Negative active material, preparation and application thereof, and sodium-ion battery negative electrode material and sodium-ion battery negative electrode and application

Abstract

This invention relates to the field of electrochemical technology, and discloses a negative electrode active material and its preparation and application, as well as a sodium-ion battery negative electrode material and sodium-ion battery negative electrode and its application. The method includes the following steps: (1) mixing a petroleum-based material and a hard carbon precursor with a solvent to obtain a mixed slurry; (2) drying the mixed slurry obtained in step (1); (3) pretreating and carbonizing the product of step (2) at high temperature to obtain the negative electrode active material; wherein, the mass ratio of the petroleum-based material and the hard carbon precursor in step (1) is 0.1-4:1. The preparation method of this negative electrode active material adopts a composite method of petroleum-based material and hard carbon precursor, which is simple to prepare and easy to scale up industrially; at the same time, it combines the advantages of both materials, improves the overall carbon production rate, and can achieve a combined improvement in the reversible capacity and first-cycle coulombic efficiency of sodium-ion battery negative electrode.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically to a negative electrode active material and its preparation and application, as well as sodium-ion battery negative electrode materials and sodium-ion battery negative electrodes and their applications. Background Technology

[0002] Secondary batteries are crucial for converting clean energy sources such as solar, wind, and tidal energy into chemical energy. They effectively address the geographical and intermittent limitations of clean energy, enabling stable energy storage and continuous output. Existing secondary battery systems, such as lithium-ion batteries, offer advantages like high energy density, good cycle stability, and low self-discharge, leading to their widespread use in mobile electronics, communication equipment, electric devices, and electric vehicles. However, their large-scale energy storage is constrained by lithium resource scarcity. Developing novel high-energy-density secondary batteries to address resource shortages is a key research focus in this field. The application of sodium-ion batteries can not only alleviate the global lithium resource shortage and narrow the supply-demand gap, but also benefit from abundant sodium salt reserves and mature extraction processes, resulting in lower material costs and less cost fluctuation for sodium-ion batteries.

[0003] Similar to the working principle of lithium-ion batteries, designing and developing electrode materials capable of accommodating stable sodium ion insertion and extraction is crucial for the commercialization of sodium-ion batteries. In academia, various anode materials for sodium-ion batteries have been developed, including conversion reaction materials, alloyed materials, titanium-based materials, and carbon-based materials. Amorphous carbon-based anodes (including hard carbon and soft carbon) exhibit high reversible specific capacity and good cycle performance in sodium-ion batteries. Since their discovery, researchers have conducted extensive exploration and research on these materials. Hard carbon materials are currently the most promising anode materials for sodium-ion rechargeable batteries; however, the low carbon yield of precursors used to produce hard carbon leads to high costs, hindering their commercial application. In contrast, preparing carbon-based anode materials from petroleum-based products offers high carbon yield, low cost, and a complete raw material supply chain, facilitating rapid market integration. However, the direct high-temperature carbonization of materials such as petroleum coke and pitch yields soft carbon materials, which suffer from low specific capacity and high sodium storage voltage. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low carbon yield, high cost, and poor performance of hard carbon precursor materials in existing technologies. It provides a negative electrode active material, its preparation and application, as well as a sodium-ion battery negative electrode material and its application. The preparation method of this negative electrode active material adopts a composite approach of petroleum-based materials and hard carbon precursors. The preparation method is simple and easy to scale up industrially. It also combines the advantages of both materials, improving the overall carbon yield and achieving a simultaneous increase in the reversible capacity and first-cycle coulombic efficiency of the sodium-ion battery negative electrode.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a negative electrode active material, wherein the method includes the following steps:

[0006] (1) The petroleum-based material and hard carbon precursor are mixed with a solvent to obtain a mixed slurry;

[0007] (2) The mixed slurry obtained in step (1) is dried;

[0008] (3) The product of step (2) is pretreated and carbonized at high temperature to obtain the negative electrode active material;

[0009] In step (1), the mass ratio of petroleum-based material to hard carbon precursor is 0.1-4:1.

[0010] Preferably, the softening point of the petroleum-based material is 100-300℃, and more preferably 200-300℃.

[0011] Preferably, the ash content in the petroleum-based material is 0-0.5 wt%, more preferably 0-0.1 wt%.

[0012] Preferably, the pretreatment conditions include: a pretreatment temperature of 160-350℃, preferably 180-250℃, a heating rate of 1-6℃ / min, preferably 2-5℃ / min, and a pretreatment time of 2-60 hours, preferably 24-60 hours.

[0013] The second aspect of the present invention provides a negative electrode active material prepared by the preparation method described in the first aspect.

[0014] The third aspect of this invention provides the application of the negative electrode active material described in the second aspect in a sodium-ion battery.

[0015] A fourth aspect of the present invention provides a sodium-ion battery negative electrode material, the negative electrode material comprising a negative electrode active material and a binder, wherein the negative electrode active material is the negative electrode active material described in the second aspect.

[0016] The fifth aspect of the present invention provides a sodium-ion battery negative electrode, the negative electrode comprising a current collector and a negative electrode material coated and / or filled on the current collector, wherein the negative electrode material is the negative electrode material described in the fourth aspect of the present invention.

[0017] The sixth aspect of this invention provides the application of the sodium-ion battery negative electrode described in the fifth aspect in a sodium-ion battery.

[0018] The beneficial effects achieved through the above technical solution are as follows:

[0019] (1) In this invention, the negative electrode active material is prepared by using petroleum-based materials and hard carbon precursors as carbon sources. After pretreatment and high-temperature carbonization, the negative electrode active material is obtained. The preparation method is simple and easy to scale up industrially. It also has the advantages of both soft carbon and hard carbon materials, which improves the overall carbon yield and reduces the cost.

[0020] (2) In this invention, preferably, the obtained negative electrode active material is used to prepare a sodium-ion battery negative electrode material for use in sodium-ion batteries, which has high reversible capacity and first-cycle coulombic efficiency. Attached Figure Description

[0021] Figure 1 This is the XRD pattern of the negative electrode active material prepared in Example 1;

[0022] Figure 2 This is a SEM image of the negative electrode active material prepared in Example 1. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The first aspect of this invention provides a method for preparing a negative electrode active material, wherein the method includes the following steps:

[0025] (1) The petroleum-based material and hard carbon precursor are mixed with a solvent to obtain a mixed slurry;

[0026] (2) The mixed slurry obtained in step (1) is dried;

[0027] (3) The product of step (2) is pretreated and carbonized at high temperature to obtain the negative electrode active material;

[0028] In step (1), the mass ratio of petroleum-based material to hard carbon precursor is 0.1-4:1.

[0029] In this invention, petroleum-based materials and hard carbon precursors are mixed as carbon sources. Petroleum-based materials have a high carbon yield, while the addition of hard carbon precursors can produce a composite negative electrode active material of soft and hard carbon after high-temperature carbonization treatment, thereby improving the specific capacity of the material and reducing the sodium storage voltage.

[0030] According to the present invention, preferably, the mass ratio of the petroleum-based material and the hard carbon precursor in step (1) is 0.1-4:1, for example, 0.1:1, 0.2:1, 0.4:1, 0.6:1, 0.8:1, 1.2:1, 1.6:1, 2:1, 2.4:1, 2.8:1, 3.2:1, 3.6:1, 4:1, or any range between the two, preferably 0.4-2.4:1. Mixing the petroleum-based material and the hard carbon precursor using the above mass ratio not only combines the advantages of both precursors, but also allows the hard carbon precursor to induce an increase in disorder in the soft carbon structure during pyrolysis. The resulting negative electrode active material is further used to prepare a negative electrode material for sodium-ion batteries, exhibiting high reversible capacity and first-cycle coulombic efficiency.

[0031] According to the present invention, the petroleum-based material in step (1) is a conventional carbon material made from petroleum, preferably selected from at least one of pitch, petroleum coke and needle coke, and more preferably pitch. In the present invention, the source of the petroleum-based material is not particularly limited; it can be commercially available or prepared by existing methods, and is a powder with a uniform particle size distribution.

[0032] According to the present invention, preferably, the softening point of the asphalt is 100-300℃, more preferably 200-300℃. In this invention, the method for testing the softening point of the asphalt is to place the asphalt raw material in a specially made test tube, heat it at a stable heating rate under a nitrogen atmosphere, and continuously probe the asphalt with a steel needle rod with a diameter of 1mm during the process. When the asphalt becomes soft and begins to adhere to the steel needle, the temperature at this point is recorded, which is the softening point of the asphalt.

[0033] According to the present invention, preferably, the mass percentage of ash in the petroleum-based material is 0-0.5 wt%, more preferably 0-0.1 wt%. In the present invention, ash has the conventional interpretation in the art, referring to the inorganic substances remaining after the petroleum-based material is burned or calcined. In the present invention, the mass percentage of ash in the petroleum-based material is determined by a calcination method: (1) record the initial mass of the petroleum-based material sample; (2) place the petroleum-based material sample in a drying oven and dry it to constant weight at a constant temperature of 110℃-115℃; (3) take out the sample, place it in a calciner, bake it at a low temperature for 30 minutes, and then calcin it to constant weight at 815℃; (4) take out the sample, place it in an air cooler to cool it, and weigh the difference in mass of the sample, which is the ash content. The ratio of the ash content to the mass of the petroleum-based material sample is recorded as the mass percentage of ash.

[0034] In this invention, the above-mentioned petroleum-based material is mixed with a hard carbon precursor. The petroleum-based material has a high softening point and low ash content, which is beneficial for improving carbon production rate and the selection of pretreatment process.

[0035] According to the present invention, preferably, the hard carbon precursor is starch and / or lignin, more preferably starch. In the present invention, the type of starch is not particularly limited; those skilled in the art can choose conventional starches, which can be natural starches and / or processed starches. The natural starches include, but are not limited to, at least one selected from legume starch, potato starch, wheat starch, sweet potato starch, cassava starch, rice starch, corn starch, sweet potato flour, and kudzu starch. The processed starches include, but are not limited to, at least one selected from pregelatinized starch, oxidized starch, cross-linked starch, esterified starch, and modified starch.

[0036] In this invention, the source of the hard carbon precursor is not particularly limited; it can be commercially available or prepared by existing methods, and those skilled in the art can make an adaptive choice.

[0037] According to the present invention, there is no particular limitation on the type of solvent. Those skilled in the art can choose conventional volatile organic solvents and / or inorganic solvents, as long as they can mix the petroleum-based material and the hard carbon precursor and can be volatilized and removed. Preferably, the solvent is ethanol and / or water. Adding the above solvent to prepare a mixed slurry allows for uniform mixing of the petroleum-based material and the hard carbon precursor during subsequent sand milling, and is environmentally friendly.

[0038] According to the present invention, there is no particular limitation on the amount of solvent used. Preferably, the total mass ratio of the solvent to the petroleum-based material and the hard carbon precursor is 2-30:1, for example 2:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, or any range between the two, preferably 5-15:1.

[0039] According to the present invention, preferably, step (1) further includes milling the mixed slurry, wherein the milling conditions include:

[0040] The grinding time is 1-10 hours, preferably 3-8 hours; the grinding speed is 1600-2400 r / min, preferably 1800-2200 r / min. In this invention, the grinding equipment is not particularly limited, as long as it can grind the mixed slurry uniformly; those skilled in the art can choose conventional grinding equipment.

[0041] According to the present invention, preferably, in step (2), the drying conditions include: spray drying under a protective atmosphere, with a spray pressure of 0.1-0.4 MPa, preferably 0.2-0.3 MPa, and a temperature of 100-220°C, preferably 150-200°C. In the present invention, preferably, spray drying of the mixed slurry under the above conditions can ensure the morphology of the mixed material while evaporating the solvent, preventing agglomeration, improving dispersibility, and ensuring the cycle stability of the obtained negative electrode material.

[0042] In this invention, the type of protective atmosphere is not particularly limited. Those skilled in the art can choose a conventional, stable protective atmosphere, preferably selected from at least one of nitrogen, helium, argon, and neon.

[0043] According to the present invention, preferably, the pretreatment conditions include: a pretreatment temperature of 160-350℃, preferably 180-250℃, a heating rate of 1-6℃ / min, preferably 2-5℃ / min, and a pretreatment time of 2-60 hours, preferably 24-60 hours.

[0044] In this invention, preferably, pretreatment under the above conditions can maintain the initial spherical structure of starch granules, prevent expansion and melting, and enable them to form a stable cross-linked structure.

[0045] According to the present invention, preferably, the conditions for high-temperature carbonization include: a reaction temperature of 1000-1300℃, preferably 1100-1300℃, a heating rate of 2-10℃ / min, preferably 3-8℃ / min, and a reaction time of 0.5-4 hours, preferably 1-3 hours.

[0046] In this invention, the equipment used for the pretreatment and high-temperature carbonization is not particularly limited, and those skilled in the art can make appropriate selections. According to a specific embodiment of this invention, the pretreatment and high-temperature carbonization are carried out in a tube furnace.

[0047] The second aspect of the present invention provides a negative electrode active material prepared by the preparation method described in the first aspect.

[0048] According to the present invention, preferably, the interlayer spacing of the negative electrode active material is 0.36-0.4 nm, more preferably 0.39-0.4 nm. This preferred embodiment is more conducive to improving the sodium storage capacity of the negative electrode active material. The interlayer spacing is the carbon interlayer spacing of the negative electrode active material, which is calculated using the Bragg equation.

[0049] Specifically, in this invention, the X-ray diffraction pattern of the negative electrode active material was obtained using an XRD-6000 X-ray powder diffractometer (Shimadzu, Japan). The XRD testing conditions were: Cu target, Kα rays (wavelength λ = 0.154 nm), tube voltage 40 kV, tube current 200 mA, and scanning speed 10°(2θ) / min. (Reference) Figure 1 The X-ray diffraction pattern of the negative electrode active material shows a diffraction peak at a 2θ angle of 22.3 ± 0.5°, which corresponds to the (002) diffraction peak of the hard carbon material, proving that hard carbon material was generated in the negative electrode active material.

[0050] The third aspect of this invention provides the application of the negative electrode active material described in the second aspect in a sodium-ion battery.

[0051] The fourth aspect of the present invention provides a sodium-ion battery anode material, the anode material comprising an anode active material and a binder, wherein the anode active material is the anode active material described in the second aspect.

[0052] In this invention, the negative electrode material prepared using the above-mentioned negative electrode active material is used in sodium-ion batteries and has high reversible capacity and first-cycle coulombic efficiency.

[0053] In this invention, the amount and type of binder for the electrode material can be selected within a wide range, and can be chosen according to conventional techniques in the art. According to a preferred embodiment of the invention, the binder is sodium alginate, which can be provided in the form of an aqueous solution. The amount of binder used is sufficient to prepare the negative electrode material from the negative electrode active material; those skilled in the art can adjust this appropriately.

[0054] The fifth aspect of the present invention provides a sodium-ion battery negative electrode, the negative electrode comprising a current collector and a negative electrode material coated and / or filled on the current collector, wherein the negative electrode material is the negative electrode material described in the fourth aspect of the present invention.

[0055] The sixth aspect of this invention provides the application of the sodium-ion battery negative electrode described in the fifth aspect in a sodium-ion battery.

[0056] According to the present invention, preferably, the sodium-ion battery includes an electrode assembly and a non-aqueous electrolyte, the electrode assembly and the non-aqueous electrolyte being sealed within a battery casing, the electrode assembly including a positive electrode, a negative electrode and a separator, the separator being located between the positive electrode and the negative electrode, and the negative electrode being the negative electrode of the sodium-ion battery as described in the fifth aspect.

[0057] In this invention, the non-aqueous electrolyte refers to an electrolyte solution whose solvent is not water. Those skilled in the art can select a suitable non-aqueous electrolyte based on the composition of the sodium-ion battery, and no limitation is made here.

[0058] According to a particularly preferred embodiment of the present invention, a method for preparing a negative electrode active material includes the following steps:

[0059] (1) The petroleum-based material and hard carbon precursor are mixed with a solvent to obtain a mixed slurry;

[0060] (2) The mixed slurry obtained in step (1) is subjected to spray drying treatment;

[0061] (3) The product of step (2) is pretreated and carbonized at high temperature to obtain the negative electrode active material;

[0062] In step (1), the mass ratio of petroleum-based material to hard carbon precursor is 0.4-2.4:1;

[0063] The petroleum-based material mentioned in step (1) is asphalt; the hard carbon precursor is starch;

[0064] The softening point of the asphalt is 200-300℃;

[0065] The ash content in the asphalt is 0-0.1 wt% by mass;

[0066] The interlayer spacing of the negative electrode active material is 0.39-0.4 nm.

[0067] The present invention will be described in detail below through examples and comparative examples. In the following examples and comparative examples, the room temperature is 25°C; unless otherwise specified, all reagents used are commercially available.

[0068] The microstructure of the negative electrode active material was observed using a scanning electron microscope.

[0069] Example 1

[0070] (1) Mix asphalt (high temperature petroleum asphalt) and starch (corn starch) in a mass ratio of 1:1, dissolve them in ethanol solvent, the mass ratio of ethanol solvent to asphalt and starch is 10:1, sand mill for 6 hours at a sand mill speed of 2200 r / min to obtain a mixed slurry, wherein the softening point of the asphalt is 278℃ and the ash content is 0.05wt%.

[0071] (2) The mixed slurry obtained in step (1) is spray-dried under a nitrogen atmosphere with a spray pressure of 0.2 MPa and a temperature of 180°C.

[0072] (3) Place the product obtained in step (2) in a tube furnace, and under a nitrogen atmosphere, first heat it to 220°C at a heating rate of 2°C / min and hold it for 48 hours, then change the heating rate to 5°C / min and heat it to 1200°C and hold it for 2 hours. After natural cooling, the negative electrode active material is obtained.

[0073] Figure 1 To obtain the X-ray diffraction (XRD) pattern of the negative electrode active material, from Figure 1 As can be seen, there is a diffraction peak at 22.3° of 2θ angle, which corresponds to the (002) diffraction peak of hard carbon material.

[0074] Figure 2 To obtain SEM images of the negative electrode active material, such as... Figure 2 As shown, the overall structure of the material is spherical.

[0075] Example 2

[0076] (1) Mix asphalt (high temperature petroleum asphalt) and starch (corn starch) in a ratio of 7:3, dissolve in an appropriate amount of ethanol solvent, and sand mill for 8 hours at a speed of 1800 r / min. The softening point of the asphalt is 278℃ and the ash content is 0.05wt%.

[0077] (2) The mixed slurry obtained in step (1) is spray-dried under a nitrogen atmosphere with a spray pressure of 0.2 MPa and a temperature of 150 °C.

[0078] (3) The product obtained in step (2) is placed in a tube furnace. Under a nitrogen atmosphere, the temperature is first raised to 250°C at a heating rate of 5°C / min and held for 60 hours. Then the temperature is raised to 1300°C at a heating rate of 8°C / min and held for 1 hour. After natural cooling, the sodium-ion battery negative electrode active material is obtained.

[0079] Example 3

[0080] (1) Mix asphalt (high temperature petroleum asphalt) and starch (corn starch) in a ratio of 3:7, dissolve in an appropriate amount of ethanol solvent, and sand mill for 3 hours at a speed of 2500 r / min. The softening point of the asphalt is 278℃ and the ash content is 0.05wt%.

[0081] (2) The mixed slurry obtained in step (1) is spray-dried under a nitrogen atmosphere with a spray pressure of 0.2 MPa and a temperature of 200 °C.

[0082] (3) The product obtained in step (2) is placed in a tube furnace. Under a nitrogen atmosphere, the temperature is first raised to 180°C at a rate of 2°C / min and held for 24 hours. Then the temperature is raised to 1100°C at a rate of 3°C / min and held for 3 hours. After natural cooling, the sodium-ion battery negative electrode active material is obtained.

[0083] Example 4

[0084] (1) Mix needle coke (source: China Petrochemical Maoming Petrochemical Co., Ltd.) and starch (corn starch) in a 1:1 ratio, dissolve in an appropriate amount of ethanol solvent, and sand mill for 6 hours at a sand mill speed of 2200 r / min. The ash content is 0.5 wt%.

[0085] (2) The mixed slurry obtained in step (1) is spray-dried under a nitrogen atmosphere with a spray pressure of 0.2 MPa and a temperature of 180°C.

[0086] (3) The product obtained in step (2) is placed in a tube furnace. Under a nitrogen atmosphere, the temperature is first raised to 220°C at a heating rate of 2°C / min and held for 48 hours. Then the temperature is raised to 1200°C at a heating rate of 5°C / min and held for 2 hours. After natural cooling, the sodium-ion battery negative electrode active material is obtained.

[0087] Example 5

[0088] Following the method of Example 1, except that starch was replaced with an equal mass of lignin (alkali-degraded lignin), and other conditions were the same as in Example 1, the negative electrode active material was obtained.

[0089] Example 6

[0090] The method of Example 1 was followed, except that the amount of asphalt added in step (1) was changed so that the mass ratio of asphalt to starch was 4:1, and other conditions were the same as in Example 1, to obtain the negative electrode active material.

[0091] Example 7

[0092] The method is the same as in Example 1, except that step (2) is performed by blowing air at a temperature of 110°C to obtain the negative electrode active material.

[0093] Comparative Example 1

[0094] (1) The method of Example 1 is followed, except that asphalt and starch are mixed in a 1:1 ratio and ball-milled for 6 hours;

[0095] (2) The product obtained in step (1) is placed in a tube furnace. Under a nitrogen atmosphere, the temperature is first raised to 220°C at a heating rate of 2°C / min and held for 48 hours. Then the temperature is raised to 1200°C at a heating rate of 5°C / min and held for 2 hours. After natural cooling, the negative electrode active material is obtained.

[0096] Comparative Example 2

[0097] (1) The method of Example 1 is followed, except that asphalt and starch are mixed in a 1:1 ratio and ball-milled for 6 hours;

[0098] (2) The product obtained in step (1) is placed in a tube furnace and heated to 1200°C at a heating rate of 5°C / min under a nitrogen atmosphere and held for 2 hours. After natural cooling, sodium-ion battery negative electrode active material is obtained.

[0099] Test case

[0100] The negative electrode active materials obtained in the examples and comparative examples were used to prepare sodium-ion battery negative electrode sheets and assembled into batteries.

[0101] 1) Preparation of the negative electrode sheet:

[0102] The dried negative electrode active materials prepared in the above examples and comparative examples were mixed with an aqueous solution of sodium alginate (binder, sodium alginate mass fraction of 2%) at a mass ratio of 9:1 and stirred on a magnetic stirrer for 6 hours to obtain a paste-like slurry. The obtained paste-like slurry was uniformly coated on the current collector copper foil and then dried in a vacuum drying oven at 100°C for 20 hours for later use.

[0103] 2) Battery assembly:

[0104] The dried negative electrode sheet was formed into a circular sheet with a diameter of 12 mm; and held under a pressure of 8 MPa for 30-180 seconds to obtain the negative electrode of the sodium-ion battery. Using a metallic sodium sheet as the counter electrode, glass fiber as the separator, and 1 mol / L sodium hexafluorophosphate as the electrolyte, with a solvent volume ratio of EC (ethylene carbonate):DEC (diethyl carbonate) = 1:1, a CR2032 coin cell was assembled. The entire battery assembly was completed in a glove box, thus obtaining the sodium-ion battery.

[0105] Routine battery performance testing: The LAND CT2001A charge / discharge tester from Wuhan Lanbo Electronics Co., Ltd. was used to conduct charge / discharge tests on the batteries. The charge / discharge voltage range was 0V to 2.5V. The specific capacity of the assembled sodium-ion batteries was tested at a 0.1C rate.

[0106] The performance test results of the sodium-ion batteries prepared in the examples and comparative examples are shown in Table 1.

[0107] Table 1

[0108]

[0109] As can be seen from the results in Table 1, the present invention prepares negative electrode active materials based on low-cost petroleum-based materials and precursor carbon sources through low-temperature pretreatment and high-temperature carbonization. When these materials are used as negative electrode active materials in sodium-ion batteries, they exhibit high reversible capacity and first-cycle coulombic efficiency.

[0110] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a negative electrode active material, characterized in that, The method includes the following steps: (1) The petroleum-based material and the hard carbon precursor are mixed with a solvent to obtain a mixed slurry; (2) The mixed slurry obtained in step (1) is dried; (3) The product of step (2) is pretreated and carbonized at high temperature to obtain the negative electrode active material; In step (1), the mass ratio of petroleum-based material to hard carbon precursor is 0.4-2.4:1; The petroleum-based material mentioned in step (1) is asphalt; In step (2), the drying conditions include: spray drying under a protective atmosphere, with a spray pressure of 0.1-0.4 MPa and a temperature of 100-220°C; The hard carbon precursor is starch; The softening point of the asphalt is 200-300℃; the ash content in the petroleum-based material is 0-0.1 wt% by mass. The total mass ratio of the solvent to the petroleum-based material and the hard carbon precursor is 2-30:1; The pretreatment conditions include: a pretreatment temperature of 160-350℃, a heating rate of 1-6℃ / min, and a pretreatment time of 2-60 hours; Step (1) also includes sand milling the mixed slurry.

2. The preparation method according to claim 1, wherein, The solvent is ethanol and / or water.

3. The preparation method according to claim 1, wherein, The total mass ratio of the solvent to the petroleum-based material and the hard carbon precursor is 5-15:

1.

4. The preparation method according to claim 1, wherein, The pretreatment conditions include: a pretreatment temperature of 180-250℃, a heating rate of 2-5℃ / min, and a pretreatment time of 24-60 hours.

5. The preparation method according to claim 1, wherein, The conditions for high-temperature carbonization include: a reaction temperature of 1000-1300℃, a heating rate of 2-10℃ / min, and a reaction time of 0.5-4 hours.

6. The preparation method according to claim 5, wherein, The conditions for high-temperature carbonization include: a reaction temperature of 1100-1300℃, a heating rate of 3-8℃ / min, and a reaction time of 1-3 hours.

7. The preparation method according to claim 1, wherein, The pretreatment and high-temperature carbonization are carried out under a protective atmosphere selected from at least one of nitrogen, helium, argon and neon.

8. The preparation method according to claim 1, wherein, The grinding conditions include: The grinding time is 1-10 hours; the grinding speed is 1600-2400 r / min.

9. The preparation method according to claim 8, wherein, The grinding time is 3-8 hours; the grinding speed is 1800-2200 r / min.

10. The preparation method according to claim 1, wherein, In step (2), the drying conditions include: spray drying under a protective atmosphere, with a spray pressure of 0.2-0.3 MPa and a temperature of 150-200℃.

11. The negative electrode active material prepared by the preparation method according to any one of claims 1-10.

12. The negative electrode active material according to claim 11, wherein, The interlayer spacing of the negative electrode active material is 0.36-0.4 nm.

13. The negative electrode active material according to claim 12, wherein, The interlayer spacing of the negative electrode active material is 0.39-0.4 nm.

14. The use of the negative electrode active material according to any one of claims 11-13 in a sodium-ion battery.

15. The application according to claim 14, wherein, The application of the negative electrode active material in sodium-ion battery negative electrode materials.

16. A sodium-ion battery negative electrode material, said negative electrode material comprising a negative electrode active material and a binder, characterized in that, The negative electrode active material is the negative electrode active material according to any one of claims 11-13.

17. A sodium-ion battery negative electrode, characterized in that, The negative electrode includes a current collector and a negative electrode material coated and / or filled on the current collector, wherein the negative electrode material is the negative electrode material as described in claim 16.

18. The application of the sodium-ion battery negative electrode according to claim 17 in a sodium-ion battery.

19. The application according to claim 18, wherein, The sodium-ion battery includes an electrode assembly and a non-aqueous electrolyte, which are sealed inside the battery casing. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrodes.

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