CN105390706B - A kind of preparation method of cobalt manganese VPO catalysts - Google Patents

Abstract

The invention provides a preparation method of a cobalt-manganese-oxygen catalyst and its application in a lithium-air battery. The cobalt-manganese-oxygen catalyst is prepared by rapid solution stirring at room temperature, specifically including the following steps: 1) dissolving potassium permanganate and manganese sulfate in water and mixing them uniformly, reacting at room temperature, and then performing suction filtration and drying to obtain 2) Dispersing the obtained amorphous MnO ₂ powder and cobalt chloride in water, stirring and mixing uniformly to obtain mixed _solution I; 3) mixing sodium borohydride and inorganic alkali, and dissolving in water and stirring uniformly to obtain Mixed solution II; 4) The obtained mixed solution II is added to the mixed solution I, and the reaction is carried out under stirring conditions, and the obtained product is the cobalt-manganese-oxygen catalyst. The raw materials involved in the invention are cheap and easy to obtain, the process is simple and easy, and the output is relatively large. The prepared cobalt-manganese-oxygen catalyst is in the shape of a porous nanosphere, and when applied to a lithium-air battery, it exhibits excellent electrochemical performance.

Description

A kind of preparation method of cobalt manganese oxygen catalyst

technical field

The invention belongs to the technical field of inorganic materials and electrochemical device materials, and in particular relates to a preparation method of a cobalt-manganese-oxygen catalyst.

Background technique

With the intensified consumption of irreversible energy such as petroleum, the chemical energy system is facing increasingly severe challenges. However, the energy density of traditional lithium-ion batteries still cannot meet the growing energy demand. In this case, because the energy density of lithium-air batteries is much higher than that of lithium-ion batteries, its specific energy or energy density is comparable to that of gasoline and diesel. Similarly, a single charge is expected to extend the range of electric vehicles by more than 500km, which has attracted widespread attention. More importantly, lithium-air batteries do not produce harmful pollutants during the reaction process, and are a new type of energy storage system with great potential to replace lithium-ion batteries.

Since Bruce first reported the rechargeable lithium-air battery in 2006, foreign researchers have turned their attention to the new secondary lithium battery system (lithium-air battery) in the development of breakthrough power lithium batteries. A lithium-air battery is a battery system in which metallic lithium is used as the negative electrode, the air electrode is used as the positive electrode, and external oxygen is used as the reactive substance, which reacts under the action of a catalyst. At present, lithium-air batteries have become the focus and focus of global power battery and energy storage battery research.

However, the lithium peroxide produced by the cathode discharge reaction in the lithium-air battery is insoluble in the organic electrolyte, and is easy to deposit on the pores and surfaces of the porous air electrode particles. At the same time, the reaction barrier of the lithium peroxide decomposition reaction is high, the reaction is difficult to occur, and the decomposition is often not complete, which limits the performance of the battery. Therefore, it is very critical to select a suitable catalyst to improve the energy efficiency of Li-air batteries.

Catalysts are crucial to lithium-air batteries, affecting the energy efficiency, power and other performance of batteries. Catalysts have always been the research focus of lithium-air batteries. At the same time, there are more and more types of catalysts being developed. At present, the most researched catalysts are metal oxides, noble metals, and nitrogen-containing metal compounds. However, the high raw material cost of noble metals is not conducive to practical applications. Therefore, it is of great application significance to further explore other catalysts suitable for lithium-air batteries, adjust their size, morphology and internal structure, and improve their preparation processes and conditions.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a cobalt-manganese-oxygen catalyst. The raw materials required by the method are common and easy to obtain, and the preparation process is simple, the reaction conditions are mild, and the output is large. The prepared cobalt-manganese-oxygen catalyst is applied to the preparation of lithium-ion batteries. electrode, showing excellent electrochemical performance.

To achieve the above object, the technical solution adopted in the present invention is:

A preparation method of cobalt-manganese-oxygen catalyst, it comprises the following steps:

1) Potassium permanganate and manganese sulfate are dissolved in water and mixed uniformly, reacted at room temperature, and the resulting product is subjected to suction filtration and drying to obtain amorphous MnO ₂ powder;

2) The obtained _MnO2 powder and cobalt chloride are dispersed in water, stirred and mixed uniformly to obtain mixed solution I;

3) Mix sodium borohydride and inorganic base, dissolve in water and stir evenly to obtain mixed solution II;

4) Add the obtained mixed solution II to the mixed solution I, and react under stirring conditions, and the obtained product is the cobalt-manganese-oxygen catalyst.

In the above scheme, the reaction time in step 1) is 5 to 12 hours.

According to said scheme, the mol ratio of described potassium permanganate and manganese sulfate is 2:3.

According to the above scheme, the molar ratio of the amorphous _MnO powder to cobalt chloride is 2:1.

According to the above scheme, the inorganic base is sodium hydroxide or potassium hydroxide.

According to the above scheme, the molar ratio of the sodium borohydride to the inorganic base is (50-200):1.

According to the above scheme, the stirring temperature in the step 4) is 25-60° C., and the stirring time is 10-60 min.

The cobalt-manganese-oxygen catalyst prepared according to the above scheme is formed by stacking nanoparticles with a size of 0.5-1 μm; wherein the size of the nanoparticles is 3-5 nm.

The cobalt-manganese-oxygen catalyst prepared according to the above scheme is applied to the preparation of lithium-ion battery electrodes, specifically comprising the following steps: using an organic solvent (N-methylpyrrolidone) to prepare the cobalt-manganese-oxygen catalyst with a binding agent (polyylidene fluoride) Ethylene) and carbon materials are mixed, and the mixed slurry is coated on the nickel foam as the positive electrode of the lithium-air battery, and then the lithium-air battery is assembled under an argon atmosphere.

According to the above scheme, applying the cobalt-manganese-oxygen catalyst prepared by the present invention to a lithium-air battery can reduce the reaction barrier of lithium peroxide decomposition reaction and improve the electrochemical performance of the lithium-air battery.

Compared with prior art, the beneficial effect of the present invention is:

1) The raw materials involved in the present invention are cheap and easy to obtain, and the manganese sulfate and sodium hydroxide used are commonly used medicines, and no toxic and harmful organic surfactants and additives are used, which is safe and environmentally friendly.

2) The preparation process of the present invention is simple and environment-friendly, is carried out at room temperature, and has low energy consumption. Utilizing the strong reducibility of sodium borohydride, cobalt element can be incorporated into the crystal structure of amorphous _MnO2 at room temperature, and there is no special limitation on the reaction vessel, the reaction is safe and stable, with high repeatability and large output. Meet the requirements of actual production applications.

3) The present invention can regulate the morphology of cobalt manganese oxide by adjusting the stirring temperature and raw material content, and prepare cobalt manganese oxide with various shapes.

4) Applying the cobalt-manganese-oxygen catalyst prepared by the present invention to lithium-air batteries can reduce the reaction barrier of lithium peroxide decomposition reaction, improve the electrochemical performance of lithium-air batteries, and meet the demand for high energy storage devices in actual production .

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is the XRD pattern of the product obtained in Example 1 of the present invention.

Figure 2 is a SEM image of the product obtained in Example 1 of the present invention.

Fig. 3 is a diagram of the electrochemical performance of the lithium-air battery obtained in Example 1 of the present invention.

Figure 4 is a SEM image of the product obtained in Example 2 of the present invention.

Figure 5 is a SEM image of the product obtained in Example 3 of the present invention.

Figure 6 is a SEM image of the product obtained in Example 4 of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

In the following examples, unless otherwise specified, all reagents used are commercially available chemical reagents.

Example 1

A preparation method of cobalt-manganese-oxygen catalyst, comprising the following steps:

1) Potassium permanganate and manganese sulfate were dissolved in 80mL water with a molar ratio of 2:3 and mixed evenly, reacted at room temperature for 6h, and obtained amorphous _MnO2 powder after suction filtration and drying;

2) The obtained amorphous _MnO2 powder and cobalt chloride were dissolved in 10 mL of water at a molar ratio of 2:1, stirred for 15 min, and mixed uniformly to obtain a mixed solution I;

3) Mix 0.02mol of sodium borohydride and 0.1mmol of sodium hydroxide, dissolve in 10mL of water, stir for 15min, and mix uniformly to obtain mixed liquid II;

4) Add the obtained mixed solution II into the mixed solution I, and react under stirring conditions, the stirring temperature is 25° C., and the stirring time is 10 min. After the reaction is completed, filter to obtain the final product.

The product obtained in this example was subjected to X-ray diffraction analysis (see Figure 1), and the results showed that the obtained product was consistent with the target product, which was cobalt manganese oxide. Scanning electron microscope analysis results show that the obtained product is a porous nanosphere with a size of about 800nm, and the pores are in the form of stacked pores. The SEM image is shown in Figure 2.

Applying the cobalt-manganese-oxygen catalyst prepared in this example to prepare the positive electrode of a lithium-air battery specifically includes the following steps: using an organic solvent (N-methylpyrrolidone) to prepare the cobalt-manganese-oxygen catalyst with a binder (polyylidene fluoride Ethylene) and carbon materials are mixed, and the mixed slurry is coated on the nickel foam as the positive electrode of the lithium-air battery, and then the lithium-air battery is assembled under an argon atmosphere. The button half-cell test results show that the cobalt-manganese-oxygen catalyst prepared in this embodiment is prepared as the positive electrode of lithium-air battery, showing good electrochemical performance (see Figure ³ ): at a current density of 0.15mA/cm , The first cycle discharge specific capacity of the battery reaches 4627.7mAh/g.

Example 2

A preparation method of cobalt-manganese-oxygen catalyst, comprising the following steps:

1) Potassium permanganate and manganese sulfate were dissolved in 80mL water with a molar ratio of 2:3 and mixed evenly, reacted at room temperature for 6h, and obtained amorphous _MnO2 powder after suction filtration and drying;

2) The obtained amorphous _MnO powder and cobalt chloride were dissolved in 10 mL of water at a molar ratio of 2:1, stirred for 15 min, and mixed uniformly to obtain solution I;

3) Mix 5mmol of sodium borohydride and 0.1mmol of sodium hydroxide, dissolve in 10mL of water, stir for 15min, and mix well to obtain a mixture II;

4) The obtained solution II was added to the mixed solution I, and the reaction was carried out under the condition of stirring, the stirring temperature was 25° C., and the stirring time was 10 min. After the reaction was completed, the cobalt-manganese-oxygen catalyst was obtained by filtering.

The product obtained in this embodiment is analyzed by a scanning electron microscope (see Figure 4), and the results show that the obtained product is a porous microsphere with good dispersion, and the microsphere is assembled by small nano-particles, with a size of about 700nm, and the existing form of the hole is Stacked holes.

^The cobalt-manganese-oxygen catalyst prepared in this embodiment is applied to the positive electrode (same as Example 1) for preparing lithium-air batteries, showing good electrochemical performance: the results of the button half-cell test show that at 0.15mA/cm Under the current density, the first cycle discharge specific capacity of the battery reaches 4153mAh/g.

Example 3

A preparation method of cobalt-manganese-oxygen catalyst, comprising the following steps:

1) Potassium permanganate and manganese sulfate were dissolved in 80mL water with a molar ratio of 2:3 and mixed evenly, reacted at room temperature for 6h, and obtained amorphous _MnO2 powder after suction filtration and drying;

2) The obtained amorphous _MnO powder and cobalt chloride were dissolved in 10 mL of water at a molar ratio of 2:1, stirred for 15 min, and mixed uniformly to obtain solution I;

3) Mix 0.02mol of sodium borohydride and 0.1mmol of potassium hydroxide, dissolve in 10mL of water, stir for 15min, and mix uniformly to obtain a mixture II;

4) The obtained solution II was added to the mixed solution I, and the reaction was carried out under the condition of stirring, the stirring temperature was 60° C., and the stirring time was 10 min. After the reaction was completed, the cobalt-manganese-oxygen catalyst was obtained by filtering.

The product obtained in this example was analyzed by a scanning electron microscope (see FIG. 4), and the results showed that the obtained product was irregular microspheres formed by accumulation of nanoparticles, with a size of about 1 micron. The SEM image is shown in FIG. 5.

Example 4

A preparation method of cobalt-manganese-oxygen catalyst, comprising the following steps:

1) Potassium permanganate and manganese sulfate were dissolved in 80mL water with a molar ratio of 2:3 and mixed evenly, reacted at room temperature for 6h, and obtained amorphous _MnO2 powder after suction filtration and drying;

2) The obtained amorphous _MnO powder and cobalt chloride were dissolved in 10 mL of water at a molar ratio of 2:1, stirred for 15 min, and mixed uniformly to obtain solution I;

3) Mix 5mmol of sodium borohydride and 0.1mmol of potassium hydroxide, dissolve in 10mL of water, stir for 15min, and mix uniformly to obtain mixed solution II;

4) Add the obtained solution II into the mixed solution I, and carry out the reaction under the condition of stirring, the stirring temperature is 25° C., and the stirring time is 1 h. After the reaction is completed, filter to obtain the cobalt-manganese-oxygen catalyst.

The result of scanning electron microscope analysis of the product obtained in this example shows that the product is nanospheres assembled with hairy nanowires, and its size is about 500 nm. The SEM image of the product is shown in FIG. 6 .

The cobalt-manganese-oxygen catalyst prepared in this example is applied to the positive electrode of the lithium-air battery (same as Example 1), showing good electrochemical performance: the results of the button half-cell test show that at 0.15mA/cm ² Under the high current density, the specific capacity of the first discharge cycle of the battery reaches 3806mAh/g.

Each raw material enumerated in the present invention can realize the present invention, and the upper and lower limit value of each raw material, interval value can realize the present invention, the upper and lower limit value and interval value of process parameter (such as temperature, time etc.) of the present invention The present invention can be realized, and the embodiments are not listed one by one here.

Claims (7)

1. a kind of lithium-air battery preparation method of cobalt manganese VPO catalysts, which is characterized in that include the following steps：

1) potassium permanganate and manganese sulfate is soluble in water and be uniformly mixed, it is reacted at room temperature, products therefrom carries out suction filtration baking Do to obtain unformed MnO₂Powder；

2) by gained MnO₂Powder and cobalt chloride are dispersed in water, and are uniformly mixed, and mixed liquor I is obtained；

3) sodium borohydride is mixed with inorganic base, and it is soluble in water stir evenly, obtain mixed liquor I I；

4) gained mixed liquor I I is added in mixed liquor I, is reacted under agitation, the as described cobalt manganese of products therefrom VPO catalysts；

The molar ratio of the sodium borohydride and inorganic base is (50~200):1.

2. preparation method according to claim 1, which is characterized in that the molar ratio of the potassium permanganate and manganese sulfate is 2: 3。

3. preparation method according to claim 1, which is characterized in that the unformed MnO₂Mole of powder and cobalt chloride Than being 2:1.

4. preparation method according to claim 1, which is characterized in that the inorganic base is sodium hydroxide or potassium hydroxide.

5. preparation method according to claim 1, which is characterized in that the whipping temp in the step 4) is 25~60 DEG C, mixing time is 10~60min.

6. cobalt manganese VPO catalysts prepared by any one of Claims 1 to 5 preparation method, which is characterized in that it is by nanometer Grain is accumulated, and size is 0.5~1 μm；Wherein the size of nano particle is 3~5nm.

7. application of the cobalt manganese VPO catalysts in lithium-air battery described in claim 6.