A nano-silver modified vanadium pentoxide composite material, a preparation method thereof and application thereof in aqueous zinc ion batteries

Abstract

The application discloses a kind of nano silver modified vanadium pentoxide composite material and its preparation method and application in water-based zinc ion battery, and the composite material is prepared by nano silver in-situ doping porous vanadium pentoxide, and its synthesis method is: after vanadium source and terephthalic acid are mixed with nano silver dispersion liquid uniformly, solvent thermal reaction is carried out in high-pressure reaction kettle, and nano silver MIL-88B (V) precursor is obtained;Nano silver MIL-88B (V) precursor is pyrolyzed under air atmosphere, and nano silver modified vanadium pentoxide composite material with good structural stability, high conductivity and excellent electrochemical performance is obtained.The obtained battery has excellent rate performance and cycle performance and super-high discharge specific capacity when it is used as positive electrode material in water-based zinc ion battery.

Description

TECHNICAL FIELD

[0001] The application relates to a water-based zinc ion battery positive electrode material, in particular to a nano-silver modified vanadium pentoxide composite material, and also relates to a preparation method thereof and application thereof in a water-based zinc ion battery, and belongs to the technical field of new energy batteries. BACKGROUND

[0002] With the gradual depletion of fossil fuels and the gradual intensification of greenhouse effect, energy shortage and environmental pollution have become two major problems that need to be solved for sustainable development, and it is urgent to develop and utilize green and efficient energy storage devices to replace fossil fuels such as oil and natural gas. Lithium ion batteries have the advantages of high energy density and long cycle service life, and are most widely used in the field of energy storage. However, lithium ion batteries have low balanced electrode potential, high cost, toxic organic electrolyte and flammable problems, which seriously limit their application in high-power energy storage systems. Compared with the flammable and volatile safety hazards of organic electrolyte, water-based electrolyte has higher safety, and also has the advantages of environmental friendliness, low production cost and high ionic conductivity, and is expected to be used for developing the next generation of green and environmentally friendly rechargeable batteries. Among many water-based rechargeable batteries, water-based zinc ion batteries are considered to be the most promising water-based battery system due to their high theoretical specific capacity (820 mAh g -1 ) and volume energy density (5855 mAh cm -3 ), low redox potential (-0.76 V vs. standard hydrogen electrode), high stability and low price. In the water-based zinc ion battery system, the selection of the positive electrode material is crucial, which needs to ensure that zinc ions can be reversibly deintercalated in the material crystal structure, and has a decisive influence on the performance of the battery system. Therefore, designing a high-performance water-based zinc ion battery positive electrode material has become a hot and difficult point of current research.

[0003] Vanadium pentoxide has a typical layered structure, which is very suitable for zinc ion diffusion; and vanadium has V 5+ , V 4+ and V 3+Vanadium pentoxide can occur multi-electron transfer redox reactions in various valence states, showing high electrochemical activity and theoretical specific capacity, and is one of the most promising positive electrode materials. However, the low specific surface area and porosity of the traditional vanadium pentoxide material seriously hinder the transfer of zinc ions during the electrochemical reaction, and the poor conductivity of vanadium pentoxide also limits the rate performance and cycle performance of the battery. It has been reported that the composite of vanadium pentoxide and high-conductivity materials such as carbon nanotubes and porous carbon can significantly improve the electronic conductivity of the composite material and achieve good rate performance. However, the method of realizing the composite of vanadium pentoxide and high-conductivity materials cannot fundamentally solve the problem of low specific surface area and porosity inherent in vanadium pentoxide, and it is difficult to stably combine vanadium pentoxide and high-conductivity materials together, thereby affecting the capacity performance and cycle stability performance. SUMMARY

[0004] In view of the defects of low specific surface area, poor porosity and low conductivity of the vanadium pentoxide positive electrode material in the prior art, the first object of the present application is to provide a nano-silver modified vanadium pentoxide composite material composed of nano-silver in-situ doped on the surface and inside of porous vanadium pentoxide, which has high specific surface area, good conductivity, excellent structural stability and high electrochemical activity.

[0005] The second object of the present application is to provide a preparation method of the nano-silver modified vanadium pentoxide composite material, which is simple in operation, low in cost and conducive to large-scale production.

[0006] The third object of the present application is to provide an application of the nano-silver modified vanadium pentoxide composite material, which is used as a positive electrode material of aqueous zinc ion battery, and can obtain high discharge specific capacity, excellent rate performance and cycle stability performance.

[0007] In order to achieve the above technical purposes, the present application provides a nano-silver modified vanadium pentoxide composite material composed of a stable heterostructure formed by in-situ doping of nano-silver in porous vanadium pentoxide.

[0008] The nano-silver modified vanadium pentoxide composite material of the present application is composed of nano-silver doped in-situ on the surface and inside of porous vanadium pentoxide. The composite material has a unique "silver-vanadium pentoxide" heterostructure, which can enhance the conductivity of the whole material, effectively promote the transfer of electrons, and improve the rate performance of the battery; the nano-silver and the porous vanadium pentoxide have a close interface effect, which can inhibit the collapse of the positive material structure of the electrode during the charge and discharge cycle process, effectively improving the overall cycle life of the battery; the porous vanadium pentoxide derived from the MOFs material has a high specific surface area and porosity, which can provide more electrochemical reaction active sites, and at the same time promote the migration and diffusion of zinc ions, realize fast ion diffusion kinetics and high discharge specific capacity.

[0009] As a preferred scheme, the mass ratio between the nano-silver and the porous vanadium pentoxide is 10-20:1.

[0010] As a preferred scheme, the length of the porous vanadium pentoxide spindle is 6-10 μm, the width is 0.8-1.2 μm, and the surface is rich in micro-mesopores.

[0011] The present application also provides a preparation method of the nano-silver modified vanadium pentoxide composite material, which comprises the following steps:

[0012] 1) After mixing the vanadium source and terephthalic acid with the nano-silver dispersion liquid uniformly, a small amount of dilute hydrochloric acid solution is added, and then the mixture is transferred to a high-pressure reaction kettle for solvothermal reaction to obtain a nano-silver@MIL-88B(V) precursor;

[0013] 2) The nano-silver@MIL-88B(V) precursor is pyrolyzed in an air atmosphere to obtain the nano-silver doped vanadium pentoxide composite material.

[0014] The key of the technical scheme of the present application is to prepare the nano-silver@MIL-88B(V) precursor in-situ by solvothermal method, and then to obtain the nano-silver doped vanadium pentoxide composite material by pyrolysis of the nano-silver@MIL-88B(V) precursor. On the one hand, the in-situ solvothermal method can make the MIL-88B(V) grow uniformly on the surface of the nano-silver, which is conducive to the formation of nano-silver@MIL-88B(V) precursor with uniform size; on the other hand, the inventors found that the one-step pyrolysis method can make the nano-silver particles and the porous vanadium pentoxide tightly combined together through heterojunction effect, which greatly improves the interface stability between the porous vanadium pentoxide and the nano-silver, and is conducive to improving the cycle stability of the porous vanadium pentoxide and the nano-silver as positive materials for aqueous zinc ion batteries.

[0015] As a preferred scheme, the molar ratio of the vanadium source and terephthalic acid is 1:1. The vanadium source is a common water-soluble vanadium salt, such as vanadium chloride, etc.

[0016] As a preferred scheme, the ratio of vanadium source to nano-silver is 3-5 mmol / 50 mg. If the ratio of nano-silver is too high, since nano-silver itself does not contribute to the capacity, when the content of nano-silver is too high, the specific discharge capacity of the overall composite material is reduced; meanwhile, too many nano-silver particles are prone to agglomeration, resulting in the decline of the electrochemical performance of the overall material. When the ratio of nano-silver is too low, the conductivity of the composite material is not significantly improved, which will affect the rate performance.

[0017] As a preferred scheme, the conditions of the solvothermal reaction are as follows: reaction at a temperature of 110-130 DEG C for 24-48 hours, and using anhydrous ethanol as the reaction solvent.

[0018] As a preferred scheme, the conditions of the pyrolysis are as follows: pyrolysis at a temperature of 400-450 DEG C for 120-240 minutes, and the heating rate is 1-2 DEG C / min. If the pyrolysis temperature is too high, the structure of MIL-88B(V) collapses, resulting in the decline of the porosity of the final derivative; if the pyrolysis temperature is too low, MIL-88B(V) is difficult to completely decompose into metal oxide.

[0019] The application further provides an application of the nano-silver modified vanadium pentoxide composite material, which is used as a positive material of an aqueous zinc ion battery.

[0020] The preparation method of the nano-silver modified vanadium pentoxide composite material of the application comprises the following specific steps:

[0021] 1) ultrasonic dispersion of nano-silver in anhydrous ethanol to form a uniform solution;

[0022] 2) dissolving vanadium trichloride in the nano-silver dispersion to form solution A;

[0023] 3) dissolving terephthalic acid in anhydrous ethanol to form solution B;

[0024] 4) slowly adding solution B to solution A, adding a small amount of dilute hydrochloric acid, and magnetically stirring for 60 minutes to obtain a uniform solution;

[0025] 5) transferring the above solution into a polytetrafluoroethylene-lined high-pressure reaction kettle, heating at 120 DEG C for 48 hours; centrifuging, washing and drying to obtain Ag@MIL-88B(V) precursor;

[0026] 6) placing the precursor into a muffle furnace, pyrolyzing at 400 DEG C for 2 hours, and setting the heating rate to 1 DEG C / min to obtain a nano-silver modified vanadium pentoxide composite.

[0027] The method for preparing the water-based zinc ion battery by using the nano-silver modified vanadium pentoxide composite material of the application comprises the following steps: weighing the nano-silver / vanadium pentoxide composite material, acetylene black and polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1, putting them into a mortar, then adding 1-methyl 2-pyrrolidone (NMP) and grinding to obtain a uniform slurry; coating the obtained slurry on a 250-mesh stainless steel mesh, and then vacuum drying at 60 DEG C for 10 hours to obtain a positive electrode sheet; using a glass fiber membrane as a separator; using a 3 mol / L zinc trifluoromethane sulfonate aqueous solution as an electrolyte; and using a metal zinc sheet as a negative electrode sheet to construct a CR2032 type button-shaped water-based zinc ion battery.

[0028] Compared with the prior art, the technical effect brought by the technical scheme of the application is that:

[0029] The nano-silver modified vanadium pentoxide composite material of the application is composed of nano-silver doped in-situ on the surface and inside of porous vanadium pentoxide. The composite material has a unique "silver-vanadium pentoxide" heterostructure, which can enhance the conductivity of the whole material, effectively promote the transfer of electrons and improve the rate performance of the battery; the nano-silver and the porous vanadium pentoxide have a close interface effect, which enhances the structural stability of the composite material, can inhibit the collapse of the positive electrode material structure during the charge and discharge cycle process of the electrode, and effectively improves the overall cycle life of the battery; the porous vanadium pentoxide derived from the MOFs material has a high specific surface area and porosity, which can provide more electrochemical reaction active sites, and at the same time, promote the migration and diffusion of zinc ions, realize fast ion diffusion kinetics and high discharge specific capacity.

[0030] After the nano-silver modified vanadium pentoxide composite material in the application is applied as a positive electrode material of a water-based zinc ion battery, the Zn / / Ag-V2O5 water-based zinc ion battery has excellent cycle performance and ultra-high discharge specific capacity.

[0031] The preparation method of the nano-silver modified vanadium pentoxide composite material of the application is simple in operation and low in cost, and is conducive to large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The X-ray diffraction spectrum of the nano-silver doped vanadium pentoxide composite material prepared for Example 1 and Example 2.

[0033] Figure 2 The X-ray diffraction spectrum of the nano-silver doped vanadium pentoxide composite material prepared for Example 1 and Example 2. Figure 2 b) and Example 2 Figure 2 a). The scanning electron microscope graph of the nano-silver doped vanadium pentoxide composite material prepared for Example 1 and Example 2.

[0034] Figure 3N2 adsorption-desorption isotherm graph of the nanosilver doped vanadium pentoxide composite material prepared for Example 1 and Example 2.

[0035] Figure 4 V2p high resolution X-ray photoelectron spectroscopy (XPS) graph of the nanosilver doped vanadium pentoxide composite material prepared for Example 1 and Example 2.

[0036] Figure 5 The specific capacitance of the nanosilver doped vanadium pentoxide composite material prepared for Example 1 and Example 2 is 0.1 A g -1 The cycle performance graph of the aqueous zinc ion battery of Example 1 and Example 2 at room temperature.

[0037] Figure 6 The specific capacitance of the nanosilver doped vanadium pentoxide composite material prepared for Example 1 and Example 2 is 5.0 A g -1 The cycle performance graph of the aqueous zinc ion battery of Example 1 and Example 2 at room temperature.

[0038] Figure 7 The rate performance graph of the aqueous zinc ion battery of Example 1 and Example 2 at room temperature.

[0039] Figure 8 The AC impedance graph of the aqueous zinc ion battery of Example 1 and Example 2 at room temperature.

[0040] Figure 9 The charge-discharge curve graph of the aqueous zinc ion battery of Example 1 and Example 2 at room temperature.

[0041] Figure 10 The zinc ion diffusion coefficient graph of the aqueous zinc ion battery of Example 1 and Example 2 at room temperature. DETAILED DESCRIPTION

[0042] The present application will be further described and illustrated in conjunction with specific embodiments and the accompanying drawings, so that those skilled in the art can better understand and implement the present application, but the embodiments are not intended to limit the present application.

[0043] Example 1

[0044] 1. Preparation of nanosilver modified vanadium pentoxide composite:

[0045] Take 50 mg of nano-silver into 20 mL of anhydrous ethanol, continuously ultrasonic for 60 minutes to obtain a uniform nano-silver dispersion, then take 628 mg of vanadium trichloride and add it into the nano-silver dispersion, stir uniformly to obtain a uniform solution, mark it as solution A; take 664 mg of terephthalic acid (H2BDC) and add it into 20 mL of anhydrous ethanol, stir uniformly to obtain solution B; under the condition of magnetic stirring, gradually add solution B into solution A, then drop 2 mL of dilute hydrochloric acid solution (1 mol / L), continue to stir for 30 minutes; transfer the above mixture into a 100 mL polytetrafluoroethylene lined stainless steel autoclave, heat at 120°C for 48 hours to obtain a dark green solid product, then wash with anhydrous ethanol for three times, dry the obtained product at 60°C for 12 hours to obtain the Ag@MIL-88B(V) precursor; finally, transfer the obtained powder into a muffle furnace connected with flowing air, pyrolyze at 400°C for 120 minutes, the heating rate is set to 1°C / min, after natural cooling to room temperature, the obtained fluffy powder product is the nano-silver modified vanadium pentoxide composite, simply referred to as Ag-V2O5.

[0046] 2. Preparation of positive electrode sheet:

[0047] Take 70 mg of Ag-V2O5 composite and add it into a mortar, then take 20 mg of acetylene black and 10 mg of polyvinylidene fluoride (PVDF), also pour into the mortar, grind the above mixture for about 20 minutes; take an appropriate amount of 1-methyl 2-pyrrolidone (PVDF) and drop it into the mortar, then quickly grind with the pestle until the slurry on the surface of the mortar has no particle feeling; then evenly coat the slurry on the cut 250-mesh stainless steel mesh small round sheet (diameter 12 mm), vacuum dry at 60°C for 12 hours to obtain the positive electrode sheet.

[0048] 3. Preparation of electrolyte:

[0049] Take 21.8 g of zinc trifluoromethanesulfonate and add it into a beaker, then take 20 mL of deionized water and add it, continuously ultrasonic for 30 minutes to obtain a 3 mol / L zinc trifluoromethanesulfonate aqueous solution.

[0050] 4. Preparation of aqueous zinc ion battery:

[0051] Select CR2032 type battery shell, the battery assembly sequence is negative shell-negative sheet (cut zinc sheet)-glass fiber diaphragm-electrolyte (6-9 drops of electrolyte are taken with a rubber bulb dropper and added to the middle of the diaphragm)-positive electrode sheet-positive shell.

[0052] Comparative Example 1

[0053] Example 2 differs from Example 1 in that 628 mg of vanadium trichloride is dissolved in 20 mL of anhydrous ethanol, and no nano-silver is added.

[0054] Figure 1 By comparing the XRD spectra, it can be seen that the diffraction peak position of the derived porous V2O5 can completely correspond to the orthorhombic vanadium pentoxide (PDF # 85-0601), and the characteristic peak of Ag (PDF # 89-3722) can also be observed in Ag-V2O5, which proves the successful preparation of the composite material.

[0055] Figure 2 a shows that V2O5 has a spindle structure, and the size is relatively uniform; from 2b, it can be seen that Ag-V2O5 retains the basic morphology of V2O5, the length is 6-10 μm, the width is 0.8-1.2 μm, and the surface is rich in micro-mesopores.

[0056] Figure 3 The N2 adsorption-desorption isotherm graphs of the nano-silver modified vanadium pentoxide composite material prepared in Example 1 and the vanadium pentoxide prepared in Example 2. From the graph, it can be observed that the specific surface area of Ag-V2O5 is as high as 85.53 m 2 g -1 , which is much higher than the specific surface area of pure V2O5 (47.92 m 2 g -1 ); at the same time, the BJH model (Barrett-Joyner-Halenda) is used to calculate that Ag-V2O5 has a wider pore size distribution than V2O5, indicating that Ag-V2O5 is a typical micro-mesoporous material. The micro-mesoporous structure produced promotes the diffusion of zinc ions in the Ag-V2O5 nanocrystals, thereby significantly improving the electrochemical performance of the Ag-V2O5 positive electrode.

[0057] Figure 4 The V 2p high-resolution X-ray photoelectron spectroscopy (XPS) graphs of the nano-silver modified vanadium pentoxide composite material prepared in Example 1 and the vanadium pentoxide prepared in Example 2, and two V 2p electronic states corresponding to V 2p 3 / 2 and V2p 1 / 2 can be observed in both samples. In addition, it can be found that the characteristic peak positions of the two electronic states of Ag-V2O5 (516.2 eV, 523.6 eV) are shifted to a lower binding energy direction compared to V2O5 (516.4 eV, 523.9 eV), which confirms that there is a strong interaction force between Ag and V2O5 in the Ag-V2O5 composite, and there is an electron transfer at the heterojunction.

[0058] Figure 5 The specific discharge capacity of the nano-silver modified vanadium pentoxide composite material prepared in Example 1 and the vanadium pentoxide prepared in Example 2 at 0.1 A g -1Cycling performance diagrams of aqueous zinc-ion batteries in Examples 1 and 2 under room temperature conditions. The results show that the aqueous zinc-ion battery in Example 1 still maintains a capacity of 365.2 mAh g⁻¹ after 100 cycles. -1 The aqueous zinc-ion battery in Example 2 has a high reversible capacity, while its capacity is only 150 mAh g after 100 cycles. -1 This demonstrates that the aqueous zinc-ion battery of Example 1 has better cycle performance than the aqueous zinc-ion battery of Example 2.

[0059] Figure 6 For 5.0A g -1 Cycling performance diagrams of aqueous zinc-ion batteries in Examples 1 and 2 under room temperature conditions. The results show that the aqueous zinc-ion battery of Example 1 still exhibits a high discharge specific capacity even at high current densities (retaining 270 mAh g⁻¹ after 2000 cycles). -1 The aqueous zinc-ion battery in Example 2 only had a capacity of 79.5 mAh g after 2000 cycles. -1 This demonstrates that the aqueous zinc-ion battery of Example 1 has a higher discharge specific capacity and higher cycle stability.

[0060] Figure 7 The diagram shows the rate performance of the aqueous zinc-ion batteries in Examples 1 and 2 at room temperature. The results indicate that at current densities of 0.1 A g... -1 0.2A g -1 0.5A g -1 1.0A g -1 and 2.0A g -1 At that time, the specific capacity provided by the aqueous zinc-ion battery in Example 1 was 422.5 mAh g. -1 412.4mAh g -1 399.8mAh g -1 381.7mAh g -1 and 363.3mAh g -1 Moreover, when the current density recovers to 0.1 A g -1 At that time, the discharge capacity can recover to 420.3 mAh g. -1 This is far superior to the aqueous zinc-ion battery of Example 2, indicating that the aqueous zinc-ion battery of Example 1 has better rate performance.

[0061] Figure 8 The AC impedance diagrams for the aqueous zinc-ion batteries of Examples 1 and 2 are shown below, under room temperature conditions. The results indicate that the charge transfer impedance (Ro) of the aqueous zinc-ion battery in Example 1 is... ct) is 31Ω, which is much lower than 220Ω of the aqueous zinc-ion battery of Example 2, indicating that the positive active material of Example 1 has higher conductivity and smaller internal resistance.

[0062] Figure 9 is a charge-discharge curve diagram of the aqueous zinc-ion batteries of Example 1 and Example 2 under room temperature conditions. Compared with the aqueous zinc-ion battery of Example 2, the aqueous zinc-ion battery of Example 1 exhibits higher specific discharge capacity, indicating that the zinc-ion storage capacity of the aqueous zinc-ion battery of Example 1 is better.

[0063] Figure 10 is a zinc-ion diffusion coefficient diagram of the aqueous zinc-ion batteries of Example 1 and Example 2 under room temperature conditions. The results show that the zinc-ion diffusion coefficient (D Zn2+ ) of the charge-discharge process of the aqueous zinc-ion battery of Example 1 is mainly concentrated between 10 -10 to 10 -9 cm -2 s -1 , which is about 10 times higher than that of the aqueous zinc-ion battery of Example 2, indicating that the aqueous zinc-ion battery system of Example 1 has faster zinc-ion diffusion kinetics.

[0064] The above-described examples are only preferred examples for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent replacement or transformation made by the person skilled in the art on the basis of the present application is within the protection scope of the present application. The protection scope of the present application is subject to the claims.

Claims

1. Application of a nano-silver modified vanadium pentoxide composite material, characterized in that: The application relates to application of a nano-silver modified vanadium pentoxide composite material as a positive electrode material of a water-based zinc ion battery. ​ The nano-silver modified vanadium pentoxide composite material is composed of a spindle-shaped hierarchical porous structure in which nano-silver is in-situ doped on the surface and inside of porous vanadium pentoxide; the mass ratio between the porous vanadium pentoxide spindle and the nano-silver is 10-20:1; the length of the porous vanadium pentoxide spindle is 6-10 microns, the width is 0.8-1.2 microns, and the surface is rich in micropores and mesopores.

2. The application of nano-silver modified vanadium pentoxide composite material according to claim 1, characterized in that: The nano-silver modified vanadium pentoxide composite material is prepared by the following method: 1) a vanadium source and terephthalic acid are uniformly mixed with a nano-silver dispersion solution, a small amount of dilute hydrochloric acid solution is added into the mixture, and then the mixture is transferred into a high-pressure reaction kettle to perform a solvothermal reaction, so as to obtain a nano-silver@MIL-88B(V) precursor; 2) the nano-silver@MIL-88B(V) precursor is pyrolyzed under an air atmosphere, and the nano-silver modified vanadium pentoxide composite material is obtained.

3. The application of nano-silver modified vanadium pentoxide composite material according to claim 2, characterized in that: The molar ratio of the vanadium source and the terephthalic acid is 1:

1.

4. The application of nano-silver modified vanadium pentoxide composite material according to claim 2, characterized in that: The ratio of the vanadium source and the nano-silver is 3-5 mmol / 50 mg.

5. The application of nano-silver modified vanadium pentoxide composite material according to claim 2, characterized in that: The solvothermal reaction is performed at a temperature of 110-130 DEG C for 24-48 hours.

6. The application of nano-silver modified vanadium pentoxide composite material according to claim 2, characterized in that: The pyrolysis under the air atmosphere is performed at a temperature of 400-450 DEG C for 120-240 minutes, and the heating rate is 1-2 DEG C / min.

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