Ammonium vanadate positive electrode material and preparation method and application thereof

Abstract

The application relates to the technical field of water-based zinc ion battery positive electrode materials, in particular to an ammonium vanadate positive electrode material and a preparation method and application thereof. The application provides a preparation method of an ammonium vanadate positive electrode material, which comprises the following steps: mixing an ammonium metavanadate solution and gas-phase grown carbon fibers, then adding cyclodextrin and anhydrous oxalic acid in sequence, carrying out a hydrothermal reaction, and obtaining the ammonium vanadate positive electrode material. The ammonium vanadate positive electrode material prepared by the method has excellent cycle stability and rate performance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of water-based zinc ion battery positive electrode materials, in particular to an ammonium vanadate positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Water-based zinc ion batteries have the advantages of high theoretical specific capacity, low redox potential, safety and reliability, environmental friendliness and the like, and are a promising large-scale energy storage technology. Ammonium vanadate is one of the important positive electrode material development objects of water-based zinc ion batteries due to its stable layered structure and excellent theoretical specific capacity. Although vanadium-based materials exhibit high capacity and excellent cycle stability as water-based rechargeable zinc battery positive electrodes, the strong interaction between the vanadium-based materials and zinc ions and the poor reaction kinetics caused by the poor conductivity of the vanadium-based materials result in poor cycle performance of the vanadium-based materials at a large current density. SUMMARY

[0003] The application aims to provide an ammonium vanadate positive electrode material and a preparation method and application thereof, and the ammonium vanadate positive electrode material prepared by the preparation method has excellent cycle stability and rate performance.

[0004] In order to achieve the above application purposes, the application provides the following technical solutions.

[0005] The application provides a preparation method of an ammonium vanadate positive electrode material, which comprises the following steps.

[0006] The ammonium metavanadate solution and the vapor-grown carbon fiber are mixed, then cyclodextrin and anhydrous oxalic acid are added in sequence, and a hydrothermal reaction is performed to obtain the ammonium vanadate positive electrode material.

[0007] Preferably, the concentration of the ammonium metavanadate solution is 5-20 g / L.

[0008] The ammonium metavanadate solution is obtained by mixing ammonium metavanadate and water and then performing water bath stirring.

[0009] Preferably, the temperature of the water bath stirring is 40-70 DEG C, the stirring speed of the water bath stirring is 1000-3000 rpm, and the time is 10-30 min.

[0010] Preferably, the concentration of the vapor-grown carbon fiber in the mixed solution obtained after the mixing is 1-10 g / L.

[0011] The mixing comprises water bath stirring and ultrasonic treatment in sequence, the temperature of the water bath stirring is 40-70 DEG C, the stirring speed of the water bath stirring is 1000-3000 rpm, and the time is 10-30 min.

[0012] The power of the ultrasonic treatment is 200-400 W, and the time is 10-30 min.

[0013] Preferably, the concentration of the cyclodextrin in the mixture obtained after adding the cyclodextrin is 5-30 g / L.

[0014] After adding the cyclodextrin, water bath stirring is further included, the temperature of the water bath stirring is 40-70℃, the rotating speed is 1000-3000 rpm, and the time is 1-2 h.

[0015] Preferably, the concentration of the anhydrous oxalic acid in the mixture obtained after adding the anhydrous oxalic acid is 5-30 g / L.

[0016] After adding the anhydrous oxalic acid, water bath stirring is further included, the temperature of the water bath stirring is 40-70℃, the rotating speed is 1000-3000 rpm, and the time is 15-35 min.

[0017] Preferably, the volume filling ratio of the hydrothermal reaction is 60-70%, the temperature is 120-200℃, and the time is 300-600 min.

[0018] Preferably, after the hydrothermal reaction is completed, washing, centrifugation, drying and cooling are sequentially performed.

[0019] The application further provides an ammonium vanadate positive electrode material prepared by the preparation method.

[0020] The application further provides an application of the ammonium vanadate positive electrode material in a water-based zinc ion battery.

[0021] The application provides a preparation method of an ammonium vanadate positive electrode material, including the following steps: mixing an ammonium metavanadate solution and gas phase growth carbon fiber, sequentially adding cyclodextrin and anhydrous oxalic acid, and performing hydrothermal reaction to obtain the ammonium vanadate positive electrode material. The application realizes bonding and compounding of the ammonium metavanadate and the gas phase growth carbon fiber by the hydrothermal method, which is beneficial to reducing the reaction temperature, saving energy, and has no waste emission in the whole reaction process, and is beneficial to environmental protection. The microstructure of the ammonium vanadate positive electrode material prepared by the application is that flaky ammonium vanadate is uniformly and in situ grown on the gas phase growth carbon fiber, the flaky ammonium vanadate provides more active sites for zinc ion deintercalation, enables active substances to more fully contact with electrolyte, promotes zinc ion intercalation and deintercalation, solves the problem of poor conductivity of the ammonium vanadate, and thus improves the electrochemical performance of the material. The application improves the intrinsic conductivity of the ammonium vanadate by compounding with the gas phase growth carbon fiber, enhances the electrochemical dynamics, and thus improves the cycle stability and capacity. Meanwhile, the preparation method of the application is simple, fast and easy to control, the ammonium vanadate positive electrode material prepared by the preparation method has uniform chemical composition, and has a good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 XRD pattern of the ammonium vanadate positive electrode material and ammonium vanadate described in Example 1;

[0023] Figure 2 SEM pattern of the ammonium vanadate positive electrode material described in Example 1;

[0024] Figure 3 XRD pattern of the ammonium vanadate positive electrode material described in Example 2;

[0025] Figure 4 SEM pattern of the ammonium vanadate positive electrode material described in Example 2;

[0026] Figure 5 EIS of the ammonium vanadate positive electrode material described in Example 1 for aqueous zinc ion battery;

[0027] Figure 6 CV of the ammonium vanadate positive electrode material described in Example 1 for aqueous zinc ion battery;

[0028] Figure 7 Cycle performance curve of the ammonium vanadate positive electrode material described in Example 1 for aqueous zinc ion battery at a current density of 5 A·g -1

[0029] Figure 8 EIS of the ammonium vanadate positive electrode material described in Example 2 for aqueous zinc ion battery;

[0030] Figure 9 CV of the ammonium vanadate positive electrode material described in Example 2 for aqueous zinc ion battery;

[0031] Figure 10 Cycle performance curve of the ammonium vanadate positive electrode material described in Example 2 for aqueous zinc ion battery at a current density of 5 A·g -1 DETAILED DESCRIPTION

[0032] The present application provides a preparation method of an ammonium vanadate positive electrode material, comprising the following steps:

[0033] After mixing the ammonium metavanadate solution and the vapor-grown carbon fiber, the cyclodextrin and anhydrous oxalic acid are sequentially added, and a hydrothermal reaction is performed to obtain the ammonium vanadate positive electrode material.

[0034] In the present application, all the preparation raw materials are commercially available products well known to those skilled in the art, unless otherwise specified.

[0035] ​​In the present application, the concentration of the ammonium metavanadate solution is preferably 5-20 g / L, more preferably 8-16 g / L. In the present application, the ammonium metavanadate solution is preferably prepared by mixing ammonium metavanadate and water, and then stirring in a water bath. In the present application, the water is preferably deionized water; the temperature of the water bath stirring is preferably 40-70°C, more preferably 50-60°C; the stirring speed of the water bath is preferably 1000-3000 rpm, more preferably 1500-2500 rpm; and the stirring time is preferably 10-30 min, more preferably 15-25 min. In the embodiments of the present application, the concentration of the ammonium metavanadate solution can be 11.79 g / L or 13.1 g / L; the temperature of the water bath stirring can be 60°C; the stirring speed of the water bath can be 1000 rpm or 1200 rpm; and the stirring time of the water bath can be 20 min.

[0036] In the present application, the concentration of the gas-phase grown carbon fibers in the mixed solution obtained after the mixing is preferably 1-10 g / L, more preferably 3-7 g / L; and the mixing preferably comprises water bath stirring and ultrasonic treatment in sequence. The temperature of the water bath stirring is preferably 40-70°C, more preferably 50-60°C; the stirring speed of the water bath is preferably 1000-3000 rpm, more preferably 1500-2500 rpm; and the stirring time is preferably 10-30 min, more preferably 15-25 min. In the embodiments of the present application, the concentration of the gas-phase grown carbon fibers in the mixed solution obtained after the mixing can be 4.4 g / L; the temperature of the water bath stirring can be 60°C or 65°C; the stirring speed of the water bath can be 1200 rpm; and the stirring time of the water bath can be 10 min or 20 min. In the present application, the power of the ultrasonic treatment is preferably 200-400 W, more preferably 250-350 W; and the treatment time is preferably 10-30 min, more preferably 15-25 min. In the embodiments of the present application, the power of the ultrasonic treatment can be 300 W; and the treatment time can be 20 min.

[0037] In the present application, the concentration of the cyclodextrin in the mixture obtained after adding the cyclodextrin is preferably 5-30 g / L, and more preferably 10-20 g / L; the present application does not have any special limitation on the adding mode of the cyclodextrin, and any adding mode known to those skilled in the art can be adopted. In the present application, water bath stirring is preferably adopted after adding the cyclodextrin, the temperature of the water bath stirring is preferably 40-70℃, and more preferably 50-60℃; the rotating speed is preferably 1000-3000 rpm, and more preferably 1500-2500 rpm; and the time is preferably 1-2 h. In the examples of the present application, the concentration of the cyclodextrin in the mixture obtained after adding the cyclodextrin can be 15 g / L; the temperature of the water bath stirring can be 60℃ or 65℃, the rotating speed can be 1500 rpm, and the time can be 1 h or 2 h. In the present application, the cyclodextrin is a surfactant, which plays a role in reducing the surface tension.

[0038] In the present application, the concentration of the anhydrous oxalic acid in the mixture obtained after adding the anhydrous oxalic acid is preferably 5-30 g / L, and more preferably 10-20 g / L; the present application does not have any special limitation on the adding mode of the anhydrous oxalic acid, and any adding mode known to those skilled in the art can be adopted. Water bath stirring is preferably adopted after adding the anhydrous oxalic acid, the temperature of the water bath stirring is preferably 40-70℃, and more preferably 50-60℃; the rotating speed is preferably 1000-3000 rpm, and more preferably 1500-2500 rpm; and the time is preferably 15-35 min, and more preferably 20-30 min. In the examples of the present application, the concentration of the anhydrous oxalic acid in the mixture obtained after adding the anhydrous oxalic acid can be 15 g / L; the temperature of the water bath stirring can be 60℃ or 65℃, the rotating speed can be 2000 rpm, and the time can be 20 min. In the present application, the anhydrous oxalic acid plays a role in adjusting the pH value of the solution.

[0039] In the present application, the volume filling ratio of the hydrothermal reaction is preferably 60-70%, and more preferably 63-66%; the temperature is preferably 120-200℃, and more preferably 120℃; and the time is preferably 300-600 min, and more preferably 300 min. In the present application, the hydrothermal reaction is preferably carried out in a reaction kettle with the inner lining material being polytetrafluoroethylene.

[0040] After the hydrothermal reaction is completed, the application further preferably comprises sequentially performed first cooling, washing, centrifugation, drying, second cooling and grinding. In the application, the washing is preferably 6 times of alternating washing of the suspension with deionized water and anhydrous ethanol, and after each washing is completed, centrifugation is preferably performed and the supernatant waste liquid is preferably discarded. In the application, the rotation speed of the centrifugation is preferably 3000-3500 rpm, more preferably 3100-3400 rpm; the time of each centrifugation is preferably 3-6 min, more preferably 4-5 min. In the embodiment of the application, the rotation speed of the centrifugation can be 3200 rpm, and the time of each centrifugation can be 5 min. In the application, the drying is preferably vacuum drying, the temperature of the vacuum drying is preferably 60-85℃, more preferably 65-80℃; the time of the vacuum drying is preferably 10-20 h, more preferably 13-16 h. In the embodiment of the application, the temperature of the vacuum drying can be 75℃ or 80℃, and the time can be 12 h. The application does not have any special limitation on the process of the first cooling and the second cooling, and a process well known to those skilled in the art can be used. The application does not have any special limitation on the process of the grinding, and a process well known to those skilled in the art can be used.

[0041] The application further provides an ammonium vanadate positive electrode material prepared by the preparation method described in the above technical solution, comprising gas phase grown carbon fibers and flaky ammonium metavanadate grown in situ on surfaces of the gas phase grown carbon fibers.

[0042] In the application, the molar ratio of the gas phase grown carbon fibers and the flaky ammonium metavanadate is preferably 1-10:1, more preferably 1-3:1. In the embodiment of the application, the molar ratio of the gas phase grown carbon fibers and the flaky ammonium metavanadate can be 2:1.

[0043] The application further provides an application of the ammonium vanadate positive electrode material described in the above technical solution in an aqueous zinc ion battery. The application does not have any special limitation on the method of the application, and a method well known to those skilled in the art can be used.

[0044] The ammonium vanadate positive electrode material, the preparation method and the application thereof provided by the application are described in detail below in combination with embodiments, but they should not be understood as limitations on the protection scope of the application.

[0045] Embodiment 1

[0046] 15 mmol of ammonium metavanadate (NH4VO3, 1.769 g) was dissolved in 150 mL of deionized water, stirred at 60℃ for 20 min (rotation speed was 1000 rpm) to obtain an ammonium metavanadate solution (orange, concentration was 11.79 g / L);

[0047] In the ammonium metavanadate solution, 0.5 g of vapor grown carbon fiber (the concentration of vapor grown fiber in the mixed solution was 3.33 g / L) was added, and after stirring at 60°C for 10 min (the rotation speed was 1200 rpm), ultrasonic treatment was performed for 20 min (the power was 300 W). Then, 2 mmol of cyclodextrin (the concentration of cyclodextrin in the mixed solution was 15.12 g / L) was added, and stirring was performed at 60°C for 1 h (the rotation speed was 1500 rpm). Then, 25 mmol of anhydrous oxalic acid (the concentration of anhydrous oxalic acid in the mixed solution was 15 g / L) was added, and stirring was performed at 60°C for 20 min (the rotation speed was 1500 rpm). The obtained mixed solution was placed in a hydrothermal reaction kettle (the volume filling ratio was 68%), and the hydrothermal reaction kettle containing the mixed solution was placed in an electric oven, which was heated from room temperature to 120°C and kept for 300 min. After natural cooling to room temperature, the suspension in the hydrothermal reaction kettle was washed with deionized water and anhydrous ethanol alternately for 6 times. After each washing, the powder product was separated by centrifugation, and then dried in an electric vacuum drying box at 80°C for 12 h. After cooling to room temperature, the product was fully ground to obtain an ammonium vanadate positive electrode material (denoted as NH4V4O10VGCF). 10 @The molar ratio of VGCF, vapor grown carbon fiber, and sheet-shaped ammonium metavanadate was 2:1;

[0048] Figure 1 The XRD pattern of the ammonium vanadate and the ammonium vanadate positive electrode material was as shown in FIG. 2. Figure 1 It can be seen that the addition of VGCF did not change the crystal structure of ammonium vanadate.

[0049] Figure 2 The SEM pattern of the ammonium vanadate positive electrode material was as shown in FIG. 3. Figure 2 It can be seen that the ammonium vanadate was uniformly distributed on the surface of VGCF, forming a uniform ammonium vanadate positive electrode material.

[0050] Example 2

[0051] 20 mmol of ammonium metavanadate (NH4VO3, 2.359 g) was dissolved in 180 mL of deionized water, and stirring was performed at 60°C for 20 min (the rotation speed was 1200 rpm) to obtain an ammonium metavanadate solution (orange, the concentration was 13.1 g / L).

[0052] Add 0.8 g of vapor-grown carbon fiber (VGCF) (concentration of VGCF in the mixture is 4.4 g / L) to the ammonium metavanadate solution, stir in a 65°C water bath for 20 min (1200 rpm), sonicate for 20 min (300 W), add 2.5 mmol of cyclodextrin (concentration of cyclodextrin in the mixture is 15.76 g / L), stir in a 65°C water bath for 2 h (1600 rpm), add 30 mmol of anhydrous oxalic acid (concentration of anhydrous oxalic acid in the mixture is 15 g / L), stir in a 65°C water bath for 20 min (1600 rpm). The obtained mixture was placed in a hydrothermal reactor (volume filling ratio of 65%), and the reactor containing the mixture was placed in an electric oven. The temperature was raised from room temperature to 120°C and maintained for 300 min. After natural cooling to room temperature, the suspension in the hydrothermal reactor was washed six times alternately with deionized water and anhydrous ethanol. After each washing, the product was centrifuged to obtain powder (centrifugation speed of 3300 rpm, centrifugation time of 5 min each time). The powder was then dried in a 75°C electric vacuum drying oven for 12 h. After cooling to room temperature, it was thoroughly ground to obtain ammonium vanadate cathode material (denoted as ②NH4V4O). 10 @VGCF, the molar ratio of vapor-grown carbon fiber to sheet-like ammonium metavanadate is 2.5:1;

[0053] Figure 3 The XRD patterns of ammonium vanadate and ammonium vanadate cathode materials are shown below. Figure 3 It can be seen that the addition of VGCF did not change the crystal structure of ammonium vanadate.

[0054] Figure 4 Here is a SEM image of the ammonium vanadate cathode material, from... Figure 4 It can be seen that ammonium vanadate is uniformly distributed on the surface of VGCF, forming a uniform ammonium vanadate@VGCF composite material.

[0055] Test case

[0056] The ammonium vanadate cathode material described in Examples 1 and 2 is used in an aqueous zinc-ion battery, and the specific method is as follows:

[0057] The ammonium vanadate positive electrode material described in Examples 1-2 is mixed with conductive carbon and polyvinylidene fluoride in a mass ratio of 7:2:1, N-dimethylpyrrolidine is used as a diluent, and the mixture is thoroughly ground to make it uniform. The uniformly mixed slurry is drop-coated on the surface of a 10 mm diameter stainless steel mesh foil, vacuum dried at 80°C for 12 hours, and the surface of each electrode is loaded with 1-3 mg of ammonium vanadate positive electrode material. A 12 mm diameter and 10 μm thick zinc foil is used as the negative electrode, a glass fiber separator is used as the separator, and 80 μL of zinc triflate is added as the electrolyte. A standard CR2032 battery is assembled and tested using a LAND-CT2001A battery testing system. The full battery is tested for charge and discharge at a current density of 5 A·g -1 ) in the voltage range of 0.3-1.6 V.

[0058] Figure 5 The AC impedance plot (EIS) of the ammonium vanadate positive electrode material described in Example 1 for a water-based zinc ion battery is shown in Figure 5 , which shows that the impedance of the battery is about 80 ohms.

[0059] Figure 6 The cyclic voltammetry plot (CV) of the ammonium vanadate positive electrode material described in Example 1 for a water-based zinc ion battery is shown in Figure 6 , which shows that the two pairs of redox peaks are very obvious, and the electrochemical activity is very high.

[0060] Figure 7 The cycle performance plot of the ammonium vanadate and the ammonium vanadate positive electrode material described in Example 1 for a water-based zinc ion battery at a current density of 5 A·g -1 is shown in Figure 7 , which shows that the rate performance and cycle performance of the battery containing the gas-phase grown carbon fiber ammonium vanadate positive electrode material have been greatly improved.

[0061] Figure 8 The AC impedance plot (EIS) of the ammonium vanadate positive electrode material described in Example 2 for a water-based zinc ion battery is shown in Figure 8 , which shows that the impedance of the battery is about 80 ohms.

[0062] Figure 9 The cyclic voltammetry plot (CV) of the ammonium vanadate positive electrode material described in Example 2 for a water-based zinc ion battery is shown in Figure 9 , which shows that the two pairs of redox peaks are very obvious, and the electrochemical activity is very high.

[0063] Figure 10 The cycle performance plot of the ammonium vanadate and the ammonium vanadate positive electrode material described in Example 2 for a water-based zinc ion battery at a current density of 5 A·g -1 is shown in Figure 10 , which shows that the rate performance and cycle performance of the battery containing the gas-phase grown carbon fiber ammonium vanadate positive electrode material have been greatly improved.

[0064] The above merely describes the preferred embodiments of the present application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method for preparing an ammonium vanadate cathode material, characterized in that, Includes the following steps: Ammonium metavanadate solution and vapor-grown carbon fibers were mixed, and cyclodextrin and anhydrous oxalic acid were added sequentially to carry out a hydrothermal reaction to obtain the ammonium metavanadate cathode material; The concentration of vapor-grown carbon fibers in the mixture obtained after mixing is 1~10 g / L; The mixing process includes sequential water bath stirring and ultrasonication. The temperature of the water bath stirring is 40~70℃, the speed of the water bath stirring is 1000~3000rpm, and the time is 10~30min. The ultrasound power is 200~400W, and the duration is 10~30min; The volumetric filling ratio of the hydrothermal reaction is 60-70%, the temperature is 120-200℃, and the time is 300-600 min.

2. The preparation method according to claim 1, characterized in that, The concentration of the ammonium metavanadate solution is 5~20 g / L; The ammonium metavanadate solution is prepared by mixing ammonium metavanadate and water and then stirring in a water bath.

3. The preparation method according to claim 2, characterized in that, The temperature of the water bath stirring is 40~70℃, the speed of the water bath stirring is 1000~3000rpm, and the time is 10~30min.

4. The preparation method according to claim 1, characterized in that, The concentration of cyclodextrin in the mixture obtained after adding the cyclodextrin is 5~30 g / L; The process includes water bath stirring after adding the cyclodextrin. The water bath stirring temperature is 40~70℃, the speed is 1000~3000rpm, and the time is 1~2h.

5. The preparation method according to claim 1, characterized in that, The concentration of anhydrous oxalic acid in the mixture obtained after adding the anhydrous oxalic acid is 5~30 g / L; The process includes adding anhydrous oxalic acid followed by water bath stirring, wherein the temperature of the water bath stirring is 40~70℃, the speed is 1000~3000rpm, and the time is 15~35min.

6. The preparation method according to claim 1, characterized in that, After the hydrothermal reaction is completed, the process also includes washing, centrifugation, drying, and cooling in sequence.

7. The ammonium vanadate cathode material prepared by the preparation method according to any one of claims 1 to 6, characterized in that, It includes vapor-grown carbon fibers and sheet-like ammonium vanadate grown in situ on the surface of the vapor-grown carbon fibers.

8. The application of the ammonium vanadate cathode material according to claim 7 in an aqueous zinc-ion battery.

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