CN104852024A - Iron trioxide monocrystal nanotube/graphene composite electrode material and preparation method thereof - Google Patents

Abstract

The invention relates to an iron trioxide monocrystal nanotube/graphene composite electrode material and a preparation method thereof. The composite electrode material of the invention is formed by coating an iron trioxide monocrystal nanotube with graphene via Van der Waals' force, wherein the mass ratio of the graphene and ferric oxide is 1:(1 to 10); the iron trioxide monocrystal nanotube is an alpha-Fe2O3 monocrystal nanotube, and the length thereof is 300 to 500 nm, and the outer diameter is 60 to 90 nm while the inside diameter is 10 to 50 nm. The method designed by the invention is simple in synthetic process and low in cost, and can be applied to lithium ion battery cathode materials. The iron trioxide monocrystal nanotube/graphene composite electrode material has excellent stability and electrochemical performance.

Description

Ferric oxide single crystal nanotube/graphene composite electrode material and preparation method thereof

technical field

The invention relates to a ferric oxide single crystal nanotube/graphene composite electrode material and a preparation method thereof.

technical background

Since Tarascon et al. reported the electrochemical performance and reaction mechanism of transition metal oxides as anode materials for lithium-ion batteries in 2000, researchers have controlled the structure and morphology of transition metal oxides to obtain high specific capacity, for The study of high-performance lithium-ion battery anode materials has opened up a very important new field. However, the rapid decline in capacity of lithium batteries using transition group metal oxides seriously hinders its further application. Significant changes can occur, and commonly used binders can easily swell in the electrolyte of a lithium battery, leading to cracking and fragmentation of the transition metal oxide electrode material. To overcome this problem, the researchers employed nanostructured transition metal oxide/graphene composites to improve the stability and electrochemical performance of Li-ion batteries.

α-Fe ₂ O ₃ , also known as hematite, widely exists in rocks and soils, and is the earliest known iron ore. α-Fe ₂ O ₃ has a hexagonal corundum structure. In the single unit cell structure, O ^2- exists in the form of hexagonal close-packed arrangement, while Fe ³⁺ is located in the 2/3 gap of the octahedral structure. α-Fe ₂ O ₃ has the characteristics of a type II semiconductor with a band gap of 2.2 eV. α-Fe ₂ O ₃ has a specific capacity of 1005 mAh/g, and has the advantages of environmental friendliness, good thermal stability, and strong corrosion resistance, which proves to be a promising electrode material for lithium batteries.

Graphene is a two-dimensional material composed of carbon atoms with sp ² hybrid orbitals forming a hexagonal honeycomb lattice. It has a special monoatomic layer structure and novel physical properties: thermal conductivity is about 5000 J/(m· K·s), the carrier mobility reaches 2×105 cm ² /(V·s), the theoretically calculated specific surface area is 2630 m ² /g, the Young's modulus is about 1100 GPa, and the fracture strength is about 125 GPa. Due to these excellent properties of graphene, in the field of lithium-ion battery electrode materials, researchers use it as a performance-enhancing phase of α-Fe ₂ O ₃ , which can be combined with α-Fe ₂ O ₃ to effectively alleviate the volume change during charge and discharge. , improve the stability and electrochemical performance of lithium-ion batteries.

The Chinese patent document with the authorized announcement number CN 103367720 A discloses a method for preparing a composite material of graphene and porous iron oxide. The principle of the invention is to use iron-containing inorganic salts as the iron source to react with graphene oxide to prepare the precursors of graphene and porous iron oxide, and then calcine them in air or inert gas to obtain graphene and porous iron oxide. composite material. The Chinese patent document with the authorized announcement number CN 103078108 A discloses a graphene-loaded rhombohedral iron oxide composite material and a hydrothermal synthesis method thereof. The invention prepares a graphene-supported rhombohedral iron oxide composite material, which is typically characterized by using graphene as the matrix skeleton, rhombohedral iron oxide grows evenly on both sides of the graphene sheet, and the particle size of the rhombohedral iron oxide is 50 ~150nm, all faces are regular parallelograms. Optimizing the production process and preparing composite materials with controllable morphology and uniform size has become a concern of researchers. However, when α-Fe2O3 is used as the negative electrode material of lithium batteries, the volume will change significantly during the insertion and extraction of lithium ions, which will lead to cracking and fragmentation of the electrode materials.

Contents of the invention

One of the objectives of the present invention is to overcome the problems of α-Fe ₂ O ₃ as a lithium battery negative electrode material, and provide a ferric oxide single crystal nanotube/graphene composite electrode material.

The second object of the present invention is to provide a method for preparing the composite electrode material, to prepare a novel lithium-ion battery negative electrode material with unique appearance, simple synthesis process and stable electrochemical performance.

To achieve the above object, the present invention adopts the following technical solutions:

A ferric oxide single crystal nanotube/graphene composite electrode material is characterized in that the composite electrode material is formed by coating graphene on the ferric oxide single crystal nanotube by van der Waals force, wherein graphene and The mass ratio of iron oxide is 1: (1-10); the ferric oxide single-crystal nanotube is α-Fe ₂ O ₃ single-crystal nanotube with a length of 300-500 nm and an outer diameter of 60-60 nm. 90 nm, with an inner diameter of 10 to 50 nm.

A method for preparing the above-mentioned ferric oxide single crystal nanotube/graphene composite electrode material is characterized in that the specific steps of the method are: graphene and α-Fe ₂ O ₃ single crystal nanotube according to 1:( The mass ratio of 1~10) is evenly dispersed in deionized water, ultrasonically dispersed for 15~30 minutes, then the dispersed solution is mixed, stirred for 5~7 days, left standing, the supernatant liquid is poured off, dried, and finally trioxide DiFe single crystal nanotube/graphene composite electrode material.

The above-mentioned α-Fe ₂ O ₃ single crystal nanotubes are prepared by mixing ferric chloride solution with a concentration of 0.5 mol/L and ammonium dihydrogen phosphate solution with a concentration of 0.02 mol/L; adding Ionized water, stirred rapidly to form a uniform mixed solution; crystallized at 200-240°C for 45-52 h; the product was centrifuged and washed with ethanol and deionized water several times; the washed product was dried to obtain α - Fe ₂ O ₃ single crystal nanotubes; the volume ratio of the ferric chloride solution, ammonium dihydrogen phosphate solution and deionized water is 10:9:(225-235).

The composite material is a graphene-coated α-Fe ₂ O ₃ single crystal nanotube material, in which the α-Fe ₂ O ₃ single crystal nanotube has a special tubular structure, which is suitable for the insertion and extraction of lithium ions, and has a large specific surface area. This composite material can not only maintain the original properties of graphene and α-Fe ₂ O ₃ , but also produce new synergistic effects. When it is used as a lithium battery negative electrode material, it can reduce the volume effect and significantly improve the electrochemical stability.

Description of drawings

Figure 1 is the XRD spectrum of α-Fe ₂ O ₃ single crystal nanotubes.

Fig. 2 is an SEM image of α-Fe ₂ O ₃ single crystal nanotubes.

Fig. 3 is a SEM image of α-Fe ₂ O ₃ single crystal nanotube/graphene composite material.

Fig. 4 is a TEM image of α-Fe ₂ O ₃ single crystal nanotubes.

Fig. 5 is an electron diffraction pattern of α-Fe ₂ O ₃ single crystal nanotubes.

Fig. 6 is a TEM image of the α-Fe ₂ O ₃ single crystal nanotube/graphene composite material.

Fig. 7 is the isothermal adsorption and desorption curves of the α-Fe ₂ O ₃ single crystal nanotube/graphene composite.

Fig. 8 is a cycle performance diagram of the α-Fe ₂ O ₃ single crystal nanotube/graphene composite material as the negative electrode.

Detailed ways

Graphene used in the present invention and α-Fe ₂ O _The preparation method of single crystal nanotube please refer to the following references:

[1]WS Hummers, RE Offeman. J. Am. Chem. Soc. 1958, 80: 1339-1340.

[2]Chun Jiang Jia, Ling Dong Sun, Zheng Guang Yan, Li Ping You, Feng Luo, Xiao Dong Han, Yu Cheng Pang, Ze Zhang, and Chun Hua Yan. Angew. Chem. Int. Ed. 2005, 44, 4328-4333.

Example 1:

1) Preparation of graphene

Under the condition of ice bath cooling and stirring, add 1.5 g NaNO ₃ (ground) to 69 mL concentrated H ₂ SO ₄ , after NaNO ₃ is completely dissolved in H ₂ SO ₄ , add 3.0 g of graphite while stirring in. Then slowly add 9.0 g KMnO ₄ , and the speed of addition is strictly controlled to ensure that the temperature is lower than 20 °C, then remove the ice bath, use a water bath and keep the temperature at about 35 °C, and keep warm for 2 h. Slowly add 137 mL of deionized water under stirring, rapidly raise the temperature to 98 °C, and then maintain it in a 98 °C water bath for 15 minutes, then further dilute to 420 mL with 60 °C deionized water, and then add 11 mL of 30% hydrogen peroxide to reduce the remaining Potassium permanganate and manganese dioxide give a bright yellow system. Filter while hot, then wash once with hydrochloric acid solution with a volume ratio of 1:10, and wash with distilled water three times. Dry in an oven at 45 °C to obtain graphite oxide. Grind the newly prepared graphite oxide into powder to ensure sufficient thermal expansion, gradually raise the temperature to 200°C, put it into the tube furnace, seal the heating tube mouth (using glycerin oil seal), and the thermocouple is in contact with the bottom of the heating tube to ensure the measurement Temperature is accurate. After thermal expansion ends, graphene is obtained.

2) Preparation of α-Fe ₂ O ₃ single crystal nanotubes

Use FeCl ₃ 6H ₂ O solid and deionized water to prepare ferric chloride aqueous solution with a concentration of 0.5 mol/L, and use NH ₄ H ₂ PO ₄ solid and deionized water to prepare ammonium dihydrogen phosphate with a concentration of 0.02 mol/L Aqueous solution; transfer ferric chloride aqueous solution (16.0 mL) and ammonium dihydrogen phosphate aqueous solution (14.4 mL) to a 500 mL beaker, and then add 369.6 mL of deionized water to the beaker to form a mixed solution; quickly stir the Mix the solution for 20-30 minutes to form a homogeneous solution; transfer the stirred homogeneous solution to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene, and keep it in an air flow oven at 220 °C for 48 h ; centrifuged, washed with ethanol and deionized water several times; the product was vacuum-dried at 80 ℃ for 12 h to obtain α-Fe ₂ O ₃ single crystal nanotubes.

3) Preparation of α-Fe ₂ O ₃ single crystal nanotube/graphene composites

Weigh 1.5 g of α-Fe ₂ O ₃ single crystal nanotubes dispersed in 250 mL deionized water with an electronic balance, and ultrasonically disperse them for 15 minutes; weigh 0.5 g of graphene dispersed in 250 mL deionized water with an electronic balance. In deionized water, ultrasonic for 15 minutes to make it completely dispersed. The two solutions after sonication were mixed and then continued to sonicate for 10 minutes, stirred at room temperature for 7 days, and dried in an oven at 60 °C for 24 hours to obtain α-Fe ₂ O ₃ single crystal nanotube/graphene composite material.

Figure 1 is the XRD spectrum of α-Fe ₂ O ₃ single crystal nanotubes, the products are all α-Fe ₂ O ₃ (hematite) (JCPDS: 33-6604), hexagonal corundum structure, space group R c; Figure 2 is the scanning electron microscope image of α-Fe ₂ O ₃ single crystal nanotubes. It can be seen from Figure 2 that α-Fe ₂ O ₃ is nanotube-shaped, with a length of 300-500 nm and an outer diameter of 60-90 nm , with an inner diameter of 10-50 nm; Fig. 3 is a scanning electron microscope image of α-Fe ₂ O ₃ single crystal nanotubes/graphene composite material. It can be seen from Fig. 3 that α-Fe ₂ O ₃ single crystal nanotubes are wrapped by graphene Fig. 4 is the TEM image of α-Fe ₂ O ₃ single crystal nanotubes. It can be seen from Fig. 4 that the color of the side wall of the material is darker than that of the middle part, which proves that the material is tubular; Fig. 5 is the α-Fe ₂ O ₃ The electron diffraction pattern of the single crystal nanotube, it can be seen from Figure 5 that the electron diffraction spots are scattered isolated points, proving that the material is a single crystal; Figure 6 is the transmission of the α-Fe ₂ O ₃ single crystal nanotube/graphene composite Electron microscope image, from Figure 6, it can be seen that α-Fe ₂ O ₃ single crystal nanotubes are covered by graphene. Figure 7 is the isothermal adsorption and desorption curves of α-Fe ₂ O ₃ single crystal nanotube/graphene composite material, it can be seen from the figure that this composite material is a mesoporous material, and this composite material has a larger specific surface area, is 31.8424 m ² /g, and the average mesopore diameter is 116.9030 Å. Figure 8 is the cycle performance diagram of α-Fe ₂ O ₃ single crystal nanotube/graphene composite material as the negative electrode of lithium ion battery. Under the condition of current density of 0.2 A g ^-1 , charge and discharge 100 times, α-Fe The ₂ O ₃ single crystal nanotube/graphene composite exhibits a stable cycling performance with a capacity maintained at around 1000 mAh g ⁻¹ .

Example 2:

1) The preparation method of graphene is the same as step 1) in Example 1.

2) Preparation of α-Fe ₂ O ₃ single crystal nanotubes

Use FeCl ₃ 6H ₂ O solid and deionized water to prepare ferric chloride aqueous solution with a concentration of 0.5 mol/L, and use NH ₄ H ₂ PO ₄ solid and deionized water to prepare ammonium dihydrogen phosphate with a concentration of 0.02 mol/L Aqueous solution; transfer ferric chloride aqueous solution (10.0 mL) and ammonium dihydrogen phosphate aqueous solution (9.0 mL) to a 300 mL beaker, and then add 235 mL of deionized water to the beaker to form a mixed solution; stir the Mix the solution for 20-30 minutes to form a homogeneous solution; transfer the stirred homogeneous solution to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene, and keep it in an air flow oven at 210 °C for 50 h ; centrifuged, washed with ethanol and deionized water several times; the product was vacuum-dried at 80 ℃ for 12 h to obtain α-Fe ₂ O ₃ single crystal nanotubes.

3) Preparation of α-Fe ₂ O ₃ single crystal nanotube/graphene composites

Use an electronic balance to weigh 1.0 g of α-Fe ₂ O ₃ single crystal nanotubes dispersed in 250 mL of deionized water, ultrasonic for 15 minutes to make it completely dispersed; use an electronic balance to weigh 0.2 g of graphene dispersed in 250 mL of deionized water In deionized water, ultrasonic for 15 minutes to make it completely dispersed. The two solutions after sonication were mixed and then continued to sonicate for 10 minutes, stirred at room temperature for 6 days, and dried in an oven at 60 °C for 24 hours to obtain α-Fe ₂ O ₃ single crystal nanotube/graphene composite material.

Example 3:

1) The preparation method of graphene is the same as step 1) in Example 1.

2) Preparation of α-Fe ₂ O ₃ single crystal nanotubes

Use FeCl ₃ 6H ₂ O solid and deionized water to prepare ferric chloride aqueous solution with a concentration of 0.5 mol/L, and use NH ₄ H ₂ PO ₄ solid and deionized water to prepare ammonium dihydrogen phosphate with a concentration of 0.02 mol/L Aqueous solution; transfer ferric chloride aqueous solution (5.0 mL) and ammonium dihydrogen phosphate aqueous solution (4.5 mL) to a 200 mL beaker, and then add 113 mL of deionized water to the beaker to form a mixed solution; stir the Mix the solution for 20-30 minutes to form a homogeneous solution; transfer the stirred homogeneous solution to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene, and keep it in an air flow oven at 230 °C for 46 h ; centrifuged, washed with ethanol and deionized water several times; the product was vacuum-dried at 80 ℃ for 12 h to obtain α-Fe ₂ O ₃ single crystal nanotubes.

3) Preparation of α-Fe ₂ O ₃ single crystal nanotube/graphene composites

Use an electronic balance to weigh 1.0 g of α-Fe ₂ O ₃ single crystal nanotubes dispersed in 250 mL of deionized water, ultrasonic for 15 minutes to make it completely dispersed; use an electronic balance to weigh 0.1 g of graphene dispersed in 250 mL of deionized water In deionized water, ultrasonic for 15 minutes to make it completely dispersed. The two solutions after sonication were mixed and then continued to be sonicated for 10 minutes, stirred at room temperature for 5 days, and dried in an oven at 60 °C for 24 hours to obtain α-Fe ₂ O ₃ single crystal nanotube/graphene composite material.

Claims (3)

1. di-iron trioxide nanometer monocrystalline pipe/graphene combination electrode material, it is characterized in that this combination electrode material is that Graphene is coated on di-iron trioxide nanometer monocrystalline pipe by Van der Waals force and is formed, wherein the mass ratio of Graphene and iron oxide is 1:(1 ~ 10); Described di-iron trioxide nanometer monocrystalline pipe is α-Fe ₂o ₃nanometer monocrystalline pipe, its length is 300 ~ 500 nm, and external diameter is 60 ~ 90 nm, and internal diameter is 10 ~ 50 nm.

2. prepare a method for di-iron trioxide nanometer monocrystalline pipe/graphene combination electrode material according to claim 1, it is characterized in that the concrete steps of the method are: by Graphene and α-Fe ₂o ₃1:(1 ~ 10 pressed by nanometer monocrystalline pipe) mass ratio in deionized water dispersed, ultrasonic disperse 15 ~ 30 minutes, then mixes scattered solution, stir 5 ~ 7 days, leave standstill, outwell supernatant liquor, drying, finally obtains di-iron trioxide nanometer monocrystalline pipe/graphene combination electrode material.

3. method according to claim 2, is characterized in that described α-Fe ₂o ₃the preparation method of nanometer monocrystalline pipe is: the ammonium dihydrogen phosphate mixing of to be the liquor ferri trichloridi of 0.5 mol/L and concentration by concentration be 0.02mol/L; In mixed solution, add deionized water, rapid stirring, make it to form homogeneous mixed solution; Crystallization 45 ~ 52 h at 200 ~ 240 DEG C; Product, through centrifugation, repeatedly washs with ethanol and deionized water; Afterproduct will be washed dry, obtain α-Fe ₂o ₃nanometer monocrystalline pipe; The volume ratio of described liquor ferri trichloridi, ammonium dihydrogen phosphate and deionized water is 10:9:(225 ~ 235).