CN111834627A

CN111834627A - VO (volatile organic compound)2Nano flower material and preparation method and application thereof

Info

Publication number: CN111834627A
Application number: CN202010736938.5A
Authority: CN
Inventors: 张睿智; 黄靖栋; 尹岚; 侯蕊
Original assignee: Hunan Institute of Technology
Current assignee: Hunan Institute of Technology
Priority date: 2020-07-28
Filing date: 2020-07-28
Publication date: 2020-10-27
Anticipated expiration: 2040-07-28
Also published as: CN111834627B

Abstract

VO (volatile organic compound)₂The invention discloses a nano flower material and a preparation method and application thereof, relates to the technical field of zinc ion battery electrode materials, and discloses V prepared by utilizing an electrostatic spinning means₂O₅The nano-fiber is used as a substrate, and then VO grows on the substrate in a hydrothermal mode₂And (4) nano flowers. Compared with the V-O compound used for the zinc ion battery in the prior art, the VO prepared by the invention is uniform and has extremely large specific surface area₂Nanoflower material, the VO₂Gaps are filled among petal-shaped structures of the nano flower material, so that the electrolyte can easily penetrate into the deep layer of the material, the contact with active substances is increased, and the electrochemical performance is favorably improved. Since the material has a poleLarge specific surface area, can store Zn during charging and discharging²⁺Ion, and may be Zn²⁺The ion and electron access provides a fast channel, and the good cycle and rate performance is shown in an electrochemical test. VO described above₂The preparation method of the nanoflower does not cause pollution to the environment, the process is easy to control, and the preparation method is suitable for large-scale industrial production.

Description

VO (volatile organic compound)2Nano flower material and preparation method thereofAnd applications

Technical Field

The invention relates to the technical field of zinc ion battery electrode materials, in particular to VO₂A nano flower material and a preparation method and application thereof.

Background

The rechargeable batteries currently on the market mainly include lead-acid batteries, nickel-metal hydride batteries, lithium ion batteries (including lithium batteries and polymer lithium batteries), and the like, and the batteries of the above types have respective disadvantages in terms of safety, price, environmental protection, and energy density. The secondary water system zinc ion battery has the advantages of safety, low price, environmental protection, high energy density and the like. Secondary aqueous Zinc Ion Batteries (ZIBs) with high energy density are expected to meet the growing demand for safe, sustainable energy storage devices.

VO₂There are five morphologies in nature, two stable structures and three metastable structures. Two stable structures are respectively metallic phase VO in high temperature state₂(R) and low-temperature non-metallic phase VO₂(M), the metallic phase in the high temperature state is a tetragonal rutile structure, and the non-metallic phase in the low temperature state has a monoclinic phase structure distorted in the rutile structure. The other three metastable structures are VO₂（A）、VO₂(B) And VO₂(C) In which the first two phases are monoclinic crystal structures, VO₂(A) The octahedron in the crystal structure is a three-dimensional stereo structure and cannot be a layered structure capable of being embedded with ions. VO B type₂Double layer V with intact bc axis for crystals₄O₁₀The strip-shaped tunnel is also connected by VO₂An octahedral basic unit resulting in the presence of a crystal plane tunnel of size 8.2 A.times.5.2A along the c and b axis, which may be effective as Zn²⁺Intercalation and deintercalation during charging and discharging provide access paths for rapid zinc ion battery non-organic and aqueous reversal/deintercalation zinc ion batteries.

Theoretically, VO₂(B) One-dimensional (1D) nanostructures of nanorods, nanowires, and nanoribbons can provide large surface areas and efficient electronsThe transmission path is easy to realize high capacity, but the materials still have the problems of high capacity fading speed and poor cycle stability and reversibility under the condition of large current.

Disclosure of Invention

One of the purposes of the invention is to synthesize VO by spinning and hydrothermal compounding in order to overcome the defect that the crystal structure of vanadium material is easy to be damaged during zinc extraction₂The nanometer flower material is used to improve the zinc-removing and embedding circulation stability of vanadium material and raise the electrochemical performance of the material.

In order to achieve the above object, the present invention provides a VO₂The preparation method of the nano flower material comprises the following steps:

step one, preparing a hydrothermal reaction solution:

1.1. adding a proper amount of V₂O₅Powder and H₂C₂O₄·2H₂Dissolving O in mixed solvent of distilled water and ethanol, and dropwise adding appropriate amount of H under magnetic stirring₂O₂Clarifying the solution;

step two, preparing VO by hydrothermal method₂The nano flower material:

2.1. with calcined V₂O₅Taking the electrostatic spinning fiber as a substrate of the hydrothermal reaction, putting the electrostatic spinning fiber into the hydrothermal reaction liquid prepared in the step one, putting the hydrothermal reaction liquid in a reaction kettle for hydrothermal reaction at the temperature of 120-280 ℃, and naturally cooling the reaction liquid to room temperature after the reaction is carried out for 0.5-13h to obtain a solid product;

2.2. separating solid products by a centrifugal machine, washing and drying to obtain the VO₂A nanoflower material.

Wherein V as a substrate for the hydrothermal reaction in step 2.1₂O₅The preparation method of the electrostatic spinning fiber comprises the following steps:

a. adding a proper amount of NH₄VO₃And H₂C₂O₄·2H₂Placing O in N, N-dimethylformamide, and magnetically stirring to form a clear blue solution;

b. adding a proper amount of polyvinylpyrrolidone into the blue solution, and fully and uniformly mixing the polyvinylpyrrolidone with the blue solution through magnetic stirring to obtain a spinning precursor solution;

c. c, carrying out continuous electrostatic spinning by using the spinning precursor solution obtained in the step b to form a fiber film;

d. drying the collected fiber film, placing in a heating furnace, and heating at 0.5-5 deg.C for min^-1The temperature rise speed is heated to 450-700 ℃ for calcination for 0.5 to 7 hours, and after the calcination is finished, V which can be used as a hydrothermal reaction substrate is obtained₂O₅Electrospinning the fibers.

Preferably, in step 1.1, said V₂O₅Powder and H₂C₂O₄·2H₂The mass ratio of O is 2: 3.

further, in the mixed solvent of step 1.1, the volume ratio of distilled water to ethanol is 3: 14.

Further, in step 1.1, H₂O₂The concentration of the solution is 10-50%.

Preferably, in step 2.1, the temperature of the hydrothermal reaction is 180 ℃ and the reaction time is 3 h.

Preferably, the polyvinylpyrrolidone added in step b has an average molecular weight of 1300000.

Wherein, in the step c, the spinning precursor solution is added into an injector during electrostatic spinning, the injector is arranged on an injection pump, and the feeding speed is set to be 0.1-6.6ml h^-1A voltage of 5-32kV was applied between the needle and the collection roller, and the receiving distance was 5-30 cm.

On the other hand, the invention also provides a VO₂Nanoflower material, the VO₂The nano flower material is prepared by the method.

Finally, the invention also relates to application of the VO2 nanoflower material as a positive electrode material of a zinc ion battery.

The invention creatively utilizes V prepared by electrostatic spinning means₂O₅The nano-fiber is used as a substrate, and then VO grows on the substrate in a hydrothermal mode₂And (4) nano flowers. Compared with the V-O compound used for the zinc ion battery in the prior art, the VO with uniformity and extremely large specific surface area is prepared by the method₂Nanoflower, the VO₂Gaps are filled among petal-shaped structures of the nano flower material, so that the electrolyte can easily penetrate into the deep layer of the material, the contact with active substances is increased, the specific surface area is further increased, and the electrochemical performance is favorably improved. Because the material has extremely large specific surface, Zn can be stored in the charging and discharging process²⁺Ionic, and which has excellent electrical conductivity, may be Zn²⁺The entrance and exit of ions and electrons provide fast channels, thereby being capable of showing good cycling and rate performance in electrochemical tests.

Description of the drawings:

FIG. 1 is V₂O₅XRD data pattern of nanofibers;

FIG. 2 is VO₂XRD data pattern of nanoflower;

FIG. 3 is VO₂A raman data map of the nanoflower;

FIG. 4 is V₂O₅Nanofibers and VO₂SEM image of the nanoflower material, in which (a) is V₂O₅The low-magnification SEM topography of the nano-fiber, and (b) is V₂O₅A high magnification SEM topography of the nanofibers; (c) is VO₂The low-magnification SEM topography of the nano flower material, and (d) is VO₂A high-magnification SEM topography of the nanoflower material;

FIG. 5 is VO₂The nano flower material has a current density of 500mA g^-1And 5A g^-1The results of the cycle performance test of (a) are shown in the figure, in which (a) is a current density of 500mA g^-1The results of the cycle performance test were shown in (b) which is a current density of 5A g^-1A time cycle performance test result chart;

FIG. 6 is VO₂A cycle rate performance test result chart of the nano flower material;

FIG. 7 is VO₂The CV curve and the charge-discharge curve chart of the nanoflower material are shown in the figure, wherein (a) is the CV curve chart, and (b) is the charge-discharge curve chart;

FIG. 8 is VO₂Living nanoflower material and V₂O₅Impedance profile of nanofibers.

Detailed Description

In order to facilitate the understanding of those skilled in the art, the present invention will be further described with reference to the following examples, which are not intended to limit the present invention. It should be noted that the following examples are carried out in the laboratory, and it should be understood by those skilled in the art that the amounts of the components given in the examples are merely representative of the proportioning relationship between the components, and are not specifically limited.

Firstly, preparing a spinning substrate.

a. Adding a proper amount of NH₄VO₃And H₂C₂O₄·2H₂O was placed in N, N-dimethylformamide and magnetically stirred to form a clear blue solution. Specifically, in this example, 0.48 g of ammonium metavanadate (NH)₄VO₃) And 1.3g oxalic acid (H) dihydrate₂C₂O₄·2H₂O) in 10mL of N, N-Dimethylformamide (DMF) and magnetic stirring at 55 ℃ for 2 hours resulted in a clear blue solution.

b. And adding a proper amount of polyvinylpyrrolidone into the blue solution, and fully and uniformly mixing the polyvinylpyrrolidone with the blue solution through magnetic stirring to obtain a spinning precursor solution. Specifically, in this example, 0.8g of PVP (polyvinylpyrrolidone, average molecular weight of 1300000) was added to the blue solution, and the mixture was magnetically stirred at 55 ℃ for 8 hours to obtain a spinning precursor solution.

c. And c, carrying out continuous electrostatic spinning by using the spinning precursor solution obtained in the step b to form a fiber film. The specific operation mode of electrostatic spinning is as follows: the spinning precursor solution was transferred to a 10ml syringe mounted on a syringe pump with the feed rate set at 0.6ml h^-1A voltage of 20kV was applied between the needle and the collection roller, and the take-up distance was 15 cm.

d. Drying the collected fiber film, placing in a heating furnace, and heating at 0.5-5 deg.C for min^-1The temperature rising rate (0.5 ℃ C. min was selected in this example)^-1Heating rate of (1) to 450-Obtaining V which can be used as a substrate of hydrothermal reaction₂O₅Electrospinning the fibers. It should be noted that the rate of temperature rise, the calcination temperature and the time may be adjusted within the ranges given above according to the actual circumstances.

Secondly, preparing a hydrothermal reaction solution.

2.1. Adding a proper amount of V₂O₅Powder and H₂C₂O₄·2H₂Dissolving O in mixed solvent of distilled water and ethanol, and dropwise adding appropriate amount of H under magnetic stirring₂O₂The solution clarified the solution. Specifically, in the present embodiment, V₂O₅Powder and H₂C₂O₄·2H₂O adopts 2: 3 by mass, e.g. V₂O₅The powder may be 0.2g, correspondingly, H₂C₂O₄·2H₂O is 0.3g, and the volume ratio of distilled water to ethanol in the mixed solvent is 3:14, for example, 7.5ml of distilled water and 35ml of ethanol smell. H₂O₂H in solution₂O₂Concentration of (3%) H₂O₂The dosage of the solution is 2 ml.

Third, preparation of VO by hydrothermal method₂A nanoflower material.

3.1. Calcined V prepared in one step₂O₅Taking the electrostatic spinning fiber as a substrate of the hydrothermal reaction, putting the electrostatic spinning fiber into the hydrothermal reaction liquid prepared in the step two, putting the electrostatic spinning fiber into a reaction kettle for hydrothermal reaction under the condition that the temperature is 120-280 ℃ (the hydrothermal reaction temperature selected in the embodiment is 180 ℃), and naturally cooling the electrostatic spinning fiber to the room temperature after the reaction is carried out for 0.5-13h (the reaction time set in the embodiment is 3 h) to obtain a solid product;

3.2. separating solid product with centrifuge, repeatedly washing with water and alcohol alternately, and drying to obtain final product.

Fourthly, measuring the phase, the morphology and the performance of the product.

1. Firstly, XRD analysis is carried out on the electrostatic spinning product, the X-ray diffraction pattern of the calcined electrostatic spinning nano-fiber powder is shown in figure 1, all diffraction peaks well correspond to PDF cards (JCPDS-77-2418),proves that the product after spinning annealing is V with high purity₂O₅. From the X-ray diffraction line and the corresponding PDF card, it can be found that the highest intensity at 20.314 ° among the diffraction peaks is the {001} orthogonal V2O5 family of crystal planes, and the other second-order intensity peaks occur at 26.135 ° and 31.048 °, corresponding to the crystal planes (110) and (400), respectively. By comparing other vanadium-based materials, no impurity peak can be found, which indicates that the V2O5 nano-fiber synthesized by the step is pure phase. In addition, the diffraction peak has a relatively sharp peak shape and relatively high intensity, which shows that the V2O5 crystal has good growth condition and relatively high crystallinity in the calcination process of the electrostatic spinning precursor.

2. The XRD results of the product synthesized by further hydrothermal method on the basis of the spinning product are shown in fig. 2. The XRD diffraction peak and B-type VO are combined₂Comparison of standard card JCPDS NO.31-1438 shows that the obtained product only contains one phase and is B type VO with high purity₂. The VO₂(B) Belongs to monoclinic system, and has space group of C2/m (12), a =12.03nm, b =3.693nm, C =6 and 42 nm. At VO₂Of the plurality of crystal forms of (A), VO₂(B) Because octahedrons in the crystal form a two-dimensional layered structure in space and form a bc axial tunnel, the zinc ion battery is more suitable for Zn in the charge and discharge process of the zinc ion battery²⁺Ions are inserted and extracted in the active material, and thus VO is very suitable for energy storage₂A crystalline form. As can be seen from the diffraction image shown in FIG. 2, the diffraction peak on the {110} crystal plane at 25.281 ℃ has a much larger intensity than other peaks, so that it can be judged that the crystal grows on the substrate with the best growth orientation along the {110} crystal plane, and the crystal can form a more regular crystal morphology on the substrate surface. In addition, each diffraction peak on the diffraction map can better correspond to the position of the standard peak provided by the PDF card, and no peak is lost or shifted, and no V exists₂O₅The existence of characteristic peaks of the matrix due to the excess reducing agent H during the hydrothermal reaction₂C₂O₄·2H₂Presence of O, V of the surface₂O₅VO reduced to V four valence₂And (4) crystals. In addition, VO is due to the surface₂Production of nano-productsThe surface of the body has a covering effect, so that the original diffraction peak in the matrix cannot be identified.

3. Because the organic high molecular polymer PVP is used in the electrostatic spinning link for preparing the substrate, the annealing temperature in the air in the calcining link is 500 ℃, the PVP pyrolysis temperature is 400-450 ℃, the PVP pyrolysis temperature can be theoretically completely decomposed at more than 450 ℃, but the possibility of PVP and small molecular product residue after the PVP decomposition can not be eliminated. To determine hydrothermal process vs. V₂O₅The influence of the residue of organic matters and carbon simple substances in electrostatic spinning is characterized by raman spectra of the raman peaks of carbon and organic matters, as shown in fig. 3. In the figure, it is difficult to find the existence of a relatively strong raman peak, and it is impossible to find the existence of a peak indicating a carbon simple substance and a peak indicating a carbon skeleton structure of an organic substance, and only a weak peak indicating a V — O compound is found. Therefore, the raman spectrum shows that the final cathode material no longer contains carbon and organic matters, which is consistent with the result of XRD detection.

4. In order to determine the morphology of the base material, SEM examination was performed thereon, and V after the electrospinning annealing is shown in FIGS. 4 (a), (b)₂O₅And (3) nano fibers. From the overall appearance, V₂O₅The electrostatic spinning product has uniform fiber and no accumulation and melting phenomena, which indicates that V is successfully prepared₂O₅The nanofiber of (4). The thickness of each fiber can be measured by further amplifying the high-resolution lens, three fibers are selected for diameter measurement, and the diameters are all around 280nm, so that the thickness is uniform, the independence is good, and the fibers are almost free of adhesion. The SEM result shows that the spinning product with uniform nanometer structure is used as the substrate for growth, so that the final product has larger specific surface area and better nanometer structure. In addition, the phenomena of surface porosity, hollowness and the like formed by annealing after spinning are beneficial to the full infiltration of electrolyte and the reduction of energy barrier in ion transmission, thereby increasing the electrode activity.

Based on V₂O₅SEM images of active material of hydrothermal reaction product with nanofiber as substrate are shown in (c) and (d) of FIG. 4Shown in the figure. From the figure, it can be seen that the shape of the nanofiber is not visible due to high-temperature hydrothermal and surface-coated nano sheets, and the plush-shaped 'petals' growing on the substrate cover almost all positions, so that the specific surface area of the final product is further improved again. The increase of the specific surface area further enables Zn of the active material in the charge and discharge process²⁺The ion is easy to be extracted, the contact between active substance and electrolyte is increased, and Zn is shortened²⁺Diffusion path of ions, thereby increasing Zn²⁺Electrochemical performance of the ion battery. When the image is magnified to 50000 times, a single VO can be clearly seen₂The complete shape of the nanometer flower structure has a plurality of strip bamboo leaf-shaped petals which are overlapped together and grow on a trunk, so that the growth process of the crystal shape can be deduced. During the growth of the structure, a main shaft is arranged and radially extends to the outside of the space, and during the extension process, a bamboo leaf-shaped dendritic crystal structure extends from the outer wall side of the main shaft to the periphery to form so-called 'petals', and finally a single 'test tube brush' -shaped nanometer flower is formed. The data in XRD diffraction pattern show that VO is₂Under the conditions of high temperature and high pressure of hydrothermal reaction, the crystal shows the growth mode related to the orientation of the {110} crystal face.

5. And (3) electrochemical performance testing: will finally obtain VO₂After the nanoflower material, ketjen black and PVDF were mixed and ground in a mass ratio of 7:2:1, N-methyl-2-pyrrolidone (NMP) was diluted into a slurry in a ratio of PVDF (1: 43) and stirred for 24 hours. Coating the stirred slurry on a Ti foil, pre-drying, putting into a vacuum drying oven, drying at 90 ℃ for 12 hours, taking out a dried pole piece, punching into a wafer with the diameter of 12mm, and performing Zn-VO (zinc-vanadium) in a common environment (without a glove box)₂And (3) assembling the half cell, wherein the counter electrode is a polished zinc sheet, the diaphragm is a Whatman glass fiber membrane, and the electrolyte is zinc sulfate aqueous solution. The assembled cell was subjected to a standing treatment for 12 hours, followed by various tests for electrochemical properties. Using an electrochemical workstation (CHI 604E, China) and blueThe electric test equipment (Land CT 2001A, Wuhan, China) performs performance tests such as cyclic performance analysis, multiplying power performance analysis, voltammetry analysis and the like on the battery, and the test voltage range is set to be 0.4V-1.4V.

VO described above₂The nano flower material has a current density of 500mA g^-1And 5A g^-1The cyclic performance at that time is shown in (a) and (b) in FIG. 5, respectively, and the VO is shown in (a) in FIG. 5₂The nano flower material has excellent Zn storage²⁺Capacity, and excellent cycle performance. At a current density of 500mA g^-1Under the action of the lithium ion battery, when the charge-discharge voltage range is 0.4-1.4V, the first discharge capacity is 283mAhg^-1The discharge capacity decreases somewhat as charging and discharging proceeds, which is a very normal phenomenon attributed to Zn²⁺Irreversible intercalation, interface formation between solid and electrolyte, and other loss phenomena. After a plurality of discharge cycle periods, the crystal structure of the active material is stable, the specific capacity descending trend is stable, the capacity of more than 130mAh g < -1 > can be maintained at 110 circles, and the good cycle performance is represented.

In FIG. 5 (b), the current density was 5A g^-1Under the condition (2), similar to the condition of low current, the first discharge capacity is higher, and the first-circle battery has 253mAh g^-1The capacity of the battery decreased within the initial 20 cycles down to 210mAh g^-1About, the reduction range of the current is even more than the low current condition, more than 40mAh g^-1The phenomenon is caused by that the transformation rate of crystal lattices is accelerated under the condition of high current, but in the subsequent circulation process, under the condition of high current, the circulation performance of the battery is obviously enhanced, and 100mAh g can be still maintained for more than 800 circles^-1The discharge specific capacity of the nano flower material is about, which shows that the nano flower material has good cycle performance under heavy current.

FIG. 6 shows VO₂Circulation rate performance, VO, of the nanoflower material₂Besides excellent Zn storage of nano material²⁺Besides the capability, the material also has excellent rate capability. This example is for VO during the cycle₂Button cell assembled by nano flower active material has been implementedThe test result shown in FIG. 6 shows that when the current density is 100mA g^-1VO when tested under the conditions₂The capacity of the nano flower material reaches 301 mAhg < -1 >, and the subsequent current density is 200mA g^-1、500 mA g^-1、1A g^-1、2A g^-1The capacity of (2) is reduced with the increase of current in charging and discharging, but has good stability even at 2A g^-1At the current level of VO₂The nanoflower material still possessed a capacity of approximately 125 mAhg-1. When the current density is adjusted back to 100mA g^-1The capacity can still be recovered to 200 mAh g^-1The above. Its good rate performance is attributed to VO₂The extremely large specific surface area of the nanoflower material and the growth and attachment to the electrospinning matrix can limit the damage of the volume expansion or shrinkage of the nanoflower material during the embedding/extracting of zinc ions to the material structure to some extent, and avoid premature pulverization and peeling.

In FIG. 7, (a) is VO₂The first three cycles of Cyclic Voltammetry (CV) curves with a discharge window in the range of 0.4V to 1.4V were performed at a scanning speed with a current density of 0.1mV s-1 for the nanoflower electrode. From the data in the figure, the curve of the first circle is in poor coincidence with the curve of the second circle, and both the oxidation peak and the reduction peak are shifted to a large extent, which indicates that the electrode material has crystal structure and composition changes during the first cycle, while the second circle has better coincidence, which can indicate that the rocking chair reaction of ion intercalation and deintercalation in the same crystal is stable after the first cycle. In the first cycle curve, two reduction peaks appear at 0.58V and 0.89V, which respectively correspond to the process of zinc ion intercalation in two voltage intervals in the discharge process, i.e. the discharge process is a two-step reaction process. However, three oxidation peaks corresponding to the voltage interval of the discharging process exist in the charging stage, which indicates that the charging process is also a multi-step reaction process. The peaks of the curves of the second and third cycles in the graph are almost completely coincident, the curves are more coincident and close well, indicating that the electrode has stabilized at this point, and the oxidation peak isThe positions appear at 0.75V, 1.02V and 1.16V, indicating that the de-intercalation of zinc ions is a three-step reaction. Two reduction peaks are provided, and the deviation amount is small, so that the vanadium dioxide nanoflower electrode has strong reversible performance.

In FIG. 7, (b) is VO₂The current density of a half cell consisting of the electrode of the nano flower material and the zinc electrode is 200mA g^-1Under the condition of (1), the charge-discharge window of the charge-discharge curve of the first three circles is 0.4-1.4V. From the figure we can see that two weak discharge plateaus can be found near 1.04V and 0.745V, and two charging plateaus can be found at 0.941V and 1.138V, which is similar to the peak position in the CV curve, and is related to the property of the material itself. The first, second and third discharge cycles in the figure give 293.1, 284.8 and 279.2mAh g, respectively^-1The specific capacity of (a) corresponds to the redox reaction process in the CV. However, the charging specific capacities of the first three circles are all 310mAh g^-1Above, the lower coulombic efficiency may be due to Zn²⁺The irreversible ion trapping at the insertion point in the host structure is also related to VO in the CV test results₂The crystal changes in the initial turns. Furthermore, we can observe that almost no decrease in the specific discharge capacity of the battery occurs as the cycling process proceeds, indicating that the electrode material has good cyclability.

Since electrochemical impedance spectroscopy is one of the most powerful tools to study the electrochemical processes occurring at the electrode-electrolyte interface, such as charge transfer resistance, electronic resistance of the active material, diffusion, and resistance to zinc ion diffusion migration through the solid electrolyte phase interface film (SEI film). To detect the prepared VO₂The nano flower material has the relevant resistance performance, and EIS impedance detection is carried out. EIS comparison of electrostatic spinning products before and after hydrothermal reaction is utilized in a monitoring experiment to investigate influences of electrode morphology on factors such as impedance, ion transfer efficiency and the like. Since only one semicircular structure exists in fig. 8, the high frequency region and the middle frequency region can be combined into one composed of faraday impedance Zf and double electric layer capacitive reactance C_dParallel and series connected battery resistor R_ΩThe model of (1). The faradaic impedance can be divided into charge transfer resistance Rct associated with charge transfer and ion transferRelative impedance Z_wFurther, since the electric signal changes too fast in the high frequency region and zinc ions are not transferred in time, it can be considered that there is no impedance Z_w. The radius of the semicircular area in the figure is R_ct\2, the slope in the low frequency region represents the magnitude of Zw impedance, from which it is apparent that VO grows/adheres after hydrothermal reaction₂The spinning matrix has lower charge transfer resistance R_ctSimultaneously, the ion exchange impedance Z is lower in a low frequency region_w. From the results, the nano flower material after the hydrothermal reaction has better diffusion efficiency of charges and zinc ions than the substrate to a certain extent, which can be attributed to the fact that the specific surface area of the material is greatly improved by the nano flower structure, so that the electrolyte can fully infiltrate active substances, the zinc ion diffusion path is effectively shortened, and the Zn is greatly reduced²⁺Ion from VO₂The diffusion distance and energy barrier of the embedding/de-embedding in the crystal lattice are increased, and the stability and reversibility in the circulation process are improved.

In conclusion, VO having uniformity and extremely large specific surface area was prepared in the above examples₂The nano flower material is compared with the V-O compound used in the zinc ion battery in the prior art, because of the VO₂Gaps are filled among petal-shaped structures of the nano flower material, so that electrolyte can easily permeate into deep layers of the material, contact with active substances is increased, the specific surface area is further increased, and the electrochemical performance of the material is improved. In addition, the material has extremely large specific surface area, so that Zn can be stored in the charging and discharging process²⁺Ionic, and which has excellent electrical conductivity, may be Zn²⁺The ion and electron access provides a fast channel, thereby showing good cycle and rate performance in electrochemical tests.

The above embodiments are preferred implementations of the present invention, and the present invention can be implemented in other ways without departing from the spirit of the present invention.

Finally, it should be emphasized that some of the descriptions of the present invention have been simplified to facilitate the understanding of the improvements of the present invention over the prior art by those of ordinary skill in the art, and that other elements have been omitted from this document for the sake of clarity, and those skilled in the art will recognize that these omitted elements may also constitute the content of the present invention.

Claims

1. VO (volatile organic compound)₂The preparation method of the nano flower material is characterized by comprising the following steps of:

step one, preparing a hydrothermal reaction solution:

step two, preparing VO by hydrothermal method₂The nano flower material:

2. Making VO according to claim 1₂Method for preparing nanoflower materials, characterized in that V is used as the substrate for hydrothermal reaction in step 2.1₂O₅The preparation method of the electrostatic spinning fiber comprises the following steps:

3. Making VO according to claim 1₂The method for preparing the nano flower material is characterized by comprising the following steps: in step 1.1, the V₂O₅Powder and H₂C₂O₄·2H₂The mass ratio of O is 2: 3.

4. making VO according to claim 3₂The method for preparing the nano flower material is characterized by comprising the following steps: in the mixed solvent of the step 1.1, the volume ratio of distilled water to ethanol is 3: 14.

5. Making VO according to claim 4₂The method for preparing the nano flower material is characterized by comprising the following steps: in step 1.1, H₂O₂The concentration of the solution is 10-50%.

6. Making VO according to claim 5₂The method for preparing the nano flower material is characterized by comprising the following steps: in step 2.1, the temperature of the hydrothermal reaction is 180 ℃ and the reaction time is 3 h.

7. Making VO according to claim 2₂The method for preparing the nano flower material is characterized by comprising the following steps: the polyvinylpyrrolidone added in step b had an average molecular weight of 1300000.

8. Making VO according to claim 7₂The method for preparing the nano flower material is characterized by comprising the following steps: in the step c, the spinning precursor solution is added into an injector during electrostatic spinning, the injector is arranged on an injection pump, and the feeding speed is set to be 0.1-6.6ml h^-1Between the needle and the collection roller 5-32 timeskV voltage, and receiving distance of 5-30 cm.

9. VO (volatile organic compound)₂The nano flower material is characterized in that: prepared by the method of any one of claims 1 to 8.

10. VO according to claim 9₂The application of the nano flower material as the anode material of the zinc ion battery.