CN115785464A - Preparation method and application of electrode material Ln(s) -Co compound of super capacitor - Google Patents

Abstract

The invention belongs to the field of functional material preparation, and particularly relates to a preparation method and application of a supercapacitor electrode material Ln(s) -Co compound, which are implemented according to the following steps: (1) Putting pyridine 2,5-dicarboxylic acid, rare earth nitrate and cobalt nitrate into a reaction kettle, adding deionized water, and stirring at room temperature; (2) Transferring the product obtained in the step (1) to an oven for constant temperature treatment; (3) Naturally cooling the product obtained in the step (2) to room temperature, washing with deionized water and ultrasonically cleaning, and then filtering to obtain mauve acicular crystals; drying under natural conditions to obtain the Ln(s) -Co-MOF material. (4) And (4) calcining the product obtained in the step (3) under the protection of inert gas to obtain the Ln(s) -Co compound which can be used for the electrode of the super capacitor. The method has good reproducibility, the target product has ideal shape and structure, and the performance of the electrode active material used as the super capacitor is excellent.

Description

Preparation method and application of supercapacitor electrode material Ln(s)-Co composite

technical field

The invention belongs to the field of preparation of functional materials, in particular to a preparation method and application of a supercapacitor electrode material Ln(s)-Co composite.

Background technique

Supercapacitors have the advantages of long cycle life, high power density, short charge and discharge time, and wide operating temperature range, which promote the development of the new energy industry, and have achieved rapid development in the field of energy storage, especially in the field of electric vehicles. Currently, electrode materials for supercapacitors are mainly based on carbon materials, transition metal oxides, and conducting polymers. However, many reported materials have disadvantages in terms of size, microstructure and stability. The application of traditional materials is limited.

Metal Organic Frameworks (MOFs) due to their unique two-dimensional and three-dimensional morphology, adjustable framework structure, large specific surface area, and more active sites that are conducive to electrolyte transport and ion transport, etc. Advantages, and the ability of complex-derived materials to maintain the original framework of the complex or in situ phase transition has attracted the attention of researchers. Complexes and their derivative materials have been developed rapidly as one of the candidate substances for sustainable energy applications. It is currently used in supercapacitors.

In recent years, MOF materials have been widely used as supercapacitor electrode materials due to their high specific surface area, tunable pore size distribution, and tunable composition and morphology. However, MOF materials have encountered many problems in practical applications, such as: (1) MOF framework is easy to collapse during charging and discharging, and significant volume effect; (2) MOF materials have poor electrical conductivity, which restricts the electron transport performance. ; (3) The morphology of derivatives prepared by MOF materials is uncontrollable or the specific surface is reduced after sintering. This hinders its application in the field of electrochemistry to a certain extent.

Contents of the invention

In order to solve some problems in the existing MOF materials mentioned above, the main purpose of the present invention is to invent an electrode material that can be used for supercapacitors with high specific capacity, good cycle stability and stable structure. The product of the present invention also highlights a technical highlight, that is, it is found in the process of preparing derivatives that the product structure at conventional calcination temperature (450-600°C) retains the original skeleton structure. However, a phase transition occurs in a high-temperature narrow region (750-800 °C), and the phase transition product has excellent electrochemical properties and can be used as an ideal electrode material for supercapacitors. Afterwards, the product obtained by continuing to raise the temperature can still be understood as the collapsed fouling area of the conventional framework.

In order to solve the problems of the technologies described above, the present invention is achieved in that:

A kind of preparation method of supercapacitor electrode material Ln (s)-Co compound, implement as follows:

(1) Put pyridine 2,5-dicarboxylic acid, rare earth nitrate, and cobalt nitrate in a reaction kettle, add deionized water, and stir at room temperature;

(2) Transfer the product obtained in step (1) to an oven for constant temperature treatment;

(3) Naturally cool the product obtained in step (2) to room temperature, rinse with deionized water and ultrasonically clean, and then filter to obtain purple-red needle-like crystals; dry under natural conditions to obtain Ln(s)-Co-MOF material ;

(4) Calcining the product obtained in step (3) under the protection of an inert gas to obtain the target product Ln(s)-Co composite, which is an electrode material for a supercapacitor.

Further, the rare earth nitrate in the present invention is cerium nitrate, praseodymium nitrate, neodymium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate or holmium nitrate.

Further, in step (1) of the present invention, the mass ratios of pyridine 2,5-dicarboxylic acid, rare earth nitrate, cobalt nitrate and deionized water are: 0.3-0.4: 0.25-0.3: 0.15-0.2: 10-12.

Furthermore, in the step (2) of the present invention, the preheating temperature of the oven is 180°C-190°C; the constant temperature is 180°C-190°C; and the constant temperature time is 55-60h.

Further, in step (3) of the present invention, the product obtained in step (2) is washed 2 to 3 times with deionized water, and dried under natural conditions for 10 to 12 hours to obtain the preparation method of Ln(s)-Co-MOF .

Further, in the step (4) of the present invention, the calcination temperature is 750°C-800°C; the constant temperature time is 1.5-2h.

The application of the product obtained in the preparation method of the above-mentioned supercapacitor electrode material Ln(s)-Co composite in the supercapacitor electrode is implemented in the following steps: Ln(s)-Co composite, polyvinylidene fluoride, conductive acetylene black and Fully grind N-methylpyrrolidone to obtain supercapacitor electrode slurry; apply the supercapacitor electrode slurry evenly on foamed nickel to obtain electrode sheets, and then dry, cool and slice to obtain supercapacitor test electrodes .

Further, the mass ratios of the Ln(s)-Co composite, conductive acetylene black and polyvinylidene fluoride in the present invention are: 5-8:1-3:0.5-2.

Further, in the present invention, the electrode sheet is dried in a 0.1Mpa vacuum oven at 80-110° C. for 10-13 hours.

Further, in the supercapacitor test of the present invention, the electrolyte used is a KOH solution with a concentration of 3-6M.

Rare earth lanthanides (Ln(s)) have the characteristics of tapered properties, and their use in supercapacitor electrode materials has the advantage of reducing the volume effect during charge and discharge, which can effectively improve the performance of supercapacitors. Based on this, the rare earth-transition metal bimetallic MOF material derivatives not only have more active sites, but also the application of bimetals can make full use of their respective characteristics, thereby improving the performance of supercapacitors. There are few reports on rare earth-transition metal bimetallic MOF materials (Ln(s)-Co-MOF), and reports on derivatives prepared on this basis (Ln(s)-Co composites) are rare.

The invention adopts pyridine 2,5-dicarboxylic acid, rare earth nitrate, and cobalt nitrate, and the synthesized material Ln(s)-Co-MOF has a stable structure, and is a supercapacitor electrode material precursor with a novel structure. The Ln(s)-Co composite prepared with Ln(s)-Co-MOF as a precursor has many active sites and a special structure. The material is made into a supercapacitor electrode material for electrochemical tests, showing excellent electrochemical performance. When the current density is 2A·g ^-1 , it shows a specific capacity of 1440 F·g ^-1 . After 2000 cycles at a current density of 20 A g ^-1 , the capacitance is more than 88.5% of the initial capacitance.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. The scope of protection of the present invention is not limited to the expression of the following content.

Fig. 1 is the Ln(s)-Co-MOF crystal morphology figure under the optical microscope of the present invention;

Fig. 2 is the pyrolysis curve diagram of Ln(s)-Co-MOF of the present invention;

Fig. 3 is the SEM characterization diagram of the Ln(s)-Co complex of the present invention;

Fig. 4 is the galvanostatic charge and discharge diagram of the Ln(s)-Co composite of the present invention;

Fig. 5 is a cycle graph of the Ln(s)-Co complex of the present invention.

Detailed ways

As shown in the figure, the electrode active material Ln(s)-Co composite, conductive acetylene black and polyvinylidene fluoride (PVDF) were mixed in a ratio of 7:2:1, and then an appropriate amount of solvent N-methylpyrrolidone was added (NMP). Grind the mixture well to form a homogeneous paste. The paste slurry was then coated on the nickel foam, and the nickel foam coated with the active material was dried in a vacuum (0.1 MPa) oven at 80 °C for 12 h. After cooling to room temperature, the nickel foam coated with the active material was taken out of the oven. During the electrochemical test, the nickel foam coated with active materials was cut into 1*2 cm ² sample pieces, and then the weight of the electrode was accurately weighed using a ten-thousandth balance. Finally, a platinum sheet was used as the counter electrode, a Hg/HgO electrode was used as the reference electrode, and 6 M KOH was used as the electrolyte, and the experiments were carried out on a CHI660 electrochemical workstation. The charge and discharge voltage range is 0-0.5V, the test temperature is room temperature, and the charge and discharge test is set to 2000 cycles. The initial discharge capacity is 1232 F·g ^-1 , and when the current density is 20A·g ^-1 , after 2000 cycle experiments After that, the capacitance of the Ln(s)-Co composite remained well, which was 88.5% of the initial capacitance (the experimental results are shown in Figure 5).

Example 1

The preparation method of Ln(s)-Co composite is implemented in the following steps:

Step 1: 0.2g of Co(NO ₃ ) ₂ ·6H ₂ O, 0.250 g of Ce(NO ₃ ) ₃ ·6H ₂ O, 0.3 g of 2,5-Pda and 11.0 g of H ₂ O were added to the polymer PTFE-lined stainless steel reactor. Stir at room temperature for 3 h, then seal the reaction vessel, transfer to a preheated oven at 180° C., and keep the temperature at 180° C. for 55 h. Cool the oven to room temperature naturally, rinse the solid product with deionized water (100mL) for 3 times and ultrasonically clean it, then filter to obtain purple-red needle-like crystals, and dry under natural environmental conditions to obtain the Ln(s)-Co-MOF material .

Step 2: Using the Ln(s)-Co-MOF material as a precursor, in a nitrogen atmosphere, in a vacuum tube furnace, at a heating rate of 3°C·min ^-1 from the built-in temperature to 750°C, at this temperature The samples were collected for 2 h, and the Ln(s)-Co complex was obtained.

Step 3: The application of the above-mentioned Ln(s)-Co composite in supercapacitors is implemented as follows: the electrode active material Ln(s)-Co composite, conductive acetylene black and polyvinylidene fluoride (PVDF) Mix at a ratio of 7:2:1, and then add an appropriate amount of solvent N-methylpyrrolidone (NMP). Grind the mixture well to form a homogeneous paste. The paste slurry was then coated on the nickel foam, and the nickel foam coated with the active material was dried in a vacuum (0.1 MPa) oven at 80 °C for 12 h. After cooling to room temperature, the nickel foam coated with the active material was taken out of the oven. The nickel foam coated with the active material is cut into 1*2cm ² sample pieces, and then the weight of the electrode is accurately weighed using a ten-thousandth balance.

Step 4: Using a platinum sheet as a counter electrode, a Hg/HgO electrode as a reference electrode, and 6 M KOH as an electrolyte, conduct electrochemical performance tests on a CHI660 electrochemical workstation.

Example 2

The preparation method of Ln(s)-Co composite is implemented in the following steps:

Step 1: Add 0.2g of Co(NO ₃ ) ₂ ·6H ₂ O, 0.250g of Ce(NO ₃ ) ₃ ·6H ₂ O, 0.3 g of 2,5-Pda and 11.0g of H ₂ O to the polymer PTFE-lined stainless steel reactor. Stir at room temperature for 3 h, then seal the reaction vessel, transfer to a preheated oven at 180° C., and keep the temperature at 180° C. for 55 h. Cool the oven to room temperature naturally, rinse the solid product with deionized water (100mL) for 3 times and ultrasonically clean it, then filter to obtain purple-red needle-like crystals, and dry under natural environmental conditions to obtain the Ln(s)-Co-MOF material .

Step 2: Using the Ln(s)-Co-MOF material as a precursor, in a nitrogen atmosphere, in a vacuum tube furnace, at a heating rate of 3°C·min ^-1 from the built-in temperature to 800°C, at this temperature The samples were collected for 1.5 h, and the Ln(s)-Co complex was obtained.

Step 3: The application of the above-mentioned Ln(s)-Co composite in supercapacitors is implemented as follows: the electrode active material Ln(s)-Co composite, conductive acetylene black and polyvinylidene fluoride (PVDF) Mix at a ratio of 7:2:1, and then add an appropriate amount of solvent N-methylpyrrolidone (NMP). Grind the mixture well to form a homogeneous paste. The paste slurry was then coated on the nickel foam, and the nickel foam coated with the active material was dried in a vacuum (0.1 MPa) oven at 80 °C for 12 h. After cooling to room temperature, the nickel foam coated with the active material was taken out of the oven. The nickel foam coated with the active material is cut into 1*2cm ² sample pieces, and then the weight of the electrode is accurately weighed using a ten-thousandth balance.

Step 4: Using a platinum sheet as the counter electrode, a Hg/HgO electrode as the reference electrode, and 6M KOH as the electrolyte, conduct electrochemical performance tests on a CHI660 electrochemical workstation.

Example 3

The preparation method of Ln(s)-Co composite is implemented in the following steps:

Step 1: 0.2 g of Co(NO ₃ ) ₂ ·6H ₂ O, 0.3 g of Pr(NO ₃ ) ₃ ·6H ₂ O, 0.350 g of 2,5-Pda and 12.0 g of H ₂ O were added to the polymer PTFE-lined stainless steel reactor. Stir at room temperature for 3h, then seal the reaction vessel, transfer to a preheated oven at 180°C, and keep the temperature at 180°C for 60h. Cool the oven to room temperature naturally, rinse the solid product with deionized water (100mL) for 3 times and ultrasonically clean it, then filter to obtain purple-red needle-like crystals, and dry under natural environmental conditions to obtain the Ln(s)-Co-MOF material .

Step 2: Using the Ln(s)-Co-MOF material as a precursor, in a nitrogen atmosphere, in a vacuum tube furnace, at a heating rate of 3°C·min ^-1 from the built-in temperature to 800°C, at this temperature Keep the temperature for 2h, collect the samples, and obtain the Ln(s)-Co complex.

Step 3: The application of the above-mentioned Ln(s)-Co composite in supercapacitors is carried out as follows: the electrode active material Ln(s)-Co composite, conductive acetylene black and polyvinylidene fluoride (PVDF) are Mix at a ratio of 7:2:1, and then add an appropriate amount of solvent N-methylpyrrolidone (NMP). Grind the mixture well to form a homogeneous paste. The paste slurry was then coated on the nickel foam, and the nickel foam coated with the active material was dried in a vacuum (0.1 MPa) oven at 80 °C for 12 h. After cooling to room temperature, the nickel foam coated with the active material was taken out of the oven. The nickel foam coated with the active material is cut into 1*2 cm2 sample pieces, and then the weight of the electrode is accurately weighed using a ten-thousandth balance.

Step 4: Using a platinum sheet as a counter electrode, a Hg/HgO electrode as a reference electrode, and 6 M KOH as an electrolyte, conduct electrochemical performance tests on a CHI660 electrochemical workstation.

The test result shows that when the current density is 2A·g ^-1 , it shows a specific capacity of 1440 F·g ^-1 . After 2000 cycles at a current density of 20 A g ^-1 , the capacitance is more than 88.5% of the initial capacitance.

For those skilled in the art, various other corresponding changes and deformations can be made according to the technical concept of the present invention, and all these changes and deformations should belong to the protection scope of the claims of the present invention.

Claims (10)

1. a preparation method of supercapacitor electrode material Ln (s)-Co composite, it is characterized in that, implement as follows: (1) Put pyridine 2,5-dicarboxylic acid, rare earth nitrate, and cobalt nitrate in a reaction kettle, add deionized water, and stir at room temperature; (2) Transfer the product obtained in step (1) to an oven for constant temperature treatment; (3) Naturally cool the product obtained in step (2) to room temperature, rinse with deionized water and ultrasonically clean, and then filter to obtain purple-red needle-like crystals; dry under natural conditions to obtain Ln(s)-Co-MOF material ; (4) Calcining the product obtained in step (3) under the protection of an inert gas to obtain the target product Ln(s)-Co composite, which is an electrode material for a supercapacitor. 2. according to the preparation method of the described supercapacitor electrode material Ln (s)-Co compound of claim 1, it is characterized in that: described rare earth nitrate is cerium nitrate, praseodymium nitrate, neodymium nitrate, samarium nitrate, europium nitrate, nitric acid Gadolinium or Holmium Nitrate. 3. The preparation method of the supercapacitor electrode material Ln(s)-Co composite according to claim 2, characterized in that: in step (1), the pyridine 2,5-dicarboxylic acid, rare earth nitrate, nitric acid The mass ratio of cobalt and deionized water is as follows: 0.3-0.4:0.25-0.3:0.15-0.2:10-12. 4. The method for preparing the supercapacitor electrode material Ln(s)-Co composite according to claim 3, characterized in that: in step (2), the preheating temperature of the oven is 180°C to 190°C; the constant temperature is 180℃～190℃; constant temperature time is 55～60h. 5. The method for preparing the supercapacitor electrode material Ln(s)-Co composite according to claim 4, characterized in that in step (3), the product obtained in step (2) is washed 2 to 3 times with deionized water , drying under natural conditions for 10 to 12 hours to obtain the preparation method of Ln(s)-Co-MOF. 6. The preparation method of the supercapacitor electrode material Ln(s)-Co composite according to claim 5, characterized in that: in step (4), the calcination temperature is 750°C-800°C; the constant temperature time is 1.5- 2h. 7. a kind of application of the preparation method gained product of supercapacitor electrode material Ln(s)-Co composite as claimed in claim 1～6 in the application of supercapacitor electrode, it is characterized in that, implement as follows: Ln(s) )-Co composite, polyvinylidene fluoride, conductive acetylene black and N-methylpyrrolidone are fully ground to obtain a supercapacitor electrode slurry; the supercapacitor electrode slurry is evenly spread on the foamed nickel to obtain an electrode sheet, and then After drying, cooling, and slicing, the test electrode of the supercapacitor is obtained. 8. according to the application of the preparation method gained product of supercapacitor electrode material Ln(s)-Co composite of claim 7 in the application of supercapacitor electrode, it is characterized in that: described Ln(s)-Co composite, conductive acetylene The mass ratio of black and polyvinylidene fluoride is: 5-8:1-3:0.5-2. 9. According to the application of the product obtained in the preparation method of the supercapacitor electrode material Ln(s)-Co composite of claim 8 in supercapacitor electrodes, it is characterized in that: the electrode sheet is placed in a 0.1Mpa vacuum drying oven at 80 to 110 Dry at ℃ for 10-13 hours. 10. according to the application of the product obtained in the preparation method of the supercapacitor electrode material Ln(s)-Co composite of claim 9 in supercapacitor electrodes, it is characterized in that: in the supercapacitor test, the electrolyte used is a concentration of 3 ~6M KOH solution.

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