CN103426564B - Graphene electrodes active material and its preparation method and application and electrode material, electrode slice and electrochemical capacitor - Google Patents

Abstract

The invention discloses a method for preparing a graphene electrode active material. The method comprises the following steps: (1) dispersing graphite oxide powder in deionized water to obtain a dispersion; (2) dissolving the dispersion obtained in step (1) in After the hydrogen ion concentration is 0.01-16mol/L and the temperature is 0-100°C, it is placed for 5-240 minutes, and the solid-liquid separation is carried out to obtain the precipitate; (3) The precipitate obtained in step (2) is dried and ground Finally, powder A is obtained; (4) The powder A obtained in step (3) is heat-treated at 600-1200° C. for 1-60 seconds in an inert gas atmosphere. The invention also discloses the graphene electrode active material prepared by the above method, and also discloses the electrode material, the electrode sheet and the electrochemical capacitor. The surface of the graphene electrode active material of the invention has a large number of carbonyl groups and hydroxyl groups, and the electrochemical capacitor has higher specific capacitance, capacity retention rate and energy density.

Description

Graphene electrode active material and its preparation method and application as well as electrode material, electrode sheet and electrochemical capacitor

technical field

The present invention relates to a kind of preparation method of graphene electrode active material and the graphene electrode active material prepared by this method, and the application of this graphene electrode active material in preparing electrode material, electrode sheet or electrochemical capacitor, the present invention also It relates to an electrode material, an electrode sheet and an electrochemical capacitor containing the electrode active material.

Background technique

Electrochemical Capacitor (EC), also known as supercapacitor (Supercapacitor), as a new type of chemical power supply, has a long service life (105 cycles), high specific power (1500W/kg), and fast charging (can be several seconds ), good low temperature performance (minimum working temperature -50°C), good high current discharge performance, large energy storage, higher power density than batteries, higher energy density than traditional capacitors, not only can be used with batteries as electric Vehicles, etc. provide peak power, and can even provide power for electric tools or electric vehicles alone, so as to reduce the negative impact on ecology based on the combustion of fossil resources to provide energy. Moreover, it is light in weight, maintenance-free, low in pollution, cheap in price, and excellent in performance, and is known as a new type of green energy. Therefore, electrochemical capacitors are likely to develop into an efficient and practical energy storage device in the future, so they have very broad application prospects in the fields of transportation, energy, communications, power electronics, military industry and national defense, and industrial production.

The quality of electrode materials is the decisive factor for the performance of electrochemical capacitors, and people have been developing electrode materials with higher energy density and higher power density. In the prior art, electrode materials used for electrochemical capacitors can be divided into the following three categories: noble metal oxides, conductive polymers and carbon-based electrode materials. Among them, precious metal resources are limited and expensive; conductive polymers have poor cycle stability, which limits their application; carbon electrode materials mainly include: activated carbon powder, activated carbon fiber, carbon aerogel, carbon nanotubes, etc., but activated carbon powder Although porous carbon materials such as activated carbon fibers and carbon aerogels can obtain relatively high specific capacitance, their conductivity is low, and their low specific power limits their application as electrochemical capacitors. Although carbon nanotubes have high conductivity Superior, but its high contact resistance, low specific capacity, and high cost also limit its application. Graphene material, as a two-dimensional material that has received wide attention in recent years, has a large specific surface area, excellent electrical conductivity, low cost and simple manufacturing process, and is an excellent choice as an electrode material for electrochemical capacitors.

The current method for preparing graphene electrode active materials is usually: directly heat-treating graphite oxide powder at a temperature of 600-1200° C. for 3-30 minutes in an inert gas atmosphere. However, the surface of the graphene electrode active material obtained by the current method has fewer carbonyl groups and hydroxyl groups, the content of carbonyl groups is generally 0.5-1.5 mol%, and the content of hydroxyl groups is generally 3-10 mol%. The electrode material prepared from the graphene electrode active material is used in an electrochemical capacitor, and the specific capacitance, capacity retention, and energy density of the electrochemical capacitor are not high enough. In order to prepare a higher specific capacitance, capacity retention, and energy density For electrochemical capacitors, it is necessary to develop more excellent graphene electrode active materials.

Contents of the invention

The purpose of the present invention is to overcome the carbonyl group and the hydroxyl group on the surface of the graphene electrode active material that current method obtains less, the electrode material prepared thus is used in the electrochemical capacitor, the specific capacitance, capacity retention rate, energy of the electrochemical capacitor The defect with lower density provides a new preparation method of graphene electrode active material, and the graphene electrode active material obtained by the method, and the graphene electrode active material is used in the preparation of electrode material, electrode sheet or electrochemical capacitor and provide electrode materials, electrode sheets and electrochemical capacitors containing the electrode active material.

The inventors of the present invention discovered unexpectedly in the research that the graphite oxide powder is dispersed in deionized water to obtain a dispersion liquid, and the dispersion liquid is placed at a hydrogen ion concentration of 0.01-16mol/L and a temperature of 0-100°C for 5- After 240 minutes, the precipitate was obtained by solid-liquid separation, and the powder obtained after drying and grinding the precipitate was heat-treated at 600-1200°C for 1-60 seconds in an inert gas atmosphere, and the graphene electrode active material obtained was The surface has a large number of carbonyl groups and hydroxyl groups. The graphene electrode active material is prepared as an electrode material and used in an electrochemical capacitor, which can make the electrochemical capacitor have higher specific capacitance, capacity retention and energy density.

Therefore, in order to achieve the above object, on the one hand, the invention provides a kind of preparation method of graphene electrode active material, it is characterized in that, described method comprises the following steps:

(1) Disperse graphite oxide powder in deionized water to obtain a dispersion;

(2) Place the dispersion liquid obtained in step (1) under the condition of hydrogen ion concentration of 0.01-16mol/L and temperature of 0-100°C for 5-240 minutes, and then conduct solid-liquid separation to obtain a precipitate;

(3) Drying and grinding the precipitate obtained in step (2) to obtain powder A;

(4) Heat-treat the powder A obtained in step (3) at 600-1200° C. for 1-60 seconds in an inert gas atmosphere.

Preferably, the carbon to oxygen atomic ratio of the graphite oxide powder is 1.5-3.0.

In another aspect, the present invention provides a graphene electrode active material, which is characterized in that the graphene electrode active material is prepared by the above-mentioned method.

In a third aspect, the present invention provides an electrode material, which contains a binder and an electrode active material, wherein the electrode active material is the above-mentioned graphene electrode active material.

In a fourth aspect, the present invention provides an electrode sheet, which includes a current collector and an electrode material supported on the current collector, wherein the electrode material is the electrode material as described above.

In a fifth aspect, the present invention provides an electrochemical capacitor, which includes a casing, a diaphragm, an electrolyte, and an electrode sheet, wherein the electrode sheet is the electrode sheet as described above.

In a sixth aspect, the present invention provides the application of the above-mentioned graphene electrode active material in the preparation of electrode materials, electrode sheets or electrochemical capacitors.

The surface of the graphene electrode active material prepared by the method of the present invention has a large amount of carbonyl groups and hydroxyl groups, the content of carbonyl groups is 2-10 mole %, and the content of hydroxyl groups is 8-30 mole %, which is made of the graphene electrode active material of the present invention Electrode materials are used in electrochemical capacitors, which can make electrochemical capacitors have higher specific capacitance, capacity retention and energy density. The method of the invention is simple and low in cost, and can be widely used in industrial production.

Other features and advantages of the present invention will be described in detail in the following detailed description.

Description of drawings

Fig. 1 is the cyclic voltammetry curve of the graphene electrode active material prepared in embodiment 1.

Fig. 2 is the cyclic voltammetry curve of the graphene electrode active material prepared in Comparative Example 1.

detailed description

Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

On the one hand, the invention provides a kind of preparation method of graphene electrode active material, and the method comprises the following steps:

(1) Disperse graphite oxide powder in deionized water to obtain a dispersion;

(2) Place the dispersion liquid obtained in step (1) under the condition of hydrogen ion concentration of 0.01-16mol/L and temperature of 0-100°C for 5-240 minutes, and then conduct solid-liquid separation to obtain a precipitate;

(3) Drying and grinding the precipitate obtained in step (2) to obtain powder A;

(4) Heat-treat the powder A obtained in step (3) at 600-1200° C. for 1-60 seconds in an inert gas atmosphere.

According to the inventive method, although adopting above-mentioned method can realize the object of the present invention, even if the surface of the prepared graphene electrode active material has a large amount of carbonyl and hydroxyl, the content of carbonyl is 2-10 mol%, and the content of hydroxyl is 8 -30 mol%, using the graphene electrode active material to make electrode materials for electrochemical capacitors, so that the electrochemical capacitors have higher specific capacitance, capacity retention and energy density. But preferably, the carbon-to-oxygen atomic ratio of graphite oxide powder is 1.5-3.0, more preferably 1.7-2.5, and the prepared graphene electrode active material is made into electrode material and used in electrochemical capacitors, which can make electrochemical capacitors have Higher specific capacitance, capacity retention and energy density.

In the present invention, graphite oxide powder can be prepared by various methods commonly used in the art, preferably using the Hummers method recorded in the document J.Am.Chem.Soc.1958,80,1339. to prepare graphite oxide, then dry and grind, That is, graphite oxide powder is obtained. In order to make the carbon-oxygen atomic ratio of the graphite oxide powder be 1.5-3.0, more preferably 1.7-2.5, the weight ratio of graphite and potassium permanganate in the Hummers method is preferably 1: 3-5, more preferably 1: 3-4 .

In the present invention, in order to make the graphite oxide powder in the dispersion liquid more fully contact with hydrogen ions, in step (1), the average particle size of the graphite oxide powder is preferably 5-600 microns, more preferably 10-500 microns.

In step (1) of the present invention, the concentration of graphite oxide powder in the dispersion liquid is preferably 0.05-0.25% by weight; more preferably 0.09-0.2% by weight.

In the present invention, the method of dispersing the graphite oxide powder in deionized water can adopt various methods known in the art. For example, after adding graphite oxide powder into deionized water, ultrasonic method is used to disperse. The conditions of sonication can adopt various conditions known in the art, for example, sonicate at 20-80° C. for 10-100 minutes.

In step (2) of the present invention, the hydrogen ion concentration is preferably 0.1-16 mol/L, the temperature is preferably 5-80°C, and the storage time is preferably 10-120 minutes.

In the present invention, the concentration of hydrogen ions can be adjusted by using an acid, and the acid can be various acids known in the art. Preferably, the acid is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, hydrobromic acid, hydroiodic acid and acetic acid, and more preferably, the acid is hydrochloric acid or sulfuric acid.

In the present invention, in step (3), various methods known in the art can be used for drying, for example, the precipitate obtained in step (2) is vacuum-dried at 30-120° C. for 2-24 hours. Various methods known in the art can be used for grinding, such as manual grinding, pulverizer grinding, ball milling, vibration milling and the like. The degree of grinding is represented by the average particle size of the powder A obtained after grinding, and the average particle size of the powder A is preferably 0.05-300 microns, more preferably 5-150 microns.

In step (4) of the present invention, the heat treatment temperature is preferably 700-1150°C, more preferably 900-1050°C; the heat treatment time is preferably 5-60 seconds, more preferably 5-30 seconds, and even more preferably 10-30 seconds Second. The heat treatment is preferably carried out in a tube furnace. For the inert gas atmosphere, it is preferably one or more of nitrogen, argon, and helium.

In the second aspect, the present invention also provides a graphene electrode active material, which is prepared by the above-mentioned method.

Preferably, the carbonyl content in the graphene electrode active material is 3-9 mol%, and the hydroxyl content is 12-25 mol%.

In a third aspect, the present invention provides an electrode material, which contains a binder and an electrode active material, and the electrode active material is the above-mentioned graphene electrode active material.

In the electrode material, the content of the graphene electrode active material can be the conventional content in this field. Preferably, based on the total weight of the electrode material, the content of the binder is 0.3-20% by weight, and the content of the graphene electrode active material is 80-99.7% by weight; more preferably, based on the total weight of the electrode material As a benchmark, the content of the binder is 1-15% by weight, and the content of the graphene electrode active material is 85-99% by weight. The binder can be various commonly used binders in the field, for example, it can be one or more of polytetrafluoroethylene, polyvinylidene fluoride, butyl rubber and polyacrylate.

The electrode material of the present invention may also include a conductive agent, which may be various conductive agents commonly used in the art, such as one or more of acetylene black, carbon black, graphite powder and carbon fiber. The content of the conductive agent can be a conventional content, preferably, based on the total weight of the electrode material, the content of the binder is 1-15% by weight, the content of the graphene electrode active material is 80-95% by weight, and the content of the conductive agent The content is 0.1-10% by weight.

In a fourth aspect, the present invention provides an electrode sheet, which includes a current collector and an electrode material supported on the current collector, where the electrode material is the electrode material as described above.

The current collector may be a commonly used current collector, such as metal sheet, metal mesh, metal foil and foamed metal.

The electrode sheet can be prepared by various methods commonly used in the field, such as preparing the electrode material into an electrode slurry with a solvent, then drying the prepared electrode slurry, pressing it into a thin sheet, and then pressing it on the current collector to obtain the electrode sheet. The drying temperature may be 80-150° C., and the drying time may be 2-10 hours.

The solvent used to prepare the electrode slurry can be various solvents in the prior art, such as water, N-methylpyrrolidone (NMP), dimethylformamide (DMF), diethylformamide (DEF), One or more of dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), water and alcohols. The weight ratio of the electrode material to the solvent is 1:0.1-100.

In a fifth aspect, the present invention provides an electrochemical capacitor, which includes a casing, a diaphragm, an electrolyte, and an electrode sheet, where the electrode sheet is the electrode sheet as described above.

The housing can be metal or plastic.

The diaphragm can be made of polyethylene film, polypropylene film, cellulose film or their modified polymers.

The electrolyte solution can choose the following three systems:

1. Organic system: The electrolyte solvent is selected from one or more of ethylene carbonate, ethylene carbonate, propylene carbonate and acetonitrile, and the salt used in the electrolyte is selected from tetraethyl tetrafluoroborate quaternary ammonium salt, tetraethyl One or more of quaternary phosphorous tetrafluoroborate, quaternary phosphorous tetra-n-propyl tetrafluoroborate, quaternary ammonium tetraethyl hexafluorophosphate, lithium hexafluorophosphate, lithium perchlorate and lithium tetrafluoroborate. The electrolyte concentration can be 0.1-5 mol/liter.

2. Various room temperature ionic liquids: any combination of any two or more of the following anions and cations. Most of the cations are the following types: quaternary ammonium cation, quaternary phosphorus cation, pyridinium cation, imidazolium cation, sulfonium cation, the most common anions are BF ₄ ^- , PF ₆ ^- , and NO ₃ ^- , SbF ₆ ^- , CIO ₄ ^- , CF ₃ SO ₃ ^- , C ₃ F ₇ COO ^- , C ₄ F ₉ SO ₃ ^- , F ₃ COO ^- , etc.

3. Solid electrolyte (no need for diaphragm and shell under this condition): the matrix is selected from one or more of polyvinylbenzenesulfonic acid, polyvinylpyrrolidone and polyvinyl alcohol, and the salt used is selected from tetraethyltetrafluoroboric acid Quaternary ammonium salt, tetraethyl tetrafluoroborate quaternary phosphorus salt, tetra-n-propyl tetrafluoroborate quaternary phosphorus salt, tetraethyl hexafluorophosphate quaternary phosphorus salt, lithium hexafluorophosphate, lithium tetrafluoroborate and tetramethyl One or more of the perchlorate salts of ammonium. The solid electrolyte concentration may be 0.1-2 mol/liter.

In the present invention, the method of constituting the electrochemical capacitor by the shell, the diaphragm, the electrolyte and the electrode sheet is well known to those skilled in the art, and will not be repeated here.

In the sixth aspect, the present invention also provides the application of the above-mentioned graphene electrode active material in the preparation of electrode materials, electrode sheets or electrochemical capacitors.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way if there is no contradiction. The combination method will not be described separately.

In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

Example

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

In the following examples and comparative examples:

Determination method of carbon-oxygen atomic ratio of graphite oxide powder: XPS (X-ray photoelectron spectroscopy).

Measuring method of powder particle size: scanning electron microscope (SEM).

A scanning electron microscope (Hitachi S-4800, Japan) was used to observe the surface morphology of the graphene electrode active material.

The specific surface area and average pore diameter of the graphene electrode active material were measured using a specific surface area and porosity adsorption instrument (Mike Instruments, USA, model ASAP2020).

X-ray photoelectron spectroscopy (Shimadzu Instrument Co., Ltd., Axis-Ultra) was used to measure the surface functional group content of graphene electrode active materials.

Using CT2001A, LAND battery test system (Wuhan Jinnuo Electronics Co., Ltd.), under the condition of constant current charge and discharge, measure the specific capacitance, capacity retention rate, energy density and power density of electrochemical capacitors; use CHI660d electrochemical workstation ( Shanghai Chenhua Instrument Co., Ltd.) obtained the cyclic voltammetry curve of the electrochemical capacitor.

Example 1

This embodiment is used to illustrate the preparation method of the graphene electrode active material provided by the present invention and the prepared graphene electrode active material, electrode material, electrode sheet and electrochemical capacitor.

(1) Weigh 10 grams of natural flake graphite (purchased from Alfa Aisha Company, the same below, with an average particle size of 0.89 mm), and 5 grams of sodium nitrate, and add to 230 ml of concentrated sulfuric acid (concentration 98% by weight) under an ice bath ), followed by adding 30 g of potassium permanganate, removing the ice bath, and raising the temperature to 35° C., and kept stirring during this process. When the reactant turns pink, add the reactant to 1.5 liters of deionized water, slowly add hydrogen peroxide with a concentration of 3% by weight until no bubbles are generated, filter to obtain a solid, and then use 0.1mol/L dilute hydrochloric acid to remove Rinse the solid with deionized water until there is no chloride ion and sulfate ion, dry it in vacuum at 40° C., and grind to obtain graphite oxide powder until the average particle size of the graphite oxide powder is 120 microns. The carbon-to-oxygen atomic ratio of the graphite oxide powder was measured to be 1.94.

(2) Disperse 1 gram of the above-mentioned graphite oxide powder in 800 grams of deionized water, and ultrasonicate at 50 °C for 1 hour to obtain a dispersion liquid, and place the dispersion liquid at a hydrogen ion concentration of 1 mol/L and a temperature of 25 °C for 90 Minutes later, the precipitate was obtained by suction filtration. After the precipitate was vacuum-dried at 40°C for 24 hours, it was manually ground to obtain powder A, and the average particle size of powder A was ground to 80 microns. Put the powder A into a quartz semi-sealed tube under the protection of argon, put it into a tube furnace at 900° C., take it out after heat treatment for 30 seconds, and obtain a graphene electrode active material.

It is observed that the surface morphology of the graphene electrode active material is a lamellar microstructure. The specific surface area, average pore size, surface carbonyl and hydroxyl content of the graphene electrode active material were measured, and the results are shown in Table 1.

(3) Mix the above-mentioned graphene electrode active material with the conductive agent acetylene black and the binder polytetrafluoroethylene (the number average molecular weight is about 2,000,000) in a weight ratio of 80:10:10 to obtain the electrode material, and add distilled water dropwise The above mixture was stirred until it was in the form of a slurry, dried at 100°C for 8 hours, pressed into thin sheets, and then pressed onto a foamed nickel collector plate to obtain an electrode sheet. Select 1-butyl-3-methylimidazolium tetrafluoroborate as the electrolyte, polypropylene (number average molecular weight is about 59000) microporous membrane as the separator, and CR2032 battery shell (purchased from Shenzhen Kejing Zhida Technology Co., Ltd. , the same below) is the shell, and the obtained electrode sheet constitutes an electrochemical capacitor.

The specific capacitance, energy density and power density of the electrochemical capacitor were measured under the constant current density of 0.1A/g and 1A/g in the working voltage window of 0~4V; After 5000 discharges, the capacity retention of the electrochemical capacitor was measured. The results are shown in Table 2. Figure 1 is the cyclic voltammetry curve of the electrochemical capacitor.

Comparative example 1

This comparative example is used to illustrate the preparation method of the currently used graphene electrode active material and the prepared graphene electrode active material and electrochemical capacitor.

(1) Graphite oxide powder was prepared according to the method of step (1) in Example 1, except that the graphite oxide powder was ground to an average particle size of 80 microns. The carbon-to-oxygen atomic ratio of the graphite oxide powder was measured to be 1.94.

(2) Put 1 g of the above-mentioned graphite oxide powder into a semi-sealed quartz tube under the protection of argon, put it into a tube furnace at 900° C., take it out after heat treatment for 200 seconds, and obtain a graphene electrode active material.

It is observed that the surface morphology of the graphene electrode active material is a lamellar microstructure. The specific surface area, average pore size, surface carbonyl and hydroxyl content of the graphene electrode active material were measured, and the results are shown in Table 1.

(3) According to the method of step (3) in Example 1, an electrochemical capacitor is formed, and the operating voltage window is 0~4V, and the electrochemical capacitor is measured at a constant current density of 0.1A/g and 1A/g, respectively. Specific capacitance, energy density and power density; after charging and discharging 5000 times with a constant current density of 0.5A/g, the capacity retention rate of the electrochemical capacitor was measured. The results are shown in Table 2. Figure 2 is the cyclic voltammetry curve of the electrochemical capacitor.

Example 2

This embodiment is used to illustrate the preparation method of the graphene electrode active material provided by the present invention and the prepared graphene electrode active material, electrode material, electrode sheet and electrochemical capacitor.

(1) Weigh 10 grams of natural flake graphite (325 mesh), and 5 grams of sodium nitrate, under ice bath, join in 230 ml of concentrated sulfuric acid (concentration 98% by weight), then add 35 grams of potassium permanganate, remove In an ice bath, the temperature was raised to 35°C, and the mixture was kept stirring during the process. When the reactant turns pink, add the reactant to 1.5 liters of deionized water, slowly add hydrogen peroxide with a concentration of 3% by weight until no bubbles are generated, filter to obtain a solid, and then use 0.1mol/L dilute hydrochloric acid to remove Rinse the solid with deionized water until there is no chloride ion and sulfate ion, dry it in vacuum at 40° C., and grind to obtain graphite oxide powder, which is ground until the average particle size of the graphite oxide powder is 50 microns. The carbon-to-oxygen atomic ratio of the graphite oxide powder was measured to be 2.15.

(2) Disperse 1 gram of the above-mentioned graphite oxide powder in 1100 grams of deionized water, and ultrasonicate at 20°C for 100 minutes to obtain a dispersion liquid, and place the dispersion liquid at a hydrogen ion concentration of 0.1mol/L and a temperature of 5°C After 120 minutes, the precipitate was obtained by suction filtration. The precipitate was vacuum-dried at 80° C. for 10 hours, and manually ground to obtain powder A. The average particle diameter of powder A was ground to 43 microns. Put the powder A into a quartz semi-sealed tube under the protection of nitrogen, put it into a tube furnace at 950°C, take it out after heat treatment for 25 seconds, and obtain a graphene electrode active material.

It is observed that the surface morphology of the graphene electrode active material is a lamellar microstructure. The specific surface area, average pore size, surface carbonyl and hydroxyl content of the graphene electrode active material were measured, and the results are shown in Table 1.

(3) Mix the above-mentioned graphene electrode active material with the conductive agent carbon black and the binder polyvinylidene fluoride (the number average molecular weight is about 71000) in a mass ratio of 90:5:5 to obtain the electrode material, and add distilled water dropwise The above mixture was stirred until it was in the form of a slurry, dried at 80°C for 10 hours, pressed into thin sheets, and then pressed onto a foamed nickel collector plate to obtain an electrode sheet. Lithium perchlorate propylene carbonate solution (1mol/L) is selected as the electrolyte, polyethylene (number average molecular weight is about 24,000) microporous membrane is used as the diaphragm, CR2032 battery shell is used as the shell, and the obtained electrode sheet constitutes an electrochemical capacitor. .

The specific capacitance, energy density and power density of the electrochemical capacitor were measured under the constant current density of 0.1A/g and 1A/g in the working voltage window of 0~4V; After 5000 discharges, the capacity retention of the electrochemical capacitor was measured. The results are shown in Table 2. The cyclic voltammetry curve is similar to that of Example 1 (not shown in the drawings).

Example 3

This embodiment is used to illustrate the preparation method of the graphene electrode active material provided by the present invention and the prepared graphene electrode active material, electrode material, electrode sheet and electrochemical capacitor.

(1) Weigh 10 grams of natural flake graphite (average particle size 0.89 mm), and 5 grams of sodium nitrate, add 230 ml of concentrated sulfuric acid (concentration 98% by weight) under ice bath, and then add 40 grams of potassium permanganate , remove the ice bath, heat up to 35°C, and keep stirring during this process. When the reactant turns pink, add the reactant to 1.5 liters of deionized water, slowly add hydrogen peroxide with a concentration of 3% by weight until no bubbles are generated, filter to obtain a solid, and then use 0.1mol/L dilute hydrochloric acid to remove Rinse the solid with deionized water until there is no chloride ion and sulfate ion. After vacuum drying at 40° C., grind to obtain graphite oxide powder, and grind until the average particle size of the graphite oxide powder is 500 microns. The carbon to oxygen atomic ratio of the graphite oxide powder was measured to be 2.33.

(2) Disperse 1 gram of the above-mentioned graphite oxide powder in 500 grams of deionized water, ultrasonicate at 50°C for 1 hour to obtain a dispersion liquid, and place the dispersion liquid at a hydrogen ion concentration of 10mol/L and a temperature of 70°C for 20 Minutes later, the precipitate was obtained by suction filtration. After the precipitate was vacuum-dried at 100° C. for 6 hours, powder A was obtained by manual grinding until the average particle size of powder A was 150 microns. Put the powder A into a quartz semi-sealed tube under the protection of argon, put it into a tube furnace at 1000° C., take it out after heat treatment for 20 seconds, and obtain a graphene electrode active material.

It is observed that the surface morphology of the graphene electrode active material is a lamellar microstructure. The specific surface area, average pore size, surface carbonyl and hydroxyl content of the graphene electrode active material were measured, and the results are shown in Table 1.

(3) Mix the above-mentioned graphene electrode active material with the binder polytetrafluoroethylene (the number-average molecular weight is about 2,000,000) at a mass ratio of 90:10 to obtain an electrode material, and stir the above-mentioned mixture in the state of adding distilled water dropwise to a slurry form, dried at 120° C. for 5 hours, pressed into thin sheets, and then pressed onto foamed nickel current collectors to obtain electrode sheets. Choose lithium hexafluorophosphate as the solute, a mixture of ethylene carbonate and ethylene carbonate with a volume ratio of 1:1 as the solvent, a solution with a concentration of 1mol/L as the electrolyte, and a cellulose (number-average molecular weight of about 48,000) microporous membrane as the diaphragm. The CR2032 battery shell is the shell, and the obtained electrode sheet constitutes an electrochemical capacitor.

The specific capacitance, energy density and power density of the electrochemical capacitor were measured under the constant current density of 0.1A/g and 1A/g in the working voltage window of 0~4V; After 5000 discharges, the capacity retention of the electrochemical capacitor was measured. The results are shown in Table 2. The cyclic voltammetry curve is similar to that of Example 1 (not shown in the drawings).

Example 4

This embodiment is used to illustrate the preparation method of the graphene electrode active material provided by the present invention and the prepared graphene electrode active material, electrode material, electrode sheet and electrochemical capacitor.

(1) Weigh 10 grams of natural flake graphite (200 mesh), and 5 grams of sodium nitrate, under ice bath, join in 230 ml concentrated sulfuric acid (concentration 98% by weight), then add 30 grams of potassium permanganate, remove In an ice bath, the temperature was raised to 35°C, and the mixture was kept stirring during the process. When the reactant turns pink, add the reactant to 1.5 liters of deionized water, slowly add hydrogen peroxide with a concentration of 3% by weight until no bubbles are generated, filter to obtain a solid, and then use 0.1mol/L dilute hydrochloric acid to remove Rinse the solid with deionized water until there is no chloride ion and sulfate ion. After vacuum drying at 40° C., grind to obtain graphite oxide powder, and grind until the average particle size of the graphite oxide powder is 10 microns. The carbon-to-oxygen atomic ratio of the graphite oxide powder was measured to be 1.77.

(2) Disperse 1 gram of the above-mentioned graphite oxide powder in 600 grams of deionized water, ultrasonicate at 80°C for 10 minutes to obtain a dispersion liquid, and place the dispersion liquid at a hydrogen ion concentration of 1mol/L and a temperature of 80°C for 10 Minutes later, the precipitate was obtained by suction filtration. After the precipitate was vacuum-dried at 30°C for 24 hours, it was manually ground to obtain powder A, and the average particle diameter of powder A was ground to 5 microns. Put the powder A into a quartz semi-sealed tube under the protection of nitrogen and put it into a tube furnace at 1050° C., take it out after heat treatment for 10 seconds, and obtain a graphene electrode active material.

It is observed that the surface morphology of the graphene electrode active material is a lamellar microstructure. The specific surface area, average pore size, surface carbonyl and hydroxyl content of the graphene electrode active material were measured, and the results are shown in Table 1.

(3) The above-mentioned graphene electrode active material is mixed with the conductive agent graphite powder and the binder butyl rubber (the number average molecular weight is about 16000) according to the mass ratio of 95:1:4 to obtain the electrode material. After adding distilled water dropwise The above mixture was stirred until it was in the form of a slurry, dried at 150°C for 2 hours, pressed into thin sheets, and then pressed onto a foamed nickel collector plate to obtain an electrode sheet. Select a solid electrolyte (polyethylene benzene sulfonic acid (number average molecular weight is about 7000) containing 10% by mass ratio of tetramethylammonium perchlorate) as the electrolyte, without a diaphragm and a shell, and form an electrode with the obtained electrode sheet. chemical capacitor.

The specific capacitance, energy density and power density of the electrochemical capacitor were measured at the constant current density of 0.1A/g and 1A/g in the working voltage window of 0~4.5V; at the constant current density of 0.5A/g After charging and discharging 5000 times, the capacity retention of the electrochemical capacitor was measured. The results are shown in Table 2. The cyclic voltammetry curve is similar to that of Example 1 (not shown in the drawings).

Example 5

This embodiment is used to illustrate the preparation method of the graphene electrode active material provided by the present invention and the prepared graphene electrode active material, electrode material, electrode sheet and electrochemical capacitor.

(1) Weigh 10 grams of natural flake graphite (32 mesh), and 5 grams of sodium nitrate, under ice bath, join in 230 ml of concentrated sulfuric acid (concentration 98% by weight), then add 30 grams of potassium permanganate, remove In an ice bath, the temperature was raised to 35°C, and the mixture was kept stirring during the process. When the reactant turns pink, add the reactant to 1.5 liters of deionized water, slowly add hydrogen peroxide with a concentration of 3% by weight until no bubbles are generated, filter to obtain a solid, and then use 0.1mol/L dilute hydrochloric acid to remove Rinse the solid with deionized water until there is no chloride ion and sulfate ion. After vacuum drying at 40° C., grind to obtain graphite oxide powder, and grind until the average particle size of the graphite oxide powder is 320 microns. The carbon-to-oxygen atomic ratio of the graphite oxide powder was measured to be 1.7.

(2) Disperse 1 gram of the above-mentioned graphite oxide powder in 700 grams of deionized water, and ultrasonicate at 20°C for 100 minutes to obtain a dispersion liquid. Place the dispersion liquid at a hydrogen ion concentration of 16mol/L and a temperature of 5°C for 120 Minutes later, the precipitate was obtained by suction filtration. After the precipitate was vacuum-dried at 120°C for 2 hours, it was manually ground to obtain powder A, and the average particle size of powder A was ground to 100 microns. Put the powder A into a quartz semi-sealed tube under the protection of helium, put it into a tube furnace at 1050° C., take it out after heat treatment for 10 seconds, and obtain a graphene electrode active material.

It is observed that the surface morphology of the graphene electrode active material is a lamellar microstructure. The specific surface area, average pore size, surface carbonyl and hydroxyl content of the graphene electrode active material were measured, and the results are shown in Table 1.

(3) Mix the above-mentioned graphene electrode active material with the binder polytetrafluoroethylene in a mass ratio of 90:10 to obtain an electrode material, and stir the above-mentioned mixture to a slurry state under the state of adding distilled water dropwise, and heat it at 120°C After drying for 5 hours, it was pressed into a thin sheet and then pressed on a foamed nickel current collector to obtain an electrode sheet. The acetonitrile solution of tetraethylhexafluorophosphate quaternary ammonium salt is selected as the electrolyte, the cellulose (number average molecular weight is about 48000) microporous membrane is used as the separator, the CR2032 battery shell is used as the outer shell, and the obtained electrode sheet constitutes an electrochemical capacitor.

In the working voltage window of 0-2.7V, the specific capacitance, energy density and power density of the electrochemical capacitor were measured at a constant current density of 0.1A/g and 1A/g respectively; at a constant current density of 0.5A/g After charging and discharging 5000 times, the capacity retention of the electrochemical capacitor was measured. The results are shown in Table 2. The cyclic voltammetry curve is similar to that of Example 1 (not shown in the drawings).

Example 6

Prepare graphene electrode active material, electrode material, electrode sheet and electrochemical capacitor according to the method for embodiment 1, difference is, the consumption of potassium permanganate is 50 grams in the step (1), measure the carbon-oxygen atomic ratio of graphite oxide powder was 2.93.

It is observed that the surface morphology of the graphene electrode active material is a lamellar microstructure. The specific surface area, average pore size, surface carbonyl and hydroxyl content of the graphene electrode active material were measured, and the results are shown in Table 1.

When the working voltage window is 0-4V, measure the specific capacitance, energy density and power density of the electrochemical capacitor under the constant current density of 0.1A/g and 1A/g respectively; After 5000 discharges, the capacity retention of the electrochemical capacitor was measured. The results are shown in Table 2.

Example 7

The graphene electrode active material, electrode material, electrode sheet and electrochemical capacitor were prepared according to the method of Example 1, except that in step (2), the concentration of hydrogen ions was 0.05 mol/L.

It is observed that the surface morphology of the graphene electrode active material is a lamellar microstructure. The specific surface area, average pore size, surface carbonyl and hydroxyl content of the graphene electrode active material were measured, and the results are shown in Table 1.

When the working voltage window is 0-4V, measure the specific capacitance, energy density and power density of the electrochemical capacitor under the constant current density of 0.1A/g and 1A/g respectively; After 5000 discharges, the capacity retention of the electrochemical capacitor was measured. The results are shown in Table 2.

Example 8

The graphene electrode active material, electrode material, electrode sheet, and electrochemical capacitor were prepared according to the method in Example 1, except that in step (2), the heat treatment time was 60 seconds.

It is observed that the surface morphology of the graphene electrode active material is a lamellar microstructure. The specific surface area, average pore size, surface carbonyl and hydroxyl content of the graphene electrode active material were measured, and the results are shown in Table 1.

When the working voltage window is 0-4V, measure the specific capacitance, energy density and power density of the electrochemical capacitor under the constant current density of 0.1A/g and 1A/g respectively; After 5000 discharges, the capacity retention of the electrochemical capacitor was measured. The results are shown in Table 2.

Table 1

Specific surface area (m ² /g) Average pore size (nm) Carbonyl content (mol%) Hydroxyl content (mol%) Example 1 398 2.6 7.57 15.16 Comparative example 1 327 1.9 1.97 7.6 Example 2 412 2.8 8.66 19.23 Example 3 382 2.7 7.85 16.22 Example 4 418 2.4 5.13 12.98 Example 5 376 2.6 3.22 12.51 Example 6 457 3.1 9.9 23.26 Example 7 305 2.1 7.21 14.98 Example 8 418 2.9 2.75 10.38

Table 2

In table 1, comparing Example 1 with Comparative Example 1, it can be seen that the specific surface area of the graphene electrode active material prepared by the inventive method is larger, the average pore size is also larger, and the surface carbonyl and hydroxyl content are far greater than existing Graphene electrode active material prepared by technical method. In Table 2, comparing Example 1 with Comparative Example 1, it can be seen that the specific capacitance, energy density and capacity retention of the electrochemical capacitor provided by the present invention are all higher than those of the prior art electrochemical capacitor. It can also be seen from the comparison of Fig. 1 and Fig. 2 that the cyclic voltammetry curve of Fig. 1 is close to a rectangle and the enclosed area is much larger than that of Fig. 2, which also shows that the electrochemical capacitor provided by the present invention has higher energy density and good power characteristics .

Comparing Example 1 with Example 6, it can be seen that the weight ratio of graphite and potassium permanganate is more conducive to the specific capacitance, energy density and capacity retention of electrochemical capacitors in the scope of 1: 3-4. Improve; Embodiment 1 is compared with embodiment 7 and can find out, the dispersion liquid of graphite oxide powder is placed under the condition that hydrogen ion concentration is 0.1-16mol/L, is more conducive to the specific capacitance, energy of electrochemical capacitor The improvement of density and capacity retention rate; Comparing embodiment 1 with embodiment 8 as can be seen, the heat treatment time is 5-30 seconds, is more conducive to the retention of the carbonyl and hydroxyl on the surface of the graphene electrode active material made, more It is beneficial to the improvement of the specific capacitance and energy density of the electrochemical capacitor.

The surface of the graphene electrode active material prepared by the method of the present invention has a large amount of carbonyl groups and hydroxyl groups, the content of carbonyl groups is 2-10 mole %, and the content of hydroxyl groups is 8-30 mole %, which is made of the graphene electrode active material of the present invention Electrode materials are used in electrochemical capacitors, which can make electrochemical capacitors have higher specific capacitance, capacity retention and energy density. The method of the invention is simple and low in cost, and can be widely used in industrial production.

Claims (16)

1. a preparation method for Graphene electrodes active material, is characterized in that, said method comprising the steps of:

(1) graphite oxide powder dispersion is obtained dispersion liquid in deionized water;

(2) dispersion liquid step (1) obtained is 0.01-16mol/L in hydrogen ion concentration, after temperature places 5-240 minute under being the condition of 0-100 DEG C, carries out Separation of Solid and Liquid and be precipitated thing;

(3) powders A is obtained after the sediment that step (2) obtains being carried out drying, grinding;

(4) by the powders A that step (3) obtains, under atmosphere of inert gases, heat treatment 1-60 second at 600-1200 DEG C.

2. method according to claim 1, wherein, in step (1), the carbon oxygen atom of described graphite oxide powder is than being 1.5-3.0.

3. method according to claim 2, wherein, in step (1), the average grain diameter of graphite oxide powder is 5-600 micron.

4. method according to claim 3, wherein, in step (1), the average grain diameter of graphite oxide powder is 10-500 micron.

5., according to the method in claim 1-4 described in any one, wherein, in step (1), in dispersion liquid, the concentration of graphite oxide powder is 0.05-0.25 % by weight.

6. method according to claim 5, wherein, in step (1), in dispersion liquid, the concentration of graphite oxide powder is 0.09-0.2 % by weight.

7. method according to claim 1, wherein, in step (2), hydrogen ion concentration is 0.1-16mol/L, and temperature is 5-80 DEG C, and standing time is 10-120 minute.

8. method according to claim 1, wherein, in step (3), the average grain diameter of described powders A is 0.05-300 micron.

9. method according to claim 8, wherein, in step (3), the average grain diameter of described powders A is 5-150 micron.

10. method according to claim 1, wherein, in step (4), described heat treated temperature is 700-1150 DEG C, and the time is 5-30 second.

11. 1 kinds of Graphene electrodes active materials, is characterized in that, described Graphene electrodes active material is obtained by the method in claim 1-10 described in any one.

12. 1 kinds of electrode materials, described electrode material contains binding agent and electrode active material, it is characterized in that, described electrode active material is Graphene electrodes active material according to claim 11.

13. electrode materials according to claim 12, wherein, with the total weight of described electrode material for benchmark, the content of described binding agent is 0.3-20 % by weight, and the content of described Graphene electrodes active material is 80-99.7 % by weight.

14. 1 kinds of electrode slices, described electrode slice comprises collector and the electrode material of load on described collector, it is characterized in that, described electrode material is the electrode material described in claim 12 or 13.

15. 1 kinds of electrochemical capacitors, described electrochemical capacitor comprises shell, barrier film, electrolyte and electrode slice, it is characterized in that, described electrode slice is electrode slice according to claim 14.

16. Graphene electrodes active materials according to claim 11 are preparing the application in electrode material, electrode slice or electrochemical capacitor.