preferably, the solvent is a mixture of volatile solvents such as water, ethanol, diethyl ether, and acetonitrile with non-volatile solvents such as toluene, dichloromethane, chloroform, N,N-dimethylformamide, dimethyl sulfoxide, carbon tetrachloride, xylene, quinoline, and pyridine. More preferably, the volatile solvent accounts for 20-80% of the volume of the mixture. When the amount of organic solvents such as N,N-dimethylformamide, dimethyl sulfoxide, carbon tetrachloride, xylene, quinoline, and pyridine used is small, they can evaporate along with the volatile solvents such as water, ethanol, and diethyl ether.

[0037] The precursor composite was subjected to high-temperature heat treatment in a protective atmosphere to obtain a porous hard carbon anode material. The protective atmosphere was any one or a combination of two or more of nitrogen, helium, neon, argon, krypton, and radon. The high-temperature heat treatment was performed at 1000–1600°C for 1–6 hours.

[0038] The precursor composite can be heated from room temperature to a predetermined high-temperature heat treatment temperature in a protective atmosphere at a certain heating rate, held at that temperature for several hours, and then naturally cooled to obtain a porous hard carbon anode material. The heating rate can be in the range of 1–20 °C / min.

[0039] The heteroatom-doped porous hard carbon anode material of the present invention has a hierarchical porous structure, containing macropores, mesopores, and micropores. Preferably, the macropores have a diameter of 50–5000 nm, the mesopores have a diameter of 2–50 nm, and the micropores have a diameter of 0.5–1.8 nm.

[0040] This invention also provides applications of the aforementioned heteroatom-doped porous hard carbon anode material, particularly in alkali metal ion battery anode materials.

[0041] In summary, this invention controls the interfacial chemical interaction between pre-oxidized asphalt and hard carbon precursor through special functional additives. At high temperatures, this not only inhibits the graphitization process of the asphalt and increases the interlayer spacing of hard carbon microcrystals, but also achieves a stable heterogeneous interface, introducing heteroatoms and a hierarchical porous structure, providing abundant sodium storage active sites, and significantly improving the overall sodium storage performance of hard carbon materials, overcoming the difficulties existing in the prior art. Furthermore, this invention eliminates the need for pre-sodiumization treatment of the material, resulting in hard carbon materials with high first-cycle coulombic efficiency.

[0042] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0043] Example 1

[0044] This embodiment provides a heteroatom-doped porous hard carbon anode material, and the preparation method is as follows:

[0045] 20g of petroleum asphalt was weighed and placed in a crucible. It was heated from room temperature to 350℃ at a rate of 2℃ / min in an Ar / O2 environment (Ar volume fraction 10%), held at this temperature for 4 hours, cooled with the furnace, and ground to obtain pre-oxidized asphalt. 3g of pre-oxidized asphalt, 7g of urea, and 7g of phenolic resin were weighed and ultrasonically dispersed in 100mL of a mixed solvent of ethanol and water (v:v = 1:1) to obtain a uniform dispersion. The dispersion was heated to 80℃ and stirred until the solvent completely evaporated to obtain the precursor composite. Subsequently, the precursor composite was heated from room temperature to 1400℃ at a rate of 5℃ / min under an argon atmosphere, held at this temperature for 2 hours, cooled with the furnace, and ground to obtain a heteroatom-doped porous hard carbon anode material.

[0046] Figure 1 This is a SEM image of the heteroatom-doped porous hard carbon anode material obtained in Example 1 of this invention. The image shows that the material has a rich pore structure.

[0047] Figure 2This is a first-cycle charge-discharge curve of the heteroatom-doped porous hard carbon anode material obtained in Example 1 of this invention. 160 mg of heteroatom-doped porous hard carbon anode material, 20 mg of Super P, and 20 mg of CMC were weighed and dispersed in 2 mL of water to obtain a slurry. After homogenization, coating, drying, and cutting, a sodium-ion battery anode sheet was prepared. Then, using a sodium metal sheet as the anode, the resulting electrode sheet as the positive electrode, GF / C glass fiber as the separator, and a 1 mol / L NaPF4 diethylene glycol dimethyl ether solution as the electrolyte, a CR2025 coin-type sodium-ion battery was assembled in an argon glove box. After the assembled battery was left to stand for 8 hours, it was discharged at a constant current density of 0.25 g / A to 0.01 V, left to stand for 5 minutes, and then charged at the same constant current density to 2.5 V. This was followed by a 5-minute stand, completing one constant current charge-discharge cycle. Experimental results show that the sodium storage specific capacity of the obtained heteroatom-doped porous hard carbon anode material is 349 mA / g, and the first-cycle coulombic efficiency is 85.9%.

[0048] Figure 3 This is a long-cycle performance curve of the heteroatom-doped porous hard carbon anode material prepared in Example 1 of this invention. The electrochemical testing process involved constant current charge-discharge cycling at a current density of 0.1 g / A. After the assembled battery was left to rest for 8 hours, it was discharged at a constant current of 0.25 g / A to 0.01 V, left to rest for 5 minutes, and then charged at the same constant current to 2.5 V. This process was repeated three times to activate the battery. The activated sodium-ion battery was then subjected to constant current charge-discharge cycling at a current of 0.1 g / A, with a voltage range of 0.01–2.5 V. It can be seen that the material can stably cycle 50 times at a current density of 0.1 g / A, with a reversible specific capacity of 331 mA / g and a capacity retention rate of 99.3%, indicating that the material has good stability.

[0049] Figure 4This is a rate performance curve of the heteroatom-doped porous hard carbon anode material prepared in Example 1 of this invention. The heteroatom-doped porous hard carbon material was mixed with Super P and CMC in a mass ratio of 8:1:1. After homogenization, coating, drying, and cutting, a sodium-ion battery anode sheet was prepared. Using a sodium metal sheet as the anode and the resulting electrode sheet as the positive electrode, GF / C glass fiber as the separator, and a 1 mol / L NaPF4 diethylene glycol dimethyl ether solution as the electrolyte, a CR2025 coin-type sodium-ion battery was assembled in an argon glove box. After the assembled battery was left to stand for 8 hours, it was discharged at a constant current of 0.25 g / A to 0.01 V, left to stand for 5 minutes, and then charged at the same constant current to 2.5 V. This process was repeated 5 times. Subsequently, constant current charge-discharge cycles were performed five times each at current densities of 0.1 g / A, 0.2 g / A, 0.5 g / A, 1 g / A, 2 g / A, 5 g / A, 10 g / A, and 1 g / A. It can be seen that the obtained material exhibits excellent rate performance, maintaining a sodium storage capacity of 18 mA / g at a current density of 10 g / A. When the current was reduced to 1 A / g, the sodium storage capacity immediately rebounded to 233 mA / g, indicating that the material's sodium storage behavior possesses excellent kinetics and stability.

[0050] Comparative Example 1

[0051] The difference between the comparative example and Example 1 is that the precursor compound was replaced with virgin bitumen.

[0052] Comparative Example 2

[0053] The difference between the comparative example and Example 1 is that a phenolic resin was used instead of the precursor complex.

[0054] Comparative Example 3

[0055] The difference between the comparative example and Example 1 is that pre-oxidized bitumen was used instead of the precursor compound.

[0056] Comparative Example 4

[0057] The difference between the comparative example and Example 1 is that the precursor compound is a mixture of pre-oxidized asphalt and urea in a mass ratio of 3:7.

[0058] Comparative Example 5

[0059] The difference between the comparative example and Example 1 is that the precursor compound is a mixture of pre-oxidized asphalt and urea in a mass ratio of 5:5.

[0060] Comparative Example 6

[0061] The difference between the comparative example and Example 1 is that the precursor compound is a mixture of pre-oxidized asphalt and urea in a mass ratio of 7:3.

[0062] Comparative Example 7

[0063] The difference between the comparative example and Example 1 is that the precursor compound is a mixture of pre-oxidized asphalt and phenolic resin in a mass ratio of 3:7.

[0064] Example 2

[0065] 5g of pre-oxidized asphalt, 5g of urea, and 5g of phenolic resin were weighed and ultrasonically dispersed in 100mL of a mixed solvent of ethanol and water (v:v = 1:1) to obtain a uniform dispersion. The dispersion was heated to 80℃ and stirred until the solvent was completely evaporated to obtain the precursor complex.

[0066] Example 3

[0067] 7g of pre-oxidized asphalt, 3g of urea, and 3g of phenolic resin were weighed and ultrasonically dispersed in 100mL of a mixed solvent of ethanol and water (v:v = 1:1) to obtain a uniform dispersion. The dispersion was heated to 80℃ and stirred until the solvent was completely evaporated to obtain the precursor complex.

[0068] Electrochemical tests were performed on the materials prepared in Comparative Examples 1-7 and Examples 2-3. The electrochemical tests were conducted using a constant current charge-discharge cycle at a current density of 0.1 g / A. After the assembled batteries were left to stand for 8 hours, they were discharged at a constant current of 0.25 g / A to 0.01 V, left to stand for 5 minutes, and then charged at the same constant current to 2.5 V. This process was repeated three times to activate the batteries. The activated sodium-ion batteries were then subjected to a constant current charge-discharge cycle at 0.1 g / A, with a voltage range of 0.01–2.5 V. The results are shown in Table 1.

[0069] Table 1 Comparison of sodium storage performance of carbon materials.

[0070] As can be seen from Table 1, the carbon materials prepared in Comparative Examples 1-7 and Examples 2-3 show significant differences in sodium storage performance. This is because the proportion of each component in the precursor complex plays a decisive role in the first-cycle coulombic efficiency and sodium storage specific capacity. In particular, the introduction of functional additives can enhance the interfacial interaction between the components and precisely control the microstructure of the target material. The functional additives in this invention have multiple functions: (1) they can enhance the interaction between pitch molecules, inhibit their graphitization process at high temperatures, and increase the interlayer spacing of hard carbon microcrystals; (2) they can obtain stable heterogeneous interfaces, thereby improving the cycling stability of hard carbon materials; (3) they can also act as pore-forming agents and introduce heteroatoms, which is beneficial to the generation of hierarchical pore structures and the introduction of abundant sodium storage active sites.

[0071] This invention illustrates the detailed process equipment and process flow through the above embodiments. However, this invention is not limited to the detailed process equipment and process flow described above, meaning that this invention does not necessarily depend on the detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

Claims

1. A method for preparing a heteroatom-doped porous hard carbon anode material, characterized in that, Includes the following steps: The raw asphalt is subjected to low-temperature heat treatment in an oxygen-containing atmosphere to obtain pre-oxidized asphalt; the low-temperature heat treatment temperature is 350℃ and the time is 0.5~10h. Pre-oxidized asphalt, functional additives, and hard carbon precursors are dispersed in a solvent, and the solvent is removed to obtain a precursor complex. The functional additives are those integrating crosslinking, pore-forming, and heteroatom origination. The functional additives are any one or a combination of two or more of urea, thiourea, cyanamide, dicyanamide, melamine, and cyanuric acid. The hard carbon precursors are selected from any one or a combination of two or more of glucose, sucrose, fructose, polyacrylonitrile, phenolic resin, epoxy resin, polyethylene terephthalate, polyfurfuryl alcohol, lignin, and cellulose. The mass ratio of the pre-oxidized asphalt, functional additives, and hard carbon precursors is 1:(0.1~5):(0.1~5). The precursor composite was subjected to high-temperature heat treatment in an inert atmosphere to obtain heteroatom-doped porous hard carbon anode material; the high-temperature heat treatment temperature was 1000~1600℃ and the time was 1~6h.

2. The preparation method according to claim 1, characterized in that, The original asphalt is any one or a combination of two or more of natural asphalt, coal-based asphalt, petroleum-based asphalt, and mesophase asphalt; the oxygen-containing atmosphere is oxygen, air, or a mixture of oxygen and air with an inert gas.

3. The preparation method according to claim 2, characterized in that, The inert gas is any one or a combination of two or more of nitrogen, helium, neon, argon, krypton, and radon.

4. The preparation method according to claim 1, characterized in that, The solvent is any one or a combination of two or more of the following: water, ethanol, diethyl ether, toluene, acetonitrile, dichloromethane, chloroform, N,N-dimethylformamide, dimethyl sulfoxide, carbon tetrachloride, xylene, quinoline, and pyridine.

5. The preparation method according to claim 1, characterized in that, The inert atmosphere is any one or a combination of two or more of nitrogen, helium, neon, argon, krypton, and radon.

6. The application of the heteroatom-doped porous hard carbon anode material obtained by the preparation method according to any one of claims 1 to 5 in the anode material of alkali metal ion batteries.

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