Hard carbon negative electrode material, preparation method thereof, application and sodium ion battery

Abstract

The application discloses a kind of hard carbon negative electrode material and its preparation method, application and sodium ion battery.The preparation method of the hard carbon negative electrode material includes the following steps: (1) the mixture of phenolic compound, aldehyde compound and amine compound is heat treated, and resin solution is prepared;Among them, amine compound is aliphatic amine;The molar ratio of phenolic compound and aldehyde compound is 1:(1-3);The molar ratio of phenolic compound and amine compound is 1:(0.2-3);(2) the resin solution is spray dried, carbonized, and the hard carbon negative electrode material is prepared;Carbonization includes first carbonization and second carbonization.The hard carbon negative electrode material prepared by the application has a regular microstructure, is rich in nitrogen elements, has a suitable pore size distribution and specific surface area, and has excellent electrochemical performance when applied to batteries;Meanwhile, the process preparation method can realize in-situ doping of nitrogen elements, the preparation process is simple, can realize large-scale production, and has good industrial application prospect.

Description

Technical Field

[0001] This invention relates to a hard carbon anode material, its preparation method, applications, and sodium-ion batteries. Background Technology

[0002] In recent years, with the large-scale application of lithium-ion batteries in consumer, power, and energy storage fields, the demand for lithium resources has increased. The shortage and uneven distribution of lithium resources have become significant factors restricting the development of lithium-ion batteries. Sodium-ion batteries, as a new type of rechargeable battery, possess numerous advantages such as abundant and widely distributed sodium resources, low cost, and high safety, showing promising application prospects in the low-end power market for two-wheeled vehicles and large-scale energy storage. As is well known, graphite is the most commonly used anode material in lithium-ion batteries due to its abundant resources, excellent conductivity, low average potential, and excellent cycle stability. However, because the ionic radius of sodium ions (0.102 nm) is larger than that of lithium ions (0.076 nm), and due to the small interlayer spacing of graphite (0.34 nm), sodium ions have difficulty penetrating the graphite layers. Furthermore, the thermodynamic instability of the intercalation compounds formed by sodium ions and graphite determines that graphite is not suitable as an anode material for sodium-ion batteries. Therefore, a suitable anode material is crucial for the widespread application of sodium-ion batteries.

[0003] Hard carbon is a type of carbon material that is difficult to graphitize. Its microstructure is highly disordered, with internal entanglements forming abundant defects and nanopores. Unlike graphite, hard carbon's structure is mainly composed of short-range graphitic domains and long-range amorphous features. This structure contains many active sites, such as edges, defects, and functional groups. Meanwhile, the precursor raw materials for hard carbon materials are relatively abundant, including biomass, polysaccharides, resin polymers, coal-based materials, and pitch. Overall, hard carbon is considered one of the most promising anode materials for sodium-ion batteries. Among these, resin polymers are favored by researchers due to their advantages such as high raw material purity, low production difficulty, good product consistency, high residual carbon value, and controllable structure.

[0004] Chinese patent CN106450320B discloses a method for preparing phenolic resin hard carbon. This method involves the condensation and co-precipitation of phenol and aldehyde monomers to obtain a phenolic resin precursor, which is then subjected to hydrothermal reaction, centrifugal washing, freeze-drying, and carbonization to prepare spherical hard carbon. This process is complex and cumbersome, with a long production cycle, accumulating 60-150 hours. Furthermore, the low-temperature freeze-drying process is energy-intensive and unsuitable for industrial production. Chinese patent CN113321202B discloses a method for preparing phenolic resin-based hard carbon microspheres. This method involves adding phenol and aldehyde monomers to an aqueous solution of an alkaline catalyst and a water-soluble polymer to obtain phenolic resin oligomers. After adding water to form an emulsion, the hard carbon material is obtained through spray drying, pre-oxidation, and carbonization. This process requires the use of multiple reagents, involves a strong alkaline catalyst, and has a long preparation cycle. Chinese patent CN109742383B discloses a method for preparing phenolic resin-based sodium-ion battery hard carbon anode material. The method involves mixing phenolic resin and ethanol in different proportions, followed by hydrothermal curing, mechanical crushing, and carbonization to obtain phenolic resin-based hard carbon material. However, the preparation process requires hydrothermal curing, and the microstructure of the finished product is irregular. In practical applications, it often exhibits low bulk density and energy density.

[0005] In addition, for hard carbon materials, nitrogen doping helps to improve electrochemical activity, conductivity and surface wettability, and expands the interlayer spacing. At the same time, nitrogen doping can also generate external defects, which is beneficial to improving the capacity of sodium batteries (J. Mater. Chem. A, 2018, 6.27: 12932-12944.).

[0006] Therefore, optimizing the preparation process of hard carbon materials to obtain hard carbon materials with both controllable microstructure and nitrogen doping is particularly important to improve their electrochemical performance in sodium-ion battery applications. Summary of the Invention

[0007] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies in the preparation of hard carbon materials, which involve complex and cumbersome processes, long production cycles, irregular microstructures, and poor electrochemical performance. This invention provides a hard carbon anode material, its preparation method, applications, and a sodium-ion battery. The hard carbon anode material prepared by this invention has a regular microstructure, is rich in nitrogen, has a suitable pore size distribution and specific surface area, and exhibits excellent electrochemical performance when applied to batteries. Furthermore, the preparation method allows for in-situ doping of nitrogen, is simple to implement, and can be mass-produced, showing promising prospects for industrial applications.

[0008] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0009] This invention provides a method for preparing a hard carbon anode material, comprising the following steps:

[0010] (1) A resin solution is prepared by heat treatment of a mixture of phenolic compounds, aldehyde compounds and amine compounds; wherein the amine compounds are aliphatic amines; the molar ratio of the phenolic compounds to the aldehyde compounds is 1:(1-3); the molar ratio of the phenolic compounds to the amine compounds is 1:(0.2-3);

[0011] (2) The resin solution is spray-dried and carbonized to obtain a hard carbon anode material; the carbonization includes a first carbonization and a second carbonization.

[0012] In step (1), the phenolic compound may be selected from one or more of phenol, bisphenol A, resorcinol and xylenol, such as resorcinol, phenol or xylenol.

[0013] In step (1), the phenolic compound is usually a solid powder, and its addition can be in a conventional manner in the art, such as positive pressure conveying, negative pressure conveying, tubular chain conveying, screw conveying or belt conveying.

[0014] In step (1), the aldehyde compound may be selected from one or more of formaldehyde, furfural, glutaraldehyde, metaldehyde and benzaldehyde, such as formaldehyde, furfural or glutaraldehyde.

[0015] The formaldehyde or furfural can be prepared as a 37 wt% solution for use.

[0016] The glutaraldehyde can be prepared as a 25 wt% solution for use.

[0017] Preferably, the aldehyde compound is a 37 wt% formaldehyde solution, a 37 wt% furfural solution, or a 25 wt% glutaraldehyde solution.

[0018] In step (1), the molar ratio of the phenolic compound to the aldehyde compound is preferably 1:(1-2), for example 1:1.12, 1:1.15, 1:1.2, 1:1.25, 1:1.35, 1:1.5 or 1:2.

[0019] In step (1), the amine compound is preferably one or more of ethylamine, N-methylimidazole, lysine, 1,4-butanediamine, 1,6-hexanediamine, 1,8-octanediamine, aniline and melamine, such as 1,6-hexanediamine, 1,8-octanediamine, melamine or N-methylimidazole.

[0020] In step (1), the molar ratio of the phenolic compound to the amine compound can be 1:(0.2-2), for example 1:0.25, 1:0.30, 1:0.50, 1:0.75, or 1:1.25.

[0021] In step (1), the mixture may also include phosphorus-containing compounds.

[0022] The phosphorus-containing compound may be selected from one or more of phosphorus pentoxide, phosphoric acid, sodium dihydrogen phosphate, sodium phosphate, potassium phosphate, ammonium phosphate, and ammonium dihydrogen phosphate, such as sodium phosphate or ammonium phosphate.

[0023] The amount of phosphorus-containing compound added can be 0-8 wt% of the resin solution mass, preferably 0-4 wt%, for example 0.5 wt%, 1.5 wt%, or 2.5 wt%.

[0024] In step (1), the mixture may not contain a water-soluble polymer. The water-soluble polymer may be one or more of polyvinyl alcohol, polyethylene glycol, and polyvinyl butyral.

[0025] In step (1), preferably, the mixture is prepared by the following steps: dissolving the phenolic compound in a solvent to obtain solution A; adding the aldehyde compound and the amine compound to solution A, stirring and heating.

[0026] The solvent may be selected from one or more of water, ethanol and toluene, such as water.

[0027] The mass ratio of the phenolic compound to the solvent can be 1:(10-100), for example 1:60, 1:15, 1:35, 1:40, 1:45 or 1:50.

[0028] The temperature of solution A can be 30-50℃, for example, 30℃, 40℃, 45℃ or 50℃.

[0029] The stirring speed can be 20-150 rpm, preferably 30-140 rpm, such as 35 rpm, 70 rpm, 100 rpm, 120 rpm, 130 rpm or 140 rpm.

[0030] The stirring time can be 1-4 hours, for example, 1 hour, 2 hours, 3 hours or 4 hours.

[0031] The agitator used for stirring can be a slanted blade impeller, a three-bladed blade impeller, or a four-bladed open turbine, preferably a four-bladed open turbine. The agitator can have a single layer, two layers, or three layers, preferably two layers.

[0032] The heating temperature can be 30-90℃, preferably 70-90℃, such as 75℃, 78℃, 80℃, 85℃ or 90℃.

[0033] The heating isothermal time can be 2-24 hours, preferably 4-10 hours, such as 1 hour, 2 hours, 3 hours or 4 hours.

[0034] The heating can be achieved by electric heating, steam heating, or hot water heating; preferably, hot water heating is used.

[0035] The phosphorus-containing compound may also be added to solution A.

[0036] In step (1), the solid content of the resin solution can be 2-40 wt%, preferably 3-15 wt%, for example 3.3 wt%, 3.4 wt%, 3.5 wt%, 4 wt%, 5 wt%, 5.6 wt%, 7.7 wt%, 10 wt%, or 11.8 wt%. The solid content in this invention can be the percentage by mass of the resin solution remaining after drying under specified conditions, as commonly understood in the art.

[0037] In step (2), the spray drying equipment can be conventional in the art, such as pressure spray drying, centrifugal spray drying, or airflow spray drying, preferably centrifugal spray drying. Spray drying can complete mixing, granulation, and drying operations in one step, greatly simplifying the production process and shortening the drying time. It eliminates the need for additional pulverization and drying, thereby reducing production steps, simplifying the production process, and avoiding the drawbacks of cumbersome and long-cycle processes in existing preparation processes. Within a certain range, operating conditions can be changed for adjustment, offering advantages such as simple preparation process and strong operability, and meeting the requirements of large-scale industrial production.

[0038] The inlet temperature of the spray dryer can be 110-350℃, preferably 120-250℃, such as 120℃, 170℃, 200℃, 210℃, or 240℃.

[0039] The outlet temperature of the spray dryer can be 70-150℃, preferably 80-150℃, such as 80℃, 90℃, 100℃, 120℃ or 150℃.

[0040] The feed flow rate of the spray dryer can be 500-1500 mL / h, preferably 800-1200 mL / h, such as 700 mL / h, 750 mL / h, 800 mL / h, 900 mL / h or 950 mL / h.

[0041] The compressed air intake pressure for spray drying can be 0.1-1.0 MPa, preferably 0.3-0.8 MPa, such as 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.75 MPa or 0.8 MPa.

[0042] When the spray drying is carried out using centrifugal spray drying, the atomizer speed can be 5000-25000 rpm, preferably 10000-20000 rpm, such as 12000 rpm, 14000 rpm, 15000 rpm, 17000 rpm, 18000 rpm or 20000 rpm.

[0043] In step (2), the carbonization employs low-temperature pre-carbonization and high-temperature carbonization, corresponding to the first carbonization and the second carbonization, respectively. The first carbonization helps the resin powder formed by spray drying to be further cured by heat, strengthens the crosslinking density between resin molecular chain segments, forms a three-dimensional crosslinked network structure, and thus improves the structural stability of the hard carbon material after the second carbonization, thereby enhancing its electrochemical performance as a negative electrode material.

[0044] In step (2), the temperature of the first carbonization can be 400-700℃, for example 400℃, 500℃, 600℃, 650℃ or 700℃.

[0045] In step (2), the isothermal time for the first carbonization can be 1-5 hours, for example, 1 hour, 2 hours, 3 hours or 4 hours.

[0046] In step (2), the temperature of the second carbonization can be 1200-1500℃, for example 1200℃, 1300℃, 1400℃ or 1500℃.

[0047] In step (2), the isothermal time for the second carbonization can be 1-4 hours, for example 2 hours, 3 hours or 4 hours.

[0048] In step (2), the heating rate of carbonization can be 1-10℃ / min, preferably 2℃ / min, 3℃ / min or 5℃ / min.

[0049] The first carbonization and the second carbonization can use different heating rates. For example, the heating rate of the first carbonization is 5℃ / min, and the heating rate of the second carbonization is 2℃ / min.

[0050] In the first and second carbonization processes, different heating rates can be used. For example, in the second carbonization process, the temperature is first raised to 700°C at a heating rate of 5°C / min, and then raised to 1400°C at a heating rate of 3°C / min.

[0051] In step (2), the carbonization can be carried out under an inert atmosphere.

[0052] The inert atmosphere can be argon or nitrogen, such as nitrogen.

[0053] In step (2), the carbonization can be carried out by vacuum carbonization or atmospheric pressure carbonization.

[0054] The vacuum carbonization operation can be conventional in the art. The vacuum degree of the vacuum carbonization can be 1-1000 Pa, preferably 10-100 Pa, for example 20 Pa.

[0055] In step (2), the carbonization equipment can be conventional in the art, such as pit furnace, rotary kiln, tube furnace, box furnace, vacuum furnace or roller kiln.

[0056] The present invention also provides a hard carbon anode material, which is prepared by the above-described preparation method.

[0057] In this invention, the hard carbon anode material has a spherical structure in its microstructure. The diameter of the spherical structure can be 1-50 μm, preferably 1-10 μm, for example, 3 μm. The diameter of the spherical structure refers to the diameter of the microspheres in the microstructure of the hard carbon anode material. The size of the microspheres varies to some extent, for example, the diameter range is 1-50 μm.

[0058] In this invention, the specific surface area of ​​the hard carbon anode material can be 1-40 m². 2 / g, preferably 2-10m 2 / g, for example 2.2m 2 / g, 2.3m 2 / g, 2.8m 2 / g, 3.0m 2 / g, 3.1m 2 / g, 3.2m 2 / g or 7.5m 2 / g.

[0059] In this invention, the hard carbon anode material has a rich microporous structure, and the micropore diameter can be 0.3-1.5 nm, preferably 0.4-1.0 nm, for example 0.53 nm or 0.88 nm.

[0060] In this invention, the median particle size D50 of the hard carbon anode material can be 3-15 μm, preferably 3-8 μm, such as 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.3 μm, 4.7 μm or 4.8 μm.

[0061] In this invention, the tap density of the hard carbon anode material can be 0.5-0.9 g / cm³. 3 The preferred value is 0.70-0.85 g / cm³. 3 For example, 0.75g / cm 3 0.76 g / cm 3 0.77g / cm 3 0.79g / cm 3 or 0.80g / cm 3 .

[0062] The present invention also provides an application of the above-mentioned hard carbon anode material in sodium-ion batteries.

[0063] The present invention also provides a sodium-ion battery comprising the aforementioned hard carbon anode material.

[0064] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0065] The reagents and raw materials used in this invention are all commercially available.

[0066] The positive and progressive effects of this invention are as follows:

[0067] 1. This invention uses phenolic compounds, aldehyde compounds, and amine compounds as raw materials. Based on the Mannich reaction, it can synthesize resin prepolymer monomers with different structures and properties. During polymerization, there is no small molecule precipitation, minimal volume shrinkage, and no need to add strong acids or bases as curing agents during curing. Simultaneously, nitrogen-containing functional groups can be introduced into the product skeleton in situ through the reaction. After subsequent spray drying molding, heat treatment carbonization, and other steps, a hard carbon material with excellent thermal stability and a nitrogen-rich skeleton can be obtained. This invention achieves precise control over the microstructure morphology and size of resin polymer microspheres and resin-based microsphere hard carbon materials by adjusting the reaction feed ratio of phenolic, aldehyde, and amine compounds and other process parameters.

[0068] 2. The preparation method of the present invention avoids the drawbacks of the existing preparation process being cumbersome and having a long process cycle, and has the advantages of simple preparation process and strong operability.

[0069] 3. The hard carbon material prepared by this invention has a microsphere structure, which is beneficial for achieving its close packing and improving the volumetric energy density of the electrode. Compared with hard carbon materials with irregular microstructures, it has advantages such as high volumetric energy density and excellent rate performance. On the other hand, it is beneficial for sodium ions to be inserted from all directions, shortening their transport path and improving the structural stability and rate performance of the negative electrode material.

[0070] 4. Furthermore, this invention introduces heteroatoms such as nitrogen and phosphorus through in-situ reactions. This doping can create more defects and active sites for hard carbon, enhancing its electronic conductivity. Simultaneously, the dual heteroatom co-doping enables the hard carbon material to exhibit better Na+ performance than single-doped materials. + Storage capacity can be improved by inducing more defects on the carbon surface and by increasing the interlayer spacing and acting as an active center. The synergistic effect of these two factors is clearly beneficial to improving electrochemical performance. Attached Figure Description

[0071] Figure 1This is a pore size distribution diagram of the hard carbon anode material prepared in Example 1.

[0072] Figure 2 This is a morphology diagram of the hard carbon anode material prepared in Example 1. Detailed Implementation

[0073] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0074] Example 1

[0075] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 30°C, add a certain amount of resorcinol into the reactor through negative pressure conveying according to the mass ratio of phenolic compound to water of 1:50. Start stirring to fully dissolve it. During this process, the speed is maintained at 120 rpm. Then add formaldehyde solution with a mass fraction of 37 wt% according to the molar ratio of phenolic compound to aldehyde compound of 1:2. Continue stirring to mix it evenly with the phenolic compound solution.

[0076] (2) Add 1,6-hexanediamine solution to the solution in step (1) according to the molar ratio of phenolic compound to amine compound of 1:0.25. After stirring at a constant temperature for 2 hours, raise the reaction temperature to 85°C and react at a constant temperature for 4 hours to obtain a resin solution with a solid content of 3.5 wt%.

[0077] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 170℃, outlet temperature parameter to 90℃, inlet air pressure to 0.5MPa, and atomizer speed to 15000rpm, the feed pump flow rate is adjusted to 700mL / h, and resin powder is obtained after cyclone separation.

[0078] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, and under nitrogen protection, raise the temperature to 600°C at a rate of 3°C / min and keep it at that temperature for 2 hours to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0079] (5) The resin pre-carbonized material obtained in step (4) is placed in an atmospheric pressure carbonization furnace. Under nitrogen protection, the temperature is raised to 1300℃ at a rate of 3℃ / min and held for 2 hours for high-temperature carbonization. After naturally cooling to room temperature, the resin-based microsphere hard carbon anode material is discharged.

[0080] Example 2

[0081] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 40°C, add a certain amount of resorcinol into the reactor through negative pressure conveying according to the mass ratio of phenolic compound to water of 1:40. Start stirring to fully dissolve it. During this process, the speed is maintained at 140 rpm. Then add formaldehyde solution with a mass fraction of 37 wt% according to the molar ratio of phenolic compound to aldehyde compound of 1:1.5. Continue stirring to mix it evenly with the phenolic compound solution.

[0082] (2) Add 1,8-octanediamine solution to the solution in step (1) according to the molar ratio of phenolic compound to amine compound of 1:0.75. After stirring at a constant temperature for 3 hours, raise the reaction temperature to 90°C and react at a constant temperature for 8 hours to obtain a resin solution with a solid content of 5.6 wt%.

[0083] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 200℃, the outlet temperature parameter to 90℃, the inlet air pressure to 0.7MPa, and the atomizer speed to 12000rpm, the feed pump flow rate is adjusted to 800mL / h, and the resin powder is obtained after cyclone separation.

[0084] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, and under nitrogen protection, raise the temperature to 700°C at a heating rate of 2°C / min and keep it at that temperature for 3 hours to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0085] (5) The resin pre-carbonized material obtained in step (4) is placed in an atmospheric pressure carbonization furnace. Under nitrogen protection, the temperature is raised to 1400℃ at a rate of 2℃ / min and held for 3 hours for high-temperature carbonization. After naturally cooling to room temperature, the resin-based microsphere hard carbon anode material is discharged.

[0086] Example 3

[0087] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 45°C, add a certain amount of phenol into the reactor through positive pressure conveying according to the mass ratio of phenolic compound to water of 1:15. Start stirring to fully dissolve it. During this process, the speed is maintained at 100 rpm. Then add a formaldehyde solution with a mass fraction of 37 wt% according to the molar ratio of phenolic compound to aldehyde compound of 1:1.35. Continue stirring to mix it evenly with the phenolic compound solution.

[0088] (2) Melamine was added to the solution in step (1) at a molar ratio of phenolic compound to amine compound of 1:0.5. After stirring at a constant temperature for 1 hour, the reaction temperature was raised to 75°C and reacted at a constant temperature for 6 hours to obtain a resin solution with a solid content of 11.8 wt%.

[0089] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 120℃, the outlet temperature parameter to 80℃, the inlet air pressure to 0.75MPa, and the atomizer speed to 18000rpm, the feed pump flow rate is adjusted to 750mL / h, and the resin powder is obtained after cyclone separation.

[0090] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, and under nitrogen protection, raise the temperature to 500°C at a rate of 5°C / min and keep it at that temperature for 4 hours to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0091] (5) Place the resin pre-carbonized material obtained in step (4) in a vacuum carbonization furnace, maintain the vacuum degree at 20 Pa, and under nitrogen protection, raise the temperature to 1500℃ at a heating rate of 2℃ / min and keep it at the temperature for 2 hours for high-temperature carbonization. After naturally cooling to room temperature, the material is discharged to obtain resin-based microsphere hard carbon anode material.

[0092] Example 4

[0093] (1) Add an alcoholic solution to the reactor as a solvent. When the temperature inside the reactor stabilizes at about 50°C, add a certain amount of phenol to the reactor through a screw conveyor at a mass ratio of phenolic compound to water of 1:60. Start stirring to dissolve it completely. During this process, the stirring speed is maintained at 120 rpm. Then add a furfural solution with a mass fraction of 37 wt% at a molar ratio of phenolic compound to aldehyde compound of 1:1.15. Continue stirring to mix it evenly with the phenolic compound solution.

[0094] (2) Add N-methylimidazole to the solution in step (1) according to the molar ratio of phenolic compound to amine compound of 1:0.30. After stirring at a constant temperature for 4 hours, raise the reaction temperature to 80°C and react at a constant temperature for 5 hours to obtain a resin solution with a solid content of 4wt%.

[0095] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 210℃, the outlet temperature parameter to 120℃, the inlet air pressure to 0.6MPa, and the atomizer speed to 15000rpm, the feed pump flow rate is adjusted to 950mL / h, and the resin powder is obtained after cyclone separation.

[0096] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, raise the temperature to 400°C at a rate of 3°C / min under nitrogen protection and keep it at that temperature for 1 hour to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0097] (5) The resin pre-carbonized material obtained in step (4) is placed in an atmospheric pressure carbonization furnace. Under nitrogen protection, the temperature is raised to 1200℃ at a rate of 3℃ / min and held for 4 hours for high-temperature carbonization. After naturally cooling to room temperature, the resin-based microsphere hard carbon anode material is discharged.

[0098] Example 5

[0099] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 45°C, add a certain amount of xylenol into the reactor through negative pressure conveying according to the mass ratio of phenolic compound to water of 1:35. Start stirring to fully dissolve it. During this process, the speed is maintained at 130 rpm. Then add glutaraldehyde solution with a mass fraction of 25 wt% according to the molar ratio of phenolic compound to aldehyde compound of 1:1.2. Continue stirring to mix it evenly with the phenolic compound solution.

[0100] (2) Add 1,6-hexanediamine solution to the solution in step (1) according to the molar ratio of phenolic compound to amine compound of 1:1.25. After stirring at a constant temperature for 2 hours, raise the reaction temperature to 85°C and react at a constant temperature for 7 hours to obtain a resin solution with a solid content of 7.7 wt%.

[0101] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 240℃, the outlet temperature parameter to 150℃, the inlet air pressure to 0.7MPa, and the atomizer speed to 17000rpm, the feed pump flow rate is adjusted to 900mL / h, and the resin powder is obtained after cyclone separation.

[0102] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, raise the temperature to 650°C at a rate of 3°C / min under nitrogen protection and keep it at that temperature for 2 hours to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0103] (5) The resin pre-carbonized material obtained in step (4) is placed in an atmospheric pressure carbonization furnace. Under nitrogen protection, the temperature is raised to 700°C at a rate of 5°C / min, and then raised to 1400°C at a rate of 3°C / min and held for 3 hours for high-temperature carbonization. After naturally cooling to room temperature, the resin-based microsphere hard carbon anode material is discharged.

[0104] Example 6

[0105] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 30°C, add a certain amount of resorcinol into the reactor through negative pressure according to the mass ratio of phenolic compound to water of 1:50. Start stirring to fully dissolve it. During this process, the speed is maintained at 120 rpm. Then add a formaldehyde solution with a mass fraction of 37 wt% according to the molar ratio of phenolic compound to aldehyde compound of 1:2. Continue stirring to mix it evenly with the phenolic compound solution.

[0106] (2) Add 1,6-hexanediamine solution to the solution in step (1) according to the molar ratio of phenolic compound to amine compound of 1:0.25, stir, and then add 2.5 wt% of ammonium phosphate of the above solution. After stirring at a constant temperature for 2 hours, raise the reaction temperature to 85°C and react at a constant temperature for 4 hours to obtain a resin solution with a solid content of 3.4 wt%.

[0107] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 170℃, the outlet temperature parameter to 90℃, the inlet air pressure to 0.8MPa, and the atomizer speed to 20000rpm, the feed pump flow rate is adjusted to 700mL / h, and the resin powder is obtained after cyclone separation.

[0108] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, and under nitrogen protection, raise the temperature to 600°C at a rate of 3°C / min and keep it at that temperature for 2 hours to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0109] (5) Place the resin pre-carbonized material obtained in step (4) in a vacuum carbonization furnace, maintain the vacuum at 20 Pa, and under nitrogen protection, raise the temperature to 1300°C at a heating rate of 3°C / min and hold for 2 hours for high-temperature carbonization. After naturally cooling to room temperature, discharge the material to obtain resin-based microsphere hard carbon anode material.

[0110] Example 7

[0111] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 30°C, add a certain amount of resorcinol into the reactor through negative pressure conveying according to the mass ratio of phenolic compound to water of 1:45. Start stirring to fully dissolve it. During this process, the speed is maintained at 120 rpm. Then add a formaldehyde solution with a mass fraction of 37 wt% according to the molar ratio of phenolic compound to aldehyde compound of 1:1.25. Continue stirring to mix it evenly with the phenolic compound solution.

[0112] (2) Add 1,6-hexanediamine solution to the solution in step (1) according to the molar ratio of phenolic compound to amine compound of 1:0.25, stir, and then add sodium phosphate of 1.5 wt% of the above solution. After stirring at a constant temperature for 2 hours, raise the reaction temperature to 78°C and react at a constant temperature for 5 hours to obtain a resin solution with a solid content of 3.4 wt%.

[0113] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 200℃, the outlet temperature parameter to 100℃, the air pressure to 0.7MPa, and the atomizer speed to 14000rpm, the feed pump flow rate is adjusted to 950mL / h, and the resin powder is obtained after cyclone separation.

[0114] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, raise the temperature to 600°C at a rate of 2°C / min under nitrogen protection and keep it at that temperature for 2 hours to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0115] (5) The resin pre-carbonized material obtained in step (4) is placed in an atmospheric pressure carbonization furnace. Under nitrogen protection, the temperature is raised to 1300℃ at a rate of 2℃ / min and held for 2 hours for high-temperature carbonization. After naturally cooling to room temperature, the resin-based microsphere hard carbon anode material is discharged.

[0116] Comparative Example 1

[0117] The difference between this comparative example and Example 1 is that no amine compound was added in step (2).

[0118] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 30°C, add a certain amount of resorcinol into the reactor through negative pressure conveying according to the mass ratio of phenolic compound to water of 1:50. Start stirring to fully dissolve it. During this process, the speed is maintained at 120 rpm. Then add formaldehyde solution with a mass fraction of 37 wt% according to the molar ratio of phenolic compound to aldehyde compound of 1:2. Continue stirring to mix it evenly with the phenolic compound solution.

[0119] (2) After raising the reaction temperature of step (1) to 85°C and reacting at a constant temperature for 4 hours, a resin solution with a solid content of 4.7 wt% can be obtained.

[0120] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 170℃, outlet temperature parameter to 90℃, inlet air pressure to 0.5MPa, and atomizer speed to 15000rpm, the feed pump flow rate is adjusted to 700mL / h, and resin powder is obtained after cyclone separation.

[0121] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, and under nitrogen protection, raise the temperature to 600°C at a rate of 3°C / min and keep it at that temperature for 2 hours to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0122] (5) The resin pre-carbonized material obtained in step (4) is placed in an atmospheric pressure carbonization furnace. Under nitrogen protection, the temperature is raised to 1300℃ at a rate of 3℃ / min and held for 2 hours for high-temperature carbonization. After naturally cooling to room temperature, the resin-based microsphere hard carbon anode material is discharged.

[0123] Comparative Example 2

[0124] The difference between this comparative example and Example 1 is that in step (4), low-temperature pre-carbonization was not performed, but high-temperature carbonization was performed directly.

[0125] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 30°C, add a certain amount of resorcinol into the reactor through negative pressure conveying at a mass ratio of phenolic compound to water of 1:50. Start stirring to fully dissolve it. During this process, the speed is maintained at 120 rpm. Then add a formaldehyde solution with a mass fraction of 37 wt% at a molar ratio of phenolic compound to aldehyde compound of 1:2. Continue stirring to mix it evenly with the phenolic compound solution.

[0126] (2) Add 1,6-hexanediamine solution to the solution in step (1) according to the molar ratio of phenolic compound to amine compound of 1:0.25. After stirring at a constant temperature for 2 hours, raise the reaction temperature to 85°C and react at a constant temperature for 4 hours to obtain a resin solution with a solid content of 3.5 wt%.

[0127] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 170℃, outlet temperature parameter to 90℃, inlet air pressure to 0.5MPa, and atomizer speed to 15000rpm, the feed pump flow rate is adjusted to 700mL / h, and resin powder is obtained after cyclone separation.

[0128] (4) The resin pre-carbonized material obtained in step (3) is placed in an atmospheric pressure carbonization furnace. Under nitrogen protection, the temperature is raised to 1300℃ at a rate of 3℃ / min and held for 2 hours for high-temperature carbonization. After naturally cooling to room temperature, the resin-based microsphere hard carbon anode material is discharged.

[0129] Comparative Example 3

[0130] The difference between this comparative example and Example 1 is the change in the molar ratio of phenolic compounds and aldehyde compounds in step (1).

[0131] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 30°C, add a certain amount of resorcinol into the reactor through negative pressure conveying according to the mass ratio of phenolic compound to water of 1:50. Start stirring to fully dissolve it. During this process, the speed is maintained at 120 rpm. Then add formaldehyde solution with a mass fraction of 37 wt% according to the molar ratio of phenolic compound to aldehyde compound of 1:0.85. Continue stirring to mix it evenly with the phenolic compound solution.

[0132] (2) Add 1,6-hexanediamine solution to the solution in step (1) according to the molar ratio of phenolic compound to amine compound of 1:0.25. After stirring at a constant temperature for 2 hours, raise the reaction temperature to 85°C and react at a constant temperature for 4 hours to obtain a resin solution with a solid content of 2.9 wt%.

[0133] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 170℃, outlet temperature parameter to 90℃, inlet air pressure to 0.5MPa, and atomizer speed to 15000rpm, the feed pump flow rate is adjusted to 700mL / h, and resin powder is obtained after cyclone separation.

[0134] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, and under nitrogen protection, raise the temperature to 600°C at a rate of 3°C / min and keep it at that temperature for 2 hours to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0135] (5) The resin pre-carbonized material obtained in step (4) is placed in an atmospheric pressure carbonization furnace. Under nitrogen protection, the temperature is raised to 1300℃ at a rate of 3℃ / min and held for 2 hours for high-temperature carbonization. After naturally cooling to room temperature, the resin-based microsphere hard carbon anode material is discharged.

[0136] Comparative Example 4

[0137] The difference between this comparative example and Example 1 is the change in the amount of amine compound added in step (2).

[0138] (1) Add water as a solvent to the reactor. When the temperature inside the reactor stabilizes at about 30°C, add a certain amount of resorcinol into the reactor through negative pressure conveying according to the mass ratio of phenolic compound to water of 1:50. Start stirring to fully dissolve it. During this process, the speed is maintained at 120 rpm. Then add formaldehyde solution with a mass fraction of 37 wt% according to the molar ratio of phenolic compound to aldehyde compound of 1:2. Continue stirring to mix it evenly with the phenolic compound solution.

[0139] (2) Add 1,6-hexanediamine solution to the solution in step (1) according to the molar ratio of phenolic compound to amine compound of 1:0.1. After stirring at a constant temperature for 2 hours, raise the reaction temperature to 85°C and react at a constant temperature for 4 hours to obtain a resin solution with a solid content of 2.5 wt%.

[0140] (3) The resin aqueous solution obtained in step (2) is spray dried, desolventized and solidified by centrifugal spray drying. Under the conditions of setting the equipment inlet temperature parameter to 170℃, outlet temperature parameter to 90℃, inlet air pressure to 0.5MPa, and atomizer speed to 15000rpm, the feed pump flow rate is adjusted to 700mL / h, and resin powder is obtained after cyclone separation.

[0141] (4) Place the resin powder obtained in step (3) in an atmospheric pressure carbonization furnace, and under nitrogen protection, raise the temperature to 600°C at a rate of 3°C / min and keep it at that temperature for 2 hours to carry out low-temperature pre-carbonization. After it cools down to room temperature naturally, the resin pre-carbonized product is discharged.

[0142] (5) The resin pre-carbonized material obtained in step (4) is placed in an atmospheric pressure carbonization furnace. Under nitrogen protection, the temperature is raised to 1300℃ at a rate of 3℃ / min and held for 2 hours for high-temperature carbonization. After naturally cooling to room temperature, the resin-based microsphere hard carbon anode material is discharged.

[0143] Example 1

[0144] Specific surface area and pore structure characterization: Specific surface area and pore structure were measured using a fully automated adsorption-desorption instrument (McCloneze), USA. Nitrogen gas was used as the adsorbate for specific surface area testing at 77 K, and the result was calculated using the BET method. Carbon dioxide was used as the adsorbate for micropore size testing at 273 K, and the result was obtained through DFT model analysis. The relevant test results are shown in Table 1, where the pore structure distribution diagram of Example 1 is shown below. Figure 1 As shown in the pore size distribution diagram, the resin-based microsphere hard carbon material is mainly composed of ultramicropores of 0.53 nm. This type of pore structure is beneficial for improving the specific capacity of sodium batteries.

[0145] Example 2

[0146] 1. Material Morphology Characterization: SEM images of the hard carbon material were obtained using a ZEISS scanning electron microscope. The SEM image of the hard carbon material prepared in Example 1 is shown below. Figure 2 As shown. By Figure 2 It is known that the resin-based hard carbon of the present invention has a spherical structure with a regular shape and a microsphere diameter of about 3 μm.

[0147] 2. The median particle size D50 of the hard carbon material was measured using Mastersize 2000 (Malvin 2000), and the results are shown in Table 1.

[0148] Example 3

[0149] Electrochemical performance testing:

[0150] The hard carbon anode materials prepared in Examples 1-7 and Comparative Examples 1-4 were weighed, ground, and mixed according to a mass ratio of anode material to conductive agent and binder of 90:5:5. Using NMP as a solvent, a viscous, homogeneous slurry was prepared. This slurry was then coated onto copper foil using a scraping method. The coated copper foil was then dried in a vacuum oven at 80°C for 12 hours. The dried copper foil was then cut into pieces with an area of ​​2 cm². 2 The working electrode was made from a circular sheet. At room temperature, a sodium metal sheet was used as the negative electrode and the counter electrode, the electrode sheet prepared above was used as the working electrode, a Celgard 2400 polypropylene porous membrane was used as the separator, and a 1 mol / L NaPF6 / EC+DMC solution (volume ratio of 1:1) was used as the electrolyte. The cells were assembled into a CR2032 button cell in a vacuum glove box and then tightly mechanically sealed.

[0151] After the assembled batteries were allowed to stand at room temperature for 24 hours, electrochemical testing was started. Constant current charge-discharge experiments were conducted on the LAND battery testing system with a charge-discharge voltage window of 0-2.0V and a charge-discharge rate of 0.1C. The discharge capacity and initial discharge efficiency were measured according to conventional testing methods in the field. The test results are shown in Table 1.

[0152] Table 1. Performance data of hard carbon anode materials obtained from each embodiment and comparative example.

[0153]

[0154] As can be seen from the results in Table 1, the sodium-ion battery made with resin-based hard carbon as the negative electrode material prepared in the embodiments of the present invention has higher capacity and first-time efficiency, and its electrochemical performance is significantly better than that of the comparative example.

[0155] A comparison of the results of Example 1 and Example 6 revealed that when nitrogen and phosphorus heteroatoms were introduced simultaneously during the synthesis process, the heteroatoms induced more defects on the carbon surface, increased the interlayer spacing, and acted as active centers. The synergistic effect of the two further improved the electrochemical performance.

[0156] By comparing the results of Examples 1-7 with those of Comparative Examples 1 and 4, it is easy to see that the addition of amine compounds and the appropriate increase in the amount of amine compounds are beneficial to improving the performance of the product. On the one hand, the introduction of nitrogen heteroatoms can improve the conductivity of the material by accelerating the diffusion of ions and electrons, and can also generate additional defects and reactive sites, thereby improving the sodium storage capacity of the material. On the other hand, amine compounds play a catalytic role in the reaction process of phenolic system.

[0157] A comparison of the results of Examples 1-7 with Comparative Example 3 revealed that changing the phenol-formaldehyde reaction ratio has a significant impact on product performance. This is mainly because when the ratio of phenol and formaldehyde is changed, the corresponding reaction process is also altered, resulting in different properties in the microstructure of the material.

[0158] Furthermore, by comparing the results of Example 1 with those of Comparative Example 2, it can be found that it is meaningful to carry out heat treatment carbonization in two stages. Low-temperature pre-carbonization helps the resin powder formed by spray drying to be further cured by heat, strengthens the cross-linking density between resin molecular chain segments, forms a three-dimensional cross-linked network structure, and thus improves the structural stability of the hard carbon material after high-temperature carbonization, thereby improving its electrochemical performance as a negative electrode material.

Claims

1. A method for preparing a hard carbon anode material, characterized in that, It includes the following steps: (1) A resin solution is prepared by heat treatment of a mixture of phenolic compounds, aldehyde compounds and amine compounds; wherein the amine compounds are one or more of 1,6-hexanediamine, 1,8-octanediamine, melamine and N-methylimidazole; the molar ratio of the phenolic compounds to the aldehyde compounds is 1:(1-3); the molar ratio of the phenolic compounds to the amine compounds is 1:(0.2-3); The mixture does not contain any water-soluble polymers; the water-soluble polymers are one or more of polyvinyl alcohol, polyethylene glycol, and polyvinyl butyral. (2) The resin solution is spray-dried and carbonized to obtain a hard carbon anode material; the carbonization includes a first carbonization and a second carbonization; The temperature of the first carbonization is 400-700℃; The second carbonization temperature is 1200-1500℃.

2. The method for preparing the hard carbon anode material as described in claim 1, characterized in that, In step (1), the phenolic compound is selected from one or more of phenol, bisphenol A, resorcinol and xylenol; And / or, in step (1), the aldehyde compound is selected from one or more of formaldehyde, furfural, glutaraldehyde, metaldehyde and benzaldehyde; And / or, in step (1), the molar ratio of the phenolic compound to the aldehyde compound is 1:(1-2); And / or, in step (1), the amine compound is 1,6-hexanediamine, 1,8-octanediamine, melamine or N-methylimidazole; And / or, in step (1), the molar ratio of the phenolic compound to the amine compound is 1:(0.2-2); In step (1), the solid content of the resin solution is 2-40 wt%.

3. The method for preparing the hard carbon anode material as described in claim 1, characterized in that, In step (1), the phenolic compound is resorcinol, phenol, or xylenol; And / or, in step (1), the aldehyde compound is formaldehyde, furfural, or glutaraldehyde; the formaldehyde or furfural is prepared as a 37 wt% solution; the glutaraldehyde is prepared as a 25 wt% solution. And / or, in step (1), the solid content of the resin solution is 3-15 wt%.

4. The method for preparing the hard carbon anode material as described in claim 1, characterized in that, The aldehyde compound is a 37wt% formaldehyde solution, a 37wt% furfural solution, or a 25wt% glutaraldehyde solution.

5. The method for preparing the hard carbon anode material as described in claim 1, characterized in that, In step (1), the mixture also includes a phosphorus-containing compound; And / or, in step (1), the mixture is prepared by the following steps: dissolving the phenolic compound in a solvent to obtain solution A; adding the aldehyde compound and the amine compound to solution A, stirring and heating.

6. The method for preparing the hard carbon anode material as described in claim 5, characterized in that, In step (1), the mixture further includes a phosphorus-containing compound selected from one or more of phosphorus pentoxide, phosphoric acid, sodium dihydrogen phosphate, sodium phosphate, potassium phosphate, ammonium phosphate, and ammonium dihydrogen phosphate; And / or, in step (1), the mixture further includes a phosphorus-containing compound, the amount of which is 0.5-8 wt% of the mass of the resin solution.

7. The method for preparing the hard carbon anode material as described in claim 6, characterized in that, The phosphorus-containing compound is sodium phosphate or ammonium phosphate; And / or, the amount of the phosphorus-containing compound added is 0.5-4 wt% of the mass of the resin solution.

8. The method for preparing the hard carbon anode material as described in claim 5, characterized in that, The solvent is selected from one or more of water, ethanol, and toluene; And / or, the mass ratio of the phenolic compound to the solvent is 1:(10-100); And / or, the temperature of solution A is 30-50°C; And / or, the stirring speed is 20-150 rpm; And / or, the stirring time is 1-4 hours; And / or, the heating temperature is 30-90°C; And / or, the heating isothermal time is 2-24 hours; And / or, the phosphorus-containing compound is added to solution A.

9. The method for preparing the hard carbon anode material as described in claim 8, characterized in that, The solvent is water; And / or, the stirring speed is 30-140 rpm; And / or, the heating temperature is 70-90°C; And / or, the heating isothermal time is 4-10 hours.

10. The method for preparing the hard carbon anode material as described in claim 1, characterized in that, In step (2), the inlet temperature of the spray dryer is 110-350℃; And / or, the outlet temperature of the spray dryer is 70-150°C; And / or, the feed flow rate of the spray dryer is 500-1500 mL / h; And / or, the compressed air inlet pressure for the spray drying is 0.1-1.0 MPa; And / or, when the spray drying is carried out using centrifugal spray drying, the atomizer speed is 5000-25000 rpm.

11. The method for preparing the hard carbon anode material as described in claim 10, characterized in that, In step (2), the inlet temperature of the spray dryer is 120-250℃; And / or, the outlet temperature of the spray dryer is 80-150°C; And / or, the feed flow rate of the spray dryer is 800-1200 mL / h; And / or, the compressed air inlet pressure for the spray drying is 0.3-0.8 MPa; And / or, when the spray drying is carried out using centrifugal spray drying, the atomizer speed is 10000-20000 rpm.

12. The method for preparing the hard carbon anode material as described in claim 1, characterized in that, In step (2), the isothermal time for the first carbonization is 1-5 hours; And / or, in step (2), the isothermal time for the second carbonization is 1-4 hours; And / or, in step (2), the heating rate of carbonization is 1-10℃ / min; And / or, in step (2), the carbonization is carried out under an inert atmosphere; the inert atmosphere is argon or nitrogen; And / or, in step (2), the carbonization is carried out by vacuum carbonization or atmospheric pressure carbonization; the vacuum degree of the vacuum carbonization is 1-1000 Pa.

13. The method for preparing the hard carbon anode material as described in claim 12, characterized in that, In step (2), the carbonization is carried out under an inert atmosphere, which is nitrogen. And / or, in step (2), the carbonization is carried out by vacuum carbonization or atmospheric pressure carbonization; the vacuum degree of the vacuum carbonization is 10-100 Pa.

14. A hard carbon anode material, characterized in that, It is prepared by any one of the preparation methods as described in claims 1-13.

15. The hard carbon anode material as described in claim 14, characterized in that, The hard carbon anode material has a spherical structure with a diameter of 1-50 μm. And / or, the specific surface area of ​​the hard carbon anode material is 1-40 m². 2 / g; And / or, the micropore size of the hard carbon anode material is 0.3-1.5 nm; And / or, the median particle size D50 of the hard carbon anode material is 3-15 μm; And / or, the tap density of the hard carbon anode material is 0.5-0.9 g / cm³. 3 .

16. The hard carbon anode material as described in claim 15, characterized in that, The hard carbon anode material has a spherical structure with a diameter of 1-10 μm. And / or, the specific surface area of ​​the hard carbon anode material is 2-10 m². 2 / g; And / or, the micropore size of the hard carbon anode material is 0.4-1.0 nm; And / or, the median particle size D50 of the hard carbon anode material is 3-8 μm; And / or, the tap density of the hard carbon anode material is 0.70-0.85 g / cm³. 3 .

17. The application of a hard carbon anode material as described in any one of claims 14 to 16 in a battery.

18. The application of the hard carbon anode material as described in claim 17 in a battery, wherein the battery is a sodium-ion battery.

19. A sodium-ion battery, characterized in that, It includes the hard carbon anode material as described in any one of claims 14 to 16.

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