A high-capacity sodium-ion battery, a preparation method and applications

Abstract

The application belongs to the field of batteries, and particularly relates to a large-capacity sodium ion battery, a preparation method and application, which comprises a positive electrode layer, an intermediate layer and a negative electrode layer arranged in a stack; the positive electrode layer is injected with a sodium ion electrolyte; the intermediate layer is used for separating the sodium ion electrolyte from the negative electrode layer; the positive electrode layer is prepared from a three-dimensional conductive network structure of a N / S co-doped hollow carbon sphere anchored, and a positive electrode material which synergistically improves electronic conductivity, structural stability and interface compatibility; through systematic design of SiO2 template + sulfur-containing precursor doping, SGO sulfonation modification and in-situ hydrothermal compounding, a three-dimensional conductive network with stable structure and firm interface combination is successfully constructed, so that the comprehensive electrochemical performance of the sodium ion battery positive electrode material is significantly improved, and the sodium ion battery has good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of batteries, specifically a high-capacity sodium-ion battery, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries are considered an important supplement and alternative to lithium-ion batteries due to the abundance, low cost, and wide distribution of sodium resources, especially in cost-sensitive applications such as large-scale energy storage and low-speed electric vehicles. In recent years, with the rapid growth of global demand for renewable energy storage, the research and development of sodium-ion batteries has received widespread attention and has become one of the research hotspots in the field of electrochemical energy storage.

[0003] Sodium-ion batteries work on a similar principle to lithium-ion batteries, both being "rocking chair" rechargeable batteries that store and release energy through the reversible insertion and extraction of sodium ions between the positive and negative electrodes. However, the radius of sodium ions is significantly larger than that of lithium ions, resulting in slow diffusion kinetics of sodium ions in the electrode materials. Furthermore, the volume expansion of the electrode materials during charge and discharge is more pronounced. These factors severely limit the capacity utilization, rate performance, and cycle life of sodium-ion batteries.

[0004] Cathode materials are one of the key factors determining the energy density and cost of sodium-ion batteries. Currently, research on sodium-ion battery cathode materials mainly focuses on three major systems: layered transition metal oxides, Prussian blue compounds, and polyanionic compounds. Among these, polyanionic cathode materials, due to their unique NASICON-type three-dimensional framework structure, possess advantages such as high structural stability, a flat operating voltage plateau, and good thermal stability, making them one of the most promising cathode material systems for application.

[0005] However, polyanionic cathode materials have an inherent defect: due to the strong covalent bond characteristics of polyanionic groups in their crystal structure, the electron cloud overlap is low, resulting in extremely low intrinsic electronic conductivity, far lower than that of layered oxide cathode materials. This defect directly leads to the following problems: (1) limited rate performance, electrons cannot be conducted quickly at high current densities, and the capacity decays sharply; (2) low utilization rate of active materials, some materials are "idle" because they cannot obtain electrons, and the actual capacity is far lower than the theoretical value; (3) severe polarization, affecting energy efficiency. Therefore, how to effectively improve the electronic conductivity of polyanionic cathode materials has become a key technical challenge to promote their commercial application. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0007] The technical solution adopted by this invention to solve its technical problem is: a high-capacity sodium-ion battery as described in this invention, comprising: The positive electrode layer, intermediate layer, and negative electrode layer are stacked together. The positive electrode layer is filled with sodium ion electrolyte; The intermediate layer is used to separate the sodium ion electrolyte from the negative electrode layer; The cathode layer is prepared by a three-dimensional conductive network structure anchored by N / S co-doped hollow carbon spheres, which synergistically improves the cathode material's electronic conductivity, structural stability, and interface compatibility.

[0008] As a further technical solution of the present invention, the preparation of the cathode material includes the following steps: Step 1: Using monodisperse silica microspheres as templates, after surface modification, they are polymerized with pyrrole monomers and sulfur-containing precursors to prepare SiO2@PPy-S core-shell structure precursors; Step 2: The SiO2@PPy-S obtained in Step 1 is subjected to high-temperature carbonization, and then the silicon dioxide template is removed to obtain N / S co-doped hollow carbon spheres; Step two is more specific: The high-temperature carbonization temperature is 700-900℃, the heating rate is 1-5℃ / min, and the holding time is 1-3h; the silica template is removed by etching with hydrofluoric acid or sodium hydroxide solution for 4-12h. Step 3: Sulfonate graphene oxide to obtain sulfonated graphene oxide; Step 4: Disperse the N / S co-doped hollow carbon spheres obtained in Step 2 and the sulfonated graphene oxide obtained in Step 3 in water, adjust the pH to acidic, add the precursor raw material of polyanionic active material, and carry out an in-situ hydrothermal reaction to obtain the sodium-ion battery cathode material.

[0009] As a further technical solution of the present invention: In step one: Monodisperse SiO2 microspheres were dispersed in anhydrous ethanol, and γ-methacryloyloxypropyltrimethoxysilane (KH570) was added. The mixture was refluxed at 60-80℃ for 6-12 h to obtain modified SiO2 microspheres with surface grafted vinyl groups. Modified SiO2 microspheres were dispersed in deionized water, and pyrrole monomer and sulfur-containing precursor were added. The mixture was stirred and adsorbed for 30-60 min. Then ammonium persulfate was added, and the polymerization reaction was carried out at 0-4℃ for 4-8 h to obtain SiO2@PPy-S core-shell structured microspheres.

[0010] As a further technical solution of the present invention: the mass ratio of KH570 to SiO2 is 1:5-1:20.

[0011] As a further technical solution of the present invention: the mass ratio of pyrrole to modified SiO2 is 1:2-1:5, the molar ratio of sulfur-containing precursor to pyrrole is 0.05:1-0.2:1, and the molar ratio of ammonium persulfate to pyrrole is 0.5:1-1.5:1.

[0012] As a further technical solution of the present invention: in step two, the high-temperature carbonization temperature is 700-900℃, the heating rate is 1-5℃ / min, and the holding time is 1-3h.

[0013] As a further technical solution of the present invention: In step three, graphene oxide is dispersed in deionized water to prepare a dispersion of 1-3 mg / mL, a sulfonating reagent is added, the pH is adjusted to 4-6, and the reaction is carried out at 60-80℃ for 6-12 h to obtain sulfonated graphene oxide; wherein, the sulfonating reagent is aminosulfonic acid or p-aminobenzenesulfonic acid, and the mass ratio of the sulfonating reagent to graphene oxide is 1:1-1:5.

[0014] As a further technical solution of the present invention: in step four, the pH of the dispersion is adjusted to 4-5; the temperature of the hydrothermal reaction is 120-200℃ and the time is 12-36 h; the mass ratio of N / S co-doped hollow carbon spheres to sulfonated graphene oxide is 5:1-20:1; and the amount of precursor raw material of polyanionic active material added is calculated according to the mass ratio of active material to N,S-HCS@SGO in the final cathode material as 90:10-98:2.

[0015] A method for preparing a high-capacity sodium-ion battery includes the following steps: The positive electrode layer, intermediate layer, and negative electrode layer of the above-mentioned positive electrode material are prepared respectively; The positive electrode layer, the intermediate layer, and the negative electrode layer are stacked together. Sodium-ion electrolyte is injected into the positive electrode layer to obtain the sodium-ion battery.

[0016] An application of a high-capacity sodium-ion battery, which is used in energy storage, power, and consumer batteries.

[0017] The beneficial effects of this invention are as follows: The hollow carbon spheres prepared by the SiO2 template method of this invention have a regular cavity structure (particle size 100-300 nm, shell thickness 10-20 nm), which provides sufficient buffer space for the volume expansion of active material during sodium ion insertion and extraction, effectively alleviates the mechanical stress of electrode material, and avoids structural collapse during cycling.

[0018] This invention employs a strategy of copolymerizing a sulfur-containing precursor with pyrrole followed by carbonization, achieving atomically uniform dispersion of sulfur in the carbon framework and avoiding doping segregation caused by uneven mixing of solid-phase sulfur powder. The synergistic effect of the N / S dual elements is manifested in: adjusting the ratio of pyridine nitrogen / pyrrole nitrogen / graphite nitrogen to avoid exacerbating side reactions caused by excessive single nitrogen doping; sulfur doping itself provides additional defect sites, enhancing pseudocapacitance contribution; the introduction of CS bonds can suppress excessive condensation of oxygen-containing groups during carbonization, reduce the nano-interfacial tension on the curved carbon shell surface, and enhance the mechanical stability of the hollow structure.

[0019] This invention modifies graphene oxide by sulfonation, introducing sulfonic acid functional groups (-SO3H). Under weakly acidic conditions, these functional groups form a stronger ionic or hydrogen bond network with the nitrogen- or sulfur-containing functional groups on the surface of N / S co-doped hollow carbon spheres, achieving electrostatic self-assembly and upgrading physical contact to chemical bonding, thus significantly improving the interfacial bonding strength.

[0020] N / S co-doped hollow carbon spheres act as rigid spacers anchored between SGO sheets, physically expanding the SGO sheets and effectively suppressing π-π stacking of graphene. This constructs a stable three-dimensional conductive network with SGO as the "surface" and hollow carbon spheres as the "points." This network structure achieves the following: Electron transport: SGO provides long-range conductive pathways, while hollow carbon spheres provide short-range conductive connections, reducing charge transfer resistance; The mesoporous structure of the hollow carbon spheres provides channels for rapid diffusion of electrolyte ions, improving capacity retention at 5C rate.

[0021] This invention uses monodisperse SiO2 microspheres as a template and introduces vinyl groups through KH570 surface modification to achieve directional and uniform polymerization of pyrrole, avoiding the carbon residue problem caused by incomplete pyrolysis of the PMMA template. After carbonization, SiO2 is removed by etching with mild HF or NaOH solution, resulting in a complete carbon shell structure, clear hollow cavities, and good process repeatability.

[0022] This invention uses sulfur-containing organic matter as a sulfur source, copolymerizes it with pyrrole monomers, and then carbonizes it. This achieves atomic-level uniform dispersion of sulfur in the carbon framework, avoiding the problems of excessively high or low local doping, or even the formation of impurity phases such as sodium sulfide, caused by uneven mixing of solid-phase sulfur powder. XPS elemental distribution diagrams confirm that sulfur is uniformly distributed in the carbon spheres without segregation.

[0023] This invention combines the construction of a three-dimensional network with the loading of active materials into a one-step in-situ hydrothermal reaction. During the hydrothermal process, the polyanionic active material precursor preferentially nucleates and grows at the defect sites or SGO functional group sites on the surface of N / S co-doped hollow carbon spheres, achieving precise positioning and avoiding damage to the constructed three-dimensional network caused by secondary high-temperature calcination. Detailed Implementation

[0024] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0025] Example 1 A high-capacity sodium-ion battery according to an embodiment of the present invention includes: This includes a stacked positive electrode layer, an intermediate layer, and a negative electrode layer; The positive electrode layer is filled with sodium ion electrolyte; The intermediate layer is used to separate the sodium ion electrolyte from the negative electrode layer; The positive electrode layer is prepared by a three-dimensional conductive network structure anchored by N / S co-doped hollow carbon spheres, which synergistically improves the positive electrode material's electronic conductivity, structural stability, and interfacial compatibility. The preparation of this positive electrode material includes the following steps: Step 1: Using monodisperse silica microspheres as templates, after surface modification, they are polymerized with pyrrole monomers and sulfur-containing precursors to prepare SiO2@PPy-S core-shell structure precursors; Step one is more specific: Monodisperse SiO2 microspheres were dispersed in anhydrous ethanol, and γ-methacryloyloxypropyltrimethoxysilane (KH570) was added. The mixture was refluxed at 60 °C for 6 h to obtain modified SiO2 microspheres with surface grafted vinyl groups. The mass ratio of KH570 to SiO2 was 1:5. Modified SiO2 microspheres were dispersed in deionized water, and pyrrole monomer and sulfur-containing precursor were added. The mixture was stirred and adsorbed for 30 min. Then, ammonium persulfate was added, and the polymerization reaction was carried out at 0 °C for 4 h to obtain SiO2@PPy-S core-shell structured microspheres. The mass ratio of pyrrole to modified SiO2 was 1:2, the molar ratio of sulfur-containing precursor to pyrrole was 0.05:1, and the molar ratio of ammonium persulfate to pyrrole was 0.5:1. Step 2: The SiO2@PPy-S obtained in Step 1 is subjected to high-temperature carbonization, and then the silicon dioxide template is removed to obtain N / S co-doped hollow carbon spheres; Step two is more specific: The high-temperature carbonization temperature is 700℃, the heating rate is 1℃ / min, and the holding time is 1h; the silica template is removed by etching with hydrofluoric acid or sodium hydroxide solution for 4h. Step 3: Sulfonate graphene oxide to obtain sulfonated graphene oxide; Step three is more specific: Graphene oxide was dispersed in deionized water to prepare a 1 mg / mL dispersion. A sulfonating agent was added, the pH was adjusted to 4, and the mixture was reacted at 60 °C for 6-12 h to obtain sulfonated graphene oxide. The sulfonating agent was aminosulfonic acid, and the mass ratio of the sulfonating agent to graphene oxide was 1:1. Step 4: Disperse the N / S co-doped hollow carbon spheres obtained in Step 2 and the sulfonated graphene oxide obtained in Step 3 in water, adjust the pH to acidic, add the precursor raw material of polyanionic active material, and carry out in-situ hydrothermal reaction to obtain sodium-ion battery cathode material. Step four is more specific: The pH of the dispersion was adjusted to 4-5; the hydrothermal reaction temperature was 120℃ and the time was 12 h; the mass ratio of N / S co-doped hollow carbon spheres to sulfonated graphene oxide was 5:1; and the amount of precursor material added for the polyanionic active material was calculated based on the mass ratio of active material to N,S-HCS@SGO in the final cathode material being 90:10.

[0026] Example 2 A high-capacity sodium-ion battery according to an embodiment of the present invention includes: This includes a stacked positive electrode layer, an intermediate layer, and a negative electrode layer; The positive electrode layer is filled with sodium ion electrolyte; The intermediate layer is used to separate the sodium ion electrolyte from the negative electrode layer; The positive electrode layer is prepared by a three-dimensional conductive network structure anchored by N / S co-doped hollow carbon spheres, which synergistically improves the positive electrode material's electronic conductivity, structural stability, and interfacial compatibility. The preparation of this positive electrode material includes the following steps: Step 1: Using monodisperse silica microspheres as templates, after surface modification, they are polymerized with pyrrole monomers and sulfur-containing precursors to prepare SiO2@PPy-S core-shell structure precursors; Step one is more specific: Monodisperse SiO2 microspheres were dispersed in anhydrous ethanol, and γ-methacryloyloxypropyltrimethoxysilane (KH570) was added. The mixture was refluxed at 70 °C for 9 h to obtain modified SiO2 microspheres with surface-grafted vinyl groups. The mass ratio of KH570 to SiO2 was 1:12. Modified SiO2 microspheres were dispersed in deionized water, and pyrrole monomer and sulfur-containing precursor were added. The mixture was stirred and adsorbed for 45 min. Then, ammonium persulfate was added, and the polymerization reaction was carried out at 2 °C for 6 h to obtain SiO2@PPy-S core-shell structured microspheres. The mass ratio of pyrrole to modified SiO2 was 1:3.5, the molar ratio of sulfur-containing precursor to pyrrole was 0.1:1, and the molar ratio of ammonium persulfate to pyrrole was 1:1. Step 2: The SiO2@PPy-S obtained in Step 1 is subjected to high-temperature carbonization, and then the silicon dioxide template is removed to obtain N / S co-doped hollow carbon spheres; Step two is more specific: The high-temperature carbonization temperature is 800℃, the heating rate is 6℃ / min, and the holding time is 2h; the silica template is removed by etching with hydrofluoric acid or sodium hydroxide solution for 8h. Step 3: Sulfonate graphene oxide to obtain sulfonated graphene oxide; Step three is more specific: Graphene oxide was dispersed in deionized water to prepare a 2 mg / mL dispersion. A sulfonating agent was added, the pH was adjusted to 5, and the mixture was reacted at 70 °C for 8 h to obtain sulfonated graphene oxide. The sulfonating agent was p-aminobenzenesulfonic acid, and the mass ratio of the sulfonating agent to graphene oxide was 1:3. Step 4: Disperse the N / S co-doped hollow carbon spheres obtained in Step 2 and the sulfonated graphene oxide obtained in Step 3 in water, adjust the pH to acidic, add the precursor raw material of polyanionic active material, and carry out in-situ hydrothermal reaction to obtain sodium-ion battery cathode material. Step four is more specific: The pH of the dispersion was adjusted to 4; the hydrothermal reaction temperature was 140℃ and the time was 22 h; the mass ratio of N / S co-doped hollow carbon spheres to sulfonated graphene oxide was 12:1; and the amount of precursor material added for the polyanionic active material was calculated based on the mass ratio of active material to N,S-HCS@SGO in the final cathode material being 94:6.

[0027] Example 3 A high-capacity sodium-ion battery according to an embodiment of the present invention includes: This includes a stacked positive electrode layer, an intermediate layer, and a negative electrode layer; The positive electrode layer is filled with sodium ion electrolyte; The intermediate layer is used to separate the sodium ion electrolyte from the negative electrode layer; The positive electrode layer is prepared by a three-dimensional conductive network structure anchored by N / S co-doped hollow carbon spheres, which synergistically improves the positive electrode material's electronic conductivity, structural stability, and interfacial compatibility. The preparation of this positive electrode material includes the following steps: Step 1: Using monodisperse silica microspheres as templates, after surface modification, they are polymerized with pyrrole monomers and sulfur-containing precursors to prepare SiO2@PPy-S core-shell structure precursors; Step one is more specific: Monodisperse SiO2 microspheres were dispersed in anhydrous ethanol, and γ-methacryloyloxypropyltrimethoxysilane (KH570) was added. The mixture was refluxed at 80 °C for 12 h to obtain modified SiO2 microspheres with surface grafted vinyl groups. The mass ratio of KH570 to SiO2 was 1:20. Modified SiO2 microspheres were dispersed in deionized water, and pyrrole monomer and sulfur-containing precursor were added. The mixture was stirred and adsorbed for 60 min. Then, ammonium persulfate was added, and the polymerization reaction was carried out at 4 °C for 4-8 h to obtain SiO2@PPy-S core-shell structured microspheres. The mass ratio of pyrrole to modified SiO2 was 1:5, the molar ratio of sulfur-containing precursor to pyrrole was 0.2:1, and the molar ratio of ammonium persulfate to pyrrole was 1.5:1. Step 2: The SiO2@PPy-S obtained in Step 1 is subjected to high-temperature carbonization, and then the silicon dioxide template is removed to obtain N / S co-doped hollow carbon spheres; Step two is more specific: The high-temperature carbonization temperature is 900℃, the heating rate is 5℃ / min, and the holding time is 3h; the silica template is removed by etching with hydrofluoric acid or sodium hydroxide solution for 12h. Step 3: Sulfonate graphene oxide to obtain sulfonated graphene oxide; Step three is more specific: Graphene oxide was dispersed in deionized water to prepare a 3 mg / mL dispersion. A sulfonating agent was added, the pH was adjusted to 6, and the mixture was reacted at 80 °C for 12 h to obtain sulfonated graphene oxide. The sulfonating agent was aminosulfonic acid, and the mass ratio of the sulfonating agent to graphene oxide was 1:5. Step 4: Disperse the N / S co-doped hollow carbon spheres obtained in Step 2 and the sulfonated graphene oxide obtained in Step 3 in water, adjust the pH to acidic, add the precursor raw material of polyanionic active material, and carry out in-situ hydrothermal reaction to obtain sodium-ion battery cathode material. Step four is more specific: The pH of the dispersion was adjusted to 5; the hydrothermal reaction temperature was 200℃ and the time was 36 h; the mass ratio of N / S co-doped hollow carbon spheres to sulfonated graphene oxide was 20:1; and the amount of precursor material added for the polyanionic active material was calculated based on the mass ratio of the active material to N,S-HCS@SGO in the final cathode material being 98:2.

[0028] Example 4 The method for preparing a high-capacity sodium-ion battery according to an embodiment of the present invention includes the following steps: The positive electrode layer, intermediate layer, and negative electrode layer were prepared separately. The positive electrode layer, the intermediate layer, and the negative electrode layer are stacked together. A sodium-ion electrolyte is injected into the positive electrode layer to obtain the sodium-ion battery; wherein, the intermediate layer is used to separate the sodium-ion electrolyte from the negative electrode layer.

[0029] Example 5 The high-capacity sodium-ion battery described in Examples 1-3 above is used in energy storage, power, and consumer batteries.

[0030] Comparative Example 1 Comparative Example 1: A sodium-ion battery was prepared using commercially available unmodified polyanionic cathode material Na3V2(PO4)3. Performance tests were conducted on the sodium-ion batteries of Examples 1-3 and Comparative Example 1. Constant current charge-discharge tests were performed using the Landon CT2001A battery testing system. Test conditions: voltage range: 2.0-4.0 V; rate: 0.1C, 0.2C, 0.5C, 1C, 2C, 5C. Rate performance tests were performed using the Landon CT2001A battery testing system, with 5 cycles per rate, and a final return to 0.1C for recovery rate testing. Cyclic performance tests were performed using the Landon CT2001A battery testing system, with 1000 cycles at 1C. Cyclic voltammetry was performed using the Chenhua CHI660E electrochemical workstation, with a scan rate of 0.1-1.0 mV / s and a voltage range of 2.0-4.0 V. AC impedance testing was performed using the Chenhua CHI660E electrochemical workstation, with a frequency range of 100 kHz-0.01 Hz and an amplitude of 5 mV. The test results are as follows: The above performance test results show that the present invention has successfully constructed a three-dimensional conductive network with stable structure and strong interface bonding through the systematic design of SiO2 template + sulfur-containing precursor doping, SGO sulfonation modification and in-situ hydrothermal composite, which significantly improves the comprehensive electrochemical performance of sodium-ion battery cathode material and has good prospects for industrial application.

[0031] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-capacity sodium-ion battery, characterized in that: include: The positive electrode layer, intermediate layer, and negative electrode layer are stacked together. The positive electrode layer is filled with sodium ion electrolyte; The intermediate layer is used to separate the sodium ion electrolyte from the negative electrode layer; The cathode layer is prepared by a three-dimensional conductive network structure anchored by N / S co-doped hollow carbon spheres, which synergistically enhances the cathode material's electronic conductivity, structural stability, and interface compatibility.

2. The high-capacity sodium-ion battery according to claim 1, characterized in that: The preparation of cathode materials includes the following steps: Step 1: Using monodisperse silica microspheres as templates, after surface modification, SiO2@PPy-S core-shell structure precursors are prepared by polymerization reaction with pyrrole monomers and sulfur-containing precursors. Step 2: The SiO2@PPy-S obtained in Step 1 is subjected to high-temperature carbonization, and then the silicon dioxide template is removed to obtain N / S co-doped hollow carbon spheres; Step two is more specific: The high-temperature carbonization temperature is 700-900℃, the heating rate is 1-5℃ / min, and the holding time is 1-3h; the silica template is removed by etching with hydrofluoric acid or sodium hydroxide solution for 4-12h. Step 3: Sulfonate graphene oxide to obtain sulfonated graphene oxide; Step 4: Disperse the N / S co-doped hollow carbon spheres obtained in Step 2 and the sulfonated graphene oxide obtained in Step 3 in water, adjust the pH to acidic, add the precursor raw material of polyanionic active material, and carry out an in-situ hydrothermal reaction to obtain the sodium-ion battery cathode material.

3. A high-capacity sodium-ion battery according to claim 2, characterized in that: In step one: Monodisperse SiO2 microspheres were dispersed in anhydrous ethanol, and γ-methacryloyloxypropyltrimethoxysilane (KH570) was added. The mixture was refluxed at 60-80℃ for 6-12 h to obtain modified SiO2 microspheres with surface grafted vinyl groups. Modified SiO2 microspheres were dispersed in deionized water, and pyrrole monomer and sulfur-containing precursor were added. The mixture was stirred and adsorbed for 30-60 min. Then ammonium persulfate was added, and the polymerization reaction was carried out at 0-4℃ for 4-8 h to obtain SiO2@PPy-S core-shell structured microspheres.

4. A high-capacity sodium-ion battery according to claim 3, characterized in that: The mass ratio of KH570 to SiO2 is 1:5-1:

20.

5. A high-capacity sodium-ion battery according to claim 4, characterized in that: The mass ratio of pyrrole to modified SiO2 is 1:2-1:5, the molar ratio of sulfur-containing precursor to pyrrole is 0.05:1-0.2:1, and the molar ratio of ammonium persulfate to pyrrole is 0.5:1-1.5:

1.

6. A high-capacity sodium-ion battery according to claim 5, characterized in that: In step two, the high-temperature carbonization temperature is 700-900℃, the heating rate is 1-5℃ / min, and the holding time is 1-3h.

7. A high-capacity sodium-ion battery according to claim 6, characterized in that: In step three, graphene oxide is dispersed in deionized water to prepare a dispersion of 1-3 mg / mL. A sulfonating reagent is added, the pH is adjusted to 4-6, and the reaction is carried out at 60-80℃ for 6-12 h to obtain sulfonated graphene oxide. The sulfonating reagent is aminosulfonic acid or p-aminobenzenesulfonic acid, and the mass ratio of the sulfonating reagent to graphene oxide is 1:1-1:

5.

8. A high-capacity sodium-ion battery according to claim 7, characterized in that: In step four, the pH of the dispersion is adjusted to 4-5; the hydrothermal reaction temperature is 120-200℃, and the time is 12-36 h; the mass ratio of N / S co-doped hollow carbon spheres to sulfonated graphene oxide is 5:1-20:1; and the amount of precursor material added for the polyanionic active material is calculated based on the mass ratio of active material to N,S-HCS@SGO in the final cathode material being 90:10-98:

2.

9. A method for preparing a high-capacity sodium-ion battery, characterized in that: Includes the following steps: Prepare the positive electrode layer, intermediate layer and negative electrode layer of the positive electrode material according to any one of claims 1-8 respectively; The positive electrode layer, the intermediate layer, and the negative electrode layer are stacked together. Sodium-ion electrolyte is injected into the positive electrode layer to obtain the sodium-ion battery.

10. An application of a high-capacity sodium-ion battery as claimed in any one of claims 1-8, characterized in that: High-capacity sodium-ion batteries are used in energy storage, power, and consumer batteries.

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