A closed-pore hard carbon material, a preparation method and application thereof

Abstract

The application relates to the technical field of negative electrode materials, and particularly discloses a closed-pore hard carbon material and a preparation method and application thereof. Fluorine-containing nitrogen-containing organic matter and a porous carbon matrix are dissolved in a solvent, mixed uniformly, impregnated under the condition of >= 110 DEG C and >= 7 MPa, and a hard carbon precursor is obtained; under an inert atmosphere, the hard carbon precursor is heated to 1300 DEG C-1500 DEG C within 5s-15s, and reacted for 2h-4h, and a closed-pore hard carbon material is obtained. The fluorine-containing nitrogen-containing organic matter is used as a pore-filling agent, and under the driving force of specific conditions, the pore-filling agent is fully filled into the internal pores of the porous carbon matrix, and then rapidly heated to high temperature to complete the carbonization of the porous carbon matrix and the pore-filling agent; the pore-filling agent grows a large number of functional groups such as C-F and C-N on the surface through high-temperature decomposition, and at the same time, a curved carbon layer is formed to block the open pores and form a closed-pore structure. The closed-pore hard carbon material is used as raw material of a battery negative electrode material, and the platform capacity and the initial efficiency of the battery can be significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of negative electrode materials, and particularly relates to a closed-pore hard carbon material and a preparation method and application thereof. BACKGROUND

[0002] Hard carbon has suitable interlayer distance and rich pore structure, and is low in cost, and is widely used as a negative electrode main material of a sodium ion battery. The charge-discharge curve of the hard carbon mainly includes a slope region above 0.1 V and a platform region below 0.1 V. The platform capacity is mainly dominated by the graphite layer and the closed pores of the hard carbon, and the closed pores can provide more than 80% of the platform capacity. Therefore, a large number of existing technologies prepare a negative electrode material by designing and adjusting the size, quantity and volume of the closed pores of the hard carbon material, and the capacity of the negative electrode material in an ether-based electrolyte is greater than or equal to 320 mAh / g, and the initial efficiency is greater than or equal to 85%.

[0003] Compared with an ester-based electrolyte, the ether-based electrolyte is high in cost, is easy to decompose at a high potential and corrodes an aluminum foil, and therefore the ester-based electrolyte is a primary choice for commercial application of the hard carbon. However, NaPF6 in the ester-based electrolyte has a higher dissociation energy than EC (ethylene carbonate) and DEC (diethyl carbonate), and therefore EC and DEC are decomposed in a large amount in a discharge process, so that a SEI (solid electrolyte membrane) layer that is thick, uneven and rich in organic components is formed, not only a large amount of sodium ions are consumed, but also filling of active sodium ions in the closed pores is hindered, and in addition, the mechanical property of the interface layer of the SEI layer dominated by the organic components is poor, and a slight expansion will cause the interface layer to crack, so that more electrolyte is consumed, and the resistance of sodium ions passing through the interface layer is also large. Therefore, the capacity of the hard carbon in the ester-based electrolyte is usually less than or equal to 280 mAh / g, and the initial efficiency is less than or equal to 75%.

[0004] Therefore, it is urgent to develop a preparation method of a hard carbon material, and to promote NaPF6 to be preferentially decomposed by reasonably designing the microstructure of the hard carbon when rich closed pores are formed, so as to improve the high platform capacity and the initial efficiency of the battery. SUMMARY

[0005] In view of the above problems, the present application provides a closed-pore hard carbon material and a preparation method and application thereof, the graphite domains formed by high-temperature decomposition of fluorine-containing nitrogen organic matter are used to block the open pores, and high-quality closed-pore hard carbon material is obtained; and the closed-pore hard carbon material is used as a negative electrode material, so that a uniform SEI layer dominated by inorganic matter is formed, and the platform sodium storage capacity and the initial efficiency of the battery are significantly improved.

[0006] To solve the above technical problems, the technical scheme provided by the present application is as follows:

[0007] In a first aspect, the present application provides a preparation method of a closed-pore hard carbon material, including the following steps:

[0008] S100, adding fluorine-nitrogen-containing organic matter and porous carbon matrix into a solvent, mixing uniformly, and performing impregnation at ≥110℃ and ≥7MPa to obtain a hard carbon precursor;

[0009] S200, under an inert atmosphere, the hard carbon precursor is heated to 1300℃-1500℃ within 5s-15s, and reacted to obtain a closed-pore hard carbon material.

[0010] Compared with the prior art, the preparation method of the closed-pore hard carbon material provided by the application uses fluorine-nitrogen-containing organic matter as a pore-filling agent, and under the action of driving force under specific conditions, the pore-filling agent is fully filled into the internal pores of the porous carbon matrix, and then quickly rises to high temperature (1300℃-1500℃) to complete the carbonization of the porous carbon matrix and the pore-filling agent; the pore-filling agent is decomposed at high temperature to grow a large number of C-F and C-N functional groups on the surface, and at the same time, a curved carbon layer is formed to block the open pores and form a closed-pore structure.

[0011] The C-F and C-N functional groups formed by the high-temperature decomposition of the pore-filling agent have strong electron-attracting power and can combine with sodium ions to form inorganic substances such as NaF and Na3N; at the same time, C-F, C-N and PF6 - have a strong ion-dipole interaction, which can promote the preferential decomposition of PF6 - and further form NaF. Based on the dual action of C-F and C-N, a uniform SEI layer rich in NaF and Na3N can be formed, which not only reduces the consumption of active sodium ions, but also accelerates the closed-pore filling dynamics of sodium ions. In addition, compared with the SEI layer dominated by organic matter, the SEI layer dominated by inorganic matter is thinner, the resistance of sodium ions passing through is smaller, and the dynamics is better; the mechanical properties of the SEI layer dominated by inorganic matter are better, and even if the structure of the electrode expands, it will not cause the interface layer to crack, thereby reducing the excessive consumption of electrolyte.

[0012] The application finds through a large number of experiments that if the heating rate in S200 is too low, a large amount of pore-filling agent will be decomposed, causing a large amount of C-F and C-N functional groups to escape, which greatly reduces the content of C-F and C-N functional groups in the hard carbon material; at the same time, excessive carbonization will cause the closed-pore structure of the hard carbon material to be completely blocked, reducing the sodium storage space and further reducing the battery capacity and initial efficiency. The application also finds through a large number of experiments that if the reaction temperature in S200 is too high, the porous carbon matrix and the pore-filling agent will be excessively carbonized, which will cause the interlayer spacing of the hard carbon material to be narrowed, which is not conducive to the sodium ions passing through the interlayer to reach the inside of the closed-pore structure, and the pore-filling agent will be completely blocked.

[0013] Preferably, in S100, the fluorine-nitrogen-containing organic matter includes at least one of perfluoropyridine amine, tetrafluoropyridine, trifluoromethyl pyrrole or pentafluoro pyrimidine.

[0014] For example, in S100, the tetrafluoropyridine includes at least one of 2,3,4,5-tetrafluoropyridine, 2,3,5,6-tetrafluoropyridine or 2,3,4,6-tetrafluoropyridine; and the trifluoromethylpyrrole includes at least one of 2-(trifluoromethyl)pyrrole or 3-(trifluoromethyl)pyrrole.

[0015] Preferably, in S100, the porous carbon substrate includes activated carbon.

[0016] Further preferably, in S100, the activated carbon has an average pore size of 1nm-2nm and a specific surface area of 1500m 2 2 / g-1700m

[0017] In the present application, the porous carbon substrate has certain porosity and adsorption effect, and the specific average pore size and specific surface area ensure the adsorption amount of the activated carbon to the pore filling agent, thereby providing a prerequisite for subsequent preparation of the closed pore hard carbon material.

[0018] Preferably, in S100, the solvent includes anhydrous ethanol and water in a volume ratio of (1-1.5):1.

[0019] The solvent of the present application can effectively dissolve the fluorine-nitrogen-containing organic matter, which is beneficial to the impregnation and adsorption of the porous carbon substrate to the pore filling agent.

[0020] Preferably, in S100, the mass-volume ratio of the fluorine-nitrogen-containing organic matter, the porous carbon substrate and the solvent is (2-4)g:(3-5)g:(40-60)mL.

[0021] It is found through a large number of experiments that if the amount of the fluorine-nitrogen-containing organic matter is too large, excessive adsorption will occur, and during the subsequent carbonization reaction, the excess pore filling agent will form curved graphite domains on the outside of the porous carbon substrate, thereby completely blocking the pore structure and narrowing the interlayer spacing of the hard carbon material.

[0022] Preferably, in S100, the impregnation pressure is 7MPa-10MPa, the impregnation temperature is 130℃-150℃, and the impregnation time is 3h-5h.

[0023] It is found through a large number of experiments that if the impregnation pressure is low or the impregnation temperature is low, the filling agent cannot fully enter the internal pores of the porous carbon substrate, thereby leading to insufficient opening of the pores at high temperature and less closed pore structure; if the impregnation pressure is high or the impregnation temperature is high, the filling agent will excessively enter the internal pores and surface of the porous carbon substrate, and after high-temperature decomposition, the pore structure may be completely blocked, reducing the sodium storage space.

[0024] Preferably, in S100, after the impregnation, the method further includes: water washing, drying, to obtain a hard carbon precursor.

[0025] ​For example, in S200, the inert atmosphere includes an argon atmosphere or a nitrogen atmosphere.

[0026] Preferably, in S200, the temperature is raised to 1300℃-1500℃ by microwave heating.

[0027] Microwave heating is to transfer heat from the inside of the material to the outside, and high temperature inside and low temperature outside can form more C-F and C-N functional groups. Further, when the closed pore hard carbon material is used as a negative electrode material, a uniform SEI layer dominated by inorganic matter (rich in NaF and Na3N) can be formed, reducing the consumption of active sodium ions and further improving the platform sodium storage capacity and initial efficiency of the battery.

[0028] Preferably, in S200, the temperature is raised to 1300℃-1500℃ within 5s-10s.

[0029] Preferably, in S200, the reaction time is 2h-4h.

[0030] In a second aspect, the application provides a closed pore hard carbon material prepared by the preparation method of the closed pore hard carbon material.

[0031] In a third aspect, the application provides a negative electrode material comprising the closed pore hard carbon material.

[0032] In a fourth aspect, the application provides the use of the negative electrode material in a sodium ion battery.

[0033] The application has the following advantages:

[0034] The application adopts an open pore to closed pore strategy, uses the graphite domain formed by high temperature decomposition of fluorine and nitrogen-containing organic matter to block the open pores, and obtains high-quality closed pore hard carbon material. Tests show that the closed pore hard carbon material provided by the application has a large closed pore structure, and the closed pore volume can reach 0.6cm 3 / g or more. When the closed pore hard carbon material is used as a raw material for a negative electrode material, the platform capacity of the sodium ion battery prepared can reach 310mAh / g or more, the initial efficiency can reach 95% or more, and the electrochemical properties are excellent. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Figure 1 is a TEM image of the closed pore hard carbon material in Example 1 of the application;

[0036] Figure 2 Figure 2 is a TEM image of the closed pore hard carbon material in Example 2 of the application;

[0037] Figure 3 Figure 3 is a TEM image of the closed pore hard carbon material in Comparative Example 1 of the application;

[0038] Figure 4TEM image of the closed-pore hard carbon material in Inventive Comparative Example 4;

[0039] In the figure, the position circled by the circle represents the closed-pore structure. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0041] In the embodiments of the present application, the water is deionized water. If the manufacturer is not specified, it is a product that can be obtained through market purchase.

[0042] Example 1

[0043] The present embodiment provides a preparation method of a closed-pore hard carbon material, comprising the following steps:

[0044] S100, 2g of fluorine-containing nitrogen organic matter (perfluoropyridine amine) is dissolved in 40mL of solvent (mixed by volume ratio of 1:1 of anhydrous ethanol and water), 3g of activated carbon (average pore size of 1.2nm, specific surface area of 1500m 2 / g) is added to the obtained pore-filling solution, after mixing and stirring for 2h, the obtained mixed system is placed in a reaction kettle, impregnation is carried out at 140℃ and 7MPa, after holding for 4h, water washing is carried out, drying is carried out at 80℃ for 12h, and a hard carbon precursor is obtained.

[0045] S200, under a nitrogen atmosphere, the hard carbon precursor is heated by microwave heating, and the temperature is raised to 1400℃ within 7s, after reaction for 3h, the temperature is cooled to room temperature, and a closed-pore hard carbon material is obtained.

[0046] The closed-pore hard carbon material prepared in the present embodiment is subjected to transmission electron microscope test, and the results are shown in Figure 1 From the figure, it can be seen that the closed-pore hard carbon material prepared in the present embodiment has a large number of closed pores and a large closed pore volume.

[0047] Example 2

[0048] The present embodiment provides a preparation method of a closed-pore hard carbon material, comprising the following steps:

[0049] S100, 2g of fluorine-containing nitrogen organic matter (perfluoropyridine amine) is dissolved in 40mL of solvent (mixed by volume ratio of 1:1 of anhydrous ethanol and water), 3g of activated carbon (average pore size of 1.2nm, specific surface area of 1500m 2After mixing and stirring for 3 hours, the resulting mixture was placed in a reactor and impregnated at 140°C and 8MPa. After holding at the temperature and pressure for 4 hours, it was washed with water and dried at 80°C for 12 hours to obtain the hard carbon precursor.

[0050] S200. Under an argon atmosphere, the hard carbon precursor is heated to 1300℃ within 5s by microwave heating. After reacting for 3.8h, it is cooled to room temperature to obtain closed-cell hard carbon material.

[0051] The closed-cell hard carbon material prepared in this embodiment was tested by transmission electron microscopy, and the results are as follows: Figure 2 As shown in the figure, the closed-cell hard carbon material prepared in this embodiment has a large number of closed pores and a large pore volume.

[0052] Example 3

[0053] This embodiment provides a method for preparing closed-cell hard carbon material, including the following steps:

[0054] S100. Dissolve 4g of a fluorinated nitrogen-containing organic compound (3-(trifluoromethyl)pyrrole) in 60mL of solvent (prepared by mixing anhydrous ethanol and water in a volume ratio of 1.5:1). Add 5g of activated carbon (average pore size 1.6nm, specific surface area 1600m²) to the resulting pore-filling solution. 2 After mixing and stirring for 4 hours, the resulting mixture was placed in a reactor and impregnated at 150°C and 10MPa. After holding at the temperature and pressure for 3 hours, it was washed with water and dried at 80°C for 12 hours to obtain the hard carbon precursor.

[0055] S200. Under a nitrogen atmosphere, the hard carbon precursor is heated to 1500℃ within 11s by microwave heating. After reacting for 2.3h, it is cooled to room temperature to obtain closed-cell hard carbon material.

[0056] Example 4

[0057] This embodiment provides a method for preparing closed-cell hard carbon material, including the following steps:

[0058] S100. Dissolve 3g of a fluorine-containing nitrogenous organic compound (pentafluoropyrimidine) in 45mL of solvent (prepared by mixing anhydrous ethanol and water in a 1:1 volume ratio). Add 4g of activated carbon (average pore size 2nm, specific surface area 1500m²) to the resulting pore-filling solution. 2 After mixing and stirring for 3 hours, the resulting mixture was placed in a reactor and impregnated at 130°C and 7MPa. After holding at the temperature and pressure for 5 hours, it was washed with water and dried at 80°C for 12 hours to obtain the hard carbon precursor.

[0059] S200, under the atmosphere of nitrogen, the hard carbon precursor is heated by microwave within 14s to 1500℃, and after 3h of reaction, it is cooled to room temperature to obtain the closed-pore hard carbon material.

[0060] Example 5

[0061] The embodiment provides a preparation method of a closed-pore hard carbon material, which comprises the following steps:

[0062] S100, 3g of fluorine and nitrogen-containing organic matter (2,3,4,6-tetrafluoropyridine and 2-(trifluoromethyl)pyrrole with equal mass) is dissolved in 55mL of solvent (mixed by 1:1 of anhydrous ethanol and water by volume ratio), 4g of activated carbon (with an average pore size of 1nm and a specific surface area of 1700m 2 / g) is added into the obtained pore-filling solution, and after 3h of mixing and stirring, the obtained mixed system is placed into a reaction kettle for impregnation at 140℃ and 9MPa, and after 4h of heat preservation and pressure preservation, it is washed with water and dried at 80℃ for 12h to obtain a hard carbon precursor.

[0063] S200, under the atmosphere of argon, the hard carbon precursor is heated by microwave within 9s to 1400℃, and after 2.5h of reaction, it is cooled to room temperature to obtain the closed-pore hard carbon material.

[0064] Example 6

[0065] The embodiment provides a preparation method of a closed-pore hard carbon material, which is similar to example 1, and the difference is that in S100, the adding amount of the fluorine and nitrogen-containing organic matter (perfluoropyridine amine) is 5g. The remaining conditions are the same as those in example 1, and details are not described herein again.

[0066] Example 7

[0067] The embodiment provides a preparation method of a closed-pore hard carbon material, which is similar to example 2, and the difference is that in S100, the impregnation pressure is replaced by 12MPa, and the impregnation temperature is replaced by 160℃. The remaining conditions are the same as those in example 2, and details are not described herein again.

[0068] Comparative Example 1

[0069] The comparative example provides a preparation method of a hard carbon material, which is similar to example 1, and the difference is that in S100, the fluorine and nitrogen-containing organic matter (perfluoropyridine amine) is replaced by toluene with equal mass. The remaining conditions are the same as those in example 1, and details are not described herein again.

[0070] The hard carbon material prepared in the comparative example is subjected to transmission electron microscope test, and the result is shown in the figure. Figure 3 As shown in the figure, the closed-pore hard carbon material prepared in the comparative example has a small number of closed pores and a small closed pore volume.

[0071] Comparative Example 2

[0072] The present comparative example provides a preparation method of a hard carbon material, which is similar to Example 1, except that in S100, the fluorine-containing nitrogen organic matter (perfluoropyridine amine) is omitted. The remaining conditions are the same as those in Example 1, and will not be repeated here.

[0073] Comparative Example 3

[0074] The present comparative example provides a preparation method of a hard carbon material, which is similar to Example 1, except that in S100, the impregnation pressure is replaced by 5 MPa. The remaining conditions are the same as those in Example 1, and will not be repeated here.

[0075] Comparative Example 4

[0076] The present comparative example provides a preparation method of a hard carbon material, which is similar to Example 2, except that in S200, the microwave heating is replaced by resistance wire heating, and the hard carbon precursor is heated to 1300℃ within 1 min. The remaining conditions are the same as those in Example 2, and will not be repeated here.

[0077] The hard carbon material prepared in the present comparative example was subjected to transmission electron microscope test, and the results are shown in FIG. 2. Figure 4 As can be seen from the figure, the closed pore hard carbon material prepared in the present comparative example has a smaller number of closed pores and a smaller closed pore volume.

[0078] Comparative Example 5

[0079] The present comparative example provides a preparation method of a hard carbon material, which is similar to Example 2, except that in S200, the reaction temperature is replaced by 1600℃, and the remaining conditions are the same as those in Example 2, and will not be repeated here.

[0080] Application Example

[0081] The present application example provides a sodium ion half-cell respectively prepared from the hard carbon materials of Examples 1-7 and Comparative Examples 1-5, and the preparation method thereof comprises the following steps:

[0082] S100, the hard carbon material, acetylene black and sodium alginate are ground in a mass ratio of 8:1:1, and water is added and mixed uniformly to obtain a mixed slurry with a solid content of 85%.

[0083] S200, the mixed slurry is coated on the surface of a copper foil, and the coating amount is 2.5 g / cm 2 After vacuum drying at 80℃ for 12 h, the obtained coated material is cut into small round pieces with a diameter of 12 mm to obtain negative electrode pieces.

[0084] S300, the negative electrode sheet is assembled into a battery, the sodium metal sheet is used as a counter electrode, the diaphragm is glass fiber, and the electrolyte is a mixed solution of EC and DEC containing 1 mol / L NaPF6 (the volume ratio of EC to DEC is 1:1), to obtain a sodium ion half battery.

[0085] Verification test

[0086] The closed pore volume of the hard carbon material of Examples 1-7 and Comparative Examples 1-5 is tested, and the test results are shown in Table 1. First, the true density of each hard carbon material is tested to obtain the true density value p ture ; then the closed pore volume is calculated according to the formula V = 1 / p ture -1 / 2.26, wherein 2.26 is the true density value of graphite.

[0087] The sodium ion half battery prepared in the application example is placed on a Land CT2001A battery test system, and electrochemical performance test is performed, and the test results are shown in Table 1. The test temperature is 25°C, the test electrochemical window is 0V-2.5V, and the test current density is 30mA / g.

[0088] Table 1: Performance test results of hard carbon materials of examples and comparative examples

[0089]

[0090] As can be seen from the table, compared with the examples, Comparative Example 1 uses toluene as a pore filling agent, toluene cannot generate C-F or C-N functional groups at high temperatures, cannot combine with sodium ions to form inorganic substances such as NaF and Na3N, and cannot promote the directional decomposition of PF6 - ; Comparative Example 2 does not add a pore filling agent, and the prepared hard carbon material has an open pore structure, less closed pore structure, and a narrow interlayer distance.

[0091] Compared with the examples, the impregnation pressure of Comparative Example 3 is too low, and the pore filling agent cannot fully enter the internal pores of the activated carbon, resulting in that the pore filling agent cannot effectively block the open pores after carbonization, and the closed pore structure is less.

[0092] Compared with the examples, Comparative Example 4 replaces the microwave rapid heating method with resistance wire heating, the heating speed is slow, the internal heat of the hard carbon precursor is transferred to the surface for a long time, causing excessive decomposition and carbonization of the pore filling agent, resulting in that the closed pore structure is blocked by graphite domains, and a large amount of C-F and C-N functional groups escape, the content of C-F and C-N functional groups in the hard carbon material is too low, and the SEI layer dominated by inorganic substances cannot be formed, thereby adversely affecting the platform capacity, initial efficiency and other properties of the hard carbon material.

[0093] Compared with the embodiments, the temperature of the reaction (carbonization) in S200 of Comparative Example 5 is too high, which also causes excessive carbonization of the pore-filling agent, resulting in the closed pore structure being blocked by graphite domains; in addition, the excessive temperature causes excessive carbonization of the activated carbon, resulting in a narrow interlayer distance, which is not conducive to the sodium ions passing through the interlayer to reach the inside of the closed pore structure.

[0094] Compared with Examples 1-5, the amount of fluorine-containing nitrogen organic matter used in Example 6 is too much, which causes excessive plugging of the pores of the activated carbon; the impregnation pressure and temperature of Example 7 are too high, which causes the activated carbon to adsorb excessive amounts of fluorine and nitrogen pore-filling organic matter, which also causes excessive plugging of the pores. In the subsequent (carbonization) reaction, the excessive pore-filling agent forms curved graphite domains on the outside of the pores of the activated carbon, resulting in some of the closed pore structures being blocked, and also causing the interlayer distance to narrow.

[0095] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements or improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a closed-cell hard carbon material, characterized in that, Includes the following steps: S100. Fluorine-nitrogen-containing organic matter and porous carbon matrix are added to solvent, mixed evenly, and impregnated at 130℃~150℃ and 7MPa~10MPa for 3h~5h to obtain hard carbon precursor. The fluorinated nitrogen organic compound includes at least one of tetrafluoropyridine or trifluoromethylpyrrole, wherein the trifluoromethylpyrrole includes at least one of 2-(trifluoromethyl)pyrrole or 3-(trifluoromethyl)pyrrole; the mass-volume ratio of the fluorinated nitrogen organic compound, the porous carbon matrix and the solvent is (2~4)g:(3~5)g:(40~60)mL. S200. Under an inert atmosphere, the hard carbon precursor is heated to 1300℃~1500℃ within 5s~15s using microwave heating, and after reacting for 2h~4h, closed-cell hard carbon material is obtained.

2. The method for preparing closed-cell hard carbon material as described in claim 1, characterized in that, In S100, the porous carbon matrix includes activated carbon; In S100, the solvent comprises anhydrous ethanol and water in a volume ratio of (1~1.5):

1.

3. The method for preparing closed-cell hard carbon material as described in claim 2, characterized in that, In S100, the activated carbon has an average pore size of 1 nm to 2 nm and a specific surface area of ​​1500 m². 2 / g~1700m 2 / g.

4. A closed-cell hard carbon material, characterized in that, It is prepared by the method for preparing closed-cell hard carbon material according to any one of claims 1 to 3.

5. A negative electrode material, characterized in that, Includes the closed-cell hard carbon material as described in claim 4.

6. The application of the negative electrode material according to claim 5 in a sodium-ion battery.

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