Vanadium-based prussian blue analogue composite, preparation method and application thereof

Abstract

The application discloses a vanadium-based prussian blue analogue composite material, which is a substance with two kinds of prussian blue analogue structures obtained by introducing zinc ions into a vanadium-based prussian blue analogue, wherein Fe, V and Zn are all redox active sites, and the vanadium-based prussian blue analogue composite material can provide additional specific capacity through multi-oxygen reduction reaction in the charging and discharging process. In addition, the trivalent vanadium ion solution obtained by using a zinc powder reduction method is more stable, and the use of ethylenediaminetetraacetic acid dipotassium (EDTA-2) as a chelating agent can obtain a complex with the trivalent vanadium ion, so that the purpose of inhibiting the rapid precipitation of the prussian blue analogue material is achieved. Through slow dissociation of metal ions and orderly coordination crystallization with ferricyanide ions, the crystal nucleus is slowly grown, and finally grown into a composite material with high crystallinity and low defect content, so that the influence of water molecules on the structure of the prussian blue analogue material is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of zinc ion batteries, in particular to a vanadium-based prussian blue compound, a preparation method and application thereof. BACKGROUND

[0002] At present, the main materials studied in the positive electrode material of zinc ion battery are manganese-based materials, vanadium-based materials, and prussian blue analogs. The open framework structure of prussian blue analogs allows ions to be embedded and extracted while maintaining the stability of the structure, which endows prussian blue analogs with the potential of being a host for various carrier ions. However, prussian blue analogs have very low specific capacity and low energy density. The prussian blue analogs obtained by the existing co-precipitation method have many structural defects and poor electrical conductivity, which leads to insufficient specific capacity, rate performance and cycle stability, and is not conducive to widespread use. The use of chelating agents can improve the structural defects caused by the rapid reaction rate during the precipitation process of prussian blue analogs and improve the electrochemical performance of the material. SUMMARY

[0003] Therefore, the present application provides a vanadium-based prussian blue compound, a preparation method and application thereof, which solves the technical problems of low specific capacity, poor rate performance and insufficient cycle stability of prussian blue analogs.

[0004] The vanadium-based prussian blue compound of the present application is a material with two types of prussian blue structures obtained by introducing zinc ions into vanadium-based prussian blue analogs, and Fe, V and Zn in the vanadium-based prussian blue compound are all redox active sites.

[0005] Further, the vanadium-based prussian blue compound with two types of prussian blue structures is obtained by introducing zinc ions into vanadium-based prussian blue analogs through zinc reduction.

[0006] The preparation method of the vanadium-based prussian blue compound of the present application comprises the following steps: reducing vanadium pentoxide to provide a vanadium source by zinc reduction, and using potassium ethylenediaminetetraacetate as a chelating agent to prepare a vanadium-based prussian blue compound.

[0007] Further, the preparation method comprises the following steps:

[0008] S1, heat the vanadium pentoxide solution and adjust the pH to weak acidity, add zinc powder and mix and heat, after sufficient reaction, add a chelating agent and react fully, and the obtained solution is denoted as solution A;

[0009] S2, dissolve the soluble ferricyanide in water and stir fully, and the obtained solution is denoted as solution B;

[0010] S3, slowly drop the A solution into the B solution under magnetic stirring to obtain a mixed solution, then stand or place in a hydrothermal kettle for reaction, then the product is filtered, washed and dried to obtain a vanadium-based prussian blue composite material;

[0011] Further, in step S1, the vanadium pentoxide solution is prepared by adding hydrogen peroxide to deionized water to obtain a mixed solvent, and then adding vanadium pentoxide powder into the mixed solvent and stirring to form a stable vanadium pentoxide solution.

[0012] Further, in step S1, the heating temperature is 50-70℃, hydrochloric acid is used to adjust the pH value to 3-4, the concentration of hydrochloric acid is 1mol / L, zinc powder is added and reacted for 10-30min, the molar ratio of the chelating agent to vanadium pentoxide is 1:2, and the chelating agent is added and reacted for 10-30min after being added.

[0013] Further, in step S2, the soluble cyanide is one of potassium ferricyanide and potassium ferrocyanide, and the concentration of the obtained B solution is 15-25mmol / L.

[0014] Further, in step S3, the molar ratio of the ferricyanide to vanadium pentoxide is 1:1, and the titration speed is 0.8-1.2ml / min.

[0015] Further, in step S3, when the co-precipitation method is used, the precipitation time is 18-24h, when the hydrothermal method is used, the reaction is carried out at 120℃ for 10h, the vacuum drying temperature is 50-70℃, and the drying time is 12-18h.

[0016] The application further discloses an application of the vanadium-based prussian blue composite material, which is used as a positive electrode material, zinc sheets are used as negative electrodes, and a water-based zinc ion battery is assembled.

[0017] The vanadium-based Prussian blue analogue composite material, the preparation method and the application disclosed by the application have the following beneficial effects: the vanadium-based Prussian blue analogue composite material has two kinds of Prussian blue analogue structures, and Fe, V and Zn in the vanadium-based Prussian blue analogue composite material all serve as redox active sites, which can provide additional specific capacity through multi-oxygen reduction reactions. The trivalent vanadium ion obtained by the zinc powder reduction method is more stable, and EDTA-2K is used as a chelating agent to obtain a complex with the trivalent vanadium ion, so that the purpose of inhibiting the rapid precipitation of the Prussian blue analogue material is achieved. Through slow dissociation of metal ions and orderly coordination crystallization with ferricyanide ions, the crystal nucleus is slowly grown, and finally grown into a composite material with high crystallinity and low defect content, so that the influence of water molecules on the structure of the Prussian blue analogue material is reduced. The method simultaneously forms vanadium ions and zinc ions in the system, and the vanadium-based Prussian blue analogue is obtained in one step, and zinc ions are introduced into the system to obtain the Prussian blue analogue composite material. The water-based zinc ion battery assembled by using the composite material as a positive electrode exhibits good redox performance and rate performance, and has great application prospect. The method has the advantages of simplicity, universality, environmental friendliness, low cost and strong controllability. BRIEF DESCRIPTION OF DRAWINGS

[0018] The application will be further described below in combination with the drawings and examples:

[0019] Figure 1 The XRD spectrum of the vanadium-based Prussian blue analogue composite material prepared in Example 1 is shown in the figure.

[0020] Figure 2 The SEM image of the vanadium-based Prussian blue analogue composite material prepared in Example 1 is shown in the figure.

[0021] Figure 3 The (a) cyclic voltammogram and (b) constant current charge-discharge curve of the water-based zinc ion battery assembled by using the vanadium-based Prussian blue analogue composite material prepared in Example 1 are shown in the figure.

[0022] Figure 4 The (a) rate performance and (b) cycle performance of the water-based zinc ion battery assembled by using the vanadium-based Prussian blue analogue composite material prepared in Example 1 are shown in the figure. DETAILED DESCRIPTION

[0023] Example 1

[0024] S1, 2ml hydrogen peroxide was added into 40ml deionized water to form a mixed solvent, 0.1091g vanadium pentoxide was weighed and dissolved in the mixed solvent, and magnetic stirring was performed for 1h, and then the solution was left to stand for 1-2 days; then the solution was heated in a water bath at 60°C for 10min, 1ml of 1mol / L hydrochloric acid was added dropwise, 20mg of zinc powder was weighed as a reducing agent and added to the above solution, and the solution was continuously heated and stirred for 20min to become a dark green solution, then the reaction residue was filtered with filter paper, and then 0.1214g of EDTA-2K was added to the solution, and the mixture was stirred for 30min to obtain a solution, which was marked as solution A;

[0025] S2, 0.1976g of potassium ferricyanide was dissolved in 40ml deionized water, and the solution was stirred for 30min to obtain a solution, which was marked as solution B;

[0026] S3, using a titration device, solution A was slowly added to solution B under magnetic stirring to obtain a mixed solution; then the mixed solution was placed in a hydrothermal kettle and reacted at 120°C for 10h, the obtained product was filtered, washed, and vacuum dried at 60°C for 24h to obtain a vanadium-based Prussian blue composite material.

[0027] Example Two

[0028] S1, 2ml hydrogen peroxide was added into 40ml deionized water to form a mixed solvent, 0.1818g vanadium pentoxide was weighed and dissolved in the mixed solvent, and magnetic stirring was performed for 1h, and then the solution was left to stand for 1-2 days; then the solution was heated in a water bath at 60°C for 10min, 1ml of 1mol / L hydrochloric acid was added dropwise, 20mg of zinc powder was weighed as a reducing agent and added to the above solution, and the solution was continuously heated and stirred for 20min to become a dark green solution, then the reaction residue was filtered with filter paper, and then 0.2022g of EDTA-2K was added to the solution, and the mixture was stirred for 30min to obtain a solution, which was marked as solution A;

[0029] S2, 0.3293g of potassium ferricyanide was dissolved in 40ml deionized water, and the solution was stirred for 30min to obtain a solution, which was marked as solution B;

[0030] S3, using a titration device, solution A was slowly added to solution B under magnetic stirring to obtain a mixed solution; then the mixed solution was left to stand. A co-precipitation method was used, and the product was precipitated at room temperature for 24h, then the product was filtered, washed, and vacuum dried at 60°C for 24h to obtain a vanadium-based Prussian blue composite material.

[0031] Example Three

[0032] S1, 2ml hydrogen peroxide was added into 40ml deionized water to prepare a mixed solvent, 0.1091g vanadium pentoxide was weighed and dissolved in the mixed solvent, and magnetic stirring was performed for 1h, and then the solution was left to stand for 1-2 days for standby; then the vanadium pentoxide solution after standing was heated in a water bath at 60℃ for 10min, 1ml of hydrochloric acid with a concentration of 1mol / L was added dropwise, 20mg of zinc powder was weighed as a reducing agent and added to the above solution, and heating and stirring were continued for 20min, and the solution turned into a dark green solution, then the reaction residue was filtered with filter paper, then 0.1214g of EDTA-2K was added to the solution, and the mixture was stirred for 30min to obtain a solution, which was marked as solution A;

[0033] S2, 0.2534g of potassium ferrocyanide was dissolved in 40ml of deionized water, and stirred for 30min to obtain a solution, which was marked as solution B;

[0034] S3, using a titration device, solution A was slowly added into solution B under magnetic stirring to obtain a mixed solution; then the mixed solution was placed in a hydrothermal kettle and reacted at 120℃ for 10h, the obtained product was filtered, washed, and vacuum dried at 60℃ for 24h to obtain a vanadium-based Prussian blue-like composite material.

[0035] Comparative Example 1

[0036] This comparative example is basically the same as Example 1, except that the reducing agent in Example 1 is replaced by ascorbic acid.

[0037] Comparative Example 2

[0038] This comparative example is basically the same as Example 1, except that the reducing agent in Example 1 is replaced by ascorbic acid, and the chelating agent is replaced by potassium citrate.

[0039] The prepared Prussian blue-like composite material was detected and analyzed, taking Example 1 as an example. Figure 1 is the XRD spectrum of Example 1. From the XRD spectrum, it can be seen that the obtained composite positive electrode material has the typical XRD diffraction peak of cubic phase Prussian blue analogue material. By comparing the obtained product with the PDF standard card, it can be seen that the product obtained by this method has the characteristic diffraction peak of vanadium ferrocyanide and zinc ferrocyanide, and is a Prussian blue-like composite material. At the same time, according to the SEM image of Figure 2 , it can be judged that the irregular granular substances are vanadium ferrocyanide, and the cubic phase substances are zinc ferrocyanide, which indicates that the zinc ions introduced into the vanadium solution form a Prussian blue-like compound, and finally form a vanadium-based Prussian blue-like compound, so it is speculated that the obtained product is a vanadium-based Prussian blue-like composite material.

[0040] The vanadium-based Prussian blue-like composite material prepared by the preparation method of the application is used as a positive electrode material of a zinc ion aqueous battery.

[0041] As an example of Example 1, 20wt% of conductive agent SuperP and 10wt% of binder polyvinylidene fluoride were added to the prepared composite material, mixed and ground for 30 min, 1-methyl-2-pyrrolidone was added, and the uniform slurry was prepared by dispersion and stirring for 24 h, then coated on a stainless steel mesh, and placed in a vacuum drying oven, dried at 60°C for 12 h to obtain a positive electrode sheet; a CR2032 button cell was assembled with zinc sheet as the negative electrode, GFD as the separator, and 3 mol / L zinc trifluoromethanesulfonate aqueous solution as the electrolyte. Similarly, Comparative Examples 1 and 2 were assembled into CR2032 button cells in the same way.

[0042] The CR2032 button cells assembled by the above method were placed on a CS electrochemical workstation (provided by Wuhan Coset Instrument Co., Ltd.) and a Neware battery test system (provided by Shenzhen Neware Electronic Co., Ltd.) for cyclic voltammetry test and constant current charge-discharge performance test, and the voltage range was relative to Zn / Zn 2+ 0.2V-2.0V.

[0043] Figure 3 The (a) cyclic voltammogram and (b) constant current charge-discharge curve of the vanadium-based Prussian blue composite material prepared in Example 1 assembled into a water-based zinc ion battery. Figure 3 (a) showed four pairs of redox peaks at a scan rate of 0.2 mV / s. Among them, the first pair (0.63 / 0.54V) corresponded to the V 3+ / V 4+ redox couple, the second pair (1.05 / 0.96V) corresponded to the V 4+ / V 5+ redox couple, the third pair (1.61 / 1.55V) corresponded to the working potential change caused by zinc ferricyanide, and the fourth pair (1.84 / 1.74V) corresponded to the Fe 2 + / Fe 3+ redox couple, and had good redox activity. As shown in Figure 3 (b), the discharge specific capacity of the composite material could reach 158 mAh / g at a current density of 0.1C. The voltage platform corresponded to the redox peak potential in the CV curve.

[0044] Figure 4 The (a) rate performance and (b) cycle performance of the vanadium-based Prussian blue composite material prepared in Example 1 assembled into a water-based zinc ion battery. Figure 4 The maximum discharge capacity of the composite material in (a) at current densities of 0.2, 0.5, 1.0, 2.0, 3.0, 5.0, and 0.2C was 92, 85, 76, 68, 59, 51, and 86 mAh / g, respectively, and the composite material had good rate performance.Figure 4 (b) the cycle performance of the composite material at a current density of 3C, the specific capacity is 32 mAh / g after 500 cycles, and the capacity retention rate is 64%.

[0045] At the same time, the water-based zinc ion battery assembled by each embodiment and the comparative example is subjected to electrochemical test, and the test results obtained under different rate current densities are as follows:

[0046]

[0047] It can be seen that the vanadium-based prussian blue composite prepared by the method has multiple redox active sites of Fe, V and Zn, which is beneficial to provide additional specific capacity through oxygen reduction reaction in the charging and discharging process. When the synthesized vanadium-based prussian blue composite is used as a positive electrode material of a water-based zinc ion battery, it has high voltage, good rate performance and cycle performance. Meanwhile, the method has the advantages of simplicity, universality, environmental friendliness, low cost and strong controllability, and has great application prospect.

[0048] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application but not limit the present application, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the purpose and scope of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A vanadium-based Prussian blue analog composite, characterized by: The vanadium-based Prussian blue analogue composite is obtained by reducing a vanadium pentoxide solution by a zinc reduction method, using dipotassium ethylenediaminetetraacetate as a chelating agent to introduce zinc ions into the vanadium-based Prussian blue analogue to obtain a material having both Prussian blue structures, and Fe, V and Zn in the vanadium-based Prussian blue analogue composite are all redox active sites.

2. The method of claim 1, wherein: The method comprises the following steps: S1, heating a vanadium pentoxide solution and adjusting the pH to weak acidity, and adding zinc powder to mix and heat, after sufficient reaction, adding a chelating agent to react sufficiently, and taking the obtained solution as an A solution; S2, dissolving a soluble ferricyanide in water and stirring sufficiently, and taking the obtained solution as a B solution; S3, slowly dropping the A solution into the B solution under magnetic stirring to obtain a mixed solution, and then standing or placing in a hydrothermal kettle to react, and then filtering, washing and drying the product to obtain a vanadium-based Prussian blue analogue composite.

3. The method for preparing vanadium-based Prussian blue composite material according to claim 2, characterized in that: In step S1, the vanadium pentoxide solution is prepared by adding hydrogen peroxide to deionized water to obtain a mixed solvent, and then adding vanadium pentoxide powder to the mixed solvent to stir and react sufficiently to form a stable vanadium pentoxide solution, and the amount of hydrogen peroxide is 1-2 ml.

4. The method for preparing vanadium-based Prussian blue composite material according to claim 3, characterized in that: In step S1, the heating temperature is 50-70℃, the pH value is adjusted to 3-4 by using hydrochloric acid, and the concentration of hydrochloric acid is 1 mol / L; zinc powder is added to react for 10-30 min; the molar ratio of the chelating agent to vanadium pentoxide is 1:2, and the chelating agent is added to react for 10-30 min after the addition.

5. The method of claim 1, wherein: In step S2, the soluble ferricyanide is one of potassium ferricyanide and potassium ferrocyanide, and the concentration of the obtained B solution is 15-25 mmol / L.

6. The method of claim 1, wherein: In step S3, the molar ratio of the ferricyanide to vanadium pentoxide is 1:1; and the titration speed is 0.8-1.2 ml / min.

7. The method for preparing vanadium-based Prussian blue composite material according to claim 6, characterized in that: In step S3, when a co-precipitation method is used, the precipitation time is 18-24 h; when a hydrothermal method is used, the reaction is carried out at 120℃ for 10 h; the vacuum drying temperature is 50-70℃, and the drying time is 12-18 h.

8. Use of a vanadium-based Prussian blue analogue composite according to claim 1, characterized in that: The vanadium-based Prussian blue analogue composite is used as a positive electrode material, and a zinc sheet is used as a negative electrode to assemble a water-based zinc ion battery.

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