Two-dimensional vanadium-based nitride electrode material for aqueous ion battery as well as preparation method and application of two-dimensional vanadium-based nitride electrode material

Abstract

The invention belongs to the technical field of electrochemical energy storage, and particularly relates to a two-dimensional vanadium-based nitride electrode material for an aqueous ion battery as well as a preparation method and application of the two-dimensional vanadium-based nitride electrode material. The two-dimensional vanadium-based nitride electrode material is prepared by the following steps: taking V2AlN as a precursor, and adding V2AlN into an etching agent to carry out etching reaction so as to remove an Al layer in the V2AlN and obtain a multi-layer V2N; the method comprises the following steps: dispersing multi-layer V2N in an intercalation agent, carrying out ice-bath ultrasonic treatment to enable the intercalation agent to enter an interlayer structure of the V2N, and expanding the interlayer spacing of the V2N to enable the V2N to be stripped to obtain a single-layer or few-layer V2N nanosheet which is used as a two-dimensional vanadium-based nitride electrode material of an aqueous ion battery. The two-dimensional vanadium-based nitride electrode material disclosed by the invention realizes the high specific capacity of 542.5 mAh / g under the current density of 0.2 A / g, and shows remarkable advantages in the aspects of improving the voltage window, the capacity and the cycling stability of an aqueous ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, and particularly relates to a two-dimensional vanadium-based nitride electrode material for aqueous ion batteries, a preparation method thereof, and an application thereof. Background Art

[0002] With the increasing energy demand, environmentally friendly and efficient energy storage technologies have become a research hotspot. Compared with traditional organic electrolyte lithium-ion batteries, aqueous ion batteries avoid the use of flammable organic solvents, significantly improving the safety of the battery system. In addition, due to the advantages of low cost and environmental friendliness of aqueous ion batteries, they have good development prospects in the new generation of energy storage batteries. However, aqueous ion batteries still face challenges in multiple aspects such as electrochemical window, cycle stability, and energy storage performance. The development of high-performance cathode materials is the key.

[0003] MXenes is a large family of two-dimensional transition metal carbides and nitrides, whose structure consists of two or more layers of transition metal atoms that form a hexagonal structure and are separated by carbon and / or nitrogen layers. The transition metal atoms occupy the octahedral positions between adjacent transition metal layers. MXenes has the general formula M n+1 X n T x , where M is a transition metal, X is carbon and / or nitrogen, and T x represents the terminal group on the outer metal surface. Due to its excellent electrical conductivity, rich surface functional groups, high specific surface area, and open layered structure, MXenes has been increasingly used in the field of cathode materials for metal ion batteries. However, most of the current research is based on carbon-based MXenes materials, and the preparation methods for related nitrogen-based MXenes mostly follow the preparation methods of the carbide system. However, the differences in the material properties between nitrides and carbides make it easy to cause excessive or insufficient etching of the material during the material preparation and synthesis process, making it difficult to obtain a stable layered material, thus limiting its application prospects in the field of electrode materials. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a two-dimensional vanadium-based nitride electrode material for aqueous ion batteries, a preparation method thereof, and an application thereof.

[0005] The first object of the present invention is to provide a preparation method for a two-dimensional vanadium-based nitride electrode material for aqueous ion batteries, comprising the following steps:

[0006] Step 1, etching treatment: Using V 2 AlN as a precursor, adding V 2 AlN to an etchant for etching to remove the Al layer in V 2 AlN, obtaining multi-layered V2 N。

[0007] It should be noted that the present invention introduces V 2 AlN as the precursor of the electrode material. V 2 AlN is a kind of MXenes material, which contains transition metal nitrides of Al and N, has a typical layered structure, and the Al layer and the N layer are connected by weak van der Waals forces. The aluminum atomic layer can be removed by selective etching and other methods to obtain a transition metal nitride V 2 N. V 2 The electron-rich nitrogen atoms in V

[0008] The present invention uses HF in-situ synthesized from fluoride salt and hydrochloric acid as the etchant. Such treatment can effectively reduce the corrosiveness of HF, enabling it to selectively etch V 2 AlN while reducing the damage to the V-N bond, and improving the etching efficiency. Preferably, the fluoride salt is one of lithium fluoride, sodium fluoride, and magnesium fluoride. Preferably, the dosage ratio of hydrochloric acid to fluoride salt is 0.135 mol to 0.27 mol: 1 g to 2 g.

[0009] Preferably, the concentration of hydrochloric acid is 8 mol / L to 10 mol / L, and the concentration of fluoride salt is 33 g / L to 66 g / L.

[0010] Preferably, the etching time is 24 h to 48 h, and the etching temperature is 30 °C to 90 °C.

[0011] The specific operation of the acid etching treatment in the present invention is as follows: Under stirring, fluoride salt is added to hydrochloric acid to obtain an HF etchant; then V 2 AlN is slowly added to the HF etchant for etching to obtain a reaction solution, where the addition of V 2 AlN is completed within 5 min to 10 min; then the reaction product is centrifuged to separate and remove the upper-layer etchant to obtain a precipitate product; the precipitate product is washed at least twice with hydrochloric acid, lithium chloride solution, and deionized water to obtain V 2 N.

[0012] It should be noted that during the washing process, the present invention can effectively neutralize and dissolve the residual acidic substances through hydrochloric acid and lithium chloride solution, remove the by-products and residual acid during the etching process, and prevent the influence of impurities in the subsequent process; then the precipitate product is washed with deionized water until neutral to ensure the purity of the V 2 N product and optimize the effect of the subsequent intercalation and exfoliation steps.

[0013] Step 2. Intercalation and exfoliation treatment: Disperse multi-layered V 2 N in an intercalating agent, and perform ice bath ultrasonic treatment to enable the intercalating agent to enter the interlayer structure of V 2 N, and expand the interlayer spacing of V 2 N to cause exfoliation, obtaining few-layer or single-layer V 2 N nanosheets, which are used as two-dimensional vanadium-based nitride electrode materials for aqueous ion batteries.

[0014] It should be noted that in the present invention, V 2 N is dispersed in an intercalating agent. First, by means of oscillation, the intercalating agent is more evenly distributed in the interlayer of V 2 N, which is helpful for subsequent efficient exfoliation treatment. Subsequently, ultrasonic treatment is carried out under ice bath conditions. Through ultrasonic treatment, the weak binding force between the layered structures in the intercalated V 2 N is destroyed, so that the V 2 N with an increased interlayer spacing is effectively exfoliated to form few-layer or single-layer nanosheets. At the same time, treatment under ice bath conditions is carried out to maintain the stability of the nanosheets and ensure that the thermal effect during ultrasonic treatment is controlled, thereby preventing the nanosheets from re-aggregating or the structure being damaged due to local overheating. Preferably, the ultrasonic time during the ultrasonic exfoliation process is 1 h to 2 h. Then, the ultrasonically exfoliated V 2 N is separated by centrifugation, wherein the rotation speed of centrifugation is 1500 rpm to 2000 rpm, and the centrifugation time is 20 min to 30 min. Finally, in the present invention, the ultrasonically exfoliated V 2 N is freeze-treated at -80 °C for 2 h, and the freeze-treated V 2 N is immediately placed in a freeze dryer for cyclic drying treatment for 24 h to 48 h. This avoids the re-aggregation or structural damage of V 2 N nanosheets during the drying process, ensures the high specific surface area and integrity of V 2 N nanosheets, and obtains two-dimensional vanadium-based nitride electrode materials.

[0015] It also should be noted that by exploring the intercalation effect of the intercalating agent and the exfoliation effect of ice bath ultrasonic treatment, it is found that multi-layered V 2 N can be obtained under the action of a single intercalating agent, but it is difficult to exfoliate to obtain few-layer V 2 N nanosheet materials; without the intercalation treatment of the intercalating agent and only under the exfoliation treatment of single ice bath ultrasonic treatment, V 2 N with a layered structure cannot be obtained. That is to say, it is difficult to obtain few-layer V 2 N nanosheets only through the intercalation treatment of the intercalating agent or only through the exfoliation treatment of ice bath ultrasonic treatment. The present invention realizes the preparation of few-layer V 2 N nanosheets by effectively combining the intercalation effect of the intercalating agent and the exfoliation effect of ice bath ultrasonic treatment.

[0016] The intercalating agent in the present invention is tetrabutylammonium hydroxide, and the mass concentration of the tetrabutylammonium hydroxide solution is 40% to 55%. Since the tetrabutylammonium hydroxide molecule is relatively large, it can enter the gap of the V 2 N layered structure, and increase the interlayer distance of V 2 N by using electrostatic and intermolecular forces.

[0017] The second object of the present invention is to provide a two-dimensional vanadium-based nitride electrode material prepared by the above preparation method.

[0018] The third object of the present invention is to provide the application of the above two-dimensional vanadium-based nitride electrode material in the preparation of an aqueous ion battery, and the two-dimensional vanadium-based nitride electrode material is used as the positive electrode material of the aqueous ion battery.

[0019] Preferably, the aqueous ion battery is divided into various metal ion batteries and non-metal ion batteries, including but not limited to zinc ion batteries, sodium ion batteries, aluminum ion batteries, ammonium ion batteries, proton batteries, and magnesium ion batteries, etc.

[0020] Preferably, the aqueous zinc ion battery is prepared by the following steps:

[0021] Assemble the negative electrode, separator material, electrolyte, and positive electrode in sequence to obtain an aqueous zinc ion battery.

[0022] Preferably, the positive electrode is prepared by the following steps:

[0023] (1) Mix the electrode material of two-dimensional vanadium-based nitride, acetylene black conductive agent, and polyvinylidene fluoride, and then add N-methylpyrrolidone to obtain a slurry; wherein, the mass ratio of the electrode material of vanadium-based nitride compound, acetylene black conductive agent, and polyvinylidene fluoride is 7:2:1, and the mass ratio of N-methylpyrrolidone to the powder slurry is 2:1.

[0024] (2) Uniformly coat the slurry on the carbon paper substrate, cure it, and then punch it to obtain the positive electrode.

[0025] Preferably, the curing temperature is 100°C to 120°C, and the curing time is 10h to 12h;

[0026] Preferably, a punching die with a diameter of 6 mm is used during the punching process, and the punching size is 1.13 cm 2 .

[0027] Preferably, the negative electrode is prepared by the following steps:

[0028] Use sandpaper to polish off the surface impurities and oxides of a zinc foil with a thickness of 0.1 mm to 0.2 mm to obtain the negative electrode.

[0029] Preferably, the electrolyte is zinc trifluoromethanesulfonate, and the concentration of zinc trifluoromethanesulfonate is 1 mol / L.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention uses V 2 AlN as a precursor, adds V 2 AlN to an etchant for etching to remove the Al layer in V 2 AlN, and obtains multi-layered V 2 N; then performs intercalation treatment and ultrasonic exfoliation on the multi-layered V 2 N to make the intercalating agent evenly distributed between the layers of V 2 N, and destroys the weak binding force between the layered structures in the intercalated V 2 N, so that the V 2 N with an increased layer spacing is effectively separated to form few-layer or single-layer nanosheets. Through etching treatment and intercalation exfoliation treatment, the present invention successfully exfoliates bulk V 2 AlN to obtain few-layer or single-layer V 2 N nanosheets, and uses them as electrode materials, achieving a high specific capacity of 542.5 mAh / g at a current density of 0.2 A / g. By utilizing the multi-valence state characteristics of vanadium elements in V 2 N, multi-electron transfer can be realized during the energy storage process, enhancing the zinc storage capacity of the V 2 N electrode material, increasing the energy density of the electrode material, and thus enhancing the electrochemical capacity of the electrode material. At the same time, the successfully synthesized single-layer structure of V 2 N nanosheets provides a higher specific surface area, which not only provides more active sites for the energy storage reaction but also helps to increase the contact area with the electrolyte, shorten the diffusion path of ions inside the electrode material, reduce the transfer impedance, and improve the ion transfer rate.

[0032] In the etching process of the present invention, mild and controllable in-situ synthesized HF is used as an etchant to etch vanadium-based nitrides, which can effectively reduce the corrosiveness of HF, enable it to selectively etch Al atoms in V 2 AlN while reducing the damage to V-N bonds, and improve the etching efficiency; then through intercalation exfoliation treatment, few-layer or single-layer V 2N nanosheet materials have achieved high ionic transport and electrochemical performance. The two-dimensional vanadium-based nitride electrode material of the present invention can maintain stable electrochemical performance at higher voltages in aqueous electrolytes, thereby improving the energy density of the battery. When the scanning rate is 2 mV / s, the specific capacitance of the zinc-ion battery assembled with the two-dimensional vanadium-based nitride electrode material is as high as 579.6 F / g, and a high specific capacity of 542.5 mAh / g is achieved at a current density of 0.2 A / g. At the same time, the zinc-ion battery assembled with the V 2 N electrode material of the present invention can achieve a wide voltage window of up to 1.9 V. In addition, the electrode material maintains stable performance during long-term charge and discharge cycles. After 6000 cycles of charge and discharge, it still has a capacity retention rate of nearly 80%, and the Coulomb efficiency is as high as 100%, demonstrating excellent stability.

[0033] The two-dimensional vanadium-based nitride electrode material of the present invention shows significant advantages in improving the voltage window, specific capacitance, and cycle stability of aqueous ion batteries, providing a new solution for the development of high-energy-density and long-life aqueous energy storage devices. Brief Description of the Drawings

[0034] Figure 1 It is a process flow chart of the two-dimensional vanadium-based nitride electrode material prepared by the present invention.

[0035] Figure 2 It is the SEM images of the precursor V 2 AlN at different magnifications; among them, (a) is the SEM at a scale of 3 μm, and (b) is the SEM image at a scale of 1 μm.

[0036] Figure 3 The SEM images of the two-dimensional vanadium-based nitride electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 2 of the present invention; among them, (a) is V 2 N-30, (b) is V 2 N-60, (c) is V 2 N-90, (d) is V 2 N-30-1, (e) is V 2 N-30-2.

[0037] Figure 4 It is the XRD pattern of V 2 N-30 prepared in Example 1 of the present invention.

[0038] Figure 5 It is the TEM image of V 2 N-30 prepared in Example 1 of the present invention.

[0039] Figure 6Photograph of the zinc-ion battery prepared in Application Example 1 of the present invention; among them, (a) is the positive electrode surface of the zinc-ion battery, and (b) is the negative electrode surface of the zinc-ion battery.

[0040] Figure 7 CV curves of the zinc-ion battery prepared in Application Example 1 of the present invention at different scanning rates.

[0041] Figure 8 Rate performance graph of the zinc-ion battery prepared in Application Example 1 of the present invention.

[0042] Figure 9 Charge-discharge curves of the zinc-ion battery prepared in Application Example 1 of the present invention.

[0043] Figure 10 Cyclic charge-discharge test of the zinc-ion battery prepared in Application Example 1 of the present invention at a current density of 5 A / g. Detailed implementation manners

[0044] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings.

[0045] In the description of the present invention, unless otherwise specified, the reagents used are commercially available, and the methods used are conventional techniques in the art.

[0046] Example 1

[0047] This example provides a preparation method for an aqueous electrode material of a two-dimensional vanadium-based nitride for an aqueous ion battery.

[0048] Step 1. Acid etching treatment:

[0049] (1.1) Place 30 ml of HCl solution with a concentration of 9 mol / L in a polytetrafluoroethylene container with holes, and add 1 g of LiF powder to the HCl solution to obtain an HF etching agent.

[0050] (1.2) Weigh 1 g of V 2 AlN powder, and under stirring at 30 °C, slowly add the V 2 AlN powder to the HF etching agent for an etching reaction for 24 h to obtain a reaction solution.

[0051] (1.3) Centrifuge the reaction solution at a rotation speed of 6000 rpm for 3 min to remove the upper-layer etching agent, and obtain a precipitate product.

[0052] (1.4) Centrifuge and wash the precipitate product with 2 mol / L hydrochloric acid and 1 mol / L lithium chloride solution twice each, and then wash it with deionized water twice to obtain V 2 N.

[0053] Step 2. Intercalation and exfoliation treatment:

[0054] (2.1) Add 10 ml of 40% tetrabutylammonium hydroxide solution to VN, shake it manually for 10 min, and then perform ultrasonic exfoliation in an ice bath for 1 h to obtain a VN mixture. 2 2

[0055] (2.2) Centrifuge and wash the VN mixture with deionized water three times, and then centrifuge it at a speed of 1500 - 2000 rpm for 30 min to obtain a VN product. 2 2

[0056] (2.3) Place the VN product in a refrigerator at -80 °C for 2 h, and then put it into a freeze dryer for cyclic freeze-drying treatment for 24 h to obtain VN nanosheets, that is, an aqueous electrode material, denoted as VN-30. 2 2 2

[0057] Example 2

[0058] This example provides a preparation method for an aqueous electrode material of two-dimensional vanadium-based nitride for aqueous ion batteries.

[0059] Step 1. Acid etching treatment:

[0060] (1.1) Place 30 ml of 9 mol / L HCl solution in a perforated polytetrafluoroethylene container, and add 1 g of LiF powder to the HCl solution to obtain an HF etching agent.

[0061] (1.2) Weigh 1 g of VAlN powder, and under stirring at 60 °C, slowly add the VAlN powder to the HF etching agent for an etching reaction for 24 h to obtain a reaction solution. 2 2

[0062] (1.3) Centrifuge the reaction solution at a speed of 6000 rpm for 3 min to remove the upper-layer etching agent, and obtain a precipitate product.

[0063] (1.4) Centrifuge and wash the precipitate product with 2 mol / L hydrochloric acid and 1 mol / L lithium chloride solution twice each, and then wash it with deionized water three times to obtain VN. 2

[0064] Step 2. Intercalation and exfoliation treatment:

[0065] (2.1) Add... to VN 2 ​​​​​​​​​​Add 10 ml of 40% tetrabutylammonium hydroxide solution to N, shake it manually for 10 min, and then ultrasonically exfoliate it in an ice bath for 1 h to obtain V 2 N mixture.

[0066] (2.2) After centrifugally washing the V 2 N mixture 3 times with deionized water, then centrifugally process it at a rotational speed of 1500 - 2000 rpm for 30 min to obtain V 2 N product.

[0067] (2.3) Place the V 2 N product in a refrigerator at -80 °C for 2 h of freezing treatment, and then put it into a freeze dryer for cyclic freeze-drying treatment for 24 h to obtain V 2 N nanosheets, that is, the aqueous electrode material, denoted as V 2 N-60.

[0068] The difference between this example and Example 1 is:

[0069] The temperature of the etching reaction in this example is 60 °C.

[0070] Example 3

[0071] This example provides a preparation method for a two-dimensional vanadium-based nitride electrode material for aqueous ion batteries.

[0072] Step 1, acid etching treatment:

[0073] (1.1) Place 30 ml of 9 mol / L HCl solution in a perforated polytetrafluoroethylene container, and add 1 g of LiF powder to the HCl solution to obtain an HF etchant.

[0074] (1.2) Weigh 1 g of V 2 AlN powder, and under stirring at 90 °C, slowly add the V 2 AlN powder to the HF etchant for an etching reaction for 24 h to obtain a reaction solution.

[0075] (1.3) Centrifuge the reaction solution at a rotational speed of 6000 rpm for 3 min to remove the upper-layer etchant, and obtain a precipitate product.

[0076] (1.4) Centrifugally wash the precipitate product 2 times each with 2 mol / L hydrochloric acid and 1 mol / L lithium chloride solution, and then wash it 2 times with deionized water to obtain V 2 N.

[0077] Step 2, intercalation and exfoliation treatment:

[0078] (2.1) Add to V 2Add 10 ml of 40% tetrabutylammonium hydroxide solution to N, shake it manually for 10 min, and then ultrasonically exfoliate it in an ice bath for 1 h to obtain the V 2 N mixture.

[0079] (2.2) After centrifugally washing the V 2 N mixture 3 times with deionized water, then centrifuge it at a speed of 1500 - 2000 rpm for 30 min to obtain the V 2 N product.

[0080] (2.3) Place the V 2 N product in a refrigerator at -80 °C for 2 h, and then put it into a freeze dryer for cyclic freeze-drying treatment for 24 h to obtain the V 2 N nanosheets, that is, the aqueous electrode material, denoted as V 2 N-90.

[0081] The difference between this example and Example 1 is:

[0082] The temperature of the etching reaction in this example is 90 °C.

[0083] Comparative Example 1

[0084] This comparative example provides a preparation method for a two-dimensional vanadium-based nitride electrode material for aqueous ion batteries.

[0085] Step 1, acid etching treatment:

[0086] (1.1) Place 30 ml of 9 mol / L HCl solution in a perforated polytetrafluoroethylene container, and add 1 g of LiF powder to the HCl solution to obtain an HF etchant.

[0087] (1.2) Weigh 1 g of V 2 AlN powder, and under stirring at 30 °C, slowly add the V 2 AlN powder to the HF etchant for an etching reaction for 24 h to obtain a reaction solution.

[0088] (1.3) Centrifuge the reaction solution at a speed of 6000 rpm for 3 min to remove the upper-layer etchant to obtain a precipitate product.

[0089] (1.4) Centrifugally wash the precipitate product 2 times each with 2 mol / L hydrochloric acid and 1 mol / L lithium chloride solution, and then wash it 3 times with deionized water to obtain V 2 N.

[0090] Step 2, exfoliation treatment:

[0091] (2.1) Place the V 2N was exfoliated in an ice bath under ultrasound for 1 h, then centrifugally washed 3 times with deionized water, and centrifuged at a speed of 1500 - 2000 rpm for 30 min to obtain V 2 N product.

[0092] (2.2) Place the V 2 N product in a refrigerator at -80 °C for 2 h of freezing treatment, and then put it into a freeze dryer for cyclic freeze-drying treatment for 24 h to obtain V 2 N nanosheets, that is, aqueous electrode materials, denoted as V 2 N-30-1.

[0093] The difference between this comparative example and Example 1 is:

[0094] In this comparative example, V 2 N was not dispersed in an intercalating agent for intercalation treatment.

[0095] Comparative Example 2

[0096] This comparative example provides a preparation method for a two-dimensional vanadium-based nitride electrode material for aqueous ion batteries.

[0097] Step 1. Acid etching treatment:

[0098] (1.1) Place 30 ml of HCl solution with a concentration of 9 mol / L in a polytetrafluoroethylene container with holes, and add 1 g of LiF powder to the HCl solution to obtain an HF etching agent.

[0099] (1.2) Weigh 1 g of V 2 AlN powder, and under stirring at 30 °C, slowly add the V 2 AlN powder to the HF etching agent for an etching reaction for 24 h to obtain a reaction solution.

[0100] (1.3) Centrifuge the reaction solution at a speed of 6000 rpm for 3 min to remove the upper-layer etching agent to obtain a precipitate product.

[0101] (1.4) Centrifugally wash the precipitate product with 2 mol / L hydrochloric acid and 1 mol / L lithium chloride solution 2 times each, and then wash it with deionized water 2 times to obtain V 2 N.

[0102] Step 2. Intercalation treatment:

[0103] (2.1) Add 10 ml of 40% tetrabutylammonium hydroxide solution to V 2 N, and shake it manually for 10 min to obtain a V 2 N mixture.

[0104] (2.2) Place the V 2After the N mixture was centrifugally washed three times with deionized water, it was then centrifugally treated at 1500 - 2000 rpm for 30 min to obtain V 2 N product.

[0105] (2.3) Place the V 2 N product in a refrigerator at -80 °C for 2 h of freezing treatment, and then put it into a freeze dryer for 24 h of cyclic freeze-drying treatment to obtain V 2 N nanosheets, that is, aqueous electrode materials, denoted as V 2 N-30-2.

[0106] The difference between this comparative example and Example 1 is that:

[0107] In this comparative example, V 2 N was not placed in an ice bath for ultrasonic peeling treatment.

[0108] Apply Example 1

[0109] This Application Example 1 provides a method for preparing a zinc-ion battery.

[0110] Step 1, prepare the positive electrode:

[0111] (1) Add the V 2 N-30, acetylene black, and PVDF prepared in Example 1 to a mortar in a mass ratio of 7:2:1, and then add 100 - 500 μL of NMP, and grind and mix until it becomes viscous to obtain a slurry.

[0112] (2) Uniformly coat the slurry on a carbon paper substrate, and after curing, punch it. Among them, a punching die with a diameter of 6 mm is used during the punching process, and the punching size is 1.13 cm 2 to obtain a positive electrode sheet.

[0113] Step 2, prepare the negative electrode:

[0114] Use sandpaper to polish a zinc foil sheet with a thickness of 0.1 - 0.2 mm to remove impurities and oxides on the surface of the zinc foil sheet, and then cut the polished zinc foil sheet into a size of 2 cm × 1 cm, that is, obtain a negative electrode sheet.

[0115] Step 3, assemble the zinc-ion battery:

[0116] Assemble the above-prepared positive electrode sheet, negative electrode sheet, 1 mol / L zinc trifluoromethanesulfonate electrolyte, and separator into a CR 2023 type button cell, that is, a zinc-ion battery.

[0117] Figure 1 is the process flow chart of the two-dimensional vanadium-based nitride electrode material prepared by the present invention. It can be seen from Figure 1 that the present invention uses V 2Using AlN as a precursor, V is etched through etching treatment 2 AlN is etched into multi-layered V 2 N; then, using ultrasonic-assisted intercalation and exfoliation treatment, the multi-layered V 2 N is exfoliated into single-layer or few-layer V 2 N nanosheets, and the obtained single-layer or few-layer V 2 N nanosheets are used as two-dimensional vanadium-based nitride electrode materials for aqueous ion batteries.

[0118] Experimental tests

[0119] 1. Surface morphology test

[0120] Figure 2 For V 2 SEM images of AlN materials at different magnification levels; among them, (a) is the SEM image at a scale of 3 μm, and (b) is the SEM image at a scale of 1 μm. It can be seen from Figure 2 that before etching, the V 2 AlN MAX phase presents a closely packed block structure.

[0121] Figure 3 SEM images of two-dimensional vanadium-based nitride electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 2; among them, (a) is V 2 N-30, (b) is V 2 N-60, (c) is V 2 N-90, (d) is V 2 N-30-1, (e) is V 2 N-30-2. It can be seen from Figure 3 in (a) to Figure 3 in (c) that the V 2 AlN materials are all successfully etched and exfoliated to obtain V 2 N nanolayer materials with a layered structure; and at an etching temperature of 30 °C, few-layer V 2 N nanomaterials with a relatively perfect lamellar structure can be obtained. It can be seen from Figure 3 in (d) that V 2 N-30-1, without the action of an intercalating agent and only under the action of single physical ultrasound, cannot obtain V 2 N with a layered structure; it can be seen from Figure 3 in (e) that V 2 N-30-2 can obtain multi-layered V 2 N under the action of a single intercalating agent, but it is difficult to exfoliate to obtain few-layer V 2 N nanosheet materials. The results show that it is difficult to obtain few-layer V 2V N nanosheets. Through the effective regulation of the intercalation treatment of the intercalant and ice-bath ultrasonic exfoliation, the present invention can achieve the preparation of V 2 N nanosheets.

[0122] 2. Structural characterization

[0123] Figure 4 XRD pattern of V 2 N-30 prepared in Example 1. As shown by Figure 4 the XRD patterns of V 2 AlN and V 2 N shown in Figure 4 , the diffraction peaks of V 2 AlN correspond to the standard card (JCPDS card no. 00-042-1213). A new characteristic peak appears at about 10.7° for V 2 N obtained after etching. According to (JCPDS card no. 00-033-1439), the diffraction peak can be attributed to the characteristic peak of V 2 N, indicating that V 2 N MXene has hexagonal crystal symmetry (P-31m). The appearance of the low-angle peak indicates that the Al atomic layer has been successfully removed from V 2 AlN MAX phase, and the interlayer spacing increases.

[0124] Figure 5 TEM image of V 2 N-30 prepared in Example 1. As can be seen from Figure 5 , the outline of the large lamellar structure is clear, which further indicates that the present invention has successfully obtained monolayer or few-layer V 2 N nanosheet material.

[0125] 3. Electrochemical tests

[0126] For the zinc-ion battery prepared in Application Example 1, a cyclic voltammetry test was carried out using an electrochemical workstation at a voltage of 0.01 V to 3 V and a scanning rate of 0.5 mV / s to 10 mV / s; when performing a constant-current charge-discharge test, the voltage range was set to 0.01 V to 3 V and the current intensity was 10 μA to 640 μA.

[0127] Figure 6 Photo of the zinc-ion battery prepared in Application Example 1; among them, (a) is the positive electrode surface of the zinc-ion battery, and (b) is the negative electrode surface of the zinc-ion battery.

[0128] Figure 7CV curves of the zinc-ion battery prepared in Application Example 1 at different scanning rates. It can be seen from the CV curve graph that the zinc-ion battery has a wide voltage window of up to 1.9 V, and there are two pairs of obvious redox peaks, which are typical battery-type electrode materials. Moreover, as the scanning rate increases, these redox peaks still exist well, accompanied by an increase in current density. This indicates that the zinc-ion battery has a good reversible Faraday reaction, further demonstrating its excellent rate performance.

[0129] 4. Charge and Discharge Tests of Zinc-Ion Battery

[0130] In this invention, a Shenzhen Neware CT-4008T charge and discharge tester was used to test the cycling stability of the zinc-ion battery prepared in Application Example 1 at room temperature.

[0131] Figure 8 Rate performance graph of the zinc-ion battery prepared in Application Example 1. As Figure 8 can be seen, at a scanning rate of 2 mV / s, the specific capacitance of the zinc-ion battery is as high as 579.6 F / g, indicating that the zinc-ion battery prepared in this invention has excellent rate performance.

[0132] Figure 9 Charge and discharge curve of the zinc-ion battery prepared in Application Example 1 of this invention. As Figure 7 can be seen, a high specific capacity of 542.5 mAh / g was achieved at a current density of 0.2 A / g.

[0133] Figure 10 Cyclic charge and discharge test of the zinc-ion battery prepared in Application Example 1 of this invention at a current density of 5 A / g. After 6000 cycles of charge and discharge, it still has a capacity retention rate of nearly 80%, and the Coulomb efficiency is as high as 100%, demonstrating excellent stability.

[0134] It should be noted that when this invention involves numerical ranges, it should be understood that any value between the two endpoints of each numerical range and the two endpoints themselves can be selected. Since the adopted step methods are the same as those in the embodiments, in order to avoid repetition, this invention describes the preferred embodiments. Although the preferred embodiments of this invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept, and these changes and modifications all fall within the scope of this invention.

[0135] Obviously, those skilled in the art can make various changes and modifications to this invention without departing from the spirit and scope of this invention. If these modifications and variations of this invention fall within the scope of the equivalent technology of this invention, this invention also intends to include these changes and deformations.

Claims

1. A method for preparing a two-dimensional vanadium-based nitride electrode material for an aqueous ion battery, characterized in that: The following steps are involved: Etching treatment: using V2AlN as a precursor, adding V2AlN into an etchant for etching reaction to remove the Al layer in V2AlN and obtain multi-layer V2N; Intercalation exfoliation treatment: multi-layer V2N is dispersed in an intercalation agent and subjected to ice bath ultrasonic treatment to allow the intercalation agent to enter the interlayer structure of V2N and expand the interlayer spacing of V2N to cause exfoliation, thereby obtaining single-layer or few-layer V2N nanosheets as two-dimensional vanadium-based nitride electrode materials for aqueous ion batteries.

2. The method for preparing a two-dimensional vanadium-based nitride electrode material for an aqueous ion battery according to claim 1, characterized in that: The intercalation agent is tetra-n-butylammonium hydroxide solution, and the mass concentration of the tetra-n-butylammonium hydroxide solution is 40% to 50%.

3. The method for preparing a two-dimensional vanadium-based nitride electrode material for an aqueous ion battery according to claim 1, characterized in that: The ice bath ultrasonic treatment lasts for 1 h to 2 h.

4. The method for preparing a two-dimensional vanadium-based nitride electrode material for an aqueous ion battery according to claim 1, characterized in that: The etching treatment time is 24h to 48h, and the temperature is 30°C to 90°C.

5. The method for preparing a two-dimensional vanadium-based nitride electrode material for an aqueous ion battery according to claim 1, characterized in that: The etching agent is prepared by the following steps: adding fluoride salt to hydrochloric acid under stirring to obtain the etching agent.

6. The method for preparing a two-dimensional vanadium-based nitride electrode material for an aqueous ion battery according to claim 5, characterized in that: The usage ratio of hydrochloric acid to lithium fluoride is 0.135 mol to 0.27 mol: 1 g to 2 g; The concentration of the hydrochloric acid is 8 mol / L to 10 mol / L; The concentration of the fluoride salt is 33 g / L to 66 g / L.

7. The method for preparing a two-dimensional vanadium-based nitride electrode material for an aqueous ion battery according to claim 1, characterized in that: The intercalation stripping treatment is followed by freeze drying, and the freeze drying conditions are: after freezing treatment at -80°C, cyclic drying in a freeze dryer for 24h to 48h.

8. A two-dimensional vanadium-based nitride electrode material prepared by the method for preparing a two-dimensional vanadium-based nitride electrode material for an aqueous ion battery according to any one of claims 1 to 7.

9. Use of the two-dimensional vanadium-based nitride electrode material according to claim 8 in the preparation of an aqueous ion battery.

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