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

Abstract

The present application discloses a hard carbon material and a preparation method therefor, a negative electrode material, and a sodium ion battery. The atomic pair distribution function technology is used to deconstruct crystal information, and the hard carbon material with the lattice curvature Formula (1) being 0.03-0.15 and the closed-cell volume being 0.04-0.5 cm3·g-1 has a high closed-cell ratio, large sodium storage capacity, and excellent pore strength, is not prone to structural collapse during long-term charge and discharge processes, and has high cycle stability.

Description

A hard carbon material and preparation method thereof, negative electrode material and sodium ion battery

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on January 18, 2024, with application number CN202410075151.7 and application name “A hard carbon material and its preparation method, negative electrode material and sodium ion battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a hard carbon material and a preparation method thereof, a negative electrode material, and a sodium ion battery. Background Art

[0003] Sodium-ion batteries (SIBs) are considered a promising candidate for next-generation secondary batteries due to their abundant sodium content in the Earth's crust and their high energy density. For the anode, due to the large radius of sodium ions, only ether-solvated sodium ions can form stable intercalation compounds with traditional graphite as a SIB anode material. Furthermore, as sodium ions intercalate and deintercalate, the graphite undergoes volume expansion and contraction, leading to fragmentation of the graphite layers. This fragmentation can lead to irreversible resistance within the battery, reducing battery performance and cycle life. Compared to graphite, hard carbon materials can store desolvated sodium ions and exhibit improved cycling stability during the intercalation and deintercalation process. Hard carbon materials can reduce sodium metal precipitation, thereby avoiding battery short circuits and safety issues, and improving battery reliability and lifespan. Furthermore, for the same volume or mass, hard carbon materials offer greater charge storage capacity, thereby increasing battery energy density and extending battery operating time. Furthermore, hard carbon materials possess high thermal stability, maintaining excellent structural stability and electrochemical performance at high temperatures. This makes hard carbon anodes promising for high-temperature applications and fast charge-discharge systems, meeting specific application requirements. Technical issues

[0004] However, existing hard carbon materials generally face the following problems:

[0005] 1. The closed porosity of hard carbon is not high: closed pores have been shown to be the main sodium storage sites for the low-voltage capacity of hard carbon. A small amount of closed pores will result in a decrease in the low-voltage capacity of hard carbon. This loss of low-voltage capacity will lead to a decrease in the energy density of the battery, affecting the battery's service life and performance;

[0006] 2. Insufficient strength of closed pores: The closed pores in hard carbon materials are mainly closed micropores or pores, which have low structural strength and are prone to structural collapse during long-term cyclic charge and discharge, thereby reducing the structural stability and cycle life of the battery material, causing capacity and voltage decay of sodium-ion batteries during long-term use, affecting the performance and reliability of the battery. Technical Solutions

[0007] The purpose of this application is to overcome the shortcomings of the prior art and provide a hard carbon material and a preparation method thereof. The hard carbon material has a high closed porosity, thereby having a high sodium storage capacity, and at the same time has good pore strength, is not prone to structural collapse during long-term charging and discharging, and has high cycle stability.

[0008] To solve the above problems, the technical solutions adopted in this application are:

[0009] Provided is a hard carbon material, wherein the lattice curvature of the hard carbon material The volume of closed cells is 0.03-0.15, and the volume of closed cells is 0.04-0.5cm 3 ·g -1 ;in For comparison, graphite The standard distance value corresponding to the position of the sixth peak in the atomic pair distribution function spectrum within the interval; The hard carbon material is The distance value corresponding to the position of the sixth peak in the atomic pair distribution function spectrum within the interval; λ is the wavelength of the silver target The atomic pair distribution function spectrum is obtained by Fourier transforming total scattering experimental data measured by a Ag target X-ray source total scattering experimental device on a target material.

[0010] In some embodiments, the raw material of the hard carbon material is one or more of a biomass derivative carbon source or a high molecular organic matter, wherein the biomass derivative carbon source is one or more of cellulose, lignin or sugars.

[0011] In some embodiments, the hard carbon material is hard carbon particles with an average particle size of 2-50 μm and a carbon interlayer spacing d002 value of 0.35-0.40 nm, which is obtained by X-ray diffraction using CuKα rays as a ray source and calculated based on the Bragg equation.

[0012] In some embodiments, the hard carbon material has an average pore size of 0.5-5 nm.

[0013] In some embodiments, the specific surface area of ​​the hard carbon material is 0.5-20 m 2 ·g -1 .

[0014] In some embodiments, the fracture strength of the hard carbon material is 14.5-22.8 kg·mm -2 The burst strength is determined by the particle-to-particle crushing test described in ASTM D 6175-3.

[0015] In some embodiments, the compacted density of the hard carbon material is 0.7-1.3 g / cm 3 .

[0016] The present application also provides a method for preparing a hard carbon material, comprising the following steps: step (1): calcining a carbon source to obtain a hard carbon precursor; step (2): mixing the hard carbon precursor with a dispersant and an activator and grinding the mixture to obtain a hard carbon precursor powder; step (3): mixing the hard carbon precursor powder with a cross-linking agent and a template, and subjecting the resulting mixture to a medium-temperature carbonization treatment in an inert atmosphere to obtain a first carbonized product; step (4): subjecting the first carbonized product to a high-temperature carbonization treatment in an inert atmosphere or a mixed atmosphere of an inert atmosphere and an organic atmosphere to obtain a second carbonized product, that is, obtaining the hard carbon material; wherein the temperature of the medium-temperature carbonization treatment is 400-900°C, and the treatment time is 1-10h; the temperature of the high-temperature carbonization treatment is 900-1700°C, and the treatment time is 1-6h.

[0017] In some embodiments, the preparation method further comprises step (5): subjecting the second carbonized product to microwave or medium frequency heating treatment in an inert atmosphere to obtain the hard carbon material.

[0018] In some embodiments, in step (1), the carbon source is calcined at a temperature of 100-350° C. and the holding time is 1-20 h.

[0019] In some embodiments, in step (2), the sieved particle size of the hard carbon precursor powder is 250-800 mesh.

[0020] In some embodiments, in step (2), the dispersant includes one or more of sodium carboxymethyl cellulose, hexadecyltrimethylammonium bromide, p-phenylenediamine, a silane coupling agent, and tetracarboxylic dianhydride.

[0021] In some embodiments, in step (2), the amount of the dispersant used is 10-30 parts by weight relative to 100 parts by weight of the hard carbon precursor.

[0022] In some embodiments, in step (2), the activator includes one or more of an alkali metal hydroxide, a metal halide, and an acidic activator, wherein the alkali metal hydroxide includes one or more of potassium hydroxide, sodium hydroxide, lithium hydroxide, and cesium hydroxide; the metal halide includes one or more of magnesium chloride, magnesium bromide, magnesium fluoride, and calcium chloride; and the acidic activator includes one or more of phosphoric acid, sulfuric acid, hydrochloric acid, and nitric acid.

[0023] In some embodiments, in step (2), the amount of the activator is 5-20 parts by weight relative to 100 parts by weight of the hard carbon precursor.

[0024] In some embodiments, in step (3), the template is a nanoscale sacrificial template with a particle size ranging from 1 to 20 nm.

[0025] In some embodiments, in step (3), the template includes one or more of ZnO, Al2O3 or MgO.

[0026] In some embodiments, in step (3), the amount of the template is 1-10 parts by weight relative to 100 parts by weight of the hard carbon precursor.

[0027] In some embodiments, in step (3), the cross-linking agent includes one or more of a peroxide and a multifunctional compound, the peroxide includes one or more of ammonium persulfate, sodium persulfate, potassium persulfate, and hydrogen peroxide, and the multifunctional compound includes one or more of hexamethylenetetramine, melamine, and polyaniline.

[0028] In some embodiments, in step (3), the amount of the cross-linking agent used is 10-40 parts by weight relative to 100 parts by weight of the hard carbon precursor.

[0029] In some embodiments, in step (3), the inert atmosphere is selected from one or more of nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, krypton atmosphere, xenon atmosphere, and radon atmosphere.

[0030] In some embodiments, in step (4), the inert atmosphere is selected from one or more of nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, krypton atmosphere, xenon atmosphere, and radon atmosphere; the organic atmosphere includes one or more of ethanol, methanol, acetone, ethylene glycol, benzyl alcohol, dodecane, diformate, glycerol, ethyl benzoate, and N-methylpyrrolidone.

[0031] In some embodiments, in step (5), the frequency of the microwave or medium frequency heating treatment is 300 kHz-100 GHz, and the treatment time is 30 min-2 h.

[0032] The present application also provides a sodium ion battery negative electrode material, which includes the hard carbon material of the present application, or the sodium ion battery negative electrode material includes the hard carbon material prepared by the preparation method of the hard carbon material of the present application.

[0033] The present application also provides a sodium ion battery, comprising the sodium ion battery negative electrode material described in the present application. Beneficial effects

[0034] In this application, hard carbon materials with a specific high closed porosity and lattice curvature significantly improve their sodium storage performance and collapse resistance. High closed porosity provides more sodium storage space, increasing the storage capacity of sodium ions within the particles. A certain curvature may indicate a certain stress distribution within the particles, thereby reducing stress concentration and minimizing particle deformation and damage. This can improve the collapse resistance of hard carbon particles.

[0035] It is difficult to achieve both high closed porosity and particle fracture strength in the existing technology. It is generally believed that the higher the closed porosity, the greater the defect degree of hard carbon, and the strength of the particles will decrease under high voltage or long cycle. The hard carbon material with specific lattice curvature in this application creatively achieves the unity of the two, thereby synergistically improving the capacity and cycle performance of sodium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 shows examples 1-5 and comparative examples 1 and 3. Atomic pair distribution function map within the range.

[0037] Figure 2 shows the results of Examples 1-5 and Comparative Examples 1 and 3. (6th peak position) atom pair distribution function spectrum.

[0038] Figure 3 is a schematic diagram of the atomic distribution structure of natural graphite.

[0039] FIG4 shows the capacity change trend of button cells using the sodium ion battery hard carbon negative electrode materials prepared in Examples 1-5 and Comparative Examples 1 and 3 in the first charge and discharge test.

[0040] Implementation Methods of the Application

[0041] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0042] In this application, unless otherwise stated, directional words such as "upper" and "lower" are used to refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of this application, the term "including" means "including but not limited to". The various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of this application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, a range of 1-6 or 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0043] In this application, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0044] In the present application, “at least one”, “at least one” and other similar descriptions specifically refer to one or more, one or more; “multiple”, “multiple” and other similar descriptions specifically refer to two or more, two or more. “At least one”, “at least one of the following” or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, “at least one of a, b, or c”, or “at least one of a, b, and c” can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0045] This application uses atom pair distribution function technology to deconstruct crystal information and identify hard carbon materials with specific high closed porosity and lattice curvature, which can significantly improve the sodium storage performance and collapse resistance of hard carbon materials.

[0046] Among them, the Atomic Pair Distribution Function (PDF) technology is a technology used to describe the distance between atoms in solid materials or liquids. It obtains the distribution of the distance between atomic pairs by analyzing the scattered rays in crystal or amorphous samples. In this application, relying on the atomic pair distribution function technology, the microstructure of hard carbon materials can be characterized and controlled. The principle of PDF technology is based on the Bragg scattering and diffuse scattering signals in the scattering experiment. The scattered rays interact with the atoms in the sample and the intensity and scattering angle of the scattered rays are recorded. By performing an inverse Fourier transform on the amplitude and phase of the scattered rays, the distance distribution function between atomic pairs can be obtained. Generally, the full scattering experimental data measured on the target material can be obtained using a neutron scattering source full scattering experimental device, an X-ray synchrotron radiation source full scattering experimental device, or an Ag target X-ray source full scattering experimental device. In order to normalize the experimental data, this application uses an Ag target X-ray source full scattering experimental device to detect the target material.

[0047] Lattice curvature

[0048] Lattice curvature is used to express the relative displacement between adjacent atoms or ions in a crystal. It characterizes the relative relationship between a crystal that has undergone a certain displacement and a standard crystal that has not undergone the displacement, thereby reflecting the deformation of the lattice. Using the atomic pair distribution function technique, by analyzing scattered radiation from a crystalline or amorphous sample, the relative displacement of adjacent atoms or ions in a crystal can be calculated.

[0049] In the atom pair distribution function, the Q value refers to the distance between atomic pairs, that is, the distance between two adjacent atoms. The unit is usually electron volts (eV). It represents the energy difference between atomic pairs, which is caused by the overlap of the electron clouds between the two atoms. Therefore, the size of the Q value is related to the electron cloud distribution of the atomic pair. The definition of D(r) in the atom pair distribution function is a probability density function, which represents the probability that another atom exists at a specific distance r from a certain atom. The resolution of the PDF function real space (also known as r space) is Δr = 2π / Q. A high Q stage can improve the real space resolution, but it is also easy to bring false peak signals. The maximum Q value needs to be adjusted according to the wavelength of the common laboratory light source and the synchrotron radiation light source. The Fourier transform formula of the atomic pair distribution function after data optimization is:

[0050] The Lorch function is introduced here as the M(Q) correction function to reduce the noise peaks in the Fourier transform process. Therefore, the Xth main peak in the optimized hard carbon atom pair distribution function spectrum corresponds to the maximum probability of the Xth shell C atom appearing outside the central C atom.

[0051] As shown in Figures 1 and 2, the Defined as natural graphite in The standard distance value corresponding to the position of the sixth peak in the atomic pair distribution function spectrum within the interval is shown in Figures 1 and 2. That is, for natural graphite, its lattice has no defects, and the position of the sixth shell relative to the central carbon atom is the standard distance value (horizontal axis); It is defined as the hard carbon material The distance value corresponding to the position of the sixth peak in the atomic pair distribution function spectrum within the interval, that is, for hard carbon materials, the distance value between the central carbon atom and the position of the sixth shell (horizontal axis). It can reflect the displacement of the hard carbon material described in this application compared to the lattice structure, The ratio of the incident wavelength λ represents the curvature of the graphene lattice structure in the hard carbon. Figure 3 shows the atomic distribution structure of natural graphite, where the carbon atom labeled 0 is the central atom, and the carbon atoms labeled 1 to 6 reflect the relative position of the carbon atoms in layers 1 to 6 and the central carbon atom.

[0052] The present application provides a hard carbon material, wherein the lattice curvature of the hard carbon material is is 0.03-0.15, preferably 0.035-0.125, more preferably 0.04-0.12; wherein For natural graphite The standard distance value corresponding to the position of the sixth peak in the atomic pair distribution function spectrum within the interval; The hard carbon material is The distance value corresponding to the position of the sixth peak in the atomic pair distribution function spectrum within the interval; the atomic pair distribution function spectrum is obtained by Fourier transforming the total scattering experimental data measured by the Ag target X-ray source total scattering experimental device on the target material.

[0053] In this embodiment, the closed pore volume of the hard carbon material is 0.04-0.5 cm 3 ·g -1 , preferably 0.1-0.45cm 3 ·g -1 , more preferably 0.25-0.4cm 3 ·g -1 .

[0054] In this embodiment, the hard carbon material's tortuosity and closed-pore volume are within the aforementioned ranges, achieving both a high closed-porosity ratio and particle fracture strength, significantly improving the hard carbon material's sodium storage performance and collapse resistance. When used in sodium-ion batteries, this can improve the battery's capacity and cycling performance. A high closed-porosity ratio provides more sodium storage space, increasing the sodium ion storage capacity within the particles. A certain degree of tortuosity may indicate a certain stress distribution within the particles, thereby reducing stress concentration and minimizing particle deformation and damage. This can improve the collapse resistance of the hard carbon particles.

[0055]

Hard carbon raw materials

[0056] The hard carbon material raw material can be one or more of a biomass derivative carbon source or a high molecular organic carbon source, wherein the high molecular organic carbon source is one or more of phenolic resin, epoxy resin, melamine resin, polyfurfuryl alcohol, polyaniline, furfural resin, polyethylene glycol, polyethylene oxide, polyvinylidene fluoride, acrylic resin, polyacrylonitrile and oxidized asphalt;

[0057] In one embodiment, the biomass derivative carbon source is one or more of cellulose, lignin, or sugars, specifically derived from crops, oil crops, agricultural organic residues, forests, and forest industry residues, such as starch, coconut shells, almond shells, pistachio shells, macadamia shells, date shells, peanut shells, walnut shells, peach shells, cotton, wood chips, bamboo, straw, sawdust, and fruit peels. In this embodiment, when using a biomass derivative as a carbon source, the biomass derivative has a low benzene ring content and is less susceptible to rearrangement during the carbonization process, which is more conducive to obtaining a complete crystal structure, thereby achieving controllable crystal structure curvature.

[0058] [Hard carbon particle structure]

[0059] The hard carbon material in the present application is hard carbon particles, which may be spherical, blocky, flaky and / or diamond-shaped. From the perspective of compaction density, spherical hard carbon particles with an aspect ratio of 1.2-3 are preferred.

[0060] In one embodiment, the hard carbon material has an average particle size of 2-50 μm, preferably 5-45 μm, and more preferably 8-40 μm; and a carbon interlayer spacing d002 of 0.35-0.40 nm, preferably 0.37-0.39 nm. In this embodiment, within these ranges, the hard carbon material is less likely to agglomerate and has a good electrical conductivity and sodium ion acceptance. The larger d002 interlayer spacing facilitates rapid sodium ion insertion and extraction within the hard carbon material.

[0061] In this embodiment, the carbon interlayer spacing can be obtained by X-ray diffraction using CuKα radiation as a radiation source and calculated based on the Bragg equation. It is understood that the carbon interlayer spacing can also refer to the detection method of carbon materials such as graphite and hard carbon, and the detection method of the carbon interlayer spacing is not limited here.

[0062] In one embodiment, the specific surface area of ​​the hard carbon material is 0.5-20 m 2 ·g -1 , preferably 1-17m 2 ·g -1 , more preferably 5-7m 2 ·g -1 .

[0063] In one embodiment, the average pore size of the hard carbon material is 0.5-5 nm, preferably 1-4 nm, and more preferably 1.5-3 nm. It is understood that the pore size in this embodiment specifically refers to the pore size of closed pores or micropores inside the hard carbon material.

[0064] It can be understood that the above-mentioned pore size range and specific surface area range are conducive to the absorption of sodium ions and the formation of ion channels, and at the same time have good mechanical strength. When used as a negative electrode material for a sodium ion battery, the negative electrode material is not prone to collapse.

[0065] In one embodiment, the compacted density of the hard carbon material is 0.7-1.3 g / cm 3 , preferably 0.8-1.2g / cm 3 .

[0066] And, in one embodiment, the fracture strength of the hard carbon material is 14.5-22.8 kg·mm -2 , more preferably 16.5-20kg·mm -2 The rupture strength is determined by the particle-to-particle crushing test (EGG) described in ASTM D 6175-3. Specifically, the rupture force of each particle of a representative sample of at least 50 particles is measured and weighted by the length of the extrudate. The EGG test is measured for the entire sample of particles and is simplified to the average value of the rupture force per unit of extrudate length.

[0067] The compaction density and fracture strength are physical properties of the material under the influence of raw material selection, pore structure, particle morphology, and specific surface area control. At the same time, when the compaction density and fracture strength are within the range defined in this application, they also help to improve the mechanical properties, electrical conductivity and chemical stability of the hard carbon material.

[0068]

Process steps

[0069] The present application also provides a method for preparing a hard carbon material, comprising the following steps:

[0070] Step (1): calcining a carbon source to obtain a hard carbon precursor;

[0071] Step (2): mixing the hard carbon precursor with a dispersant and an activator and grinding the mixture to obtain hard carbon precursor powder;

[0072] Step (3): mixing the hard carbon precursor powder with a crosslinking agent and a template, and subjecting the resulting mixture to a medium-temperature carbonization treatment in an inert atmosphere to obtain a first carbonized product;

[0073] Step (4): subjecting the first carbonized product obtained in step (3) to a high-temperature carbonization treatment in an inert atmosphere or a mixed atmosphere of an inert atmosphere and an organic atmosphere to obtain a second carbonized product, that is, obtaining the hard carbon material;

[0074] In this embodiment, through low-temperature pre-calcination, the introduction of dispersants, activators, cross-linking agents and templates, and two-step carbonization treatment of medium-temperature carbonization and high-temperature carbonization, a hard carbon material with specific curvature and closed-pore content can be prepared. It can take into account both high closed-pore rate and particle fracture strength, significantly improve the sodium storage performance and collapse resistance of the hard carbon material, and when the hard carbon material is used in sodium-ion batteries, it can improve the capacity and cycle performance of the sodium-ion battery.

[0075] In step (1):

[0076] The carbon source includes one or more of a biomass-derived carbon source or a high molecular weight organic matter, wherein the biomass-derived carbon source is one or more of cellulose, lignin, or sugars. For details, please refer to the detailed description of the hard carbon raw materials in the hard carbon materials section above and will not be repeated here.

[0077] In one embodiment, the carbon source is calcined at a temperature of 100-350°C, specifically 150-300°C, 200-300°C, 200-250°C, etc.; the holding time is 1-20 hours, specifically 1-18 hours, 2-18 hours, 2-12 hours, 5-10 hours, etc. In a specific embodiment, the calcination temperature is 150-300°C, and the holding time is 2-12 hours. Low-temperature pre-calcination of the carbon source can remove impurities such as moisture and small molecules.

[0078] In step (2):

[0079] In some embodiments, the dispersant may include one or more of sodium carboxymethyl cellulose, hexadecyltrimethylammonium bromide, p-phenylenediamine, a silane coupling agent, and tetracarboxylic dianhydride; compared to 100 parts by weight of the hard carbon precursor, the amount of the dispersant is 1-30 parts by weight, preferably 10-30 parts by weight.

[0080] In some embodiments, in step (2), the activator includes one or more of an alkali metal hydroxide, a metal halide, and an acidic activator, wherein the alkali metal hydroxide includes one or more of potassium hydroxide, sodium hydroxide, lithium hydroxide, and cesium hydroxide, the metal halide includes one or more of magnesium chloride, magnesium bromide, magnesium fluoride, and calcium chloride, and the acidic activator includes one or more of phosphoric acid, sulfuric acid, hydrochloric acid, and nitric acid. Compared to 100 parts by weight of the hard carbon precursor, the amount of the activator is 5-20 parts by weight, preferably 10-18 parts by weight. This amount of activator can give the hard carbon a better overall morphology without damaging the production equipment.

[0081] In some embodiments, the hard carbon precursor powder has a sieved particle size of 250-800 mesh, preferably 300-500 mesh. Powder particles in the above particle size range are conducive to uniform mixing and carbonization in subsequent steps.

[0082] In step (3):

[0083] In some embodiments, the cross-linking agent includes peroxides such as ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, etc., and multifunctional compounds such as hexamethylenetetramine, melamine, polyaniline, etc.; compared to 100 parts by weight of the hard carbon precursor, the amount of the cross-linking agent is 10-40 parts by weight, specifically 10-30 parts by weight, 20-30 parts by weight, etc.

[0084] In some embodiments, the template is a nanoscale sacrificial template, and the particle size of the template is in the range of 1-20 nm, preferably 2-12 nm.

[0085] Specifically, the template can be selected from one or more of ZnO, Al2O3, MgO, and the like, preferably a nanoscale sacrificial template ZnO. The template is used in an amount of 1-10 parts by weight, specifically 1-8 parts by weight, 3-8 parts by weight, 3-5 parts by weight, etc., relative to 100 parts by weight of the hard carbon precursor.

[0086] In some embodiments, the medium-temperature carbonization treatment temperature is 400-900°C, specifically 400-800°C, 500-800°C, 600-700°C, etc.; the treatment time is 1-10h, specifically 2-6h, 3-6h, 4-5h, etc.

[0087] It is understandable that, unless otherwise specified, the inert gas involved in this application is mainly used to isolate oxygen, and can be specifically selected from one or more of nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, krypton atmosphere, xenon atmosphere, and radon atmosphere.

[0088] During the medium-temperature carbonization process, the hard carbon precursor undergoes partial graphitization, forming graphite crystallites. Simultaneously, the template occupies some lattice positions, forming defects and causing partial lattice shifts, thus affecting the lattice curvature of the hard carbon material.

[0089] In step (4):

[0090] The temperature of the high-temperature carbonization treatment is 900-1700°C, specifically 900-1600°C, 1000-1500°C, 1000-1300°C, 1200-1300°C, 1200-1600°C, etc. The treatment time is 1-6 hours, specifically 1-4 hours, 2-4 hours, 2-3 hours, etc. During this process, the first carbonized product further undergoes partial graphitization reaction, and part of the carbon undergoes structural rearrangement and short-range diffusion, forming lattice defects and bends. After the template is removed by high temperature, a pore structure is formed at its location where the template is retained.

[0091] It can be understood that the temperature of the high-temperature carbonization treatment is higher than that of the medium-temperature carbonization treatment. When the temperature of the medium-temperature carbonization treatment is 900°C, the temperature of the high-temperature carbonization treatment is greater than 900°C.

[0092] The high-temperature carbonization treatment is carried out in an inert atmosphere or a mixed atmosphere of an inert atmosphere and an organic matter. The inert atmosphere can be referred to the description in step (3) and will not be described in detail here.

[0093] In some embodiments, high-temperature carbonization is performed in a mixed atmosphere of an inert atmosphere and an organic atmosphere. The volume ratio of the organic atmosphere to the inert atmosphere in the mixed atmosphere can be 1:20-1:2, preferably 1:10-1:5. In this embodiment, the introduction of a small amount of organic atmosphere facilitates supplementing a small amount of carbon source during the high-temperature carbonization process, allowing for appropriate adjustments in defects and specific surface area. However, if the volume percentage of the organic atmosphere is too high, it may be detrimental to controlling the hard carbon crystal form.

[0094] Specifically, the organic atmosphere is formed by one or more selected from ethanol, methanol, acetone, ethylene glycol, benzyl alcohol, dodecane, diformate, glycerol, ethyl benzoate, and N-methylpyrrolidone.

[0095] In one embodiment, in step (4), before the high-temperature carbonization treatment, impurities such as the cross-linking agent that have not reacted during the medium-temperature carbonization process in step (3) are removed from the first carbonized product; specifically, the first carbonized product can be cleaned with a solvent, wherein the solvent can be selected according to the type of impurities such as the cross-linking agent, and is not limited here.

[0096] In some embodiments, the method further includes step (5): subjecting the second carbonized product to microwave or medium frequency heating treatment in an inert atmosphere to obtain the hard carbon material.

[0097] The microwave or medium-frequency heating treatment is performed at a frequency of 300kHz-100GHz, preferably 500kHz-10GHz, and more preferably 1-8GHz; the treatment duration is 30 minutes-2 hours, and more preferably 50 minutes-1.5 hours. Microwave or medium-frequency heating not only helps activate the hard carbon surface and pores, increasing the material's specific surface area and adsorption properties, but also eliminates stress caused by partial crystal bending, further improving collapse resistance.

[0098] The present application also provides a sodium ion battery negative electrode material, wherein the sodium ion battery hard carbon negative electrode material comprises the hard carbon material provided in the present application, or the sodium ion battery hard carbon negative electrode material comprises the hard carbon material prepared by the preparation method provided in the present application.

[0099] Furthermore, the present application also provides a sodium ion battery, which includes the sodium ion battery negative electrode material provided in the present application.

[0100] The present application also provides a sodium ion battery, which contains a negative electrode material. The negative electrode material includes the hard carbon material provided in the present application, or the hard carbon material prepared by the preparation method provided in the present application.

[0101] The hard carbon material provided in the present application, when used in the negative electrode of a sodium ion battery, can enable the sodium ion battery to have better capacity and cycle performance, and avoid the collapse of the negative electrode caused by long-term use.

[0102] The technical solutions and technical effects of the present application are described in detail below through specific embodiments, comparative examples and experimental examples. The following embodiments are only some embodiments of the present application and do not specifically limit the present application.

[0103]

Measurement method

[0104] 1- Lattice curvature test

[0105] Total scattering experiments were performed on a PA Nalytical Empyrean diffractometer. A CdTe GaliPIX3D detector was used as the detector, and Fourier transform correction and fitting were performed using PDFgui software.

[0106] Defined as natural graphite in The standard distance value corresponding to the position of the sixth peak in the atomic pair distribution function spectrum within the interval, It is defined as the hard carbon material The distance value corresponding to the position of the sixth peak in the atomic pair distribution function spectrum within the interval is measured as shown in Figure 1, and λ is the wavelength of the silver target Calculate from this The lattice curvature value.

[0107] 2- Average particle size of hard carbon particles

[0108] The particle size distribution was determined by laser diffraction method according to GB / T 19077-2016 using a Mastersizer 2000E laser particle size analyzer (Malvern, UK).

[0109] 3- Closed cell volume

[0110] Determined by true density test, the calculation is based on the density of highly oriented graphite with a density of 2.26g cm-3 as the reference material. The calculation formula V 闭孔 =1 / ρ 真密度 -1 / 2.26, true density is tested according to GB / T24586-2009 standard.

[0111] 4-Specific surface area

[0112] The specific surface area of ​​the negative electrode active material was measured by nitrogen adsorption / desorption method: the negative electrode active material was dried in a vacuum drying oven, then placed in a sample tube, and measured in a specific surface area analyzer (Tristar II 3020M).

[0113] 5-Burst strength

[0114] The determination is carried out by the particle-to-particle crushing test (EGG) described in ASTM D 6175-3. It consists in measuring the rupture force per particle of a representative sample containing at least 50 particles. The results are weighted by the length of the extrudate. The EGG value is the average value of the rupture force measured for the entirety of the sample particles and reduced to the length unit of the extrudate.

[0115] 6-Compacted density

[0116] Use an electronic balance to weigh the treated negative electrode sheet (the negative electrode current collector is coated with a negative electrode active material layer on both sides) with an area of ​​S, and the weight is recorded as W1. Use a caliper to measure the thickness T1 of the negative electrode sheet; use a solvent to wash off the negative electrode active material layer, dry it, measure the weight of the negative electrode current collector, and record it as W2. Use a caliper to measure the thickness T2 of the negative electrode current collector; the compaction density PD of the negative electrode active material layer provided on one side of the negative electrode current collector = (W1-W2) / [(T1-T2)·S].

[0117] 7-002 interplanar spacing

[0118] The X-ray diffraction phase analysis of the hard carbon material sample was performed by using CuKα radiation as the radiation source and was calculated based on the Bragg equation.

[0119] Example 1

[0120] Step (1): Weigh 4 g of coconut shell and place it in a mortar, grind it for 10 min until it is ground into a fine powder, then put the ground coconut shell fine powder into a crucible, uncover it, and heat it to 200°C at a heating rate of 3°C / min, keep it warm for 4 h, and take it out after it cools down naturally;

[0121] Step (2): Add 0.6 g of sodium carboxymethyl cellulose, 0.3 g of sodium hydroxide, and 10 g of water, mix well with the coconut shell hard carbon precursor, and grind it using a 1 cm zirconia ball at a speed of 300 rpm for about 8 hours until the fine powder has a sieve particle size of about 400 mesh;

[0122] Step (3): drying the sieved hard carbon precursor, mixing it with 0.9 g of sodium persulfate and 0.15 g of a template ZnO with a particle size of 10 nm, and carbonizing it at 600° C. for 5 h in a nitrogen atmosphere to obtain a first carbonized product;

[0123] Step (4): placing the first carbonized product in a mixed atmosphere of ethanol / nitrogen = 1:9 at 1200° C. for 3 h, washing it three times with deionized water and ethanol respectively, and centrifuging it to obtain a second carbonized product;

[0124] Step (5): In a nitrogen atmosphere, the second carbonized product is subjected to microwave treatment at a frequency of 1 GHz for a treatment time of 1 h to obtain the final product.

[0125] Example 2

[0126] Step (1): Weigh 4 g of phenolic resin and place it in a mortar, grind it for 8 minutes until it is ground into a fine powder, then place the ground phenolic resin fine powder into a crucible, uncover it, and heat it to 200°C at a heating rate of 3°C / min, keep it warm for 4 hours, and take it out after it cools down naturally;

[0127] Step (2): Add 0.4 g of hexadecyltrimethylammonium bromide, 0.2 g of magnesium chloride, and 10 g of water, mix well with the phenolic resin hard carbon precursor, and grind using a 1 cm zirconium oxide ball at a speed of 200 rpm for about 4 hours until the fine powder has a sieve particle size of about 600 mesh;

[0128] Step (3): drying the sieved hard carbon precursor, mixing it with 0.5 g of hexamethylenetetramine and 0.2 g of a template ZnO with a particle size of 30 nm, and carbonizing it at 400° C. for 3 h in a nitrogen atmosphere to obtain a first carbonized product;

[0129] Step (4): removing impurities from the first carbonized product, carbonizing the product at 900° C. for 2 h in a mixed atmosphere of acetone / nitrogen = 1:9, washing the product three times with deionized water and ethanol, and centrifuging the product to remove the template, thereby obtaining a second carbonized product;

[0130] Step (5): In a nitrogen atmosphere, the second carbonized product is subjected to medium frequency treatment at a frequency of 400 KHz for 30 minutes to obtain a final product.

[0131] Example 3

[0132] Step (1): Weigh 4 g of starch and place it in a mortar. Grind it for 10 min until it becomes a fine powder. Then, place the ground starch powder into a crucible without covering it. Heat it to 200°C at a heating rate of 3°C / min, keep it warm for 4 h, and take it out after it cools down naturally.

[0133] Step (2): Add 0.8 g of sodium carboxymethyl cellulose, 0.4 g of sodium hydroxide, and 10 g of water, mix well with the starch hard carbon precursor, and grind it using a 1 cm zirconia ball at a speed of 500 rpm for about 10 h until the fine powder has a sieve particle size of about 200 mesh;

[0134] Step (3): drying the sieved hard carbon precursor, mixing it with 0.5 g of sodium persulfate and 0.15 g of a template ZnO with a particle size of 10 nm, and carbonizing it at 800° C. for 6 h in a nitrogen atmosphere to obtain a first carbonized product;

[0135] Step (4): removing impurities from the first carbonized product, carbonizing the product at 1400° C. for 4 h in a mixed atmosphere of ethanol / nitrogen = 1:9, washing the product three times with deionized water and ethanol, and centrifuging the product to remove the template, thereby obtaining a second carbonized product;

[0136] Step (5): In a nitrogen atmosphere, the second carbonized product is subjected to microwave treatment at a frequency of 8 GHz for 2 h to obtain the final product.

[0137] Example 4

[0138] Step (1): Weigh 4 g of coconut shell and place it in a mortar, grind it for 10 min until it is ground into a fine powder, then put the ground coconut shell fine powder into a crucible, uncover it, and heat it to 200°C at a heating rate of 3°C / min, keep it warm for 4 h, and take it out after it cools down naturally;

[0139] Step (2): Add 0.6 g of sodium carboxymethyl cellulose, 0.3 g of sodium hydroxide, and 10 g of water, mix well with the coconut shell hard carbon precursor, and grind it using a 0.5 cm zirconia ball at a speed of 500 rpm for about 12 h until the fine powder has a sieve particle size of about 250 mesh;

[0140] Step (3): drying the sieved hard carbon precursor, mixing it with 0.9 g of sodium persulfate and 0.15 g of a template ZnO with a particle size of 20 nm, and carbonizing it at 600° C. for 5 h in a nitrogen atmosphere to obtain a first carbonized product;

[0141] Step (4): removing impurities from the first carbonized product, carbonizing the product at 1200° C. for 3 h in a mixed atmosphere of ethanol / nitrogen = 1:9, washing the product three times with deionized water and ethanol, and centrifuging the product to remove the template, thereby obtaining a second carbonized product;

[0142] Step (5): In a nitrogen atmosphere, the second carbonized product is subjected to microwave treatment at a frequency of 1 GHz for a treatment time of 1 h to obtain the final product.

[0143] Example 5

[0144] Step (1): Weigh 4 g of coconut shell and place it in a mortar, grind it for 10 min until it is ground into a fine powder, then put the ground coconut shell fine powder into a crucible, uncover it, and heat it to 200°C at a heating rate of 3°C / min, keep it warm for 4 h, and take it out after it cools down naturally;

[0145] Step (2): Add 0.6 g of sodium carboxymethyl cellulose, 0.3 g of sodium hydroxide, and 10 g of water, mix well with the coconut shell hard carbon precursor, and grind it using a 1 cm zirconia ball at a speed of 300 rpm for about 8 hours until the fine powder has a sieve particle size of about 400 mesh;

[0146] Step (3): drying the sieved hard carbon precursor, mixing it with 0.9 g of sodium persulfate and 0.15 g of a template ZnO with a particle size of 10 nm, and carbonizing it at 600° C. for 5 h in a nitrogen atmosphere to obtain a first carbonized product;

[0147] Step (4): removing impurities from the first carbonized product, carbonizing it at 1200°C for 3 h in a mixed atmosphere of ethanol / nitrogen = 1:9, washing it three times with deionized water and ethanol respectively, and centrifuging it to remove the template, thereby obtaining a second carbonized product as the final product.

[0148] Comparative Example 1

[0149] Step (1): Weigh 4 g of coconut shell and place it in a mortar, grind it for 10 min until it is ground into a fine powder, then put the ground coconut shell fine powder into a crucible, uncover it, and heat it to 200°C at a heating rate of 3°C / min, keep it warm for 4 h, and take it out after it cools down naturally;

[0150] Step (2): Add 0.6 g of sodium carboxymethyl cellulose, 0.3 g of sodium hydroxide, and 10 g of water, mix well with the coconut shell hard carbon precursor, and grind it using a 1 cm zirconia ball at a speed of 300 rpm for about 8 hours until the fine powder has a sieve particle size of about 400 mesh;

[0151] Step (3): drying the sieved hard carbon precursor, mixing it with 0.9 g of sodium persulfate and 0.15 g of a template ZnO with a particle size of 10 nm, and carbonizing it at 800° C. in a nitrogen atmosphere for 10 h to obtain a carbonized product;

[0152] Step (4): washing with deionized water and ethanol three times in sequence and centrifuging to remove excess impurities, and drying at 100° C. to obtain the final product.

[0153] Comparative Example 2

[0154] Step (1): Weigh 4 g of coconut shell and place it in a mortar, grind it for 10 min until it is ground into a fine powder, then put the ground coconut shell fine powder into a crucible, uncover it, and heat it to 200°C at a heating rate of 3°C / min, keep it warm for 4 h, and take it out after it cools down naturally;

[0155] Step (2): Add 0.6 g of sodium carboxymethyl cellulose, 0.3 g of sodium hydroxide, and 10 g of water, mix well with the coconut shell hard carbon precursor, and grind it using a 1 cm zirconia ball at a speed of 300 rpm for about 8 hours until the fine powder has a sieve particle size of about 400 mesh;

[0156] Step (3): drying the sieved hard carbon precursor, mixing it with 0.9 g of sodium persulfate and 0.15 g of a template ZnO with a particle size of 10 nm, and carbonizing it at 850° C. for 6.5 h in a nitrogen atmosphere to obtain a first carbonized product;

[0157] Step (4): removing impurities from the first carbonized product, carbonizing the product at 900° C. for 1.5 h in a mixed atmosphere of ethanol / nitrogen = 1:9, washing the product three times with deionized water and ethanol, and centrifuging the product to remove the template, thereby obtaining a second carbonized product;

[0158] Step (5): In a nitrogen atmosphere, the second carbonized product is subjected to microwave treatment at a frequency of 1 GHz for a treatment time of 1 h to obtain the final product.

[0159] Comparative Example 3

[0160] Step (1): Weigh 4 g of coconut shell and place it in a mortar, grind it for 10 min until it is ground into a fine powder, then put the ground coconut shell fine powder into a crucible, uncover it, and heat it to 200°C at a heating rate of 3°C / min, keep it warm for 4 h, and take it out after it cools down naturally;

[0161] Step (2): Add 0.6 g of sodium carboxymethyl cellulose, 0.3 g of sodium hydroxide, and 10 g of water, mix well with the coconut shell hard carbon precursor, and grind it using a 1 cm zirconia ball at a speed of 300 rpm for about 8 hours until the fine powder has a sieve particle size of about 400 mesh;

[0162] Step (3): drying the sieved hard carbon precursor, mixing it with 0.9 g of sodium persulfate and 0.15 g of a template ZnO with a particle size of 10 nm, and carbonizing it at 350° C. for 2 h in a nitrogen atmosphere to obtain a first carbonized product;

[0163] Step (4): removing impurities from the first carbonized product, carbonizing the product at 1200° C. for 6 h in a mixed atmosphere of ethanol / nitrogen = 1:9, washing the product three times with deionized water and ethanol, and centrifuging the product to remove the template, thereby obtaining a second carbonized product;

[0164] Step (5): In a nitrogen atmosphere, the second carbonized product is subjected to microwave treatment at a frequency of 1 GHz for a treatment time of 1 h to obtain the final product.

[0165] The performance tests and indicators of Examples 1-5 and Comparative Examples 1-3 are shown in Table 1.

[0166] Table 1 Structure and mechanical properties test of Examples 1-5 and Comparative Examples 1-3

[0167] Battery performance test:

[0168] The sodium ion battery hard carbon negative electrode material prepared in Examples 1-5 and Comparative Examples 1-3 was mixed with conductive carbon black and a binder to form a slurry, which was evenly coated on aluminum foil and dried to form an electrode. A metal sodium sheet was used as the positive electrode, a glass fiber film was used as the diaphragm, a mixed solution of 1 mol / L NaPF6 and ethylene carbonate (EC): dimethyl carbonate (DEC) = 1:1 vol.% was used as the electrolyte, and 5 wt% fluoroethylene carbonate (FEC) was used as an additive to prepare a button cell; the test conditions were: the first discharge test was performed with 30 mA / g to discharge to 0.01 V, and then charged to 2.5 V; the cycle performance test was performed with a constant current charge and discharge test at 50 mA / g, the charge and discharge voltage range was 0.01-2.5 V, and the test was performed at a constant temperature of 25°C. The capacity change trend after the first discharge is shown in Figure 4.

[0169] Table 2 Electrochemical performance test of Examples 1-5 and Comparative Examples 1-3

[0170] According to the structural characterization of Tables 1 and 2, as well as the indicators of rupture strength, initial charge capacity, charge capacity after 500 cycles, and capacity retention rate after 500 cycles, it can be seen that the one-step carbonization of Comparative Example 1 is reflected in the hard carbon structure, with a high closed-pore content and reduced rupture strength. The medium-temperature treatment time of Comparative Example 2 is too long, and the high-temperature treatment time is too short, resulting in excessive lattice curvature, which also affects the rupture strength. Comparative Example 3 has fewer lattice defects, smaller lattice curvature, and smaller closed-pore content by changing the treatment process, and its charge-discharge capacity is obviously insufficient. Comparative Examples 1-3 are not as good as Examples 1-5 in terms of charge capacity and capacity retention rate after 500 cycles, as shown by the case where the lattice curvature and closed-pore content fall within their ranges. Obviously, Examples 1-5 have better sodium storage capacity and pore strength, and are not prone to structural collapse during long-term charge and discharge, and have high cycle stability.

[0171] Those skilled in the art may make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations.

Claims

1. A hard carbon material, wherein, Lattice curvature of the hard carbon material described is 0.03 - 0.15, and the closed pore volume is 0.04 - 0.5 cm 3 ·g -1 ; Among them For comparison with graphite in The standard distance value corresponding to the position of the 6th peak in the atomic pair distribution function spectrum within the interval; For the hard carbon material in The distance value corresponding to the position of the 6th peak in the atomic pair distribution function spectrum within the interval; λ is the wavelength of the silver target The atomic pair distribution function spectrum is obtained by Fourier transform of the total scattering experimental data measured for the target material by a total scattering experimental device with an Ag target X-ray source.

2. The hard carbon material according to claim 1, wherein, The raw material of the hard carbon material is one or more of biomass derivative carbon sources or high molecular organics, wherein the biomass derivative carbon source is one or more of cellulose, lignin or sugars.

3. The hard carbon material according to claim 1 or 2, wherein The hard carbon material is hard carbon particles with an average particle size of 2 - 50 μm and a d002 value of the carbon layer spacing of 0.35 - 0.40 nm. The carbon layer spacing is obtained by X-ray diffraction using CuKα rays as the ray source and calculated based on the Bragg equation.

4. The hard carbon material according to claim 1, wherein, The average pore size of the hard carbon material is 0.5 - 5 nm.

5. The hard carbon material according to claim 1, wherein The specific surface area of the hard carbon material is 0.5 - 20 m 2 ·g -1 .

6. The hard carbon material according to claim 1, wherein, The fracture strength of the hard carbon material is 14.5 - 22.8 kg·mm -2 , and the fracture strength is measured by a particle-particle crushing test described by the ASTM D 6175-3 method.

7. The hard carbon material according to claim 1, wherein The tap density of the hard carbon material is 0.7-1.3 g / cm 3 .

8. A method for preparing a hard carbon material, wherein, It includes the following steps: Step (1): Calcining the carbon source to obtain a hard carbon precursor. Step (2): Mixing and grinding the hard carbon precursor with a dispersant and an activator to obtain a hard carbon precursor powder. Step (3): Mixing the hard carbon precursor powder with a crosslinking agent and a templating agent, and carrying out medium-temperature carbonization treatment on the obtained mixture in an inert atmosphere to obtain a first carbonization product. Step (4): Carrying out high-temperature carbonization treatment on the first carbonization product in an inert atmosphere or a mixed atmosphere of an inert atmosphere and an organic gas atmosphere to obtain a second carbonization product, that is, obtaining the hard carbon material. Wherein, the temperature of the medium-temperature carbonization treatment is 400 - 900 °C, and the treatment duration is 1 - 10 h; the temperature of the high-temperature carbonization treatment is 900 - 1700 °C, and the treatment duration is 1 - 6 h.

9. The method for preparing the hard carbon material according to claim 8, wherein, The preparation method further includes step (5): In an inert atmosphere, carrying out microwave or intermediate frequency heating treatment on the second carbonization product, that is, obtaining the hard carbon material.

10. The method for preparing the hard carbon material according to claim 8, wherein: In step (1), the calcination temperature of the carbon source is 100 - 350 °C, and the heat preservation time is 1 - 20 h.

11. The method for preparing the hard carbon material according to claim 8, wherein: In step (2), the sieving particle size of the hard carbon precursor powder is 250 - 800 mesh.

12. The preparation method of the hard carbon material according to claim 8, wherein: In step (2), the dispersant includes one or more of sodium carboxymethyl cellulose, cetyltrimethylammonium bromide, p-phenylenediamine, silane coupling agent and tetracarboxylic dianhydride.

13. The method for preparing the hard carbon material according to claim 8, wherein: In step (2), compared with 100 parts by weight of the hard carbon precursor, the dosage of the dispersant is 10 - 30 parts by weight.

14. The preparation method of the hard carbon material according to claim 8, wherein: In step (2), the activator includes one or more of alkali metal hydroxides, metal halides, acidic activators. Among them, the alkali metal hydroxides include one or more of potassium hydroxide, sodium hydroxide, lithium hydroxide, cesium hydroxide, the metal halides include one or more of magnesium chloride, magnesium bromide, magnesium fluoride, calcium chloride, and the acidic activators include one or more of phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid.

15. The preparation method of the hard carbon material according to claim 8, wherein: In step (2), compared with 100 parts by weight of the hard carbon precursor, the dosage of the activator is 5 - 20 parts by weight.

16. The method for preparing the hard carbon material according to claim 8, wherein: In step (3), the templating agent is a nano-scale sacrificial templating agent with a particle size range of 1 - 20 nm.

17. The method for preparing the hard carbon material according to claim 8, wherein: In step (3), the templating agent includes one or more of ZnO, Al2O3 or MgO.

18. The method for preparing the hard carbon material according to claim 8, wherein: In step (3), compared with 100 parts by weight of the hard carbon precursor, the dosage of the templating agent is 1 - 10 parts by weight.

19. The preparation method of the hard carbon material according to claim 8, wherein: In step (3), the crosslinking agent includes one or more of peroxides and polyfunctional compounds. The peroxides include one or more of ammonium persulfate, sodium persulfate, potassium persulfate, and hydrogen peroxide. The polyfunctional compounds include one or more of hexamethylenetetramine, melamine, and polyaniline.

20. The method for preparing the hard carbon material according to claim 8, wherein: In step (3), compared with 100 parts by weight of the hard carbon precursor, the dosage of the crosslinking agent is 10 - 40 parts by weight.

21. The preparation method of the hard carbon material according to claim 8, wherein: In step (3), the inert atmosphere is selected from one or more of nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, krypton atmosphere, xenon atmosphere, and radon atmosphere.

22. The method for preparing the hard carbon material according to claim 8, wherein: In step (4), the inert atmosphere is selected from one or more of nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, krypton atmosphere, xenon atmosphere, and radon atmosphere; the organic atmosphere includes one or more of ethanol, methanol, acetone, ethylene glycol, benzyl alcohol, dodecane, dimethyl phthalate, glycerol, ethyl benzoate, and N-methylpyrrolidone.

23. The method for preparing the hard carbon material according to claim 9, wherein, In step (5), the frequency of the microwave or intermediate frequency heating treatment is 300 kHz - 100 GHz, and the treatment duration is 30 min - 2 h.

24. A negative electrode material for a sodium ion battery, wherein, The negative electrode material of the sodium ion battery comprises the hard carbon material according to any one of claims 1 - 7, or the negative electrode material of the sodium ion battery comprises the hard carbon material obtained by the preparation method according to any one of claims 8 - 23.

25. A sodium-ion battery, wherein, The sodium ion battery includes the negative electrode material of the sodium ion battery according to claim 24.

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