Nitrogen and sulfur co-doped hard carbon composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of battery negative electrode materials, and particularly relates to a nitrogen-sulfur co-doped hard carbon composite material and a preparation method and application thereof. The preparation method comprises the following steps: performing pre-carbonization treatment on a carbon source under an anaerobic condition to obtain a carbonized material; the carbonized material is activated in the atmosphere of activated gas, and a nitrogen-sulfur co-doped activated material is obtained; sequentially carrying out impurity removal treatment, water washing, drying and crushing on the nitrogen-sulfur co-doped activated material to obtain a purified crushed material; and carrying out carbonization treatment on the purified crushed material in a protective gas atmosphere to obtain the nitrogen-sulfur co-doped hard carbon composite material. The nitrogen-sulfur co-doped hard carbon composite material provided by the invention is used as a negative electrode material of a sodium-ion battery, and the initial coulombic efficiency and the charging specific capacity are remarkably improved; in a sodium storage process, the material shows higher reversible capacity and more excellent cycling stability and rate capability; meanwhile, the preparation method is simple and suitable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of battery anode material technology, specifically relating to a nitrogen-sulfur co-doped hard carbon composite material, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries possess numerous advantages, including abundant resources, low cost, high energy conversion efficiency, and long cycle life, perfectly meeting the requirements of the new energy field for low cost, long lifespan, and high safety performance. However, compared to lithium-ion batteries, sodium ions have a larger ionic radius, making graphite anodes, widely used in lithium-ion batteries, incompatible. Therefore, alternative suitable anode materials need to be found. In recent years, the application of hard carbon anode materials in sodium-ion batteries has made significant progress.

[0003] Compared to graphite, hard carbon has a larger interlayer spacing and more micropores, thus providing more sodium storage sites. Coal-based hard carbon materials, represented by bituminous coal, anthracite, and charcoal, are characterized by abundant resources, low cost, and high carbon yield. Sodium-ion battery anode materials prepared using coal-based precursors have a sodium storage capacity of approximately 220 mAh / g and an initial efficiency of up to 80%, making them the most cost-effective carbon-based anode materials for sodium-ion batteries currently available. However, coal-based hard carbon still has some shortcomings as a sodium-ion battery anode material, such as low initial coulombic efficiency and low specific capacity. These shortcomings significantly limit the practical application of coal-based hard carbon as a sodium-ion battery anode material. Summary of the Invention

[0004] The purpose of this invention is to provide a nitrogen-sulfur co-doped hard carbon composite material, its preparation method, and its application. The nitrogen-sulfur co-doped hard carbon composite material provided by this invention, as a negative electrode material for sodium-ion batteries, significantly improves the initial coulombic efficiency and specific capacity; it exhibits higher reversible capacity, better cycle stability, and rate performance during sodium storage; at the same time, the preparation method is simple and suitable for industrial application.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing nitrogen-sulfur co-doped hard carbon composite materials, comprising the following steps: The carbon source is pre-carbonized under oxygen-free conditions to obtain carbonized material; The carbonized material is activated in an atmosphere of activating gas to obtain a nitrogen-sulfur co-doped activated material. The activating gas includes a nitrogen-containing gas and a sulfur-containing gas. The flow rate of the nitrogen-containing gas is 1~5 L / min, the flow rate of the sulfur-containing gas is 2~5 L / min, the activation temperature is 200~500℃, and the activation time is 2~5 h. The nitrogen-sulfur co-doped activated material was subjected to impurity removal treatment, water washing, drying and pulverization in sequence to obtain purified pulverized material; The purified pulverized material is carbonized in a protective gas atmosphere to obtain the nitrogen-sulfur co-doped hard carbon composite material, wherein the carbonization temperature is ≥1100℃.

[0006] Preferably, the carbon source includes one or more of coal-based carbon sources, biomass carbon sources, and phenolic resin carbon sources. The coal-based carbon source includes one or more of sub-bituminous coal, lignite, bituminous coal, and anthracite. The biomass carbon source includes one or more of bamboo, coconut shell, and walnut shell. Before the pre-carbonization treatment, the carbon source is further subjected to crushing and sieving in sequence to obtain undersize material. The undersize material is then subjected to pre-carbonization treatment under anoxic conditions to obtain carbonized material. The sieve used for sieving has a mesh size of 50-100 mesh. The temperature of the pre-carbonization treatment is 300-800℃, the time is 2-8 hours, and the oxygen content under the anoxic conditions is ≤0.5%.

[0007] Preferably, the nitrogen-containing gas includes one or more of nitric oxide, nitrous oxide, nitrogen dioxide, dinitrogen trioxide, and dinitrogen tetroxide; the sulfur-containing gas is sulfur dioxide; and the activation treatment time is 1-5 hours.

[0008] Preferably, the impurity removal process involves soaking in an acid solution, the acid solution including one or more of hydrochloric acid, nitric acid, and hydrofluoric acid; the water washing is performed until the pH value is >3; the particle size of the purified pulverized material is 2~20μm; the carbonization treatment is performed at a temperature of 1100~1500℃ for 3~9h; and the protective gas atmosphere is nitrogen.

[0009] The present invention provides a nitrogen-sulfur co-doped hard carbon composite material prepared by the preparation method described in the above technical solution.

[0010] Preferably, the macroscopic morphology of the nitrogen-sulfur co-doped hard carbon composite material is irregular blocky, and it contains one or more of macropores, mesopores and micropores, exhibiting microstructural characteristics of short-range order and long-range disorder. The nitrogen-sulfur co-doped hard carbon composite material has a carbon content of 95-99.7 wt%, a nitrogen content of 300-2000 ppm, a sulfur content of 20-200 ppm, and a specific surface area of ​​3-12 m². 2 / g, particle size D 50 The value is 2~20μm.

[0011] This invention provides the application of the nitrogen-sulfur co-doped hard carbon composite material described above in the anode material of ion batteries.

[0012] This invention provides an ion battery anode material, wherein the active component of the ion battery anode material is the nitrogen-sulfur co-doped hard carbon composite material described in the above technical solution.

[0013] The present invention provides an ion battery negative electrode, comprising a current collector and a negative electrode material disposed on the surface of the current collector, wherein the negative electrode material is the ion battery negative electrode material described in the above technical solution.

[0014] This invention provides an ion battery, wherein the negative electrode of the ion battery is the negative electrode of the ion battery described in the above-described technical solution.

[0015] This invention provides a method for preparing a nitrogen-sulfur co-doped hard carbon composite material, comprising the following steps: pre-carbonizing a carbon source under oxygen-free conditions to obtain a carbonized material; activating the carbonized material in an activating gas atmosphere to obtain a nitrogen-sulfur co-doped activated material, wherein the activating gas includes a nitrogen-containing gas and a sulfur-containing gas, the flow rate of the nitrogen-containing gas is 1~5 L / min, the flow rate of the sulfur-containing gas is 2~5 L / min, the activation temperature is 200~500℃, and the activation time is 2~5 h; sequentially subjecting the nitrogen-sulfur co-doped activated material to impurity removal, water washing, drying, and pulverization to obtain a purified pulverized material; and carbonizing the purified pulverized material in a protective gas atmosphere to obtain the nitrogen-sulfur co-doped hard carbon composite material, wherein the carbonization temperature is ≥1100℃. In the preparation method proposed in this invention, nitrogen-containing gas and sulfur-containing gas are used together as activation gases during the activation process. These gases act as both pore-forming gases, creating pores of different sizes on the carbonized material to provide high sodium storage potential, and as dopants, providing dopant elements (nitrogen and sulfur) during the redox reaction. By controlling the flow rate of the activation gas and the temperature and time of the activation process, this invention significantly improves the specific capacity and initial coulombic efficiency (i.e., first-time efficiency) of the nitrogen-sulfur co-doped hard carbon composite material under the synergistic effect of a specific pore size distribution and a specific amount of nitrogen and sulfur doping. Furthermore, the preparation method proposed in this invention combines the activation and doping processes into one, resulting in low energy consumption, simple operation, high production efficiency, and low production cost, which is conducive to large-scale production.

[0016] This invention provides a nitrogen-sulfur co-doped hard carbon composite material prepared by the preparation method described above. In this invention, after N doping, NC and NO bonds can be formed, which not only provides more active sites for sodium storage and improves the sodium storage capacity, but also enhances the electrochemical reactivity and stability of the material. After S doping, the hard carbon material is more likely to form an sp2 carbon framework, improving the conductivity and reversible capacity of the hard carbon. Moreover, sulfur atoms have relatively large radii, and co-doping can effectively widen the carbon interlayer spacing, which is conducive to the insertion and extraction of sodium ions and reduces the insertion barrier. It can also promote rapid charge transfer, improve the electronic conductivity of the hard carbon anode, and synergistically improve the electrochemical performance of the hard carbon anode. The synergistic effect of the two improves or even avoids the problem of low initial coulombic efficiency existing in existing hard carbon materials, so that the hard carbon anode exhibits higher reversible capacity, better cycle stability and rate performance during sodium storage. Attached Figure Description

[0017] Figure 1 A flowchart illustrating the preparation process of the nitrogen-sulfur co-doped hard carbon composite material provided by this invention; Figure 2 EDS surface scan of the nitrogen-sulfur co-doped hard carbon composite material prepared in Example 6 of this invention; Figure 3 This is a charge-discharge curve of a sodium coin cell made of nitrogen-sulfur co-doped hard carbon composite material prepared in Example 6 of the present invention. Detailed Implementation

[0018] This invention provides a method for preparing nitrogen-sulfur co-doped hard carbon composite materials, comprising the following steps: The carbon source is pre-carbonized under oxygen-free conditions to obtain carbonized material; The carbonized material is activated in an atmosphere of activating gas to obtain a nitrogen-sulfur co-doped activated material. The activating gas includes a nitrogen-containing gas and a sulfur-containing gas. The flow rate of the nitrogen-containing gas is 1~5 L / min, the flow rate of the sulfur-containing gas is 2~5 L / min, the activation temperature is 200~500℃, and the activation time is 2~5 h. The nitrogen-sulfur co-doped activated material was subjected to impurity removal treatment, water washing, drying and pulverization in sequence to obtain purified pulverized material; The purified pulverized material is carbonized in a protective gas atmosphere to obtain the nitrogen-sulfur co-doped hard carbon composite material, wherein the carbonization temperature is ≥1100℃.

[0019] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0020] This invention pre-carbonizes a carbon source under oxygen-free conditions to obtain carbonized material.

[0021] In this invention, prior to the pre-carbonization treatment, the invention preferably further includes sequentially crushing and sieving the carbon source to obtain undersize material.

[0022] In this invention, the carbon source preferably includes one or more of coal-based carbon sources, biomass carbon sources, and phenolic resin carbon sources; in the embodiments, it can be a coal-based carbon source. The coal-based carbon source preferably includes one or more of sub-bituminous coal, lignite, bituminous coal, and anthracite. The biomass carbon source preferably includes one or more of bamboo, coconut shell, and walnut shell. This invention does not have special requirements for the phenolic resin carbon source. In this invention, the pulverization is preferably carried out using a mechanical mill. The sieve used for sieving is preferably 50-100 mesh; in the embodiments, it can be 50 mesh. In this invention, the particles of the carbon source undergoing the pre-carbonization treatment should not be too large, as excessively large particles are detrimental to the chemical reactions of the pre-carbonization and activation treatments, leading to incomplete pre-carbonization and activation reactions. In a specific embodiment of this invention, the undersize material can be the undersize material from a 50-mesh sieve.

[0023] After obtaining the screened material, the present invention pre-carbonizes the screened material under oxygen-free conditions to obtain carbonized material. In this invention, the pre-carbonization treatment is preferably carried out in a carbonization furnace. The temperature of the pre-carbonization treatment is preferably 300~800℃, more preferably 400~700℃, and in the embodiments, it can be 500 or 600℃. The time of the pre-carbonization treatment is preferably 2~8 hours, and in the embodiments, it can be 4, 5, or 6 hours. The oxygen content under the oxygen-free conditions is preferably ≤0.5%. This invention preferably achieves adjustment of the initial pore structure formed during the pre-carbonization process by optimizing the temperature of the pre-carbonization treatment. Temperatures that are too high or too low will affect the size of the initial pore structure, resulting in poor pore structure of the final nitrogen-sulfur co-doped hard carbon composite material, which is detrimental to improving its performance as a sodium-ion battery anode material.

[0024] After obtaining the carbonized material, the present invention activates the carbonized material in an atmosphere of activating gas to obtain a nitrogen-sulfur co-doped activated material. In the present invention, the activation treatment is carried out in an activation furnace. The activation gas includes a nitrogen-containing gas and a sulfur-containing gas. The nitrogen-containing gas preferably includes one or more of nitric oxide, nitrous oxide, nitrogen dioxide, dinitrogen trioxide, and dinitrogen tetroxide, and in the embodiments, it can be nitrogen dioxide. The flow rate of the nitrogen-containing gas is 1~5 L / min, preferably 2~5 L / min, more preferably 2~4 L / min, and in the embodiments, it can be 1 L / min, 2 L / min, 3 L / min, 5 L / min, or 4 L / min. The sulfur-containing gas is preferably sulfur dioxide. The flow rate of the sulfur-containing gas is 2~5 L / min, preferably 3~5 L / min, and in the embodiments, it can be 2 L / min, 3 L / min, 4 L / min, or 5 L / min. The activation treatment temperature is 200~500℃, and in the embodiments, it can be 500℃, 400℃, 350℃, 300℃, or 200℃. The activation treatment time is 1 to 5 hours, and in the examples it can be 2 hours, 2.5 hours, 3 hours, 4 hours or 5 hours.

[0025] In this invention, during the activation process, nitrogen-containing gas and sulfur-containing gas undergo a relatively strong redox reaction with carbon, generating nitrogen and sulfur elements while etching carbon, thus achieving nitrogen and sulfur element doping.

[0026] This invention, through the activation treatment and by controlling the atmosphere of the activation treatment, can optimize the pore structure, increase the number and proportion of micropores and mesopores, improve the connectivity and utilization of the pores, provide more storage space and diffusion paths for sodium ions, and ultimately improve the specific capacity and first-efficiency of the hard carbon anode. This invention also achieves nitrogen and sulfur doping through the activation treatment, which not only changes the electronic structure of hard carbon and enhances the conductivity of the hard carbon material, but also increases active sites. These active sites can serve as adsorption and desorption centers for sodium ions, improving the reactivity and reversibility of sodium ions.

[0027] After obtaining the nitrogen-sulfur co-doped activated material, the present invention sequentially performs impurity removal treatment, water washing, drying, and pulverization on the nitrogen-sulfur co-doped activated material to obtain purified pulverized material. In the present invention, the impurity removal treatment preferably uses an acid solution for immersion impurity removal. The acid solution preferably includes one or more of hydrochloric acid, nitric acid, and hydrofluoric acid, and in the examples, it can be a mixture of hydrochloric acid and nitric acid. The HCl content in the mixture of hydrochloric acid and nitric acid is preferably 5-15 wt%, and in the examples, it can be 10 wt%; the HNO3 content is preferably 1-10 wt%, and in the examples, it can be 5 wt%. The impurity removal treatment preferably includes immersion impurity removal using a mixture of hydrochloric acid and nitric acid. In the present invention, the water washing can be rinsing. The water washing preferably uses deionized water. The water washing is preferably performed until the pH value is >3. The drying is preferably oven drying. The present invention does not have special requirements for the specific implementation of the drying. The pulverization is preferably ball milling.

[0028] In this invention, the particle size of the purified pulverized material is preferably 2~20μm.

[0029] In this invention, if the nitrogen-sulfur co-doped activator is not treated to remove impurities, the residual ash will affect the cycle life of the battery cell and even its safety. In this invention, it is preferable to use an acid solution to wash the nitrogen-sulfur co-doped activator, which can effectively avoid removing the residual ash in the nitrogen-sulfur co-doped activator and improve the electrical performance of the material.

[0030] In this invention, after impurity removal treatment with an acid solution, the product was not washed with water or was not washed sufficiently. The acid solution, being highly acidic, can corrode the surface and internal structure of hard carbon materials, leading to increased surface roughness, affecting electrochemical performance, increasing interfacial resistance, and causing safety issues. This invention discovers that washing the product until the pH of the filtrate is greater than 3 before drying effectively avoids these problems without significantly increasing process complexity or processing costs.

[0031] After obtaining the purified pulverized material, the present invention carbonizes the purified pulverized material in a protective gas atmosphere to obtain the nitrogen-sulfur co-doped hard carbon composite material. In the present invention, the carbonization treatment is preferably carried out in a high-temperature carbonization furnace. The carbonization temperature is ≥1100℃, preferably 1100~1500℃, and in the examples, it can be 1450℃. The carbonization time is preferably 3~9 hours, and in the examples, it can be 6 hours. The protective gas atmosphere can be nitrogen.

[0032] In this invention, if the carbonization temperature is below 1100℃ or the carbonization time is below 3 hours, the carbonization of the material will be incomplete or insufficient, the pore structure will not be fully formed, and the mechanical properties, thermal stability, and electrochemical properties of the material will be poor. If the carbonization temperature is above 1500℃ or the carbonization time is above 9 hours, it will lead to excessive graphitization of the carbon layer, reducing the number of micropores and causing pore shrinkage, collapse, or blockage. This will reduce the active sites for sodium ion insertion and extraction, reduce the transport channels for sodium ions, increase the resistance to sodium ion migration, affect the sodium storage performance, rate performance, and cycle performance of the material, and also increase the preparation cost.

[0033] The present invention provides a nitrogen-sulfur co-doped hard carbon composite material prepared by the preparation method described in the above technical solution.

[0034] In this invention, the nitrogen-sulfur co-doped hard carbon composite material is an amorphous carbon material.

[0035] In this invention, the nitrogen-sulfur co-doped hard carbon composite material exhibits an irregular blocky macroscopic morphology, containing one or more of macropores, mesopores, and micropores, and possesses a microstructural characteristic of short-range order and long-range disorder. In this invention, the macropore diameter is >50 nm, the mesopore diameter is 2-50 nm, and the micropore diameter is <2 nm. The volume percentage of macropores in the nitrogen-sulfur co-doped hard carbon composite material is <1%, the volume percentage of mesopores is <5%, and the volume percentage of micropores is >94%.

[0036] In this invention, the nitrogen-sulfur co-doped hard carbon composite material has a carbon content of 95-99.7 wt%, a nitrogen content of 300-2000 ppm, a sulfur content of 20-200 ppm, and a specific surface area of ​​3-12 m². 2 / g, particle size D 50 The value is 2~20μm.

[0037] This invention reveals that this preparation method can produce materials with a carbon content of 95-99.7 wt%, a nitrogen content of 300-2000 ppm, a sulfur content of 20-200 ppm, and a specific surface area of ​​3-12 m². 2 The specific capacity of the coin cell is >345mAh / g under the condition of charge / discharge cutoff voltage of 2.0~0V, the initial coulombic efficiency is >90.0%, and the particle size D50 is 2~20μm.

[0038] This invention provides the application of the nitrogen-sulfur co-doped hard carbon composite material described above in the anode material of an ion battery. In this invention, the ion battery can be a sodium-ion battery.

[0039] This invention provides an ion battery anode material, wherein the active component of the ion battery anode material is the nitrogen-sulfur co-doped hard carbon composite material described in the above technical solution.

[0040] In this invention, the negative electrode material of the ion battery includes an active component, a conductive agent, and a binder. The conductive agent may be Super P, and the binder may be carboxymethyl cellulose (CMC).

[0041] In this invention, the mass percentage of the active component in the ion battery negative electrode material can be 90%, the mass percentage of the conductive agent can be 10%, and the mass percentage of the binder can be 10%.

[0042] The present invention provides an ion battery negative electrode, comprising a current collector and a negative electrode material disposed on the surface of the current collector, wherein the negative electrode material is the ion battery negative electrode material described in the above technical solution.

[0043] This invention provides an ion battery, wherein the negative electrode of the ion battery is the negative electrode of the ion battery described in the above-described technical solution.

[0044] This invention provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based hard carbon anode material. The method includes: coarsely crushing and sieving a carbon source, and subjecting it to low-temperature oxygen-free treatment to obtain a carbonized coal material; the carbon source includes one or more of bituminous coal, lignite, bituminous coal, and anthracite; transferring the carbonized material to an activation furnace and treating it at a low temperature of 200-500°C for 1-5 hours under a nitrogen dioxide / sulfur dioxide atmosphere to obtain a nitrogen-sulfur co-doped activated material; subjecting the activated material to a strong acid condition for impurity removal treatment to obtain an acid-washed material; rinsing, drying, and ball milling the acid-washed material to obtain a 2-20 μm pulverized material; placing the pulverized material into a high-temperature carbonization furnace and treating it at a high temperature of 1100-1500°C for 3-9 hours under a nitrogen atmosphere; and cooling the product of the high-temperature treatment to room temperature to obtain an amorphous carbon material, which is the high-capacity nitrogen-sulfur co-doped coal-based hard carbon anode material.

[0045] To further illustrate the present invention, the technical solutions provided by the present invention are described in detail below with reference to embodiments, but these should not be construed as limiting the scope of protection of the present invention. In the following embodiments, the preparation of nitrogen-sulfur co-doped hard carbon composite materials is carried out according to... Figure 1 The flowchart shown is followed.

[0046] Example 1 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 4L / min and sulfur dioxide at a flow rate of 5L / min. The material is activated at 200℃ for 5 hours to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material.

[0047] Example 2 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 5L / min and sulfur dioxide at a flow rate of 5L / min. The material is activated at 200℃ for 5 hours to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material.

[0048] Example 3 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 3L / min and sulfur dioxide at a flow rate of 5L / min. The material is activated at 300℃ for 4 hours to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material. Example 4 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 3L / min and sulfur dioxide at a flow rate of 4L / min. The material is activated at 300℃ for 4 hours to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material.

[0049] Example 5 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 2L / min and sulfur dioxide at a flow rate of 4L / min. The material is activated at 350℃ for 3 hours to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material.

[0050] Example 6 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 2L / min and sulfur dioxide at a flow rate of 3L / min. The material is activated at 350℃ for 3 hours to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material.

[0051] Example 7 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 2L / min and sulfur dioxide at a flow rate of 3L / min. The material is activated at 400℃ for 2.5h to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material.

[0052] Example 8 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 1L / min and sulfur dioxide at a flow rate of 3L / min. The material is activated at 400℃ for 2.5h to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material.

[0053] Example 9 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 2L / min and sulfur dioxide at a flow rate of 3L / min. The material is activated at 500℃ for 2 hours to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material.

[0054] Example 10 This embodiment provides a method for preparing a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material: S1. Crush the bituminous coal using a mechanical mill, then sieve it through a 50-mesh screen, retaining the material that passes through the screen; S2. Place the undersize material obtained in the previous step into a carbonization furnace and pre-carbonize it at 600℃ for 5 hours in an oxygen-free environment to obtain bituminous coal. S3. The carbonized material obtained in the previous step is placed into an activation furnace, and nitrogen dioxide is introduced at a flow rate of 1L / min and sulfur dioxide at a flow rate of 2L / min. The material is activated at 500℃ for 2 hours to obtain bituminous coal activated material. S4. The activated material obtained in the previous step is treated with a mixture of hydrochloric acid and nitric acid to remove impurities. The concentration of HCl in the mixture of hydrochloric acid and nitric acid is 10wt%, and the concentration of HNO3 is 5wt%. After the impurity removal treatment at 80℃ for 4h, the bituminous coal acid wash material is obtained. S5. Wash the pickling material obtained in the previous step with deionized water until the pH of the filtrate is greater than 3, then dry it, and then ball mill it until the particle size D50 is 2~20μm. S6. The product obtained in the previous step is carbonized under nitrogen protection at a temperature of 1450℃ for 6 hours to obtain a high-capacity nitrogen-sulfur co-doped coal-based sodium ion anode material.

[0055] Comparative Example 1: Compared with Example 1, the nitrogen dioxide flow rate was too high. Compared with Example 1, the nitrogen dioxide flow rate was adjusted to 7 L / min, while all other parameters remained the same as in Example 1.

[0056] Comparative Example 2: The activation time was too long compared to Example 2. Compared with Example 2, the activation time was adjusted to 6 hours, while all other aspects remained the same as in Example 2.

[0057] Comparative Example 3: The activation temperature was too high compared to Example 10. Compared with Example 10, the activation temperature was adjusted from 500°C in Example 10 to 600°C, while all other aspects remained the same as in Example 10.

[0058] Comparative Example 4: Compared to Comparative Example 4, the sulfur dioxide flow rate was too high. Compared to Example 4, the sulfur dioxide flow rate was adjusted to 6 L / min, while all other parameters remained the same as in Example 4.

[0059] Comparative Example 5: Compared with Example 5, it is not doped with sulfur. Compared to Example 5, this one is free of sulfur, but otherwise remains the same as Example 5.

[0060] Comparative Example 6: Compared to Comparative Example 6, it is not doped with nitrogen. Compared to Example 6, this example does not contain nitrogen doping, but all other aspects remain the same as Example 6.

[0061] Comparative Example 7: Compared to Example 7, it is not doped with nitrogen and sulfur elements. Compared to Example 7, this example does not contain nitrogen or sulfur, but otherwise remains the same as Example 7.

[0062] Comparative Example 8: The sulfur dioxide flow rate was too low compared to Example 8. Compared to Example 8, the sulfur dioxide flow rate was adjusted to 1 L / min, while all other parameters remained the same as in Example 8.

[0063] Comparative Example 9: The activation time was too short compared to Example 9. Compared with Example 9, the activation time was adjusted to 1 hour, while all other aspects remained the same as in Example 9.

[0064] Comparative Example 10: Compared to Example 10, the nitrogen dioxide flow rate was too low. Compared with Example 10, the nitrogen dioxide flow rate was adjusted to 0.5 L / min, while all other parameters remained the same as in Example 10.

[0065] Test Example 1 The specific preparation conditions for each of the above embodiments and comparative examples are shown in Table 1.

[0066] Table 1. Preparation conditions of the examples and comparative examples

[0067] Test Example 2 The high-capacity nitrogen-sulfur co-doped coal-based sodium-ion anode materials prepared according to the above embodiments and comparative examples were subjected to ICP testing to determine the nitrogen and sulfur content, and the specific surface area was also tested. In addition, anode slurries were prepared as anode active materials and coated onto anode current collectors to form anode sheets, which were then assembled into sodium-ion half-cells for electrochemical performance testing. Specifically, the anode slurry consisted of 80% anode active material, 10% conductive agent Super P, and 10% binder CMC by mass, with a sodium sheet as the counter electrode. The initial efficiency and specific capacity were tested at 25°C, with a voltage range of 0–2V and a charge / discharge rate of 0.1C. Nitrogen and sulfur content were determined using ICP testing, and the specific surface area was measured using the nitrogen BET method.

[0068] The test results are shown in Table 2.

[0069] Table 2 Performance of the anode materials prepared in the examples and comparative examples

[0070] From Table 1 and Table 2, we can see that: As shown in Examples 5-7: Under the preparation conditions defined in this invention, nitrogen-sulfur co-doped hard carbon anode materials with an initial efficiency of over 90% and a charge specific capacity of over 340 mAh / g can be obtained without separating activation and doping processes.

[0071] EDS surface scan of the nitrogen-sulfur co-doped hard carbon anode material prepared in Case 6, as shown in Figure 6. Figure 2 As shown. By Figure 2 It can be seen that the N and S elements are evenly distributed in the nitrogen-sulfur co-doped hard carbon anode material prepared in Example 6.

[0072] The charge-discharge curves of the sodium coin cell with nitrogen-sulfur co-doped hard carbon anode material prepared in Case 6 are shown in Figure 6. Figure 3 As shown.

[0073] A comparison of the test results of Comparative Examples 5-7 and Examples 5-7 shows that without additional nitrogen or sulfur doping, both the initial efficiency and the charge specific capacity are significantly lower than those with nitrogen and sulfur co-doping.

[0074] Furthermore, in this invention, the activation temperature and the flow rates of the nitrogen and sulfur sources need to be controlled within a certain range to help obtain a hard carbon anode material with excellent initial efficiency and charge specific capacity. Specifically, the activation temperature is preferably 350~400℃, and the nitrogen and sulfur source flow rates are preferably 2~5L / min. If the activation temperature is too high, the pores will be too large, reducing the effective sodium storage sites and ultimately affecting the charge specific capacity and initial efficiency; if the activation temperature is too low, the pore-forming ability will be insufficient, resulting in very few effective sodium storage sites, ultimately affecting the charge specific capacity and initial efficiency.

[0075] In summary, the preparation method proposed in this invention combines the activation and doping processes into one, resulting in low energy consumption, simple operation, high production efficiency, and low production cost, which is conducive to large-scale production. Under the synergistic effect of a specific pore size distribution and a specific amount of nitrogen and sulfur doping, the specific capacity / first coulombic efficiency of the obtained hard carbon anode material is improved.

[0076] As can be seen from the above embodiments, the preparation method provided by the present invention does not require separate processing of activation and doping, reducing the number of steps, thus resulting in low energy consumption, simple operation, high production efficiency, and low production cost, which is conducive to large-scale production. Under the synergistic effect of a specific amount of nitrogen and sulfur doped, the specific capacity of the obtained hard carbon anode material is improved, and it also has a high first coulombic efficiency.

[0077] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-sulfur co-doped hard carbon composite material, characterized in that, Includes the following steps: The carbon source is pre-carbonized under oxygen-free conditions to obtain carbonized material; The carbonized material is activated in an atmosphere of activating gas to obtain a nitrogen-sulfur co-doped activated material. The activating gas includes a nitrogen-containing gas and a sulfur-containing gas. The flow rate of the nitrogen-containing gas is 1~5 L / min, the flow rate of the sulfur-containing gas is 2~5 L / min, the activation temperature is 200~500℃, and the activation time is 2~5 h. The nitrogen-sulfur co-doped activated material was subjected to impurity removal treatment, water washing, drying and pulverization in sequence to obtain purified pulverized material; The purified pulverized material is carbonized in a protective gas atmosphere to obtain the nitrogen-sulfur co-doped hard carbon composite material, wherein the carbonization temperature is ≥1100℃.

2. The preparation method according to claim 1, characterized in that, The carbon source includes one or more of coal-based carbon sources, biomass carbon sources, and phenolic resin carbon sources. The coal-based carbon source includes one or more of sub-bituminous coal, lignite, bituminous coal, and anthracite. The biomass carbon source includes one or more of bamboo, coconut shell, and walnut shell. Before the pre-carbonization treatment, the carbon source is further subjected to crushing and sieving in sequence to obtain undersize material. The undersize material is then subjected to pre-carbonization treatment under anoxic conditions to obtain carbonized material. The sieve used for sieving has a mesh size of 50-100 mesh. The pre-carbonization treatment temperature is 300-800℃, the time is 2-8 hours, and the oxygen content under the anoxic conditions is ≤0.5%.

3. The preparation method according to claim 1, characterized in that, The nitrogen-containing gas includes one or more of nitric oxide, nitrous oxide, nitrogen dioxide, dinitrogen trioxide, and dinitrogen tetroxide; the sulfur-containing gas is sulfur dioxide; and the activation treatment time is 1-5 hours.

4. The preparation method according to claim 1, characterized in that, The impurity removal process involves soaking the material in an acid solution, which includes one or more of hydrochloric acid, nitric acid, and hydrofluoric acid; the water washing process is carried out until the pH value is greater than 3; the particle size of the purified pulverized material is 2-20 μm; the carbonization process is carried out at a temperature of 1100-1500℃ for 3-9 hours; and the protective gas atmosphere is nitrogen.

5. The nitrogen-sulfur co-doped hard carbon composite material prepared by the preparation method according to any one of claims 1 to 4.

6. The nitrogen-sulfur co-doped hard carbon composite material according to claim 5, characterized in that, The macroscopic morphology of the nitrogen-sulfur co-doped hard carbon composite material is irregular blocky, and it contains one or more of macropores, mesopores and micropores, exhibiting microstructural characteristics of short-range order and long-range disorder. The nitrogen-sulfur co-doped hard carbon composite material has a carbon content of 95-99.7 wt%, a nitrogen content of 300-2000 ppm, a sulfur content of 20-200 ppm, and a specific surface area of ​​3-12 m². 2 / g, particle size D 50 The value is 2~20μm.

7. The application of the nitrogen-sulfur co-doped hard carbon composite material according to claim 5 or 6 in the anode material of ion batteries.

8. An ion battery anode material, characterized in that, The active component of the ion battery anode material is the nitrogen-sulfur co-doped hard carbon composite material as described in claim 5 or 6.

9. A negative electrode for an ion battery, characterized in that, It includes a current collector and a negative electrode material disposed on the surface of the current collector, wherein the negative electrode material is the ion battery negative electrode material according to claim 8.

10. An ion battery, characterized in that, The negative electrode of the ion battery is the negative electrode of the ion battery according to claim 9.

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