Carbon-coated core-shell structure fe2n nanoparticle composite material, and preparation method and application thereof

Abstract

The application discloses a carbon-coated core-shell structure Fe2N nanoparticle composite material and a preparation method and application thereof, and belongs to the technical field of materials. The application comprises the following steps: mixing iron source and silicon source under alkaline catalytic conditions to obtain a material to which SiO2 is attached to the surface of the iron source; mixing the material to which SiO2 is attached and an organic carbon source to obtain an intermediate, and pre-oxidizing the intermediate to obtain Fe3O4 / SiO2 / C core-shell structure nanomaterial; etching the SiO2 intermediate layer of the Fe3O4 / SiO2 / C core-shell structure material to obtain Fe3O4 / C core-shell structure nanomaterial; and subjecting the Fe3O4 / C core-shell structure material to nitriding to obtain Fe2N / C core-shell structure nanomaterial. The Fe2N nanoparticles are wrapped in a carbon layer and constructed into a core-shell structure, so that the conductivity of the Fe2N is improved, the growth of sodium dendrites is effectively inhibited in the process of metal sodium deposition, and the electrochemical performance of the Fe2N / C core-shell structure nanomaterial as a negative electrode material of a sodium battery is greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of materials, and particularly relates to a carbon-coated core-shell structure Fe2N nanoparticle composite material and a preparation method and application thereof. BACKGROUND

[0002] Compared with traditional grid storage technologies, rechargeable batteries show significant advantages in conversion efficiency, energy density and power management. In addition, batteries are easier to deploy for various distributed and centralized applications. Lithium ion batteries (LIB) are the most widely used battery technology in today's grid energy storage, but the shortage of lithium resources leads to rising lithium prices, high cost, so scientists urgently need to develop new long-life energy storage devices with low cost and high performance. Compared with lithium, the same main group metal sodium has similar physicochemical properties, and is abundant in resources and low in price, so sodium-based batteries have entered people's field of vision. However, the sodium ion radius is larger than that of lithium, and the theoretical capacity is lower than that of lithium, and when the actual energy density is higher than 200 Wh kg -1 , the cost-effectiveness of sodium batteries is expected to exceed that of lithium ion batteries. In order to achieve this goal, it is crucial to develop a stable and high-capacity sodium anode, but during the discharge process of sodium metal batteries, due to the uneven deposition of Na, serious sodium dendrite growth is caused, which greatly limits the performance of sodium metal batteries.

[0003] The most important problem of the current sodium metal battery is to develop an electrode material with high sodium affinity, multiple active sites, which can effectively inhibit the growth of sodium dendrites. SUMMARY

[0004] In view of this, the application provides a carbon-coated core-shell structure Fe2N nanoparticle composite material and a preparation method and application thereof, and the main purpose is to solve the technical problem of sodium dendrite growth generated in the sodium metal battery.

[0005] In one aspect, the application provides a carbon-coated core-shell structure Fe2N nanoparticle composite material, which has a core-shell structure, Fe2N nanoparticles as a core, and a carbon material as a shell, and the carbon layer coats the Fe2N nanoparticles and has a cavity between them.

[0006] Optionally, the morphology of the core-shell structure nanocomposite material is a strip-shaped or rod-shaped sharp hexagonal prism.

[0007] In the present application, iron resources are used in sodium metal batteries. In the cycle process, sodium ions enter the core-shell structure through the surface carbon layer of the nanocomposite material, and form sodium nitride (Na XN), since sodium nitride has good sodium affinity, it can make the subsequent entering sodium ions preferentially nucleate; at the same time, the carbon layer coated on the surface can also effectively prevent the further growth of dendrites, avoid generating more sodium dendrites, prevent dendrites from penetrating the diaphragm, leading to battery short circuit, and the unique core-shell structure effectively inhibits the growth of sodium dendrites, so that the cycle stability of the battery is greatly improved.

[0008] In a second aspect, the application provides a preparation method of the carbon-coated core-shell structure Fe2N nanoparticle composite material, which comprises the following steps:

[0009] S1: obtaining an iron source;

[0010] S2: mixing the iron source and a silicon source in step S1 under alkaline conditions to obtain a material with SiO2 attached to the surface of the iron source;

[0011] S3: mixing the material with SiO2 attached to the surface of the iron source in step S2 and an organic carbon source to obtain an intermediate, and pre-oxidizing the intermediate by heating to obtain a Fe3O4 / SiO2 / C core-shell structure nanocomposite material;

[0012] S4: etching the SiO2 intermediate layer of the Fe3O4 / SiO2 / C core-shell structure nanocomposite material in step S3 to obtain a Fe3O4 / C core-shell structure nanocomposite material;

[0013] S5: nitrogenizing the Fe3O4 / C core-shell structure nanocomposite material in step S3 to obtain a Fe2N / C core-shell structure nanocomposite material.

[0014] Traditional FexN usually adopts a co-precipitation synthesized precursor, which is obtained after nitrogenizing atmosphere treatment, and has the disadvantages of harsh nitrogenizing conditions, low purity of the obtained nitrided iron phase, small specific surface area, large and uneven particle size, etc. The above synthesis method of the application is simple, environmentally friendly, has high product yield, low production cost, and is easy to realize commercialization.

[0015] The iron source and the silicon source in step S1 of the application are mixed under alkaline catalytic conditions.

[0016] The pre-oxidation before etching is to build a stable carbon skeleton to prevent the structure from collapsing during later etching.

[0017] Optionally, in step S1, the iron source is selected from an iron-containing metal organic framework material or an iron oxide.

[0018] Optionally, in step S1, the preparation method of the iron-containing metal organic framework material comprises: mixing raw materials of an iron-containing compound and an organic compound, and heating III under closed conditions to obtain an iron-containing metal organic framework material.

[0019] Optionally, in step S1, the iron-containing compound is selected from iron nitrate nonahydrate; and the organic compound is selected from fumaric acid.

[0020] Optionally, in step S1, the heating III is performed at a temperature of 100-120°C for 5-7h.

[0021] Optionally, in step S1, the heating III is performed at a temperature of 110°C for 6h.

[0022] The iron-containing metal-organic framework material used in the present application can be prepared by the above method or selected from prior art.

[0023] Optionally, in step S2, the silicon source is selected from tetraethyl orthosilicate.

[0024] Optionally, in step S3, the organic carbon source is selected from dopamine hydrochloride.

[0025] The organic carbon source used in the present application can also be selected from other organic compounds.

[0026] Optionally, in step S2, the alkaline condition comprises ammonia.

[0027] Optionally, after mixing the iron source, the silicon source and ammonia, the mixture is stirred for 1-2h, and the obtained material with SiO2 attached to the surface of the iron source is obtained after centrifugation and drying.

[0028] Optionally, in step S2, the stirring is performed for 1.5h.

[0029] Optionally, in step S2, the mixing ratio of the iron source, the silicon source and the ammonia is (250-350)mg:(0.5-1.5)mL:(0.4-0.6)mL.

[0030] Optionally, in step S2, the mixing ratio of the iron-containing metal-organic framework material, the tetraethyl orthosilicate and the ammonia is (250-350)mg:(0.5-1.5)mL:(0.4-0.6)mL.

[0031] Optionally, in step S2, the mixing ratio of the iron-containing metal-organic framework material, the tetraethyl orthosilicate and the ammonia is 300mg:1mL:0.5mL.

[0032] Optionally, in step S3, the material with SiO2 attached to the surface of the iron source, dopamine hydrochloride and tris buffer with pH of 8.5 are mixed, the mixture is stirred for 7-9h, and the obtained product after centrifugation and drying is subjected to pre-oxidation in a tube furnace.

[0033] Optionally, in step S3, the stirring is performed for 8h.

[0034] Optionally, in step S3, the mixing ratio of the SiO2-attached material, dopamine hydrochloride and buffer is (180-220) mg:(60-140) mg:(80-120) mL.

[0035] Optionally, in step S3, the mixing weight ratio of the SiO2-attached material, dopamine hydrochloride and buffer is 200 mg:100 mg:100 mL.

[0036] Optionally, in step S3, the heating pre-oxidation process comprises heating I of the intermediate in an inert atmosphere to obtain the Fe3O4 / SiO2 / C core-shell structure nanocomposite.

[0037] Optionally, in step S3, the inert atmosphere is selected from an argon atmosphere.

[0038] Optionally, the heating I is performed at a temperature of 400-600°C for 1-3 h.

[0039] Optionally, the heating I is performed at a temperature of 500°C for 2 h.

[0040] Optionally, in step S4, the etching is performed by using a NaOH solution with a concentration of 3-5 mol / L to etch the SiO2 intermediate layer of the Fe3O4 / SiO2 / C core-shell structure nanocomposite.

[0041] Optionally, in step S4, the molar concentration of the NaOH solution is 4 mol / L.

[0042] Optionally, in step S4, the etching process comprises mixing the Fe3O4 / SiO2 / C core-shell structure nanocomposite and the NaOH solution, stirring at a temperature of 70-90°C for 8-12 h to etch the SiO2 intermediate layer, centrifugal washing and vacuum drying to obtain the Fe3O4 / C core-shell structure nanocomposite.

[0043] Optionally, in step S4, the etching is performed by stirring at a temperature of 80°C for 10 h.

[0044] Optionally, in step S5, the nitriding process comprises heating II of the Fe3O4 / C core-shell structure nanocomposite in a nitrogen source atmosphere to obtain the Fe2N / C core-shell structure nanocomposite.

[0045] Optionally, in step S5, the heating II is performed at a temperature of 500-650°C for 1.5-2.5 h.

[0046] Optionally, in step S5, the temperature of the heating II is 600℃, and the time of the heating II is 2h.

[0047] Optionally, the nitrogen source is selected from an ammonia gas atmosphere.

[0048] Optionally, in step S5, the heating II comprises two heating processes.

[0049] The first heating process comprises: heating at a rate of 5℃ / min to 150-250℃ and then holding for 1.5-2.5h.

[0050] The second heating process comprises: heating at a rate of 2℃ / min to 550-650℃ and then holding for 1.5-2.5h.

[0051] Optionally, the first heating process comprises: heating at a rate of 5℃ / min to 200℃ and then holding for 2h.

[0052] The second heating process comprises: heating at a rate of 2℃ / min to 600℃ and then holding for 2h.

[0053] The application specifically provides a preparation method of a carbon-coated core-shell structure Fe2N nanoparticle sodium metal battery negative electrode material, comprising the following steps:

[0054] First, a MIL 88A precursor is prepared; second, the prepared MIL 88A precursor is coated with a layer of SiO2, centrifuged and dried, and then coated with dopamine, dried and placed in a tube furnace to be pre-oxidized at a constant rate to a certain temperature for a period of time. The pre-oxidized product is etched with high-concentration sodium hydroxide to obtain an intermediate product of a core-shell structure, and finally the intermediate product of the core-shell structure is placed in a tube furnace to be nitrided at a constant heating rate and temperature under an ammonia atmosphere, and finally a carbon-coated core-shell structure Fe2N nanoparticle composite material is obtained.

[0055] The application wraps Fe2N nanoparticles in a carbon layer and constructs a core-shell structure, thereby not only improving the conductivity of Fe2N, but also effectively inhibiting the growth of sodium dendrites during sodium metal deposition, greatly improving the electrochemical performance of the Fe2N nanoparticles as a sodium metal battery negative electrode material.

[0056] The application specifically provides a preparation method of a carbon-coated core-shell structure Fe2N nanoparticle sodium metal battery negative electrode material, comprising the following steps:

[0057] (1) a certain amount of ferric nitrate and fumaric acid is added in a deionized water solution, stirred for 10 minutes, then transferred to a polytetrafluoroethylene reaction kettle, placed in a 110℃ oven for 6 hours, cooled to room temperature and centrifuged and dried to obtain a MIL 88A precursor;

[0058] (2) MIL 88A precursor is dispersed in a mixed solution of ethanol and water, a certain amount of ammonia water and tetraethyl orthosilicate is added dropwise, stirring for 1.5 hours, a layer of SiO2 is successfully attached to the surface of MIL 88A, and then centrifugal drying is performed;

[0059] (3) The dried MIL 88A / SiO2 is dispersed in tris buffer solution again, dopamine hydrochloride is added, stirring for 8 hours, centrifugal drying, and then the obtained product is placed in a tube furnace for pre-oxidation, 500℃ for 2 hours, and argon protection gas is passed throughout the process, and Fe3O4 / SiO2 / C core-shell structure nanocomposite is obtained after cooling;

[0060] (4) The Fe3O4 / SiO2 / C core-shell structure nanocomposite is dispersed in a 4 mol NaOH solution, stirred at 80℃ for 10 hours to etch the SiO2 intermediate layer, centrifuged and washed, and then vacuum dried to obtain a Fe3O4 / C core-shell structure nanocomposite;

[0061] (5) The Fe3O4 / C nanomaterial is placed in a tube furnace for nitridation, 600℃ for 2 hours, and ammonia gas is passed throughout the process, and Fe2N / C core-shell structure nanocomposite is obtained after cooling;

[0062] (6) The prepared composite material is assembled into a sodium metal battery, and the sodium metal battery performance is tested.

[0063] In a third aspect, the application provides a sodium ion battery negative electrode material, wherein the active material of the negative electrode material comprises the core-shell structure nanocomposite or the core-shell structure nanocomposite prepared by the above preparation method.

[0064] In a fourth aspect, the application provides a sodium metal battery, wherein the negative electrode material of the sodium metal battery comprises the sodium ion battery negative electrode material.

[0065] Optionally, the sodium metal battery is a sodium metal button cell.

[0066] Compared with the prior art, the application has the following beneficial effects:

[0067] The application uses MIL 88A precursor as an iron source, wherein MIL 88A can be prepared in large quantities, and each batch can obtain a gram level, and then SiO2 and dopamine are coated in turn, the SiO2 intermediate layer is etched after pre-oxidation, and the core-shell structure Fe2N / C nanocomposite is obtained by nitriding in an ammonia atmosphere. The structure of this composite nanomaterial can greatly improve the conductivity of the material, and the core-shell structure can well inhibit the growth of sodium dendrites to obtain excellent electrochemical performance. In addition, this method has simple production process, is environment-friendly, has high product yield, low production cost, and is easy to realize commercialization. BRIEF DESCRIPTION OF DRAWINGS

[0068] Figure 1 is the X-ray diffraction pattern of the product obtained by the preparation process of the present application;

[0069] Figure 2 is the field emission scanning electron microscope pattern of the product obtained by the preparation process of the present application;

[0070] Figure 3 is the electrochemical performance pattern of the electrode material prepared by the preparation process of the present application;

[0071] Figure 4 is the symmetric cell electrochemical cycle performance pattern of the electrode material prepared by the preparation process of the present application. DETAILED DESCRIPTION

[0072] The present application will be further described below in combination with specific examples. The following description is only a few embodiments of the present application, and does not limit the present application in any form. Although the present application is disclosed as follows with preferred embodiments, it is not intended to limit the present application. Any skilled person in the art, without departing from the scope of the technical solution of the present application, can make some changes or modifications to the disclosed technical content, which are equivalent to equivalent embodiments, and are within the scope of the technical solution.

[0073] Unless otherwise specified, the raw materials in the examples of the present application are purchased through commercial channels and directly used without any special treatment.

[0074] Example 1

[0075] Preparation of the precursor:

[0076] 2.69 g of ferric nitrate nonahydrate was added to 25 mL of deionized water, and ultrasonic treatment was performed for 10 minutes, and was recorded as solution A; 0.7 g of fumaric acid was added to 100 mL of deionized water, and stirring was performed at 70°C for 15 minutes, and was recorded as solution B; solution A was slowly added to solution B, and stirring was performed for 20 minutes, and then was transferred to a polytetrafluoroethylene reaction kettle, and was placed in a 110°C oven for 6 hours of heat preservation, and after cooling to room temperature, centrifugal drying was performed to obtain the MIL 88A precursor.

[0077] Preparation of the intermediate product:

[0078] The 300 mg MIL 88A precursor is dispersed in a mixed solution of 80 mL of ethanol and 20 mL of water, stirred for 30 minutes, then 0.5 mL of ammonia water and 1 mL of tetraethyl orthosilicate are added dropwise, stirred for 1.5 hours, a layer of SiO2 is successfully attached to the surface of MIL 88A, then centrifugal drying is performed; 200 mg of dried MIL 88A / SiO2 is again dispersed in 100 mL of tris buffer solution with a pH of 8.5, 100 mg of dopamine hydrochloride is added, stirred for 8 hours, centrifugal dried, and then the obtained product is placed in a tube furnace for pre-oxidation, 500℃ for 2 hours, with argon gas protection throughout the process, and after cooling, a Fe3O4 / SiO2 / C core-shell structure nanocomposite material is obtained; the Fe3O4 / SiO2 / C core-shell structure nanocomposite material is dispersed in a 4 mol NaOH solution, stirred at 80℃ for 10 hours to etch the SiO2 intermediate layer, centrifugal washed, and then vacuum dried to obtain a Fe3O4 / C core-shell structure nanocomposite material.

[0079] nitriding process

[0080] The Fe3O4 / C nanomaterial is placed in a tube furnace for nitriding, 600℃ for 2 hours, first heated to 200℃ at a rate of 5℃ / min, then held for 2 hours, then heated to 600℃ at a rate of 2℃ / min, and held for 2 hours, with ammonia gas being introduced throughout the process, and after cooling, a powder-like nanocomposite material is obtained.

[0081] The powder-like nanocomposite material prepared in the above Example 1 is subjected to structural detection analysis:

[0082] From Figure 1 The X-ray diffraction pattern shows that the above-mentioned powder-like nanocomposite material has a Fe2N / C core-shell structure; the morphology of the material is shown in the field emission scanning electron microscope pattern, which is a strip or rod-shaped sharp hexagonal prism, with Fe2N as the core, a carbon-coated structure on the outside, and a cavity structure in the middle. Figure 2

[0083] Example 2

[0084] The above-mentioned active composite material powder is artificially prepared into a button-type sodium metal battery;

[0085] The specific steps are as follows: the above-mentioned active material powder and binder (sodium carboxymethyl cellulose, CMC) are ground uniformly at a mass ratio of 9:1, then a small amount of deionized water is added to form a slurry, the slurry is coated on a copper foil with a diameter of 12 mm, then it is placed in a vacuum drying oven for 24 h at 70℃; finally, the electrode sheet is assembled into a sodium metal button battery with metal sodium as the counter electrode in a glove box.

[0086] The sodium metal button battery assembled in Example 2 is subjected to electrochemical performance testing.

[0087] From​Figure 3 It can be seen that the nucleation overpotential of sodium metal on the Fe2N / C material is only 18 mV; it is shown that the surface of the composite material is conducive to inhibiting the generation of dendrites.

[0088] By Figure 4 It can be seen that the symmetric battery prepared by using Fe2N / C as the electrode material has a current density of 1 mA cm-2 and a specific capacity of 1 mAh cm-2, and the overpotential is still very small, not more than 0.05 V, which shows that the core-shell structure Fe2N / C nanocomposite reduces the nucleation overpotential of sodium metal, and the unique core-shell structure effectively inhibits the growth of sodium dendrites, and the cycle stability of the symmetric battery is greatly improved. -2 Current density, 1 mAh cm-2 -2 Under the condition of 2000 hours of cycle, the overpotential is still very small, not more than 0.05 V, which shows that the core-shell structure Fe2N / C nanocomposite reduces the nucleation overpotential of sodium metal, and the unique core-shell structure effectively inhibits the growth of sodium dendrites, and the cycle stability of the symmetric battery is greatly improved.

[0089] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the preferred embodiments are disclosed above, they are not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical contents without departing from the scope of the technical solutions of the present application, which are equivalent to equivalent embodiments, and belong to the scope of the technical solutions.

Claims

1. A carbon-coated core-shell structured Fe2N nanoparticle composite material, characterized in that, The composite material has a core-shell structure, with Fe2N nanoparticles as the core and carbon material as the shell. The carbon layer covers the Fe2N nanoparticles and there is a cavity between them. The core-shell structured nanocomposite material has a morphology of strip-shaped or rod-shaped pointed hexagonal prisms.

2. The method for preparing a carbon-coated core-shell structured Fe2N nanoparticle composite material according to claim 1, characterized in that, The method includes the following steps: S1: Obtain iron source; S2: The iron source and silicon source mentioned in step S1 are mixed under alkaline conditions to obtain a material with SiO2 attached to the surface of the iron source; S3: The material with SiO2 attached to the surface of the iron source in step S2 is mixed with an organic carbon source to obtain an intermediate. The intermediate is pre-oxidized by heating to obtain a Fe3O4 / SiO2 / C core-shell structured nanocomposite material. S4: The Fe3O4 / SiO2 / C core-shell structured nanocomposite material in step S3 is obtained by etching the SiO2 intermediate layer to obtain the Fe3O4 / C core-shell structured nanocomposite material; S5: The Fe3O4 / C core-shell nanocomposite material in step S3 is nitrided to obtain the Fe2N / C core-shell nanocomposite material.

3. The preparation method according to claim 2, characterized in that, In step S1, the iron source is selected from iron-containing metal-organic framework materials or iron oxide; The silicon source is selected from tetraethyl orthosilicate; The organic carbon source is selected from dopamine hydrochloride.

4. The preparation method according to claim 2, characterized in that, In step S2, the alkaline conditions include ammonia water; After mixing the iron source, the silicon source, and ammonia, the mixture is stirred for 1 to 2 hours, and then centrifuged and dried to obtain a material with SiO2 attached to the surface of the iron source. The mixing ratio of the iron source, the silicon source and the ammonia water is (250 ~ 350) mg: (0.5 ~ 1.5) mL: (0.4 ~ 0.6) mL.

5. The preparation method according to claim 2, characterized in that, In step S3, the material with SiO2 attached to the surface of the iron source, dopamine hydrochloride, and Tris buffer solution with pH 8.5 are mixed and stirred for 7 to 9 hours. After centrifugation and drying, the resulting product is pre-oxidized by heating in a tube furnace. The mixing ratio of the material with SiO2 attached to the iron source surface, the dopamine hydrochloride and the buffer solution is (180~220) mg: (60~140) mg: (80~120) mL.

6. The preparation method according to claim 2, characterized in that, In step S3, the heating pre-oxidation process includes: heating the intermediate in an inert atmosphere to obtain Fe3O4 / SiO2 / C core-shell structured nanocomposite material; The inert atmosphere is selected from argon atmosphere; The temperature of heating I is 400 ~ 600 ℃, and the heating time is 1 ~ 3 h.

7. The preparation method according to claim 2, characterized in that, In step S4, the etching is performed by etching the SiO2 intermediate layer of the Fe3O4 / SiO2 / C core-shell structured nanocomposite material with a NaOH solution of concentration of 3~5 mol / L. The etching process includes: mixing the Fe3O4 / SiO2 / C core-shell nanocomposite material with NaOH solution, stirring at 70~90 ℃ for 8~12 h to etch the SiO2 intermediate layer, centrifuging and washing, and then vacuum drying to obtain the Fe3O4 / C core-shell nanocomposite material.

8. The preparation method according to claim 2, characterized in that, In step S5, the nitriding process includes: heating the Fe3O4 / C core-shell structured nanocomposite material in a nitrogen source atmosphere to obtain the Fe2N / C core-shell structured nanocomposite material. The temperature of heating II is 500~650 ℃, and the heating time is 1.5~2.5 h; the nitrogen source atmosphere is selected from an ammonia atmosphere; The heating II process includes two heating processes; The first heating process includes: raising the temperature to 150~250℃ at a rate of 5℃ / min and then holding it at that temperature for 1.5~2.5h; The second heating process includes: heating to 550~650℃ at a rate of 2℃ / min and then holding at that temperature for 1.5~2.5h.

9. A sodium-ion battery anode material, characterized in that, The active material of the negative electrode material includes the core-shell structured nanocomposite material according to claim 1 or the core-shell structured nanocomposite material obtained by the preparation method according to any one of claims 3 to 8.

10. A sodium metal battery, characterized in that, The negative electrode material of the sodium metal battery includes the negative electrode material of the sodium-ion battery as described in claim 9; The sodium metal battery is a sodium metal button cell.

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