Surface amorphous ammonium vanadate material as well as preparation method and application thereof

Abstract

The invention provides a surface amorphous ammonium vanadate material as well as a preparation method and application thereof, and relates to the technical field of ammonium ion batteries. The preparation method of the ammonium vanadate material comprises the following steps: S1, dispersing V2O5 in an organic solvent, adding a proper amount of water, and stirring to obtain a mixed solution; s2, after the mixed solution is subjected to a hydrothermal reaction, a reaction product is washed and dried, and VO2 is obtained; s3, VO2 and a NaBH4 solution are mixed, and a vanadium oxide material is obtained after suction filtration and drying; and S4, embedding ammonium ions into the vanadium oxide material in situ through electrochemical driving to prepare the surface amorphous ammonium vanadate material. The prepared surface amorphous ammonium vanadate material has more active sites, and the electrochemical performance of the material is improved. And secondly, the process of in-situ embedding ammonium ions is electrochemically driven, so that the composition and the structure of the material can be accurately regulated and controlled, and the ion transmission efficiency in the material can be enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonium ion batteries, and particularly to a surface amorphous ammonium vanadate material, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of globalization and industrialization, the demand for energy around the world is growing rapidly. Finding new renewable, clean, and efficient energy sources has become a major challenge for human society. In recent years, lithium-ion batteries have been widely used in portable devices and electric vehicles due to their high energy density and long cycle performance. However, lithium-ion batteries face challenges in terms of safety, cost, and resource sustainability in large-scale energy storage systems, especially the risk of thermal runaway and high manufacturing costs.

[0003] Aqueous rechargeable batteries have very good prospects in next-generation batteries due to their advantages such as easy manufacturing, low cost, environmental friendliness, and high ionic conductivity. Among them, ammonium ions, as non-metallic charge carriers, operate under neutral or weakly acidic conditions, possessing safety, non-toxicity, and ecological friendliness, and their smaller hydrated ion radius and lower molar mass are conducive to rapid diffusion in solution.

[0004] Although ammonium ion batteries have many advantages, the lack of suitable electrode materials is still the key limiting their development at present. Currently, the research on ammonium ion electrode materials mainly focuses on Prussian blue analogs, transition metal oxides, and organic compounds. Among them, vanadium-based materials have rich oxidation states, easy regulation of the material lattice space, and high theoretical capacity, making them ideal candidates for ammonium ion battery electrode materials. However, due to the relatively large volume of ammonium ions, when vanadium oxides are used as ammonium ion battery materials, there are problems such as unstable layered structures and low electronic conductivity, resulting in poor cycle capacity and stability. Summary of the Invention

[0005] In view of this, the present invention provides a surface amorphous ammonium vanadate material with a simple synthesis process, short operation cycle, and excellent ammonium storage performance, a preparation method thereof, and an application thereof.

[0006] In a first aspect, the present invention provides a preparation method of a surface amorphous ammonium vanadate material, comprising the following steps:

[0007] S1. Disperse vanadium pentoxide (V2O5) in an organic solvent, add an appropriate amount of water, and stir to obtain a mixed solution;

[0008] S2. After performing a hydrothermal reaction on the mixed solution in step S1, wash and dry the reaction product to obtain crystalline vanadium oxide (VO2);

[0009] S3. Add the crystalline vanadium oxide obtained in step S2 into a sodium borohydride (NaBH4) solution, perform ultrasonic oscillation, and after suction filtration and drying, a surface amorphous vanadium oxide material is obtained;

[0010] S4. Electrochemically drive the in-situ embedding of ammonium ions into the surface amorphous vanadium oxide material obtained in step S3 to prepare a surface amorphous ammonium vanadate material.

[0011] In one or some possible embodiments, in step S1, the concentration of vanadium pentoxide in the dispersion is 2.5 - 5 mM; the organic solvent is selected from at least one of ethanol, ethylene glycol, and isopropanol; the volume ratio of the organic solvent to the water is 4:3.

[0012] In one or some possible embodiments, the stirring temperature is 20 - 30 °C and the stirring time is 30 - 60 min.

[0013] In one or some possible embodiments, in step S2, the temperature condition of the hydrothermal reaction is 150 - 180 °C and the time is 20 - 26 h; the drying temperature is 60 - 80 °C and the time is not less than 12 h.

[0014] In one or some possible embodiments, the washing method is: wash with water and ethanol at least three times in sequence.

[0015] In one or some possible embodiments, in step S3, the concentration of the sodium borohydride solution is 1 - 5 mol / L and the ultrasonic oscillation time is 3 - 5 h.

[0016] In one or some possible embodiments, the suction filtration conditions are: suction filter with water and ethanol at least 3 times respectively, and the volume of the solvent used each time is 280 - 320 mL.

[0017] In one or some possible embodiments, in step S4, the in-situ embedding of ammonium ions into the surface amorphous vanadium oxide material obtained in step S3 specifically includes:

[0018] Immerse the surface amorphous vanadium oxide material obtained in step S3 in an ammonium salt electrolyte solution, and electrochemically drive the embedding of ammonium ions into the surface amorphous vanadium oxide material to prepare a surface amorphous ammonium vanadate material.

[0019] In one or some possible embodiments, the ammonium salt electrolyte is selected from one of ammonium sulfate, ammonium acetate, or ammonium trifluoromethanesulfonate, and the concentration is 1 M - 2 M.

[0020] In one or some possible embodiments, the electrochemically driving conditions include: the voltage range is -0.7 V - 0.3 V and the current density is 0.1 A / g - 0.5 A / g.

[0021] Second aspect, the present invention relates to a surface amorphous ammonium vanadate material prepared by the above preparation method.

[0022] Third aspect, the present invention relates to the application of the surface amorphous ammonium vanadate material in an ammonium ion battery.

[0023] Fourth aspect, the present invention provides an ammonium ion battery, including a negative electrode material, and the negative electrode material includes the above surface amorphous ammonium vanadate material.

[0024] Fifth aspect, the present invention provides a method for preparing an ammonium ion battery, including the following steps:

[0025] Using the above surface amorphous ammonium vanadate material as a working electrode, assembling it with a saturated calomel reference electrode and an activated carbon counter electrode to obtain an ammonium ion battery.

[0026] The surface amorphous ammonium vanadate material, its preparation method and application provided by the present invention have the following beneficial effects compared with the prior art:

[0027] (1) The surface amorphous ammonium vanadate material prepared by the present invention has a larger number of active sites, which is beneficial to improving the electrochemical performance of the material. Secondly, through the process of electrochemically driven in-situ embedding of ammonium ions, it not only helps to precisely regulate the composition and structure of the material, but also enhances the ion transport efficiency inside the material.

[0028] (2) The surface amorphous ammonium vanadate material prepared by the present invention can show more excellent performance in energy storage devices such as batteries or supercapacitors.

[0029] (3) When the surface amorphous ammonium vanadate material of the present invention stores ammonium ions, the surface amorphous modified vanadium oxide exhibits a longer cycle life, and the ammonium ion battery prepared from this material has a higher energy density, better cycle stability and rate performance.

[0030] (4) The method for preparing the surface amorphous ammonium vanadate material of the present invention effectively introduces ammonium ions into the structure of the electrode material through an electrochemical pre-embedding process, providing more diffusion sites. By adopting the design of amorphous and crystalline heterojunction, the volume expansion caused by pre-embedding is alleviated. At the same time, the conductivity of the electrode material is improved, the structural stability is enhanced, the volume change during charge and discharge is reduced, and the ion diffusion efficiency of the electrode is improved.

[0031] (5) The ammonium ion battery prepared by using the surface amorphous ammonium vanadate material of the present invention can control the change rate of the interlayer spacing of the electrode material within 0.5%. Compared with the interlayer spacing of the ammonium ion battery electrode material prepared by the prior art exceeding 2.3%, this improvement significantly improves the stability and cycle life of the battery. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0033] Figure 1 SEM diagrams of the vanadium oxide materials prepared in Example 1 of the present invention and Comparative Example 1;

[0034] Figure 2 TEM diagrams of the vanadium oxide materials prepared in Example 1 of the present invention and Comparative Example 1;

[0035] Figure 3 EPR diagrams of the vanadium oxide materials prepared in Examples 1 - 3 of the present invention and Comparative Example 3;

[0036] Figure 4 XRD diagrams of the vanadium oxide materials prepared in Example 1 of the present invention and Comparative Example 3;

[0037] Figure 5 Electrochemical impedance spectra and Warburg coefficient diagrams of the ammonium ion batteries prepared in Example 1 of the present invention and Comparative Example 3;

[0038] Figure 6 Electronic conductivity diagrams of the ammonium ion batteries prepared in Example 1 of the present invention and Comparative Example 3;

[0039] Figure 7 Diagrams of the change in the crystal plane spacing of the vanadium oxide material during the charge and discharge process of the ammonium ion battery prepared in Example 1 of the present invention;

[0040] Figure 8 Diagrams of the change in the crystal plane spacing of the vanadium oxide material during the charge and discharge process of the ammonium ion battery prepared in Comparative Example 3 of the present invention;

[0041] Figure 9 Electrochemical cycling performance diagrams of the ammonium ion batteries prepared in Example 1, Comparative Example 1, and Comparative Example 3 of the present invention;

[0042] Figure 10 Electrochemical cycling performance diagrams of the ammonium ion batteries prepared in Examples 2 - 3 of the present invention;

[0043] Figure 11 Electrochemical cycling performance diagrams of the ammonium ion batteries prepared in Comparative Example 2 of the present invention. Detailed implementation manners

[0044] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0045] When vanadium oxide is used as an electrode material for ammonium ion batteries, due to the large volume characteristics of ammonium ions, the crystal structure is prone to collapse during the insertion and extraction processes, resulting in poor cycle stability and capacity retention. Although the electrochemical pre-insertion of ammonium ions can broaden the overall space of the lattice tunnels in advance, increase the layer spacing and provide more active sites to improve battery performance, its large volume also makes the material structure fragile and prone to collapse, thus causing mechanical failure problems. In response to this challenge, the present invention proposes a surface amorphous ammonium vanadate material: first, an amorphous layer is constructed on the surface of crystalline VO2 through a one-step reduction method, and an internal built-in electric field is formed at the amorphous / crystalline interface, which not only significantly improves the electronic conductivity of the material, but also the large number of ion diffusion channels in the amorphous layer enhance the ionic conductivity. In addition, the elastic amorphous layer can effectively adapt to the lattice expansion and contraction during the ammonium ion insertion process, and as a buffer layer, it alleviates the volume expansion stress caused by the repeated insertion and extraction of ammonium ions, thereby protecting the crystal structure of the material from damage. This design not only enhances the cycle stability of the electrode material, but also accelerates the transmission rate of ammonium ions in the electrode material, ensuring that the electrode can still maintain a high capacity at a high current density.

[0046] The following will further describe the present invention in combination with specific embodiments. The protection scope of the present invention is not limited by the following embodiments. Unless otherwise specified, the main materials involved in the following examples are all commercially available products.

[0047] Example 1

[0048] This example provides a preparation method for a surface amorphous ammonium vanadate material, including the following steps:

[0049] S1. Disperse 0.4 g of V2O5 in 40 mL of ethanol to form a uniform solution, then add 30 mL of water, and stir at room temperature for 30 min to obtain a mixed solution;

[0050] S2. Hydrothermally treat the mixed solution in step S1 at 160 °C for 24 h, wash the reaction product with water and ethanol at least three times respectively, and then dry at 60 °C for 12 h to obtain a crystalline black product VO2;

[0051] S3. Take 100 mg of the black product obtained in step S2 and add it to an aqueous solution of 3M NaBH4. After ultrasonic oscillation for 3 h, filter and wash it at least 3 times with 300 mL of water and ethanol respectively, and then dry it at 60 °C for 12 h to obtain a black product, which is a surface amorphous vanadium oxide material, labeled as LP-VO-3;

[0052] S4. Immerse the above product as a working electrode in a 2M ammonium acetate electrolyte solution. In the voltage range of -0.7V to -0.3V, in-situ embed ammonium ions through electrochemical driving at a current density of 0.5 A / g to obtain a surface amorphous ammonium vanadate material;

[0053] S5. Assemble the surface amorphous ammonium vanadate material obtained in step S4 as a working electrode with a saturated calomel reference electrode and an activated carbon counter electrode to obtain an ammonium ion battery.

[0054] The vanadium oxide material LP-VO-3 prepared in Example 1 was characterized by JES X320 electron paramagnetic resonance, as Figure 3 shown. It can be seen from Figure 3 that there are oxygen defects in the amorphous layer of the vanadium oxide material LP-VO-3 obtained in this example. The oxygen defects provide a large number of active sites and provide a path for ion diffusion.

[0055] Comparative Example 1

[0056] The difference from Example 1 is that the operation of step S3 was not carried out, and the remaining steps remained unchanged, labeled as VO-1.

[0057] The vanadium oxide material LP-VO-3 prepared in Example 1 and VO-1 prepared in Comparative Example 1 were tested by SEM scanning electron microscopy using a JSM-IT800 field emission scanning electron microscope, as Figure 1 shown. It can be seen from Figure 1 that the morphology of the vanadium oxide material LP-VO-3 obtained in this example is the same as that of the VO-1 material synthesized in Comparative Example 1, both of which are nanothin bands, indicating that the lattice reconstruction mentioned in the present invention will not affect the morphology of the electrode material.

[0058] The vanadium oxide material LP-VO-3 prepared in Example 1 and VO-1 prepared in Comparative Example 1 were characterized by TEM transmission electron microscopy using a Talos F200S field emission transmission electron microscope, as Figure 2 shown. It can be seen from Figure 2It can be seen that: compared with the VO-1 material synthesized in Comparative Example 1, the vanadium oxide material LP-VO-3 obtained in this embodiment has clear lattice fringes inside, but within the range of 5 nm on the surface of the vanadium oxide material LP-VO-3 obtained in this embodiment, an amorphous region is also shown, indicating that the NaBH4 etching causes lattice reconstruction on the material surface to form an amorphous thin layer.

[0059] Comparative Example 2

[0060] The difference from Example 1 is that: the operation of step S4 is not carried out, and the remaining steps remain unchanged, which is marked as VO-2.

[0061] Comparative Example 3

[0062] The difference from Example 1 is that: the operation of step S3 is not carried out, and at the same time the operation of step S4 is not carried out, and the remaining steps remain unchanged, which is marked as VO-3.

[0063] The vanadium oxide material VO-3 prepared in Comparative Example 3 was characterized by JES X320 electron paramagnetic resonance, as Figure 3 shown. It can be seen from Figure 3 that: although a small amount of oxygen defects are inevitably introduced during the synthesis process, compared with other embodiments, the content of oxygen defects is very low and can be ignored.

[0064] The vanadium oxide material LP-VO-3 prepared in Example 1 and the vanadium oxide material VO-3 prepared in Comparative Example 3 were subjected to XRD tests using a D2 Discover X-ray diffractometer, as Figure 4 shown. It can be seen from Figure 4 that: after the etching treatment with NaBH4, the vanadium oxide as a whole still maintains its original crystal structure.

[0065] The ammonium ion batteries prepared in Example 1 and the ammonium ion batteries prepared in Comparative Example 3 were subjected to electrochemical impedance spectroscopy tests by EC-lab, and their Warburg coefficients were calculated. The results are as Figure 5 shown.

[0066] It can be seen from Figure 5 that: in Example 1, due to the use of the ammonium vanadate material provided by the present invention, the charge transfer resistance of the final ammonium ion battery is low, while in the ammonium ion battery prepared in Comparative Example 3, the ammonium vanadate material of the present invention is not used, and its charge transfer resistance is as high as 30 Ω. It shows that using the ammonium vanadate material prepared by the present invention to configure an ammonium ion battery can significantly improve the ion migration rate and the electrochemical reaction rate of the material.

[0067] The electronic conductivities of the materials prepared in Example 1 and Comparative Example 3 were tested by a four-probe conductivity tester. It can be seen from Figure 6It can be seen that in Example 1 of the present invention, by means of surface amorphization of the material, the electronic conductivity of the material is significantly improved.

[0068] When performing electrochemical cycling on the ammonium ion batteries prepared in Example 1 and Comparative Example 3, analyze the changes in the crystal plane spacing of the materials prepared in Example 1 and Comparative Example 3 during this process and perform in-situ XRD characterization using a D8 Advance X-ray diffractometer. At the same time, calculate the changes in their crystal plane spacing, as Figure 7 、 8 shown. Test the changes in the crystal plane spacing, as Figure 7 、 8 shown.

[0069] It can be Figure 7 seen that: the crystal plane spacing of the material LP-VO-3 prepared in Example 1 significantly shrinks during charge and discharge, indicating that the amorphous layer inhibits the breathing effect of the electrode material, relieves lattice stress, and effectively inhibits the expansion and contraction of the lattice.

[0070] It can be Figure 8 seen that: for the material VO-3 in Comparative Example 3, due to the lack of surface amorphization reconstruction and ammonium ion pre-embedding, the crystal plane spacing changes greatly during charge and discharge, resulting in the collapse of the structure.

[0071] Example 2

[0072] This example provides a preparation method for a surface amorphous ammonium vanadate material, including the following steps:

[0073] S1. Disperse 0.4 g of V2O5 in 40 mL of ethanol to form a uniform solution, then add 30 mL of water, and stir at room temperature for 45 min to obtain a mixed solution;

[0074] S2. Hydrothermally treat the mixed solution obtained in step S1 at 160 °C for 24 h. Wash the reaction product with water and ethanol at least three times respectively, and then dry at 60 °C for 12 h to obtain a crystalline black product VO2;

[0075] S3. Take 100 mg of the black product obtained in step S2 and add it to a 5 M aqueous solution of NaBH4. After ultrasonic oscillation for 5 h, filter and wash it with 320 mL of water and ethanol at least 3 times respectively, and then dry at 60 °C for 12 h to obtain a black product, which is a surface amorphous vanadium oxide material, labeled as LP-VO-5;

[0076] S4. Immerse the above product as a working electrode in a 2 M ammonium acetate electrolyte solution, and electrochemically drive the in-situ embedding of ammonium ions at a current density of 0.5 A / g within a voltage range of -0.7 V to -0.3 V to obtain a surface amorphous ammonium vanadate material;

[0077] S5. Use the surface amorphous ammonium vanadate material obtained in step S4 as the working electrode, assemble it with a saturated calomel reference electrode and an activated carbon counter electrode to obtain an ammonium ion battery.

[0078] The vanadium oxide material LP-VO-3 of this example was characterized by JES X320 electron paramagnetic resonance, as Figure 3 shown. It can be seen from Figure 3 that: as the concentration of the NaBH4 solution increases, the content of oxygen defects formed increases simultaneously, and the thickness of the amorphous layer increases accordingly.

[0079] Example 3

[0080] This example provides a preparation method of a surface amorphous ammonium vanadate material, including the following steps:

[0081] S1. Disperse 0.4 g of V2O5 in 40 mL of ethanol to form a homogeneous solution, then add 30 mL of water, and stir at room temperature for 45 min to obtain a mixed solution;

[0082] S2. Hydrothermally treat the mixed solution obtained in step S1 at 160 °C for 24 h. Wash the reaction product with water and ethanol at least three times respectively, and then dry at 60 °C for 12 h to obtain a crystalline black product VO2;

[0083] S3. Take 100 mg of the black product obtained in step S2 and add it to a 1 M aqueous solution of NaBH4. After ultrasonic oscillation for 5 h, filter and wash it with 300 mL of water and ethanol at least 3 times respectively, and then dry at 60 °C for 12 h to obtain a black product, which is a surface amorphous vanadium oxide material, labeled as LP-VO-1;

[0084] S4. Immerse the above product as the working electrode in a 2 M ammonium acetate electrolyte solution, and electrochemically drive the in-situ embedding of ammonium ions at a current density of 0.5 A / g within the voltage range of -0.7 V to -0.3 V to obtain a surface amorphous ammonium vanadate material;

[0085] S5. Use the surface amorphous ammonium vanadate material obtained in step S4 as the working electrode, assemble it with a saturated calomel reference electrode and an activated carbon counter electrode to obtain an ammonium ion battery.

[0086] The vanadium oxide material LP-VO-1 of this example was characterized by JES X320 electron paramagnetic resonance, as Figure 3 shown. It can be seen from Figure 3 that: as the concentration of NaBH4 decreases, the content of oxygen defects decreases, and the thickness of the amorphous layer becomes smaller.

[0087] Example 4

[0088] This embodiment provides a method for preparing a surface amorphous ammonium vanadate material, which includes the following steps:

[0089] S1. Disperse 0.18 g of V2O5 in 40 mL of ethanol to form a homogeneous solution, then add 30 mL of water, and stir for 60 min at room temperature to obtain a mixed solution;

[0090] S2. Hydrothermally treat the mixed solution obtained in step S1 at 150 °C for 26 h. Wash the reaction product with water and ethanol at least three times respectively, and then dry it at 70 °C for 12 h to obtain a crystalline black product VO2;

[0091] S3. Take 100 mg of the black product obtained in step S2 and add it to a 2 M aqueous NaBH4 solution. After ultrasonic oscillation for 5 h, filter and wash it with 320 mL of water and ethanol at least 3 times respectively, and then dry it at 70 °C for 12 h to obtain a black product, which is a surface amorphous vanadium oxide material, labeled as LP-VO-2;

[0092] S4. Immerse the above product as a working electrode in a 2 M ammonium sulfate electrolyte solution, and electrochemically drive the in-situ embedding of ammonium ions at a current density of 0.1 A / g within a voltage range of -0.7 V to -0.3 V to obtain a surface amorphous ammonium vanadate material;

[0093] S5. Assemble the surface amorphous ammonium vanadate material obtained in step S4 as a working electrode with a saturated calomel reference electrode and an activated carbon counter electrode to obtain an ammonium ion battery.

[0094] Example 5

[0095] This embodiment provides a method for preparing a surface amorphous ammonium vanadate material, which includes the following steps:

[0096] S1. Disperse 0.4 g of V2O5 in 40 mL of ethanol to form a homogeneous solution, then add 30 mL of water, and stir for 45 min at room temperature to obtain a mixed solution;

[0097] S2. Hydrothermally treat the mixed solution obtained in step S1 at 180 °C for 20 h. Wash the reaction product with water and ethanol at least three times respectively, and then dry it at 75 °C for 14 h to obtain a crystalline black product VO2;

[0098] S3. Take 100 mg of the black product obtained in step S2 and add it to a 2 M aqueous NaBH4 solution. After ultrasonic oscillation for 5 h, filter and wash it with 320 mL of water and ethanol at least 3 times respectively, and then dry it at 75 °C for 14 h to obtain a black product, which is a surface amorphous vanadium oxide material, labeled as LP-VO-2;

[0099] S4. Immerse the above product as the working electrode in a 1 M ammonium trifluoromethanesulfonate electrolyte solution, and electrochemically drive the in-situ embedding of ammonium ions at a current density of 0.3 A / g within the voltage range of -0.7 V to -0.3 V to obtain a surface amorphous ammonium vanadate material;

[0100] S5. Assemble the surface amorphous ammonium vanadate material obtained in step S4 as the working electrode with a saturated calomel reference electrode and an activated carbon counter electrode to obtain an ammonium ion battery.

[0101] Taking the ammonium ion batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 3 as examples, perform constant current charge and discharge tests on them. The test results are as Figures 9 - 11 shown.

[0102] It can be seen from Figures 9 - 11 that: (1) Considering Comparative Examples 1 to 3, when the working electrode of the present invention is not used in the ammonium ion battery, during the cycling process, the structure collapses and the capacity continuously decays for more than 1000 cycles. Although the pre-embedding of the ammonium ion battery prepared in Comparative Example 1 increases its specific capacity, due to the relatively large radius of ammonium ions, the interplanar spacing changes repeatedly during the charge and discharge process, resulting in structural collapse, so that the capacity of the ammonium ion battery rapidly decays in the first 200 cycles. The ammonium ion battery prepared in Comparative Example 2 sacrifices a part of its capacity due to surface amorphous reconstruction. Although the cycling is stable, its specific capacity is low and it is difficult to meet the actual application requirements. (2) Considering Examples 1 to 3: The ammonium ion battery prepared in Example 1 can stably cycle 2000 times at a current density of 2 A g -1 . This shows that when the ammonium vanadate material prepared by the present invention is used as the working electrode, the lattice structure is very stable during the cycling process, which is beneficial to extending the service life of the ammonium ion battery. The cycling performance of the ammonium ion battery prepared in Example 2 is significantly improved during the electrochemical ammonium storage process, but its specific capacity is relatively low, and it is not recommended for actual application. The cycling performance of the ammonium ion battery prepared in Example 3 is slightly improved during the electrochemical ammonium storage process. Although there is still capacity decay, it can meet the actual application requirements. Therefore, the inventor found that: as the concentration of the etching solution increases, the cycling stability of the battery increases, but its specific capacity will decrease. Based on this analysis, the inventor suggests that when the concentration of the NaBH4 solution is further controlled at 1 to 3 M, the comprehensive performance of the ammonium ion battery prepared by the present invention is optimal.

[0103] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a surface amorphous ammonium vanadate material, characterized in that It includes the following steps: S1. Disperse vanadium pentoxide in an organic solvent, add an appropriate amount of water, and stir to obtain a mixed solution; S2. After performing a hydrothermal reaction on the mixed solution in step S1, wash and dry the reaction product to obtain crystalline vanadium oxide; S3. Add the crystalline vanadium oxide in step S2 to a sodium borohydride solution, perform ultrasonic oscillation, filter and dry to obtain a surface amorphous vanadium oxide material; S4. Electrochemically drive to in-situ embed ammonium ions in the surface amorphous vanadium oxide material in step S3 to obtain a surface amorphous ammonium vanadate material.

2. The preparation method of a surface amorphous ammonium vanadate material according to claim 1, characterized in that, In step S1, the concentration of vanadium pentoxide in the dispersion is 2.5 - 5 mM; The organic solvent is selected from at least one of ethanol, ethylene glycol, and isopropanol.

3. The preparation method of a surface amorphous ammonium vanadate material according to claim 2, wherein, The stirring temperature is 20 - 30 °C, and the stirring time is 30 - 60 min.

4. The preparation method of a surface amorphous ammonium vanadate material according to claim 1, characterized in that, In step S2, the temperature condition of the hydrothermal reaction is 150 - 180 °C, and the time is 20 - 26 h; The drying temperature is 60 - 80 °C, and the time is not less than 12 h.

5. The preparation method of a surface amorphous ammonium vanadate material according to claim 1, characterized in that, In step S3, the concentration of the sodium borohydride solution is 1 - 5 mol / L, and the ultrasonic oscillation time is 3 - 5 h.

6. The preparation method of a surface amorphous ammonium vanadate material as claimed in claim 1, wherein, In step S4, the in-situ embedding of ammonium ions in the surface amorphous vanadium oxide material in step S3 specifically includes: Immerse the surface amorphous vanadium oxide material in step S3 in an ammonium salt electrolyte solution, and electrochemically drive to embed ammonium ions on the surface of the surface amorphous vanadium oxide material to obtain a surface amorphous ammonium vanadate material.

7. The preparation method of a surface amorphous ammonium vanadate material according to claim 6, characterized in that, The ammonium salt electrolyte solution is selected from one of ammonium sulfate, ammonium acetate, or ammonium trifluoromethanesulfonate, and the concentration is 1 M - 2 M.

8. The preparation method of a surface amorphous ammonium vanadate material according to claim 6, characterized in that, The electrochemically driving conditions include: the voltage range is -0.7 V - 0.3 V, and the current density is 0.1 A / g - 0.5 A / g.

9. A surface amorphous ammonium vanadate material, characterized in that, Prepared by the preparation method according to any one of claims 1 - 8.

10. Application of a surface amorphous ammonium vanadate material as described in claim 9 in an ammonium ion battery.

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