Hard carbon material, preparation method and application thereof, and sodium ion battery

Abstract

The invention relates to the technical field of hard carbon materials and electrochemical energy storage, and particularly discloses a hard carbon material, a preparation method and application thereof and a sodium ion battery. The hard carbon material is prepared from a fossil-based carbonaceous raw material, a doping agent and a pore-forming agent, a hierarchical porous structure is constructed by taking a pore-forming agent as a template, and the wide interlayer spacing of the hard carbon material is maintained; and sulfur / nitrogen active species are released by combining an in-situ nitrogen / sulfur doping technology, so that the pore surface is modified with a large number of uniformly distributed nitrogen / sulfur active sites, a synergistic sodium storage mode of pore efficient conveying-surface site rapid adsorption / reaction is constructed, and the sodium storage performance of the hard carbon material is greatly improved. Meanwhile, halogen elements are not introduced in the scheme, corrosion hazards are avoided, performance advantages and production safety are considered, and the key technical defects that an existing battery negative electrode material is high in corrosion, and the sodium storage capacity is low due to the fact that a hard carbon material is high in crystallinity, small in interlayer spacing and incapable of accurately regulating and controlling a pore structure are overcome.

Description

Technical Field

[0001] This application relates to the fields of hard carbon materials and electrochemical energy storage technology, and particularly to a hard carbon material, its preparation method and application, and sodium-ion batteries. Background Technology

[0002] Lithium-ion batteries hold a core position in the battery field due to their high energy density and excellent cycle performance. However, the tightening supply and rising prices of lithium resources have become key factors restricting the expansion of the large-scale energy storage market. Sodium-ion batteries, with their abundant sodium resources, low cost, and similar working principle to lithium-ion batteries, have become a highly promising alternative. As a core component, the anode material directly affects the performance indicators of sodium batteries.

[0003] Graphite is a mature commercial anode material for lithium-ion batteries, but it cannot meet the application requirements of sodium-ion batteries due to the large radius of sodium ions, high interlayer resistance, and the thermodynamic instability of Na-C compounds. In contrast, hard carbon materials, with their unique disordered structure, large interlayer spacing, and theoretical sodium storage capacity of up to 300.33 mAh / g, have become the optimal potential choice for anode materials in sodium-ion batteries. However, the development of hard carbon materials still faces significant bottlenecks: although biomass-derived hard carbon has certain sodium storage performance, the precursor sources are unstable and the yield is less than 30%, making it difficult to adapt to industrial-scale production; fossil fuel derivatives, represented by coal tar pitch, although widely available, inexpensive, and rich in carbon content, aligning with my country's development direction of high-value utilization of coal resources, are prone to graphitization during heat treatment, resulting in high crystallinity and interlayer spacing reduced to below 0.37 nm. The actual sodium storage capacity is generally below 250 mAh / g, severely restricting the industrialization process of pitch-based anode materials.

[0004] To address the aforementioned technical bottlenecks, Chinese patent CN117550585B proposed an improved scheme for preparing hard carbon materials by mixing halogen-containing acid anhydrides with coal tar pitch and then treating the mixture at high temperatures. While this technology improves the specific capacity of the material to some extent, it has significant drawbacks: halogen atoms are extremely corrosive to production equipment, significantly increasing equipment maintenance costs and posing serious safety hazards; furthermore, this scheme fails to effectively control the pore structure of the material, making it difficult to achieve comprehensive optimization of sodium storage performance. Addressing the common problems of small interlayer spacing, high crystallinity, and lack of pore structure control leading to insufficient sodium storage capacity in existing pitch-based hard carbon materials, as well as the corrosive hazards caused by halogen additives, this invention aims to develop a high-performance, non-corrosive sodium-ion battery anode material. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a hard carbon material, its preparation method and application, and a sodium-ion battery, to solve the key technical defects of existing battery negative electrode materials, such as strong corrosivity and low sodium storage capacity caused by the high crystallinity, small interlayer spacing and inability to precisely control the pore structure of hard carbon materials.

[0006] To achieve the above technical objectives, this application provides an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material, comprising the following components in parts by weight: 100 parts of fossil-based carbonaceous raw material; 200-280 parts of dopant, wherein the dopant includes at least one of sulfur dopant and nitrogen dopant; and 3-15 parts of pore-forming agent.

[0007] Further, fossil-based carbonaceous raw materials include at least one of bitumen, coal tar, and petroleum coke.

[0008] Furthermore, the sulfur dopant includes at least one of elemental sulfur, thiourea, sodium thiosulfate, ammonium persulfate, thioacetamide, benzothiophene, and aminosulfonic acid.

[0009] Furthermore, the nitrogen dopant includes at least one of urea, melamine, pyridine, ethylenediamine, ammonium chloride, polyvinylpyrrolidone, polyacrylonitrile, polyaniline, polydopamine, and chitosan.

[0010] Furthermore, the pore-forming agent includes at least one of magnesium oxide, zinc oxide, and calcium oxide.

[0011] This application provides a method for preparing hard carbon material, including the following steps:

[0012] Step S1: Grind and mix the fossil-based carbonaceous raw material, sulfur dopant, nitrogen dopant and pore-forming agent evenly to obtain a premix.

[0013] Step S2: Under nitrogen atmosphere protection, the premix is ​​calcined to obtain carbides;

[0014] Step S3: Immerse the carbide in an acidic solution until no more bubbles are generated on the surface of the carbide to obtain hard carbon material.

[0015] Furthermore, during the calcination treatment, the calcination temperature is 1300℃~1500℃, the calcination time is 1h~3h, and the heating rate is 1℃ / min~15℃ / min.

[0016] Furthermore, before calcination, the premix is ​​subjected to sulfidation treatment. The sulfidation treatment steps are as follows: the premix is ​​placed at 300~400℃ and kept at that temperature for 0.5h~3h; wherein the heating rate is 1℃ / min~10℃ / min.

[0017] This application provides an application of a hard carbon material for the fabrication of electrodes.

[0018] This application provides a sodium-ion battery, including an electrode made of hard carbon material.

[0019] In summary, this application discloses a hard carbon material prepared from fossil-based carbonaceous raw materials, dopants, and pore-forming agents. The pore-forming agent serves as a template for constructing a hierarchical porous structure and effectively suppresses graphitization at high temperatures, maintaining the wide interlayer spacing of the hard carbon material. Combined with in-situ doping technology, sulfur / nitrogen active species released from nitrogen / sulfur heteroatoms are simultaneously introduced into the fossil-based carbonaceous raw materials. The release of these active species and the pore-forming process of the carbon framework are highly synergistically matched in time and space, resulting in a large number of uniformly distributed nitrogen / sulfur active sites on the surface of the formed pores. This ultimately constructs a synergistic sodium storage mode of "efficient pore transport - rapid adsorption / reaction at surface sites," significantly improving the sodium storage performance of the hard carbon material. Furthermore, this method avoids the introduction of halogen elements, mitigating corrosive hazards and balancing performance advantages with production safety.

[0020] This application discloses a method for preparing hard carbon materials, comprising the following steps: thoroughly grinding fossil-based carbonaceous raw materials, sulfur dopant, nitrogen dopant, and pore-forming agent, and mixing them uniformly to obtain a premix; calcining the premix under a nitrogen atmosphere using at least one stage of heat treatment, and generating nitrogen-sulfur co-doped coal tar pitch-based carbides in situ through crosslinking and dehydrogenation reactions driven by a high-temperature thermal field; finally, immersing the carbides in an acidic solution until no bubbles are generated on the surface of the carbides, thereby obtaining the hard carbon material. This preparation method belongs to solid-state heat treatment technology, which is simple, low-cost, and has good potential for large-scale production, making it suitable for the large-scale preparation of sodium-ion battery anode materials.

[0021] Compared with existing technologies, this invention achieves precise control of the micropore structure of hard carbon materials through the synergistic use of pore-forming technology and in-situ nitrogen-sulfur co-doping technology, enabling hard carbon materials to have both excellent cycle stability and rate performance in sodium ion storage applications. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The first charge-discharge curves of the hard carbon anodes prepared in Examples 1-3 at a current density of 0.05C are shown.

[0024] Figure 2The first charge-discharge curves of the hard carbon anodes prepared in Examples 1, 4, and 5 at a current density of 0.05C are shown.

[0025] Figure 3 The first charge-discharge curves of the hard carbon anodes prepared in Examples 6-9 at a current density of 0.05C are shown.

[0026] Figure 4 The first charge-discharge curves of the hard carbon anodes prepared in Examples 8, 10, and 11 at a current density of 0.1 A / g are shown.

[0027] Figure 5 The first charge-discharge curves of the hard carbon anodes prepared in Examples 8, 12, and 13 at a current density of 0.1 A / g are shown.

[0028] Figure 6 The first charge-discharge curves of the hard carbon anodes prepared in Examples 8 and 14 at a current density of 0.05C are shown.

[0029] Figure 7 The first charge-discharge curves of the hard carbon anodes prepared in Examples 8 and 15 at a current density of 0.05C are shown.

[0030] Figure 8 The first charge-discharge curves of the hard carbon anodes prepared in Examples 8 and 16 at a current density of 0.05C are shown.

[0031] Figure 9 The first charge-discharge curves of the hard carbon anodes prepared in Examples 8 and 17 at a current density of 0.05C are shown.

[0032] Figure 10 Scanning electron microscope (SEM) image of the hard carbon anode prepared in Example 8;

[0033] Figure 11 Energy dispersive X-ray spectroscopy (EDS) of the hard carbon anode prepared in Example 8;

[0034] Figure 12 The X-ray diffraction (XRD) pattern of the hard carbon anode prepared in Example 8;

[0035] Figure 13 The Raman spectrum of the hard carbon anode prepared in Example 8. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments in this application specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.

[0037] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship shown, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0039] The raw materials used in this invention are not particularly restricted in their source; they can be purchased on the market or prepared using conventional methods known to those skilled in the art.

[0040] This application provides a hard carbon material comprising the following components in parts by weight: 100 parts of fossil-based carbonaceous raw material; 200-280 parts of dopant, wherein the dopant includes at least one of sulfur dopant and nitrogen dopant; and 3-15 parts of pore-forming agent.

[0041] In some embodiments, the dopant includes 100-140 parts of sulfur dopant and 100-140 parts of nitrogen dopant. It should be noted that this invention employs pore-forming technology and in-situ nitrogen-sulfur co-doping technology to simultaneously introduce nitrogen and sulfur heteroatoms into the formed porous structure. This significantly enhances the sodium ion insertion / extraction kinetics and constructs abundant active sites, greatly strengthening the adsorption and storage capacity of sodium on the surface of hard carbon materials. Furthermore, the principles of the pore-forming agent and dopant are as follows: fossil-based carbonaceous raw materials can construct a carbon skeleton with a certain interlayer spacing during carbonization; the pore-forming agent acts as a template to construct a hierarchical porous structure on the carbon skeleton during carbonization, and the alkaline environment it provides can stabilize the crosslinking network of the fossil-based carbonaceous raw materials during the pre-crosslinking stage, effectively suppressing its graphitization tendency at high temperatures, thereby maintaining the wide interlayer spacing of the hard carbon material; the sulfur or nitrogen dopant releases sulfur / nitrogen active species respectively at a suitable decomposition temperature, achieving in-situ and uniform doping with the forming carbon skeleton. More importantly, the pore-forming process and the doping process are highly matched in terms of time and space, which modifies the pore surface of the carbon skeleton with a large number of nitrogen / sulfur active sites, ultimately constructing a highly efficient sodium storage mode of "pore transport - rapid adsorption / reaction of surface active sites".

[0042] In some embodiments, the fossil-based carbonaceous raw material is a by-product of coal chemical or petrochemical processes, with a carbon content ≥85wt% and a polycyclic aromatic hydrocarbon content ≥70wt%. Specifically, the fossil-based carbonaceous raw material includes at least one of pitch, coal tar, and petroleum coke. In some specific embodiments, coal pitch is specifically coal tar pitch, and commercially available coal tar pitch can be used, with optional models including Kejing 250, Kejing 280, Kelude A, and Kelude E.

[0043] In some embodiments, the sulfur dopant includes at least one of elemental sulfur, thiourea, sodium thiosulfate, ammonium persulfate, thioacetamide, benzothiophene, and aminosulfonic acid.

[0044] In some embodiments, the nitrogen dopant includes at least one of urea, melamine, pyridine, ethylenediamine, ammonium chloride, polyvinylpyrrolidone, polyacrylonitrile, polyaniline, polydopamine, and chitosan.

[0045] In some embodiments, the pore-forming agent includes at least one of magnesium oxide, zinc oxide, and calcium oxide.

[0046] In some preferred embodiments, the fossil-based carbonaceous raw material is coal tar pitch; the sulfur dopant is sodium thiosulfate; the nitrogen dopant is polyvinylpyrrolidone; and the pore-forming agent is magnesium oxide.

[0047] It should be noted that magnesium oxide not only acts as a template to create a hierarchical porous structure during carbonization, but its alkaline environment also helps stabilize the crosslinking network of coal tar pitch in the pre-crosslinking stage, inhibiting its graphitization tendency at high temperatures and maintaining the wide interlayer spacing of the carbon skeleton. Simultaneously, sodium thiosulfate and polyvinylpyrrolidone release sulfur and nitrogen active species, respectively, at suitable decomposition temperatures, which in-situ and uniformly dope the forming carbon skeleton. Furthermore, in terms of raw material selection, other sulfur dopants (such as thiourea and elemental sulfur) can be used to replace sodium thiosulfate, or zinc oxide and calcium oxide can be used to replace magnesium oxide as pore-forming agents. However, these alternatives tend to lead to uneven sulfur doping or poor pore structure distribution, thus affecting its electrical properties.

[0048] This application provides a method for preparing a hard carbon material, including the following steps:

[0049] Step S1: Grind and mix the fossil-based carbonaceous raw material, sulfur dopant, nitrogen dopant and pore-forming agent evenly to obtain a premix.

[0050] Step S2: Under nitrogen atmosphere protection, the premix is ​​calcined to obtain carbides;

[0051] Step S3: Immerse the carbide in an acidic solution until no more bubbles are generated on the surface of the carbide to obtain hard carbon material.

[0052] It should be noted that the preparation method of hard carbon materials is based on solid-state heat treatment: sulfur dopant, nitrogen dopant, pore-forming agent, and fossil-based carbonaceous raw materials are uniformly mixed, and then cross-linking and dehydrogenation reactions are carried out under a high-temperature thermal field to prepare nitrogen-sulfur co-doped coal tar pitch-based hard carbon materials in situ. The performance advantages of this hard carbon material stem from the synergistic regulatory effect of nitrogen, sulfur, and pore-forming agent: the three elements jointly optimize the microcrystalline structure, pore structure, and surface active sites of the hard carbon material, giving it both good cycle stability and rate performance in sodium-ion storage applications. In addition, this preparation method is simple, low-cost, and easy to scale up, making it suitable for the large-scale preparation of sodium-ion battery anode materials.

[0053] In some embodiments, the acidic solution includes at least one of hydrochloric acid solution, sulfuric acid solution, and nitric acid solution. More specifically, the molar concentration of the acidic solution is 1~5 mol / L.

[0054] In some embodiments, during the calcination process, the calcination temperature is 1300℃~1500℃, the calcination time is 1h~3h, and the heating rate is 1℃ / min~15℃ / min. More specifically, the heating rate is 3℃ / min, 5℃ / min, or 10℃ / min. It should be noted that by precisely controlling the above-mentioned calcination temperature, the initial charge specific capacity and initial coulombic efficiency of the hard carbon material can be optimized separately.

[0055] In some embodiments, before calcination, the premix is ​​subjected to sulfidation treatment. The sulfidation treatment step is as follows: the premix is ​​placed at 300~400℃ and kept at that temperature for 0.5h~3h; wherein the heating rate is 1℃ / min~10℃ / min.

[0056] It should be noted that the aforementioned sulfidation treatment and subsequent calcination treatment constitute a two-step gradient calcination process. This process design can be used to specifically control the initial charge specific capacity and initial coulombic efficiency of the premix, and can in particular significantly improve the initial coulombic efficiency.

[0057] This application provides an application of hard carbon material for preparing electrodes.

[0058] This application provides a sodium-ion battery, including an electrode made of hard carbon material.

[0059] The applicant further provides the following specific embodiments to describe the present invention. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0060] Example 1

[0061] This invention provides a method for preparing in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon materials, comprising the following steps:

[0062] Step S1: Take 2g of coal tar pitch (Kejing 250), 2g of sodium thiosulfate, and 2g of magnesium oxide and place them in a mortar. Grind and mix them thoroughly until they are homogeneous to obtain a premix.

[0063] Step S2: Transfer the premix to the corundum boat, then place the corundum boat carrying the premix in the central area of ​​the muffle furnace, set the heating rate of the muffle furnace to 5℃ / min, heat to 300℃ at this heating rate, and hold at this temperature for 1h for pre-crosslinking treatment; after the holding time is completed, cool to room temperature, evacuate the muffle furnace, and then introduce nitrogen to atmospheric pressure to completely remove the residual air in the muffle furnace;

[0064] Step S3: Under nitrogen atmosphere protection, the internal temperature of the muffle furnace is raised to 1300℃ at a heating rate of 10℃ / min, and held at this temperature for 3 hours for carbonization treatment to obtain carbides.

[0065] Step S4: After the carbide cools naturally, wash the carbide with a 3 mol / L hydrochloric acid solution until no more bubbles are generated, to obtain an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material.

[0066] This embodiment also provides a method for preparing a sodium-ion battery, including the following steps:

[0067] Step S1, Preparation of hard carbon anode: Take 10 mg of polyvinylidene fluoride, add 200 μL of N-methylpyrrolidone, stir for 5 minutes using a vacuum degassing mixer, then add 80 mg of the hard carbon material prepared in this example and 10 mg of SuperP (Termec AG, Switzerland). ® (Li Conductive Carbon) was stirred for another 5 minutes using a vacuum degassing mixer to ensure thorough mixing of all components and obtain a homogeneous and stable slurry. The slurry was then evenly coated onto a clean copper foil surface using a scraper. The copper foil was then vacuum dried at 60°C for 12 hours to obtain a loading of 1–2 mg / cm³. -2 The negative electrode.

[0068] Step S2, Half-cell assembly: In a glove box protected by argon atmosphere, the cells are stacked in the following order: negative electrode shell - gasket - sodium sheet - glass fiber separator - electrolyte - negative electrode - gasket - spring sheet - positive electrode shell. After assembly, the cells are sealed using a button cell sealing machine to obtain a sodium-ion battery. The electrolyte is a 1 mol / L sodium hexafluorophosphate solution and the solvent is diethylene glycol dimethyl ether.

[0069] Step S3, Performance Testing: The assembled sodium-ion battery was tested for electrochemical performance using the Newway Battery Testing System. The test voltage window was set to 0.01~2.0V (0.05C current density or (Current density). Test results show that at a current density of 0.05C, the initial charge specific capacity of the negative electrode can reach 291.0 mAh / g, and the initial coulombic efficiency is 42.9%. It should be noted that in the embodiments of this application, the current test density can be adjusted according to actual testing; for example, it can also be adjusted to... .

[0070] Examples 2 to 5

[0071] Examples 2-5 provide a method for preparing an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material and a method for preparing a sodium-ion battery. The difference from Example 1 is that the amounts of sodium thiosulfate and magnesium oxide added are different, as detailed in Table 1. The remaining steps are the same as in Example 1, and the test results are shown in Table 1.

[0072] Example 6

[0073] This invention provides a method for preparing an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material and a method for preparing a sodium-ion battery, comprising the following steps:

[0074] Step S1: Take 2g of coal tar pitch (Kejing 250), 2g of sodium thiosulfate, 2g of magnesium oxide, and 0.06g of polyvinylpyrrolidone and place them in a mortar. Grind and mix them thoroughly until they are homogeneous to obtain a premix.

[0075] Step S2: Transfer the premix to the corundum boat, then place the corundum boat carrying the premix in the central area of ​​the muffle furnace, set the heating rate of the muffle furnace to 5℃ / min, heat to 300℃ at this heating rate, and hold at this temperature for 1h for pre-crosslinking treatment; after the holding time is completed, cool to room temperature, evacuate the muffle furnace, and then introduce nitrogen to atmospheric pressure to completely remove the residual air in the muffle furnace;

[0076] Step S3: Under nitrogen atmosphere protection, the internal temperature of the muffle furnace is raised to 1300℃ at a heating rate of 10℃ / min, and held at this temperature for 3 hours for carbonization treatment to obtain carbides.

[0077] Step S4: After the carbide cools naturally, wash the carbide with a 3 mol / L hydrochloric acid solution until no more bubbles are generated, to obtain an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material.

[0078] This embodiment also provides a method for preparing a sodium-ion battery, the preparation steps of which are the same as in Example 1, and the test results are shown in Table 1.

[0079] Examples 7 to 9

[0080] Examples 7-9 provide a method for preparing an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material and a method for preparing a sodium-ion battery. The difference from Example 1 is that the amount of polyvinylpyrrolidone added is different, as detailed in Table 1. The remaining steps are the same as in Example 1, and the test results are shown in Table 1.

[0081] Examples 10-11

[0082] Examples 10 and 11 provide a method for preparing an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material and a method for preparing a sodium-ion battery. The difference from Example 8 is that the carbonization time under a nitrogen atmosphere is different, as detailed in Table 1. The remaining steps are the same as in Example 1, and the test results are shown in Table 1.

[0083] Examples 12-13

[0084] Examples 12 and 13 provide a method for preparing an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material and a method for preparing a sodium-ion battery. The difference from Example 8 is that the heating rate is different under a nitrogen atmosphere, as detailed in Table 1. The remaining steps are the same as in Example 1, and the test results are shown in Table 1.

[0085] Examples 14-16

[0086] Examples 14-16 provide a method for preparing an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material and a method for preparing a sodium-ion battery. The difference from Example 8 is that magnesium oxide, sodium thiosulfate, and polyvinylpyrrolidone are replaced by equal amounts of calcium oxide, thiourea, and melamine, respectively.

[0087] Example 17

[0088] This invention provides a method for preparing an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material and a method for preparing a sodium-ion battery, comprising the following steps:

[0089] Step S1: Take 2g of coal tar pitch (Kejing 250), 2g of sodium thiosulfate, 2g of magnesium oxide, and 0.2g of polyvinylpyrrolidone and place them in a mortar. Grind and mix them thoroughly until they are homogeneous to obtain a premix.

[0090] Step S2: Transfer the premix to the corundum boat, then place the corundum boat carrying the premix in the central area of ​​the muffle furnace, evacuate the muffle furnace, and then introduce nitrogen to atmospheric pressure to completely remove the residual air inside the muffle furnace; under nitrogen atmosphere protection, raise the internal temperature of the muffle furnace to 1300℃ at a heating rate of 10℃ / min, and hold at this temperature for 3 hours for carbonization treatment to obtain carbides;

[0091] Step S3: After the carbide cools naturally, wash the carbide with a 3 mol / L hydrochloric acid solution until no more bubbles are generated, to obtain an in-situ nitrogen-sulfur co-doped coal tar pitch-based hard carbon material.

[0092] This embodiment also provides a method for preparing a sodium-ion battery, the preparation steps of which are the same as in Example 1, and the test results are shown in Table 1.

[0093] Table 1. Electrical performance characterization of sodium-ion batteries

[0094]

[0095] Based on the data in Table 1 and Figures 1-9 It can be seen that the sodium-ion battery assembled from the hard carbon material prepared in Example 8 exhibits excellent electrochemical performance: not only is the initial coulombic efficiency high, but its initial charge specific capacity is also significantly better than that of other examples. To further demonstrate the intrinsic relationship between the structural characteristics and performance advantages of the hard carbon material, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy were performed on the hard carbon anode of Example 8. The results are as follows: Figures 10-13 As shown. Figure 10The SEM characterization image of the hard carbon anode provided in Example 8 shows that the hard carbon anode has a rich and interconnected pore structure, which can provide sufficient space for the rapid transport and efficient storage of sodium ions. Figure 11 The EDS spectrum and elemental distribution results for the hard carbon anode are shown. Figure 11 The display shows that carbon, nitrogen, and sulfur are uniformly distributed on the surface of the hard carbon anode, indicating that nitrogen and sulfur dual heteroatoms have been successfully doped into the carbon matrix. Figure 12 The XRD pattern of the hard carbon anode shows that the phase of the hard carbon anode is mainly carbon, with carbon (002) characteristic peaks appearing in the range of 20° to 30°, and no obvious by-product or impurity diffraction peaks were detected in the pattern. Figure 13 The Raman spectrum of the hard carbon anode shows a D / G peak ratio of 0.69, indicating a suitable degree of graphitization; simultaneously, at 400 cm⁻¹... -1 The presence of a characteristic signal at the wavenumber further corroborates that sulfur has been successfully doped and is stably present in the carbon matrix.

[0096] The above are merely preferred embodiments of this application and are not intended to limit the present invention. Although this application has been described in detail with reference to examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A hard carbon material, characterized by, The components include the following mass parts: 100 parts of a fossil-based carbonaceous raw material; 200-280 parts of a dopant, and the dopant includes at least one of a sulfur dopant and a nitrogen dopant; 3-15 parts of a pore-forming agent.

2. The hard carbon material of claim 1, wherein, The fossil-based carbonaceous raw material includes at least one of asphalt, coal tar, and petroleum coke.

3. The hard carbon material of claim 1, wherein, The sulfur dopant includes at least one of elemental sulfur, thiourea, sodium thiosulfate, ammonium persulfate, thioacetamide, benzothiophene, and sulfamic acid.

4. The hard carbon material of claim 1, wherein, The nitrogen dopant includes at least one of urea, melamine, pyridine, ethylenediamine, ammonium chloride, polyvinylpyrrolidone, polyacrylonitrile, polyaniline, polydopamine, and chitosan.

5. The hard carbon material of claim 1, wherein, The pore-forming agent includes at least one of magnesium oxide, zinc oxide, and calcium oxide.

6. A method for producing the hard carbon material according to any one of claims 1 to 5, characterized by, The method includes the following steps: S1. Grinding and uniformly mixing the fossil-based carbonaceous raw material, the sulfur dopant, the nitrogen dopant, and the pore-forming agent to obtain a premix; S2. Under the protection of a nitrogen atmosphere, performing calcination treatment on the premix to obtain a carbide; S3. Immersing and washing the carbide in an acidic solution until no bubbles are generated on the surface of the carbide to obtain a hard carbon material.

7. The method of producing a hard carbon material according to claim 6, wherein During the calcination treatment, the calcination temperature is 1300-1500°C, the calcination time is 1-3 h, and the heating rate is 1-15°C / min.

8. The method of claim 6, wherein the hard carbon material is prepared by a process comprising: Before the calcination treatment, performing vulcanization treatment on the premix, and the vulcanization treatment includes the following steps: placing the premix in a 300-400°C environment for 0.5-3 h of heat preservation reaction, and the heating rate is 1-10°C / min.

9. Use of the hard carbon material according to any one of claims 1 to 5 or the hard carbon material obtained by the production method according to any one of claims 6 to 8, characterized in that, The method is used for preparing an electrode.

10. A sodium-ion battery, characterized in that, The electrode is prepared from the hard carbon material of any one of claims 1-5 or the hard carbon material obtained by the preparation method of any one of claims 6-8.

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