CN114914423B - Composite material of zinc vanadate coated carbon microsphere, and preparation method and application thereof - Google Patents

Abstract

The invention provides a composite material of zinc vanadate coated carbon microspheres, which structurally comprises carbon microspheres and zinc vanadate nanosheets, wherein the carbon microspheres are coated by the zinc vanadate nanosheets; a method for preparing a composite material of zinc vanadate coated carbon microspheres, comprising the following steps: 1. preparing carbon microspheres by a hydrothermal method; 2. coating the carbon microspheres by zinc vanadate nanosheets by a hydrothermal method and a heat treatment method; the composite material of the zinc vanadate coated carbon microsphere is used as a positive electrode material of a water-based zinc ion battery. The composite material of the zinc vanadate coated carbon microsphere prepared by the invention can effectively improve the electrochemical performance of a water system zinc ion battery.

Description

A kind of composite material of zinc vanadate coated carbon microspheres and its preparation method and application

technical field

The invention relates to a composite material of zinc vanadate-coated carbon microspheres, a preparation method and application thereof, and belongs to the technical field of new energy materials.

Background technique

With the continuous development of society and the advancement of technology, electronic products are becoming more and more common, and energy storage has become crucial; traditional lithium-ion batteries cannot be mass-produced and applied due to their inherent insecurity and expensive processing costs To meet the needs of the energy storage market; in recent years, water-based zinc-ion batteries have become popular candidates for lithium-ion batteries due to their environmental protection, high safety, and large-scale development.

So far, vanadium oxides and their composites, manganese oxides and their composites, Prussian blue analogues, and bimetallic compounds are the most commonly used cathode materials for aqueous zinc-ion batteries; among them, vanadium oxide is due to its inherent layered or tunnel The special structure of vanadium makes ion diffusion efficient and feasible, and has become a commonly used material in aqueous zinc-ion batteries; however, the poor rate performance and poor cycle stability of pure vanadium oxides cannot be ignored, because pure vanadium oxides are conductive. Poor performance, which is not conducive to electron transport, hinders electrochemical reactions, and thus affects its rate capacity; in addition, volume expansion is prone to occur during cycling, and the internal structure will collapse rapidly, resulting in rapid capacity decay and poor cycle stability.

Due to its unique structure and superior physical and chemical properties, vanadium-based double metal oxides (such as Fe ₂ VO ₄ , CaV ₂ O ₇ , etc.) In one field, zinc vanadate is very suitable as the positive electrode of aqueous zinc-ion batteries due to the zinc-rich characteristics and multi-electron transport properties of vanadium, and the release of Zn ²⁺ during the first charging process will bring additional metal vacancies to improve the capacity. materials; but so far, zinc vanadate materials as cathode materials for aqueous zinc-ion batteries generally have low capacity and low safety in the preparation process. It can be seen that under the premise of ensuring the discharge capacity, it is necessary to study a morphology A controllable, easy-to-operate, and highly safe preparation method for zinc vanadate is very meaningful.

Contents of the invention

The present invention proposes a composite material of zinc vanadate-coated carbon microspheres and its preparation method and application. The purpose of the invention is to prepare a positive electrode material that can be applied to an aqueous zinc-ion battery.

Technical solution of the present invention: a composite material of zinc vanadate coated carbon microspheres, the structure of which includes carbon microspheres and zinc vanadate (Zn3V3O8) nanosheets, zinc vanadate (Zn3V3O8) nanosheets coated carbon microspheres .

Further, the particle size range of the carbon microspheres is preferably 1 μm-10 μm.

Further, the thickness of the zinc vanadate (Zn3V3O8) nanosheets is preferably 10nm-200nm.

A preparation method of a composite material of zinc vanadate coated carbon microspheres, the method comprising:

1. Preparation of carbon microspheres by hydrothermal method;

2. Using hydrothermal method and heat treatment method to realize the coating of zinc vanadate nanosheets on carbon microspheres.

Further, the preparation of carbon microspheres by hydrothermal method specifically includes:

1-1. Prepare glucose solution;

1-2. Add a pH adjuster and formaldehyde solution to the glucose solution, and stir fully to form a mixed solution;

1-3. Performing a hydrothermal reaction on the mixed solution to obtain a hydrothermal reaction product;

1-4. Centrifuge the hydrothermal reaction product to collect the first precipitate;

1-5. Vacuum freeze-drying the collected first precipitate to obtain carbon microspheres.

Further, the use of hydrothermal method and heat treatment method to realize the coating of zinc vanadate nanosheets on carbon microspheres specifically includes:

2-1. Pour ethylene glycol into the container;

2-2. Uniformly disperse sodium metavanadate, zinc trifluoromethanesulfonate, and polyvinylpyrrolidone into ethylene glycol to obtain a suspension;

2-3. Add the carbon microspheres prepared in step 1 to the suspension, and continue until the dispersion is uniform;

2-4. Performing a solvothermal reaction on the suspension dispersed with carbon microspheres to obtain a solvothermal reaction product;

2-5. Centrifuging the solvothermal reaction product to collect the second precipitate;

2-6. Vacuum freeze-drying the collected second precipitate;

2-7. Keeping the dried product under a nitrogen atmosphere at a temperature for a certain period of time to obtain a composite material of carbon microspheres coated with zinc vanadate nanosheets.

Further, the pH regulator is preferably sodium hydroxide and citric acid, and the pH regulator is used to adjust the pH to preferably 8; the solubility of the glucose solution is preferably 0.23mol/L-0.38mol/L The concentration of the aqueous formaldehyde solution is preferably 0.37 mol/L-0.40 mol/L; the solubility of the glucose solution is more preferably 0.38 mol/L; the concentration of the aqueous formaldehyde solution is further preferably 0.40 mol/L.

Further, the hydrothermal reaction of the mixed solution to obtain a hydrothermal reaction product is specifically: pouring the mixed solution into a polytetrafluoroethylene mold, and performing a hydrothermal reaction to obtain a hydrothermal reaction product; the conditions of the hydrothermal reaction Preferably, the reaction is at 160°C for 4h-6h; the condition of the hydrothermal reaction is further preferably at 160°C for 6h.

Further, the specific method of centrifuging the hydrothermal reaction product is: alternately centrifuging with deionized water and ethanol at a speed of 8000 r/min.

Further, the vacuum freeze-drying of the collected first precipitate specifically includes: vacuum freeze-drying of the collected first precipitate for 48 hours at a temperature of -80°C.

Further, the concentration of the ammonium metavanadate in ethylene glycol is preferably 0.10mol/L-0.15mol/L; the concentration of the zinc trifluoromethanesulfonate in ethylene glycol is preferably 0.030mol/L -0.035 mol/L; the concentration of the polyvinylpyrrolidone in ethylene glycol is preferably 1.55 g/L-1.70g/L; the concentration of the carbon microspheres in ethylene glycol is preferably 10g/L.

Further, performing solvothermal reaction on the suspension dispersed with carbon microspheres to obtain a solvothermal reaction product, specifically: pouring the suspension dispersed with carbon microspheres into a polytetrafluoroethylene mold for solvothermal reaction; The reaction condition of the solvothermal reaction is 180°C for 8h-12h; the reaction condition of the solvothermal reaction is further preferably 180°C for 12h.

Further, the specific method of centrifuging the solvothermal reaction product is: alternately centrifuging with deionized water and ethanol at 8000 r/min.

Further, the vacuum freeze-drying of the collected second precipitate is specifically: vacuum freeze-drying of the collected second precipitate for 48 hours at a temperature of -80°C.

Further, the holding temperature is preferably 400°C-600°C; the holding temperature is specifically raised from room temperature to the holding temperature at a heating rate of 5°C/min; the holding time is 6 hours; the holding temperature is further Preferably it is 600°C.

The composite material of the zinc vanadate-coated carbon microspheres is used as the positive electrode material of the aqueous zinc-ion battery.

A kind of application of the composite material of zinc vanadate coating carbon microsphere, specifically comprises as follows: the composite material of zinc vanadate nano sheet coating carbon microsphere, conductive carbon black, polyvinylidene fluoride is 7 according to mass ratio: 2:1 dispersed in N-methylpyrrolidone to form a slurry coated on Ti foil, and then placed in an oven and dried under vacuum to obtain a water-based zinc-ion battery positive electrode material.

Beneficial effects of the present invention:

The composite material of zinc vanadate-coated carbon microspheres prepared by the preparation method provided by the invention is used for the positive electrode of the aqueous zinc-ion battery, and the zinc vanadate with the ultra-thin nanosheet structure can improve the ion transmission rate and shorten the time for ion diffusion and transfer , which is conducive to the performance improvement of the electrochemical diffusion control process; in addition, the unique spherical structure of the overall composite material formed by zinc vanadate nanosheets coated with carbon microspheres has a high specific surface area, which can not only increase the contact area between the active material and the electrolyte , shorten the ion diffusion path, and can also provide more space for the volume expansion in the charging and discharging process; in general, the composite material of zinc vanadate-coated carbon microspheres prepared by the present invention can effectively improve the performance of aqueous zinc-ion batteries. electrochemical performance.

Description of drawings

Accompanying drawing 1 is the scanning electron micrograph of the composite material of ultra-thin zinc vanadate nanosheets coated with carbon microspheres prepared in Example 1 of the present invention.

Accompanying drawing 2 is the scanning electron micrograph of the composite material of ultra-thin zinc vanadate nanosheets coated with carbon microspheres prepared in Example 2 of the present invention.

Accompanying drawing 3 is the scanning electron micrograph 1 of the composite material of ultra-thin zinc vanadate nanosheets coated with carbon microspheres prepared in Example 3 of the present invention.

Accompanying drawing 4 is the scanning electron micrograph 2 of the composite material of ultra-thin zinc vanadate nanosheets coated with carbon microspheres prepared in Example 3 of the present invention.

Accompanying drawing 5 is the XRD pattern of the product prepared in Example 1 of the present invention.

Accompanying drawing 6 is the XRD spectrum of the product prepared in Example 2 of the present invention.

Accompanying drawing 7 is the XRD spectrum of the product prepared in Example 3 of the present invention.

Accompanying drawing 8 is the composite material of ultra-thin zinc vanadate nanosheets coated with carbon microspheres in Example 1 of the present invention as a positive electrode in an aqueous zinc-ion battery at the same current density for five charge-discharge test curves.

Accompanying drawing 9 is the composite material of ultra-thin zinc vanadate nanosheets coated with carbon microspheres in Example 2 of the present invention as a positive electrode in an aqueous zinc-ion battery at the same current density for five charge-discharge test curves.

Accompanying drawing 10 is the composite material of ultra-thin zinc vanadate nanosheets coated with carbon microspheres in Example 3 of the present invention as a positive electrode in an aqueous zinc-ion battery at the same current density for five charge-discharge test curves.

Figure 11 is a graph of the rate performance of the composite material of ultra-thin zinc vanadate nanosheets coated with carbon microspheres as the positive electrode in the aqueous zinc-ion battery in Examples 1-3 of the present invention.

Detailed ways

A composite material of zinc vanadate coated carbon microspheres, the structure of which comprises carbon microspheres and zinc vanadate (Zn3V3O8) nanosheets, wherein the zinc vanadate (Zn3V3O8) nanosheets coat carbon microspheres.

The particle size range of the carbon microspheres is preferably 1 μm-10 μm, more preferably 4 μm-8 μm; using carbon microspheres with uniform size as a template to load ultra-thin vanadic acid nanosheets provides a controllable shape for the composite material. Similarly, the spherical composite material is conducive to stabilizing the structure when it is used as an electrode for charge-discharge cycles, providing a buffer space for the volume change during the reaction.

The thickness of the zinc vanadate (Zn3V3O8) nanosheets is preferably 10 nm-200nm, more preferably 10 nm-100nm; the nanoscale thickness provides negligible ion diffusion and transfer time, which is beneficial to the electrochemical diffusion control process performance improvement.

A preparation method of a composite material of zinc vanadate coated carbon microspheres, the method may further comprise the steps:

1. Preparation of carbon microspheres:

1-1. Prepare a glucose solution with a concentration of 0.23mol/L -0.38mol/L in a beaker;

1-2. Add sodium hydroxide, citric acid, and formaldehyde solution with a concentration of 0.37 mol/L-0.40 mol/L, and stir well to form a mixed solution; wherein, the role of sodium hydroxide and citric acid is to adjust the pH value of the reaction system, The pH of the reaction system is preferably 8;

1-3. Pour the mixed solution into a polytetrafluoroethylene mold, and perform a hydrothermal reaction to obtain a hydrothermal reaction product. The condition of the hydrothermal reaction is 160ºC for 6 hours;

1-4. Alternately centrifuge the hydrothermal reaction product with deionized water and ethanol at 8000r/min, and collect the first precipitate;

1-5. Vacuum freeze-dry the collected first precipitate for 48 hours at a freezing temperature of -80°C to obtain carbon microspheres;

2. Preparation of zinc vanadate-coated carbon microsphere composites:

2-1. Pour ethylene glycol into the beaker;

2-2. Uniformly disperse sodium metavanadate, zinc trifluoromethanesulfonate, and polyvinylpyrrolidone into ethylene glycol to obtain a suspension;

2-3. Add the carbon microsphere material prepared in step (1) into the suspension, and keep stirring until uniformly dispersed;

2-4. Pour the suspension into a polytetrafluoroethylene mold for solvothermal reaction to obtain a solvothermal reaction product. The reaction condition of the solvothermal reaction is 180ºC for 12 hours;

2-5. The solvothermal reaction product was alternately centrifuged with deionized water and ethanol at 8000 r/min, and the second precipitate was collected;

2-6. Vacuum freeze-dry the collected second precipitate for 48 hours, and the freezing temperature is -80°C;

2-7. Put the freeze-dried product in a tube furnace, and keep it warm at 400°C-600°C under a nitrogen atmosphere. The heating rate is 5°C/min, and the holding time is 6h, and zinc vanadate nanosheet coating is obtained. A composite material of carbon microspheres; the holding temperature is further preferably 600°C.

The composite material of the zinc vanadate-coated carbon microspheres prepared in the present invention is used as the positive electrode material of the aqueous zinc-ion battery.

The specific application method of the composite material of the zinc vanadate coated carbon microspheres as the positive electrode material of the aqueous zinc ion battery includes as follows:

1. Disperse the composite material of zinc vanadate nanosheets coated carbon microspheres with conductive carbon black and polyvinylidene fluoride in N-methylpyrrolidone at a mass ratio of 7:2:1 to make a slurry and coat it on Ti foil, then placed in an oven and dried at 110°C for 12 hours under vacuum conditions, to obtain the positive electrode material of the aqueous zinc ion battery;

2. Cut the obtained aqueous zinc-ion battery cathode material into a circular electrode with a diameter of 14 mm, use platinum mesh and saturated calomel electrode as the counter electrode and reference electrode respectively, and use Whatman GF/D glass fiber filter paper as the diaphragm, and assemble into a button battery.

The assembled button cell was tested by electrochemical workstation Autolab.

The present invention utilizes a two-step hydrothermal method (hydrothermal reaction in the preparation process of carbon microspheres and solvothermal reaction in the preparation process of zinc vanadate-coated carbon microsphere composite materials) and a heat treatment method (zinc vanadate-coated carbon In the preparation process of the microsphere composite material, the annealing reaction of maintaining a certain temperature and a certain period of time under a nitrogen atmosphere) synthesizes a composite material of zinc vanadate nanosheets coated with carbon microspheres with excellent electrochemical properties; the zinc vanadate nanosheets prepared by the present invention The composite material of sheet-coated carbon microspheres is used as the positive electrode material of the water-based zinc-ion battery, and when the current density is 1 A g ^-1 , the discharge specific capacity can reach more than 300mAh g ^-1 ; the zinc vanadate prepared by the method of the present invention The composite material coated with carbon microspheres has a spherical shape, and the whole preparation process is safe and easy to operate, which provides a new method for the preparation of zinc vanadate.

The glucose is preferably biomass glucose.

In the preparation method provided by the present invention, firstly, under the condition of hydrothermal reaction, glucose is reacted in a weakly alkaline environment to generate spherical templates—carbon microspheres; ethylene glycol is used as a solvent, ammonium metavanadate is used as a vanadium source, and Zinc trifluoromethanesulfonate is used as the zinc source, polyvinylpyrrolidone is used as the surfactant, and carbon microspheres are used as the template. The zinc vanadate/carbon microsphere precursor was obtained; high-temperature heat treatment was carried out under nitrogen atmosphere in a tube furnace, and the zinc vanadate attached to the carbon microspheres was annealed into nanosheets, and the structure of the carbon microspheres also changed at high temperature. Get loose, the composite material of the zinc vanadate nano-sheet coated carbon microsphere finally obtained; The particle size of the carbon microsphere in the zinc vanadate nano-sheet coated carbon microsphere composite material prepared by the preparation method of the present invention can be distributed Between 1 μm and 10 μm, the thickness of zinc vanadate (Zn3V3O8) nanosheets can be distributed between 10 nm and 200 nm, and the thickness of most zinc vanadate (Zn3V3O8) nanosheets can be distributed between 10 nm and 100 nm.

The invention provides a positive electrode material for a water-based zinc ion battery. Zinc vanadate nanosheets are attached to the surface of carbon microspheres, which can increase the capacity while ensuring the conductivity of the zinc vanadate nanosheets coated carbon microspheres; specifically , the participation of carbon microspheres makes electronic conduction easier, based on which the overall conductivity of the composite material is improved; the sheet structure of zinc vanadate nanosheets has a large contact area with the electrolyte, and ions are easier to embed. It can provide a higher specific capacity; the zinc vanadate nanosheets are attached to the spherical template, and the composite material is spherical, so that the volume expansion during charge and discharge is more selective in direction than the planar structure, so in Prolonging the time of structural collapse and rupture during the battery cycle has strong structural stability and is of great help to the battery life; the composite material of zinc vanadate nanosheets coated with carbon microspheres is used as a water-based zinc-ion battery ( AZIBs) as cathode materials and assembled into aqueous Zn-ion batteries, exhibiting excellent electrochemical behavior.

The present invention will be further described below in conjunction with specific embodiments.

Example 1

1. Preparation of carbon microspheres:

(a) Prepare a glucose solution with a concentration of 0.23mol/L in a beaker;

(b) Add sodium hydroxide, citric acid and aqueous formaldehyde solution with a concentration of 0.37mol/L, and stir thoroughly;

(c) Pour the mixed solution into a polytetrafluoroethylene mold for hydrothermal reaction at 160ºC for 4 hours;

(d) Alternately centrifuge the hydrothermal reaction product with deionized water and ethanol at 8000r/min to collect the precipitate;

(e) Vacuum freeze-dry the collected precipitate for 48 hours at -80°C to obtain carbon microspheres;

2. Preparation of zinc vanadate-coated carbon microsphere composites:

(a) Pour ethylene glycol into the beaker;

(b) Uniformly disperse sodium metavanadate, zinc trifluoromethanesulfonate, and polyvinylpyrrolidone in ethylene glycol to obtain a suspension;

(c) Add the carbon microsphere material in step (1) into the suspension, and continue to stir vigorously until it is uniformly dispersed;

(d) Pour the suspension into a polytetrafluoroethylene mold for solvothermal reaction, and the reaction condition is 180ºC for 8 hours;

(e) Alternately centrifuge the solvothermal reaction product with deionized water and ethanol at 8000r/min to collect the precipitate;

(f) Vacuum freeze-dry the collected precipitate for 48 hours at -80°C;

(g) Put the dried product in a tube furnace, and in a nitrogen atmosphere, the holding temperature is 400°C, the heating rate is 5°C/min, and the holding time is 6h to obtain zinc vanadate nanosheet-coated carbon microspheres. composite material.

3. Preparation of zinc vanadate nanosheet-coated carbon microsphere composites as electrode materials for aqueous zinc-ion batteries:

Disperse the zinc vanadate nanosheet-coated carbon microsphere composite material prepared in step 2 with Super P (conductive carbon black) and polyvinylidene fluoride in N-methylpyrrolidone at a mass ratio of 7:2:1 The prepared slurry is coated on the Ti foil, and then placed in an oven and dried at 110° C. for 12 hours under vacuum condition to obtain the positive electrode material of the battery.

4. Test of zinc vanadate nanosheet-coated carbon microsphere composites as electrode materials for zinc-ion batteries:

Cut the positive electrode material of the battery in step 3 into a circular electrode with a diameter of 14 mm, use platinum mesh and saturated calomel electrode as the counter electrode and reference electrode respectively, and use Whatman GF/D glass fiber filter paper as the separator, and assemble it into a button type The battery, wherein the electrolyte in the button cell is a zinc trifluoromethanesulfonate solution with a concentration of 2.8~3.0mol/L, and the negative electrode is a zinc sheet; the button cell is tested by the electrochemical workstation Autolab, and the current density is 0.1A /g, the charge and discharge performance of the test is shown in Figure 8; the button battery is cycle tested by the blue battery tester CT2001A (voltage window is 0.3-1.7V), and the rate performance is shown in Example 1 of Figure 11.

Taking the ultra-thin zinc vanadate nanosheet-coated carbon microsphere composite material prepared in Example 1 as an example, it can be observed from the scanning electron microscope photo of accompanying drawing 1 that the composite material basically presents a composite material composed of zinc vanadate and carbon microspheres. The shape of the ball is closely combined; its structure can be seen from the XRD of accompanying drawing 5, the crystallinity is relatively poor, and all the characteristic peaks of Zn ₃ V ₃ O ₈ do not appear; from the charge and discharge test results of accompanying drawing 8, it can be seen that It can be seen that, as an independent electrode sheet, it is tested with the three-electrode test method, and when the current density is 1 A g ^-1 , the discharge specific capacity is 187mAh g ^-1 ; it can be seen from the rate performance diagram of Figure 11 , when used as the positive electrode active material of the aqueous zinc-ion battery, the button battery was tested with the method of two electrodes, and when the current density was 0.1, 0.2, 0.5, 1, 2, 3, 4, 5 A g ^-1 The discharge specific capacity of the battery is 247.8, 164.8, 126.5, 108.3, 90.0, 72.5, 60.0, 48.6mAh g ^-1 , and when the current density returns to the low current density (0.1A g ^-1 ), the discharge specific capacity is 133.7 mAh g ^-1 , we can see its good electrochemical performance.

Example 2

1. Preparation of carbon microspheres:

(a) Prepare a glucose solution with a concentration of 0.30mol/L in a beaker;

(b) Add sodium hydroxide, citric acid and aqueous formaldehyde solution with a concentration of 0.38 mol/L, and stir thoroughly;

(c) Pour the mixed solution into a polytetrafluoroethylene mold for hydrothermal reaction at 160ºC for 5 hours;

(d) Alternately centrifuge the hydrothermal reaction product with deionized water and ethanol at 8000r/min to collect the precipitate;

(e) Vacuum freeze-dry the collected precipitate for 48 hours at -80°C to obtain carbon microspheres;

2. Preparation of zinc vanadate-coated carbon microsphere composites:

(a) Pour ethylene glycol into the beaker;

(b) Uniformly disperse sodium metavanadate, zinc trifluoromethanesulfonate, and polyvinylpyrrolidone in ethylene glycol to obtain a suspension;

(c) Add the carbon microsphere material in step (1) into the suspension, and continue to stir vigorously until it is uniformly dispersed;

(d) Pour the suspension into a polytetrafluoroethylene mold for solvothermal reaction, and the reaction condition is 180ºC for 10 hours;

(e) Alternately centrifuge the solvothermal reaction product with deionized water and ethanol at 8000r/min to collect the precipitate;

(f) Vacuum freeze-dry the collected precipitate for 48 hours at -80°C;

(g) Put the dried product in a tube furnace, and in a nitrogen atmosphere, the holding temperature is 500°C, the heating rate is 5°C/min, and the holding time is 6h to obtain zinc vanadate nanosheet-coated carbon microspheres. composite material.

3. Preparation of zinc vanadate nanosheet-coated carbon microsphere composites as electrode materials for aqueous zinc-ion batteries:

Disperse the composite material of zinc vanadate nanosheets coated carbon microspheres prepared in step 2 with Super P and polyvinylidene fluoride in N-methylpyrrolidone at a mass ratio of 7:2:1 to make a slurry coating Clothed on Ti foil, then placed in an oven and dried at 110° C. for 12 hours under vacuum to obtain the positive electrode material of the battery.

4. Test of zinc vanadate nanosheet-coated carbon microsphere composites as electrode materials for zinc-ion batteries

Cut the positive electrode material of the battery in step 3 into a circular electrode with a diameter of 14 mm, use platinum mesh and saturated calomel electrode as the counter electrode and reference electrode respectively, and use Whatman GF/D as the separator to assemble a button cell, wherein , the electrolyte in the button cell is a zinc trifluoromethanesulfonate solution with a concentration of 2.8~3.0mol/L, and the negative electrode is a zinc sheet; the button cell is tested by the electrochemical workstation Autolab, and the current density is 0.1A g ^-1 The charging and discharging performance is tested as shown in Figure 9; the button battery is cycle tested by the blue battery tester CT2001A (voltage window is 0.3-1.7V), and the rate performance is shown in Example 2 of Figure 11.

Taking the ultra-thin zinc vanadate nanosheet-coated carbon microsphere composite material prepared in Example 2 as an example, it can be observed from the scanning electron microscope figure of accompanying drawing 2 that the composite material has basically reached the expected zinc vanadate-coated carbon microsphere composite material. The morphology of the microspheres; its structure can be seen from the XRD of the accompanying drawing 6, the crystallinity is relatively good, although there are individual instabilities in the peak position, but it basically conforms to all the Zn ₃ V ₃ O ₈ in the PDF standard card Characteristic peak; As can be seen from the charge and discharge test results of accompanying drawing 9, as an independent electrode sheet, it is tested with the test method of three electrodes, and when the current density is 1 A g ^-1 , the discharge specific capacity is 213mAhg ^{- 1} ; As can be seen from the 11 rate performance figure of accompanying drawing, when as the positive electrode active material of water system zinc ion battery, with the method for two electrodes, it is tested to coin battery, and at current density respectively 0.1,0.2,0.5,1, At 2, 3, 4, and 5 A g ^-1 , the discharge specific capacities of the full battery are 286.3, 222.6, 191.7, 173.0, 133.3, 98.3, 76.7, 59.7 mAh g ^-1 , and when the current density returns to the low current density (0.1A g ^-1 ), the discharge specific capacity reached 196.3 mAh g ^-1 , it can be seen that the cycle performance of the battery is relatively stable, and the electrochemical performance has been greatly improved compared with Example 1.

Example 3

1. Preparation of carbon microspheres:

(a) Prepare a glucose solution with a concentration of 0.38mol/L in a beaker;

(b) Add sodium hydroxide, citric acid and aqueous formaldehyde solution with a concentration of 0.40 mol/L, and stir thoroughly;

(c) Pour the mixed solution into a polytetrafluoroethylene mold for hydrothermal reaction at 160ºC for 6 hours;

(d) Alternately centrifuge the hydrothermal reaction product with deionized water and ethanol at 8000r/min to collect the precipitate;

(e) Vacuum freeze-dry the collected precipitate for 48 hours at -80°C to obtain carbon microspheres;

2. Preparation of zinc vanadate-coated carbon microsphere composites:

(a) Pour ethylene glycol into the beaker;

(b) Uniformly disperse sodium metavanadate, zinc trifluoromethanesulfonate, and polyvinylpyrrolidone in ethylene glycol to obtain a suspension;

(c) Add the carbon microsphere material in step (1) into the suspension, and continue to stir vigorously until it is uniformly dispersed;

(d) Pour the suspension into a polytetrafluoroethylene mold for solvothermal reaction at 180ºC for 12 hours;

(e) Alternately centrifuge the solvothermal reaction product with deionized water and ethanol at 8000r/min to collect the precipitate;

(f) Vacuum freeze-dry the collected precipitate for 48 hours at -80°C;

(g) Put the dried product in a tube furnace, and in a nitrogen atmosphere, the holding temperature is 600°C, the heating rate is 5°C/min, and the holding time is 6h to obtain zinc vanadate nanosheet-coated carbon microspheres. composite material.

3. Preparation of zinc vanadate nanosheet-coated carbon microsphere composites as electrode materials for aqueous zinc-ion batteries

Disperse the composite material of zinc vanadate nanosheets coated carbon microspheres prepared in step 2 with Super P and polyvinylidene fluoride in N-methylpyrrolidone at a mass ratio of 7:2:1 to make a slurry coating Clothed on Ti foil, then placed in an oven and dried at 110° C. for 12 hours under vacuum to obtain the positive electrode material of the battery.

4. Test of zinc vanadate nanosheet-coated carbon microsphere composites as electrode materials for zinc-ion batteries

Cut the positive electrode material of the battery in step 3 into a circular electrode with a diameter of 14 mm, use platinum mesh and saturated calomel electrode as the counter electrode and reference electrode respectively, and use Whatman GF/D as the separator to assemble a button cell, wherein , the electrolyte of the button cell is a zinc trifluoromethanesulfonate solution with a concentration of 2.8~3.0mol/L, and the negative electrode is a zinc sheet; the button cell is tested by the electrochemical workstation Autolab, and the current density is 0.1A g ^-1 , The charging and discharging performance is tested as shown in Figure 10; the button battery is subjected to a cycle test (voltage window is 0.3-1.7V) through the blue battery tester CT2001A, and the rate performance is shown in Example 3 of Figure 11.

Taking the ultra-thin zinc vanadate nanosheet-coated carbon microsphere composite material prepared in Example 3 as an example, it can be observed from the scanning electron microscope figure of accompanying drawing 3 that the composite material is a regular and uniform spherical shape. 4, we can see the ultra-thin zinc vanadate nanosheets on the surface of the composite material and the spherical shape provided by the carbon microspheres as a template, indicating that the material was successfully synthesized; its structure can be seen from the XRD of Figure 7 It can be seen that the crystallinity is very good, and the diffraction peaks conform to all the characteristic peaks of Zn ₃ V ₃ O ₈ ; as can be seen from the charge and discharge test results in Figure 10, as an independent electrode sheet, it is tested with the three-electrode test method , when the current density is 1 A g ^-1 , the discharge specific capacity is 275mAh g ^-1 ; it can be seen from the rate performance diagram in Figure 11 that when used as the positive electrode active material of the aqueous zinc ion battery, the two-electrode method is used to buckle When the current density is 0.1, 0.2, 0.5, 1, 2, 3, 4, 5 A g ^-1 , the discharge specific capacity of the full battery is 312.3, 278.1, 242.3, 218.0, 183.9, 147.5 , 118.9, 93.0mAh g ^-1 , and when the current density returns to the low current density (0.1A g ^-1 ), its discharge specific capacity still maintains a capacity of 257.6 mAh g ^-1 , which shows its excellent electrochemical performance.

Claims (8)

1. The composite material of the zinc vanadate coated carbon microsphere is characterized by comprising the carbon microsphere and a zinc vanadate nanosheet, wherein the carbon microsphere is coated by the zinc vanadate nanosheet;

the preparation method of the zinc vanadate coated carbon microsphere composite material comprises the following steps:

1. preparing carbon microspheres by a hydrothermal method;

2. coating the carbon microspheres by zinc vanadate nanosheets by a hydrothermal method and a heat treatment method;

the method for coating the carbon microsphere by the zinc vanadate nanosheets by using a hydrothermal method and a heat treatment method comprises the following steps:

2-1, pouring ethylene glycol into a container;

2-2, uniformly dispersing sodium metavanadate, zinc trifluoromethane sulfonate and polyvinylpyrrolidone into ethylene glycol to obtain a suspension;

2-3, adding the carbon microspheres prepared by a hydrothermal method into the suspension, and continuing until the carbon microspheres are uniformly dispersed;

2-4, carrying out solvothermal reaction on the suspension dispersed with the carbon microspheres to obtain a solvothermal reaction product;

2-5, centrifuging the solvothermal reaction product, and collecting a second precipitate;

2-6, vacuum freeze-drying the collected second precipitate;

2-7, carrying out heat preservation on the dried product for a certain time at the heat preservation temperature in the nitrogen atmosphere to obtain the zinc vanadate nanosheet coated carbon microsphere composite material.

2. The zinc vanadate coated carbon microsphere composite according to claim 1, wherein the carbon microsphere has a particle size in the range of 1 μm to 10 μm.

3. The zinc vanadate coated carbon microsphere composite according to claim 1, wherein the zinc vanadate nanosheets have a thickness of 10nm-200nm.

4. The zinc vanadate coated carbon microsphere composite material according to claim 1, wherein the carbon microsphere preparation by a hydrothermal method comprises the following steps:

1-1, preparing a glucose solution;

1-2, adding a pH value regulator and a formaldehyde aqueous solution into the glucose solution, and fully stirring to form a mixed solution;

1-3, carrying out hydrothermal reaction on the mixed solution to obtain a hydrothermal reaction product;

1-4, centrifuging the hydrothermal reaction product, and collecting to obtain a first precipitate;

1-5, performing vacuum freeze drying on the collected first precipitate to obtain the carbon microsphere.

5. The zinc vanadate coated carbon microsphere composite according to claim 4, wherein the pH regulator is sodium hydroxide and citric acid, and the pH regulator is used for regulating the pH value to 8; the solubility of the glucose solution is 0.23mol/L-0.38mol/L; the concentration of the formaldehyde aqueous solution is 0.37mol/L-0.40 mol/L;

the mixed solution is subjected to hydrothermal reaction to obtain a hydrothermal reaction product, which is specifically as follows: pouring the mixed solution into a polytetrafluoroethylene mould, and performing a hydrothermal reaction to obtain a hydrothermal reaction product; the hydrothermal reaction condition is 160 ℃ for 4-6 hours;

the specific method for centrifuging the hydrothermal reaction product comprises the following steps: alternately centrifuging with deionized water and ethanol at 8000 r/min;

the first precipitate collected is freeze-dried in vacuum, and is specifically: the collected first precipitate was freeze-dried in vacuo for 48h at-80 ℃.

6. The zinc vanadate coated carbon microsphere composite material according to claim 1, wherein the concentration of sodium metavanadate in ethylene glycol is 0.10 mol/L-0.15 mol/L; the concentration of the zinc triflate in the glycol is 0.030 mol/L-0.035 mol/L; the concentration of the polyvinylpyrrolidone in the glycol is 1.55-g/L-1.70 g/L; the concentration of the carbon microsphere in the glycol is 10 g/L;

the suspension dispersed with carbon microspheres is subjected to solvothermal reaction to obtain a solvothermal reaction product, which is specifically as follows: pouring the suspension with the carbon microspheres into a polytetrafluoroethylene mould for solvothermal reaction; the reaction condition of the solvothermal reaction is 180 ℃ for 8-12 h;

the specific method for centrifuging the solvothermal reaction product comprises the following steps: alternately centrifuging with deionized water and ethanol at 8000 r/min;

the second precipitate collected is freeze-dried in vacuum, and is specifically: vacuum freeze-drying the collected second precipitate for 48h at-80 ℃;

the heat preservation temperature is 400-600 ℃; the heat preservation temperature is specifically that the temperature is raised from the room temperature to the heat preservation temperature at a heating rate of 5 ℃/min; and the heat preservation for a certain time is 6 hours.

7. The application of the zinc vanadate coated carbon microsphere composite material according to claim 1, wherein the zinc vanadate coated carbon microsphere composite material is used as a positive electrode material of a water-based zinc ion battery.

8. The use of the zinc vanadate coated carbon microsphere composite according to claim 7, characterized by comprising in particular the following: and dispersing the composite material of the zinc vanadate nanosheets coated with the carbon microspheres, the conductive carbon black and the polyvinylidene fluoride in the mass ratio of 7:2:1 in N-methylpyrrolidone to prepare slurry, coating the slurry on a Ti foil, and then drying the Ti foil in an oven under a vacuum condition to obtain the water-based zinc ion battery anode material.

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