Preparation method and application of sodium ion battery small molecule carbon chain coordination composite hard carbon negative electrode material

Abstract

The application discloses a preparation method and application of a sodium ion battery small-molecule carbon chain coordination composite hard carbon negative electrode material, and relates to the technical field of new energy materials. The method uses small-molecule sugar and coal tar as raw materials, performs pre-carbonization on the small-molecule sugar in air to form a small-molecule carbon chain, then mixes the small-molecule carbon chain with the coal tar, and performs high-temperature carbonization under an inert atmosphere to obtain a hard carbon material, and a high-specific-capacity sodium ion battery is prepared by using the material. The method is simple in process, green and environment-friendly in raw materials, and suitable for batch production; and the prepared hard carbon material has excellent electrochemical performance and can be used as an ideal sodium ion battery negative electrode material.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, and in particular to a method for preparing and applying a sodium-ion battery small molecule sugar and coal tar-based hard carbon anode material. Background Technology

[0002] Lithium-ion batteries have become the mainstream technology in the energy storage field, especially in electric vehicles and mobile electronic devices. However, the relatively limited availability of lithium resources restricts their further promotion in large-scale energy storage. In contrast, sodium-ion batteries are closer to lithium-ion batteries in terms of physical and chemical properties, and sodium resources are abundant and cheaper, making them more suitable for large-scale energy storage applications. Electrode materials play a crucial role in the composition of sodium-ion batteries. Although various positive electrode materials have been developed, high-performance anode materials to match them are still insufficient. Therefore, exploring and developing efficient sodium-ion battery anode materials is particularly important.

[0003] Hard carbon is considered a potential candidate for anode materials in sodium-ion batteries, mainly due to its structural stability and abundance of defects. As a carbon material that is difficult to graphitize, hard carbon consists of randomly arranged graphite microcrystals with numerous microscopic defects. These structural features provide it with more active sites for sodium storage, thereby enhancing its sodium-ion storage capacity.

[0004] The search for low-cost, high-performance hard carbon anode materials has become one of the core challenges in this field. Among numerous carbon source precursors, biomass materials have attracted widespread attention from researchers due to their wide availability, renewability, and environmental friendliness. However, traditional biomass materials are complex in composition, containing varying proportions of cellulose, hemicellulose, lignin, inorganic metal salts, and ash, resulting in significant batch-to-batch variations and making precise control of the microstructure difficult. Therefore, shifting focus from complex biomass to small-molecule sugars with higher purity and more defined structures after extraction has become an important development direction for the preparation of high-purity hard carbon materials. Small-molecule sugars have highly regular molecular structures, short molecular chains, and are rich in oxygen-containing functional groups such as carbon-oxygen bonds (CO, C=O) and hydroxyl groups (-OH). Compared with high-molecular-weight, complex biomass, small-molecule sugars not only have extremely low ash content and high purity, but also avoid the adverse effects of impurities on the electrochemical performance of batteries from the source. At the same time, their good solubility and melting characteristics make them easy to mix uniformly with other components or modifiers at the molecular level, providing great convenience for the controllable design of precursors.

[0005] Despite the significant advantages of small-molecule sugars, the direct pyrolysis of them to prepare hard carbon suffers from several serious drawbacks that hinder their industrial application. First, the structure is prone to collapse, making it difficult to form closed pores. Small-molecule sugars lack a natural rigid framework and melt easily in the initial stages of pyrolysis. As the temperature rises, the abundant oxygen-containing functional groups undergo violent degassing, producing a foaming effect that leads to uncontrolled expansion of the material. The resulting carbon framework is extremely loose and porous, making it difficult to form the dense, closed-pore structure required for efficient sodium storage, resulting in low initial efficiency and poor electrochemical performance. Second, due to the loose structure, excessive specific surface area, and numerous open pores of the sintered product, it excessively consumes electrolyte when used as a negative electrode, forming a solid electrolyte interface. This leads to significant irreversible sodium consumption, resulting in low initial coulombic efficiency and deteriorating battery cycle life and energy density. Furthermore, the low residual carbon yield and high manufacturing cost, coupled with the loss of a large amount of elements in gaseous form during pyrolysis, result in a low final carbon yield (typically below 20%). This not only wastes raw materials but also significantly increases manufacturing costs, causing it to lose its low-cost competitive advantage.

[0006] Coal tar, a byproduct of the coal coking industry, is a widely available and extremely inexpensive liquid mixture. Chemically, coal tar is rich in polycyclic aromatic hydrocarbons (PAHs) and various aromatic compounds, possessing a highly developed planar conjugated carbon ring structure and extremely high carbon skeleton density. When this liquid coal tar, rich in rigid aromatic rings, combines with pre-carbonized small-molecule sugars, the two exhibit structural complementarity at the molecular level. Due to its excellent fluidity and wettability, coal tar can deeply penetrate and encapsulate the amorphous carbon chains and defect pores retained by the pre-carbonized sugars. During subsequent heat treatment and cross-linking, the PAH molecules of coal tar undergo strong π-π interactions and chemical recombination with the carbon chains generated from sugar decomposition. This combination effectively compensates for the inherent limitations of small-molecule sugars due to the lack of a rigid three-dimensional skeleton. In this process, coal tar acts as both a molecular skeleton guide and a high-temperature binder. Its aromatic microdomains not only embed into the sugar-derived carbon skeleton but also, due to their excellent thermal stability, effectively suppress the structural collapse of small-molecule sugars caused by violent foaming and expansion during high-temperature pyrolysis.

[0007] Combining the two materials resulted in a novel composite hard carbon material. The original loose, porous, and fragile honeycomb morphology of carbonized sugars was transformed into dense, smooth-surfaced, and highly fusible solid bulk particles. At the microscopic level, the material exhibits an ideal composite configuration, with coal tar-derived graphite-like microcrystals constructing a robust carbon framework that effectively supports and stabilizes the abundant closed-cell structure derived from sugars.

[0008] By leveraging the complementary advantages of the aromatic fused rings of coal tar and the carbon chain structure of pre-carbonized small-molecule sugars, an effective strategy for preparing high-efficiency, high-compact, and high-yield hard carbon anodes from low-cost precursors is proposed. This innovative design overcomes the technical bottleneck of large-scale production of high-performance biomass hard carbon and is expected to promote the industrial application of sodium-ion batteries in energy storage and power fields. Summary of the Invention

[0009] To address the shortcomings of existing small-molecule sugars, such as easy foaming and collapse during direct pyrolysis, low residual carbon content, and poor initial efficiency, this invention aims to provide a method for preparing and applying a small-molecule carbon chain coordination composite hard carbon anode material for sodium-ion batteries. This invention utilizes a specific mechanical mixing process, leveraging the high viscosity and aromatic fused-ring structure of coal tar to encapsulate and confine pre-carbonized small-molecule sugars, effectively suppressing their severe degassing and foaming at high temperatures, thereby constructing a dense composite carbon framework with low specific surface area and high closed-pore ratio. This strategy improves the initial coulombic efficiency and cycle life of hard carbon while effectively controlling the preparation cost by relying on the high residual carbon content of coal tar, providing a practical solution for the large-scale production of high-performance sodium-ion battery anodes.

[0010] This invention provides a method for preparing and applying a small-molecule carbon chain coordination composite hard carbon anode material for sodium-ion batteries. The method first involves low-temperature pre-carbonizing small-molecule sugars in air to construct an initial rigid framework. Subsequently, the sugars are mechanically mixed with coal tar at a specific mass ratio, utilizing the binding and confinement effect of the coal tar to encapsulate the pre-carbonized small-molecule sugar particles and suppress foaming and collapse. Finally, high-temperature co-carbonization is performed under an inert atmosphere, promoting structural recombination at the molecular level, ultimately producing a composite hard carbon anode material with high density, high closed-pore volume, and excellent sodium storage performance.

[0011] Firstly, the preparation method of the hard carbon anode material is as follows:

[0012] Step 1): Pre-carbonize the small molecule sugars to obtain pre-carbonized materials.

[0013] Step 2): The small molecule sugars in Step 1) are one of glucose, fructose, sorbitol, galactose, pentose aldose, sucrose, maltose, and lactose, or a mixture thereof in any proportion.

[0014] Step 3): The pre-carbonization temperature in Step 1) is 150-700 ℃, the pre-sintering time is 1-24h, and the heating rate is 1-10 ℃ / min.

[0015] Step 4): Mix the pre-carbonized material obtained in Step 1) with coal tar to obtain a mixture material. The mass ratio of the pre-carbonized small molecule sugar to the coal tar is 9:1-1:9.

[0016] Step 5): The mixing method in Step 4) is mechanical mixing.

[0017] Step 6): The mixture powder obtained in step 4) is heated to 800-1600 °C under an inert atmosphere for 1-10 h with a heating rate of 1-120 °C / min to obtain the hard carbon material. The inert atmosphere is at least one of nitrogen or argon.

[0018] Secondly, the small molecule carbon chain coordination composite hard carbon anode material is prepared using the small molecule carbon chain coordination composite hard carbon anode material and its preparation method described in the first aspect.

[0019] Thirdly, a sodium-ion battery negative electrode sheet.

[0020] This includes the small molecule carbon chain coordination composite hard carbon anode material described in the second aspect.

[0021] Fourthly, a sodium-ion secondary battery.

[0022] This includes the negative electrode sheet described in the third aspect.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) This invention proposes a rigid framework confinement structure construction strategy. A porous rigid network formed by pre-carbonized small-molecule sugars is used to spatially confine the liquid coal tar filling it. During the high-temperature co-carbonization stage, this confinement effect effectively inhibits excessive graphitization of the coal tar, promoting the widening of the carbon microcrystal interlayer spacing, thereby improving the insertion and extraction kinetics of sodium ions. Simultaneously, the two-phase precursors mutually constrain each other during the high-temperature crosslinking and shrinkage process, constructing abundant and uniform nanopores in situ within the material, providing numerous active sites for sodium ion filling and significantly enhancing the sodium storage capacity of the hard carbon material.

[0025] (2) This invention effectively solves the problem of low initial coulombic efficiency of small molecule sugar-derived hard carbon. By filling the pre-carbonized small molecule sugar porous framework with coal tar, a significant structural repair effect is achieved, effectively sealing the external openings and surface defects generated by sugar pyrolysis. This structural reshaping makes the surface of hard carbon particles smoother and denser, significantly reducing the specific surface area of ​​the material, thereby effectively suppressing the side reactions of the electrolyte and irreversible sodium consumption in the first cycle, and significantly improving the initial coulombic efficiency.

[0026] (3) This invention provides a practical and feasible process route for the large-scale production of high-performance hard carbon anodes. The selected precursors are widely available and inexpensive. Among them, the high residual carbon characteristics of coal tar effectively compensate for the low pyrolysis yield of small molecule sugars, significantly improving the overall carbon yield and thus greatly reducing the unit manufacturing cost of the material. At the same time, the process flow of air pre-carbonization-mechanical mixing-high temperature co-carbonization is simple, does not require the use of complex chemical reagents, and is highly compatible with existing industrial calcination equipment for anode materials, providing a solution with significant economic advantages for the industrial application of sodium-ion battery anodes. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope (SEM) image of the hard carbon material prepared in Example 1.

[0028] Figure 2 This is the charge-discharge curve for the first week of Example 1.

[0029] Figure 3 This is a graph showing the 0.2 C cycle performance of Example 1 in a sodium-ion battery.

[0030] Figure 4 This is a scanning electron microscope (SEM) image of the hard carbon material prepared in Example 2.

[0031] Figure 5 This is the charge-discharge curve for the first week of Example 2.

[0032] Figure 6 This is a graph showing the 0.2 C cycle performance of Example 2 in a sodium-ion battery.

[0033] Figure 7 This is a scanning electron microscope (SEM) image of the hard carbon material prepared in Example 3.

[0034] Figure 8 This is the charge-discharge curve for the first week of Example 3.

[0035] Figure 9 This is a graph showing the 0.2 C cycle performance of Example 3 in a sodium-ion battery.

[0036] Figure 10 This is a scanning electron microscope (SEM) image of the hard carbon material prepared in Example 4.

[0037] Figure 11 This is the charge-discharge curve for the first week of Example 4.

[0038] Figure 12 This is a graph showing the 0.2 C cycle performance of Example 4 in a sodium-ion battery.

[0039] Figure 13 This is a scanning electron microscope (SEM) image of the hard carbon material prepared in Comparative Example 1.

[0040] Figure 14 This is the charge-discharge curve for the first week of comparison example 1.

[0041] Figure 15 This is a graph showing the 0.2 C cycle performance of Comparative Example 1 in a sodium-ion battery.

[0042] Figure 16 This is a scanning electron microscope (SEM) image of the hard carbon material prepared in Comparative Example 2.

[0043] Figure 17 This is the charge-discharge curve of Comparative Example 2 during the first week.

[0044] Figure 18 This is a graph showing the 0.2 C cycle performance of Comparative Example 2 in a sodium-ion battery.

[0045] Figure 19 This is a scanning electron microscope (SEM) image of the hard carbon material prepared in Comparative Example 3.

[0046] Figure 20 This is the charge-discharge curve of Comparative Example 3 during the first week.

[0047] Figure 21 This is a graph showing the 0.2 C cycle performance of Comparative Example 3 in a sodium-ion battery. Detailed Implementation

[0048] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0049] Example 1

[0050] This embodiment provides a method for preparing and applying a small-molecule carbon chain coordination composite hard carbon anode material for sodium-ion batteries.

[0051] The preparation steps are as follows: Glucose was placed in air and heated to 250℃ at a heating rate of 5℃ / min, and held at this temperature for 12 h. After natural cooling, it was pre-ground to obtain pre-carbonized glucose powder. The pre-carbonized glucose and liquid coal tar were weighed at a mass ratio of 7:3 and transferred to a mechanical stirring device for strong shearing and mixing. After thorough mixing, the solid and liquid phases were highly fused to form a dense, semi-solid homogeneous mixed precursor with no obvious dry powder particles and high cohesion. The composite precursor was placed in a tube furnace and heated slowly to 1300℃ at a rate of 3℃ / min under an argon protective atmosphere, and held at this temperature for 3 h. After natural cooling, the product was pulverized, ground, and sieved to obtain a small molecule carbon chain coordination composite hard carbon anode material.

[0052] Figure 1 The image is a scanning electron microscope (SEM) image of the small molecule carbon chain coordination composite hard carbon anode material described in Example 1. It can be clearly seen that it is composed of blocky objects of different sizes, and there are fine particles present.

[0053] Assembly and electrochemical performance testing of button batteries:

[0054] The prepared small-molecule carbon chain coordination composite hard carbon anode material was mixed with conductive carbon black and carboxymethyl cellulose at a mass ratio of 90:5:5. A suitable amount of deionized water was added dropwise to the mixture, and after stirring, a uniform slurry was formed. The slurry was coated onto copper foil and vacuum dried at 80 °C for 12 hours. Anode sheets with a diameter of 11 mm were then cut. Using sodium metal as the counter electrode, a glass fiber filter membrane (Whatman GF / C) as the separator, a 1 mol / L NaPF6 solution in dimethyl ethylene glycol (DME) as the electrolyte, and a stainless steel shell as the outer casing, a 2025 button cell was assembled. Charge-discharge tests were performed using the Xinwei battery system, with a test voltage range of 0.01-2.0 V and a test temperature of room temperature. The test current density for the first three cycles was 0.1 C (1C=300 mA / g), followed by charge-discharge tests at a current density of 0.2 C.

[0055] Experimental results: The reversible specific capacity in the first cycle was 288.95 mAh / g ( Figure 2 The initial coulombic efficiency was 87.88%, the median voltage was 0.0789 V, and the specific capacity after 150 cycles was 241.2 mAh / g. Figure 3 ).

[0056] Example 2

[0057] This embodiment provides a method for preparing and applying a small-molecule carbon chain coordination composite hard carbon anode material for sodium-ion batteries.

[0058] The preparation steps are as follows: Glucose was placed in an air atmosphere and heated to 250℃ at a heating rate of 5℃ / min, and held at this temperature for 12 h. After natural cooling, it was pre-ground to obtain pre-carbonized glucose powder. The pre-carbonized glucose and liquid coal tar were weighed at a mass ratio of 3:7 and transferred to a mechanical stirring device for strong shearing and mixing. After thorough mixing, the solid and liquid phases were highly fused to form a dense, semi-solid homogeneous mixed precursor with no obvious dry powder particles and high cohesion. The composite precursor was placed in a tube furnace and heated slowly to 1300℃ at a rate of 3℃ / min under an argon protective atmosphere, and held at this temperature for 3 h. After natural cooling, the product was pulverized, ground, and sieved to obtain a small molecule carbon chain coordination composite hard carbon anode material.

[0059] Figure 4 The image is a scanning electron microscope (SEM) image of the small molecule carbon chain coordination composite hard carbon anode material described in Example 2, which clearly shows that it is composed of blocky objects of different sizes.

[0060] As in Example 1, electrodes were prepared, batteries were assembled, and electrochemical tests were performed.

[0061] Experimental results: The reversible specific capacity in the first cycle was 289.34 mAh / g ( Figure 5 The initial coulombic efficiency was 88.75%, the median voltage was 0.0734 V, and the specific capacity after 150 cycles was 215.67 mAh / g. Figure 6 ).

[0062] Example 3

[0063] This embodiment provides a method for preparing and applying a small-molecule carbon chain coordination composite hard carbon anode material for sodium-ion batteries.

[0064] The preparation steps are as follows: Sucrose was placed in air and heated to 250℃ at a heating rate of 5℃ / min, and held at this temperature for 12 h. After natural cooling, it was pre-ground to obtain pre-carbonized sucrose powder. The pre-carbonized sucrose and liquid coal tar were weighed at a mass ratio of 7:3 and transferred to a mechanical stirring device for strong shearing and mixing. After thorough mixing, the solid and liquid phases were highly fused, forming a dense, semi-solid homogeneous mixed precursor with no obvious dry powder particles and high cohesion. The composite precursor was placed in a tube furnace and heated slowly to 1300℃ at a rate of 3℃ / min under an argon protective atmosphere, and held at this temperature for 3 h. After natural cooling, the product was pulverized, ground, and sieved to obtain a small-molecule carbon chain coordination composite hard carbon anode material.

[0065] Figure 7The image is a scanning electron microscope (SEM) image of the small molecule carbon chain coordination composite hard carbon anode material described in Example 3, which clearly shows that it is composed of blocky objects of varying sizes.

[0066] As in Example 1, electrodes were prepared, batteries were assembled, and electrochemical tests were performed.

[0067] Experimental results: The reversible specific capacity in the first cycle was 279.83 mAh / g ( Figure 8 The initial coulombic efficiency was 84.77%, the median voltage was 0.0753 V, and the specific capacity after 150 cycles was 203.11 mAh / g. Figure 9 ).

[0068] Example 4

[0069] This embodiment provides a method for preparing and applying a small-molecule carbon chain coordination composite hard carbon anode material for sodium-ion batteries.

[0070] The preparation steps are as follows: Sucrose was placed in air and heated to 250℃ at a heating rate of 5℃ / min, and held at this temperature for 12 h. After natural cooling, it was pre-ground to obtain pre-carbonized sucrose powder. The pre-carbonized sucrose and liquid coal tar were weighed at a mass ratio of 3:7 and transferred to a mechanical stirring device for strong shearing and mixing. After thorough mixing, the solid and liquid phases were highly fused, forming a dense, semi-solid homogeneous mixed precursor with no obvious dry powder particles and high cohesion. The composite precursor was placed in a tube furnace and heated slowly to 1300℃ at a rate of 3℃ / min under an argon protective atmosphere, and held at this temperature for 3 h. After natural cooling, the product was pulverized, ground, and sieved to obtain a small-molecule carbon chain coordination composite hard carbon anode material.

[0071] Figure 10 The image is a scanning electron microscope (SEM) image of the small molecule carbon chain coordination composite hard carbon anode material described in Example 4. It can be clearly seen that it is composed of blocky objects of different sizes, and spherical particles are also present.

[0072] As in Example 1, electrodes were prepared, batteries were assembled, and electrochemical tests were performed.

[0073] Experimental results: The reversible specific capacity in the first cycle was 297.45 mAh / g ( Figure 11 The initial coulombic efficiency was 88.78%, the median voltage was 0.0697 V, and the specific capacity after 168 cycles was 232.33 mAh / g. Figure 12 ).

[0074] Comparative Example 1

[0075] This comparative example provides coal tar-based hard carbon, its preparation method, and its applications.

[0076] The preparation steps are as follows: coal tar is directly heated to 1300 ℃ under an argon atmosphere at a heating rate of 3 ℃ / min and held for 3 h to obtain coal tar-based hard carbon.

[0077] Figure 13 The image is a scanning electron microscope (SEM) image of the coal tar-based hard carbon material described in Comparative Example 1, which clearly shows that it is composed of a large number of stacked fine particles.

[0078] As in Example 1, electrodes were prepared, batteries were assembled, and electrochemical tests were performed.

[0079] Experimental results: The first-cycle discharge specific capacity was 193.30 mAh / g ( Figure 14 The initial coulombic efficiency was 52.28%, the median voltage was 0.1317 V, and the specific capacity after 150 cycles was 154.63 mAh / g. Figure 15 ).

[0080] Comparative Example 2

[0081] This comparative example provides glucose-based hard carbon, its preparation method, and its applications.

[0082] The preparation steps are as follows: Glucose is directly heated to 1300 ℃ under an argon atmosphere at a heating rate of 3 ℃ / min and held for 3 h to obtain glucose-based hard carbon.

[0083] Figure 16 The image shown is a scanning electron microscope (SEM) image of the glucose-based hard carbon material described in Comparative Example 2, which clearly shows that it is composed of a large number of sheet-like objects of varying sizes.

[0084] As in Example 1, electrodes were prepared, batteries were assembled, and electrochemical tests were performed.

[0085] Experimental results: The first-cycle discharge specific capacity was 251.79 mAh / g ( Figure 17 The initial coulombic efficiency was 78.71%, the median voltage was 0.0822 V, and the specific capacity after 70 cycles was 241.24 mAh / g. Figure 18 ).

[0086] Comparative Example 3

[0087] This comparative example provides sucrose-based hard carbon, its preparation method, and its applications.

[0088] The preparation steps are as follows: Sucrose is directly heated to 1300 ℃ under an argon atmosphere at a heating rate of 3 ℃ / min and held for 3 h to obtain sucrose-based hard carbon.

[0089] Figure 19The image shown is a scanning electron microscope (SEM) image of the sucrose-based hard carbon material described in Comparative Example 3, which clearly shows that it is composed of a large number of sheet-like objects of varying sizes.

[0090] As in Example 1, electrodes were prepared, batteries were assembled, and electrochemical tests were performed.

[0091] Experimental results: The first-cycle discharge specific capacity was 244.22 mAh / g ( Figure 20 The initial coulombic efficiency was 80.33%, the median voltage was 0.0624 V, and the specific capacity after 50 cycles was 238.49 mAh / g. Figure 21 ).

Claims

1. A method for preparing and applying a small-molecule carbon chain coordination composite hard carbon anode material for sodium-ion batteries, characterized in that, Small molecule sugars are pre-carbonized in air to form small molecule carbon chains. Then, the pre-carbonized small molecule sugars are mixed with coal tar in a certain mass ratio and carbonized at high temperature in an inert atmosphere to obtain composite hard carbon materials.

2. The preparation method according to claim 1, characterized in that, The temperature for pre-carbonizing small molecule sugars in air is 150-700 ℃, preferably 200-400 ℃; the time is 1-24 h, preferably 8-15 h; and the heating rate is 1-10 ℃ / min, preferably 4-8 ℃ / min.

3. The preparation method according to claim 1, characterized in that, Small molecule sugars are one of glucose, fructose, sorbitol, galactose, pentose aldose, sucrose, maltose, lactose, or a mixture thereof in any proportion.

4. The preparation method according to claim 1, characterized in that, The mass ratio of pre-carbonized small molecule sugars to coal tar is 9:1-1:9, preferably 9:1-3:

7.

5. The preparation method according to claim 1, characterized in that, The mixing method is mechanical mixing; the pre-carbonized small molecule sugar powder and coal tar liquid are mixed uniformly at high speed in a high-speed mixer to obtain a semi-solid homogeneous mixture precursor material with high cohesion.

6. The preparation method according to claim 1, characterized in that, During the high-speed mixing stage, the residual oxygen-containing functional groups on the surface of the pre-carbonized small molecule sugars undergo surface chemical bonding such as hydrogen bonding and preliminary dehydration condensation with the polar aromatic groups in the coal tar. This chemical anchoring effect enables deep wetting of both the solid and liquid phases, and the coal tar firmly encapsulates the pre-carbonized small molecule sugar particles, macroscopically transforming them into a semi-solid homogeneous precursor with high cohesion.

7. The preparation method according to claim 1, characterized in that, The high-temperature carbonization temperature is 800-1600 ℃, preferably 900-1400 ℃; the carbonization time is 1-10 h, preferably 2-4 h; the heating rate is 1-120 ℃ / min, preferably 2-30 ℃ / min; and the inert atmosphere is at least one of nitrogen or argon.

8. The preparation method according to claim 1, characterized in that, During high-temperature carbonization, the amorphous short-chain carbon generated by the cracking of pre-carbonized small-molecule sugars undergoes in-situ coupling and covalent grafting with the rigid aromatic rings of coal tar, constructing a unique short-chain-aromatic ring chemical coordination structure. In this structure, the short-chain carbons are intercalated through cross-linking to widen the carbon layer spacing. At the same time, polycyclic aromatic hydrocarbons construct a rigid framework, which hinders the pore collapse during high-temperature carbonization.

9. The preparation method according to claim 1, characterized in that, This invention defines a novel dense-modified-framework co-intercalation composite hard carbon structure. The structure has a dense and smooth continuous surface on the outside, which repairs open defects and reduces specific surface area, thereby significantly improving the first coulombic efficiency. The inside is formed by cross-linking short-chain carbon with aromatic microcrystals to form a rigid framework, which seals the free space in situ into nanoscale closed pores, thereby achieving high-capacity sodium storage.

10. The application of the small molecule carbon chain coordination composite hard carbon anode material for sodium-ion batteries as described in claim 1, or the small molecule carbon chain coordination composite hard carbon prepared by the method described in any one of claims 2-9, as a sodium-ion battery anode material.

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