Polymer-derived hard carbon anode materials rich in microporous structure, their preparation methods and applications

Abstract

This invention discloses a polymer-derived hard carbon anode material rich in microporous structure, its preparation method, and its applications, belonging to the field of inorganic materials technology. The preparation method includes: adding nitrogen-containing monomers such as pyrrole, aniline, or indole to an aqueous solution containing a polymeric confinement agent; obtaining a precursor through oxidative polymerization, purification, and drying; and then subjecting it to high-temperature heat treatment in nitrogen gas, utilizing the pyrolysis gas of the confinement agent to in-situ etch the carbon framework. The resulting hard carbon is in the form of nanoparticles with expanded graphite microcrystal spacing and in-situ nitrogen and oxygen doping, forming an open microporous network transformed from closed pores. Through the synergistic effect of "liquid-phase confinement" and "in-situ gas-phase etching," the ion diffusion path is significantly shortened and the migration energy barrier is reduced, improving high-rate sodium storage capacity. Sodium-ion batteries using this material as the anode exhibit excellent rate performance and long-cycle stability, showing broad application prospects in the field of energy storage devices.

Description

Technical Field

[0001] This invention belongs to the field of inorganic material preparation technology, specifically relating to a polymer-derived hard carbon anode material rich in microporous structure, its preparation method, and its application. Background Technology

[0002] With the rapid development of large-scale energy storage systems and new energy devices, sodium-ion batteries have attracted much attention due to their ability to balance high energy density and high power density. Hard carbon materials are considered the most promising anode materials due to their wide availability of precursors and stable structure. However, in scenarios requiring high power output, traditional hard carbon materials face severe kinetic reaction bottlenecks, resulting in poor rate performance.

[0003] Specifically, the existing technology has the following main drawbacks: Firstly, during the liquid-phase synthesis of traditional polymer-derived hard carbon, the primary crystal nuclei are prone to severe agglomeration, resulting in carbonization product particles generally being in the micrometer or large nanometer scale. This greatly elongates the bulk migration path of sodium ions, causing slow diffusion kinetics.

[0004] Secondly, traditional hard carbon typically consists of a dense closed-pore network, lacking highly interconnected open channels, and the interlayer spacing of graphite microcrystals is relatively small. This not only restricts the wetting of the electrolyte and the utilization of the surface's rapid adsorption capacity, but also increases the kinetic energy barrier for sodium ion intercalation.

[0005] Third, existing heteroelement doping processes (such as post-processing or direct carbonization) have bottlenecks such as cumbersome steps and easy loss at high temperatures, resulting in low retention rates of active heteroatoms (such as nitrogen and oxygen) in the products, which seriously restricts the electronic conductivity and pseudocapacitive sodium storage capacity of the materials.

[0006] Therefore, how to effectively suppress the disordered aggregation of hard carbon precursors to achieve particle nano-sized structures, simultaneously construct internal open channels and expand interlayer spacing, and achieve in-situ efficient doping of heterogeneous elements, thereby significantly improving the rate performance and sodium storage capacity of hard carbon anodes, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the problems in existing polymer-derived hard carbon materials, such as disordered agglomeration of crystal nuclei during liquid-phase synthesis, resulting in large particle size of the final product, long solid-phase diffusion paths, high closed-pore ratio, low impurity element retention rate, and slow ion transport kinetics, this invention provides a polymer-derived hard carbon anode material rich in microporous structure, its preparation method, and its application.

[0008] This invention is achieved through the following technical solution: A method for preparing a polymer-derived hard carbon anode material rich in microporous structure includes: In an aqueous solution containing a polymeric confinement agent, a nitrogen-containing organic monomer and an oxidant are added to induce a copolymerization reaction. After the reaction is complete, a polymer precursor is obtained. The amount of polymeric confinement agent added is 0.01% to 0.5% of the total mass of the aqueous solution system. The polymer precursor is subjected to high-temperature heat treatment in an inert gas atmosphere to obtain the polymer-derived hard carbon anode material rich in microporous structure.

[0009] Preferably, the polymeric confinement agent is selected from at least one of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, and polyacrylic acid.

[0010] Preferably, the nitrogen-containing organic monomer is selected from at least one of pyrrole, aniline, and indole.

[0011] Preferably, the oxidant is selected from at least one of ammonium persulfate, potassium persulfate, and hydrogen peroxide.

[0012] Preferably, the total amount of nitrogen-containing organic monomers added is 0.1% to 5.0% of the total mass of the aqueous solution system; when the nitrogen-containing organic monomers include two types, the molar ratio of the two monomers is 1:3 to 3:1.

[0013] Preferably, the amount of oxidant added is 0.5% to 8.0% of the total mass of the aqueous solution system.

[0014] Preferably, the copolymerization reaction is carried out at a system temperature of 0–30°C for a reaction time of 4–24 hours; the inert gas is nitrogen; the high-temperature heat treatment has a heating rate of 2–10°C / min, a temperature of 900–1500°C, and a holding time of 1–6 hours.

[0015] Preferably, the process further includes purifying and drying the polymer precursor, wherein the purification method is at least one of dialysis, filtration, and centrifugation; and the drying method is vacuum drying or freeze drying.

[0016] A polymer-derived hard carbon anode material rich in microporous structure, wherein the average particle size of the polymer-derived hard carbon anode material rich in microporous structure is 30-150 nm, and the average interlayer spacing of graphite microcrystals (002) is 0.370-0.420 nm; the pore structure of the polymer-derived hard carbon anode material includes closed pores and open pore network, and the specific surface area of ​​micropores accounts for not less than 20% of the total specific surface area.

[0017] A sodium-ion battery, characterized in that the negative electrode of the sodium-ion battery comprises the aforementioned polymer-derived hard carbon negative electrode material rich in microporous structure.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a polymer-derived hard carbon anode material rich in microporous structure, its preparation method, and its application, belonging to the field of inorganic material preparation technology. The preparation method includes: adding one or two nitrogen-containing organic monomers selected from pyrrole, aniline, and indole to an aqueous solution containing a polymeric confinement agent; utilizing the steric hindrance effect of the confinement agent to limit the precursor size; and obtaining a polymer precursor through oxidative copolymerization, purification, and drying. Subsequently, the precursor is subjected to high-temperature heat treatment under a nitrogen atmosphere, utilizing the "in-situ vapor phase etching" effect generated by the pyrolysis of the confinement agent to microscopically reshape the carbon framework. The resulting hard carbon material has a nanoscale average particle size, expanded graphite microcrystal spacing, and abundant in-situ heteroatom doping, and contains an open microporous network transformed from closed pores. This invention, through the synergistic effect of "liquid phase confinement" and "in-situ vapor phase etching," effectively shortens the solid-phase diffusion distance of ions and lowers the migration energy barrier on a physical scale, significantly improving the sodium storage capacity of the hard carbon material at high rates. Sodium-ion batteries assembled using this material as the negative electrode exhibit excellent rate performance and long-term cycle stability at high current densities, and have broad application prospects in the field of high-performance energy storage devices.

[0019] Furthermore, this invention achieves controllable nanoscale particle size regulation: by introducing a specific concentration (0.01%–0.5%) of a polymer confinement agent, the disordered aggregation and excessive growth of precursor crystal nuclei are effectively suppressed through steric hindrance by utilizing its "liquid-phase confinement" effect during the liquid-phase polymerization stage. This significant particle nanostructuring effect shortens the solid-phase diffusion distance of sodium ions by several orders of magnitude, breaking down diffusion barriers at the physical scale.

[0020] Furthermore, this invention constructs a highly developed open microporous network: utilizing the "in-situ vapor-phase etching" effect of a polymer confinement agent during high-temperature pyrolysis, oxidizing gases are released. This effect breaks the original dense stacking of the carbon skeleton, transforming some closed pores into highly developed open microporous channels, significantly enriching the microporous structure of the material, and providing low-resistance channels for the rapid shuttle of ions.

[0021] Furthermore, this invention achieves in-situ efficient doping and defect engineering of heterogeneous elements: This invention utilizes nitrogen-rich organic monomers (such as pyrrole, aniline, and indole) and oxygen-containing polymeric confinement agents to synergistically construct a precursor network, achieving in-situ doping of nitrogen and oxygen elements during heat treatment. This in-situ doping not only improves the electronic conductivity of the carbon substrate but also constructs a large number of highly active edge defect sites, providing abundant pseudocapacitive adsorption centers for sodium ions.

[0022] Furthermore, this invention achieves an expanded average interlayer spacing of (002) graphite microcrystals: the physical expansion of the etching gas between carbon layers significantly expands the interlayer spacing to 0.370–0.420 nm. The spacious crystal channels significantly reduce the kinetic energy barrier for sodium ion intercalation and deintercalation in the bulk phase.

[0023] Furthermore, the preparation process of this invention is simple and easy to industrialize: by using aqueous polymerization and conventional carbonization processes, and by precisely controlling the concentration and ratio of monomers, confinement agents and oxidants, the material structure can be precisely customized, which has broad application prospects in the field of high-performance sodium ion energy storage devices. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 These are scanning electron microscope (SEM) images comparing the hard carbon materials prepared according to this invention. Figure 1 a represents the hard carbon material prepared in Comparative Example 1. Figure 1 b is the hard carbon material with a rich microporous structure prepared in Example 1; Figure 2 These are transmission electron microscopy (TEM) comparison images of the materials prepared in Example 1 and Comparative Example 1 of the present invention. Figure 2 a is a low-magnification morphology image of the hard carbon material prepared in Comparative Example 1. Figure 2 b is a low-magnification morphology image of the hard carbon material rich in microporous structure prepared in Example 1; Figure 2 c is a high-resolution transmission image of the hard carbon material prepared in Comparative Example 1. Figure 2 d is a high-resolution transmission image of the hard carbon material rich in microporous structure prepared in Example 1; Figure 3 These are pore structure characterization diagrams of the products of this invention. Figure 3 a represents the nitrogen adsorption-desorption isotherm. Figure 3 b is the aperture distribution diagram calculated based on the density functional theory model; Figure 4 This is a comparison chart showing the sodium storage rate performance of the various products of this invention as negative electrode materials in a sodium-ion battery system. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0027] To address the problems in existing polymer-derived hard carbon materials during liquid-phase synthesis, such as disordered agglomeration of crystal nuclei, resulting in large particle size, long solid-phase diffusion paths, high closed-pore ratio, low impurity element retention, and sluggish ion transport kinetics, this invention provides a polymer-derived hard carbon anode material rich in microporous structure, its preparation method, and its applications, as detailed below: 1. Experimental Materials The nitrogen-containing organic monomers, polymeric confinement agents, oxidants, polyvinylidene fluoride, acetylene black, sodium hexafluorophosphate, diethylene glycol dimethyl ether, N-methylpyrrolidone, and current collector copper foil involved in the various embodiments and comparative examples of this invention are all analytical grade or battery-grade products purchased from conventional commercial channels.

[0028] 2. General preparation mechanism and explanation of its applicability The preparation process of this invention is based on the synergistic mechanism of "liquid phase confinement" and "in-situ vapor phase etching". In specific implementation, the polymer confinement agents described, such as polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, and polyacrylic acid, all have long-chain polymer structures rich in polar functional groups, which can effectively perform steric confinement and high-temperature gas release etching functions. Regarding the nitrogen-containing organic monomers, pyrrole, aniline, and indole all possess similar nitrogen-containing heterocyclic or aromatic ring structures, and can all undergo free radical copolymerization under the induction of oxidants to construct a cross-linked polymer backbone rich in defects; Regarding the oxidants, ammonium persulfate, potassium persulfate, and hydrogen peroxide can all provide equivalent oxidation potentials to trigger the above polymerization reaction.

[0029] Based on the high similarity of the substances in each group in terms of chemical structure and physicochemical function, the reagents in the same group are completely interchangeable within the process parameters defined in this invention, and can all synergistically achieve the nano-sizing of hard carbon material particles and the directional construction of internal microporous networks.

[0030] 3. The general preparation process and assembly flow of polymer-derived hard carbon anode materials rich in microporous structures are as follows: (1) Preparation of precursor: Dissolve the polymer confinement agent with a mass fraction of 0.01% to 0.5% of the total mass of the aqueous solution system in deionized water to form an aqueous solution system; then add nitrogen-containing organic monomers, and control the total mass of the monomers added to be 0.1% to 5.0% of the total mass of the aqueous solution system, and when two nitrogen-containing organic monomers are included, adjust the molar ratio of the two to be 1:3 to 3:1; An oxidant is added to the reaction system at a temperature of 0–30°C, and the mass of the added oxidant is controlled to be 0.5%–8.0% of the total mass of the aqueous solution system. The reaction is carried out for 4–24 h. After the reaction is completed, the product is purified to remove unreacted monomers and oligomer impurities. The purification method is selected from at least one of dialysis, filtration or centrifugation. Subsequently, the product is freeze-dried or vacuum-dried to obtain a dry polymer precursor powder.

[0031] (2) Carbonization treatment: The precursor powder is placed in a nitrogen atmosphere and heated to 900-1500°C at a heating rate of 2-10 °C / min, and held at that temperature for 1-6 h. The carbon skeleton is etched by the gaseous products generated in situ in the precursor to construct a hard carbon material rich in micropores. After carbonization, the material is cooled to room temperature in the furnace to obtain the target product.

[0032] (3) Preparation of negative electrode sheet: Weigh the active material (polymer-derived hard carbon negative electrode material prepared in this invention), conductive agent (acetylene black) and binder (polyvinylidene fluoride) in a mass ratio of 8:1:1; place the material in an agate mortar, add N-methylpyrrolidone solvent dropwise and grind thoroughly to form a uniform electrode slurry; then coat the slurry evenly on the surface of the copper foil current collector, vacuum dry at 110°C for 12 h and cut into circular electrode sheets.

[0033] (4) Sodium-ion battery assembly and testing: CR2032 coin-type sodium-ion batteries were assembled in a glove box filled with high-purity argon gas (water and oxygen content both below 0.1 ppm). The electrode prepared above was used as the working electrode, and a metallic sodium sheet was used as the counter electrode. A 1 mol / L sodium hexafluorophosphate solution in diethylene glycol dimethyl ether was used as the electrolyte. After the battery was assembled, it was allowed to stand for an appropriate time, and then electrochemical performance tests such as constant current charge-discharge, cyclic voltammetry, and AC impedance were performed.

[0034] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1 (1) Preparation of precursor: 1.0 g of polyvinylpyrrolidone was dissolved in 440 mL of deionized water (the amount added corresponds to 0.2% of the total mass of the aqueous solution system), magnetically stirred and pre-cooled to 0-2°C; then 3.42 mL of aniline and 2.61 mL of pyrrole (the total mass fraction of monomers is about 1.2%, and the molar ratio of the two is about 1:1); 60 mL of 1 mol / L ammonium persulfate solution was slowly added over 5-10 min (the amount of oxidant added corresponds to about 2.6% of the total mass of the aqueous solution system), and the reaction was allowed to stand at 0-2°C for 12 h; the reaction solution was transferred to a dialysis bag for dialysis purification, and freeze-dried to obtain precursor powder.

[0036] (2) Heat treatment carbonization: The temperature is increased to 1300°C at 5 °C / min under nitrogen atmosphere and held for 2 h to obtain polymer-derived hard carbon anode material rich in microporous structure.

[0037] (3) Prepare negative electrode sheets according to the general process and assemble them into coin cell sodium-ion batteries for electrochemical performance testing.

[0038] Comparative Example 1 The preparation steps are basically the same as those in Example 1, except that: in step (1), polyvinylpyrrolidone is not added, that is, the oxidative copolymerization reaction is carried out under conditions without polymer confinement agents.

[0039] Example 2 The preparation steps are basically the same as in Example 1, except that the amount of polyvinylpyrrolidone added in step (1) is changed to 0.5 g (corresponding to 0.1% of the total mass of the aqueous solution system).

[0040] Example 3 The preparation steps are basically the same as in Example 1, except that the amount of polyvinylpyrrolidone added in step (1) is changed to 1.5 g (corresponding to 0.3% of the total mass of the aqueous solution system).

[0041] Table 1: Summary of pore structure parameters of products from Comparative Example 1 and various embodiments

[0042] pass Figure 1 and Figure 2 As can be seen from the comparison, the hard carbon particles generated in Comparative Example 1 exhibit an irregular aggregated state, with a particle size distribution between 100-500 nm (e.g., ...). Figure 1 a and Figure 2 As shown in a); while in Example 1, under the liquid-phase confinement of polyvinylpyrrolidone, the particle size was significantly reduced, exhibiting a uniform nanosphere morphology with an average particle size of about 50 nm (as shown in a). Figure 1 b and Figure 2 (As shown in b). Further observation using high-resolution transmission electron microscopy (HRTEM) images revealed that the interlayer spacing of the graphite microcrystals in Comparative Example 1 was 0.378 nm (as shown in b). Figure 2 As shown in c), the interlayer spacing in Example 1 significantly expands to 0.412 nm due to the localized pressure generated by the in-situ vapor-phase etching of the polymer confinement agent during high-temperature pyrolysis (as shown in c). Figure 2 (As shown in d). This significant particle nanostructuring and interlayer spacing expansion effect not only greatly shortens the solid-phase diffusion distance of sodium ions, but also significantly reduces the kinetic energy barrier for ion intercalation and deintercalation in the bulk phase. Figure 3 The above-mentioned ultrafine nanoscale features and the open channel structure generated by in-situ vapor phase etching were further confirmed. Table 1 above quantitatively demonstrates the reshaping effect of the polymer confinement agent on the pore structure, combined with Figure 3 Example 1 exhibits the most significant mesoporous / microporous features, demonstrating that the process successfully breaks the dense stacking of the carbon skeleton.

[0043] Table 2: Summary of elemental contents of products from Comparative Example 1 and various embodiments

[0044] As can be seen from the elemental composition comparison in Table 2, the introduction of polymeric confinement agents significantly improved the retention rates of nitrogen and oxygen heteroatoms in the carbonization products. This highly efficient in-situ heteroelement doping not only improved the electronic conductivity of the carbon substrate but also provided abundant active centers for the rapid adsorption of sodium ions.

[0045] Rate performance tests were conducted on the negative electrodes of each group, and the results are shown in Table 3 below: Table 3: Comparison of sodium storage specific capacity of Comparative Example 1 and various embodiments at different current densities

[0046] Depend on Figure 4 As can be seen, thanks to the short diffusion path at the nanoscale and the extended interlayer spacing, the specific capacity of Example 1 at high rates far exceeds that of Comparative Example 1.

[0047] Example 4 (1) Preparation of precursor: 0.05 g of polyvinyl alcohol was dissolved in 500 mL of deionized water (the amount of limiting agent added corresponds to about 0.01% of the total mass of the aqueous solution system), and the system was magnetically stirred and the temperature of the system was kept at 30°C; only 0.5 g of aniline was added as monomer (the total mass of monomer added is about 0.1%); then 2.5 g of potassium persulfate was added (the amount of oxidant added is about 0.5%), and the reaction was carried out at 30°C for 4 h; the reaction solution was purified by centrifugation, and the obtained solid was vacuum dried at 60°C for 24 h to obtain precursor powder.

[0048] (2) Heat treatment carbonization: Under nitrogen atmosphere, the temperature is increased to 900°C at 2 °C / min, held for 6 h, and then cooled to obtain polymer-derived hard carbon anode material rich in microporous structure.

[0049] (3) Prepare negative electrode sheets according to the general process and assemble them into coin cell sodium-ion batteries for electrochemical performance testing.

[0050] Example 5 (1) Preparation of precursor: 2.5 g of polyethylene glycol was dissolved in 500 mL of deionized water (the amount of confinement agent added corresponds to about 0.5% of the total mass of the aqueous solution system), and the system was magnetically stirred and the temperature of the system was kept at 0~2°C; only 25 g of pyrrole was added as monomer (the total mass of monomer added is about 5.0%); then 40 g of hydrogen peroxide aqueous solution was slowly added (the amount of oxidant added is about 8.0%), and the reaction was allowed to stand at 0~2°C for 24 h; the reaction solution was separated and purified by vacuum filtration, and the obtained solid was freeze-dried to obtain precursor powder.

[0051] (2) Heat treatment carbonization: Under nitrogen atmosphere, the temperature is increased to 1500°C at 10 °C / min, held for 1 h, and then cooled to obtain polymer-derived hard carbon anode material rich in microporous structure.

[0052] (3) Prepare negative electrode sheets according to the general process and assemble them into coin cell sodium-ion batteries for electrochemical performance testing.

[0053] Example 6 (1) Preparation of precursor: 0.75 g of polyacrylic acid was dissolved in 500 mL of deionized water (the amount of limiting agent added corresponds to about 0.15% of the total mass of the aqueous solution system), and the system was magnetically stirred and the temperature of the system was kept at 15°C; only 12.5 g of indole was added as monomer (the total mass of monomer added is about 2.5%); then 20 g of ammonium persulfate was added (the amount of oxidant added is about 4.0%), and the reaction was carried out at 15°C for 12 h; the reaction solution was transferred to a dialysis bag for dialysis purification, and then vacuum dried to obtain precursor powder.

[0054] (2) Heat treatment carbonization: Under nitrogen atmosphere, the temperature is increased to 1100°C at 5 °C / min, held for 4 h, and then cooled to obtain polymer-derived hard carbon anode material rich in microporous structure.

[0055] (3) Prepare negative electrode sheets according to the general process and assemble them into coin cell sodium-ion batteries for electrochemical performance testing.

[0056] Example 7 (1) Preparation of precursor: 2.0 g of polyvinylpyrrolidone was dissolved in 500 mL of deionized water (the amount of limiting agent added corresponds to about 0.4% of the total mass of the aqueous solution system), and the system was magnetically stirred and the temperature of the system was kept at 25°C; aniline and indole monomers (total mass of 15 g, total added mass of monomers of about 3.0%, and the molar ratio of the two is 3:1) were added; then 25 g of potassium persulfate (oxidant added of about 5.0%) was added, and the reaction was carried out at 25°C for 8 h; the reaction solution was purified by centrifugation, and the obtained solid was vacuum dried at 60°C to obtain precursor powder.

[0057] (2) Heat treatment carbonization: Under nitrogen atmosphere, the temperature is raised to 1200°C at 8 °C / min, held for 3 h, and then cooled to obtain polymer-derived hard carbon anode material rich in microporous structure.

[0058] (3) Prepare negative electrode sheets according to the general process and assemble them into coin cell sodium-ion batteries for electrochemical performance testing.

[0059] Example 8 (1) Preparation of precursor: 1.5 g of polyacrylic acid was dissolved in 500 mL of deionized water (the amount of confinement agent added corresponds to about 0.3% of the total mass of the aqueous solution system), and the system was magnetically stirred and the temperature of the system was kept at 20°C; pyrrole and indole monomers (total mass of 10 g, total added mass of monomers of about 2.0%, and the molar ratio of the two is 1:2) were added; then 20 g of hydrogen peroxide aqueous solution (oxidant added of about 4.0%) was slowly added, and the reaction was carried out at 20°C for 16 h; the reaction solution was separated and purified by filtration, and the obtained solid was vacuum dried at 60°C to obtain precursor powder.

[0060] (2) Heat treatment carbonization: Under nitrogen atmosphere, the temperature is increased to 1400°C at 5 °C / min, held for 2 h, and then cooled to obtain polymer-derived hard carbon anode material rich in microporous structure.

[0061] (3) Prepare negative electrode sheets according to the general process and assemble them into coin cell sodium-ion batteries for electrochemical performance testing.

[0062] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0063] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0064] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0065] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0066] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0067] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0068] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0069] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0070] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0071] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a polymer-derived hard carbon anode material rich in microporous structure, characterized in that, include: In an aqueous solution containing a polymeric confinement agent, a nitrogen-containing organic monomer and an oxidant are added to induce a copolymerization reaction. After the reaction is complete, a polymer precursor is obtained. The amount of polymeric confinement agent added is 0.01% to 0.5% of the total mass of the aqueous solution system. The polymer precursor is subjected to high-temperature heat treatment in an inert gas atmosphere to obtain the polymer-derived hard carbon anode material rich in microporous structure.

2. The method for preparing a polymer-derived hard carbon anode material rich in microporous structure according to claim 1, characterized in that, The polymeric confinement agent is selected from at least one of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, and polyacrylic acid.

3. The method for preparing a polymer-derived hard carbon anode material rich in microporous structure according to claim 1, characterized in that, The nitrogen-containing organic monomer is selected from at least one of pyrrole, aniline, and indole.

4. The method for preparing a polymer-derived hard carbon anode material rich in microporous structure according to claim 1, characterized in that, The oxidant is selected from at least one of ammonium persulfate, potassium persulfate, and hydrogen peroxide.

5. The method for preparing a polymer-derived hard carbon anode material rich in microporous structure according to claim 1, characterized in that, The total amount of nitrogen-containing organic monomers added is 0.1% to 5.0% of the total mass of the aqueous solution system; when the nitrogen-containing organic monomers contain two types, the molar ratio of the two monomers is 1:3 to 3:

1.

6. The method for preparing a polymer-derived hard carbon anode material rich in microporous structure according to claim 1, characterized in that, The amount of oxidant added is 0.5% to 8.0% of the total mass of the aqueous solution system.

7. The method for preparing a polymer-derived hard carbon anode material rich in microporous structure according to claim 1, characterized in that, The copolymerization reaction is carried out at a system temperature of 0–30°C for a reaction time of 4–24 hours; the inert gas is nitrogen; the high-temperature heat treatment has a heating rate of 2–10°C / min, a temperature of 900–1500°C, and a holding time of 1–6 hours.

8. The method for preparing a polymer-derived hard carbon anode material rich in microporous structure according to claim 1, characterized in that, It also includes purifying and drying the polymer precursor, wherein the purification method is at least one of dialysis, filtration, and centrifugation; and the drying method is vacuum drying or freeze drying.

9. A polymer-derived hard carbon anode material rich in microporous structure, characterized in that, The polymer-derived hard carbon anode material rich in microporous structure is prepared by the preparation method of any one of claims 1 to 8; the average particle size of the polymer-derived hard carbon anode material rich in microporous structure is 30 to 150 nm, and the average interlayer spacing of graphite microcrystals (002) is 0.370 to 0.420 nm; the pore structure of the polymer-derived hard carbon anode material includes closed pores and open pore networks, and the specific surface area of ​​micropores accounts for not less than 20% of the total specific surface area.

10. A sodium-ion battery, characterized in that, The negative electrode of the sodium-ion battery comprises the polymer-derived hard carbon negative electrode material rich in microporous structure as described in claim 9, or the polymer-derived hard carbon negative electrode material rich in microporous structure prepared by the preparation method of the polymer-derived hard carbon negative electrode material rich in microporous structure as described in any one of claims 1-8.

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