CN101521119A - Preparation method of expanded graphite/metal oxide composite material - Google Patents

Abstract

The invention provides a preparation method of an expanded graphite/metal oxide composite material for a supercapacitor electrode. The expanded graphite is prepared from 5-99 wt% of expanded graphite and 1-95 wt% of transition metal oxide, and then the process comprises the following steps: (a) Uniformly dispersing transition metal oxide nanoparticles into an aqueous solution through a surfactant to prepare a stable dispersion of inorganic nanoparticles, wherein the weight ratio of the nanoparticles is 1-70%; (b) Dipping the expanded graphite into the stable dispersion liquid of the inorganic nano particles in the step (a), standing for 10-24 hours at room temperature, and then drying for 4-20 hours at 100-200 ℃ to obtain the expanded graphite/metal oxide composite material. The method has the advantages of simple preparation process, low cost and strong industrial application value.

Description

Preparation method of expanded graphite/metal oxide composite material

(1) Technical field

The invention relates to the field of manufacturing capacitor electrode materials, in particular to a method for preparing expanded graphite/metal oxide composite materials used as super capacitor electrode materials.

(2) Background technology

Supercapacitor is a new type of energy storage element. Due to its advantages of fast storage and release of energy, it can be used as a backup power supply for electronic systems such as computers, flash and ignition devices in industrial equipment, high-power microwave and laser weapons and electric There are also broad application prospects in the hybrid power supply of automobiles. The structural properties of electrode materials play a decisive role in the performance of supercapacitors. At present, the research on electrode materials for supercapacitors mainly focuses on activated carbon, carbon nanotubes, and transition metal oxides. The carbon electrode material is cheap and the preparation process is simple, but the specific capacitance is low (50-100F/g). Metal oxide electrode materials can be classified into noble metal oxides and base metal oxides. Noble metal oxides are represented by hydrated oxides (RuO ₂ xH ₂ O), which store energy through reversible redox reactions on the surface, and their specific capacitance (720F/g) is much greater than that of carbon electrodes, but The high price limits its application prospect. Base metal oxides are represented by manganese oxide and nickel oxide. Although the specific capacity (70-300F/g) is lower than that of hydrated ruthenium oxide, they are rich in resources, low in price, and environmentally friendly, so they are potential electrode materials.

At present, metal oxide electrode materials are mainly prepared by electrochemical method, thermal decomposition method, or sol-gel method, but when the metal oxide electrode materials prepared by the above methods are used in supercapacitors, the problem of excessive material resistance often exists. Therefore, it is necessary to add carbon to the electrode material in a certain way to improve the electrical conductivity of the material and improve the performance of the capacitor. Expanded graphite is a loose and porous material made of natural graphite, which has good electrical conductivity. Adding expanded graphite to the anode of a rechargeable zinc-manganese battery can improve the electrical conductivity of the electrode and prolong the battery life. Therefore, taking advantage of the good conductive network of expanded graphite, as well as the high specific capacitance and good cycle performance of metal oxides, a composite electrode composed of expanded graphite and metal oxides is expected to obtain a new supercapacitor electrode material with excellent performance.

(3) Contents of the invention

The purpose of the present invention is to provide a preparation method of expanded graphite/metal oxide composite material which is used to prepare supercapacitor and make it have high energy density and power density.

The weight percentage of the product of the present invention consists of: expanded graphite 5-99t% and metal oxide 1-95%, preferably expanded graphite 10%-50%, metal oxide 50%-90%; One or at least two of oxides of transition metals Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ir, Ni, Pa or Ru.

Product of the present invention adopts such method to make:

(1) High energy ball milling method

According to the proportion of expanded graphite 5-99t% and metal oxide 1-95% by weight, the nano-powder of expanded graphite and transition metal oxide is added to a planetary high-energy ball mill for ball milling and mixing, and the speed is 100-250r/min. Preferably 150-250r/min; ball powder ratio 10:1-30:1, preferably 10:1-15:1; ball milling time 5-40 hours, preferably 10-20 hours to obtain expanded graphite/metal oxide composites.

(2) Sol impregnation method

The raw materials are prepared in proportions of 5-99t% of expanded graphite and 1-95% of transition metal oxides by weight percentage;

(a) Uniformly disperse the above-mentioned transition metal oxide nanoparticles into an aqueous solution through a surfactant to obtain a stable dispersion of inorganic nanoparticles, wherein the weight ratio of the nanoparticles is 1% to 70%, preferably 10 to 30%. ;

(b) Immerse expanded graphite into a stable dispersion of inorganic nanoparticles, place it at room temperature for 10 to 24 hours, and then dry it at 100°C to 200°C for 4 to 20 hours, preferably 4 to 8 hours, to obtain expanded graphite / metal oxide composites.

(3) Chemical deposition method

Add the expanded graphite to the metal nitrate or other soluble salt solution with a concentration of 0.1-3mol/L, the weight ratio of the expanded graphite to the solution is 1:5-20, after fully stirring, ultrasonically disperse for 1-20 hours, preferably for 5 to 10 hours, then add sodium hydroxide, potassium hydroxide, or sodium carbonate solution dropwise with stirring until the pH of the solution is >10. After the addition is complete, stir for 1 to 4 hours, filter and wash until the pH value is neutral, and then Dry at 100°C to 200°C for 2 to 10 hours, and finally calcine at 300°C to 800°C for 1 to 4 hours in an inert atmosphere, preferably at 300°C to 500°C for 1 to 4 hours, to obtain expanded graphite/metal oxide composite Material.

The present invention also has some technical characteristics:

1. The expansion volume of the expanded graphite described in the above methods (1), (2) and (3) is 10mL/g～600mL/g, preferably 200mL/g～600mL/g, and its purity is >99%;

2. The particle size of the nano-transition metal oxide in the above methods (1) and (2) is 5-1000 nm, preferably 5-100 nm;

3. The transition metal oxide in the above method (1), (2) is the transition metal Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ir, Ni, Pa or Ru one or at least two of the oxides;

4. Nitrate or other soluble salts of transition metals in the above-mentioned method (3) are transition metals Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ir, Ni, Pa or One or at least two of Ru nitrates or other soluble salts.

Expanded graphite/metal oxide material of the present invention is made polarized electrode according to the following steps, and carries out electrochemical performance test:

Fully mix expanded graphite/metal oxide (80wt%) and conductive carbon black (10wt%) by mechanical vibration, and then add distilled water (5wt%) and polytetrafluoroethylene PTFE (5wt%) emulsion, while adding Make it uniform by mechanical stirring, the current collector is made of foamed metal nickel, the electrode tab is made of metal nickel platinum, and the tab and the current collector are connected by spot welding; the above mixed paste is mechanically applied to the pre-cut and welded In the current collector of the tab, dry the paste-coated pole piece at 110°C for 10 hours in vacuum, then compact the dried pole piece on a hydraulic press, and trim off the burrs on the edge to make an electrode (1cm ² ) . A polypropylene separator is inserted between two identical electrodes and compressed with clamps. After the 30% KOH electrolyte was injected into the electrode, the cyclic voltammetry measurement was performed at a scan rate of 1mV/s under the condition of a constant current of 1mA and a voltage range of 0.0-0.8V with a platinum counter electrode and an SCE reference electrode. The specific capacitance can be calculated by dividing the current in cyclic voltammetry by the scan rate and the mass of the electrode active material. After charging is completed, open the circuit for 1 second, and calculate the internal resistance R from the current and voltage drop ΔV before the circuit is to be opened according to ΔV=RI.

The invention uses expanded graphite and oxide particles to compose supercapacitor electrode materials, and the prepared supercapacitor not only has high specific capacity, but also has low internal resistance. At the same time, the method uses cheap and easy-to-obtain expanded graphite as a raw material, has a simple preparation process, low cost, and has strong industrial application value.

(4) Specific implementation methods

The present invention will be further described below in conjunction with specific examples: the nano-metal oxides in the following embodiments can be purchased by commercial means, or according to [Jongnam Park, et al ultra-large-scale synthesis of monodispersenanocrystal, Nature Materials, 2004, 3 : 891; Guo Liqin et al., Preparation and Application of Nano-nickel Oxide, Chemical Engineer, 2006, 130(7): 28] and other published methods.

Example 1:

0.5g of expanded graphite (expansion volume 200mL/g) and 9.5g of nano-nickel oxide (average particle size 5nm) were used in a planetary high-energy ball mill with steel balls and a spherical tank at a rotation speed of 100rpm and a ball-to-powder ratio of 10:1 , Ball milling for 40 hours. Take it out and dry it at 100°C to make a polarized electrode for electrochemical performance test. The results are listed in Table 1.

Example 2:

5g of expanded graphite (expansion volume 600mL/g) and 5g of nano-manganese oxide (average particle size 1000nm) were ball milled in a planetary high-energy ball mill using steel balls and spherical pots at a rotation speed of 250rpm and a ball-to-powder ratio of 30:1. 5 hours. Take it out and dry it at 100°C to make a polarized electrode for electrochemical performance test. The results are listed in Table 1.

Example 3:

3g of expanded graphite (expansion volume 400mL/g) and 7g of nano-manganese oxide (average particle size 50nm) were ball milled in a planetary high-energy ball mill using steel balls and a spherical tank at a rotation speed of 250rpm and a ball-to-powder ratio of 10:1. 10 hours. Take it out and dry it at 100°C to make a polarized electrode for electrochemical performance test. The results are listed in Table 1.

Example 4:

Using an ultrasonic disperser, and using hexadecyltrimethylammonium bromide as a surfactant, 1g of nano-molybdenum oxide (average particle diameter 100nm) was uniformly dispersed in 100g of aqueous solution, and then 9g of expanded graphite (expansion volume 300mL/ g) Immerse in the above dispersion liquid, place at room temperature for 10 hours, then dry at 100°C for 20 hours, take it out and make a polarized electrode for electrochemical performance test, the measured results are listed in Table 1.

Example 5:

Using an ultrasonic disperser, and using cetyltrimethylammonium bromide as a surfactant, 7g nanometer ruthenium oxide (average particle diameter 50nm) is uniformly dispersed in 10g aqueous solution, and then 2g expanded graphite (expansion volume 400mL/ g) Immerse in the above dispersion liquid, place it at room temperature for 24 hours, then dry it at 200°C for 4 hours, take it out and make a polarized electrode for electrochemical performance testing. The measured results are listed in Table 1.

Embodiment 6:

Add 5g of expanded graphite (expansion volume 400mL/g) into 100mL of 0.1mol/L nickel nitrate solution and stir thoroughly, then ultrasonically disperse for 1 hour, then add dropwise 1mol/L sodium hydroxide solution to pH=10 while stirring After completion, stir for 4 hours, filter and wash until the pH value is neutral, dry at 100°C for 2 hours, and then calcinate at 400°C for 4 hours under an inert atmosphere. The resulting mixture was made into a polarized electrode for electrochemical performance testing, and the measured results are listed in Table 1.

Embodiment 7:

Add 4g of expanded graphite (expansion volume 400mL/g) into 20mL of 1mol/L nickel nitrate solution and stir thoroughly, ultrasonically disperse for 20 hours, then add 0.1mol/L sodium carbonate solution dropwise under stirring until pH=10. After stirring for 1 hour, filter and wash until the pH value is neutral, dry at 100°C for 10 hours, and then calcinate at 800°C for 1 hour under an inert atmosphere. The resulting mixture was made into a polarized electrode for electrochemical performance testing, and the measured results are listed in Table 1.

Embodiment 8:

Add 5g of expanded graphite (expansion volume 400mL/g) into 50mL of 3mol/L cobalt nitrate solution and stir thoroughly, ultrasonically disperse for 10 hours, then add 3mol/L potassium hydroxide solution dropwise under stirring until pH=10. After stirring for 1 hour, filter and wash until the pH value is neutral, dry at 100°C for 5 hours, and then calcinate at 400°C for 1 hour under an inert atmosphere. The resulting mixture was made into a polarized electrode for electrochemical performance testing, and the measured results are listed in Table 1.

Table 1 Electrochemical test results of expanded graphite/oxide composites

Example Unit capacitance F/g Internal resistance Ω Example 1 295 0.24 Example 2 264 0.38 Example 3 240 0.34 Example 4 265 0.25 Example 5 620 0.34 Example 6 257 0.21 Example 7 248 0.39 Example 8 148 0.32

Claims (6)

1, a kind of preparation method of expanded graphite/metal oxide composite material, it is characterized in that: by weight percentage expanded graphite 5%～99%, transition metal oxide 1%～95% after preparing raw materials, process according to the following steps: (a) uniformly dispersing transition metal oxide nanoparticles into an aqueous solution through a surfactant to prepare a stable dispersion of inorganic nanoparticles, wherein the weight ratio of the nanoparticles is 1% to 70%; (b) impregnating expanded graphite into the stable dispersion of inorganic nanoparticles described in step (a), placing it at room temperature for 10 to 24 hours, and then drying at 100°C to 200°C for 4 to 20 hours to obtain expanded graphite / metal oxide composites. 2. The preparation method of expanded graphite/metal oxide composite material according to claim 1, characterized in that the weight ratio of the nanoparticles in step (a) is 10-30%. 3. The preparation method of expanded graphite/metal oxide composite material according to claim 2, characterized in that: the drying time at 100°C-200°C described in step (b) is 4-8 hours . 4. The preparation method of expanded graphite/metal oxide composite material according to claim 3, characterized in that: the expansion volume of the expanded graphite is 10mL/g-600mL/g, and its purity is >99%. 5. The preparation method of expanded graphite/metal oxide composite material according to claim 4, characterized in that: the particle size of the transition metal oxide is 5-1000 nm. 6. The preparation method of expanded graphite/metal oxide composite material according to claim 5, characterized in that: the transition metal oxides are Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn , Fe, Co, Ir, Ni, Pa or Ru, one or at least two of the oxides.