In-situ derived heterostructured vanadium oxide and preparation method and application thereof

Abstract

The present invention relates to an in-situ derived heterogeneous structure vanadium oxide, its preparation method and application. The preparation method uses vanadium pentoxide, oxalic acid and sulfur powder as raw materials. A certain mass ratio of sulfur powder and vanadium pentoxide with modified morphology is calcined in an inert atmosphere. Due to the reduction of sulfur, a trace amount of sulfur atom-doped VO2 / V6O with a heterogeneous structure is in-situ generated. 13 , and this heterogeneous structure vanadium oxide is used as an electrode material. Due to the synergistic effect between different substances and the doping of trace sulfur atoms, it alleviates the volume change generated during charge and discharge of the electrode material, and also accelerates ion migration and charge transfer, showing a higher specific capacity and excellent cycle stability.

Description

Technical Field

[0001] The invention relates to the field of zinc ion batteries, and in particular to an in-situ derived heterostructured vanadium oxide and a preparation method and application thereof. Background Art

[0002] With the replacement of various electronic products, people have higher expectations for the power density, energy density and rate performance of batteries. Due to the advantages of high energy density, safety and environmental protection, simple assembly and low cost, aqueous zinc-ion batteries have become energy storage devices with great application prospects. The positive electrode material is one of the key factors that determine the performance of the battery. At present, the positive electrode materials of zinc-ion batteries that have been studied include vanadium-based oxides, manganese-based oxides, Prussian blue analogs, polyanionic compounds, etc.

[0003] The valence state of vanadium is rich, and multi-electron reactions can be carried out during the charge and discharge process to achieve the transformation between different vanadium oxides, so a higher specific capacity can be obtained. The diversity of valence states and crystal structures of vanadium oxides provides researchers with a larger design space for research in this field. However, the defect of vanadium oxides is that serious volume changes will occur during the zinc ion deintercalation process, resulting in structural collapse and shortening the cycle life of the material. Therefore, for vanadium oxide positive electrode materials, improving their cycle stability is a key issue that needs to be solved urgently. Summary of the invention

[0004] In view of the problems existing in the prior art, the primary purpose of the present invention is to provide an in-situ derived heterostructured vanadium oxide and a preparation method and application thereof, wherein the heterostructured vanadium oxide converts VO 2 and V 6 O 13 Combined together, it has high crystallinity, abundant grain boundaries, appropriate oxygen vacancies, and is doped with trace amounts of sulfur. The synergistic effect enables the vanadium oxide to exhibit higher specific capacity and excellent cycle stability when used as a positive electrode material for batteries.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing an in-situ derived heterostructured vanadium oxide comprises the following steps:

[0007] A certain amount of vanadium pentoxide having a first morphological characteristic is added into water at a certain temperature, and a reducing agent is added under stirring to obtain a mixed solution;

[0008] The mixed solution is dried, then ground, and then calcined in an air atmosphere to obtain powdery vanadium pentoxide having a second morphological characteristic;

[0009] Subsequently, vanadium pentoxide with the second morphological feature is calcined with sulfur powder in an inert atmosphere, and the sulfur powder is located upstream of the gas flow to in-situ generate sulfur-doped VO with a heterogeneous structure. 2 / V 6 O 13 .

[0010] Furthermore, the reducing agent is oxalic acid.

[0011] Furthermore, the temperature of the water is 75° C., the amount of vanadium pentoxide having the first morphological characteristic added is 0.167 mol / L, the concentration of oxalic acid is 0.5 mol / L, the stirring speed is 400-500 r / min, and the stirring time is 2-4 h.

[0012] Furthermore, the drying temperature is 70° C. and the drying time is about 70 hours.

[0013] Furthermore, the calcination conditions under air conditions are: a tubular furnace or a muffle furnace is selected, the calcination temperature is 260° C., the holding time is 3 hours, and the heating rate is 2-5° C. / min.

[0014] Furthermore, the calcination conditions under the inert atmosphere are: in a nitrogen or argon atmosphere, vanadium pentoxide and sulfur powder are placed in a covered porcelain boat in a mass ratio of 0.5:1 to 8:1, with the sulfur powder located upstream of the air flow. The calcination temperature conditions are heating at 2 to 10°C / min, keeping at 400 to 500°C for 1 to 3 hours, and then cooling naturally with the furnace.

[0015] Furthermore, the first morphological feature is different from the second morphological feature.

[0016] Furthermore, compared with the vanadium pentoxide with the first morphological characteristics, the vanadium pentoxide with the second morphological characteristics has smaller particles and more voids.

[0017] An in-situ derived heterostructured vanadium oxide is obtained by using the above preparation method.

[0018] Application of the above vanadium oxide in positive electrode materials of aqueous zinc ion batteries.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The in-situ derived heterostructure vanadium oxide of the present invention has abundant heterojunction interfaces, and has large lattice distortion at these interfaces. The heterostructure vanadium oxide is used as a positive electrode material. Due to the presence of its crystal defects, the mechanical stress generated by the electrode material during the charge and discharge process can be relieved, thereby improving the cycle stability of the electrode material. The vanadium atoms of different valence states coexisting in the heterojunction improve the reaction kinetics of the battery by adjusting the intrinsic electronic structure. The disordered atomic arrangement at the interface also provides more active sites for the storage and reaction of zinc ions. The abundant heterojunction interfaces improve the cycle stability and specific capacity of the battery.

[0021] On the other hand, the in-situ derived heterostructured vanadium oxide of the present invention contains VO 2 and V 6 O 13 The two have different redox potentials. During the electrochemical reaction, they react at different potentials, which promotes the reaction and storage of more zinc ions, which is beneficial to improving the specific capacity.

[0022] The in-situ derived heterostructured vanadium oxide of the present invention introduces defects and oxygen vacancies into the material due to the doping of trace amounts of sulfur atoms, which changes the surface chemical state and electronic structure, improves the intrinsic electronic conductivity, and promotes the improvement of rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The in-situ derived heterostructure VO prepared in the embodiment of the present invention 2 / V 6 O 13 XRD pattern of .

[0024] Figure 2 These are SEM images of vanadium pentoxide before and after the reaction.

[0025] Figure 3 It is the XPS chart of the vanadium oxide prepared in the embodiment of the present invention.

[0026] Figure 4 3 is an EDS diagram of the vanadium oxide prepared in the embodiment of the present invention.

[0027] Figure 5 It is a constant current charge and discharge performance diagram of aqueous zinc ion batteries used with vanadium oxides prepared in the examples and comparative examples of the present invention. DETAILED DESCRIPTION

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention. The experimental methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, can be obtained from public commercial channels.

[0029] In addition, the use of terms such as "first", "second", etc. to describe various layers, regions, sections, etc. is not intended to be limiting. The use of "having", "containing", "including", "comprising", etc. is open-ended, indicating the presence of stated elements or features, but not excluding additional elements or features. Unless the context clearly indicates otherwise.

[0030] Example 1

[0031] Take 6mmol of vanadium pentoxide with the first morphological feature and 18mmol of oxalic acid, add the vanadium pentoxide and oxalic acid to 36mL of deionized water at 75°C under magnetic stirring at a speed of 420r / min, and stir in a constant temperature water bath for 2h. Then dry at 70°C for about 70h to obtain a dark blue solid. After grinding, calcine at 260°C in an air atmosphere for 3h to obtain vanadium pentoxide with the second morphological feature, which is different from the first morphological feature.

[0032] Weigh 0.0167 g of sulfur powder and 0.1 g of vanadium pentoxide with the second morphological feature (mass ratio is 1:6), and place them separately in a covered porcelain boat, with the sulfur powder located upstream of the airflow. 2 In the atmosphere, the temperature was raised at a rate of 2°C / min to 450°C, calcined for 1 hour, and then cooled naturally in the furnace. Finally, the in-situ derived heterostructured VO 2 / V 6 O 13 .

[0033] Example 2

[0034] Under magnetic stirring at a speed of 420r / min, 6mmol of vanadium pentoxide with the first morphological characteristics and 18mmol of oxalic acid were added to deionized water with a temperature of 75°C and a volume of 36mL, and stirred in a constant temperature water bath for 2h. Then dried at 70°C for about 70h to obtain a dark blue solid. After grinding, it was calcined at 260°C in an air atmosphere for 3h to obtain vanadium pentoxide with the second morphological characteristics, which is different from the first morphological characteristics.

[0035] Weigh 0.0125 g of sulfur powder and 0.1 g of vanadium pentoxide with the second morphological feature (mass ratio is 1:8), and place them separately in a covered porcelain boat, with the sulfur powder located upstream of the airflow. 2 In the atmosphere, the temperature was raised at a rate of 2°C / min to 450°C, calcined for 1 hour, and then cooled naturally in the furnace. Finally, the in-situ derived heterostructured VO 2 / V 6 O 13 .

[0036] Example 3

[0037] Under magnetic stirring at a speed of 420r / min, 6mmol of vanadium pentoxide with the first morphological characteristics and 18mmol of oxalic acid were added to deionized water with a temperature of 75°C and a volume of 36mL, and stirred in a constant temperature water bath for 2h. Then dried at 70°C for about 70h to obtain a dark blue solid. After grinding, it was calcined at 260°C in an air atmosphere for 3h to obtain vanadium pentoxide with the second morphological characteristics, which is different from the first morphological characteristics.

[0038] Weigh 0.025g of sulfur powder and 0.1g of vanadium pentoxide with the second morphological feature (mass ratio is 1:4), and place them separately in a covered porcelain boat, with the sulfur powder located upstream of the airflow. 2 In the atmosphere, the temperature was raised at a rate of 2°C / min to 450°C, calcined for 1 hour, and then cooled naturally in the furnace. Finally, the in-situ derived heterostructured VO 2 / V 6 O 13 .

[0039] Example 4

[0040] Under magnetic stirring at a speed of 420r / min, 6mmol of vanadium pentoxide with the first morphological characteristics and 18mmol of oxalic acid were added to 36mL of deionized water at a temperature of 75°C, and stirred in a constant temperature water bath for 2h. Then dried at 70°C for about 70h to obtain a dark blue solid. After grinding, it was calcined at 260°C in an air atmosphere for 3h to obtain vanadium pentoxide with the second morphological characteristics, which is different from the first morphological characteristics.

[0041] Weigh 0.0167 g of sulfur powder and 0.1 g of vanadium pentoxide with the second morphological feature (mass ratio is 1:6), and place them separately in a covered porcelain boat, with the sulfur powder located upstream of the airflow. 2 In the atmosphere, the temperature was raised at a rate of 2°C / min to 500°C, calcined for 3 hours, and then cooled naturally in the furnace. Finally, the in-situ derived heterostructured VO 2 / V 6 O13 .

[0042] Comparative Example 1

[0043] Weigh 0.0167 g of sulfur powder and 0.1 g of vanadium pentoxide with the first morphological feature (mass ratio is 1:6), and place them separately in a covered porcelain boat, with the sulfur powder located upstream of the airflow. 2 In the atmosphere, the temperature was raised at a rate of 2°C / min to 450°C, calcined for 1 hour, and then cooled naturally in the furnace. Finally, the in-situ derived heterostructured VO 2 / V 6 O 13 .

[0044] Figure 1 The X-ray diffraction patterns (XRD) of the in-situ derived heterostructured vanadium oxides obtained in Examples 1 to 3 show that under the sulfidation conditions, vanadium pentoxide is reduced and VO is generated in situ. 2 / V 6 O 13 In the heterogeneous structured composites, the peaks of different materials are relatively obvious, indicating that their crystallinity is relatively high.

[0045] Figure 2 Figure 1 is a SEM image of vanadium pentoxide, where (a) is a SEM image of commercial vanadium pentoxide before the reaction, and (b) is a SEM image of vanadium pentoxide with the second morphological characteristics after the reaction. Comparing the vanadium pentoxide before and after the reaction, it can be seen that the vanadium pentoxide after the reaction is composed of stacked small particles of about 50nm, with more voids and a larger specific surface area, which will promote the full sulfidation process.

[0046] Figure 3 2 is the XPS spectrum of the vanadium oxides prepared in Examples 1 to 3. The figure shows the narrow spectrum scan of S 2p. Although the signal is weak, it can still be observed at 168.6 (S 4+ ) and 163.3eV(S 2- ), indicating that sulfur atoms are successfully doped on the surface without affecting the crystal structure of the sample.

[0047] Figure 4 This is the EDS image of the in-situ derived heterostructured vanadium oxide obtained in Example 1. It can be seen from the figure that vanadium, oxygen and sulfur elements are evenly distributed in the sample, and the atomic proportion of sulfur element is 0.46%, indicating the successful doping of sulfur element on the surface.

[0048] Figure 5The electrochemical performance of the in-situ derived heterostructured vanadium oxide prepared in Examples 1 to 3 of the present invention and Comparative Example 1 when used as a positive electrode material for a zinc ion battery is shown. The vanadium oxide obtained in Examples 1 to 3 and Comparative Example 1 is used as a positive electrode material, respectively. The vanadium oxide, conductive carbon black super P, and adhesive in a mass ratio of 7:2:1 are ground evenly, and then NMP is added to continue grinding until it is in a paste state, and evenly coated on a stainless steel mesh, and dried at a temperature of 60°C in a vacuum environment for 12 hours to obtain a positive electrode for a zinc ion battery; a metal zinc foil is used as a negative electrode, an aqueous solution containing 0.07M sodium dodecyl sulfate and 2M zinc trifluoromethanesulfonate is used as an electrolyte, and glass fiber is used as a separator to assemble a battery. Figure 5 Figure (a) shows the performance of batteries assembled with these four different cathode materials at 0.5A g -1 The cycle performance of S-VO obtained in Example 1 2 / V 6 O 13 (1:6) After 500 cycles, it still shows ~400 mAh g -1 The specific capacity of the positive electrode materials obtained in Examples 1, 2, and 3 was still as high as 91.94%, 91.18%, and 81.52% after 300 cycles. Figure 5 Figure (b) shows the performance of these materials at 10A g -1 The cycle performance under the condition of 1000 cycles shows that after 3000 cycles, the specific capacities of the positive electrode materials of Examples 1 to 3 can still be maintained at 250, 180, and 180 mAh g -1 The capacity retention rates are 83.9%, 86.6% and 65.2% respectively. However, the positive electrode material obtained in Comparative Example 1 decays sharply in the charge and discharge cycles of large and small currents, indicating that the V with the second morphological characteristics after the experimental treatment 2 O 5 The in-situ derived heterostructured vanadium oxides obtained after sulfidation have better cycling stability.

[0049] The implementation methods of the present invention are not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A method for preparing in-situ derived heterostructured vanadium oxides, It is characterized in that The following steps are involved: 0.167 mol / L of vanadium pentoxide having the first morphological feature is added to water at 75°C, and 0.5 mol / L of reducing agent oxalic acid is added under stirring conditions of a stirring speed of 400-500 r / min for a stirring time of 2-4 h to obtain a mixed solution; The mixed solution is dried at 70° C. for 70 hours, then ground, and then calcined in a tube furnace or a muffle furnace in an air atmosphere at a calcination temperature of 260° C. for 3 hours at a heating rate of 2-5° C. / min to obtain powdered vanadium pentoxide having the second morphological feature; Subsequently, vanadium pentoxide with the second morphological feature is calcined with sulfur powder in an inert atmosphere, and the sulfur powder is located upstream of the gas flow to in-situ generate sulfur-doped VO with a heterogeneous structure. 2 / V 6 O 13 .

2. According to the preparation method of claim 1, It is characterized in that The conditions for calcination under the inert atmosphere are: in a nitrogen or argon atmosphere, vanadium pentoxide and sulfur powder are placed in a covered porcelain boat in a mass ratio of 0.5:1-8:1, with the sulfur powder located upstream of the air flow. The calcination temperature conditions are heating at 2-10 °C / min, keeping at 400-500 °C for 1-3 h, and naturally cooling with the furnace.

3. According to the preparation method of claim 1 or 2, It is characterized in that The first topographical feature is different from the second topographical feature.

4. According to the preparation method of claim 3, It is characterized in that Compared with the vanadium pentoxide with the first morphological characteristics, the vanadium pentoxide with the second morphological characteristics has smaller particles and more voids.

5. An in-situ derived heterostructured vanadium oxide, It is characterized in that The in-situ derived heterostructured vanadium oxide is obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the vanadium oxide according to claim 5 in positive electrode materials for aqueous zinc ion batteries.

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