Preparation method and application of a vanadium pentoxide composite carbon material with core-shell structure

Abstract

The present application relates to the technical field of supercapacitor, in particular, especially relates to a preparation method of core-shell structure vanadium pentoxide composite carbon material and application thereof. The present application takes vanadium-based alcohol salt as a precursor, grows small-size metal organic framework (Zn-MI) particles on the surface, and then realizes the preparation of core-shell structure V2O5 composite carbon material through the control of carbonization process. The metal alcohol salt can provide the growth site of Zn-MI due to the strong electronegativity of oxygen atom, and ensure the small particle Zn-MI to grow on the surface of the sphere; and in the carbonization process, Zn-MI can inhibit the shrinkage of alcohol salt shell, and then realize the preparation of core-shell V2O5. The core-shell structure V2O5 composite carbon material prepared by the present application can provide a large number of active sites through the core-shell structure, slow down the expansion of the electrode charge-discharge structure, and the internal cavity can be used as a place for storing electrolyte to shorten the transmission distance of ions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of supercapacitors, in particular, and more particularly, to a preparation method of a core-shell structure vanadium pentoxide composite carbon material and application thereof. BACKGROUND

[0002] With the rapid development of high energy consumption industries, traditional batteries have been unable to meet people's needs. Supercapacitors are a new type of energy storage device between traditional capacitors and rechargeable batteries, which have excellent electrochemical performance and cycle stability. As a kind of electrochemical energy storage device with excellent electrochemical properties, low cost and environmental friendliness, supercapacitors have attracted more and more attention from scientists and industrial researchers. V2O5 is successfully used as a supercapacitor electrode due to its large energy storage capacity, environmental friendliness and other characteristics. Combining V2O5 with carbon materials can also improve the conductivity of the composite material and further improve the electrochemical properties. The structure design of V2O5 can further improve its electrochemical performance. The core-shell structure can provide a large number of active sites and slow down the expansion of the electrode charge-discharge structure, while the internal cavity can serve as a place to store electrolyte and shorten the ion transmission distance. However, the preparation of core-shell structure V2O5 is relatively complex and difficult. For example, Zeiger et al. (J. Mater. Chem. A, 2016, 4, 18899) synthesized hybrid particles composed of porous carbon and V2O5 in situ by a two-step method. These particles exhibit a V2O5-C@C core-shell structure with a nano-V2O5 core, which is completely accessible to electrolyte ions and is interconnected by highly conductive carbon. This material exhibits excellent specific capacity and cycle stability. However, this method is complex and costly, which is not conducive to practical application. In addition, V2O5 can be improved by compounding with carbon materials due to its poor conductivity. For example, the commonly used carbon-coated V2O5 is a carbon material with a uniform structure coated on the surface of V2O5. However, although the conductivity is improved, the carbon material has charge shielding ability, so this uniform carbon material combined with V2O5 usually lacks active sites and ion transmission channels, which also brings new problems. SUMMARY

[0003] In view of the problems existing in the prior art, the present application provides a preparation method of a core-shell structure vanadium pentoxide composite carbon material and application thereof in supercapacitors. The preparation method is simple, easy to control and low in cost, and the prepared material has good electrochemical performance.

[0004] The present application takes vanadium-based alkoxide as a precursor, grows small-sized metal organic framework (Zn-MI) particles on the surface, and then realizes the preparation of core-shell structure V2O5 composite carbon material through the control of the carbonization process. The metal alkoxide can provide the growth site of Zn-MI due to the strong electronegativity of oxygen atom, so as to ensure the growth of small particle Zn-MI on the surface of the sphere; and in the carbonization process, Zn-MI can inhibit the shrinkage of the alkoxide shell, thereby realizing the preparation of core-shell V2O5.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The present application provides a kind of core-shell structure V2O5 composite carbon material preparation method, the method comprises the following steps:

[0007] (1) NH4VO3 is dissolved in the mixed solvent of propylene glycol and glycerol, and is reacted at 180-200 DEG C for 6-9h, is filtered, washed, and dried to obtain vanadium alkoxide precursor V-ako;

[0008] (2) vanadium alkoxide precursor V-ako and Zn (NO3) 2·6H2O are dispersed in methanol, ultrasonic, to obtain solution A, 2-methyl imidazole is dissolved in methanol to obtain solution B, solution B is slowly poured into solution A, the mixed solution is stirred, and then it is extracted, washed, and dried to obtain V-ako@ZIF-8 precursor;

[0009] (3) V-ako@ZIF-8 precursor is subjected to two-stage high-temperature annealing under argon environment to obtain core-shell structure V2O5 composite carbon material (V2O5-C@C).

[0010] Further, in step (1), the volume ratio of glycerol to propylene glycol in the mixed solvent of propylene glycol and glycerol is 2:1 to 8:1.

[0011] Further, in step (1), 0.1-0.65g NH4VO3 is dissolved in 45ml of mixed solvent.

[0012] Further, in step (1), the washing is carried out with water and ethanol; the drying temperature is 50-70 DEG C, and the drying time is 5-8h.

[0013] Further, in step (2), the ultrasonic time is 20-30min.

[0014] Further, in step (2), the concentration of vanadium alcoholate precursor in solution A is 0.0066-0.027 g / ml, and the concentration of Zn(NO3)2·6H2O is 0.013-0.033 g / ml; the concentration of 2-methylimidazole in solution B is 0.26-0.46 g / ml; and the stirring time is 1-3 h.

[0015] Further, in step (3), in the two-stage high-temperature annealing, the first-stage annealing has a heating rate of 5-10 ℃ / min, an annealing temperature of 600-800 ℃, and an annealing time of 1-3 h; and the second-stage annealing has a heating rate of 20-30 ℃ / min, an annealing temperature of 910-1000 ℃, and an annealing time of 1-3 h.

[0016] In another aspect, the application provides a use of the core-shell V2O5 composite carbon material prepared by the above preparation method in supercapacitors.

[0017] The principle of the application is as follows:

[0018] The metal alcoholate can provide a growth site of Zn-MI due to the strong electronegativity of oxygen atoms, thereby ensuring the growth of small Zn-MI particles on the surface of the sphere. In the carbonization and oxidation process, the Zn-MI can inhibit the shrinkage of the alcoholate shell, thereby realizing the preparation of the core-shell V2O5. However, the large-size Zn-MI particles cannot grow on the surface of the alcoholate, and thus cannot control the core-shell structure.

[0019] The application has the following beneficial effects:

[0020] 1) The preparation method is simple and controllable, and has low cost.

[0021] 2) The core-shell structure V2O5-C@C prepared by the application can provide a large number of active sites, slow down the expansion of the electrode charge-discharge structure, and the internal cavity can be used as a place for storing electrolyte to shorten the ion transmission distance.

[0022] 3) The carbon particles grown on the surface of the V2O5 composite carbon material can be used as protrusions to increase the contact with the electrolyte and provide more active sites, and the gap between the particles can be used as a transmission channel for the electrolyte, thereby improving the electrochemical performance of the material.

[0023] 4) The V2O5 composite carbon material prepared by the application has good electrical conductivity and high specific capacitance and rate performance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 FIG. 2 is a SEM image of the V2O5 composite carbon material prepared in Example 1.

[0025] Figure 2Rate capability graph of V2O5 composite carbon material prepared for Example 1;

[0026] Figure 3 Rate capability graph of V2O5 composite carbon material prepared for Example 2;

[0027] Figure 4 SEM graph of V2O5-C prepared for Comparative Example 1;

[0028] Figure 5 Rate capability graph of V2O5-C prepared for Comparative Example 1. DETAILED DESCRIPTION

[0029] The following examples can make the ordinary skilled in the art more fully understand the present application, but in no way limit the present application.

[0030] Unless otherwise specified, the materials used in the examples of the present application can be obtained by commercial channels or prepared according to conventional methods well known to those skilled in the art.

[0031] The specific embodiments of the present application are further illustrated in conjunction with the accompanying drawings and technical solutions.

[0032] Example 1

[0033] (1) 0.1 g of NH4VO3 was dissolved in a mixed solvent of 30 ml of glycerol and 15 ml of propylene glycol, stirred at room temperature for 30 min to make the solute fully dissolved, transferred into a reaction kettle, reacted at 180℃ for 6 h, and then the reaction liquid was filtered to obtain a reactant, which was washed several times with water and ethanol, and dried in an oven at 50℃ for 8 h to obtain a spherical product vanadyl salt (V-ako) ;

[0034] (2) 0.1 g of V-ako and 0.2 g of Zn(NO3)2·6H2O were dispersed in 15 ml of methanol, ultrasonically treated for 20 min to form solution A, 3.9 g of 2-methylimidazole was dissolved in 15 ml of methanol to form solution B, solution B was slowly poured into solution A, the mixed solution was stirred for 1 h, and then it was subjected to suction filtration, washing and drying to obtain V-ako@ZIF-8 precursor;

[0035] (3) 0.15 g of V-ako@ZIF-8 was subjected to two-stage high-temperature annealing under argon environment, the first-stage annealing had a heating rate of 5℃ / min, an annealing temperature of 600℃, and an annealing time of 1 h, the second-stage annealing had a heating rate of 20℃ / min, an annealing temperature of 910℃, and an annealing time of 1 h, to obtain V2O5-C@C.

[0036] The specific embodiments of the present application are further illustrated in conjunction with the accompanying drawings and technical solutions. -1 The specific embodiments of the present application are further illustrated in conjunction with the accompanying drawings and technical solutions. -1Unit, the magnification is 68%.

[0037] Example 2

[0038] (1) 0.65 g of NH4VO3 was dissolved in a mixed solvent of 35 ml of glycerol and 10 ml of propylene glycol, stirred at room temperature for 40 min to fully dissolve the solute, and then transferred to a reactor. After reacting at 200°C for 9 h, the reaction liquid was filtered to obtain the reactant, washed several times with water and ethanol, and dried in an oven at 70°C for 5 h to obtain a spherical product, vanadium alkoxide (V-ako);

[0039] (2) 0.3 g of V-ako and 0.5 g of Zn(NO3)2·6H2O were dispersed in 15 ml of methanol and ultrasonically treated for 30 min to form solution A. Then, 6.9 g of 2-methylimidazole was dissolved in 15 ml of methanol to form solution B. Solution B was slowly poured into solution A. The mixed solution was stirred for 3 h and then filtered, washed, and dried to obtain the V-ako@ZIF-8 precursor.

[0040] (3) 0.5 g of V-ako@ZIF-8 was subjected to two high-temperature annealing stages in an argon environment. The first annealing stage had a heating rate of 10°C / min, an annealing temperature of 800°C, and an annealing time of 2 h. The second annealing stage had a heating rate of 30°C / min, an annealing temperature of 1000°C, and an annealing time of 1 h to obtain V2O5-C@C.

[0041] The compound is in 1Ag -1 The specific capacitance is 508F / g. -1 Under the unit, the magnification is 63.2%.

[0042] Example 3

[0043] (1) 0.35 g of NH4VO3 was dissolved in a mixed solvent of 35 ml of glycerol and 10 ml of propylene glycol, stirred at room temperature for 30 min to fully dissolve the solute, and then transferred to a reactor. After reacting at 200°C for 9 h, the reaction liquid was filtered to obtain the reactant, washed several times with water and ethanol, and dried in an oven at 70°C for 5 h to obtain a spherical product, vanadium alkoxide (V-ako);

[0044] (2) 0.4 g of V-ako and 0.3 g of Zn(NO3)2·6H2O were dispersed in 15 ml of methanol and ultrasonically treated for 30 min to form solution A. Then, 5.9 g of 2-methylimidazole was dissolved in 15 ml of methanol to form solution B. Solution B was slowly poured into solution A. The mixed solution was stirred for 2 h and then filtered, washed, and dried to obtain the V-ako@ZIF-8 precursor.

[0045] (3) 0.4 g of V-ako@ZIF-8 was subjected to two-stage high-temperature annealing under an argon atmosphere, the first-stage annealing had a heating rate of 8°C / min, an annealing temperature of 700°C, and an annealing time of 3 h, and the second-stage annealing had a heating rate of 20°C / min, an annealing temperature of 950°C, and an annealing time of 2 h, to obtain V2O5-C@C.

[0046] The specific capacitance of the compound was 454 F / g at 1 Ag -1 The specific capacitance of the compound was 454 F / g at 1 Ag -1 The specific capacitance of the compound was 454 F / g at 1 Ag

[0047] Example 4

[0048] (1) 0.65 g of NH4VO3 was dissolved in 35 ml of a mixed solvent of glycerol and 10 ml of propylene glycol, stirred at room temperature for 40 min to fully dissolve the solute, and then transferred into a reaction kettle. After reaction at 200°C for 9 h, the reaction liquid was filtered to obtain a reactant, which was washed several times with water and ethanol, and dried in an oven at 70°C for 5 h to obtain a spherical product, vanadyl alcohol salt (V-ako);

[0049] (2) 0.3 g of V-ako and 0.5 g of Zn(NO3)2·6H2O were dispersed in 15 ml of methanol, and ultrasonic treatment was performed for 30 min to form solution A. Then, 4.9 g of 2-methylimidazole was dissolved in 15 ml of methanol to form solution B. Solution B was slowly poured into solution A, and the mixed solution was stirred for 2 h, and then subjected to suction filtration, washing, and drying to obtain a V-ako@ZIF-8 precursor;

[0050] (3) 0.5 g of V-ako@ZIF-8 was subjected to two-stage high-temperature annealing under an argon atmosphere, the first-stage annealing had a heating rate of 5°C / min, an annealing temperature of 700°C, and an annealing time of 1 h, and the second-stage annealing had a heating rate of 25°C / min, an annealing temperature of 950°C, and an annealing time of 2 h, to obtain V2O5-C@C.

[0051] The specific capacitance of the compound was 454 F / g at 1 Ag -1 The specific capacitance of the compound was 454 F / g at 1 Ag -1 The specific capacitance of the compound was 454 F / g at 1 Ag

[0052] Example 5

[0053] (1) 0.55 g of NH4VO3 was dissolved in 40 ml of a mixed solvent of glycerol and 5 ml of propylene glycol, stirred at room temperature for 30 min to fully dissolve the solute, and then transferred into a reaction kettle. After reaction at 180°C for 9 h, the reaction liquid was filtered to obtain a reactant, which was washed several times with water and ethanol, and dried in an oven at 70°C for 5 h to obtain a spherical product, vanadyl alcohol salt (V-ako);

[0054] (2) 0.3 g V-ako was dispersed with 0.5 g Zn(NO3)2·6H2O in 15 ml of methanol, ultrasonic treatment for 30 min to form solution A, then 6.3 g of 2-methylimidazole was dissolved in 15 ml of methanol to form solution B, solution B was slowly poured into solution A, the mixed solution was stirred for 2 h, and then it was subjected to suction filtration, washing and drying to obtain V-ako@ZIF-8 precursor;

[0055] (3) 0.5 g of V-ako@ZIF-8 was subjected to two-stage high-temperature annealing under argon environment, the first-stage annealing had a heating rate of 5 ℃ / min, an annealing temperature of 800 ℃, and an annealing time of 1 h, the second-stage annealing had a heating rate of 20 ℃ / min, an annealing temperature of 980 ℃, and an annealing time of 3 h, to obtain V2O5-C@C.

[0056] The specific capacitance of the compound was 480 F / g under a unit of 1 A g -1 The rate was 67.2% under a unit of 20 A g -1

[0057] Example 6

[0058] (1) 0.35 g of NH4VO3 was dissolved in 35 ml of a mixed solvent of glycerol and 10 ml of propylene glycol, stirred at room temperature for 40 min to make the solute fully dissolved, and then transferred into a reaction kettle, reacted at 190 ℃ for 9 h, and then the reaction liquid was filtered to obtain a reactant, which was washed with water and ethanol several times, and dried in an oven at 70 ℃ for 5 h to obtain a spherical product vanadyl salt (V-ako);

[0059] (2) 0.3 g of V-ako was dispersed with 0.5 g of Zn(NO3)2·6H2O in 15 ml of methanol, ultrasonic treatment for 30 min to form solution A, then 3.9 g of 2-methylimidazole was dissolved in 15 ml of methanol to form solution B, solution B was slowly poured into solution A, the mixed solution was stirred for 3 h, and then it was subjected to suction filtration, washing and drying to obtain V-ako@ZIF-8 precursor;

[0060] (3) 0.3 g of V-ako@ZIF-8 was subjected to two-stage high-temperature annealing under argon environment, the first-stage annealing had a heating rate of 5 ℃ / min, an annealing temperature of 600 ℃, and an annealing time of 3 h, the second-stage annealing had a heating rate of 25 ℃ / min, an annealing temperature of 910 ℃, and an annealing time of 3 h, to obtain V2O5-C@C.

[0061] The specific capacitance of the compound was 440 F / g under a unit of 1 A g -1 The rate was 66.5% under a unit of 20 A g -1 ​​

[0062] Example 7

[0063] (1) 0.3 g of NH4VO3 was dissolved in 35 ml of a mixed solvent of glycerol and 10 ml of propylene glycol, stirred at room temperature for 30 min to fully dissolve the solute, transferred into a reaction kettle, and reacted at 200°C for 6 h. The reaction solution was filtered to obtain a reactant, which was washed several times with water and ethanol, and dried in an oven at 60°C for 5 h to obtain spherical product vanadyl alcohol salt (V-ako);

[0064] (2) 0.3 g of V-ako and 0.5 g of Zn(NO3)2·6H2O were dispersed in 15 ml of methanol, ultrasonically treated for 30 min to form solution A, then 5.9 g of 2-methylimidazole was dissolved in 15 ml of methanol to form solution B, solution B was slowly poured into solution A, the mixed solution was stirred for 1 h, and then it was filtered, washed and dried to obtain V-ako@ZIF-8 precursor;

[0065] (3) 0.5 g of V-ako@ZIF-8 was subjected to two-stage high-temperature annealing under argon environment, the first-stage annealing had a heating rate of 10°C / min, an annealing temperature of 650°C, and an annealing time of 3 h, the second-stage annealing had a heating rate of 20°C / min, an annealing temperature of 910°C, and an annealing time of 1 h, and V2O5-C@C was obtained.

[0066] The specific capacitance of the compound was 380 F / g under 1 Ag -1 unit, and the rate was 61.2% under 20 Ag -1 unit.

[0067] Comparative Example 1

[0068] (1) 0.1 g of NH4VO3 was dissolved in 30 ml of a mixed solvent of glycerol and 15 ml of propylene glycol, stirred at room temperature for 30 min to fully dissolve the solute, transferred into a reaction kettle, and reacted at 180°C for 6 h. The reaction solution was filtered to obtain a reactant, which was washed several times with water and ethanol, and dried in an oven at 50°C for 8 h to obtain spherical product vanadyl alcohol salt (V-ako);

[0069] (2) 0.15 g of V-ako was subjected to two-stage high-temperature annealing under argon environment, the first-stage annealing had a heating rate of 5°C / min, an annealing temperature of 600°C, and an annealing time of 1 h, the second-stage annealing had a heating rate of 20°C / min, an annealing temperature of 910°C, and an annealing time of 1 h, and broken structure V2O5-C was obtained.

[0070] The specific capacitance of the compound was 150 F / g under 1 Ag -1 unit, and the rate was 45.2% under 20 Ag -1 unit.

[0071] Comparative Example 1, compared with Example 1, demonstrates that without ZIF-8 coating, no core-shell structure V2O5-C@C is formed after annealing, and the rate and specific capacitance of the formed product are not ideal.

[0072] The above examples only express the embodiments of the present application, but cannot be understood as limiting the scope of the patent of the present application. It should be pointed out that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application.

Claims

1. A method for preparing a core-shell structured V2O5 composite carbon material, characterized by: The method comprises the following steps: (1) dissolving NH4VO3 in a mixed solvent of propylene glycol and glycerol, reacting at 180-200 ℃ for 6-9 h, filtering, washing, and drying to obtain spherical vanadyl salt precursor V-ako; (2) dispersing the spherical vanadyl salt precursor V-ako and Zn(NO3)2·6H2O in methanol, ultrasonicating to obtain solution A, dissolving 2-methylimidazole in methanol to obtain solution B, slowly pouring solution B into solution A, stirring the mixed solution, and then performing suction filtration, washing, and drying to obtain V-ako@ZIF-8 precursor; (3) performing two-stage high-temperature annealing on the V-ako@ZIF-8 precursor in an argon environment to obtain core-shell structure V2O5 composite carbon material.

2. The preparation method of the core-shell structure V2O5 composite carbon material according to claim 1, characterized in that: In step (1), the volume ratio of glycerol to propylene glycol in the mixed solvent of propylene glycol and glycerol is 2:1-8:

1.

3. The preparation method of the core-shell structure V2O5 composite carbon material according to claim 1, characterized in that: In step (1), 0.1-0.65 g of NH4VO3 is dissolved in 45 ml of mixed solvent.

4. The method for preparing the core-shell structure V2O5 composite carbon material according to claim 1, characterized in that: In step (1), the washing is performed using water and ethanol; The drying temperature is 50-70 ℃, and the drying time is 5-8 h.

5. The preparation method of the core-shell structure V2O5 composite carbon material according to claim 1, characterized in that: In step (2), the ultrasonicating time is 20-30 min.

6. The preparation method of the core-shell structure V2O5 composite carbon material according to claim 1, characterized in that: In step (2), in solution A, the concentration of the spherical vanadyl salt precursor is 0.0066-0.027 g / ml, and the concentration of Zn(NO3)2·6H2O is 0.013-0.033 g / ml; In solution B, the concentration of 2-methylimidazole is 0.26-0.46 g / ml; The stirring time is 1-3 h.

7. The preparation method of the core-shell structure V2O5 composite carbon material according to claim 1, characterized in that: In step (3), in the two-stage high-temperature annealing, the first-stage annealing has a heating rate of 5-10 ℃ / min, an annealing temperature of 600-800 ℃, and an annealing time of 1-3 h, and the second-stage annealing has a heating rate of 20-30 ℃ / min, an annealing temperature of 910-1000 ℃, and an annealing time of 1-3 h.

8. Use of the core-shell structure V2O5 composite carbon material prepared by the preparation method of any one of claims 1-7 in supercapacitors.

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