Iron-based porous carbon sodium-ion battery composite negative electrode material and preparation method thereof

Abstract

The application discloses a kind of iron-based porous carbon sodium ion battery composite negative materials and preparation method thereof, the composite negative material includes porous carbon skeleton, iron-based nanoparticle is composited in the inside of porous carbon skeleton, and the outside of porous carbon skeleton is coated with hard carbon layer, iron-based nanoparticle is one or two or more above in Fe2O3, Fe3O4, FeS2, FeS, FeSe2, FeP;Its preparation method includes the following steps: S1, the preparation of iron-based porous carbon skeleton composite material, S2, the preparation of surface-coated iron-based porous carbon skeleton composite material, S3, high-temperature sintering.The iron-based porous carbon sodium ion battery composite negative material and preparation method thereof of the application have the characteristics of good uniformity, high specific capacity and long cycle life.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion batteries, in particular to an iron-based porous carbon sodium ion battery composite negative electrode material and a preparation method thereof. BACKGROUND

[0002] Due to the advantages of rich resources, sodium ion batteries, as a low-cost alternative to lithium ion batteries, have rapidly developed in recent years. The negative electrode plays a decisive role in the energy density and cycle performance of the sodium ion battery system. Among the many sodium storage negative electrode materials, the hard carbon negative electrode has low cost and good cycle performance, and has strong application potential, but the low specific capacity limits the further improvement of the energy density of the sodium ion battery.

[0003] In contrast, the iron-based negative electrode material has high specific capacity, rich raw materials and low cost, but the electronic conductivity of the material is poor, and the volume expansion during the sodium process is serious, which leads to easy pulverization and agglomeration during the cycle process, resulting in poor cycle performance and rate performance.

[0004] In addition, the material particle pulverization leads to the instability of the electrode / electrolyte interface, and the repeated formation and destruction of the solid electrolyte (SEI) on the electrode surface leads to the continuous loss of active sodium, which further reduces the capacity. SUMMARY

[0005] The purpose of the present application is to provide an iron-based porous carbon sodium ion battery composite negative electrode material and a preparation method thereof, which has the characteristics of good uniformity, high specific capacity and long cycle life.

[0006] The present application can be realized by the following technical solutions:

[0007] The application discloses an iron-based porous carbon sodium ion battery composite negative electrode material, which comprises a porous carbon framework, iron-based nanoparticles are compounded in the porous carbon framework, a hard carbon layer is coated on the outside of the porous carbon framework, and the iron-based nanoparticles are one or two or more of Fe2O3, Fe3O4, FeS2, FeS, FeSe2 and FeP. In the present application, the reserved buffer space can buffer the volume change of the iron-based nanoparticles during the charging and discharging process, and ensure the structural stability.

[0008] Further, the iron-based nanoparticles are filled in the porous carbon framework, the particle size of the iron-based nanoparticles is 0.8-45 nm, and the nanoparticles are filled in the micropores or mesopores in the porous carbon framework.

[0009] Further, the iron-based nanoparticles account for 60-90% of the total pore volume of the porous carbon framework, and the remaining unfilled pores are reserved buffer spaces.

[0010] Further, the average pore size of the mesopores or micropores in the porous carbon framework is 0.8-50 nm, the porosity is 30-60%, and the specific surface area is 1000-3000 m 2 g -1 .

[0011] Another aspect of the present application is to protect the preparation method of the above-mentioned iron-based porous carbon sodium ion battery composite anode material, comprising the following steps:

[0012] S1, preparation of iron-based porous carbon framework composite material: using a chemical vapor deposition system for processing, heating the porous carbon framework, introducing carrier gas and heteroatom-containing gas to bring pyrolytic iron source to deposit inside the porous carbon framework, and the iron source and heteroatom-containing gas pyrolyze to form iron-based nanoparticles in the pores of the porous carbon framework, to obtain an iron-based porous carbon framework composite material;

[0013] S2, preparation of surface-coated iron-based porous carbon framework composite material: switching the gas path of the vapor deposition system, heating the porous carbon framework, introducing carrier gas to bring pyrolytic carbon source to deposit on the surface of the iron-based porous carbon framework composite material, to obtain a surface-coated iron-based porous carbon framework composite material;

[0014] S3, high-temperature sintering: the surface-coated iron-based porous carbon framework composite material obtained in step S2 is subjected to high-temperature sintering to obtain the final anode material.

[0015] In the preparation of the iron-based porous carbon framework composite material in step S1, the carrier gas brings the pyrolytic iron source to the porous carbon region, and the pyrolytic iron source is adsorbed in the pores of the porous carbon and decomposes to form iron oxide under the catalytic action of the pore wall; when the heteroatom-containing gas is present, the pyrolytic iron source reacts with it at high temperature to form iron-based nanoparticles such as iron sulfide, iron phosphide, and iron selenide. The preparation conditions of this step will affect the deposition effect of the iron-based nanoparticles. Specifically, increasing the deposition temperature and prolonging the deposition time will increase the deposition amount of the iron-based material. If the deposition temperature is too low, a longer deposition time is needed, increasing the production cost; if the deposition temperature is too high, the pyrolytic iron source is easily decomposed and deposited on the surface of the porous carbon framework, and cannot be deposited in the pores, which does not achieve the purpose of the present application. Too low deposition amount will affect the specific capacity of the composite material, and too high deposition amount will lead to a lack of pores in the composite material, which does not achieve the purpose of buffering the volume expansion of the iron-based material. The preparation conditions need to be considered comprehensively to ensure that the filling degree of the porous carbon pores is at an appropriate level.

[0016] In the preparation process of the surface-coated iron-based porous carbon skeleton composite material in step S2, the preparation conditions will affect the coating effect of the carbon layer. Specifically, higher deposition temperature and longer deposition time will increase the coating amount of the carbon layer. Too high deposition amount will reduce the specific capacity of the composite material, and too thin coating layer cannot form a complete coating layer, which cannot achieve the purpose of isolating the iron-based nanoparticles from contacting the electrolyte.

[0017] In the high-temperature sintering process of step S3, the purpose of high-temperature sintering is to graphitize the coated carbon layer, increase the density of the carbon layer, reduce the porosity, and make the carbon atoms in the coated carbon layer and the base material more closely rearranged and combined at high temperature. The sintering temperature cannot be higher than the boiling point of the iron-based material.

[0018] Further, in step S1, the carrier gas is nitrogen and / or argon, the carrier gas flow rate is 20-300 Sccm, the deposition temperature is 300-800℃, and the deposition time is 0.2-3 h; the heteroatom-containing gas is one or more of H2S, PH3, and H2Se.

[0019] Further, in step S1, the pyrolysis iron source is one or more of ferrocene, iron phthalocyanine, ferrous gluconate, ferrous fumarate, and iron citrate.

[0020] Further, in step S2, the carrier gas is nitrogen and / or argon, the carrier gas flow rate is 20-300 Sccm, the deposition temperature is 400-1000℃, and the deposition time is 0.2-1 h.

[0021] Further, in step S2, the pyrolysis carbon source is one or more of benzene, toluene, trimethylbenzene, acetylene, ethanol, formaldehyde, thiophene, pyridine, and / or sulfide.

[0022] Further, in step S3, the high-temperature sintering conditions are: the heating rate is 0.5-10℃ / min, the sintering temperature is 500-1600℃, and the sintering time is 1-5 h.

[0023] The iron-based porous carbon sodium ion battery composite negative electrode material and the preparation method thereof have the following beneficial effects:

[0024] In the negative electrode material of the present application, the porous carbon skeleton is used as the base, and the carbon material is used as the buffer base material, which can inhibit particle agglomeration, relieve volume expansion, and provide a conductive network, fully exerting the basic characteristics of the long-cycle stability of the hard carbon material; by compounding the iron-based nanoparticles, the high specific capacity advantage thereof is exerted; by coating the hard carbon layer, the specific surface area of the porous carbon is reduced, the irreversible decomposition of the electrolyte is inhibited, and the first-cycle coulombic efficiency of the hard carbon material is improved. DETAILED DESCRIPTION

[0025] In order for those skilled in the art to better understand the technical solutions of the present application, the product of the present application is further described in detail below in combination with embodiments.

[0026] The application discloses a kind of iron-based porous carbon sodium ion battery composite negative electrode material, including porous carbon framework, iron-based nanoparticle is composited in the inside of porous carbon framework, porous carbon framework is coated with hard carbon layer outside, iron-based nanoparticle is one or two or more above in Fe2O3, Fe3O4, FeS2, FeS, FeSe2, FeP.

[0027] Further, the mode that iron-based nanoparticle is composited in porous carbon framework is filling, the particle size of iron-based nanoparticle is 0.8-45 nm, and the nanoparticle is filled in micropore or mesopore in the inside of porous carbon framework.

[0028] Further, iron-based nanoparticle accounts for 60-90% of the total pore volume of porous carbon framework, and the remaining unfilled pore is reserved buffer space.

[0029] Further, in porous carbon framework, the average pore size of mesopore or micropore is 0.8-50 nm, the porosity is 30-60%, and the specific surface area is 1000-3000 m 2 g -1 .

[0030] Another aspect of the present application is to protect the preparation method of the above-mentioned iron-based porous carbon sodium ion battery composite negative electrode material, comprising the following steps:

[0031] S1, preparation of iron-based porous carbon framework composite material: using chemical vapor deposition system to process, heating porous carbon framework, introducing carrier gas and heteroatom-containing gas to bring pyrolysis iron source to make it deposit in the inside of porous carbon framework, and iron source and heteroatom-containing gas are pyrolyzed to form iron-based nanoparticles in the pores of porous carbon framework, to obtain iron-based porous carbon framework composite material;

[0032] S2, preparation of surface-coated iron-based porous carbon framework composite material: switching gas phase deposition system gas path, heating porous carbon framework, introducing carrier gas to bring pyrolysis carbon source to make it deposit on the surface of iron-based porous carbon framework composite material, to obtain surface-coated iron-based porous carbon framework composite material;

[0033] S3, high-temperature sintering: the surface-coated iron-based porous carbon framework composite material obtained in step S2 is subjected to high-temperature sintering to obtain the final negative electrode material.

[0034] Further, in step S1, the carrier gas is nitrogen and / or argon, the carrier gas flow rate is 20-300 Sccm, the deposition temperature is 300-800℃, and the deposition time is 0.2-3 h; the heteroatom-containing gas is one or more of H2S, PH3, and H2Se.

[0035] Further, in step S1, the pyrolysis iron source is one or more of ferrocene, iron phthalocyanine, ferrous gluconate, ferrous fumarate, and iron citrate.

[0036] Further, in step S2, the carrier gas is nitrogen and / or argon, the carrier gas flow rate is 20-300 Sccm, the deposition temperature is 400-1000℃, and the deposition time is 0.2-1 h.

[0037] Further, in step S2, the pyrolysis carbon source is one or more of benzene, toluene, mesitylene, acetylene, ethanol, formaldehyde, thiophene, pyridine, and / or a sulfide.

[0038] Further, in step S3, the high-temperature sintering conditions are: a heating rate of 0.5-10℃ / min, a sintering temperature of 500-1600℃, and a sintering time of 1-5 h. Embodiment

[0039] This embodiment relates to an iron-based porous carbon sodium-ion battery composite negative electrode material, and a preparation method thereof, which comprises the following steps:

[0040] S1, preparation of an iron-based porous carbon skeleton composite material: using a chemical vapor deposition system for processing, adjusting the gas path of the chemical vapor deposition system, and connecting the iron source gas path to the system. The average pore size of the porous carbon is 2.5 nm, and the specific surface area is 1800 m 2 / g. The porous carbon skeleton material is placed in a tube furnace, the iron source is ferrocene, nitrogen gas is introduced as a carrier gas, the carrier gas flow rate is 100 Sccm, the deposition temperature is 500℃, and the deposition time is 2.5 h, to obtain a Fe2O3@ porous carbon skeleton composite material.

[0041] S2, chemical vapor deposition: switching the vapor deposition gas path, heating the porous carbon skeleton to 450℃, introducing nitrogen gas to bring in an ethylene carbon source, the carrier gas nitrogen flow rate is 100 Sccm, and the deposition time is 30 min, to obtain a surface-coated iron-based porous carbon skeleton composite material.

[0042] S3, high-temperature sintering: the surface-coated iron-based porous carbon skeleton composite material obtained in step S2 is subjected to high-temperature sintering, heated to 1300 o C at a heating rate of 2 o C / min in a nitrogen gas atmosphere, and kept at 2 h to obtain the final negative electrode material.

[0043] The obtained material was subjected to electrochemical performance test according to the following method: the hard carbon material, Super P, CMC and SBR were mixed into a homogenate at a mass ratio of 94:1.5:2:2.5, then the black slurry was coated on a copper foil using a 120 um four-side preparation device, and then the film was dried in a 100℃ vacuum drying oven for 2 hours. The electrode film was punched into a circular sheet with a radius of 0.6 mm using a sheet puncher, and a metal sodium was used as a counter electrode, 1 mol / L NaClO4 EC+DEC (1:1 vol%) was used as an electrolyte, and a PP / PE / PP three-layer separator was used as a separator to assemble a CR2016 type button cell in a glove box. The above button cell was subjected to constant current charge and discharge test, the current density was 0.1C (1C=300 mAh / g), and the voltage range was 2-0.005 V.

[0044] The first cycle reversible specific capacity of the iron-based composite electrode in Example 1 was 377 mAh / g, showing a high sodium storage capacity. The capacity of the iron-based composite electrode in Example 1 remained as high as 85% after 1000 cycles, showing good cycle stability. The reason for the high cycle stability of Example 1 is that the iron-based nanometer iron nanoparticles have a small size, the volume expansion during sodiumization is limited, and the hard porous carbon skeleton material serves as an electronic transmission network to transmit electrons and can buffer the volume expansion of the alloy iron-based nanoparticles; on the other hand, the surface coated carbon layer effectively isolates the alloy from contact with the electrolyte, improving the cycle stability of the electrode / interface. Example

[0045] This embodiment relates to an iron-based porous carbon sodium ion battery composite negative electrode material, and a preparation method thereof, which comprises the following steps:

[0046] S1, preparation of iron-based porous carbon skeleton composite material: using a chemical vapor deposition system for treatment, adjusting the gas path of the chemical vapor deposition system, and connecting the iron source gas path to the system. The average pore size of the porous carbon is 2.5 nm, and the specific surface area is 1800 m 2 / g. The porous carbon skeleton material was placed in a tube furnace, the iron source was ferrocene, nitrogen gas was introduced as a carrier gas at a flow rate of 100 Sccm, and hydrogen sulfide gas was introduced at the same time, the deposition temperature was 500℃, the deposition time was 2 h, and the FeS@ porous carbon skeleton composite material was obtained.

[0047] S2, chemical vapor deposition: switching the vapor deposition gas path, heating the porous carbon skeleton to 450℃, introducing nitrogen gas to bring in ethylene carbon source, the carrier gas nitrogen flow rate is 100 Sccm, the deposition time is 30 min, and the surface coated FeS@ porous carbon skeleton composite material is obtained.

[0048] S3, high-temperature sintering: the surface-coated FeS@porous carbon framework composite material obtained in step S2 is subjected to high-temperature sintering, and is heated to 1300 o C at a heating rate of 2 o C / min in a nitrogen gas atmosphere, and is kept at 1300

[0049] The obtained material is subjected to electrochemical performance testing according to the following method: hard carbon material, Super P, CMC, and SBR are mixed into a slurry at a mass ratio of 94:1.5:2:2.5, and the black slurry is coated on a copper foil using a 120-um four-side coater, and the film is dried in a 100°C vacuum drying box for 2 hours. The electrode film is punched into a circular sheet with a radius of 0.6 mm using a sheet puncher, and a CR2016 type button cell is assembled in a glove box using metallic sodium as the counter electrode, 1 mol / L NaClO4 EC+DEC (1:1 vol%) as the electrolyte, and a PP / PE / PP three-layer separator. The above button cell is subjected to constant-current charge and discharge testing, the current density is 0.1C (1C=300 mAh / g), and the voltage range is 2-0.005 V.

[0050] The first-cycle reversible specific capacity of the iron-based composite electrode in Example 2 is 402 mAh / g, and the iron-based composite electrode in Example 2 has a high capacity retention of 83.2% after 1000 cycles, and has good cycle stability. Example

[0051] The present embodiment discloses an iron-based porous carbon sodium ion battery composite negative material, which comprises a porous carbon framework, iron-based nanoparticles are compounded in the interior of the porous carbon framework, a hard carbon layer is coated on the exterior of the porous carbon framework, and the iron-based nanoparticles are Fe2O3 and Fe3O4.

[0052] In the present embodiment, the iron-based nanoparticles are filled in the porous carbon framework, the particle size of the iron-based nanoparticles is 0.8-45 nm, and the nanoparticles are filled in the micropores or mesopores in the interior of the porous carbon framework. The iron-based nanoparticles account for 60-90% of the total pore volume of the porous carbon framework, and the remaining unfilled pores are reserved as buffer spaces. In the porous carbon framework, the average pore size of the mesopores or micropores is 0.8-50 nm, the porosity is 30-60%, and the specific surface area is 1000-3000 m 2 g -1 .

[0053] The present embodiment discloses a preparation method of an iron-based porous carbon sodium ion battery composite negative material, which comprises the following steps:

[0054] S1, preparation of the iron-based porous carbon framework composite: using a chemical vapor deposition system to process, heating the porous carbon framework, introducing carrier gas and heteroatom-containing gas to bring the pyrolysis iron source to deposit inside the porous carbon framework, the iron source and the heteroatom-containing gas pyrolyze to form iron-based nanoparticles in the pores of the porous carbon framework, to obtain the iron-based porous carbon framework composite;

[0055] S2, preparation of the surface-coated iron-based porous carbon framework composite: switching the gas path of the vapor deposition system, heating the porous carbon framework, introducing carrier gas to bring the pyrolysis carbon source to deposit on the surface of the iron-based porous carbon framework composite, to obtain the surface-coated iron-based porous carbon framework composite;

[0056] S3, high-temperature sintering: the surface-coated iron-based porous carbon framework composite obtained in step S2 is subjected to high-temperature sintering to obtain the final negative electrode material.

[0057] In this embodiment, in step S1, the carrier gas is inert gas, the inert gas is nitrogen, the carrier gas flow rate is 300 Sccm, the deposition temperature is 600℃, and the deposition time is 0.2h; the heteroatom-containing gas is H2S; the pyrolysis iron source is ferrocene, iron phthalocyanine.

[0058] In this embodiment, in step S2, the carrier gas is nitrogen, the carrier gas flow rate is 300 Sccm, the deposition temperature is 700℃, and the deposition time is 0.2h; the pyrolysis carbon source is benzene, toluene.

[0059] In this embodiment, in step S3, the high-temperature sintering conditions are: the heating rate is 10℃ / min, the sintering temperature is 1100℃, and the sintering time is 1h. Embodiment

[0060] This embodiment discloses an iron-based porous carbon sodium ion battery composite negative electrode material, which comprises a porous carbon framework, iron-based nanoparticles are compounded inside the porous carbon framework, a hard carbon layer is coated outside the porous carbon framework, and the iron-based nanoparticles are Fe2O3 and FeSe2.

[0061] In this embodiment, the iron-based nanoparticles are filled in the porous carbon framework, the particle size of the iron-based nanoparticles is 0.8-45 nm, the iron-based nanoparticles of the nanoparticles are filled in the micropores or mesopores inside the porous carbon framework, the iron-based nanoparticles account for 60-90% of the total pore volume of the porous carbon framework, and the remaining unfilled pores are reserved buffer spaces. In the porous carbon framework, the average pore size of the mesopores or micropores is 0.8-50 nm, the porosity is 30-60%, the specific surface area is 1000-3000 m 2 g -1 .

[0062] The preparation method of the iron-based porous carbon sodium ion battery composite negative electrode material of the embodiment comprises the following steps:

[0063] S1, preparation of an iron-based porous carbon framework composite material: a chemical vapor deposition system is used for processing, the porous carbon framework is heated, carrier gas and heteroatom-containing gas are introduced to bring pyrolytic iron sources to deposit inside the porous carbon framework, the iron sources and the heteroatom-containing gas are pyrolyzed to form iron-based nanoparticles in the pores of the porous carbon framework, and an iron-based porous carbon framework composite material is obtained;

[0064] S2, preparation of a surface-coated iron-based porous carbon framework composite material: the gas path of the vapor deposition system is switched, the porous carbon framework is heated, carrier gas is introduced to bring pyrolytic carbon sources to deposit on the surface of the iron-based porous carbon framework composite material, and a surface-coated iron-based porous carbon framework composite material is obtained;

[0065] S3, high-temperature sintering: the surface-coated iron-based porous carbon framework composite material obtained in step S2 is subjected to high-temperature sintering to obtain a final negative electrode material.

[0066] In the embodiment, in step S1, the carrier gas is argon, the carrier gas flow rate is 150 Sccm, the deposition temperature is 300°C, and the deposition time is 3 h; the heteroatom-containing gas is H2Se; and the pyrolytic iron source is ferrous fumarate or iron citrate.

[0067] In the embodiment, in step S2, the carrier gas is argon, the carrier gas flow rate is 200 Sccm, the deposition temperature is 400°C, and the deposition time is 1 h; and the pyrolytic carbon source is trimethylbenzene or acetylene.

[0068] In the embodiment, in step S3, the high-temperature sintering conditions are as follows: the temperature rising rate is 8°C / min, the sintering temperature is 500°C, and the sintering time is 5 h. Embodiment

[0069] The embodiment discloses an iron-based porous carbon sodium ion battery composite negative electrode material, which comprises a porous carbon framework, iron-based nanoparticles are compounded inside the porous carbon framework, a hard carbon layer is coated outside the porous carbon framework, and the iron-based nanoparticles are Fe2O3, Fe3O4, FeS2, FeS, FeSe2, or FeP.

[0070] The preparation method of the iron-based porous carbon sodium ion battery composite negative electrode material of the embodiment comprises the following steps:

[0071] S1, preparation of an iron-based porous carbon framework composite material: a chemical vapor deposition system is used for processing, the porous carbon framework is heated, carrier gas and heteroatom-containing gas are introduced to bring pyrolytic iron sources to deposit inside the porous carbon framework, the iron sources and the heteroatom-containing gas are pyrolyzed to form iron-based nanoparticles in the pores of the porous carbon framework, and an iron-based porous carbon framework composite material is obtained;

[0072] S2, preparation of the surface-coated iron-based porous carbon skeleton composite material: switch the gas path of the vapor deposition system, heat the porous carbon skeleton, and introduce the carrier gas to bring the pyrolytic carbon source to deposit on the surface of the iron-based porous carbon skeleton composite material, to obtain the surface-coated iron-based porous carbon skeleton composite material;

[0073] S3, high-temperature sintering: the surface-coated iron-based porous carbon skeleton composite material obtained in step S2 is subjected to high-temperature sintering to obtain the final negative electrode material.

[0074] In this embodiment, in step S1, the carrier gas is nitrogen and / or argon, the carrier gas flow rate is 20-300 Sccm, the deposition temperature is 300-800℃, and the deposition time is 0.2-3 h; the heteroatom-containing gas is one or two or more of H2S, PH3, and H2Se; and the pyrolytic iron source is one or two or more of ferrocene, iron phthalocyanine, ferrous gluconate, ferrous fumarate, and iron citrate.

[0075] In this embodiment, in step S2, the carrier gas is nitrogen and argon, the carrier gas flow rate is 20 Sccm, the deposition temperature is 1000℃, and the deposition time is 0.5 h; and the pyrolytic carbon source is benzene, toluene, trimethylbenzene, acetylene, ethanol, or formaldehyde.

[0076] In this embodiment, in step S3, the high-temperature sintering conditions are: a temperature increase rate of 0.5℃ / min, a sintering temperature of 1600℃, and a sintering time of 3 h. Embodiment

[0077] This embodiment discloses an iron-based porous carbon sodium-ion battery composite negative electrode material, which comprises a porous carbon skeleton, iron-based nanoparticles are compounded inside the porous carbon skeleton, and a hard carbon layer is coated outside the porous carbon skeleton, and the iron-based nanoparticles are Fe2O3, Fe3O4, FeS2, FeS, FeSe2, or FeP.

[0078] In this embodiment, the iron-based nanoparticles are filled in the porous carbon skeleton, the particle size of the iron-based nanoparticles is 0.8-45 nm, the iron-based nanoparticles of the nanoparticles are filled in the micropores or mesopores inside the porous carbon skeleton, the iron-based nanoparticles account for 60-90% of the total pore volume of the porous carbon skeleton, and the remaining unfilled pores are reserved buffer spaces. In the porous carbon skeleton, the average pore size of the mesopores or micropores is 0.8-50 nm, the porosity is 30-60%, and the specific surface area is 1000-3000 m 2 g -1 .

[0079] In the embodiment, the iron-based nanoparticles are filled in the porous carbon framework, the particle size of the iron-based nanoparticles is 0.8-45 nm, and the iron-based nanoparticles are filled in the micropores or mesopores in the porous carbon framework. The iron-based nanoparticles account for 60-90% of the total pore volume of the porous carbon framework, and the remaining unfilled pores are reserved buffer spaces. In the porous carbon framework, the average pore size of the mesopores or micropores is 0.8-50 nm, the porosity is 30-60%, and the specific surface area is 1000-3000 m 2 g -1 .

[0080] The preparation method of the iron-based porous carbon sodium ion battery composite negative electrode material in the embodiment includes the following steps:

[0081] S1, preparation of the iron-based porous carbon framework composite material: using a chemical vapor deposition system to process, heating the porous carbon framework, introducing carrier gas and heteroatom-containing gas to bring pyrolytic iron source to deposit in the porous carbon framework, and pyrolyzing the iron source and the heteroatom-containing gas in the pores of the porous carbon framework to form iron-based nanoparticles, thereby obtaining the iron-based porous carbon framework composite material;

[0082] S2, preparation of the surface-coated iron-based porous carbon framework composite material: switching the gas path of the vapor deposition system, heating the porous carbon framework, introducing carrier gas to bring pyrolytic carbon source to deposit on the surface of the iron-based porous carbon framework composite material, thereby obtaining the surface-coated iron-based porous carbon framework composite material;

[0083] S3, high-temperature sintering: high-temperature sintering the surface-coated iron-based porous carbon framework composite material obtained in step S2 to obtain the final negative electrode material.

[0084] In the embodiment, in step S1, the carrier gas is nitrogen and argon, the carrier gas flow rate is 20-300 Sccm, the deposition temperature is 500℃, and the deposition time is 2 h; the heteroatom-containing gas is H2S, PH3, and H2Se; and the pyrolytic iron source is ferrocene, iron phthalocyanine, ferrous gluconate, and ferrous fumarate.

[0085] In the embodiment, in step S2, the carrier gas is nitrogen and argon, the carrier gas flow rate is 100 Sccm, the deposition temperature is 600℃, and the deposition time is 0.6 h; and the pyrolytic carbon source is benzene, trimethylbenzene, acetylene, ethanol, formaldehyde, thiophene, and pyridine.

[0086] In the embodiment, in step S3, the high-temperature sintering conditions are as follows: the heating rate is 5℃ / min, the sintering temperature is 1000℃, and the sintering time is 4 h.

[0087] The above embodiments are only specific embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, and these obvious replacement forms belong to the protection scope of the present application.

Claims

1. An iron-based porous carbon-sodium ion battery composite anode material, comprising a porous carbon framework, characterized in that: The porous carbon framework is internally composited with iron-based nanoparticles, and the porous carbon framework is externally coated with a hard carbon layer. The iron-based nanoparticles are one or more of Fe2O3, Fe3O4, FeS2, FeS, FeSe2, and FeP. The iron-based nanoparticles are incorporated into the porous carbon framework by filling, and the particle size of the iron-based nanoparticles is 0.8-45 nm. The iron-based nanoparticles fill the micropores or mesopores inside the porous carbon framework. Iron-based nanoparticles account for 60-90% of the total pore volume of the porous carbon framework, with the remaining unfilled pores serving as reserved buffer space. In porous carbon frameworks, the average pore size of mesopores or micropores is 0.8-50 nm, the porosity is 30-60%, and the specific surface area is 1000-3000 m². 2 g -1 .

2. The preparation method of the iron-based porous sodium-carbon ion battery composite negative electrode material according to claim 1, characterized in that... Includes the following steps: S1. Preparation of iron-based@porous carbon skeleton composite material: A chemical vapor deposition system is used for processing. The porous carbon skeleton is heated, and a carrier gas and a gas containing heteroatoms are introduced to carry the pyrolytic iron source, causing it to deposit inside the porous carbon skeleton. The deposition temperature is 300–800℃, and the deposition time is 0.2–3 h. The iron source and the gas containing heteroatoms pyrolyze within the pores of the porous carbon skeleton to form iron-based nanoparticles, thus obtaining the iron-based@porous carbon skeleton composite material. The pyrolytic iron source is one or more of ferrocene, ferrophthalocyanine, ferrous gluconate, ferrous fumarate, and ferric citrate. S2. Preparation of surface-coated iron-based@porous carbon skeleton composite material: Switch the gas path of the vapor deposition system, heat the porous carbon skeleton, and introduce a carrier gas to carry in the pyrolytic carbon source so that it is deposited on the surface of the iron-based@porous carbon skeleton composite material. The deposition temperature is 400-1000℃ and the deposition time is 0.2-1 h to obtain the surface-coated iron-based@porous carbon skeleton composite material. The pyrolytic carbon source is one or more of benzene, toluene, trimethylbenzene, acetylene, ethanol, formaldehyde, thiophene, pyridine and / or sulfide. S3. High-temperature sintering: The iron-based @ porous carbon skeleton composite material with surface coating obtained in step S2 is subjected to high-temperature sintering at a temperature of 500-1600℃ for 1-5 hours to obtain the final anode material.

3. The method for preparing the iron-based porous sodium-carbon ion battery composite negative electrode material according to claim 2, characterized in that: In step S1, the carrier gas is nitrogen and / or argon, the carrier gas flow rate is 20-300 Sccm, and the heteroatom-containing gas is one or more of H2S, PH3, and H2Se.

4. The method for preparing the iron-based porous sodium-carbon ion battery composite negative electrode material according to claim 2, characterized in that: In step S2, the carrier gas is nitrogen and / or argon, and the carrier gas flow rate is 20-300 Sccm.

5. The method for preparing the iron-based porous sodium-carbon ion battery composite negative electrode material according to claim 2, characterized in that: In step S3, the heating rate is 0.5-10℃ / min.