A three-dimensional nanoflower-shaped titanium-based Prussian blue analog electrode material assembled by nanosheets and its preparation method and application

Abstract

The present invention relates to the technical field of aqueous zinc ion batteries, and in particular to a three-dimensional nano-flower-shaped titanium-based Prussian blue analog electrode material assembled by nanosheets, and a preparation method and application thereof. The present invention provides a method for preparing a positive electrode material for a zinc ion battery, wherein an aqueous solution of potassium ferrocyanide is added to a glacial acetic acid / ethanol solution of tetrabutyl titanate, mixed and then heated in a water bath, and finally the precipitate is washed and dried to obtain a three-dimensional nano-flower-shaped titanium-based Prussian blue analog electrode material. The preparation method of the battery material of the present invention has simple process operation, and the positive electrode material of the battery is a flower-shaped structure assembled by two-dimensional nanosheets, which can not only ensure good structural stability, but also effectively slow down the change in volume during charging and discharging, thereby significantly improving the charging and discharging cycle performance and ion migration rate. The prepared positive electrode material of the battery is used in an aqueous zinc ion battery, and the charging and discharging cycle stability is high, and the electrochemical performance is better than that of nano-granular electrode materials.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous zinc ion batteries, and particularly to a three-dimensional nanoflower-like titanium-based Prussian blue analogue electrode material assembled by nanosheets, a preparation method thereof and an application thereof. Background Art

[0002] In the past few decades, the global environmental problems caused by the overuse of fossil fuels have greatly promoted the utilization of renewable energy. Among them, lithium-ion batteries have been widely used in various electronic devices. However, in recent years, due to problems such as limited lithium reserves, large fluctuations in market prices and safety, the exploration of alternative lithium-ion battery technologies has been greatly promoted. A rechargeable aqueous zinc ion battery mainly consists of a zinc salt-based aqueous electrolyte, a zinc metal negative electrode and a positive electrode. Compared with the flammable organic electrolytes in lithium-ion batteries, aqueous electrolytes have lower costs, higher safety and ionic conductivities. In addition, the zinc negative electrode has a high theoretical capacity (840 mAh / g) and a low electrochemical potential (-0.76 V vs. SHE). The positive electrode materials of aqueous zinc ion batteries are mainly divided into vanadium-based materials, manganese-based materials, Prussian blue analogues (PBAs) and organic materials. Among them, PBAs have received extensive attention due to their attractive characteristics such as three-dimensional open frameworks, high stability, and multiple active sites. Such materials usually have a simple cubic structure, and the chemical formula is generally A x M[Fe(CN)6] y ·nH2O (A usually represents an alkali metal, M represents a transition metal, 0 < x < 2, 0 < y ≤ 1). PBAs have the following advantages as positive electrode materials: ① The open framework of PBAs provides rich three-dimensional diffusion channels for the diffusion of various charge carrier ions; ② The charge storage behavior of PBAs can be optimized by controlling the composition of transition metal ions in PBAs, while the entire open framework structure remains almost unchanged. However, the research on PBAs as positive electrode materials for aqueous zinc ion batteries is still in its initial stage. When Prussian blue is used as the positive electrode material for aqueous zinc ion batteries, most of them show poor cycle performance, rapid capacity decay, and the evolution of oxygen reaction will occur due to their relatively high operating voltage (1.7 V vs. Zn2+ / Zn). How to overcome the defects of the above-mentioned prior art has become an urgent problem to be solved in this field. Summary of the Invention

[0003] In order to overcome the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of a three-dimensional nanoflower-like titanium-based Prussian blue analogue electrode material assembled by nanosheets. The electrode material is obtained by adding an ice acetic acid / ethanol solution of tetrabutyl titanate to a ferricyanide solution and mixing them evenly and then reacting. The preparation method of the battery positive electrode material provided by the present invention has simple process operation, and when the prepared battery positive electrode material is used in an aqueous zinc ion battery, the charge and discharge cycle stability is relatively high.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is:

[0005] The invention provides a method for preparing a three-dimensional nano-flower-shaped titanium-based Prussian blue analog electrode material assembled by nanosheets. A glacial acetic acid / ethanol solution of tetrabutyl titanate is added to a ferrocyanide solution, the mixture is evenly mixed, and then reacted to obtain the three-dimensional nano-flower-shaped titanium-based Prussian blue analog electrode material assembled by nanosheets.

[0006] Preferably, the ferrocyanide solution includes one or more of potassium ferrocyanide solution, potassium ferrocyanide solution, sodium ferrocyanide solution and sodium ferrocyanide solution; and the concentration of the ferrocyanide solution is 0.1 mol / L.

[0007] Preferably, in the glacial acetic acid / ethanol solution of tetrabutyl titanate, the concentration of tetrabutyl titanate is 0.1 mol / L; and the volume ratio of the glacial acetic acid to ethanol is (0.5-2):50.

[0008] Preferably, the molar ratio of tetrabutyl titanate in the glacial acetic acid / ethanol solution of tetrabutyl titanate to ferrocyanide ions in the ferrocyanide solution is (1-2):2.

[0009] Preferably, the pH of the ferrocyanide solution is less than 3.

[0010] More preferably, the pH of the ferrocyanide solution is <1.

[0011] Preferably, the reaction is carried out at 50-60° C. for 3-8 hours.

[0012] Preferably, after the reaction is completed, the mixture is allowed to stand for a period of time to precipitate.

[0013] The three-dimensional nano-flower-shaped titanium-based Prussian blue analog electrode material assembled by the nanosheets prepared by the preparation method is used to prepare the positive electrode of the aqueous zinc ion battery.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention provides a method for preparing a positive electrode material for a zinc ion battery. The method comprises adding an aqueous solution of potassium ferrocyanide to a glacial acetic acid / ethanol solution of tetrabutyl titanate, mixing and then heating in a water bath, and finally washing and drying the precipitate to obtain a three-dimensional nano-flower-shaped titanium-based Prussian blue analog electrode material. The method for preparing the positive electrode material for a battery provided by the present invention has a simple process operation. The positive electrode material for a battery is a flower-shaped structure assembled from two-dimensional nanosheets, which can not only ensure good structural stability, but also effectively slow down the change in volume during the charge and discharge process, thereby significantly improving the charge and discharge cycle performance and ion migration rate. The obtained positive electrode material for a battery is used in an aqueous zinc ion battery, and the charge and discharge cycle stability is high, and the electrochemical performance is better than that of nano-granular electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the X-ray diffraction pattern of the sample of Example 1;

[0017] Figure 2 It is the electron microscope scanning image of the sample of Example 1;

[0018] Figure 3 It is the electron microscope scanning image of the sample of comparative example 1;

[0019] Figure 4 It is the electron microscope scanning image of the sample of comparative example 2;

[0020] Figure 5 It is the electron microscope scanning image of the sample of comparative example 3;

[0021] Figure 6 The sample of Example 1 is used as the positive electrode material of aqueous zinc ion full battery at 0.05A·g -1 Cyclic performance plots of current density;

[0022] Figure 7 The sample of comparative example 1 is used as the positive electrode material of aqueous zinc ion full battery at 0.05A·g -1 Cyclic performance plots of current density;

[0023] Figure 8 The sample of Example 1 is the rate performance of the positive electrode material of an aqueous zinc ion full battery. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0026] Example 1 Preparation of titanium-based Prussian blue analog electrode material

[0027] The drugs required for this experiment are: anhydrous ethanol, glacial acetic acid, tetrabutyl titanate, hydrochloric acid (37%), potassium ferrocyanide. The specific preparation method is as follows:

[0028] 1. Add 200 μL of glacial acetic acid to 10 mL of anhydrous ethanol and stir for 1 minute. Then, add 680 μL of tetrabutyl titanate to the glacial acetic acid / anhydrous ethanol solution at a rate of 20 μL / s under continuous stirring, and stir for another 2 minutes to obtain a glacial acetic acid / anhydrous ethanol solution of tetrabutyl titanate with a concentration of 0.1 mol / L.

[0029] 2. Add 735 mg of potassium ferrocyanide to 20 mL of deionized water and stir until the particles are completely dissolved to obtain a 0.1 mol / L potassium ferrocyanide aqueous solution. Then add 2.5 mL of hydrochloric acid to the potassium ferrocyanide aqueous solution to make the pH of the reaction system 0.1 and stir for 1 minute.

[0030] 3. The glacial acetic acid / anhydrous ethanol solution of tetrabutyl titanate in step 1 is added to the potassium ferrocyanide aqueous solution in step 2 at a rate of 0.1 mL / s under continuous stirring, and then the resulting mixed solution is heated in a water bath at 60° C. for 4 hours under continuous stirring, and the stirring rate of the water bath is 300 r / min; the reacted solution is allowed to stand at room temperature for 4 days, and a precipitate will precipitate at the bottom of the solution;

[0031] 4. The precipitate in step 3 was washed three times by centrifugation with a mixture of ethanol and deionized water in a volume ratio of 1:1, and finally vacuum dried at 100° C. for 12 hours to obtain a titanium-based Prussian blue analog electrode material.

[0032] The X-ray diffraction results (XRD) of the sample of Example 1 are as follows: Figure 1 As shown, it is consistent with the diffraction peak of TiFe(CN)6·2H2O (JCPDS no.23-0605), indicating that titanium ferrocyanide (TiHCF) is successfully prepared in this example and has a face-centered cubic structure of Fm-3m.

[0033] The scanning electron microscope image of the sample of Example 1 is as follows Figure 2 As shown, the sample is a flower-like structure assembled from two-dimensional nanosheets, which not only ensures good structural stability, but also effectively slows down the volume change during the charge and discharge process, thereby significantly improving the charge and discharge cycle performance and ion migration rate.

[0034] Comparative Example 1 Preparation of Titanium-based Prussian Blue Analogue Electrode Material

[0035] The preparation method is the same as that of Example 1, except that, in step 1, glacial acetic acid is not added to anhydrous ethanol.

[0036] The scanning electron microscope image of the sample of Comparative Example 1 is as follows: Figure 3 As shown, the sample is a nanoparticle, and the capacitance of the nanoparticle is not as good as that of the three-dimensional nanoflower-shaped sample.

[0037] Comparative Example 2 Preparation of Titanium-based Prussian Blue Analogue Electrode Material

[0038] The preparation method is the same as that of Example 1, except that step 3 is to stir the obtained mixed solution at room temperature for 4 hours. The electron microscope scanning results of the obtained sample are as follows: Figure 4 As shown, the sample did not form nanosheets.

[0039] Comparative Example 3 Preparation of Titanium-based Prussian Blue Analogue Electrode Material

[0040] The preparation method is the same as that of Example 1, except that hydrochloric acid is not added in step 2 to adjust the pH of the potassium ferrocyanide aqueous solution. The electron microscopy results of the prepared sample are as follows: Figure 5 As shown, the sample is spherical TiHCF.

[0041] Experimental Example 1 Characterization of Titanium-based Prussian Blue Analogue Electrode Materials

[0042] The samples of Example 1 and Comparative Example 1 were respectively made into positive electrode sheets. Using 0.8 mL of N-methylpyrrolidone (NMP) as a dispersant, 0.6 g of the sample of Example 1 or Comparative Example 1, 0.1 g of conductive carbon black (SuperP), and 0.3 g of polyvinylidene fluoride were uniformly stirred to prepare an adhesive slurry, which was coated on a carbon paper material and then dried in a vacuum oven at 60°C for 12 h. A positive electrode sheet with a diameter of 12 mm was obtained using a slicer.

[0043] The full cell was assembled in a glove box filled with Ar and with H2O and O2 contents less than 1ppm. The electrode sheet prepared above was used as the positive electrode, a zinc foil with a thickness of 0.1mm was used as the negative electrode, glass fiber was used as the separator, and the electrolyte was 2M Zn(CF3SO3)2 to form an aqueous zinc ion full cell. The constant current charge and discharge cycle performance tests of the full cell were all carried out in a battery test system (Neware, BTS) and were carried out at room temperature.

[0044] The electrochemical cycle performance of the full battery composed of the samples of Example 1 and Comparative Example 1 at a current density of 0.05 A / g is as follows: Figure 6 and Figure 7As shown, the first cycle discharge capacity of the full battery composed of the sample of Example 1 is 69.6mAh / g, and after 100 cycles it is 55.2mAh / g; while the first cycle discharge capacity of the full battery composed of the sample of Comparative Example 1 is 46.1mAh / g, and after 100 cycles it is 10mAh / g. From the electrochemical cycle characterization, after 100 cycles, the full battery of Example 1 still exhibits a larger specific capacity than that of Comparative Example 1, and provides a high capacity retention rate. It can be seen that the three-dimensional nanoflower-like TiHCF material has good stability, and the structure of the nanosheet effectively slows down the change in volume during the charge and discharge process, thereby significantly improving the cycle performance.

[0045] The rate performance of the full battery composed of Example 1 is as follows Figure 8 As shown, when the current density is 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5A / g, the reversible capacity of the full battery is 63, 60, 55, 50, 40 and 33mAh / g respectively. When the current density returns to 0.05A / g, the average discharge specific capacity is restored to 63mAh / g, reflecting excellent rate performance.

[0046] In summary, the preparation method of the battery positive electrode material provided by the present invention has simple process operation, and the battery positive electrode material is a flower-like structure assembled from two-dimensional nanosheets, which can not only ensure good structural stability, but also effectively slow down the volume change during the charge and discharge process, thereby significantly improving the charge and discharge cycle performance and ion migration rate. The prepared battery positive electrode material is used in an aqueous zinc ion battery, and the cycle stability is high, and the electrochemical performance is better than that of nano-granular electrode materials.

[0047] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional nanoflower-shaped titanium-based Prussian blue analog electrode material assembled by nanosheets, characterized in that: The glacial acetic acid / ethanol solution of tetrabutyl titanate and the ferrocyanide solution are mixed evenly, and the precipitate is collected after heating reaction to obtain the three-dimensional nanoflower-shaped titanium-based Prussian blue analog electrode material assembled by the nanosheets; The ferrocyanide solution includes one or more of potassium ferrocyanide solution, potassium ferrocyanide solution, sodium ferrocyanide solution and sodium ferrocyanide solution; The pH of the ferrocyanide solution is less than 3; In the glacial acetic acid / ethanol solution of tetrabutyl titanate, the volume ratio of glacial acetic acid to ethanol is (0.5-2):50; The heating reaction is carried out at 50-60° C. for 3-8 hours.

2. The method for preparing a nanosheet-assembled three-dimensional nanoflower-shaped titanium-based Prussian blue analog electrode material according to claim 1, characterized in that: The molar ratio of tetrabutyl titanate in the glacial acetic acid / ethanol solution of tetrabutyl titanate to ferrocyanide ions in the ferrocyanide solution is (1-2):

2.

3. The method for preparing a nanosheet-assembled three-dimensional nanoflower-shaped titanium-based Prussian blue analog electrode material according to claim 1, wherein after the heating reaction is completed, the material is allowed to stand for a period of time to precipitate.

4. A three-dimensional nanoflower-shaped titanium-based Prussian blue analog electrode material assembled by the preparation method according to any one of claims 1 to 3.

5. The three-dimensional nanoflower-shaped titanium-based Prussian blue analog electrode material assembled by nanosheets as described in claim 4 is used to prepare the positive electrode of an aqueous zinc ion battery.

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