CN108962617B - Preparation method and application of self-assembled cobaltosic oxide hierarchical microsphere - Google Patents

Abstract

The invention discloses a preparation method and application of self-assembled tricobalt tetroxide graded microspheres. The preparation method is as follows: dispersing cobalt salt and polyvinyl alcohol in a mixed solution of ethylene glycol and deionized water, and using a hydrothermal method to obtain hydroxide The cobalt precursor is then subjected to high temperature annealing treatment to finally obtain cobalt tetroxide microspheres with a hierarchical structure formed by self-assembly of two-dimensional nanosheets; the obtained cobalt tetroxide graded microspheres are specifically used in supercapacitor electrode materials, and the specific capacitance retention rate is more than 70% . The invention utilizes the pyrolysis and gasification properties of polyvinyl alcohol to generate a large number of hollow micropores in the cobalt tetroxide structure, improve its porosity and specific surface area, and increase active sites, and the prepared cobalt tetroxide microspheres have both micro-nano size effect and classification It can effectively avoid the agglomeration problem caused by too small size and improve its electrochemical performance.

Description

Preparation method and application of self-assembled tricobalt tetroxide graded microspheres

technical field

The invention belongs to the technical field of supercapacitor electrode materials, and in particular relates to a preparation method and application of self-assembled tricobalt tetroxide graded microspheres.

Background technique

Supercapacitors, also known as electrochemical capacitors, are secondary energy storage devices that can directly store charges. Compared with traditional electrostatic capacitors and secondary batteries, they have higher power density, longer cycles, shorter charging times, and higher energy efficiency. It has higher efficiency and has broad application prospects in the mobile electronics industry, new energy energy storage systems, and pure electric vehicles.

Electrode materials play a decisive role in supercapacitors. According to the different working principles of electrode materials, they can be divided into two categories: one is electric double layer electrode materials represented by carbon-based materials, and the other is transition metal materials. Compound or conductive polymer-based pseudocapacitive electrode materials. Pseudocapacitive materials include not only the electric double layer charge storage, but also the charge stored by the redox reaction of electrolyte ions on the surface of the material, so the capacity can be increased by one to two orders of magnitude, thereby greatly improving the specific capacity and energy density. focus of researchers. The pseudocapacitor materials currently studied are: ruthenium dioxide, manganese oxide, vanadium oxide, nickel oxide, cobalt tetroxide, etc. Among them, cobalt tetroxide has excellent electronic storage capacity and extremely high theoretical capacity due to its low price and abundant natural resources. (up to 3500F/g) and other advantages, it is considered to be one of the materials with extremely high research potential.

In recent years, cobalt tetroxide with various microstructures and special morphologies has been successfully prepared. For example, Chinese patent CN103011306B authorizes a method for preparing nano-cube-shaped cobalt tetroxide, and Chinese patent CN104787806B authorizes a rose-shaped nano-cobalt tetroxide and its Preparation method, Chinese patent CN103247777B authorizes the lithium ion battery with cobalt tetroxide multi-shell hollow sphere negative electrode material and its preparation method, Chinese patent CN103979616B authorizes the preparation method of a rose-shaped tricobalt tetroxide, and so on. At present, there is no relevant report on the self-assembly of cobalt tetroxide nanosheets into graded microspheres.

SUMMARY OF THE INVENTION

The purpose of the present invention is to prepare a kind of cobalt tetroxide with micro-nano size effect and hierarchical structure; another purpose of the present invention is to provide the application of this material as a supercapacitor electrode material, and the supercapacitor electrode made of this material has good electrochemical performance, high specific capacitance and stable cycling characteristics. In order to achieve the above purpose, the present invention provides a preparation method and application of self-assembled tricobalt tetroxide graded microspheres.

The technical scheme of the present invention is summarized as follows:

A preparation method of self-assembled tricobalt tetroxide graded microspheres, the cobalt salt and polyvinyl alcohol are dispersed in a mixed solution of ethylene glycol and deionized water, a cobalt hydroxide precursor is obtained by a hydrothermal method, and then subjected to high temperature annealing treatment, and finally To obtain cobalt tetroxide microspheres with hierarchical structure formed by self-assembly of two-dimensional nanosheets, the preparation method specifically includes the following steps:

(1) Mix ethylene glycol and deionized water in a volume ratio of 5:1-1:5, then add 1-4 mmol of divalent inorganic cobalt salt to 15-50 mL of mixed solution, and then add 0.01-0.5 g of polyvinyl alcohol, Stir at room temperature for 0.5-1 h;

(2) Transfer the above mixed solution to a polytetrafluoroethylene-lined reaction kettle, and perform a hydrothermal reaction at 150-200° C. for 6-24 hours;

(3) After the reaction product was naturally cooled to room temperature, centrifuged and washed, the obtained precipitate was dried at 60°C for 12h, then heated to 350-600°C at a heating rate of 1-10°C/min, and calcined at a constant temperature for 2- 4h, the self-assembled tricobalt tetroxide graded microspheres were prepared.

Preferably, the divalent inorganic cobalt salt is one of cobalt acetate, cobalt nitrate, cobalt sulfate, and cobalt chloride.

Preferably, the operation process of the washing is as follows: washing the separated precipitate with deionized water for 5-8 times.

The invention also provides the application of the above-mentioned self-assembled tricobalt tetroxide graded microspheres. The self-assembled tricobalt tetroxide graded microspheres are specifically applied to supercapacitor electrode materials, and the specific capacitance retention rate of the electrode materials is as high as 70% or more.

Preferably, the preparation process of the supercapacitor electrode material is as follows:

(1) mix cobalt tetroxide, conductive agent and binder according to the mass ratio of (7-8):(1-2):1, and add in N-methylpyrrolidone, after ultrasonic dispersion, make slurry;

(2) The slurry is uniformly coated on the substrate, and after vacuum drying at 80-120° C. for 12-24 hours, the tableting treatment is performed at a pressure of 10-20 MPa.

Preferably, the conductive agent is one of acetylene black, graphite and Super P.

Preferably, the binder is one of PVDF and PTFE.

Preferably, the substrate is one of foamed nickel, copper foil, aluminum foil, and carbon paper. Beneficial effects of the present invention:

(1) The present invention uses polyvinyl alcohol as a structure-directing agent for synthesizing cobalt tetroxide for the first time, and utilizes the pyrolysis and gasification properties of polyvinyl alcohol to generate a large number of internal hollow hierarchical structures of cobalt tetroxide, and the design of hollow channels improves the porosity and ratio of cobalt tetroxide. Surface area, increase active sites, so that cobalt tetroxide has excellent electrochemical properties;

(2) the present invention adopts a one-step hydrothermal method, without adding any template agent or surfactant, the experimental operation is simple, the reaction conditions are mild, and the repeatability is good;

(3) the present invention is to self-assemble into microspheres with a hierarchical structure through the formed nanosheets under hydrothermal conditions;

(4) The cobalt tetroxide microspheres prepared by the present invention have a micro-nano size effect, and the hierarchical structure formed at the same time can effectively avoid the problem of agglomeration caused by too small size, which is beneficial to the application in the field of energy storage;

(5) The supercapacitor electrode made of the material of the present invention has good electrochemical performance, high specific capacitance and stable cycle characteristics.

Description of drawings

Fig. 1 is the X-ray diffraction pattern (XRD) of the prepared product of Example 1;

Fig. 2 is the scanning electron microscope (SEM) of the prepared product of embodiment 1;

Fig. 3 is the cyclic voltammetry curve of the product obtained in Example 1 as a supercapacitor electrode material, and the sweep speed is 10mV/s in 6mol/L KOH electrolyte;

Fig. 4 is the galvanostatic discharge curve diagram of the supercapacitor electrode material described in Example 1 in 6mol/LKOH electrolyte under different current densities;

FIG. 5 is a specific capacitance diagram of tricobalt tetroxide graded microspheres prepared in Example 1 under different current densities.

Detailed ways

The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, so that those skilled in the art can implement the invention with reference to the description.

Example 1

Weigh 0.5g of cobalt acetate, 0.02g of PVA, dissolve in 15ml of deionized water and stir for 30min, measure 15ml of ethylene glycol and add it to the above solution and stir for 30min, transfer the above mixed solution to a reaction kettle with a polytetrafluoroethylene lining , heated at an oven temperature of 180 °C for 24 h, cooled to room temperature naturally, the reaction product was centrifuged and washed with deionized water for 5 times, then dried at 60 °C for 12 h, and then the reaction product was calcined in a 400 °C tube furnace for 2 h, That is, the final desired cobalt tetroxide product is obtained.

The above-obtained cobalt tetroxide is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 8:1:1, uniformly dispersed in N-methylpyrrolidone (NMP) to form a slurry, and the slurry is uniformly coated on the foam nickel base. After drying in a drying oven at 80 °C for 24 h, the tableting treatment was performed, and the pressure was set to 10 MPa.

Example 2

Weigh 0.5g of cobalt acetate, 0.05g of PVA, dissolve in 15ml of deionized water and stir for 30min, measure 15ml of ethylene glycol and add it to the above solution and stir for 30min, transfer the above mixed solution to a reaction kettle with a polytetrafluoroethylene lining , heated at an oven temperature of 180 °C for 24 h, cooled to room temperature naturally, the reaction product was centrifuged and washed with deionized water for 6 times, then dried at 60 °C for 12 h, and then the reaction product was calcined in a 400 °C tube furnace for 2 h, That is, the final desired cobalt tetroxide product is obtained.

The above-obtained cobalt tetroxide is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 8:1:1, uniformly dispersed in N-methylpyrrolidone (NMP) to form a slurry, and the slurry is uniformly coated on the foam nickel base. After drying in a drying oven at 80 °C for 24 h, the tableting treatment was performed, and the pressure was set to 10 MPa.

Example 3

Weigh 0.5g of cobalt acetate, 0.02g of PVA, dissolve in 25ml of deionized water and stir for 30min, measure 5ml of ethylene glycol and add it to the above solution and stir for 30min, transfer the above mixed solution to a reaction kettle with a polytetrafluoroethylene lining , heated at an oven temperature of 180 °C for 24 h, cooled to room temperature naturally, the reaction product was centrifuged and washed with deionized water for 6 times, then dried at 60 °C for 12 h, and then the reaction product was calcined in a 400 °C tube furnace for 2 h, That is, the final desired cobalt tetroxide product is obtained.

The above-obtained cobalt tetroxide is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 8:1:1, uniformly dispersed in N-methylpyrrolidone (NMP) to form a slurry, and the slurry is uniformly coated on the foam nickel base. After drying in a drying oven at 80 °C for 24 h, the tableting treatment was performed, and the pressure was set to 10 MPa.

Example 4

Weigh 0.5g of cobalt acetate, 0.02g of PVA, dissolve in 15ml of deionized water and stir for 30min, measure 15ml of ethylene glycol and add it to the above solution and stir for 30min, transfer the above mixed solution to a reaction kettle with a polytetrafluoroethylene lining , heated at an oven temperature of 150°C for 24h, naturally cooled to room temperature, the reaction product was centrifuged and washed with deionized water for 7 times, then dried at 60°C for 12h, and then the reaction product was calcined in a 400°C tube furnace for 2h, That is, the final desired cobalt tetroxide product is obtained.

The above-obtained cobalt tetroxide is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 8:1:1, uniformly dispersed in N-methylpyrrolidone (NMP) to form a slurry, and the slurry is uniformly coated on the foam nickel base. After drying in a drying oven at 80 °C for 24 h, the tableting treatment was performed, and the pressure was set to 10 MPa.

Example 5

Weigh 0.5g of cobalt acetate, 0.02g of PVA, dissolve in 15ml of deionized water and stir for 30min, measure 15ml of ethylene glycol and add it to the above solution and stir for 30min, transfer the above mixed solution to a reaction kettle with a polytetrafluoroethylene lining , heated at an oven temperature of 180 °C for 12 h, cooled to room temperature naturally, the reaction product was centrifuged and washed with deionized water 7 times, then dried at 60 °C for 12 h, and then the reaction product was calcined in a 400 °C tube furnace for 2 h, That is, the final desired cobalt tetroxide product is obtained.

The above-obtained cobalt tetroxide is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 8:1:1, uniformly dispersed in N-methylpyrrolidone (NMP) to form a slurry, and the slurry is uniformly coated on the foam nickel base. After drying in a drying oven at 80 °C for 24 h, the tableting treatment was performed, and the pressure was set to 10 MPa.

Example 6

Weigh 0.5g of cobalt acetate, 0.02g of PVA, dissolve in 15ml of deionized water and stir for 30min, measure 15ml of ethylene glycol and add it to the above solution and stir for 30min, transfer the above mixed solution to a reaction kettle with a polytetrafluoroethylene lining , heated at an oven temperature of 180 °C for 24 h, cooled to room temperature naturally, the reaction product was centrifuged and washed with deionized water for 8 times, then dried at 60 °C for 12 h, and then the reaction product was calcined in a 600 °C tube furnace for 2 h, That is, the final desired cobalt tetroxide product is obtained.

The above-obtained cobalt tetroxide is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 8:1:1, uniformly dispersed in N-methylpyrrolidone (NMP) to form a slurry, and the slurry is uniformly coated on the foam nickel base. After drying in a drying oven at 80 °C for 24 h, the tableting treatment was performed, and the pressure was set to 10 MPa.

Example 7

Weigh 0.5g of cobalt acetate, 0.02g of PVA, dissolve in 15ml of deionized water and stir for 30min, measure 15ml of ethylene glycol and add it to the above solution and stir for 30min, transfer the above mixed solution to a reaction kettle with a polytetrafluoroethylene lining , heated at an oven temperature of 180 °C for 24 h, cooled to room temperature naturally, the reaction product was centrifuged and washed with deionized water for 8 times, then dried at 60 °C for 12 h, and then the reaction product was calcined in a 400 °C tube furnace for 4 h, That is, the final desired cobalt tetroxide product is obtained.

The above-obtained cobalt tetroxide is mixed with conductive agent acetylene black and binder PVDF in a mass ratio of 8:1:1, uniformly dispersed in N-methylpyrrolidone (NMP) to form a slurry, and the slurry is uniformly coated on the foam nickel base. After drying in a drying oven at 80 °C for 24 h, the tableting treatment was performed, and the pressure was set to 10 MPa.

The self-assembled tricobalt tetroxide graded microspheres prepared in Example 1 were characterized and electrochemical performance tested to confirm the beneficial effects of the present invention.

Figure 1 is the XRD spectrum of the product prepared in Example 1. The diffraction peaks in the spectrum are completely consistent with the standard tab JCPDS 42-1467, which are typical spinel structure cobalt tetroxide characteristic diffraction peaks, and no other impurity characteristic peaks appear. .

Fig. 2 is the SEM image of the product obtained in Example 1. As can be seen from the figure, the microspheres with a hierarchical structure are composed of nanosheets regularly assembled, and the interior of the microspheres runs through hollow channels, and the particle size is between 5- 20μm.

Fig. 3 is the cyclic voltammetry curve of the product obtained in Example 1 as a supercapacitor electrode material with a sweep rate of 10mV/s in 6mol/L KOH electrolyte. It can be seen that the peak of the reduction peak in the curve The current reaches 20mA, and the peak current of the oxidation peak is -15mA, that is, the tricobalt tetroxide product is used as the electrode material, which has an obvious redox process, which is a typical pseudocapacitive reaction mechanism.

FIG. 4 is a galvanostatic discharge curve diagram of the supercapacitor electrode material described in Example 1 in a 6 mol/L KOH electrolyte, a potential window range of 0-0.54 V, and different current densities. It can be seen from the figure that when the current density is 1A/g, the specific capacitance of the electrode reaches 265.9F/g, indicating that the material has the potential to be used as a supercapacitor.

FIG. 5 is a specific capacitance diagram of tricobalt tetroxide graded microspheres prepared in Example 1 under different current densities. It can be seen from the figure that when the current densities are 1A/g, 2A/g, 3A/g, 4A/g, 5A/g, 7A/g, and 10A/g, the specific capacitances are 265.9F/g and 259.2F, respectively. /g, 251.1F/g, 244.4F/g, 235F/g, 223.3F/g, 207F/g, when the current density increases from 1A/g to 10A/g, the supercapacitor electrode material prepared by the present invention The specific capacitance retention rate is as high as 78%.

Although the embodiment of the present invention has been disclosed as above, it is not limited to the application listed in the description and the embodiment, and it can be applied to various fields suitable for the present invention. For those skilled in the art, it can be easily Therefore, the invention is not limited to the specific details without departing from the general concept defined by the appended claims and the scope of equivalents.

Claims (8)

1. a preparation method of self-assembled tricobalt tetroxide graded microspheres, is characterized in that: cobalt salt, polyvinyl alcohol are dispersed in ethylene glycol and deionized water mixed solution, utilize hydrothermal method to obtain cobalt hydroxide precursor, then After high-temperature annealing treatment, the cobalt tetroxide microspheres with hierarchical structure formed by self-assembly of two-dimensional nanosheets are finally obtained, and the preparation method specifically includes the following steps: (1) Mix ethylene glycol and deionized water in a volume ratio of 5:1-1:5, then add 1-4 mmol of divalent inorganic cobalt salt to 15-50 mL of mixed solution, and then add 0.01-0.5 g of polyvinyl alcohol, Stir at room temperature for 0.5-1 h; (2) Transfer the above mixed solution to a polytetrafluoroethylene-lined reaction kettle, and perform a hydrothermal reaction at 150-200° C. for 6-24 hours; (3) After the reaction product was naturally cooled to room temperature, centrifuged and washed, the obtained precipitate was dried at 60°C for 12h, then heated to 350-600°C at a heating rate of 1-10°C/min, and calcined at a constant temperature for 2- 4h, the self-assembled tricobalt tetroxide graded microspheres were prepared; The self-assembled tricobalt tetroxide graded microspheres are specifically applied to supercapacitor electrode materials, and the specific capacitance retention rate of the electrode materials is as high as more than 70%. 2. the preparation method of a kind of self-assembled tricobalt tetroxide graded microspheres according to claim 1, is characterized in that, described divalent inorganic cobalt salt is a kind of in cobalt acetate, cobalt nitrate, cobalt sulfate, cobalt chloride. 3. A kind of preparation method of self-assembled tricobalt tetroxide graded microspheres according to claim 1, is characterized in that, the operation process of described washing: wash the separated precipitate with deionized water 5-8 times. 4. the application of a kind of self-assembled tricobalt tetroxide graded microsphere as described in any one of claim 1-3, it is characterized in that, this self-assembled tricobalt tetroxide graded microsphere is specifically applied to supercapacitor electrode material, and the specific capacitance of electrode material keeps The rate is as high as 70% or more. 5. the application of a kind of self-assembled tricobalt tetroxide graded microsphere according to claim 4, is characterized in that, the preparation process of described supercapacitor electrode material is as follows: (1) mix cobalt tetroxide, conductive agent and binder according to the mass ratio of (7-8):(1-2):1, and add in N-methylpyrrolidone, after ultrasonic dispersion, make slurry; (2) The slurry is uniformly coated on the substrate, and after vacuum drying at 80-120° C. for 12-24 hours, the tableting treatment is performed at a pressure of 10-20 MPa. 6. the application of a kind of self-assembled tricobalt tetroxide graded microspheres according to claim 5, is characterized in that, described conductive agent is a kind of in acetylene black, graphite, Super P. 7. the application of a kind of self-assembled tricobalt tetroxide graded microspheres according to claim 5, is characterized in that, described binder is a kind of in PVDF, PTFE. 8 . The application of a self-assembled tricobalt tetroxide graded microsphere according to claim 5 , wherein the substrate is one of foamed nickel, copper foil, aluminum foil, and carbon paper. 9 .

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