Polymer-based hard carbon negative electrode material, preparation method and application

Abstract

The application discloses a polymer-based hard carbon negative electrode material, a preparation method and application thereof, and the preparation method comprises the following steps: (1) preparing an aqueous solution and an oil solution, wherein the aqueous solution comprises water, polyvinylpyrrolidone and a cationic surfactant, and the oil solution comprises a pore-forming agent, a free radical initiator and a divinylbenzene monomer; (2) mixing the aqueous solution and the oil solution uniformly under ultrasonic condition to form an emulsion; (3) transferring the emulsion to a nitrogen atmosphere, heating the emulsion, cooling to room temperature after the reaction is completed, collecting a solid product through solid-liquid separation, and drying after washing; and (4) heating the solid product in a nitrogen atmosphere, and constant-temperature carbonization to obtain the polymer-based hard carbon negative electrode material. The polymer-based hard carbon negative electrode material has the potential to be widely applied in the field of energy storage and energy storage systems such as sodium ion batteries, and can significantly improve the charge-discharge capacity of the sodium ion battery through the rich closed pore design.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion batteries, and particularly relates to a polymer-based hard carbon negative electrode material, a preparation method and application. BACKGROUND

[0002] In recent years, lithium ion batteries are widely used in society, and as a homologous element, sodium ions have attracted widespread attention from researchers due to their abundant resources and similar physicochemical properties to lithium ions. However, as a commonly used negative electrode material of lithium ion batteries, graphite material is difficult to form a stable intercalation compound with sodium ions due to thermodynamic reasons, so it is difficult for sodium ion batteries to use graphite as a negative electrode material.

[0003] Researchers have found that hard carbon material can become the most promising negative electrode material for sodium ion batteries due to its low discharge platform, high charge and discharge capacity and excellent cycle stability. Although the hard carbon negative electrode material has many application potentials, its low first coulomb efficiency and low voltage platform (<0.1V) capacity limit its commercial application.

[0004] In sodium ion batteries, the charge and discharge curve of hard carbon usually shows a high potential slope area (>0.1V) and a low potential plateau area (<0.1V). Although the storage mechanism of sodium is not clear, a large number of studies have shown that closed pores are the main reason for sodium storage on the low voltage plateau. So far, many studies have been devoted to increasing the number and size of closed nanopores to maximize the platform capacity of the obtained hard carbon. For example, CN118387859A - Preparation method of a high closed pore capacity hard carbon negative electrode material and sodium ion battery, which is a method of reacting a first carbon source containing multivalent metal ions with a second carbon source to obtain an aerogel precursor, and then pyrolyzing and steam blasting the aerogel precursor to obtain a porous pyrolytic carbon material containing multivalent metal oxides, and then acid washing and heat treating the porous pyrolytic carbon material to finally obtain the high closed pore capacity hard carbon negative electrode material. However, the above scheme is relatively complex, and there is still a lack of simple and effective closed pore construction strategy, which seriously hinders the development of high platform capacity hard carbon negative electrode materials. Therefore, how to develop a low-cost, simple process and high platform capacity hard carbon negative electrode material is a problem to be solved by the present application. SUMMARY

[0005] To solve the above technical problems, the purpose of the present application is to provide a polymer-based hard carbon negative electrode material, a preparation method and application, which can significantly improve the charge and discharge capacity of sodium ion batteries through rich closed pore design. The polymer-based hard carbon negative electrode material has the potential to be widely used in energy storage fields and energy storage systems such as sodium ion batteries.

[0006] To achieve the above application purposes, the technical solutions adopted by the present application are as follows:

[0007] In the first aspect of the present application, the present application provides a preparation method of a polymer-based hard carbon negative electrode material, which comprises the following steps:

[0008] (1) preparing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution comprises water, polyvinylpyrrolidone and a cationic surfactant dissolved in water, and the oil phase solution comprises an organic solvent, a pore-forming agent, a free radical initiator and a divinylbenzene monomer dissolved in the organic solvent;

[0009] (2) mixing the aqueous phase solution and the oil phase solution under ultrasonic conditions to form an emulsion;

[0010] (3) transferring the emulsion to a nitrogen atmosphere, heating the emulsion to 55-95°C, continuously stirring for 4-12h, cooling to room temperature after the reaction is completed, collecting the solid product by solid-liquid separation, and drying the solid product after washing with ethanol and deionized water;

[0011] (4) heating the solid product in a nitrogen atmosphere, heating the solid product to 500-1700°C at a rate of 1-10°C / min, and then carbonizing the solid product at a constant temperature for 1-8h to obtain a polymer-based hard carbon negative electrode material.

[0012] Preferably, in the aqueous phase solution, the mass ratio of water, polyvinylpyrrolidone and the cationic surfactant is (25-75):(0.05-0.1):(0.02-0.04).

[0013] Preferably, in the oil phase solution, the mass ratio of the pore-forming agent, the free radical initiator and the divinylbenzene monomer is (30-50):(0.2-0.5):(5-15).

[0014] Preferably, in step (2), the aqueous phase solution is added dropwise into the oil phase solution under ultrasonic conditions to form the emulsion.

[0015] Preferably, in step (1), the cationic surfactant comprises one or more of ammonium lauryl sulfate, cetyltrimethylammonium bromide, cetyl dimethyl ammonium chloride, benzalkonium bromide and polyethyleneimine.

[0016] Preferably, in step (1), the pore-forming agent comprises one or more of polyvinyl alcohol, a toluene-n-heptane mixed solution, azodicarbonamide, ammonium chloride and polyvinyl chloride.

[0017] More preferably, the pore-forming agent is a toluene-n-heptane mixed solution formed by mixing toluene and n-heptane at a volume ratio of 2:1.

[0018] Preferably, in step (1), the free radical initiator comprises one or more of cyclohexanone peroxide, azobisisobutyronitrile, ammonium persulfate, dibenzoyl peroxide and azobisisoheptane nitrile.

[0019] In the second aspect of the present application, the present application provides a polymer-based hard carbon negative material prepared by the above preparation method.

[0020] In the third aspect of the present application, the present application provides an application of the polymer-based hard carbon negative material, the polymer-based hard carbon negative material prepared above is applied to a sodium ion battery to prepare a negative electrode of the sodium ion battery.

[0021] Beneficial effects:

[0022] The present application can significantly improve the charge and discharge capacity of the sodium ion battery through the rich closed pore design, and obtain a higher first coulomb efficiency without any coating and granulation treatment. The polymer-based hard carbon negative material prepared by the present application has potential and can be widely applied in the field of energy storage and energy storage systems such as sodium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The SEM diagram of the sodium ion battery negative material obtained by the present application is shown.

[0024] Figure 2 The HRTEM diagram of the sodium ion battery negative material obtained by the present application is shown.

[0025] Figure 3 The first cycle charge and discharge curve of the sodium ion battery negative material obtained by the present application under a current density of 0.05 A / g is shown.

[0026] Figure 4 The second to fifth cycle charge and discharge curves of the sodium ion battery negative material obtained by the present application under a current density of 0.05 A / g are shown.

[0027] Figure 5 The first cycle charge and discharge curves of each embodiment of the sodium ion battery negative material obtained by the present application and the comparative example 1 are shown. DETAILED DESCRIPTION

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the specific embodiments of the present application will be described below with reference to the drawings. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor, and other embodiments can also be obtained.

[0029] The present application provides a preparation method of a polymer-based hard carbon negative material, which uses a pre-emulsified micro-suspension polymerization method to prepare the hard carbon negative material, and the specific process is as follows:

[0030] (1) preparing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution comprises water, polyvinyl pyrrolidone soluble in water, and a cationic surfactant, and the oil phase solution comprises a pore former, a free radical initiator, and a divinylbenzene monomer;

[0031] (2) Under ultrasonic conditions, the aqueous phase solution and the oil phase solution are mixed uniformly to form an emulsion. Preferably, the aqueous phase solution is added dropwise to the oil phase solution to form an emulsion.

[0032] (3) transferring the emulsion to a nitrogen atmosphere, heating the emulsion to 55-95°C, and continuously stirring for 4-12 hours. After the reaction is completed, cooling the emulsion to room temperature, collecting the solid product by solid-liquid separation, washing the solid product with ethanol and deionized water, and then drying;

[0033] (4) heating the solid product in a nitrogen atmosphere to 500-1700° C. at a rate of 1-10° C. / min, and then carbonizing the solid product at a constant temperature for 1-8 hours to obtain a polymer-based hard carbon negative electrode material.

[0034] In step (1), the cationic surfactant includes one or more of lauryl ammonium sulfate, cetyltrimethylammonium bromide, cetyldimethylammonium chloride, benzalkonium bromide and polyethyleneimine.

[0035] In step (1), the pore-forming agent includes one or more of polyvinyl alcohol, a toluene-n-heptane mixed solution, azodicarbonamide, ammonium chloride, and polyvinyl chloride. Preferably, the pore-forming agent is a toluene-n-heptane mixed solution formed by mixing toluene and n-heptane in a volume ratio of 2:1. The toluene-n-heptane solution is a good solvent for divinylbenzene monomer, but polydivinylbenzene chains are insoluble therein. After the polymerization reaction, extrusion of the toluene-n-heptane solution in the polymer is more conducive to forming a porous structure.

[0036] In step (1), the free radical initiator includes one or more of cyclohexanone peroxide, azobisisobutyronitrile, ammonium persulfate, dibenzoyl peroxide and azobisisoheptylonitrile.

[0037] The present invention uses only a pore-forming agent to prepare a polymer-based hard carbon material precursor with abundant pores (i.e., the solid product in step (3)). After subsequent high-temperature carbonization, a rich closed-pore structure is formed, providing additional storage sites for sodium ion storage. This significantly increases the platform capacity at low potentials (<0.1V), reaching a platform capacity of 244.2 mAh / g. The polymer-based hard carbon anode material prepared by the present invention exhibits excellent sodium storage performance. The anode material prepared from the anode material is applied to sodium-ion batteries, achieving an initial discharge specific capacity of 466.4 mAh / g and an initial coulombic efficiency of 73.7%.

[0038] The synthesis process of the polymer-based hard carbon negative electrode material does not involve other auxiliary materials such as metals, has relatively low overall preparation cost, and has the advantages of simple operation and high repeatability, and is convenient for large-scale production.

[0039] To sum up, the sodium ion battery charge and discharge capacity can be significantly improved by the rich closed pore design, and the high initial coulomb efficiency can be obtained without any coating and granulation treatment. The negative electrode material has the potential to be widely used in the field of energy storage and energy storage systems such as sodium ion batteries, because it provides a synthesis method of polymer-based hard carbon negative electrode material with high charge and discharge capacity and high initial coulomb efficiency.

[0040] The technical solutions of the present application will be described in detail below with specific examples.

[0041] Example 1

[0042] 75mg polyvinylpyrrolidone, 33mg cetyltrimethylammonium bromide were dissolved in 50ml deionized water to prepare an aqueous phase solution.

[0043] 12.5ml n-heptane and 25ml toluene were used as pore forming agents, 0.32g azobisisobutyronitrile was used as a free radical initiator, and 10ml divinylbenzene monomer was mixed to prepare an oil phase solution.

[0044] Under the condition of ultrasonic, the aqueous phase was added dropwise into the oil phase to make it uniformly dispersed to form an emulsion, and then the emulsion was transferred into a three-necked flask with nitrogen protection, heated at 75℃ for 6h, after the reaction was completed, cooled to room temperature.

[0045] The cooled product was filtered, and the solid product was collected, and the collected solid product was washed with ethanol and deionized water repeatedly, and the washed solid product was dried in a vacuum drying oven at 80℃ for 12h; the dried solid product was heated to 1500℃ at a heating rate of 5℃ / min in a tube furnace, and carbonized at 1500℃ for 2h to obtain a polymer-based hard carbon negative electrode material (HC-1500).

[0046] The polymer-based hard carbon negative electrode material, conductive agent acetylene black and binder PVDF were mixed uniformly at a mass ratio of 7:2:1, and N-methyl pyrrolidone was added to prepare a negative electrode slurry, which was coated on an aluminum foil and dried in a 60°C drying oven for 12 h. The above-prepared material was used as a negative electrode sheet, a separator was a polyethylene-polypropylene-polyethylene three-layer film, and an electrolyte was 1M NaPF6 in diglyme (DIGLYME). A CR2025 button cell was assembled in an argon-filled glove box (water and oxygen were both <0.1 ppm). The charge-discharge test was performed on a new Wei CT-4008 (Shenzhen Xinnwei Electronics Co., Ltd.) to measure the constant current charge-discharge, and the charge-discharge voltage range was 0.01-3V.

[0047] Figure 1 The scanning electron microscope (SEM) image of the material HC-1500 prepared in the application shows that the prepared material has a lamellar structure.

[0048] Figure 2 The high-resolution transmission electron microscopy (HRTEM) image of the material HC-1500 shows that HC-1500 has a high degree of graphitization, which provides more sodium storage sites.

[0049] Figure 3 The first cycle charge-discharge curve of the polymer-based hard carbon negative electrode material HC-1500 as a sodium ion battery negative electrode material, with a charge-discharge voltage range of 0.01-3V and a current density of 0.05A / g. As can be seen from the figure, the first discharge / charge specific capacity is 466.4 / 343.9mAh / g, and the initial coulombic efficiency is 73.7%. The low voltage (<0.1V) platform capacity is 244.2mAh / g.

[0050] Figure 4 The second to fifth cycle charge-discharge curves of the polymer-based hard carbon negative electrode material HC-1500 as a sodium ion battery negative electrode material, with a charge-discharge voltage range of 0.01-3V and a current density of 0.05A / g. As can be seen from the figure, the second to fifth cycle GCD curves can be well overlapped, and the sodium ion battery negative electrode material HC-1500 has good reversibility.

[0051] Figure 5 The first cycle charge-discharge curve of the polymer-based hard carbon negative electrode material HC-1500 as a sodium ion battery negative electrode material, with a charge-discharge voltage range of 0.01-3V and a current density of 0.05A / g. As can be seen from the figure, HC-1500 has a higher low voltage platform capacity (244.2mAh / g) and the highest initial coulombic efficiency (73.7%).

[0052] Example 2

[0053] The carbonization temperature in Example 2 was changed to 700°C for 2h, and a polymer-based hard carbon negative electrode material HC-700 was obtained.

[0054] The polymer-based hard carbon negative electrode material, conductive agent acetylene black and binder PVDF were mixed in a mass ratio of 7:2:1, and N-methyl pyrrolidone was added to prepare a negative electrode slurry, which was coated on an aluminum foil and dried in a 60°C drying oven for 12h. The above-prepared material was used as a negative electrode sheet, a separator was a polyethylene-polypropylene-polyethylene three-layer film, and an electrolyte was 1M NaPF6 in diglyme (DIGLYME). CR2025 button cells were assembled in an argon-filled glove box (water and oxygen were both <0.1ppm). The charge-discharge test was a constant current charge-discharge measurement on a new CT-4008 (Shenzhen New Wei Electronics Co., Ltd.), and the charge-discharge voltage range was 0.01-3V.

[0055] The measured polymer-based hard carbon negative electrode material HC-700 had a discharge / charge specific capacity of 446.2 / 245.7mAh / g at the first cycle at a current density of 0.05A / g, and the first coulombic efficiency was 55.1%. The low voltage (<0.1V) platform capacity was 96.1mAh / g.

[0056] Example 3

[0057] The carbonization temperature in Example 3 was changed to 900°C for 2h, and a polymer-based hard carbon negative electrode material HC-900 was obtained.

[0058] The polymer-based hard carbon negative electrode material, conductive agent acetylene black and binder PVDF were mixed in a mass ratio of 7:2:1, and N-methyl pyrrolidone was added to prepare a negative electrode slurry, which was coated on an aluminum foil and dried in a 60°C drying oven for 12h. The above-prepared material was used as a negative electrode sheet, a separator was a polyethylene-polypropylene-polyethylene three-layer film, and an electrolyte was 1M NaPF6 in diglyme (DIGLYME). CR2025 button cells were assembled in an argon-filled glove box (water and oxygen were both <0.1ppm). The charge-discharge test was a constant current charge-discharge measurement on a new CT-4008 (Shenzhen New Wei Electronics Co., Ltd.), and the charge-discharge voltage range was 0.01-3V.

[0059] The measured polymer-based hard carbon negative electrode material HC-900 had a discharge / charge specific capacity of 440.6 / 274.7mAh / g at the first cycle at a current density of 0.05A / g, and the first coulombic efficiency was 62.4%. The low voltage (<0.1V) platform capacity was 140.0mAh / g.

[0060] Example 4

[0061] The carbonization temperature in Example 4 was changed to 1100°C for 2h, and a polymer-based hard carbon negative electrode material HC-1100 was obtained based on the other conditions in Example 1.

[0062] The polymer-based hard carbon negative electrode material, conductive agent acetylene black and binder PVDF were mixed uniformly at a mass ratio of 7:2:1, and N-methyl pyrrolidone was added to prepare a negative electrode slurry, which was coated on an aluminum foil and dried in a 60°C drying oven for 12h. The above-prepared material was used as a negative electrode sheet, a separator was a polyethylene-polypropylene-polyethylene three-layer film, and an electrolyte was 1M NaPF6 in diglyme (DIGLYME), and a CR2025 button cell was assembled in an argon-filled glove box (water and oxygen were both <0.1ppm). The charge-discharge test was a constant current charge-discharge measurement on a Xunwei CT-4008 (Shenzhen Xunwei Electronics Co., Ltd.), and the charge-discharge voltage range was 0.01-3V.

[0063] The measured hard carbon negative electrode material HC-1100 had a discharge / charge specific capacity of 391.8 / 246.1mAh / g at the first cycle at a current density of 0.05A / g, and a first coulombic efficiency of 62.8%. The low voltage (<0.1V) platform capacity was 118.5mAh / g.

[0064] Example 5

[0065] The carbonization temperature in Example 5 was changed to 1300°C for 2h, and a polymer-based hard carbon negative electrode material HC-1300 was obtained based on the other conditions in Example 1.

[0066] The polymer-based hard carbon negative electrode material, conductive agent acetylene black and binder PVDF were mixed uniformly at a mass ratio of 7:2:1, and N-methyl pyrrolidone was added to prepare a negative electrode slurry, which was coated on an aluminum foil and dried in a 60°C drying oven for 12h. The above-prepared material was used as a negative electrode sheet, a separator was a polyethylene-polypropylene-polyethylene three-layer film, and an electrolyte was 1M NaPF6 in diglyme (DIGLYME), and a CR2025 button cell was assembled in an argon-filled glove box (water and oxygen were both <0.1ppm). The charge-discharge test was a constant current charge-discharge measurement on a Xunwei CT-4008 (Shenzhen Xunwei Electronics Co., Ltd.), and the charge-discharge voltage range was 0.01-3V.

[0067] The measured hard carbon negative electrode material HC-1300 had a discharge / charge specific capacity of 446.0 / 300.6mAh / g at the first cycle at a current density of 0.05A / g, and a first coulombic efficiency of 67.4%. The low voltage (<0.1V) platform capacity was 190.1mAh / g.

[0068] Example 6

[0069] On the basis of Example 1, other conditions remain unchanged, the oil phase solution and aqueous solution in Example 6 are mixed directly, and other conditions remain unchanged, carbonization at a temperature of 1500℃ for 2h, to obtain a polymer-based hard carbon negative electrode material HC-1500-1.

[0070] The polymer-based hard carbon negative electrode material, conductive agent acetylene black and binder PVDF are mixed uniformly at a mass ratio of 7:2:1, and N-methyl pyrrolidone is added to prepare a negative electrode slurry, which is coated on an aluminum foil and dried in a 60℃ drying oven for 12h. The above-prepared material is used as a negative electrode sheet, the separator is a polyethylene-polypropylene-polyethylene three-layer film, and the electrolyte is 1M NaPF6 in diglyme (DIGLYME), which is assembled into a CR2025 button cell in an argon-filled glove box (water and oxygen are both <0.1ppm). The charge-discharge test is a constant current charge-discharge measurement on a new CT-4008 (Shenzhen New Wei Electronics Co., Ltd.), and the charge-discharge voltage range is 0.01-3V.

[0071] The measured hard carbon negative electrode material HC-1500-1 has a discharge / charge specific capacity of 461.3 / 337.8mAh / g at the first cycle at a current density of 0.05A / g, and a first coulombic efficiency of 73.2%. The low voltage (<0.1V) platform capacity is 235.5mAh / g.

[0072] It can be seen that, compared with HC-1500 in Example 1, the mixing of the oil phase and aqueous solution has little effect on the electrochemical data of the HC-1500-1 material.

[0073] Example 7

[0074] On the basis of Example 1, other conditions remain unchanged, the carbonization temperature in Example 5 is changed to 1700℃ for 2h, to obtain a polymer-based hard carbon negative electrode material HC-1700.

[0075] The polymer-based hard carbon negative electrode material, conductive agent acetylene black and binder PVDF are mixed uniformly at a mass ratio of 7:2:1, and N-methyl pyrrolidone is added to prepare a negative electrode slurry, which is coated on an aluminum foil and dried in a 60℃ drying oven for 12h. The above-prepared material is used as a negative electrode sheet, the separator is a polyethylene-polypropylene-polyethylene three-layer film, and the electrolyte is 1M NaPF6 in diglyme (DIGLYME), which is assembled into a CR2025 button cell in an argon-filled glove box (water and oxygen are both <0.1ppm). The charge-discharge test is a constant current charge-discharge measurement on a new CT-4008 (Shenzhen New Wei Electronics Co., Ltd.), and the charge-discharge voltage range is 0.01-3V.

[0076] The measured hard carbon negative material HC-1700, the discharge / charge specific capacity of the first circle at 0.05 A / g current density is 430.3 / 300.2 mAh / g respectively, the first coulombic efficiency is 69.7%. The low voltage (<0.1 V) platform capacity is 190.6 mAh / g.

[0077] This shows that HC-1700 has less low voltage capacity compared with HC-1500 when the carbonization temperature rises to 1700℃, which indicates that the number of closed pores is relatively reduced at the temperature of 1700℃. It shows the influence of temperature on the closed pores in the hard carbon material.

[0078] The above has carried out the detailed elaboration to the example provided by the application. The principle and implementation mode of the application are described by applying specific examples in this paper, and the above example is only used to help understanding the core idea of the application. It should be pointed out that for ordinary skilled in the art, without departing from the principle of the application, the application can be improved and modified, and these improvements and modifications also fall within the protection scope of the claims of the application.

Claims

1. A method for preparing a polymer-based hard carbon negative electrode material, characterized in that: include: (1) preparing an aqueous phase solution and an oil phase solution, wherein the aqueous phase solution includes water and polyvinyl pyrrolidone and a cationic surfactant dissolved in water, and the oil phase solution includes a pore former, a free radical initiator, and a divinylbenzene monomer, wherein the pore former includes a mixed solution of toluene and n-heptane, and the free radical initiator includes one or more of cyclohexanone peroxide, azobisisobutyronitrile, ammonium persulfate, dibenzoyl peroxide, and azobisisoheptanenitrile; (2) Under ultrasonic conditions, the aqueous phase solution and the oil phase solution are mixed to form an emulsion; (3) transferring the emulsion to a nitrogen atmosphere, heating the emulsion to 55-95°C, and continuously stirring for 4-12 hours. After the reaction is completed, cooling the emulsion to room temperature, collecting the solid product by solid-liquid separation, washing the solid product with ethanol and deionized water, and then drying; (4) heating the solid product in a nitrogen atmosphere to 500-1700° C. at a rate of 1-10° C. / min, and then carbonizing the solid product at a constant temperature for 1-8 hours to obtain a polymer-based hard carbon negative electrode material.

2. The preparation method according to claim 1, characterized in that In the aqueous phase solution, the mass ratio of water, polyvinyl pyrrolidone and cationic surfactant is (25-75):(0.05-0.1):(0.02-0.04).

3. The preparation method according to claim 1, characterized in that In the oil phase solution, the mass ratio of the pore former, the free radical initiator and the divinylbenzene monomer is (30-50):(0.2-0.5):(5-15).

4. The preparation method according to claim 1, characterized in that In step (2), the aqueous phase solution is added dropwise to the oil phase solution under ultrasonic conditions to form an emulsion.

5. The preparation method according to claim 1, characterized in that In step (1), the cationic surfactant includes one or more of lauryl ammonium sulfate, cetyltrimethylammonium bromide, cetyldimethylammonium chloride, benzalkonium bromide and polyethyleneimine.

6. The preparation method according to claim 1, characterized in that The pore-forming agent is a toluene-n-heptane mixed solution formed by mixing toluene and n-heptane in a volume ratio of 2:

1.

7. A polymer-based hard carbon negative electrode material, characterized in that: The hard carbon anode material is prepared by the method for preparing the polymer-based hard carbon anode material according to any one of claims 1 to 6.

8. An application of a polymer-based hard carbon negative electrode material, characterized in that: The polymer-based hard carbon negative electrode material prepared by the preparation method according to any one of claims 1 to 6 is applied to sodium ion batteries.

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