Sodium-ion battery hard carbon negative electrode material and preparation method thereof

Abstract

The invention discloses a sodium ion battery hard carbon negative electrode material and a preparation method thereof. Relates to the field of sodium-ion battery materials. The preparation method comprises the following steps: firstly, mechanically crushing a semi-coke block, carrying out acid pickling, then, carrying out pre-oxidation in an air atmosphere to obtain a pre-oxidation product, putting the pre-oxidation product and crushed asphalt powder into a VC (Vitamin C) mixer, carrying out mixing, putting a mixed hard carbon precursor into an inert gas atmosphere, carrying out high-temperature carbonization, and then, carrying out cooling, so as to prepare the hard carbon negative electrode material. According to the hard carbon negative electrode material provided by the invention, the surface of the semi-coke is coated with a layer of asphalt through a solid-phase mixing and coating method, so that part of open pores of the semi-coke can be closed, a large number of closed pores are formed, the pore structure is improved, active sites, in contact with electrolyte, of the surface of the material are reduced, and the first-week coulombic efficiency is improved; the problem that an existing negative electrode carbon material for the sodium-ion battery cannot be compatible in the aspects of hard carbon yield, reversible capacity, first-week coulombic efficiency and the like is solved.

Description

Technical Field

[0001] The present invention relates to the field of sodium ion battery materials, and in particular to a sodium ion battery hard carbon negative electrode material and a preparation method thereof. Background Art

[0002] As society continues to progress, the new energy industry is also rapidly developing. The scarcity of lithium resources has led to the risk of increasing costs for mainstream lithium-ion batteries. Therefore, developing more cost-effective applications is more conducive to the development of the new energy industry. Sodium-ion batteries, due to their abundant resources, widespread distribution, and low cost, are the most likely energy storage applications to replace lithium-ion batteries in the future.

[0003] Anode materials are a key factor in determining the performance of sodium-ion batteries. Graphite is a commonly used anode material in lithium-ion batteries. However, because the atomic radius of sodium is larger than that of lithium, graphite anodes cannot be used in sodium-ion batteries due to the small interlayer spacing, making sodium insertion impossible. Currently, hard carbon is widely considered the most mainstream choice for sodium-ion battery anodes. Precursor materials used for hard carbon include biomass, resin, asphalt, and anthracite. However, the carbonization yield of biomass-based hard carbon is relatively low, the synthesis process of resin-based hard carbon is too expensive, and asphalt and anthracite-based hard carbons suffer from low capacity. Therefore, the use of these precursors to prepare sodium-ion battery hard carbon anode materials cannot achieve a balance in terms of yield, cost, and capacity. Therefore, there is an urgent need to find new anode material precursors. Semi-coke, also known as semi-coke, is a product obtained by pyrolyzing coal at 600-700°C. The large amount of fine particulate matter generated during its production and transportation causes resource waste and environmental pollution. However, lignite has the characteristics of high fixed carbon content, low ash content, low volatile matter, etc., and has advantages in the preparation of hard carbon for sodium ion batteries.

[0004] Chinese patent CN115124021 A discloses a method for preparing hard carbon materials of a semi-carbon system modified by a nitrogen-oxygen dual-doping process, which solves the problem that the current preparation process of semi-carbon-based hard carbon materials and the electrochemical properties of the prepared carbon materials need to be further optimized. However, the hard carbon negative electrode material obtained by this method has low reversible capacity and first coulombic efficiency. Therefore, how to find a suitable method to improve the reversible capacity and first coulombic efficiency of the semi-carbon system hard carbon negative electrode is a challenge facing the current work. Summary of the Invention

[0005] The purpose of the present invention is to provide a sodium ion battery hard carbon negative electrode material and a preparation method thereof, so as to solve the problems of low reversible capacity and poor first coulombic efficiency of the blue charcoal system hard carbon negative electrode.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0008] S1. The semi-coke block is crushed and then subjected to acid washing and deashing treatment, then washed with water until neutral, and dried to obtain semi-coke powder;

[0009] S2. The blue carbon powder is pre-oxidized and calcined to obtain a pre-oxidized product;

[0010] S3. Adding the crushed asphalt to the pre-oxidation product and mixing uniformly to obtain a hard carbon precursor;

[0011] S4. Carbonizing the hard carbon precursor in an inert atmosphere to obtain a hard carbon negative electrode material.

[0012] As a further solution of the present invention, in S1, the particle size d of the semi-coke block after crushing is 50 3-10μm.

[0013] As a further solution of the present invention, in S1, the pickling liquid in the pickling and deashing process is hydrochloric acid, hydrofluoric acid or a combination of the two.

[0014] As a further solution of the present invention, in S2, the temperature of the pre-oxidation calcination is 300-500°C and the time is 3-5 hours.

[0015] As a further solution of the present invention, in S3, the asphalt is any one of petroleum asphalt, coal asphalt, and natural asphalt, or a combination of several of them.

[0016] As a further embodiment of the present invention, in S3, the particle size d of the crushed asphalt is 50 3±1μm.

[0017] As a further embodiment of the present invention, in S3, the mass ratio of the pre-oxidation product to the asphalt is (2-4):1.

[0018] As a further embodiment of the present invention, in S4, the inert atmosphere is nitrogen.

[0019] As a further solution of the present invention, in S4, the carbonization treatment temperature is 1100-1500° C. and the time is 2-4 hours.

[0020] A hard carbon negative electrode material for a sodium ion battery is prepared by the above-mentioned preparation method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a hard carbon negative electrode material for sodium ion batteries and a preparation method thereof. First, the semi-coke block is mechanically crushed, and after acid washing, it is pre-oxidized in an air atmosphere to obtain a pre-oxidation product. The pre-oxidation product and the crushed asphalt powder are placed in a VC mixer for mixing. The mixed hard carbon precursor is placed in an inert gas atmosphere for high-temperature carbonization, and then cooled to obtain a hard carbon negative electrode material. The hard carbon negative electrode material provided by the present invention is coated with a layer of asphalt on the surface of the semi-coke by a solid-phase mixed coating method, which can close part of the open pores of the semi-coke, forming a large number of closed pores, improving the pore structure, reducing the active sites on the surface of the material in contact with the electrolyte, and improving the first-week coulomb efficiency, solving the problem that the existing negative electrode carbon materials for sodium ion batteries cannot achieve both hard carbon yield, reversible capacity and first-week coulomb efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the first charge and discharge of the hard carbon negative electrode material prepared in Example 1 of the present invention when used in a battery. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0025] The terms used in the examples of this application are for the purpose of describing specific implementation rules only and are not intended to limit this application. The singular forms "a", "an", "the" and "the" used in the implementation rules of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0026] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0027] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0028] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0030] The present application provides a method for preparing a hard carbon negative electrode material for a sodium ion battery, which specifically includes the following steps:

[0031] S1. The semi-coke block is crushed into a certain size using a mechanical crusher to obtain small-sized pulverized semi-coke, deashed by acid washing, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0032] S2. The blue carbon powder is placed in a tube furnace and pre-oxidized and calcined in an air atmosphere. After the calcination is completed, it is cooled to room temperature (25-30 ° C) to obtain a pre-oxidized product;

[0033] S3 the asphalt is crushed, and then the pre-oxidation product and the crushed asphalt are placed in a VC mixer and mixed to obtain a hard carbon precursor;

[0034] S4. Place the hard carbon precursor in an inert atmosphere for high-temperature carbonization treatment, and cool to room temperature after the reaction is completed to obtain a hard carbon negative electrode material.

[0035] High temperature carbonization converts asphalt and semi-coke into hard carbon. The polycondensation reaction of asphalt and the pore structure of semi-coke synergistically form a "closed pore + open pore" composite system, which uses closed pores to store Na + , the openings promote electrolyte penetration.

[0036] In a specific implementation case, the lignite selected is lignite produced in Xinjiang.

[0037] In a specific implementation case, the particle size of the semi-coal after crushing is d 50 3-10 μm, including but not limited to 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm.

[0038] In a specific implementation case, the pickling liquid is hydrochloric acid, hydrofluoric acid or a combination of the two. The pickling liquid is used to dissolve metal oxides and improve carbon purity. After pickling, the specific surface area and porosity of the lignite increase, which is beneficial for subsequent pre-oxidation and asphalt penetration; the reduction of ash content can avoid side reactions with the electrolyte.

[0039] In a specific embodiment, the pre-oxidation temperature is 300-500°C, including but not limited to 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, and 500°C; the time is 3-5h, including but not limited to 3h, 4h, and 5h.

[0040] Low-temperature pre-burning in air generates oxygen-containing functional groups (-COOH, -OH) on the surface of semi-coke, which enhances the interface bonding with asphalt; at the same time, part of the microporous structure is retained, forming more defect sites, which is conducive to Na + Adsorption.

[0041] In a specific implementation case, the asphalt is selected from any one or any combination of petroleum asphalt, coal asphalt, and natural asphalt.

[0042] In a specific implementation case, the particle size of the asphalt after the crushing treatment is d 50 3±1μm.

[0043] In a specific implementation case, the mass ratio of the pre-oxidation product to the asphalt is (2-4):1; including but not limited to 2:1, 3:1, and 4:1.

[0044] In a specific embodiment, the inert atmosphere is preferably nitrogen.

[0045] In a specific embodiment, the carbonization treatment temperature is 1100-1500°C, including but not limited to 1100°C, 1200°C, 1300°C, 1400°C, and 1500°C; and the time is 2-4h, including but not limited to 2h, 3h, and 4h.

[0046] The following is further explained with reference to specific embodiments.

[0047] Example 1

[0048] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0049] S1. Use a mechanical crusher to crush the semi-coal blocks into d 50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0050] S2. The semi-coke powder was placed in a tube furnace and heated to 400°C at a heating rate of 5°C / min in an air atmosphere for pre-oxidation and calcination for 4 hours. After the calcination, the mixture was cooled to room temperature to obtain a pre-oxidation product.

[0051] S3. Crushing the asphalt to d 50 The pre-oxidation product and the crushed asphalt were mixed in a VC mixer at a mass ratio of 3:1 to obtain a hard carbon precursor.

[0052] S4. Place the hard carbon precursor in nitrogen and heat it to 1300°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0053] Example 2

[0054] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0055] S1. Use a mechanical crusher to crush the semi-coal blocks into d 50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0056] S2. The blue carbon powder was placed in a tube furnace and heated to 300°C at a heating rate of 5°C / min in an air atmosphere for pre-oxidation and calcination for 4 hours. After the calcination, the mixture was cooled to room temperature to obtain a pre-oxidation product.

[0057] S3. Crushing the asphalt to d 50 The pre-oxidation product and the crushed asphalt were mixed in a VC mixer at a mass ratio of 3:1 to obtain a hard carbon precursor.

[0058] S4. Place the hard carbon precursor in nitrogen and heat it to 1300°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0059] Example 3

[0060] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0061] S1. Use a mechanical crusher to crush the semi-coal blocks into d 50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0062] S2. The semi-coke powder was placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min in an air atmosphere for pre-oxidation and calcination for 4 hours. After the calcination, the mixture was cooled to room temperature to obtain a pre-oxidation product.

[0063] S3. Crushing the asphalt to d 50 The pre-oxidation product and the crushed asphalt were mixed in a VC mixer at a mass ratio of 3:1 to obtain a hard carbon precursor.

[0064] S4. Place the hard carbon precursor in nitrogen and heat it to 1300°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0065] Example 4

[0066] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0067] S1. Use a mechanical crusher to crush the semi-coal blocks into d 50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0068] S2. The semi-coke powder was placed in a tube furnace and heated to 400°C at a heating rate of 5°C / min in an air atmosphere for pre-oxidation and calcination for 4 hours. After the calcination, the mixture was cooled to room temperature to obtain a pre-oxidation product.

[0069] S3. Crushing the asphalt to d 50 The pre-oxidation product and the crushed asphalt were mixed in a VC mixer at a mass ratio of 4:1 to obtain a hard carbon precursor;

[0070] S4. Place the hard carbon precursor in nitrogen and heat it to 1300°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0071] Example 5

[0072] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0073] S1. Use a mechanical crusher to crush the semi-coal blocks into d 50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0074] S2. The semi-coke powder was placed in a tube furnace and heated to 400°C at a heating rate of 5°C / min in an air atmosphere for pre-oxidation and calcination for 4 hours. After the calcination, the mixture was cooled to room temperature to obtain a pre-oxidation product.

[0075] S3. Crushing the asphalt to d 50 The pre-oxidation product and the crushed asphalt were mixed in a VC mixer at a mass ratio of 2:1 to obtain a hard carbon precursor;

[0076] S4. Place the hard carbon precursor in nitrogen and heat it to 1300°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0077] Example 6

[0078] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0079] S1. Use a mechanical crusher to crush the semi-coal blocks into d 50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0080] S2. The semi-coke powder was placed in a tube furnace and heated to 400°C at a heating rate of 5°C / min in an air atmosphere for pre-oxidation and calcination for 4 hours. After the calcination, the mixture was cooled to room temperature to obtain a pre-oxidation product.

[0081] S3. Crushing the asphalt to d 50 The pre-oxidation product and the crushed asphalt were mixed in a VC mixer at a mass ratio of 3:1 to obtain a hard carbon precursor.

[0082] S4. Place the hard carbon precursor in nitrogen and heat it to 1500°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0083] Example 7

[0084] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0085] S1. Use a mechanical crusher to crush the semi-coal blocks into d 50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0086] S2. The semi-coke powder was placed in a tube furnace and heated to 400°C at a heating rate of 5°C / min in an air atmosphere for pre-oxidation and calcination for 4 hours. After the calcination, the mixture was cooled to room temperature to obtain a pre-oxidation product.

[0087] S3. Crushing the asphalt to d 50 The pre-oxidation product and the crushed asphalt were mixed in a VC mixer at a mass ratio of 3:1 to obtain a hard carbon precursor.

[0088] S4. Place the hard carbon precursor in nitrogen and heat it to 1100°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0089] Comparative Example 1

[0090] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0091] S1. Use a mechanical crusher to crush the semi-coal blocks into d 50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0092] S2. Crushing the asphalt to d 50 The semi-coke powder and the crushed asphalt were mixed in a VC mixer at a mass ratio of 3:1 to obtain a hard carbon precursor.

[0093] S3. Place the hard carbon precursor in nitrogen and heat it to 1300°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0094] Comparative Example 2

[0095] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0096] S1. Use a mechanical crusher to crush the semi-coal blocks into d 50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0097] S2. The semi-coke powder was placed in a tube furnace and heated to 400°C at a heating rate of 5°C / min in an air atmosphere for pre-oxidation and calcination for 4 hours. After the calcination, the mixture was cooled to room temperature to obtain a pre-oxidation product.

[0098] S3. Place the pre-oxidation product in nitrogen and heat it to 1300°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0099] Comparative Example 3

[0100] A method for preparing a hard carbon negative electrode material for a sodium ion battery comprises the following steps:

[0101] S1. Use a mechanical crusher to crush the semi-coal blocks into d50 The pulverized semi-coke of 10 μm is deashed by pickling with 10% by mass dilute hydrochloric acid and 10% by mass hydrofluoric acid, then washed with deionized water until neutral, and dried to obtain semi-coke powder;

[0102] S2. The semi-coke powder was placed in a tube furnace and heated to 400°C at a heating rate of 5°C / min in an air atmosphere for pre-oxidation and calcination for 4 hours. After the calcination, the mixture was cooled to room temperature to obtain a pre-oxidation product.

[0103] S3. Crushing the asphalt to d 50 The pre-oxidation product and the crushed asphalt were mixed in a VC mixer at a mass ratio of 1:1 to obtain a hard carbon precursor.

[0104] S4. Place the hard carbon precursor in nitrogen and heat it to 1300°C at a heating rate of 5°C / min for high-temperature carbonization treatment for 2 hours. After the reaction is completed, cool it to room temperature to obtain a hard carbon negative electrode material.

[0105] The performance tests were conducted on the hard carbon negative electrode materials for ion batteries prepared in Examples 1-7 and Comparative Examples 1-3:

[0106] 80% of the sodium ion battery hard carbon negative electrode material and 20% of other materials (well known in the art) with a mass ratio of SuperP:PVDF=1:1 are assembled into electrodes. The electrolyte is a solvent with a volume ratio of EC:DEC=1:1 in which 1 mol of sodium hexafluorophosphate is dissolved. The separator is glass fiber, and the positive electrode is a sodium sheet. The battery is processed into a CR2032 button battery.

[0107] The test conditions are: first discharge at a rate of 0.1°C, then discharge at a constant current of 0.02mA, and then charge at a rate of 0.1C for testing.

[0108] The test results are shown in Table 1.

[0109] Table 1

[0110]

[0111] The first charge and discharge test diagram of the battery assembled from the hard carbon negative electrode material for the ion battery prepared in Example 1 is shown in FIG. Figure 1 .

[0112] It can be seen from the above test results that the present invention uses pre-oxidation to precisely control the pore distribution of lignite, balancing the specific surface area and the first effect; and then regulates the doping amount of asphalt to adjust the interlayer spacing and conductivity of the hard carbon. When it is excessive, it may cause the blockage and collapse of the lignite pores, and the battery performance is poor at this time.

[0113] In summary, the sodium ion battery hard carbon negative electrode material prepared by the present invention has excellent electrochemical properties and can be widely used in sodium ion batteries.

[0114] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0115] The above disclosures are only a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a hard carbon negative electrode material for a sodium ion battery, characterized in that: The following steps are involved: S1. The semi-coke block is crushed and then subjected to acid washing and deashing treatment, then washed with water until neutral, and dried to obtain semi-coke powder; S2. The blue carbon powder is pre-oxidized and calcined to obtain a pre-oxidized product; S3. Adding the crushed asphalt to the pre-oxidation product and mixing uniformly to obtain a hard carbon precursor; S4. Carbonizing the hard carbon precursor in an inert atmosphere to obtain a hard carbon negative electrode material.

2. The method for preparing a hard carbon negative electrode material for sodium ion batteries according to claim 1, wherein: In S1, the particle size d of the semi-coal block after crushing 50 3-10μm.

3. The method for preparing a hard carbon negative electrode material for sodium ion batteries according to claim 1, wherein: In S1, the pickling liquid in the pickling and deashing process is hydrochloric acid, hydrofluoric acid or a combination of the two.

4. The method for preparing a hard carbon negative electrode material for sodium ion batteries according to claim 1, wherein: In S2, the temperature of the pre-oxidation calcination is 300-500°C and the time is 3-5 hours.

5. The method for preparing a hard carbon negative electrode material for sodium ion batteries according to claim 1, wherein: In S3, the asphalt is any one of petroleum asphalt, coal asphalt, and natural asphalt, or a combination of several of them.

6. The method for preparing a hard carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: In S3, the particle size d of the crushed asphalt 50 3±1μm.

7. The method for preparing a hard carbon negative electrode material for sodium ion batteries according to claim 1, wherein: In S3, the mass ratio of the pre-oxidation product to the asphalt is (2-4):

1.

8. The method for preparing a hard carbon negative electrode material for sodium ion batteries according to claim 1, wherein: In S4, the inert atmosphere is nitrogen.

9. The method for preparing a hard carbon negative electrode material for sodium ion batteries according to claim 1, characterized in that: In S4, the carbonization treatment temperature is 1100-1500° C. and the time is 2-4 hours.

10. A hard carbon negative electrode material for a sodium ion battery, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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