CN104505508A - Preparation method of nickel cobalt oxide electrode material - Google Patents

Abstract

A method for preparing a Ni _1.5 Co _1.5 O ₄ electrode material, comprising: providing nickel salt, cobalt salt, hexamethylenetetramine, ethanol and water, wherein the mass ratio of the ethanol to water is greater than 1:1 and less than or equal to 4:1; Mix the nickel salt, cobalt salt, hexamethylenetetramine, ethanol and water, and dissolve the nickel salt, cobalt salt, and hexamethylenetetramine to obtain a mixed solution; make the The mixed solution is subjected to solvothermal reaction to obtain a precursor; and the precursor is sintered in an oxygen-containing atmosphere to obtain the Ni _1.5 Co _1.5 O ₄ electrode material, and the Ni _1.5 Co _1.5 O ₄ electrode material is made of Ni Multiple 3D flower-like structures formed by self-assembly of _1.5 Co _1.5 O ₄ nanosheets.

Description

Preparation method of nickel-cobalt oxide electrode material

technical field

The invention relates to a preparation method of an electrode material, in particular to a preparation method of a Ni _1.5 Co _1.5 O ₄ electrode material.

Background technique

Nickel-cobalt oxide has become an ideal electrode material for lithium-ion batteries and supercapacitors that can meet practical applications due to its good electrical conductivity, high theoretical specific capacitance, good cycle performance, and environmental friendliness. However, nickel cobalt oxide (NiCo 2 O 4 ) currently used as electrode materials for lithium-ion batteries and supercapacitors is mainly nickel cobalt oxide (NiCo ₂ O ₄ ), and other nickel-cobalt oxides such as Ni _1.5 Co _1.5 O ₄ have not been used as lithium-ion batteries and supercapacitors. Research on electrode materials for supercapacitors.

However, people found that Ni _1.5 Co _1.5 O ₄ has better conductivity than NiCo ₂ O ₄ when studying the use of nickel cobalt oxide as a semiconductor material with a large band gap. The higher the conductivity, the better the performance as an electrode material, but the prior art mainly uses the Ni _1.5 Co _1.5 O ₄ film as a semiconductor material, because the Ni _1.5 Co _1.5 O ₄ film has almost no pores, and the specific surface area Smaller, it is not conducive to the diffusion of lithium ions and the full reaction of electrochemical reaction active sites, and the storage capacity of lithium ions is very limited, so when the Ni _1.5 Co _1.5 O ₄ thin film is directly used as an electrode material, its electrochemical performance is poor.

Contents of the invention

In view of this, it is indeed necessary to provide a preparation method of Ni _1.5 Co _1.5 O ₄ electrode material that is conducive to the full reaction of lithium ion diffusion and electrochemical reaction active sites.

A preparation method of Ni _1.5 Co _1.5 O ₄ electrode material, comprising:

Nickel salt, cobalt salt, hexamethylenetetramine, ethanol and water are provided, wherein the mass ratio of ethanol to water is greater than 1:1 and less than or equal to 4:1;

mixing the nickel salt, cobalt salt, hexamethylenetetramine, ethanol and water, and dissolving the nickel salt, cobalt salt, and hexamethylenetetramine to obtain a mixed solution;

subjecting the mixed solution to a hydrothermal reaction to obtain a precursor; and

The precursor is sintered under an oxygen-containing atmosphere to obtain the Ni _1.5 Co _1.5 O ₄ electrode material, and the Ni _1.5 Co _1.5 O ₄ electrode material is a plurality of self-assembled Ni _1.5 Co _1.5 O ₄ nanosheets Three-dimensional flower-like structure.

In the preparation method of Ni _1.5 Co _1.5 O ₄ electrode material provided by the present invention, hexamethylenetetramine is selected to carry out co-precipitation of nickel ions and cobalt ions, and Ni _1.5 with a molar ratio of nickel and cobalt elements of 1:1 can be obtained. Co _1.5 O ₄ electrode material, at the same time choose ethanol aqueous solution and hexamethylenetetramine to adjust the morphology of Ni _1.5 Co _1.5 O ₄ electrode material, and can prepare Ni _1.5 Co _1.5 O ₄ with three-dimensional flower structure electrode material. The Ni _1.5 Co _1.5 O ₄ electrode material with the three-dimensional flower-like structure has a large specific surface area, strong adsorption capacity, and small volume change during the stress release process, which is more conducive to the diffusion of lithium ions and the full reaction of the electrochemical reaction active sites. The improvement of lithium ion storage capacity, the modification of volume change and the improvement of speed in the process of adsorption and desorption of lithium are of great significance. The preparation method has the advantages of simple process, environmental protection, low cost and large-scale production.

Description of drawings

Fig. 1 is a flowchart of the preparation method of the Ni _1.5 Co _1.5 O ₄ electrode material of the present invention.

Figure 2a and Figure 2b are the XRD spectra of the green precursor powder and the black solid powder prepared in Example 1 of the present invention, respectively.

Fig. 3 is an energy dispersive EDX elemental analysis diagram of the black solid powder prepared in Example 1 of the present invention.

Figures 4a, 4b, 4c and 4d are field emission scanning electron microscope (FESEM) images at different magnifications of the black solid powder prepared in Example 1 of the present invention, respectively.

Detailed ways

Please refer to Fig. 1, the embodiment of the present invention provides a kind of preparation method of Ni _1.5 Co _1.5 O ₄ electrode material, comprising:

S1, providing nickel salt, cobalt salt, hexamethylenetetramine, ethanol and water, wherein the mass ratio of ethanol and water is greater than 1:1 and less than or equal to 4:1;

S2, mixing the nickel salt, cobalt salt, hexamethylenetetramine, ethanol and water, and dissolving the nickel salt, cobalt salt, and hexamethylenetetramine to obtain a mixed solution;

S3, subjecting the mixed solution to a hydrothermal reaction to obtain a precursor; and

S4, sintering the precursor in an oxygen-containing atmosphere to obtain the Ni _1.5 Co _1.5 O ₄ electrode material, the Ni _1.5 Co _1.5 O ₄ electrode material is formed by self-assembly of Ni _1.5 Co _1.5 O ₄ nanosheets Multiple three-dimensional flower-like structures.

In step S1, the nickel salt may be one or more of nickel nitrate, nickel chloride, nickel acetate and nickel sulfate. The cobalt salt may be one or more of nickel nitrate, nickel chloride, cobalt acetate and cobalt sulfate. The mixing ratio of the nickel salt and the cobalt salt is not limited, and at any mixing ratio, a Ni _1.5 Co _1.5 O ₄ electrode material with a molar ratio of nickel element and cobalt element of 1:1 can be obtained. Preferably, the mixing ratio of the nickel element and the cobalt element in the nickel salt and the cobalt salt may be 1:4-4:1. More preferably, the mixing ratio of the nickel element and the cobalt element in the nickel salt and the cobalt salt may be 1:2-2:1. Within the above ratio range, the nickel salt and cobalt salt can be fully utilized to reduce the waste of raw materials.

In step S2, the mixed solution is a uniform transparent clear solution. In the mixed solution, the ethanol and water form a mixed solvent, which is the reaction medium of the hydrothermal reaction. The nickel salt, cobalt salt and hexamethylenetetramine are dissolved in the mixed solvent. The nickel salt and the cobalt salt are dissolved in the mixed solvent to form nickel ions and cobalt ions respectively.

The ethanol and water may be mixed first to form the mixed solvent, and then the nickel salt, cobalt salt and hexamethylenetetramine are simultaneously added to the mixed solvent for mixing. It is also possible to mix the nickel salt, cobalt salt, ethanol and water first, and then add the hexamethylenetetramine for mixing. The mixing method is not limited, for example, stirring or ultrasonic mixing can be used.

In step S3, the precursor is light green powder, and the light green powder is nickel cobalt hydroxide. In the hydrothermal reaction process, the hexamethylenetetramine acts as a precipitant to convert the nickel ions and the cobalt ions into nickel-cobalt hydroxide precipitation, and because the hexamethylenetetramine The precipitation ability of the nickel ion and the cobalt ion is similar, so in the nickel-cobalt hydroxide, the molar ratio of the nickel element to the cobalt element is 0.91-1.09. Preferably, the ratio of the mass of the hexamethylenetetramine to the sum of the nickel salt and the cobalt salt is 1:1 to 3:1, and the hexamethylenetetramine within the range of the ratio can make the Nickel ions and cobalt ions are sufficiently precipitated.

The hexamethylenetetramine and the mixed solvent also function as a shape guiding agent, and under the cooperation of the two, a three-dimensional flower-like structure of nickel-cobalt hydroxide can be obtained, and the three-dimensional flower-like structure of nickel Cobalt hydroxide is formed by self-assembly of nickel-cobalt hydroxide nanosheets. During the sintering process in the subsequent step S4, the nickel-cobalt hydroxide is oxidized to Ni _1.5 Co _1.5 O ₄ , while the three-dimensional flower-like structure remains unchanged, thereby obtaining the three-dimensional flower-like structure of Ni _1.5 Co _1.5 O ₄ electrode material. When the mass ratio of ethanol to water is greater than 1:1 and less than or equal to 4:1, the three-dimensional flower-like Ni _1.5 Co _1.5 O ₄ electrode material with regular shape and uniform size can be formed, and the three-dimensional flower The Ni _1.5 Co _1.5 O ₄ electrode material is a spherical structure composed of dozens of Ni _1.5 Co _1.5 O ₄ nanosheets. In this spherical structure, each of the Ni _1.5 Co _1.5 O ₄ nanosheets is like a petal extend outward from the center of the spherical structure, and a plurality of said Ni _1.5 Co _1.5 O ₄ nanosheets partially intersect, and the spherical structure has voids formed by said Ni _1.5 Co _1.5 O ₄ nanosheets in all directions and tunnel. The Ni _1.5 Co _1.5 O ₄ electrode material with the three-dimensional flower-like structure has a large specific surface area, strong adsorption capacity, and small volume change during the stress release process, which is more conducive to the diffusion of lithium ions and the full reaction of the electrochemical reaction active sites. The improvement of lithium ion storage capacity, the modification of volume change and the improvement of speed in the process of adsorption and desorption of lithium are of great significance. Preferably, the mass ratio of ethanol to water is greater than or equal to 2:1 and less than or equal to 3:1. Preferably, the ratio of the mass of the hexamethylenetetramine to the mass sum of the ethanol and water is 1:4-1:2.

The mixed solution can be transferred to a steel-lined polytetrafluoroethylene reactor for hydrothermal reaction. The reaction temperature of the hydrothermal reaction is 80°C to 260°C, if the reaction temperature is too low, the dissociation constant of the hexamethylenetetramine is also low, so that it cannot function as a precipitant and a shape guiding agent, If the reaction temperature is too high, the hexamethylenetetramine will be decomposed. Preferably, the reaction temperature is 100° C. to 140° C., and this temperature range is more conducive to the formation of the nickel-cobalt hydroxide with a uniform and consistent three-dimensional flower-like structure. The hydrothermal reaction time is greater than 2 hours to make the hydrothermal reaction more complete. Preferably, the hydrothermal reaction time is 2 hours to 8 hours.

After the precursor is obtained through the step S3, the precursor can be further separated and purified. The separation method can be filtration or centrifugation. The separated precursor may be further washed. In the embodiment of the present invention, the precursor was washed several times with water and absolute ethanol respectively. The separated and purified precursor may be further dried to remove the solvent. The drying can be vacuum filtration or heating drying.

In step S4, the sintering temperature may be 300° C. to 500° C., and the sintering time may be 2 hours to 10 hours. The nickel cobalt hydroxide undergoes an oxidation reaction during the sintering process to form the Ni _1.5 Co _1.5 O ₄ electrode material. The Ni _1.5 Co _1.5 O ₄ electrode material is black powder.

Example 1

Add 1 mmol of Ni(NO ₃ ) ₂ ·6H ₂ O and 2 mmol of Co(NO ₃ ) ₂ ·6H ₂ O into the mixed solvent of ethanol and water, stir for 30 minutes, the mixing ratio of ethanol and water is 2:1 , and then slowly add hexamethylenetetramine (HMT), the ratio of the mass of hexamethylenetetramine to the sum of the mass of Ni(NO ₃ ) ₂ ·6H ₂ O and Co(NO ₃ ) ₂ ·6H ₂ O is 2:1, stirred for 30 minutes to form a uniform pink mixed solution;

Transfer the above mixed solution to a steel-lined polytetrafluoroethylene reactor, heat at 90°C for 4 hours, then cool to room temperature with the furnace, take it out, and go through vacuum filtration-three washings-vacuum filtration-three ethanol washings. The prepared sample was purified and dried in vacuum at 60°C for 12 hours to obtain light green precursor powder;

The prepared green precursor powder was placed in a muffle furnace, and in an air atmosphere, the temperature was raised to 350°C at a rate of 1°C per minute, kept for 3 hours, and then cooled to room temperature with the furnace to obtain a black solid powder.

Please refer to FIG. 2 , the analysis of the XRD pattern shows that the green precursor is a cobalt-nickel hydroxide structure, and the black solid powder is a spinel-type cobalt-nickel oxide structure. Please refer to Fig. 3 and the following table. Through EDX analysis, it can be determined that the Co/Ni atomic ratio is 1:1, so it can be inferred that the structural formula of the spinel-type cobalt-nickel oxide is Ni _1.5 Co _1.5 O ₄ . Please refer to FIG. 4 , it can be seen that the black solid powder is a three-dimensional flower-like structure formed by self-assembly of Ni _1.5 Co _1.5 O ₄ nanosheets with uniform appearance.

element weight percentage (%) Atomic percentage (%) o 32.94 64.36 co 34.98 18.55 Ni 32.09 17.09 Total 100.00 100.00

In the preparation method of Ni _1.5 Co _1.5 O ₄ electrode material provided by the present invention, hexamethylenetetramine is selected to carry out co-precipitation of nickel ions and cobalt ions, and Ni _1.5 with a molar ratio of nickel and cobalt elements of 1:1 can be obtained. Co _1.5 O ₄ electrode material, at the same time choose ethanol aqueous solution and hexamethylenetetramine to adjust the morphology of Ni _1.5 Co _1.5 O ₄ electrode material, and can prepare Ni _1.5 Co _1.5 O ₄ with three-dimensional flower structure electrode material. The Ni _1.5 Co _1.5 O ₄ electrode material with the three-dimensional flower-like structure has a large specific surface area, strong adsorption capacity, and small volume change during the stress release process, which is more conducive to the diffusion of lithium ions and the full reaction of the electrochemical reaction active sites. The improvement of lithium ion storage capacity, the modification of volume change and the improvement of speed in the process of adsorption and desorption of lithium are of great significance. The preparation method has the advantages of simple process, environmental protection, low cost and large-scale production.

In addition, those skilled in the art can also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should be included within the scope of protection claimed by the present invention.

Claims (9)

1. a Ni _1.5co _1.5o ₄the preparation method of electrode material, comprising:

There is provided nickel salt, cobalt salt, hexa, ethanol and water, wherein, the mass ratio of described second alcohol and water is greater than 1:1 and is less than or equal to 4:1;

Described nickel salt, cobalt salt, hexa, ethanol and water are mixed, and described nickel salt, cobalt salt, hexa are dissolved, obtain a mixed solution;

Make described mixed solution carry out hydro-thermal reaction, obtain presoma; And

Carry out under an oxygen-containing atmosphere sintering described presoma, obtain described Ni _1.5co _1.5o ₄electrode material, described Ni _1.5co _1.5o ₄electrode material is by Ni _1.5co _1.5o ₄the multiple three-dimensional flower-shaped structure that nanometer sheet self assembly is formed.

2. Ni as claimed in claim 1 _1.5co _1.5o ₄the preparation method of electrode material, is characterized in that, described presoma is nickel cobalt hydroxide, and in described nickel cobalt hydroxide, the mol ratio of nickel element and cobalt element is 0.91 ~ 1.09.

3. Ni as claimed in claim 1 _1.5co _1.5o ₄the preparation method of electrode material, is characterized in that, the mass ratio of described second alcohol and water is 2:1 ~ 3:1.

4. Ni as claimed in claim 1 _1.5co _1.5o ₄the preparation method of electrode material, is characterized in that, the quality of described hexa and the quality of described second alcohol and water and ratio be 1:4 ~ 1:2.

5. Ni as claimed in claim 1 _1.5co _1.5o ₄the preparation method of electrode material, is characterized in that, the reaction temperature of described hydro-thermal reaction is 100 DEG C ~ 140 DEG C.

6. Ni as claimed in claim 1 _1.5co _1.5o ₄the preparation method of electrode material, is characterized in that, described hexa and described nickel salt and cobalt salt quality and mass ratio be 1:1 ~ 3:1.

7. Ni as claimed in claim 1 _1.5co _1.5o ₄the preparation method of electrode material, is characterized in that, described nickel salt is one or more in nickel nitrate, nickel chloride, nickel acetate and nickelous sulfate, and described cobalt salt is one or more in cobalt nitrate, cobalt chloride, cobalt acetate and cobaltous sulfate.

8. Ni as claimed in claim 1 _1.5co _1.5o ₄the preparation method of electrode material, is characterized in that, described sintering temperature is 300 ~ 500 DEG C, and described sintering time is 2 ~ 8 hours.

9. Ni as claimed in claim 1 _1.5co _1.5o ₄the preparation method of electrode material, is characterized in that, each three-dimensional flower-shaped structure is by tens Ni _1.5co _1.5o ₄the spherical structure of nanometer sheet composition, in this spherical structure, each described Ni _1.5co _1.5o ₄the center of nanometer sheet all from this spherical structure as petal stretches out, and multiple described Ni _1.5co _1.5o ₄nanometer sheet partial intersection, this spherical structure all has in all directions by described Ni _1.5co _1.5o ₄the space that nanometer sheet is formed and duct.