CN104617290A - A uniform precipitation method for preparing Fe2O3 nanobelts and their composite materials with carbon - Google Patents

Abstract

A uniform precipitation method for preparing Fe ₂ O ₃ nanobelts and their composite materials with carbon, using complexing agent C ₂ O ₄ ^2- to react with Fe ³⁺ in solution to generate soluble [Fe(C ₂ O ₄ ) ₃ ] ³⁺ complex, and then use the reducing agent to reduce Fe(III) to Fe(II), Fe(II) reacts with C ₂ O ₄ ^2- in the solution to form FeC ₂ O ₄ precipitate or evenly deposit on carbon Precipitation of FeC ₂ O ₄ on the solid material to obtain FeC ₂ O ₄ or FeC ₂ O ₄ /carbon composite material precursor; and then calcination at a certain temperature to obtain Fe ₂ O ₃ nanobelts or Fe ₂ O ₃ nanobelts/carbon composite material. Fe ₂ O ₃ nanoribbons/carbon exhibit excellent electrochemical performance when used as anode materials for lithium-ion batteries. Among them, on the one hand, carbonaceous materials can effectively buffer the volume change of Fe ₂ O ₃ during charging and discharging, and improve the cycle stability of materials. On the other hand, carbonaceous materials form an effective conductive network, which is conducive to the rapid transmission of electrons and improves rate performance of the material. In addition, the preparation method involved in the present invention has low equipment requirements, mild preparation conditions, simple process, short cycle and low cost, and is suitable for large-scale production.

Description

A uniform precipitation method for preparing Fe2O3 nanobelts and their composite materials with carbon

technical field

The invention belongs to the fields of new energy materials and electrochemistry, and in particular relates to a _uniform precipitation method for preparing _Fe2O3 nanobelts and their composite materials with carbon.

Background technique

Lithium-ion battery has the advantages of high working voltage, large specific energy, no memory effect, no pollution, low self-discharge rate and long service life, and is currently the best secondary battery system with comprehensive performance. It has been widely used in portable consumer electronics fields such as mobile phones, notebook computers, and digital cameras, and is gradually expanding to fields such as electric vehicles and energy storage batteries.

Negative electrode material is one of the key components of lithium-ion batteries and a key factor determining the overall performance of lithium-ion batteries. At present, the anode materials in commercialized lithium ion batteries are mainly graphite carbon materials, and their theoretical specific capacity is 372mAh·g ^-1 , which cannot meet the needs of the new generation of high specific capacity lithium ion batteries. Therefore, research and development of high specific capacity The new negative electrode material has become one of the hot spots in the research of lithium-ion batteries. In the research of new negative electrode materials with high specific capacity, silicon-based materials, tin-based materials, and transition metal oxides (such as Fe ₂ O ₃ , Fe ₃ O ₄ , NiO, Co ₃ O ₄ ) have all received great attention. focus on. Among them, Fe ₂ O ₃ is regarded as a potential anode material for lithium-ion batteries because of its high specific capacity (theoretical capacity is 1007mAh·g ^-1 ), low cost, environmental friendliness and abundant raw materials. However, Fe ₂ O ₃ is accompanied by a large volume change during the intercalation/delithiation process, and the material is prone to agglomeration and pulverization, resulting in rapid capacity decay and poor cycle stability; at the same time, Fe ₂ O ₃ is a semiconductor and has poor conductivity. , resulting in unsatisfactory rate performance. Therefore, how to improve the cycle stability and rate performance of Fe ₂ O ₃ anode materials has become the premise and key to realize its practical application. In order to solve the above problems, researchers have done a lot of modification work on Fe ₂ O ₃ . At present, many modification measures can be divided into two categories: designing and preparing Fe ₂ O ₃ with nanostructure and constructing Fe ₂ O ₃ composite materials. Designing and preparing Fe ₂ O ₃ with a nanostructure can reduce the transfer distance of electrons or ions and improve the electrochemical reactivity. At the same time, the nanostructure can effectively alleviate its volume effect during charge and discharge, thereby improving its electrochemical performance. Constructing _{Fe2O3 composites} is another commonly used and effective modification method, combining _Fe2O3 with active or inactive substances with good electrical _conductivity and small volume effect, on the one hand these materials can effectively buffer _{Fe2O 3} The volume change during charge and discharge, on the other hand, can provide an effective electron transfer channel, thereby effectively improving the electrochemical performance of the material. The construction of Fe ₂ O ₃ -carbon composites is a typical representative of Fe ₂ O ₃ -based composites.

Representative _{Fe2O3 -} based negative electrode materials in literature and patents include:

Using the microemulsion formed by glycerol in water as a template, Wang et al. prepared Fe ₂ O ₃ hollow spheres with a diameter of about 1 μm by a hydrothermal method. When they were used as negative electrode materials, they showed good cycle stability, and they were stable at 200mA· The current density of g ^-1 is charged and discharged, and its reversible capacity can still be maintained at 710mAh g ^-1 after 100 cycles, which is obviously better than that of solid Fe ₂ O ₃ particles (J.Am.Chem.Soc.,2011,133( 43), 17146-17148). Liu et al. prepared Fe ₂ O ₃ nanorods with a diameter of about 60-80nm by a hydrothermal method. When charged and discharged at a rate of 0.1C, the initial discharge capacity was 1332mAh·g ^-1 , and the capacity after 30 cycles was 763mAh· g ^-1 , much higher than 112mAh·g ^-1 of commercial microscale Fe ₂ O ₃ . (Electrochimica Acta, 2009, 54(6), 1733-1736). Gao et al. synthesized Fe ₂ O ₃ nanoribbons with a width of about 20-40 nm by microemulsion method. When used as anode materials for lithium-ion batteries, they showed high intercalation and delithiation activities, and their initial discharge and charge capacities were respectively 1068 and 701mAh·g ^-1 , but poor cycle stability. (CrystEngComm, 2011, 13(20), 6045-6049). Yu et al. used chemical vapor deposition to prepare CNTs with an inner diameter of about 55 nm using AAO as a template, and then filled Fe ₂ O ₃ into CNTs by impregnation-calcination method, and prepared Fe ₂ O ₃ -CNTs after removing the AAO template. composite material. The composite material has a reversible capacity of 768mAh·g ^-1 after 40 cycles of charging and discharging at a current density of 35mA·g ^-1 (Chem.Commun, 2010, 46(45), 8576-8578). In the patent CN102427129A, Pan Hongge et al. used commercial Fe ₂ O ₃ powder and carbon material to conduct ball milling treatment combined with heat treatment process to prepare iron-based oxide/carbon composite material. Cycling stability, but relatively low specific capacity. In the patent CN103227324A, Zhao Hailei et al. used the sol-gel method to prepare an iron oxide precursor with an airgel structure. After further heat treatment, an iron oxide/carbon composite material was prepared. This material has a high initial reversibility when used as a negative electrode. Capacity, but the cycle stability is not ideal.

To sum up, in literature and patent reports, iron oxide-based negative electrode materials are mostly prepared by template method, hydrothermal method, microemulsion method and sol-gel method for the research on iron oxide materials as anode materials for lithium-ion batteries. Most of these methods have complicated technical process, high cost and poor product consistency.

In the present invention, for the first time, a simple reduction reaction is used to adjust the reduction of ferric ions in the solution to ferrous ions, which promotes the occurrence of a uniform precipitation reaction, generates ferrous oxalate precipitates or evenly deposits ferrous oxalate precipitates on carbonaceous materials, and prepares Ferrous oxalate or ferrous oxalate/carbon composite material; Fe ₂ O ₃ nanobelts or Fe ₂ O ₃ nanobelts/carbon composite materials were prepared after calcining at a certain temperature. The method has simple process, mild preparation conditions, low cost, good repeatability and is convenient for large-scale production. The synthesized material has a good micro-composite structure and exhibits excellent electrochemical performance when it is used as an anode material for a lithium-ion battery.

Contents of the invention

The purpose of the present invention is to provide a uniform precipitation method for preparing Fe ₂ O ₃ nanobelts and their composite materials with carbon, aiming at the shortcomings of poor cycle performance and poor rate performance of current Fe ₂ O ₃ negative electrode materials.

The invention provides a uniform precipitation method for preparing Fe ₂ O ₃ nanobelts and their composite materials with carbon, using complexing agent C ₂ O ₄ ^2- to react with Fe ³⁺ in solution to generate soluble [Fe( C ₂ O ₄ ) ₃ ] ³⁺ complex, and then use a reducing agent to reduce Fe(III) to Fe(II), Fe(II) reacts with C ₂ O ₄ ^2- in the solution to form FeC ₂ O ₄ precipitate or Precipitation of FeC ₂ O ₄ uniformly deposited on the carbonaceous material to obtain FeC ₂ O ₄ or FeC ₂ O ₄ /carbon composite material precursor; after calcination at a certain temperature, Fe ₂ O ₃ nanobelts or Fe ₂ O ₃ nanoribbon/carbon composite material; specific steps are as follows:

1) Disperse carbonaceous material: Weigh the required mass of carbonaceous material and evenly disperse it in the solvent to form a suspension;

Among them, the dispersion method of carbonaceous material is one or both of ultrasonic dispersion and stirring dispersion;

2) Prepare the reaction solution: dissolve the trivalent inorganic iron salt and the complexing agent in the solvent, or dissolve it in the suspension containing carbon materials; then add the reducing agent to it, and continuously stir the reaction to obtain the precipitated product;

3) The precipitated product obtained in step 2) is centrifuged or filtered, separated, washed, and vacuum-dried at 40-85°C to obtain FeC ₂ O ₄ or FeC ₂ O ₄ /carbon composite material;

4) Calcining the FeC ₂ O ₄ or FeC ₂ O ₄ /carbon composite material obtained in step 3) at 250-900°C for 0.5-24 hours in a protective atmosphere to prepare Fe ₂ O ₃ nanobelts or Fe ₂ O ₃ Nanoribbon/carbon composites.

In the uniform precipitation method for preparing _Fe2O3 nanobelts and their composite materials with carbon provided by the present invention, the carbonaceous materials described in step 1) are carbon _nanotubes , carbon aerogels, mesoporous carbon, expanded graphite, One or more of graphene, conductive carbon black, Cabot superconductive carbon black BP2000, and activated carbon; the conductivity of carbonaceous materials is greater than or equal to 0.1S·cm ^-1 , and the specific surface area is greater than or equal to 50m ² · g ^-1 , the pore volume is greater than or equal to 0.2 cm ³ ·g ^-1 .

In the uniform precipitation method for preparing Fe ₂ O ₃ nanobelts and their composite materials with carbon provided by the present invention, the ultrasonic dispersion described in step 1) is to use an ultrasonic cleaning machine or a cell pulverizer for ultrasonic dispersion, and the ultrasonic power is 25-1000W , the ultrasonic time is 0.1-3h; the stirring and dispersing is magnetic stirring or mechanical stirring, the stirring rate is 400-1000rmp, and the stirring time is 0.1-3h.

_In the uniform precipitation method for preparing _Fe2O3 nanobelts and their composite materials with carbon provided by the present invention, the solvents described in step 1) and step 2) are deionized water, methanol, ethanol, propanol, and isopropanol , one or more of ethylene glycol.

In the uniform precipitation method for preparing Fe ₂ O ₃ nanobelts and their composite materials with carbon provided by the present invention, the trivalent inorganic iron salt described in step 2) is one or both of ferric nitrate, ferric chloride, and ferric sulfate. more than one species; wherein, the molar ratio of iron ions to carbonaceous materials is 1:1.5-100.

In the uniform precipitation method _for preparing _Fe2O3 nanobelts and their composite materials with carbon provided by the present invention, the complexing agent described in step 2) is one of potassium oxalate, sodium oxalate, lithium oxalate, ammonium oxalate, and oxalic acid or two or more; wherein, the molar ratio of iron ions in the trivalent inorganic iron salt to oxalate ions in the complexing agent is 1:0.5-6.

In the uniform precipitation method for preparing _Fe2O3 nanobelts and their composite materials with carbon provided by the present invention _, the reducing agent described in step 2) is sodium borohydride, potassium borohydride, hydrazine hydrate, sodium hypophosphite, ascorbic acid One or more of them; wherein, the molar ratio of iron ions in the trivalent inorganic iron salt to the reducing agent is 1:0.5-3.

In the uniform precipitation method for _{preparing Fe2O3} nanobelts and their composite materials with carbon provided by the present invention, after adding the reducing agent in step 2), the stirring speed is 400-1000rmp, the reaction temperature is 0-90°C, and the reaction time is 0.1～3h.

In the uniform precipitation method for preparing Fe ₂ O ₃ nanobelts and their composite materials with carbon provided by the present invention, the calcination temperature in step 4) is 300-700°C.

In the uniform precipitation method for preparing Fe ₂ O ₃ nanobelts and their composite materials with carbon provided by the present invention, the protective atmosphere described in step 4) is one or more of air, oxygen, argon, and nitrogen.

In the uniform precipitation method for preparing _Fe2O3 nanobelts and their composite _materials with _carbon provided by the present invention, the mass fraction of _Fe2O3 in the _{prepared Fe2O3} nanobelts and their composite materials with carbon is 5 %～98%, preferably 25%～90%.

The Fe ₂ O ₃ nanobelt prepared by the method of the invention and its composite material with carbon are applied to negative electrode materials in electrochemical energy storage devices of lithium ion batteries or asymmetric supercapacitors.

The beneficial effects that the present invention has are:

First, the complexing agent C ₂ O ₄ ^2- undergoes a complexation reaction with the reactant Fe ³⁺ in the solution. When a reducing agent is added to the phase solution, Fe(III) is reduced to Fe(II), and rapidly reacts with the surrounding The C ₂ O ₄ ^2- undergoes a compound reaction to generate FeC ₂ O ₄ precipitates. Since Fe ²⁺ ions are produced from the inside of the solution, the phenomenon of excessive local concentration can be effectively avoided. Therefore, Fe ²⁺ ions react with C ₂ O ₄ ^2- in the solution to uniformly generate FeC ₂ O ₄ precipitation, or The FeC ₂ O ₄ precipitate was uniformly deposited on the carbonaceous material, and the FeC ₂ O ₄ /carbon composite material was synthesized. Secondly, C ₂ O ₄ ^2- also acts as a directing agent to promote the formation of nanoribbon materials. In the _FeC2O4 or _FeC2O4 /carbon _{composite material prepared by the present invention, FeC2O4 is in nano-ribbon structure, and the Fe2O3 or Fe2O3 / carbon composite material is} prepared after calcining. In Fe ₂ O ₃ and Fe ₂ O ₃ /carbon composites, Fe ₂ O ₃ maintains the nanoribbon structure of its precursor, ferrous oxalate, and is evenly distributed on the carbon material, forming a good composite structure. Third, _Fe2O3 nanoribbons/carbon exhibit excellent electrochemical performance when used as anode materials _for lithium-ion batteries. On the one hand, compared with micron-sized commercial Fe ₂ O ₃ , Fe ₂ O ₃ nanobelts have higher electrochemical activity and excellent structural stability; on the other hand, in composite materials, carbonaceous materials can effectively Buffering the volume change of Fe ₂ O ₃ during charge and discharge, and at the same time improving the conductivity of the material, thus further improving the cycle performance and rate performance of the material. Finally, the preparation method of the present invention requires simple production equipment, mild preparation conditions, simple process, short cycle and low cost, and is suitable for large-scale production.

Description of drawings

Fig. 1 is the Fe that embodiment ₂ obtains O The _nanobelt /carbon X-ray diffraction figure;

Fig. 2 is the _Fe2O3 nanobelt/carbon TEM figure that embodiment ₃ obtains;

Fig. 3 is the _Fe2O3 nanobelt/carbon charge-discharge curve that embodiment 4 obtains _;

Fig. 4 is the Fe that embodiment ₆ obtains O The cycle performance curve of _nanobelt /carbon;

FIG. 5 is the rate performance curve of the Fe ₂ O ₃ nanobelt/carbon obtained in Example 8.

Detailed ways

The following examples will further illustrate the present invention, but do not limit the present invention thereby.

Example 1

First, 0.5g FeCl ₃ ·6H ₂ O and 0.134g sodium oxalate were respectively dissolved in 200mL deionized water. Take 0.20 g of ascorbic acid and dissolve it in about 5 mL of deionized water, then add the ascorbic acid aqueous solution dropwise to the stirring solution above, and continue to stir for about 3 hours after the addition is complete. After centrifugal separation, the product was washed three times with deionized water, and then dried in a vacuum oven at 85° C. to obtain a yellow product. The obtained yellow product was placed in a porcelain boat, and heat-treated at 700° C. for 3 hours in an air atmosphere to obtain the final product Fe ₂ O ₃ nanobelts.

Example 2

First, take 25.0 mg of carbon nanotubes (CNTs), add it into 200 mL of deionized water, and stir it ultrasonically for 3 h. Then, 6.06g of Fe(NO ₃ ) ₃ ·9H ₂ O and 6.6g of ammonium oxalate were sequentially added to the above dispersion of CNTs, and stirred to dissolve them. Take 3.52g of sodium hypophosphite and dissolve it in about 10mL of deionized water, then add the aqueous solution of sodium hypophosphite dropwise to the stirring mixture of Fe(NO ₃ ) ₃ , ammonium oxalate and CNTs. The stirring reaction was continued for about 0.5h. After centrifugation, the product was washed three times with ethanol, and then dried in a vacuum oven at 85°C to obtain a black product. The obtained black product was placed in a porcelain boat and heat-treated at 250° C. for 3 hours in an air atmosphere to obtain the final Fe ₂ O ₃ -CNTs composite material.

Figure 1 is the XRD pattern of the prepared Fe ₂ O ₃ /carbon. It can be seen from the figure that the diffraction peak of the sample at 2θ=26.2° corresponds to the diffraction peak of CNTs on the crystal plane (002), and there are obvious The diffraction peak corresponding to the α-Fe ₂ O ₃ phase indicates that the prepared sample is a composite material of Fe ₂ O ₃ and CNTs.

Example 3

First, take 100 mg of CNTs, add it into 200 mL of deionized water, and disperse for 0.5 h with ultrasonic-assisted stirring. Then, 0.5 g of FeCl ₃ ·6H ₂ O and 0.134 g of sodium oxalate were sequentially added to the above dispersion of CNTs, and stirred to dissolve them. Dissolve 0.20 g of ascorbic acid in about 5 mL of deionized water, then add the aqueous solution of ascorbic acid dropwise to the stirring mixture of FeCl ₃ , sodium oxalate and CNTs, and continue stirring for about 3 hours after the addition is complete. After centrifugation, the product was washed three times with ethanol, and then dried in a vacuum oven at 85°C to obtain a black product. The obtained black product was placed in a porcelain boat, heat-treated at 300°C for 0.5h in an air atmosphere, and then heat-treated at 700°C for 3h under an argon or nitrogen atmosphere to obtain the final product Fe ₂ O ₃ -CNTs composite material .

Figure 2 is the TEM image of the prepared Fe ₂ O ₃ nanoribbon/carbon. It can be seen from the figure that Fe ₂ O ₃ forms a nanoribbon structure and spreads on the CNTs, forming a good microscopic composite structure.

Example 4

First, 75 mg of graphene (GO) was taken, added to 200 mL of deionized water and ethanol, and dispersed for 2 h with ultrasonic-assisted stirring. Then, 0.80 g of Fe ₂ (SO ₄ ) ₃ ·9H ₂ O and 0.70 g of oxalic acid were sequentially added to the above GO dispersion, and stirred to dissolve them. Dissolve 0.20 g of sodium borohydride in about 5 mL of deionized water, then add the sodium borohydride solution dropwise to the stirring mixture of Fe ₂ (SO ₄ ) ₃ , oxalic acid and GO, and continue stirring after the addition is complete Reaction about 1h. After centrifugation, the product was washed three times with ethanol, and then dried in a vacuum oven at 60°C to obtain a black product. The obtained black product was placed in a porcelain boat and heat-treated at 300° C. for 1 h in an air atmosphere to obtain the final Fe ₂ O ₃ -GO composite material.

The prepared Fe ₂ O ₃ /GO composite material was used as the negative electrode material of the lithium ion battery, and was mixed with acetylene black and PVDF according to the mass ratio of 80:10:10 to obtain a slurry. The slurry was uniformly coated on the copper foil to obtain the working electrode, the lithium sheet was used as the counter electrode, the Celgard2325 polypropylene film was used as the separator, and 1MLiPF ₆ /EC+DMC (EC:DMC=1:1) was used as the electrolyte, and the electrode was filled with argon Assemble a button cell in an air-conditioned glove box.

The above batteries were charged and discharged on the Land charge and discharge instrument. Charge and discharge voltage range 0.005 ~ 3.0V. Charged and discharged at a constant current of 100mA·g ^-1 , its first reversible discharge and charge specific capacities are 1347.8 and 1033.9mAh g ^-1 , respectively. Fig. 3 is the charge-discharge curves of the prepared Fe ₂ O ₃ -GO composite material in the first two cycles.

Example 5

First, take 200 mg of mesoporous carbon, add it into 200 mL of deionized water and ethanol mixture, and disperse it for 1 h with ultrasonic-assisted stirring. Then, 52.5 mg of Fe(NO ₃ ) ₃ ·9H ₂ O and 55 mg of oxalic acid were sequentially added to the above mesoporous carbon dispersion, and stirred to dissolve. Take 0.30mL hydrazine hydrate solution and add it dropwise to the stirring mixture of Fe(NO ₃ ) ₃ , oxalic acid and mesoporous carbon, and continue stirring for about 1 hour after the addition is complete. After centrifugation, the product was washed three times with ethanol, and then dried in a vacuum oven at 85°C to obtain a black product. The obtained black product was placed in a porcelain boat and heat-treated at 300° C. for 1 h in an air atmosphere to obtain the final product Fe ₂ O ₃ -mesoporous carbon composite material.

Example 6

First, take 50 mg of carbon airgel, add it into 200 mL of deionized water, and disperse for 3 h with ultrasonic-assisted stirring. Then, 0.60 g of Fe(NO ₃ ) ₃ ·9H ₂ O and 0.70 g of potassium oxalate were sequentially added to the above carbon airgel dispersion, and stirred to dissolve. Dissolve 0.40g of ascorbic acid in about 5mL of deionized water, then add the ascorbic acid aqueous solution dropwise to the stirring mixture of Fe(NO ₃ ) ₃ , oxalic acid and carbon aerogel, and continue to stir for about 3h. After centrifugation, the product was washed three times with ethanol, and then dried in a vacuum oven at 85°C to obtain a black product. The obtained black product was placed in a porcelain boat, heat-treated at 250°C for 3 hours in an air atmosphere, and then heat-treated at 500°C for 1 hour to obtain the final Fe ₂ O ₃ -carbon airgel composite material.

The prepared Fe ₂ O ₃ /carbon airgel material was used as the negative electrode material of the lithium ion battery, and was mixed with acetylene black and PVDF according to the mass ratio of 80:10:10 to obtain a slurry. The slurry was uniformly coated on the copper foil to obtain the working electrode, the lithium sheet was used as the counter electrode, the Celgard2325 polypropylene film was used as the separator, and 1MLiPF ₆ /EC+DMC (EC:DMC=1:1) was used as the electrolyte, and the electrode was filled with argon Assemble a button cell in an air-conditioned glove box.

The above batteries were charged and discharged on the Land charge and discharge instrument. The charging and discharging voltage ranges from 0.005 to 3.0V, and the current density is 100mA·g ^-1 . Fig. 4 is the cycle performance curve of the prepared Fe ₂ O ₃ -carbon airgel composite material.

Example 7

First, take 100 mg of commercialized BP2000, add it into 200 mL of ethanol, and disperse for 3 h with ultrasonic-assisted stirring. Then, 0.60g FeCl ₃ ·9H ₂ O and 0.70g oxalic acid were respectively added to the above-mentioned dispersion of BP2000 in sequence, and stirred to dissolve them. Take 0.4mL of hydrazine hydrate solution and add dropwise to the stirring mixture of FeCl ₃ , oxalic acid and BP2000, and continue stirring for about 3 hours after the addition is complete. After centrifugation, the product was washed three times with ethanol, and then dried in a vacuum oven at 60°C to obtain a black product. The obtained black product was placed in a porcelain boat and heat-treated at 400° C. for 1 h in an air atmosphere to obtain the final Fe ₂ O ₃ -BP2000 composite material.

Example 8

First, take 100 mg of conductive carbon black, add it to 200 mL of deionized water and ethanol mixture, and disperse it for 1 h with ultrasonic-assisted stirring. Then, 0.80 g of Fe(NO ₃ ) ₃ ·9H ₂ O and 0.90 g of oxalic acid were sequentially added to the above mesoporous carbon dispersion, and stirred to dissolve them. Dissolve 0.5g of potassium borohydride in about 5mL of deionized water, and add it dropwise to the stirring mixture of Fe(NO ₃ ) ₃ , oxalic acid and mesoporous carbon, and continue to stir for about 1h. After centrifugation, the product was washed three times with ethanol, and then dried in a vacuum oven at 85°C to obtain a black product. The obtained black product was placed in a porcelain boat and heat-treated at 300° C. for 1 h in an air atmosphere to obtain the final product Fe ₂ O ₃ -carbon composite material.

The prepared Fe ₂ O ₃ /conductive carbon black composite material was used as the negative electrode material of lithium ion battery, and was mixed with acetylene black and PVDF according to the mass ratio of 80:10:10 to obtain a slurry. The slurry was uniformly coated on the copper foil to obtain the working electrode, the lithium sheet was used as the counter electrode, the Celgard2325 polypropylene film was used as the separator, and 1MLiPF ₆ /EC+DMC (EC:DMC=1:1) was used as the electrolyte, and the electrode was filled with argon Assemble a button cell in an air-conditioned glove box.

The above batteries were charged and discharged on the Land charge and discharge instrument. Charge and discharge voltage range 0.005 ~ 3.0V. Fig. 5 is a rate performance curve of the prepared Fe ₂ O ₃ -mesoporous carbon composite.

Claims (13)

1. prepare Fe for one kind ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that:

Utilize complexing agent C ₂o ₄ ^2-with the Fe in solution ³⁺reaction generates [Fe (C ₂o ₄) ₃] ³⁺complex compound, recycling reducing agent reduction Fe(III) be Fe(II), Fe(II) with solution in C ₂o ₄ ^2-reaction generates FeC ₂o ₄precipitation, or generate the FeC deposited equably on the carbonaceous material ₂o ₄precipitation, obtains ferrous oxalate or ferrous oxalate/carbon composite; Fe has been obtained again after uniform temperature calcination processing ₂o ₃nanobelt or Fe ₂o ₃nanobelt/carbon composite; Concrete steps are as follows:

1) dispersed carbon material: take required quality carbonaceous material and be dispersed in solvent and form suspension-turbid liquid;

Wherein, the dispersing mode of carbonaceous material is one or both in ultrasonic disperse, dispersed with stirring;

2) reaction solution is prepared: trivalent inorganic molysite and complexing agent are dissolved in solvent, then are added wherein by reducing agent, and continuous stirring reaction, be precipitated product;

Or trivalent inorganic molysite and complexing agent are dissolved in the suspension-turbid liquid containing material with carbon element, then reducing agent is added wherein, and continuous stirring reaction, be precipitated product;

3) by step 2) the centrifugal or isolated by filtration of the precipitated product that obtains, washing, and in 40 ~ 85 DEG C of vacuumizes, obtain FeC ₂o ₄or FeC ₂o ₄/ carbon composite;

4) FeC step 3) obtained ₂o ₄or FeC ₂o ₄/ carbon composite calcines 0.5 ~ 24h in protective atmosphere at 250 ~ 900 DEG C, obtained Fe ₂o ₃nanobelt or Fe ₂o ₃nanobelt/carbon composite.

2. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: the carbonaceous material described in step 1) is one or more in carbon nano-tube, carbon aerogels, mesoporous carbon, expanded graphite, Graphene, conductive carbon black, Cabot Super-conductive carbon BP2000, active carbon;

The conductivity of carbonaceous material is more than or equal to 0.1Scm ^-1, specific area is more than or equal to 50m ²g ^-1, pore volume is more than or equal to 0.2cm ³g ^-1.

3. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: the ultrasonic disperse described in step 1) is for adopting supersonic wave cleaning machine or cell disruptor ultrasonic disperse, and ultrasonic power is 25 ~ 1000W, and ultrasonic time is 0.1 ~ 3h;

Described dispersed with stirring is magnetic agitation or mechanical agitation, and the speed of stirring is 400 ~ 1000rmp, and mixing time is 0.1 ~ 3h.

4. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: step 1) and step 2) described in solvent be deionized water, methyl alcohol, ethanol, propyl alcohol, isopropyl alcohol, ethylene glycol one or more.

5. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: step 2) described in trivalent inorganic molysite be ferric nitrate, iron chloride, ferric sulfate one or more;

Wherein, the mol ratio of iron ion and carbonaceous material is 1:1.5 ~ 100.

6. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: step 2) described in complexing agent be potassium oxalate, sodium oxalate, lithium oxalate, ammonium oxalate, oxalic acid one or more;

Wherein, the mol ratio of the iron ion in trivalent inorganic molysite and complexing agent oxalate ion is 1:0.5 ~ 6.

7. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: step 2) described in reducing agent be one or more in sodium borohydride, potassium borohydride, hydrazine hydrate, inferior sodium phosphate, ascorbic acid;

Wherein, the iron ion in trivalent inorganic molysite and the mol ratio of reducing agent are 1:0.5 ~ 3.

8. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: step 2) in add reducing agent after, mixing speed is 400 ~ 1000rmp, and reaction temperature is 0 ~ 90 DEG C, and the reaction time is 0.1 ~ 3h.

9. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: the calcining heat described in step 4) is 300 ~ 700 DEG C.

10. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: the protective atmosphere described in step 4) be air, oxygen, argon gas, nitrogen one or more.

11. prepare Fe according to described in claim 1 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: the Fe of described preparation ₂o ₃nanobelt and with the Fe in the composite material of carbon ₂o ₃mass fraction is 5% ~ 98%.

12. prepare Fe according to described in claim 11 ₂o ₃the homogeneous precipitation method of nanobelt and the composite material with carbon thereof, is characterized in that: the Fe of described preparation ₂o ₃nanobelt and with the Fe in the composite material of carbon ₂o ₃mass fraction is 25% ~ 90%.

The Fe that described in 13. claims 1 prepared by method ₂o ₃nanobelt and be applied to the negative material in the electrochemical energy storage device of lithium ion battery or asymmetric type supercapacitor with the composite material of carbon.