Preparation method of three-dimensional microstructure vanadium pentoxide composite cathode material and application thereof in zinc ion battery

Abstract

The application belongs to the field of aqueous zinc ion batteries, and particularly relates to a preparation method of a three-dimensional microstructure vanadium pentoxide composite cathode material and application of the three-dimensional microstructure vanadium pentoxide composite cathode material in zinc ion batteries. The vanadium oxide is dispersed in water, polypyrrole is added and heated and stirred, the precipitate is collected, and after washing and drying, the polypyrrole is in-situ reacted with polyaniline to be compounded, and calcination is performed under air to further oxidize vanadium ions and reduce the water content, so as to obtain a ternary composite material of polyaniline-poly pyrrole organic polymer composite vanadium pentoxide; the polypyrrole embedded in the main material can not only expand the interlayer spacing, but also improve the conductivity of the mixed cathode. In addition, the introduction of the PANI chain provides more zinc storage sites, and the in-situ polymerization of polyaniline on the vanadium-based material produces 3D amorphous nanofibers, the nanofibers are randomly stacked to form an open interpenetrating network structure, the interface of the composite material is optimized, and a more effective ion migration path and a complete structure are provided.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of aqueous zinc-ion batteries, and particularly relates to a preparation method and application of a composite positive electrode material of three-dimensional microstructure vanadium pentoxide. BACKGROUND

[0002] Aqueous zinc-ion batteries (AZIBs) are a kind of secondary batteries with high safety and low cost, but the strong static interaction of the main material and the suboptimal cycle life hinder the development of AZIBs. Therefore, developing a new type of positive electrode material with stable structure, excellent capacity and high energy density will be an attractive research direction. Currently, the research on AZIBs positive electrode materials mainly focuses on manganese-based materials, vanadium-based compounds and prussian blue analogues. Due to the open framework crystal structure and multiple oxidation states of vanadium, vanadium-based materials usually have high capacity and excellent rate performance.

[0003] The most stable component in the vanadium oxide system is V2O5, and the research on performance improvement is still continuing. Although V2O5 has a series of advantages, it is plagued by poor cycle stability, low ionic conductivity, slow Zn 2+ diffusion and low electronic content. In order to solve these problems, the research on vanadium-based materials mainly focuses on the strategy of expanding the interlayer spacing and optimizing the interface to improve the cycle life and rate performance. However, the introduction of "lubricant" often causes the dissolution of vanadium-based materials, resulting in a significant reduction in battery capacity.

[0004] Previous studies have shown that the introduction of conductive materials such as carbon nanotubes, graphene and polymers into vanadium oxides can effectively improve the electrochemical performance of the battery. For example, CN202111662109.8 and CN202011069581.6 confirmed that the introduction of PANI can improve the performance of the battery by increasing oxygen vacancies and interface optimization. However, due to the problems of slow electronic migration path and vanadium dissolution, the rapid decay of battery capacity limits its further application.

[0005] How to further design a vanadium-based cathode stable skeleton structure with efficient migration channels to improve the structural stability and zinc ion storage capacity of the composite material is the problem to be solved by the present application. SUMMARY

[0006] In order to solve the above problems, the present application proposes to prepare a ternary composite material of two organic polymers (polyaniline (PANI), polypyrrole (PPy)) and vanadium pentoxide, and to design a vanadium-based cathode stable skeleton structure with efficient migration channels to improve the structural stability and zinc ion storage capacity of the composite material.

[0007] The technical scheme of the present application is as follows:

[0008] The present application aims to overcome the defects of the prior art, and provides a preparation method of an organic polymer composite vanadium pentoxide material.

[0009] Another object of the present application is to provide applications of two kinds of organic polymer composite vanadium pentoxide materials.

[0010] A preparation method of an organic polymer composite vanadium pentoxide material, comprising the following steps:

[0011] (1) Disperse the inorganic vanadium source in deionized water, add polypyrrole and stir under oil bath (80℃) for 20 minutes, collect the precipitate by vacuum filtration, wash with deionized water and anhydrous ethanol for several times, and vacuum dry at 60℃ for 10h.

[0012] (2) Disperse the dried material of step (1) in deionized water to obtain a dispersion liquid, dissolve APS in HCl aqueous solution to form solution A, and perform magnetic stirring in an ice bath to achieve uniform dispersion; disperse aniline monomer in HCl aqueous solution to form solution B, and stir it uniformly in an ice bath; add solution B and solution A to the dispersion liquid, and stir in an ice bath for 6 hours, then centrifuge the obtained product with deionized water and ethanol for three times, and dry in a vacuum oven at 60℃ for 10 hours.

[0013] (3) Further calcine the above-mentioned material in air at 100-300℃ for 0.5-5h to further oxidize vanadium ions and reduce the water content, and the heating rate is 2℃·min -1 , to obtain a product of ternary composite material of organic polymer (polyaniline, polypyrrole) composite vanadium pentoxide;

[0014] Further, the inorganic vanadium source compound of step (1) is selected from one of V2O5, vanadate. Further preferably, the inorganic vanadium source compound is V2O5.

[0015] Further, the mass ratio of the inorganic vanadium source compound to polypyrrole is 2-5:0.5-1. The molar ratio of the inorganic vanadium source compound to aniline is 1-4:0.5-2; and the molar ratio of ammonium persulfate to aniline monomer is 1:1.

[0016] Further, the concentration of hydrochloric acid is 0.01-1mol / L. Further preferably, the concentration of hydrochloric acid for synthesizing the organic polymer composite material is 0.02mol / L.

[0017] Further, the ice bath condition refers to controlling the temperature of the reaction at 0-5℃.

[0018] Further, as preferred, the calcination temperature of the inorganic vanadium compound precursor and the organic polymer is 200℃, the calcination time is 2h, and the heating rate is 2℃·min -1 .

[0019] The organic polymer composite vanadium pentoxide material prepared by the preparation method is applied in a positive electrode of a zinc ion battery.

[0020] The embedding of polypyrrole into the main material can not only expand the interlayer spacing, but also improve the conductivity of the mixed cathode. In addition, the introduction of the PANI chain provides more zinc storage sites, and the polyaniline is in-situ reacted on the prepared vanadium-based material-polypyrrole material to generate 3D amorphous nanofibers, and the nanofibers are randomly stacked to form an open interpenetrating network structure, which provides a stable channel for zinc ion migration, optimizes the interface of the composite material, and provides a more effective ion migration path and a complete structure.

[0021] The organic polymer composite vanadium pentoxide material prepared by the preparation method is applied in a positive electrode of a zinc ion battery.

[0022] 1、The organic polymer composite vanadium pentoxide material prepared by the preparation method can combine the advantages of inorganic vanadium oxide and organic polymer, and the preparation process is simple and low in cost.

[0023] 2、The specific organic polymer in the application can not only form hydrogen bonds with the vanadium oxide framework to maintain the structural stability of the material, but also better expand the interlayer spacing of vanadium pentoxide, improve the zinc ion deintercalation kinetics, and thus obtain excellent cycle stability and rate performance.

[0024] 3、The organic polymer polyaniline in the application has active sites and can also participate in the zinc ion storage process to provide a certain capacity, avoid the reduction of the theoretical capacity of the material due to the occupation of the reaction sites by metal ions, and thus make the vanadium pentoxide material have high specific capacity. The in-situ polymerization of polyaniline on the vanadium-based-polypyrrole material generates 3D amorphous nanofibers with a diameter of about 200nm, and the nanofibers are randomly stacked to form an open interpenetrating network structure, which provides a stable channel for zinc ion migration, and the composite sample presents a rough and irregular distribution on the surface.

[0025] 4、The organic polymer introduced in the application itself has high conductivity, and the prepared ternary composite material exhibits excellent kinetic performance. DETAILED DESCRIPTION

[0026] Figure 1 The XRD graphs of the sample of example 1, example 2 and example 3, polyaniline and polypyrrole polymer in the application.

[0027] Figure 2 The SEM pictures of example 1 and example 3 in the application.

[0028] Figure 3 The low-magnification SEM photo of example 3 in the application.

[0029] Figure 4 The figure is the zinc storage rate performance graph of example 1, example 2 and example 3 in the application.

[0030] Figure 5 The figure is the zinc storage cycle performance graph of example 1, example 2 and example 3 in the application at 0.5A·g -1 The figure is the zinc storage cycle performance graph of example 1, example 2 and example 3 in the application at 0.5A·g

[0031] Figure 6 The figure is the high current cycle performance graph of example 3 in the application.

[0032] Figure 7 The figure is the zinc storage cycle performance graph of example 4 in the application at 0.5A·g -1 The figure is the zinc storage cycle performance graph of example 4 in the application at 0.5A·g

[0033] Figure 8 The figure is the zinc storage cycle performance graph of example 5 in the application at 0.5A·g -1 The figure is the zinc storage cycle performance graph of example 5 in the application at 0.5A·g

[0034] Figure 9 The figure is the zinc storage cycle performance graph of comparative example 1 in the application at 0.5A·g -1 The figure is the zinc storage cycle performance graph of comparative example 1 in the application at 0.5A·g

[0035] Figure 10 The figure is the zinc storage cycle performance graph of comparative example 2 in the application at 0.5A·g -1 The figure is the zinc storage cycle performance graph of comparative example 2 in the application at 0.5A·g

[0036] Figure 11 The figure is the zinc storage cycle performance graph of comparative example 3 in the application at 0.5A·g -1 The figure is the zinc storage cycle performance graph of comparative example 3 in the application at 0.5A·g

[0037] Figure 12 The figure is the zinc storage cycle performance graph of comparative example 4 in the application at 0.5A·g -1 The figure is the zinc storage cycle performance graph of comparative example 4 in the application at 0.5A·g

[0038] Figure 13 The figure is the zinc storage cycle performance graph of comparative example 5 in the application at 0.5A·g -1 The figure is the zinc storage cycle performance graph of comparative example 5 in the application at 0.5A·g DETAILED DESCRIPTION

[0039] The technical solutions of the application are further described and explained in the following detailed description with reference to the accompanying drawings.

[0040] Example 1:

[0041] Example 1 directly uses the vanadium pentoxide produced by Maclean, which is counted as VO.

[0042] Example 2:

[0043] (1) 80 mg of polypyrrole was added into a solution of 363 mg (2 mmol) of vanadium oxide precursor (V2O5) dispersed in deionized water, and was fully stirred at 80°C. The obtained product was washed with deionized water and ethanol for three times, and was dried in a vacuum oven at 60°C for 10 hours.

[0044] (2) The above material was further calcined in air at 200°C for 2h with a heating rate of 2°C·min -1 to further oxidize vanadium ions and reduce the content of water, to obtain a binary composite PVO.

[0045] Example 3:

[0046] (1) 80 mg of polypyrrole was added into a solution of 363 mg (2 mmol) of vanadium oxide precursor (V2O5) dispersed in deionized water, and was fully stirred at 80°C. The obtained product was washed with deionized water and ethanol for three times, and was dried in a vacuum oven at 60°C for 10 hours.

[0047] (2) Then the above product PVO was dispersed in deionized water to obtain a PVO dispersion, 0.5 mmol of APS was dissolved in 0.02 mol / L of aqueous hydrochloric acid solution to form solution A. Magnetic stirring was carried out in an ice bath to achieve uniform dispersion, and 0.5 mmol of aniline monomer was dispersed in 0.02 mol / L of aqueous hydrochloric acid solution to form solution B, which was stirred in an ice bath for 10 minutes. Solution B, solution A was added to the PVO dispersion, and was stirred in an ice bath for 6 hours. The obtained product was centrifuged with deionized water and ethanol for three times, and was dried in a vacuum oven at 60°C for 10 hours. -1 HCl aqueous solution to form solution B, which was stirred in an ice bath for 10 minutes. Solution B, solution A was added to the PVO dispersion, and was stirred in an ice bath for 6 hours. The obtained product was centrifuged with deionized water and ethanol for three times, and was dried in a vacuum oven at 60°C for 10 hours. -1 HCl aqueous solution to form solution B, which was stirred in an ice bath for 10 minutes. Solution B, solution A was added to the PVO dispersion, and was stirred in an ice bath for 6 hours. The obtained product was centrifuged with deionized water and ethanol for three times, and was dried in a vacuum oven at 60°C for 10 hours.

[0048] (3) The above material was further calcined in air at 200°C for 2h with a heating rate of 2°C·min -1 to further oxidize vanadium ions and reduce the content of water, to obtain a ternary composite PPVO.

[0049] (1) 2 mmol of vanadium oxide precursor (V2O5) was dispersed in 20 mL of deionized water, 114 mg (0.5 mmol) of ammonium persulfate (APS) and 46 mg (0.5 mmol) of aniline were respectively dissolved in hydrochloric acid with a concentration of 0.02 mol / L, and then were added into the vanadium oxide precursor dispersion, which was stirred in an ice bath for 24 hours, and then was washed with water and centrifuged for three times, and was dried in a vacuum oven at 60°C for 10 hours, to obtain a product of a composite of polyaniline and vanadium pentoxide;

[0050] (2) The above material was further calcined in air at 200°C for 2 hours with a heating rate of 2°C·min-1 to further oxidize vanadium ions and reduce water content, thus obtaining the binary composite material PVO.

[0051] Example 5:

[0052] (1) 2 mmol of vanadium oxide precursor (V2O5) was dispersed in 10 mL of deionized water. 0.5 mmol of ammonium persulfate (APS) and 0.5 mmol of aniline were dissolved in 0.02 mol / L hydrochloric acid and then added to the vanadium oxide precursor dispersion. The mixture was stirred in an ice bath for 24 h. After washing with water and centrifuging three times, the mixture was dried in a vacuum oven at 60 °C for 10 h to obtain the product, a complex of polyaniline and vanadium pentoxide.

[0053] (2) Disperse the product from step (1) completely in deionized water, add 80 mg of polypyrrole, and stir thoroughly at 80 °C. Wash the resulting product three times with deionized water and ethanol, and dry it in a vacuum oven at 60 °C for 10 hours.

[0054] (3) The dry substance was further calcined in air at 200°C for 2 hours, with a heating rate of 2°C·min. -1 To further oxidize vanadium ions while reducing water content, a ternary composite material 2-PPVO was obtained.

[0055] Comparative Example 1

[0056] (1) First, 80 mg of polypyrrole was added to a deionized water solution containing 2 mmol of zinc vanadate, and the mixture was stirred completely at 80 °C. The resulting product was washed three times with deionized water and ethanol, and dried in a vacuum oven at 60 °C for 10 hours to obtain a complex of zinc vanadate and polypyrrole.

[0057] (2) Then disperse the product of step (1) in deionized water, and dissolve 0.5 mmol APS in 0.02 mol·L⁻¹ water. -1 Solution A is formed in hydrochloric acid aqueous solution. To achieve uniform dispersion, 0.5 mmol of aniline monomer is dispersed in 0.02 mol·L⁻¹ solution by magnetic stirring in an ice bath. -1 Solution B is formed in an aqueous HCl solution and stirred in an ice bath for 10 minutes. Solution B is then rapidly added to solution A and stirred in an ice bath for 6 hours. The resulting product is centrifuged three times with deionized water and ethanol, and dried in a vacuum oven at 60°C for 10 hours to obtain the ternary complex of zinc vanadate.

[0058] (3) The above material was further calcined in air at 200°C for 2 hours, with a heating rate of 2°C·min. -1 To reduce the water content, the final composite material PPVO was obtained.

[0059] Comparative Example 2

[0060] (1) First, 80 mg of polypyrrole was added to a deionized solution water dispersed with 1 mmol of vanadium oxide precursor, and completely stirred at 80°C. The resulting product was washed with deionized water and ethanol three times, and dried in a vacuum oven at 60°C for 10 hours to obtain a product PVO.

[0061] (2) Then, the product PVO was dispersed in deionized water to obtain a PVO dispersion liquid, 0.5 mmol of APS was dissolved in 0.02 mol·L -1 of aqueous hydrochloric acid to form a solution A. Magnetic stirring was carried out in an ice bath to achieve uniform dispersion, and 0.5 mmol of aniline monomer was dispersed in 0.02 mol·L -1 of aqueous hydrochloric acid to form a solution B, which was stirred in an ice bath for 10 minutes. Solution B, solution A was added to the PVO dispersion liquid, and stirred in an ice bath for 6 hours. The resulting product was centrifuged with deionized water and ethanol three times, and dried in a vacuum oven at 60°C for 10 hours to obtain a product PPVO.

[0062] (3) The above material was further calcined in air at 200°C for 2h, with a heating rate of 2°C·min -1 to further oxidize vanadium ions while reducing the water content, to obtain a final composite material PPVO.

[0063] Comparative Example 3

[0064] (1) 30 mg of polyethylene was added to a solution of deionized water dispersed with 2 mmol of vanadium oxide precursor, and completely stirred at room temperature for 8h. The resulting product was washed with deionized water and ethanol three times, and dried in a vacuum oven at 60°C for 10 hours to obtain a product of a composite of polyethylene and vanadium pentoxide.

[0065] (2) The above material was further calcined in air at 200°C for 2h, with a heating rate of 2°C·min -1 to further oxidize vanadium ions while reducing the water content, to obtain a composite material of vanadium oxide and polyethylene.

[0066] Comparative Example 4

[0067] (1) First, 80 mg of polypyrrole was added to a deionized solution water dispersed with 2 mmol of vanadium oxide precursor, and completely stirred at 80°C. The resulting product was washed with deionized water and ethanol three times, and dried in a vacuum oven at 60°C for 10 hours to obtain a product PVO.

[0068] (2) Then, the product PVO was dispersed in deionized water to obtain a PVO dispersion liquid, 0.5 mmol of APS was dissolved in 0.05 mol·L-1 Solution A was formed in aqueous hydrochloric acid. 0.5 mmol of aniline monomer was dispersed in 0.05 mol·L -1 Solution B was formed in aqueous hydrochloric acid and stirred in an ice bath for 10 minutes. Solution B, solution A were added to the PVO dispersion, stirred in an ice bath for 6 hours, the resulting product was centrifuged three times with deionized water and ethanol, dried in a vacuum oven at 60°C for 10 hours to obtain the product PPVO.

[0069] (3) The above material was further calcined in air at 200°C for 2h, the heating rate was 2°C·min -1 to further oxidize vanadium ions and reduce the water content, to obtain the final composite material PPVO.

[0070] Comparative Example 5

[0071] (1) First, 2 mmol of vanadium oxide precursor was dispersed in deionized water, 80 mg of polypyrrole was added, and stirred completely at 80°C. The resulting product was washed three times with deionized water and ethanol, and dried in a vacuum oven at 60°C for 10 hours to obtain the product PVO.

[0072] (2) Then the product PVO was dispersed in deionized water to obtain a PVO dispersion, 0.5 mmol of APS was dissolved in 0.02 mol·L -1 Solution A was formed in aqueous hydrochloric acid. 0.5 mmol of aniline monomer was dispersed in 0.02 mol·L -1 Solution B was formed in aqueous hydrochloric acid and stirred in an ice bath for 10 minutes. Solution B, solution A were added to the PVO dispersion, stirred in an ice bath for 6 hours, the resulting product was centrifuged three times with deionized water and ethanol, dried in a vacuum oven at 60°C for 10 hours to obtain the product PPVO.

[0073] (3) The above material was further calcined in air at 350°C for 2h, the heating rate was 2°C·min -1 to further oxidize vanadium ions and reduce the water content, to obtain the final composite material PPVO.

[0074] The products prepared in the above examples and comparative examples were applied to the positive electrode material of the battery, as follows: (1) Preparation of electrolyte

[0075] Zinc ion storage electrolyte: deionized water as solvent, zinc trifluoromethanesulfonate as zinc salt, 3 mol·L -1 The electrolyte was prepared. This electrolyte is mainly used for zinc ion battery assembly and zinc ion storage.

[0076] (2) Preparation of positive electrode sheet

[0077] The organic polymer composite vanadium pentoxide positive active material, conductive agent acetylene black, PVDF binder were mixed in a mass ratio of 7:2:1, N-methyl pyrrolidone was added, and stirred uniformly to obtain a slurry. The slurry was uniformly coated on a stainless steel mesh, and placed in a 60°C vacuum drying oven for 10h.

[0078] (3) Preparation of battery

[0079] The positive electrode sheet, negative electrode sheet, glass fiber separator, gasket and electrolyte were assembled into a CR2016 type button cell, the cell was sealed, and the electrochemical performance test was carried out after standing for 2h

[0080] The experimental results of the above examples and comparative examples are as follows:

[0081] Figure 1 The XRD patterns of the five samples of Example 1, Example 2, Example 3, polypyrrole and polyaniline 5. From the analysis of the figure, PPy belongs to a random polymer molecule, and the molecular chain has no crystallinity, and there is only one amorphous broad peak on the XRD curve. Compared with the original VO, the crystallinity of the composite PVO is lower. The final product PPVO has improved crystallinity due to calcination, and part of the water and organic matter in the sample is removed. And consistent with the diffraction peak position in the standard card (JCPDS 41-1426) of VO, it is proved that the structure of VO is not destroyed or covered during the compounding process.

[0082] Figure 2 The 200 nanometer SEM photos of the organic polymer composite vanadium pentoxide (PPVO) prepared in Example 3 and the two samples of vanadium pentoxide of Example 1. From the analysis of the figure, the vanadium pentoxide sample without composite organic polymer has a length of 1 micrometer and a nanorod structure of about 50 nanometers wide. Due to the incorporation of multiple polymers, in-situ polymerization of polyaniline on vanadium-based materials produces 3D amorphous nanofibers with a diameter of about 200 nm, which randomly stack to form an open interpenetrating network structure, providing a stable channel for zinc ion migration. The composite sample presents a rough and irregular distribution on the surface.

[0083] Figure 3 The 2 micrometer SEM photo of the organic polymer composite vanadium pentoxide (PPVO) prepared in Example 3. From the figure, it can be seen that the composite vanadium pentoxide presents a random distribution of clusters in different sizes of spherical shape.

[0084] Figure 4 The rate performance graph of the samples of Example 1, Example 2, Example 3, the specific capacity of PPVO of Example 3 is 466.5mAh·g -1 at a current density of 0.1A·g-1 , to 5 A·g -1 The specific capacity at the current density is 196.7 mAh·g -1 When the current density returns to 0.1 A·g -1 The specific capacity at the current density does not have any decay, and the reversible capacity can still be maintained at 481.3 mAh·g -1 The PVO of Example 2 has a specific capacity of 275.5 mAh·g -1 at the current density of 0.1 A·g -1 , to 5 A·g -1 The specific capacity at the current density is 94.7 mAh·g -1 When the current density returns to 0.1 A·g -1 The specific capacity at the current density can still be maintained at 325.3 mAh·g -1 . It has excellent rate performance, but the specific capacity is slightly lower due to the certain mass ratio of PPy. The VO of Example 1 has a specific capacity of 321.5 mAh·g -1 at the current density of 0.1 A·g -1 , to 5 A·g -1 The specific capacity at the current density is 146.7 mAh·g -1 When the current density returns to 0.1 A·g -1 The specific capacity at the current density can still be maintained at 288.3 mAh·g -1 . The specific capacity has obvious decay, and the decay continues after returning to 0.1 A·g -1 By comparison, it can be proved that the PPVO has excellent resistance and high specific capacity.

[0085] Figure 5 The figure is the zinc storage cycle performance of the samples of Example 1, Example 2 and Example 3. As can be seen from the figure, the cycle performance and reversible capacity of the PPVO of Example 3 are obviously improved. At the current density of 0.5 A·g -1 , after 500 cycles, the reversible capacity can be maintained at 372.5 mAh·g -1 , the capacity retention rate is 86.7%, and the capacity retention rate and zinc ion storage efficiency are obviously higher than those of the other two samples. At the same time, the cycle performance of the PVO of Example 2 is also improved to a certain extent. At the current density of 0.5 A·g -1 , after 500 cycles, the reversible capacity can be maintained at 285.5 mAh·g -1 , and the capacity retention rate is 66.7%. The VO has an ultra-high initial capacity, but at the current density of 0.5 A·g -1 , after 500 cycles, the reversible capacity is only 205.5 mAh·g -1, the capacity retention rate is 40.7%. By comparison, it can be proved that PPVO has excellent cycle performance, which is due to the optimization of its structure and the enhancement of its conductivity.

[0086] Figure 6 The cycle performance of PPVO prepared in Example 3 at a large current density is shown in the figure. After 3000 cycles at 3 A·g -1 , the reversible capacity can be maintained at 288.5 mAh·g -1 , and the capacity retention rate is 87.7%.

[0087] Figure 7 The cycle performance of Example 4 at 0.5 A·g -1 , the initial specific capacity can reach 484.1 mAh·g -1 , after 500 cycles, the reversible capacity is 355.3 mAh·g -1 , the capacity retention rate is 73.4%, and the fluctuation of coulombic efficiency during the cycle process is particularly large. This proves that the addition of PANI has little effect on the theoretical specific capacity of the positive electrode material, but the cycle stability needs to be improved.

[0088] Figure 8 The cycle performance of Example 5 at 0.5 A·g -1 , the specific capacity can reach 308.9 mAh·g -1 , after 500 cycles, the reversible capacity is 209.6 mAh·g -1 , the capacity retention rate is 59.4%. The rapid decline of its capacity is due to the destruction of the structure of polyaniline caused by the heating process of subsequent composite polypyrrole under the condition of pre-composite polyaniline.

[0089] Figure 9 The cycle performance of Comparative Example 1 at 0.5 A·g -1 , due to the low theoretical specific capacity and unstable structure of zinc vanadate, the initial specific capacity can reach 318.7 mAh·g -1 , after 500 cycles, the reversible capacity is 189.6 mAh·g -1 , the capacity retention rate is 67.8%.

[0090] Figure 10 The cycle performance of Comparative Example 2 at 0.5 A·g -1 , the initial capacity is 62.7 mAh g -1 , after 500 cycles, the reversible capacity is 56.1 mAh·g -1 , and the specific capacity exhibited is low. Due to the too low content of active material, the specific capacity is low.

[0091] Figure 11 For Comparative Example 3 at 0.5 A·g -1 The cycle performance graph at a current density of 0.5 A·g -1 , the battery was damaged when cycled to 145 cycles.

[0092] Figure 12 For Comparative Example 4 at 0.5 A·g -1 The cycle performance graph at a current density of 0.5 A·g -1 , after 500 cycles, the reversible capacity was 285.6 mAh·g -1 , the capacity retention rate was 71.1%. The preparation process of polyaniline requires hydrochloric acid, but the structure of vanadium-based materials is easily destroyed under acidic conditions, so the concentration of hydrochloric acid needs to be controlled. Under the condition of 0.05 mol·L -1 aqueous hydrochloric acid, the prepared positive electrode has a relatively high initial capacity, but the capacity retention rate needs to be improved.

[0093] Figure 13 For Comparative Example 5 at 0.5 A·g -1 The cycle performance graph at a current density of 0.5 A·g -1 , after 500 cycles, the reversible capacity was 245.3 mAh·g -1 , the capacity retention rate was 66.7%. Because the temperature is too high, the organic matter is burned off, resulting in unstable structure and low capacity retention rate.

[0094] The present invention is a PPVO composite electrode with a three-dimensional skeleton structure. By introducing highly conductive organic polymers PPy and PANI as the main support material, the low conductivity and solubility problems of vanadium pentoxide are improved. Due to the efficient and stable Zn 2+ migration channel, PPVO exhibits excellent ion transfer efficiency, thereby improving the performance of the battery in terms of cycle and rate capability. The optimized PPVO has high specific capacity (442.9 mAh·g -1 at 0.5 A·g -1 ), excellent rate performance, and a capacity retention rate of 87.7% after 3000 cycles at 3 A·g -1 .

Claims

1. A method for preparing a composite cathode material of three-dimensional microstructure vanadium pentoxide, characterized in that: The preparation steps are as follows: (1) dispersing an inorganic vanadium source in deionized water, adding polypyrrole and stirring under heating, filtering after stirring, collecting the precipitate, washing with distilled water and anhydrous ethanol for several times, and vacuum drying; (2) dispersing the dried product into deionized water to obtain a dispersion liquid, dissolving ammonium persulfate in an aqueous hydrochloric acid solution, stirring uniformly in an ice bath to form solution A; dispersing an aniline monomer into an aqueous hydrochloric acid solution, stirring uniformly in an ice bath to form solution B; adding solution B and solution A into the dispersion liquid, stirring and reacting in an ice bath, centrifuging and drying the reaction product after reaction; (3) calcining the dried product of step (2) at 100-300℃ in air for 0.5-5h to obtain a three-dimensional microstructure vanadium pentoxide composite positive electrode material.

2. The method according to claim 1, wherein the method comprises the steps of: In step (1), the inorganic vanadium source is selected from one of V2O5 and vanadate; the mass ratio of the inorganic vanadium source compound to polypyrrole is 2-5:0.5-1. ​ 3. The method of claim 1, wherein the method further comprises the steps of: The molar ratio of the inorganic vanadium source compound to aniline is 1-4:0.5-2; the molar ratio of ammonium persulfate to aniline monomer is 1:

1. ​ 4. The method of claim 1, wherein the method further comprises the steps of: preparing a solution of vanadium pentoxide and a surfactant; and adding the solution to the mixture of claim 1. In step (2), the concentration of the aqueous hydrochloric acid solution is 0.01-1mol / L.

5. The method of claim 4, wherein the method further comprises the step of: In step (2), the concentration of the aqueous hydrochloric acid solution is 0.02mol / L. ​ 6. The method of claim 1, wherein the method further comprises the steps of: mixing the vanadium pentoxide with the conductive material; and mixing the vanadium pentoxide with the binder. Step (3) the calcination temperature is 200℃, the calcination time is 2h, and the heating rate is 2℃·min -1 .

7. The three-dimensional microstructure vanadium pentoxide composite positive electrode material prepared by the method according to any one of claims 1-6.

8. The application of the three-dimensional microstructure vanadium pentoxide composite positive electrode material prepared by the method according to any one of claims 1-6 in a zinc ion battery.

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