Fluorine-doped phosphorus-carbon composite negative electrode material and preparation method thereof

Abstract

The application provides a fluorine-doped phosphorus-carbon composite negative electrode material, which is composed of elemental phosphorus and a fluorine-doped porous carbon substrate, the fluorine-doped porous carbon substrate has gradually decreasing fluorocarbon content from the surface layer to the inside, and the X-ray photoelectron spectrogram (XPS spectrogram) of the F element has characteristic peaks of 687.2±0.1eV and 685.5±0.1eV. The composite material is composed of elemental phosphorus and a porous carbon substrate, the porous carbon is composed of carbon and fluorocarbon. By introducing fluorine atoms into the porous carbon, the structure of carbon and fluorocarbon is constructed, the carbon content of the surface layer to the inside of the porous carbon material gradually increases, and the fluorocarbon content gradually decreases. The introduction of fluorine successfully constructs a polar interface on the surface of the material, and in the battery cycle process, the polar interface effectively improves the polysulfide adsorption of the material to sodium, inhibits the dissolution of sodium polysulfide shuttle, and thus effectively improves the cycle performance of the composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to a phosphorus-carbon composite material and a preparation method thereof, in particular to a fluorine-doped phosphorus-carbon composite negative electrode material and a preparation method thereof. BACKGROUND

[0002] With the demand for large-scale energy storage, secondary batteries with high energy density and low price have developed rapidly. Sodium-ion batteries have become the inevitable choice due to their advantages of abundant resources, wide distribution, low cost, good safety, etc. under the background of lithium resource shortage, price rising and strong demand for energy storage. And with the increasing demand for high energy density, sodium-ion batteries are developing towards higher energy density. Most of the currently commercialized sodium-ion batteries use sodium vanadium phosphate / hard carbon system. Due to the low theoretical capacity of the electrode itself, the energy density of the battery cannot be greatly improved. Generally speaking, the energy density of sodium-ion batteries is determined by the specific capacity of the positive and negative electrode materials and other components of the battery. Among them, the specific capacity of the positive and negative electrode materials is the key to improving the energy density of sodium-ion batteries. Therefore, it is urgent to develop new high-capacity sodium-ion battery positive and negative electrode materials.

[0003] Among the currently developed sodium-ion battery negative electrode materials, hard carbon material is favored due to its low sodium storage site, low cost, environmental protection, stable structure, good charge-discharge cycle performance and high safety performance, and is considered as the most likely to realize large-scale commercial application in sodium-ion battery negative electrode materials. However, hard carbon material also has the characteristics of low first coulomb efficiency, insufficient capacity, insufficient long cycle performance and poor rate performance. Therefore, it is urgent to develop a sodium-ion battery negative electrode material with high capacity and high first coulomb efficiency, which can obtain high capacity while considering the first coulomb efficiency and cycle performance. Phosphorus-carbon negative electrode material as a kind of sodium-ion battery negative electrode material has the advantages of abundant resources, low cost, high capacity, good air stability, excellent rate performance, moderate working potential and flame retardant, and is also considered to surpass hard carbon in energy density. Phosphorus-carbon applied to sodium-ion battery negative electrode, just like silicon-carbon applied to lithium-ion battery negative electrode, can effectively improve the energy density of sodium-ion battery. However, phosphorus still cannot avoid the huge volume expansion during sodium extraction and insertion, and due to the huge solvation energy of the electrolyte, the sodium polyphosphates are dissolved and shuttled during the cycle process, resulting in a large capacity decay. Based on this, various methods are used to improve the cycle performance of phosphorus-carbon negative electrode material. Porous carbon material has a rich pore structure, which can provide a buffer space for the volume expansion of phosphorus, effectively improving the cycle stability of phosphorus-carbon negative electrode material. Another effective way is to construct a polar interface on the surface of the phosphorus-carbon negative electrode material, which can improve the adsorption of sodium polyphosphates through the polar interface, effectively inhibit the dissolution and shuttling, and improve the cycle performance of the material. Therefore, developing a phosphorus-carbon negative electrode material with both space buffer structure and polar interface is the key to solving the insufficient cycle performance of the material. The buffer space can effectively alleviate the volume expansion of phosphorus during charging and discharging, and the polar interface can improve the interaction force between phosphorus and the carbon substrate, reducing the shedding of the material. The present application is based on the above two key scientific problems, by constructing a polar interface on the surface of the porous carbon, introducing fluorine atoms, and then depositing phosphorus to form a stable C-F-P structure, the pores of the porous carbon can effectively buffer the volume expansion of phosphorus, and the formed C-F-P structure can improve the interaction force between phosphorus and the carbon substrate, finally achieving the purpose of improving the cycle performance of the material.

[0004] CN115832264A discloses a phosphorus-carbon composite material composed of carbon spheres and red phosphorus filled in the carbon spheres; CN117673304A discloses a phosphorus-carbon composite material obtained by depositing a phosphorus source on a carbon source by a vapor deposition method; and CN116759556A discloses a phosphorus-carbon composite material obtained by mixing phosphorus and carbon, pre-activating the mixture, and then performing a series of treatments on the slurry obtained by mixing and crushing the mixture with water and a dispersing agent. Although there are many reports on phosphorus-carbon composite materials in the prior art, there are few reports on phosphorus-carbon composite materials that simultaneously have a space buffer structure and a polar carbon interface. The prior art also has reports on fluorine-doped carbon sources, such as CN115036519A. F-doping can modify the pore density and hydrophilicity of carbon materials to some extent, but there is no report on the formation of stable chemical bonds between fluorine and phosphorus. CN117832462A discloses a fluorine-doped carbon-loaded red phosphorus material, which is obtained by carbonizing a polymer obtained from urea and p-phenylenediisocyanate, and then mixing the carbon material obtained by mechanically grinding polytetrafluoroethylene, and sintering the mixture in an inert atmosphere to obtain fluorine-doped carbon nanosheets. Then, red phosphorus is infiltrated into the carbon nanosheets by evaporation-condensation to obtain a fluorine-doped carbon-loaded red phosphorus material. This patent simultaneously performs fluorine doping and phosphorus-carbon compounding, but lacks the design of a space buffer structure and a clear understanding of the chemical structure between carbon and fluorine, and the preparation method is complex. SUMMARY

[0005] To solve the above technical problems, the present application provides a phosphorus-carbon negative electrode material with a polar interface and a preparation method thereof. In the method, a fluorine-containing substance is introduced into a double-temperature-zone heating furnace to pyrolyze the fluorine-containing substance and generate fluorine active components, so that the fluorine active components and the porous carbon undergo a thermal reaction to form fluorocarbon in situ on the surface, and the fluorocarbon and the carbon form a continuous and dense composite structure. Subsequently, the porous carbon treated by fluorination is used to load phosphorus to prepare a phosphorus-carbon negative electrode material, which is applied as a negative electrode material in a sodium ion battery, can effectively improve the coulomb efficiency and reversible capacity of the battery, and make the battery have more excellent cycle stability. Moreover, the phosphorus-carbon negative electrode material is simple to prepare and easy to produce industrially, and has a wide application prospect.

[0006] To achieve the above-mentioned application purposes, the present application provides a fluorine-doped phosphorus-carbon composite negative electrode material composed of elemental phosphorus and a fluorine-doped porous carbon substrate. The fluorine content gradually decreases from the surface layer to the interior of the fluorine-doped porous carbon substrate. The X-ray photoelectron spectroscopy (XPS spectrum) of the F element has characteristic peaks at 687.2±0.1eV and 685.5±0.1eV.

[0007] The mass percentage of carbon in the phosphorus-carbon composite material is 20-40%, the mass percentage of phosphorus is 40-60%, and the mass percentage of fluorine is 2-7%.

[0008] The phosphorus-carbon composite material can be in the form of powder, bulk, fiber, etc., and the powder has a median particle size of 1-10 μm.

[0009] Further, the porous carbon material is selected from at least one of spherical activated carbon, activated carbon fiber, mesoporous carbon, carbon nanotube, carbon molecular sieve, carbon aerogel, carbon nanocage, porous carbon microsphere, columnar activated carbon, granular activated carbon, powdered activated carbon, expanded graphite, porous graphite, MOFs material, and biomass carbon.

[0010] Further, the specific surface area of the porous carbon material is 800-1500 m 2 / g, and the pores include micropores, mesopores, and macropores; the micropores have a pore size distribution of >0-2 nm, the mesopores have a pore size distribution of >2-50 nm, and the macropores have a pore size of >50 nm.

[0011] Further, the elemental phosphorus is selected from red phosphorus, white phosphorus, purple phosphorus, and black scale. The elemental phosphorus is uniformly confined in the pores of the porous carbon to form a uniformly distributed composite structure.

[0012] The application also provides a preparation method of the fluorine-doped phosphorus-carbon composite negative electrode material.

[0013] (1) placing the porous carbon in the downstream of a double-temperature-zone heating furnace (the lower gas outlet of the double-temperature-zone tube furnace), placing a fluorine source in the upstream (the upper gas inlet of the double-temperature-zone tube furnace), heating the upstream to 700-1000 ℃ under an inert atmosphere, and heating the downstream to 400-600 ℃, and keeping the temperature for 1-5 h, and then cooling to room temperature to obtain the fluorine-doped porous carbon material;

[0014] (2) adding the fluorine-doped porous carbon material and elemental phosphorus into a sealed reactor, heating to 420-600 ℃ under vacuum, keeping the temperature for 5-30 h, and then naturally cooling to condense and deposit, and then heating to 280-400 ℃ for the second time, keeping the temperature for 10-40 h, and then naturally cooling to obtain the fluorine-doped phosphorus-carbon composite material.

[0015] Further, in steps (1) and (2), the heating rate is independently 1-20 ℃ / min, preferably 5-10 ℃ / min; and in step (2), the vacuum degree is 0.01-10 Pa.

[0016] Further, in step (1), the mass ratio of the porous carbon to the fluorine source is 1:5-10; and in step (S2), the mass ratio of the fluorine-doped porous carbon material to the elemental phosphorus is 1:2-4.

[0017] Further, the fluorine source is selected from at least one of a fluorine-containing polymer and a fluorine-containing small molecule; the fluorine-containing polymer is selected from at least one of a fluorine-containing polyimide, a perfluoropolyether (PFPE), a polyvinylidene fluoride (PVDF), an AFLAS fluororubber, a polychlorotrifluoroethylene, a fluorinated ethylene propylene copolymer, a tetrafluoroethylene and hexafluoropropylene copolymer, a polyhexafluoroisobutylene, a polyhexafluoropropylene, a polytetrafluoroethylene, a perfluoroalkoxyethylene polymer, a poly(2,2,3,3,3-pentafluoropropyl acrylate), a poly(1,1,1,3,3,3-hexafluoroisopropyl acrylate), a poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate), and a poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate); and the fluorine-containing small molecule is selected from at least one of an ammonium fluoride, a calcium fluoride, and a lanthanum fluoride.

[0018] Preferably, the fluorine source is a compound of the fluorine-containing polymer and the fluorine-containing small molecule in a mass ratio of 1-3:1. The inventors unexpectedly found that fluorine doping using a fluorine source compounded from a polymer and a small molecule can effectively increase the amount of fluorine doping, and the fluorine-containing polymer is preferentially decomposed at low temperature to form fluoride or fluorine gas for fluorination of the carbon material; when the temperature increases, the fluorine-containing small molecule begins to decompose to form fluoride or fluorine gas for fluorination of the carbon material, and gradient fluorination is beneficial to fluorine doping from the surface to the inside of the carbon material, effectively increasing the amount of fluorine doping and reducing the decreasing trend of fluorine content from the surface to the inside of the material, thereby achieving uniform doping of fluorine.

[0019] The application also provides application of the phosphorus-carbon composite material prepared by the above method as a negative electrode material in a sodium ion battery, and the prepared sodium battery has high first coulomb efficiency, high reversible capacity, and excellent cycle stability.

[0020] Compared with the prior art, the phosphorus-carbon composite material for sodium ion batteries and the preparation method thereof have the advantages that the phosphorus-carbon composite material for sodium ion batteries prepared by the method is composed of elemental phosphorus and a porous carbon substrate, and the porous carbon is composed of carbon and carbon fluoride. By introducing fluorine atoms into the porous carbon, the fluorine atoms successfully construct a polar interface (C-F) on the surface of the material; by using a gradient fluorination strategy, i.e., mixing fluorine-containing polymers and fluorine-containing small molecules, the fluorine incorporation amount is effectively increased, and the fluorine content decreases from the surface to the interior of the material, so that uniform fluorine incorporation is achieved. Finally, by depositing phosphorus, a stable C-F-P structure is formed, the pores of the porous carbon can effectively buffer the volume expansion of phosphorus, the C-F-P structure can improve the interaction force between phosphorus and the carbon substrate, effectively improve the adsorption of sodium polyphosphates of the material, inhibit the dissolution and shuttle of sodium polyphosphates in the cycle process, and thus improve the cycle performance of the material. Preferably, a double-temperature-zone heating furnace is used, fluorine-containing polymers are placed in the upstream of the heating furnace, and porous carbon materials are placed in the downstream of the heating furnace, so that the fluorine-containing active ingredients can react with the porous carbon under more safe and gentle conditions to form a continuous composite structure of carbon fluoride and carbon. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 X-ray diffraction spectrum (XRD) of the phosphorus-carbon composite material prepared in Example 1.

[0022] Figure 2 F element photoelectron spectrum (XPS) of the phosphorus-carbon composite material prepared in Example 1.

[0023] Figure 3 Scanning electron microscope (SEM) photograph of the phosphorus-carbon composite material prepared in Example 1.

[0024] Figure 4 Transmission electron microscope (TEM) photograph of the phosphorus-carbon composite material prepared in Example 1.

[0025] Figure 5 Element distribution map (Mapping) of the phosphorus-carbon composite material prepared in Example 1.

[0026] Figure 6 Charge-discharge curve of the phosphorus-carbon composite material prepared in Example 1 as a negative electrode of a sodium ion battery.

[0027] Figure 7 Cycle performance curve of the phosphorus-carbon composite material prepared in Example 1 as a negative electrode of a sodium ion battery. DETAILED DESCRIPTION

[0028] The application will be further described in conjunction with specific examples, but the application is not limited to the following examples.

[0029] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0030] The porous carbon has a median particle size of 8 μm and a specific surface area of 1800 ± 100 m 2 / g, and the pores include micropores, mesopores, and macropores.

[0031] Example 1

[0032] (1) Powdered porous carbon particles having a median particle size of 8 μm were placed in the downstream of a dual-temperature zone heating furnace, and polyvinylidene fluoride was placed in the upstream, with the mass ratio of the powdered porous carbon particles to the polyvinylidene fluoride being 1:10. Under an inert atmosphere, the upstream was heated to 800°C at a heating rate of 10°C / min -1 , and at the same time, the downstream was heated to 500°C at a heating rate of 10°C / min -1 . After 3 h of heat preservation, the carbon and fluorocarbon composite porous carbon material was obtained after cooling to room temperature.

[0033] (2) The fluorine-doped porous carbon material and red phosphorus described above were mixed by stirring at a mass ratio of 1:2.5 for 30 min to obtain uniformly mixed raw materials, and the raw materials were placed in a sealed reactor with a vacuum degree of 1 Pa and heated to 450°C at a heating rate of 5°C / min for 20 h of heat preservation. After natural cooling and condensation deposition, the temperature was cooled to room temperature, and then a second heating was performed at a heating rate of 2°C / min to a heating temperature of 300°C for 30 h of heat preservation. After natural cooling, the fluorine-doped phosphorus-carbon composite material was obtained. TEM-EDS energy spectrum testing showed that the mass percentage of fluorine was 3.25%, and the results are shown in Table 1.

[0034] Table 1 Element Content Test

[0035] Element Line type k factor Absorption correction wt% C K line system 2.781 1.00 35.73 O K line system 2.028 1.00 2.28 F K line system 1.728 1.00 3.25 P K line system 1.056 1.00 58.74 Total amount 100.00

[0036] Figure 1 Figure 1 is an XRD diffraction pattern of the phosphorus-carbon composite material obtained in Example 1. As can be seen, there are obvious phosphorus diffraction peaks, and there are no other impurity peaks.

[0037] Figure 2 Figure 2 is an XPS graph of the carbon and fluorocarbon composite porous carbon material obtained in Example 1. As can be seen from the figure, the porous carbon material contains C-F and F-P chemical structures.

[0038] Figure 3 Figure 3 is an SEM graph of the phosphorus-carbon composite material obtained in Example 1. As can be seen from the figure, the composite material is blocky, the surface is dense, and the particle size is uniform, with a particle size range of 1-10 μm.

[0039] Figure 4is a TEM image of the phosphorus-carbon composite material obtained in Example 1. As can be seen from the figure, the phosphorus is uniformly distributed in the composite material, and the carbon and carbon fluoride composite structure has the characteristics of being continuous and dense.

[0040] Figure 5 is a Mapping image of the phosphorus-carbon composite material obtained in Example 1. As can be seen from the figure, the carbon, fluorine, and phosphorus are uniformly distributed in the composite material.

[0041] The phosphorus-carbon composite material obtained in the application was subjected to electrochemical analysis test, and the results are shown in Figure 6 and Figure 7 . The charge and discharge interval is 0.005-2.0V, the compacted density is 1.5g cm -3 , and the current density is 160mA g -1 (0.1C) during charging and discharging, which proves that the composite material obtained in the application has excellent cycle performance.

[0042] Example 2

[0043] The other conditions are the same as in Example 1, except that:

[0044] In step (1), the upstream is heated to 1000℃, and the downstream is heated to 400℃.

[0045] Example 3

[0046] The other conditions are the same as in Example 1, except that in step (1), the mass ratio of the powdery porous carbon particles to the fluorine source is 1:5, and in step (2), the mass ratio of the fluorine-doped porous carbon material to red phosphorus is 1:2.

[0047] Example 4

[0048] The other conditions are the same as in Example 1, except that in step (2), the mass ratio of the fluorine-doped porous carbon material to red phosphorus is 1:4.

[0049] Example 5

[0050] The other conditions are the same as in Example 1, except that in step (1), polyhexafluoropropylene is used instead of polyvinylidene fluoride.

[0051] Example 6

[0052] The other conditions are the same as in Example 1, except that in step (1), a mixture of polyvinylidene fluoride and polyhexafluoropropylene with a mass ratio of 1:1 is used instead of polyvinylidene fluoride.

[0053] Example 7

[0054] The other conditions are the same as in Example 1, except that in step (1), a mixture of polyvinylidene fluoride and calcium fluoride with a mass ratio of 1:1 is used instead of polyvinylidene fluoride.

[0055] Example 8

[0056] Other conditions are the same as Example 1, except that polyvinylidene fluoride is replaced by a mixture of polyvinylidene fluoride and ammonium fluoride with a mass ratio of 3:1 in step (1).

[0057] Example 9

[0058] Other conditions are the same as Example 1, except that polyvinylidene fluoride is replaced by calcium fluoride in step (1).

[0059] Comparative Example 1

[0060] The phosphorus-carbon composite material described in the application is prepared according to the same method as Example 1, except that the fluorination treatment in step (1) is omitted and the porous carbon is directly subjected to the phosphorus-carbon in step (2).

[0061] Comparative Example 2

[0062] Other conditions are the same as Example 1, except that the powdered porous carbon in step (1) is mixed with fluorinated carbon, and the carbon and fluorinated carbon composite porous carbon material is obtained by ball milling, and the F content in the final product is close to 1:1.

[0063] Application Example

[0064] The electrochemical performance of the phosphorus-carbon composite materials prepared in the following examples and comparative examples is tested according to the following method: the prepared phosphorus-carbon composite material, carbon black and carboxymethyl cellulose (CMC) are mixed with a mass ratio of 8:1:1 to form a slurry (wherein the mass ratio of CMC and SBR is 2:3), the slurry is uniformly coated on a copper foil current collector, and after vacuum drying for 12h, a working electrode is prepared; sodium sheet is used as a counter electrode, glass fiber membrane is used as a separator, 1mol L -1 NaPF6(solvent is a mixture of ethylene carbonate and dimethyl carbonate with a volume ratio of 1:1) is used as an electrolyte, and 5% VC (ethylene carbonate) and 5% FEC (fluoroethylene carbonate) are added to the electrolyte, and a button cell is assembled in an argon atmosphere glove box.

[0065] The above assembled battery is subjected to charge-discharge test on a LAND charge-discharge tester. The results are shown in Table 2.

[0066] Table 2 Electrochemical performance test results of phosphorus-carbon composite materials

[0067]

Claims

1. A fluorine-doped phosphorus-carbon composite negative electrode material, characterized by, The fluorine-doped porous carbon substrate is composed of elemental phosphorus and fluorine, and the fluorine content gradually decreases from the surface layer to the interior of the fluorine-doped porous carbon substrate. The X-ray photoelectron spectroscopy of the F element has characteristic peaks of 687.2±0.1eV and 685.5±0.1eV.

2. The fluorine-doped phosphorus-carbon composite negative electrode material according to claim 1, characterized in that, The mass percentage of carbon is 20-40%, the mass percentage of phosphorus is 40-60%, and the mass percentage of fluorine is 2-7% in the total mass of 100% of the phosphorus-carbon composite material.

3. The fluorine-doped phosphorus-carbon composite negative electrode material of claim 1, wherein, The phosphorus-carbon composite material is in the form of powder, bulk or fiber, and the median particle size of the powder is 1-10 µm.

4. The fluorine-doped phosphorus-carbon composite negative electrode material of claim 1, wherein, The porous carbon material is selected from at least one of spherical activated carbon, activated carbon fiber, mesoporous carbon, carbon nanotube, carbon molecular sieve, carbon aerogel, carbon nanocage, porous carbon microsphere, columnar activated carbon, granular activated carbon, powdered activated carbon, expanded graphite, porous graphite, MOFs material, and biomass carbon.

5. The fluorine-doped phosphorus-carbon composite negative electrode material of claim 1, wherein, The porous carbon material has a specific surface area of 800-1500 m 2 / g, the pores include micropores, mesopores, and macropores; the micropores have a pore size distribution of >0 to 2 nm, the mesopores have a pore size distribution of >2 to 50 nm, and the macropores have a pore size of >50 nm.

6. The fluorine-doped phosphorus-carbon composite negative electrode material of claim 1, wherein, The elemental phosphorus is selected from red phosphorus, white phosphorus, purple phosphorus, and black scale.

7. The method for preparing the fluorine-doped phosphorus-carbon composite negative electrode material according to any one of claims 1-6, characterized in that, The method comprises the following steps: (1) placing the porous carbon in the downstream of a double-temperature zone heating furnace, placing a fluorine source in the upstream, heating the upstream to 700-1000 ℃ under an inert atmosphere, and maintaining the temperature for 1-5 h, heating the downstream to 400-600 ℃, and maintaining the temperature for 1-5 h, and then cooling to room temperature to obtain the fluorine-doped porous carbon material; (2) adding the fluorine-doped porous carbon material and elemental phosphorus into a sealed reactor, heating to 420-600 ℃ under vacuum, maintaining the temperature for 5-30 h, and then naturally cooling for condensation and deposition, and then heating to 280-400 ℃ for the second time when the temperature cools to room temperature, maintaining the temperature for 10-40 h, and then naturally cooling to obtain the fluorine-doped phosphorus-carbon composite material.

8. The preparation method according to claim 7, characterized in that, In steps (1) and (2), the heating rate is independently 1-20 ℃ / min; in step (2), the vacuum degree is 0.01-10 Pa; the mass ratio of the porous carbon to the fluorine source is 1:5-10; and in step (S2), the mass ratio of the fluorine-doped porous carbon material to the elemental phosphorus is 1:2-4.

9. The preparation method according to claim 8, characterized in that, In steps (1) and (2), the heating rate is independently 5-10 ℃ / min.

10. The method of claim 7, wherein, The fluorine source is selected from at least one of fluorine-containing polymer and fluorine-containing small molecule; the fluorine-containing polymer is selected from at least one of fluorine-containing polyimide, perfluoropolyether, polyvinylidene fluoride, vinylidene fluoride fluororubber, polychlorotrifluoroethylene, fluorinated ethylene propylene copolymer, tetrafluoroethylene and hexafluoropropylene copolymer, polyhexafluoroisopropylene, polyhexafluoropropylene, polytetrafluoroethylene, perfluoroalkoxyethylene polymer, poly(2,2,3,3,3-pentafluoropropyl acrylate), poly(1,1,1,3,3,3-hexafluoroisopropyl acrylate), poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate), and poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate); and the fluorine-containing small molecule is selected from at least one of ammonium fluoride, calcium fluoride, and lanthanum fluoride.

11. The method of claim 10, wherein, The fluorine source is a compound of fluorine-containing polymer and fluorine-containing small molecule with a mass ratio of 1-3:

1.

12. Use of the phosphorus-carbon composite material of any one of claims 1-6 or the phosphorus-carbon composite material prepared by the method of any one of claims 7-11 as an anode material for preparing a sodium-ion battery anode.

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