阅读说明：本技术 一种四氧化三铁/氧化硅/多层石墨烯复合材料及制备方法 (Ferroferric oxide/silicon oxide/multilayer graphene composite material and preparation method thereof ) 是由 徐军明 徐嘉呈 冯斌 唐梦霞 刘树岭 于 2020-06-02 设计创作，主要内容包括：本发明公开了一种四氧化三铁/氧化硅/多层石墨烯复合材料及制备方法,该复合材料中多层石墨烯为碳基底材料,由膨胀石墨经机械剥离获得,厚度小于10nm,具有平整的表面。四氧化三铁和氧化硅在多层石墨烯表面形成复合薄膜,四氧化三铁和氧化硅在复合膜中相互隔离,均匀分布,膜层的厚度小于10nm。该四氧化三铁/氧化硅/多层石墨烯复合材料的具体制备过程为：将膨胀石墨放入DMF与水的混合溶液,经机械剥离后获得多层石墨烯分散液；称取无水乙酸钠、氯化亚铁和正硅酸乙酯,加入多层石墨烯分散液；放入水浴中搅拌,随后水浴中室温升温至90℃,升温时间为15分钟；反应一定时间后取出,离心清洗后获得本发明四氧化三铁/氧化硅/多层石墨烯复合材料。本发明制备工艺简单,适合工业化生产。(The invention discloses a ferroferric oxide/silicon oxide/multilayer graphene composite material and a preparation method thereof, wherein multilayer graphene in the composite material is a carbon-based material, is obtained by mechanically stripping expanded graphite, has the thickness of less than 10nm, and has a flat surface. Ferroferric oxide and silicon oxide form a composite film on the surface of multilayer graphene, the ferroferric oxide and the silicon oxide are mutually isolated and uniformly distributed in the composite film, and the thickness of the film layer is less than 10 nm. The preparation process of the ferroferric oxide/silicon oxide/multilayer graphene composite material comprises the following steps: placing the expanded graphite into a mixed solution of DMF and water, and mechanically stripping to obtain a multilayer graphene dispersion liquid; weighing anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate, and adding the multilayer graphene dispersion liquid; stirring in a water bath, and then heating to 90 ℃ at room temperature in the water bath for 15 minutes; taking out after reacting for a certain time, and obtaining the ferroferric oxide/silicon oxide/multilayer graphene composite material after centrifugal cleaning. The preparation process is simple and suitable for industrial production.)

1. The ferroferric oxide/silicon oxide/multilayer graphene composite material is characterized in that multilayer graphene is used as a carbon-based material in the composite material, ferroferric oxide and silicon oxide form a composite film on the surface of the multilayer graphene, and the ferroferric oxide and the silicon oxide are mutually isolated and uniformly distributed in the composite film; the multilayer graphene is obtained by mechanically exfoliating expanded graphite.

2. The ferroferric oxide/silicon oxide/multilayer graphene composite material according to claim 1, wherein the thickness of the composite film is less than 10 nm.

3. The ferroferric oxide/silicon oxide/multilayer graphene composite material according to claim 1, wherein the multilayer graphene has a flat surface and a thickness of less than 10 nm.

4. The preparation method of the ferroferric oxide/silicon oxide/multilayer graphene composite material according to claim 1, characterized by comprising the following steps:

step S1, measuring DMF (dimethyl formamide) and deionized water with a volume ratio of 8:2, adding expanded graphite, and performing high-speed shearing for 30 minutes to obtain a multilayer graphene dispersion liquid, wherein the concentration of the expanded graphite relative to a mixed solvent is 0.5-2 mg/mL;

step S2, weighing anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate, adding the anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate into the multilayer graphene dispersion liquid, and fully stirring at normal temperature to obtain a mixed liquid; the concentration of the anhydrous sodium acetate relative to the mixed solvent is 10-30 mg/mL, the concentration of the ferrous chloride relative to the mixed solvent is 10-20 mg/mL, and the concentration of the ethyl orthosilicate relative to the mixed solvent is 2-10 mu L/mL;

step S3, placing the mixed solution into a water bath and stirring;

step S4, taking out after the water bath reaction for 2-4 hours, and carrying out centrifugal cleaning on the reaction product;

and step S5, drying the cleaned reaction product to obtain the ferroferric oxide/silicon oxide/multilayer graphene composite material.

5. The preparation method of the ferroferric oxide/silicon oxide/multilayer graphene composite material according to claim 4, wherein the nano-iron oxide and the silicon oxide particles are uniformly distributed on the surface of the multilayer graphene, and basically no agglomeration phenomenon exists; the mass ratio of the ferroferric oxide to the silicon oxide is adjusted by adjusting the content of the tetraethoxysilane.

6. The preparation method of the ferroferric oxide/silicon oxide/multilayer graphene composite material according to claim 4, wherein DMF is taken as a complexing agent to be combined with ferrous ions to form a complex, the complex is adsorbed on the surface of the multilayer graphene through molecular force, and the complex is gradually decomposed and converted on the surface of the multilayer graphene to form nanoscale ferroferric oxide particles; meanwhile, tetraethoxysilane is adsorbed on the surface of the multilayer graphene through molecular force, and tetraethoxysilane generates silicon dioxide nanoparticles through polycondensation; so that ferroferric oxide and silicon dioxide are uniformly deposited on the surface of the multilayer graphene to form a film; another product C of condensation polymerization of ethyl orthosilicate₂H₅OH has reducing property and slows down Fe²⁺Oxygen of (2)The reaction rate is increased, so that the final product is Fe₃O₄。

Technical Field

The invention belongs to the technical field of materials, and relates to a ferroferric oxide/silicon oxide/multilayer graphene composite material and a preparation method thereof. The material has potential application in the fields of catalysis, energy storage and the like, and can be used as a high-performance lithium ion battery cathode material.

Background

With the continuous development of portable electronic products, people have higher and higher requirements on indexes such as energy density, power density, service life and rapid charge and discharge of energy storage equipment. At present, the cathode material in the commercial lithium ion battery is mainly graphite material (with a theoretical capacity of 372 mAh/g), and the transition metal oxide has attracted extensive attention because of the advantages of high reversible capacity, low working voltage, abundant reserves, no pollution to the environment and the like.

The theoretical capacity of the ferroferric oxide is as high as 926mAh/g, but when the ferroferric oxide is charged and discharged, huge volume expansion occurs, and after multiple cycles, the active material is easy to pulverize/fall off, so that the cycle performance is reduced and the capacity is rapidly attenuated. In view of the above drawbacks, researchers propose: the performance of the composite material is improved by structural nanocrystallization, combination with other conductive materials, composition of the composite material with other oxides and the like.

The preparation method of the metal oxide/silicon oxide composite material mainly comprises a high-temperature solid-phase synthesis method and a nano-silica coating method. The high-temperature solid phase method generally needs to raise the temperature to more than 950 ℃ to compound the metal oxide and the silicon dioxide, so that the consumed energy is large and the requirement on equipment is high. The nano silicon dioxide coating method is to prepare spherical silicon dioxide particles firstly and then coat metal oxide, and the process is complex and is not suitable for industrial production.

Aiming at the defects in the prior art, the invention provides a technical scheme to solve the technical problems in the prior art.

Disclosure of Invention

Aiming at the problems in the background art, the invention provides a ferroferric oxide/silicon oxide/multilayer graphene composite material and a preparation method thereof.

In order to solve the technical problems in the prior art, the technical scheme of the invention is as follows:

a ferroferric oxide/silicon oxide/multilayer graphene composite material takes multilayer graphene as a carbon-based material, ferroferric oxide and silicon oxide form a composite film on the surface of the multilayer graphene, and the ferroferric oxide and the silicon oxide are mutually isolated and uniformly distributed in the composite film; the multilayer graphene is obtained by mechanically exfoliating expanded graphite.

As a further improvement, the thickness of the composite film is less than 10 nm.

As a further improvement, the multilayer graphene has a flat surface with a thickness of less than 10 nm.

The invention also discloses a preparation method of the ferroferric oxide/silicon oxide/multilayer graphene composite material, which comprises the following steps:

step S1, measuring DMF (dimethyl formamide) and deionized water with a volume ratio of 8:2, adding expanded graphite, and shearing for 30 minutes by a dispersion machine at 30000 r/min to obtain a multilayer graphene dispersion liquid, wherein the concentration of the expanded graphite relative to the mixed solvent is 0.5-2 mg/mL;

step S2, weighing anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate, adding the anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate into the multilayer graphene dispersion liquid, and magnetically stirring the mixture for 10 minutes at normal temperature. The concentration of the anhydrous sodium acetate relative to the mixed solvent is 10-30 mg/mL, the concentration of the ferrous chloride relative to the mixed solvent is 10-20 mg/mL, and the concentration of the ethyl orthosilicate relative to the mixed solvent is 2-10 mu L/mL;

step S3, putting the mixed solution into a water bath for stirring, then heating the water bath from room temperature to 90 ℃ for 15 minutes, and rotating the magnetic stirring at a speed of 300 r/min;

step S4, taking out after reacting for 2-4 hours, and centrifugally cleaning reaction products, wherein deionized water is adopted for centrifugal cleaning for 3 times, alcohol is adopted for centrifugal cleaning for 3 times, and the speed of a centrifugal machine is 6000 rpm;

and step S5, after cleaning, placing the material in an oven to dry for 24 hours at 70 ℃, and drying to obtain the ferroferric oxide/silicon oxide/multilayer graphene composite material.

As a further improvement scheme, the multilayer graphene is used as a substrate, and the nano ferric oxide and the silicon oxide particles can be uniformly distributed on the surface of the multilayer graphene and basically have no agglomeration phenomenon. The mass ratio of the ferroferric oxide to the silicon oxide can be adjusted by adjusting the content of the tetraethoxysilane.

As a further improvement, in step S4, DMF as a complexing agent is combined with divalent iron ions to form a complex, and the complex is adsorbed on the surface of the multilayer graphene through molecular force, and the complex is gradually decomposed and converted on the surface of the multilayer graphene to form nano-scale ferroferric oxide particles. Meanwhile, the tetraethoxysilane is adsorbed on the surface of the multilayer graphene through molecular force, and the tetraethoxysilane generates silicon dioxide nano-particles through a polycondensation reaction. So that ferroferric oxide and silicon dioxide are uniformly deposited on the surface of the multilayer graphene to form a film. Another product C of condensation polymerization of ethyl orthosilicate₂H₅OH has reducing property and slows down Fe²⁺So that the final product is Fe₃O₄Instead of Fe₂O₃。

Compared with the prior art, the invention has the following beneficial effects:

(1) the film formed on the surface of the multilayer graphene is uniform, and the particle diameter is small. The silicon oxide and the ferroferric oxide are mutually dispersed.

(2) The reaction solution is not required to be added with a reducing agent and protected by atmosphere, and is prepared from a condensation polymerization reaction product C of ethyl orthosilicate₂H₅The reduction of OH makes the final product ferroferric oxide.

(2) The preparation of the substrate multilayer graphene is simple, the cost is low, and the ferroferric oxide and silicon dioxide nanoparticle film can be deposited without activating the surface of the multilayer graphene.

(3) The ferrous chloride and the tetraethoxysilane have low cost and are convenient to purchase. Is beneficial to large-scale production.

(4) The method has the advantages of simple process, proper reaction temperature, short reaction time, less energy consumption and lower requirement on equipment, and is suitable for large-scale industrial production.

Drawings

Fig. 1 is a flowchart illustrating steps of a method for preparing uniformly distributed iron oxide and silicon oxide particles on multilayer graphene according to example 1 of the present invention;

fig. 2 is a low-power scanning electron microscope image of the method for preparing uniformly distributed iron oxide and silicon oxide particles on multilayer graphene according to example 1 of the present invention;

fig. 3 is a high-power scanning electron microscope image of the method for preparing uniformly distributed iron oxide and silicon oxide particle particles on multilayer graphene according to example 1 of the present invention;

FIG. 4 is a test junction of cyclic voltammograms of a half cell made with the product of an example of the invention;

fig. 5 is a test curve of constant current charging and discharging of a half cell made of the product of the embodiment of the invention.

Detailed Description

In order to better explain the process and scheme of the present invention, the following invention is further described with reference to the accompanying drawings and examples. The specific embodiments described herein are merely illustrative of the invention and do not delimit the invention.

In order to solve the technical problems in the prior art, referring to fig. 1, a flow chart of steps of a preparation method for uniformly distributing nano ferroferric oxide and silicon dioxide particles on multilayer graphene is shown. The preparation process is described in detail by combining the following 3 examples.

EXAMPLE 1

Step S1, measuring DMF (dimethyl formamide) and deionized water with a volume ratio of 8:2, adding expanded graphite, and shearing for 30 minutes by a dispersion machine at 30000 r/min to obtain a multilayer graphene dispersion liquid, wherein the concentration of the expanded graphite relative to the mixed solvent is 2 mg/mL;

step S2, weighing anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate, adding the anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate into the multilayer graphene dispersion liquid, and magnetically stirring the mixture for 10 minutes at normal temperature. The concentration of the anhydrous sodium acetate relative to the mixed solvent is 20mg/mL, the concentration of the ferrous chloride relative to the mixed solvent is 10mg/mL, and the concentration of the tetraethoxysilane relative to the mixed solvent is 2 mu L/mL;

step S3, putting the mixed solution into a water bath for stirring, then heating the water bath from room temperature to 90 ℃ for 15 minutes, and rotating the magnetic stirring at a speed of 300 r/min;

step S4, taking out after reacting for 2 hours, and centrifugally cleaning the reaction product by using deionized water for 3 times and alcohol for 3 times, wherein the speed of the centrifugal machine is 6000 r/min;

and step S5, after cleaning, placing the material in an oven to dry for 24 hours at 70 ℃, and drying to obtain the ferroferric oxide/silicon oxide/multilayer graphene composite material.

The composite material powder obtained by the preparation was subjected to SEM observation, and fig. 2 and 3 are SEM images at different magnifications. Only the morphology of the multilayer graphene is observed from the low power SEM figure 2. When the surface of the graphene in fig. 2 is enlarged, a scanning electron microscope image in fig. 3 is obtained, and it can be observed from fig. 3 that fine particles are connected into a film, completely coat the graphene, and are uniformly distributed without agglomeration. Several large particles in figure 3 are precipitated extra magnetite/silica particles, not referred to in the present invention as a magnetite/silica thin film. The results of cyclic voltammetry measurements on half cells prepared from the product of this example are shown in FIG. 4, where the peaks are redox peaks for lithium deintercalation of ferroferric oxide and silica. The test curve of constant current charge and discharge is shown in fig. 5, showing a first discharge capacity of 1250mAh/g, second and third discharge capacities of 940mAh/g and 920mAh/g, showing a higher discharge capacity.

Instantiation 2

Step S1, measuring DMF (dimethyl formamide) and deionized water with a volume ratio of 8:2, adding expanded graphite, and shearing for 30 minutes by a dispersion machine at 30000 r/min to obtain a multilayer graphene dispersion liquid, wherein the concentration of the expanded graphite relative to the mixed solvent is 1.5 mg/mL;

step S2, weighing anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate, adding the anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate into the multilayer graphene dispersion liquid, and magnetically stirring the mixture for 10 minutes at normal temperature. The concentration of the anhydrous sodium acetate relative to the mixed solvent is 20mg/mL, the concentration of the ferrous chloride relative to the mixed solvent is 10mg/mL, and the concentration of the tetraethoxysilane relative to the mixed solvent is 4 mu L/mL;

step S3, putting the mixed solution into a water bath for stirring, then heating the water bath from room temperature to 90 ℃ for 15 minutes, and rotating the magnetic stirring at a speed of 300 r/min;

step S4, taking out after reacting for 3 hours, and centrifugally cleaning the reaction product by using deionized water for 3 times and alcohol for 3 times, wherein the speed of the centrifugal machine is 6000 r/min;

and step S5, after cleaning, placing the material in an oven to dry for 24 hours at 70 ℃, and drying to obtain the ferroferric oxide/silicon oxide/multilayer graphene composite material.

Instantiation 3

Step S1, measuring DMF (dimethyl formamide) and deionized water with a volume ratio of 8:2, adding expanded graphite, and shearing for 30 minutes by a dispersion machine at 30000 r/min to obtain multilayer graphene dispersion liquid, wherein the concentration of the expanded graphite relative to the mixed solvent is 0.5 mg/mL;

step S2, weighing anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate, adding the anhydrous sodium acetate, ferrous chloride and ethyl orthosilicate into the multilayer graphene dispersion liquid, and magnetically stirring the mixture for 10 minutes at normal temperature. The concentration of the anhydrous sodium acetate relative to the mixed solvent is 20mg/mL, the concentration of the ferrous chloride relative to the mixed solvent is 10mg/mL, and the concentration of the tetraethoxysilane relative to the mixed solvent is 6 mu L/mL;

step S3, putting the mixed solution into a water bath for stirring, then heating the water bath from room temperature to 90 ℃ for 15 minutes, and rotating the magnetic stirring at a speed of 300 r/min;

step S4, taking out after 4 hours of reaction, and centrifugally cleaning the reaction product by using deionized water for 3 times and alcohol for 3 times, wherein the speed of the centrifugal machine is 6000 r/min;

and step S5, after cleaning, placing the material in an oven to dry for 24 hours at 70 ℃, and drying to obtain the ferroferric oxide/silicon oxide/multilayer graphene composite material.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.