CN101521119B

CN101521119B - Preparation method of expanded graphite/metal oxide composite material

Info

Publication number: CN101521119B
Application number: CN2009101331195A
Authority: CN
Inventors: 范壮军; 魏彤; 闫俊; 郄忠伟; 王珊珊
Original assignee: Harbin Engineering University
Current assignee: Harbin Engineering University
Priority date: 2007-04-20
Filing date: 2007-04-20
Publication date: 2011-03-16
Anticipated expiration: 2027-04-20
Also published as: CN101521119A

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

(I) technical field

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

(II) background of the invention

The super capacitor is a new type of energy storage element, and owing to its advantages of quick energy storage and release, it may be used as stand-by power supply for computer and other electronic systems, as well as flash and ignition device in industrial equipment, in high power microwaveAnd the hybrid power supply of laser weapons and electric automobiles, and the like. The structural properties of the electrode material are decisive for the performance of the supercapacitor. At present, research on electrode materials of supercapacitors mainly focuses on activated carbon, carbon nanotubes, transition metal oxides, and the like. The carbon electrode material has low price and simple preparation process, but the specific capacitance is lower (50-100F/g). Metal oxide electrode materials can be divided into precious metal oxides and base metal oxides. Noble metal oxides are represented by hydrated oxide (RuO) ₂ .xH ₂ O), the energy storage is realized through the redox reversible reaction generated on the surface, the specific capacitance (720F/g) is far larger than that of the carbon electrode, but the expensive price of the noble metal limits the application prospect. The base metal oxide is represented by manganese oxide and nickel oxide, has a specific capacity (70-300F/g) lower than that of hydrated ruthenium oxide, but is abundant in resources, low in price and environment-friendly, so that the base metal oxide is a potential electrode material.

At present, the metal oxide electrode material is mainly prepared by an electrochemical method, a thermal decomposition method or a sol-gel method, but when the metal oxide electrode material prepared by the method is used for a super capacitor, the problem of overlarge material resistance is often existed. Therefore, carbon needs to be added to the electrode material in a certain way to improve the conductivity of the material and improve the performance of the capacitor. The expanded graphite is a loose and porous material prepared from natural graphite, has good conductivity, and can be added into the anode of a rechargeable zinc-manganese battery to improve the conductivity of the electrode and prolong the service life of the battery. Therefore, by utilizing the good conductive network of the expanded graphite, the high specific capacitance and the good cycle performance of the metal oxide, the expanded graphite and the metal oxide form a composite electrode, and a novel super capacitor electrode material with excellent performance is expected to be obtained.

Disclosure of the invention

The object of the present invention is to provide a process for the preparation of an expanded graphite/metal oxide composite material for the preparation of supercapacitors with a high energy density and power density.

The product of the invention comprises the following components in percentage by weight: 5 to 99t percent of expanded graphite and 1 to 95 percent of metal oxide, preferably 10 to 50 percent of expanded graphite and 50 to 90 percent of metal oxide; the metal oxide is one or at least two of oxides of transition metals of Ti, zr, V, nb, ta, cr, mo, W, mn, fe, co, ir, ni, pa or Ru.

The product of the invention is made by the following method:

(1) High energy ball milling process

Adding the expanded graphite and the nano powder of the transition metal oxide into a planetary high-energy ball mill according to the proportion of 5-99 t percent of the expanded graphite and 1-95 percent of the metal oxide by weight percent for ball milling and mixing, wherein the rotating speed is 100-250 r/min, and preferably 150-250 r/min; the ball powder ratio is 10: 1-30: 1, preferably 10: 1-15: 1; the ball milling time is 5 to 40 hours, preferably: and (3) obtaining the expanded graphite/metal oxide composite material after 10-20 hours.

(2) Sol impregnation method

Preparing raw materials according to the weight percentage of 5-99 t percent of expanded graphite and 1-95 percent of transition metal oxide;

(a) Uniformly dispersing the 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%, and preferably 10-30%;

(b) The expanded graphite is dipped into the stable dispersion liquid of the inorganic nano particles, placed for 10 to 24 hours at room temperature, and then dried for 4 to 20 hours, preferably 4 to 8 hours at the temperature of between 100 and 200 ℃, so as to obtain the expanded graphite/metal oxide composite material.

(3) Chemical deposition method

Adding expanded graphite into metal nitrate or other soluble salt solution with the concentration of 0.1-3 mol/L, wherein the weight ratio of the expanded graphite to the solution is 1: 5-20, fully stirring, performing ultrasonic dispersion for 1-20 hours, preferably for 5-10 hours, then dropwise adding sodium hydroxide, potassium hydroxide or sodium carbonate solution while stirring until the pH value of the solution is more than 10, stirring for 1-4 hours, filtering and washing until the pH value is neutral, drying at 100-200 ℃ for 2-10 hours, finally calcining at 300-800 ℃ for 1-4 hours, preferably at 300-500 ℃ for 1-4 hours under inert atmosphere, and thus obtaining the expanded graphite/metal oxide composite material.

The invention also has the technical characteristics that:

1. the expanded graphite obtained by the above processes (1), (2) and (3) has an expanded volume of 10 to 600mL/g, preferably 200 to 600mL/g, and a purity of > 99%;

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

3. the transition metal oxide in the above methods (1) and (2) is one or at least two oxides of transition metals Ti, zr, V, nb, ta, cr, mo, W, mn, fe, co, ir, ni, pa or Ru;

4. the nitrate or other soluble salt of a transition metal in the above method (3) is one or at least two of nitrates or other soluble salts of transition metals Ti, zr, V, nb, ta, cr, mo, W, mn, fe, co, ir, ni, pa or Ru.

The expanded graphite/metal oxide material is prepared into a polarized electrode according to the following steps, and electrochemical performance test is carried out:

fully and uniformly mixing expanded graphite/metal oxide (80 wt%) and conductive carbon black (10 wt%) in a mechanical oscillation mode, sequentially adding distilled water (5 wt%) and Polytetrafluoroethylene (PTFE) (5 wt%) emulsion, adding while mechanically stirring to ensure that the emulsion is uniform, adopting foamed metal nickel as a current collector, adopting metal nickel platinum as an electrode tab, and adopting a spot welding mode for connecting the tab and the current collector; mechanically coating the paste on a current collector which is cut and welded with a tab in advance, vacuum-drying the pasted pole piece at 110 ℃ for 10 hours, compacting the dried pole piece on an oil press, and trimming burrs on the edge to obtain an electrode (1 cm) ² ). A polypropylene separator was inserted between two identical electrodes and pressed with a clamp. 30% of KAfter the OH electrolyte was injected into the electrode, cyclic voltammetry measurements were carried out at a scan rate of 1mV/s using a platinum counter electrode and an SCE reference electrode under a constant current of 1mA at a voltage range of 0.0 to 0.8V. The unit capacitance can be calculated by dividing the current in cyclic voltammetry by the scan rate and the mass of the electrode active material. After the completion of charging, the circuit is opened for 1 second, and the internal resistance R is obtained from Δ V = RI from the current just before opening and the voltage drop Δ V.

According to the invention, the electrode material of the super capacitor is prepared by compounding the expanded graphite and the oxide particles, and the prepared super capacitor has high specific capacity and lower internal resistance. Meanwhile, the method uses the cheap and easily obtained expanded graphite as the raw material, has simple preparation process and low cost and has strong industrial application value.

(IV) detailed description of the invention

The invention will be further illustrated with reference to the following specific examples: the nanometal oxides in the following embodiments may be purchased commercially or otherwise as described in [ journal Park, et al ultra-large-scale synthesis of monodispersensonanocrysis, nature Materials,2004,3:891; guoliqin et al, preparation of nano nickel oxide and its applications, chemical engineers, 2006, 130 (7): 28], etc. by methods reported in the literature.

Example 1:

0.5g of expanded graphite (expanded volume 200 mL/g) and 9.5g of nano nickel oxide (average particle size 5 nm) were ball-milled for 40 hours in a planetary high-energy ball mill using steel balls and ball pots at a revolution of 100rpm and a ball-to-powder ratio of 10: 1. The electrode was taken out and dried at 100 ℃ to prepare a polarized electrode for electrochemical performance test, and the obtained results are shown in Table 1.

Example 2:

5g of expanded graphite (the expansion volume is 600 mL/g) and 5g of nano manganese oxide (the average particle size is 1000 nm) are subjected to ball milling for 5 hours in a planetary high-energy ball mill by using steel grinding balls and ball tanks at the rotation speed of 250rpm and the ball powder ratio of 30: 1. The electrode was taken out and dried at 100 ℃ to prepare a polarized electrode for electrochemical performance test, and the obtained results are shown in Table 1.

Example 3:

3g of expanded graphite (expansion volume 400 mL/g) and 7g of nano manganese oxide (average particle size 50 nm) are subjected to ball milling for 10 hours in a planetary high-energy ball mill by using steel grinding balls and ball tanks at the rotation speed of 250rpm and the ball powder ratio of 10: 1. The electrode was taken out and dried at 100 ℃ to prepare a polarized electrode for electrochemical performance test, and the obtained results are shown in Table 1.

Example 4:

using an ultrasonic disperser and cetyl trimethyl ammonium bromide as a surfactant, 1g of nano molybdenum oxide (average particle size of 100 nm) is uniformly dispersed into 100g of aqueous solution, then 9g of expanded graphite (expansion volume of 300 mL/g) is immersed into the dispersion, the dispersion is placed at room temperature for 10 hours and dried at 100 ℃ for 20 hours, and the dispersion is taken out to prepare a polarizing electrode for electrochemical performance test, and the test results are listed in table 1.

Example 5:

using an ultrasonic disperser and cetyl trimethyl ammonium bromide as a surfactant, 7g of nano ruthenium oxide (with an average particle size of 50 nm) is uniformly dispersed into 10g of aqueous solution, then 2g of expanded graphite (with an expanded volume of 400 mL/g) is immersed into the dispersion, the dispersion is placed at room temperature for 24 hours and then dried at 200 ℃ for 4 hours, and after being taken out, a polarizing electrode is prepared for electrochemical performance test, and the test results are listed in table 1.

Example 6:

5g of expanded graphite (expanded volume 400 mL/g) is added into 100mL of 0.1mol/L nickel nitrate solution, sufficiently stirred, ultrasonically dispersed for 1 hour, then stirred and dropwise added with 1mol/L sodium hydroxide solution until the pH is =10, stirred for 4 hours, filtered and washed until the pH value is neutral, dried at 100 ℃ for 2 hours, and calcined at 400 ℃ for 4 hours under an inert atmosphere. The obtained mixture was used to prepare a polarizable electrode for electrochemical performance test, and the results are shown in Table 1.

Example 7:

adding 4g of expanded graphite (the expansion volume is 400 mL/g) into 20mL of 1mol/L nickel nitrate solution, fully stirring, ultrasonically dispersing for 20 hours, then dropwise adding 0.1mol/L sodium carbonate solution under stirring until the pH value is =10, stirring for 1 hour after dropwise adding is finished, filtering and washing until the pH value is neutral, drying at 100 ℃ for 10 hours, and calcining at 800 ℃ for 1 hour under an inert atmosphere. The obtained mixture was formed into a polarizable electrode to be subjected to electrochemical performance tests, and the results thereof are shown in table 1.

Example 8:

adding 5g of expanded graphite (the expansion volume is 400 mL/g) into 50mL of a 3mol/L cobalt nitrate solution, fully stirring, ultrasonically dispersing for 10 hours, then dropwise adding 3mol/L potassium hydroxide solution under stirring until the pH value is =10, stirring for 1 hour after dropwise adding, filtering and washing until the pH value is neutral, drying for 5 hours at 100 ℃, and calcining for 1 hour at 400 ℃ under an inert atmosphere. The obtained mixture was used to prepare a polarizable electrode for electrochemical performance test, and the results are shown in Table 1.

TABLE 1 electrochemical test results for expanded graphite/oxide composites

Examples	Unit capacitor 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

1. A preparation method of an expanded graphite/metal oxide composite material is characterized by comprising the following steps: 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.

2. The method for producing an expanded graphite/metal oxide composite material according to claim 1, characterized in that: the weight ratio of the nano particles in the step (a) is 10-30%.

3. The method for preparing an expanded graphite/metal oxide composite material according to claim 2, wherein: the drying time of the drying at 100-200 ℃ in the step (b) is 4-8 hours.

4. The method for preparing an expanded graphite/metal oxide composite material according to claim 3, wherein: the expanded volume of the expanded graphite is 10 mL/g-600 mL/g, and the purity of the expanded graphite is more than 99%.

5. The method for producing an expanded graphite/metal oxide composite material according to claim 4, characterized in that: the grain diameter of the transition metal oxide is 5-1000 nm.

6. The method for producing an expanded graphite/metal oxide composite material according to claim 5, characterized in that: the transition metal oxide is one or at least two of oxides of Ti, zr, V, nb, ta, cr, mo, W, mn, fe, co, ir, ni, pa or Ru.