CN103440996A - Method for preparing nanometer manganous-manganic oxide/carbon composite energy storage material - Google Patents

Abstract

The invention discloses a preparation method of nanometer trimanganese tetraoxide/carbon composite energy storage material: react potassium permanganate and oleic acid in an aqueous solution at a ratio of 100:1 (g/L), and disperse the obtained solid In the alcohol solvent, add elemental iodine and dissolve according to the mass ratio of 0-2:1. Then react the above solution in a reaction kettle at 120-200° C. for 12-48 hours. After centrifugal separation, washing and drying, the trimanganese tetraoxide/carbon composite material is obtained. The method can be carried out under relatively low temperature and non-alkaline conditions, and has simple process and low energy consumption. At the same time, the supercapacitive performance of the manganese tetraoxide/carbon composite material obtained by the method has been significantly improved.

Description

A preparation method of nanometer trimanganese tetraoxide/carbon composite energy storage material

technical field

The invention relates to the technical field of inorganic non-metallic composite materials, in particular to a preparation method of a nanometer trimanganese tetraoxide/carbon composite energy storage material.

Background technique

Compared with carbon materials, manganese tetraoxide energy storage materials have the advantages of large specific capacity, high energy density, and corrosion resistance. attention. However, the conductivity of trimanganese tetroxide is low, and the electron transfer resistance is large when the redox reaction occurs in the electrolyte, so that its actual specific capacity is much lower than the theoretical specific capacity. Trimanganese tetroxide is usually compounded with carbon materials to increase the electrical conductivity of the material, thereby greatly improving the specific capacity and cycle performance (Journal of Power Sources, 2002, 104: 52-61). Yin Longwei et al. (ACS Applied Materials & Interfaces, 2012, 4: 1636-1642) reported a two-step synthesis of manganese tetraoxide/carbon composites using manganese acetate monohydrate as a precursor, ethylene glycol as a nucleating agent, and polyvinylpyrrolidone as a carbon source. Material: First, hydrothermal reaction at 180°C for 48 hours, and then sintering in nitrogen atmosphere at 700°C for 4 hours. The disadvantage is that the process is complicated, high temperature is required, and energy consumption is large. Chinese patent CN101901916A reports a preparation method of carbon-supported trimanganese tetraoxide: first, carbon black is used to absorb manganese nitrate in water, after drying, the temperature is kept at 400°C for 3 hours, and the carbon-supported trimanganese tetraoxide composite material is obtained after grinding. The disadvantages are Manganese nitrate is decomposed to generate nitrogen oxide gas, which is easy to pollute the environment and requires high energy consumption. Wang Zhilin et al. (Chemistry-A European Journal, 2013, 19, 7084-7089) reported using manganese trioxide as a precursor and glucose as a carbon source for a hydrothermal reaction at 180°C for 12 hours, and then at a constant temperature of 400°C for 30 minutes in an argon atmosphere. The disadvantage of synthesizing trimanganese tetraoxide/carbon composite material is also high temperature, and the specific capacity of the trimanganese tetraoxide/carbon composite supercapacitor material synthesized by this method is only 174F/g at 1A/g.

Contents of the invention

In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a method for synthesizing nanometer trimanganese tetraoxide/carbon composite energy storage material. The technical scheme adopted in the present invention is:

The trimanganese tetraoxide precursor used is potassium permanganate;

The solvent heat medium and carbon source used are one or more of methanol, ethanol, propanol;

Elemental iodine is used to control the carbon content and crystallinity of trimanganese tetraoxide;

The mass ratio of iodine to manganese dioxide is 0-2:1.

Potassium permanganate and oleic acid are reacted in an aqueous solution at a ratio of 100:1 (g/L), the obtained solid product is dispersed in an alcohol solvent, and elemental iodine is added and dissolved at a mass ratio of 0 to 2:1. The mixed material is subjected to solvothermal reaction at 120-200° C. in a reaction kettle for 12-48 hours. After centrifugal separation, washing and drying, the nanometer trimanganese tetraoxide/carbon composite material is obtained.

Compared with the prior art, the present invention can solvothermally synthesize target nanometer manganese tetraoxide/carbon composite energy storage material at a lower temperature without high-temperature sintering and carbon activation steps, and has low energy consumption; crystal grains of manganese tetraoxide The particle size is less than 100nm. The elemental iodine required for the reaction of the method can be recycled without harmful gas emission. At the same time, the composite material synthesized by this method has excellent supercapacitive performance.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) collection of illustrative plates of nanometer trimanganese tetraoxide/carbon (20%) composite material;

Fig. 2 is the scanning electron microscope (SEM) figure of nanometer trimanganese tetraoxide/carbon (20%) composite material;

Fig. 3 is the X-ray diffraction (XRD) collection of illustrative plates of nanometer trimanganese tetraoxide/carbon (7%) composite material;

Fig. 4 is the scanning electron microscope (SEM) figure of nanometer trimanganese tetraoxide/carbon (7%) composite material;

Figure 5 is the first charge and discharge curve of the nanometer trimanganese tetraoxide/carbon composite material at 0.2A/g

Figure 6 is a comparison curve of the rate performance of trimanganese tetraoxide and trimanganese tetraoxide/carbon composite material.

Detailed ways

Embodiment 1: the preparation of nano trimanganese tetraoxide/carbon (20%) composite material

Slowly add 50 milliliters of oleic acid into 1.5 liters of 0.04 mol/L potassium permanganate solution under stirring. After reacting at room temperature for 24 hours, the obtained solid was filtered, washed and dried. Weigh 0.3 g of the above product, add 100 ml of absolute ethanol, and ultrasonically disperse. Then the solution was transferred to a reaction kettle and reacted at 160° C. for 24 hours. Centrifuge, wash and dry to obtain the product. The X-ray powder diffraction spectrum of the product (Figure 1) is consistent with the standard spectrum of manganese tetramanganese tetraoxide (JCPDS No.24-0734), but a broad diffraction peak of amorphous carbon appears near 20 °; the diffraction peak is wider , indicating that the crystal grains are small, and the average particle size calculated by the Scherrer formula is about 11.4nm. From the scanning electron microscope image (Fig. 2), it can be seen that the trimanganese tetraoxide/carbon material is irregular particles with agglomeration phenomenon, and the elemental analysis shows that the material contains 20% carbon.

Embodiment 2: the preparation of nanometer trimanganese tetraoxide/carbon (7%) composite material

Weigh 0.3 g of the solid intermediate product obtained in Example 1, add 100 ml of absolute ethanol, and ultrasonically disperse. According to the mass ratio of iodine/manganese dioxide of 1:1, 0.3 g of elemental iodine was added and dissolved. Then the solution was transferred to a reaction kettle and reacted at 160° C. for 24 hours. Centrifugal separation, washing and drying to obtain nanometer trimanganese tetraoxide/carbon composite material. X-ray powder diffraction spectrogram (Fig. 3) is consistent with the standard spectrogram (JCPDS No.24-0734) of manganese ore type trimanganese tetraoxide; compared with the product of embodiment 1, the sharpness of diffraction peak change shows that crystallinity improves, Calculated by Scherrer's formula, the average particle size is 27nm. This is because the carbon generated in the reaction is reduced, which reduces the inhibitory effect on the grain growth of manganese tetraoxide, resulting in a larger grain size, but also because the carbon coated on the grain surface is reduced, which makes the composite material particles diameter becomes smaller, see Figure 4. The elemental analysis results showed that the carbon content of the material was 7%, which was reduced by 13% compared with the product obtained in Example 1, which was consistent with the XRD test results.

Embodiment 3: Electrochemical performance test of trimanganese tetraoxide and trimanganese tetraoxide/carbon composite material

The electrochemical properties of pure trimanganese tetraoxide and trimanganese tetraoxide/carbon composite were tested at room temperature with a three-electrode system, in which the reference electrode was a saturated calomel electrode and the auxiliary electrode was a platinum electrode. The electrolyte is 1mol/L sodium sulfate solution. The constant current charge and discharge test is carried out with the Blue Electric CT2001A battery test system, and the voltage range is 0-1.0V. The result is as follows:

(1) It can be seen from Figure 5 that the specific capacities of manganese tetraoxide/carbon with a carbon content of 7% and 20% are 218.2F/g and 207.8F/g respectively when charging and discharging at a current density of 0.2A/g. . The curve of voltage versus time has a good mirror symmetry, indicating that the material has good electrochemical reversibility and excellent cycle performance.

(2) As shown in Figure 6, at different current densities, the specific capacity of trimanganese tetraoxide/carbon composites is higher than that of pure trimanganese tetraoxide. With the increase of current density, the discharge specific capacity of pure manganese tetraoxide decays quickly; the manganese tetraoxide/carbon composite material presents good high-current discharge characteristics, especially the specific capacity of the composite material with a carbon content of 7% is 5A The specific capacity at /g is still as high as 180F/g, which is only 17% lower than that at 0.2A/g.

(3) At a small current density, such as 0.2A/g, the electrolyte can fully penetrate the carbon coating and infiltrate into the material to react with trimanganese tetraoxide, and the specific capacity of composite materials with different carbon contents is very large. near. However, as the current density increases, the electrolyte cannot penetrate into the particles well, resulting in a decrease in the specific capacity. The composite material with a carbon content of 20% is more obvious due to the thicker carbon coating. Therefore, by adding elemental iodine to regulate the carbon content and carbon layer thickness in the material, the purpose of optimizing the supercapacitor energy storage performance of the material can be achieved.

Claims (5)

1. the preparation method of nano manganic manganous oxide/carbon composite energy-storage material, its concrete steps are:

Potassium permanganate is reacted according to the ratio of 100: 1 (g/L) with oleic acid in the aqueous solution, the solid product obtained is scattered in alcoholic solvent, according to 0～2: 1 mass ratio adds iodine and dissolves.Then above-mentioned solution is reacted 12～48 hours under (compactedness 60～80%) 120～200 ℃ in reactor.Centrifugation obtains mangano-manganic oxide/carbon composite after washing, drying.

2. the preparation method of a kind of nano manganic manganous oxide according to claim 1/carbon composite energy storage material year siccative, is characterized in that described alcoholic solvent is one or more in methyl alcohol, ethanol, propyl alcohol.

3. the preparation method of a kind of nano manganic manganous oxide according to claim 1/carbon composite energy-storage material, is characterized in that coming phosphorus content in controlled material and the degree of crystallinity of mangano-manganic oxide by adding iodine, thereby optimize the energy-storage property of material.

4. the preparation method of a kind of nano manganic manganous oxide according to claim 1/carbon composite energy-storage material, is characterized in that the average crystal grain particle diameter of mangano-manganic oxide in composite material is less than 100nm.

5. the preparation method of a kind of nano manganic manganous oxide according to claim 1/carbon composite energy-storage material, described energy storage material is by the described method preparation of power 1.

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