Vanadium-based metal oxide (at) rGO composite aerogel as well as preparation method and application thereof

Abstract

The invention discloses vanadium-based metal oxide (at) rGO composite aerogel as well as a preparation method and application thereof. The preparation method comprises the following steps: 1) dissolving a vanadium-based oxide precursor in an organic solvent, and carrying out microwave reaction to obtain vanadium-based metal oxide nanoparticles; the vanadium-based oxide precursor comprises at least one of vanadium oxytriisopropoxide, vanadium oxytrichloride, ammonium metavanadate and vanadyl oxalate; the vanadium-based metal oxide nanoparticles are selected from at least one of V2O3, VO1.52 (OH) 0.77 and VO2; and 2) dispersing the vanadium-based metal oxide nanoparticles in a dispersion liquid of graphene oxide nanosheets, carrying out electrostatic self-assembly, freeze-drying, and calcining in a protective atmosphere to obtain the vanadium-based metal oxide (at) rGO composite aerogel. The vanadium-based metal oxide (at) rGO composite aerogel prepared by the method can effectively improve the discharge capacity, the rate capability and the cycle performance of the material.

Description

Technical Field

[0001] The present invention belongs to the technical field of zinc ion batteries and relates to a vanadium-based metal oxide @rGO composite aerogel and a preparation method and application thereof. Background Art

[0002] As society's reliance on fossil fuels increases and non-renewable energy sources gradually deplete, the development of energy storage devices compatible with clean energy sources such as solar and wind power has become urgent. Currently, lithium-ion batteries (LIBs) are widely used in various fields due to their high discharge capacity and long cycle life. However, the use of organic electrolytes can easily cause combustion and lead to safety accidents. Furthermore, the water-free and oxygen-free manufacturing environment increases the production cost of LIBs, hindering their development.

[0003] In recent years, researchers have made significant progress in developing aqueous batteries with high safety, including monovalent aqueous Na + , K + Batteries, divalent aqueous Zn 2+ Mg 2+ Batteries and polyvalent aqueous Al 3+ Batteries. Among them, due to their low cost, low flammability, high theoretical specific capacity (820mAh g -1 ) and low redox potential (-0.76 V), zinc-ion batteries (ZIBs) have become a popular candidate for the next-generation energy storage technology.

[0004] A major problem with ZIBs is the development of cathode materials with high discharge capacity and long cycle life. In recent years, researchers have developed many new cathode materials for ZIBs, mainly including manganese-based compounds, vanadium-based compounds, Prussian blue analogs and organic compounds. Among them, vanadium-based compounds have attracted increasing attention due to their advantages such as multi-electron redox reactions, multidimensional ion diffusion pathways and high specific capacity. However, conventionally synthesized vanadium-based compounds have poor performance in rate characteristics, cycle stability and other aspects due to their slow electrochemical reaction kinetics and structural collapse problems. Therefore, solving the problems of slow reaction kinetics and structural collapse of vanadium-based compounds is the key to achieving high-performance AZIBs.

[0005] In response to the problems of the above-mentioned vanadium-based positive electrode materials, many strategies have emerged, mainly focusing on coating materials, defect modulation and intercalation engineering, etc. These strategies are expected to alleviate the key problems of the above-mentioned vanadium-based materials. For example, CN110817958A - A carbon-coated nano-vanadium pentoxide lithium battery positive electrode material and its liquid phase in-situ preparation method, the method comprises the following steps: (1) dissolving hexadecyltrimethylammonium bromide in water and stirring; (2) adding triisopropoxide vanadium solution dropwise to the solution obtained in step (1) and stirring; (3) transferring the mixed solution obtained in step (2) into a reactor for hydrothermal reaction; (4) washing and drying the product obtained in step (3), and then performing low-temperature heat treatment. The method comprises mixing a hexadecyltrimethylammonium bromide solution with a vanadyl triisopropoxide solution, performing a hydrothermal reaction, and then washing, drying, and low-temperature heat treating the resulting product to obtain a carbon-coated nano-vanadium pentoxide lithium battery positive electrode material. The carbon-coated nano-vanadium pentoxide lithium battery positive electrode material has a high reversible charge and discharge specific capacity, a uniform carbon film coating, a carbon film that is not easily detached, and good electrochemical performance. CN115092960A discloses a defect-rich vanadium disulfide, a preparation method, and its application as a positive electrode material in aqueous zinc ion batteries. The method first involves preparing a defect-rich layered transition metal dichalcogenide VS2 powder material. The main preparation process includes a simple one-step hydrothermal method and subsequent in-situ electrochemical activation under high pressure. The obtained VS2 has a relatively unique structure and exhibits extremely high specific capacity and excellent rate performance when used as a positive electrode material for aqueous zinc ion batteries. Subsequently, a simple and convenient external weak magnetic field method is used to inhibit the growth of zinc dendrites, greatly improving the cycle life of the VS2 / Zn battery. The method has broad application prospects in the field of aqueous zinc ion batteries.

[0006] Although the above method can improve the electrochemical performance of cathode materials for aqueous zinc-ion batteries to a certain extent, it still has defects such as low exposure of electroactive sites and poor charge transfer kinetics. Summary of the Invention

[0007] In view of the above technical problems existing in the prior art, the object of the present invention is to provide a vanadium-based metal oxide@rGO composite aerogel and its preparation method and application.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] In the present invention, the "vanadium-based metal oxide@rGO composite aerogel" refers to: it includes reduced graphene oxide nanosheets and vanadium-based metal oxide nanoparticles dispersed on the reduced graphene oxide nanosheets.

[0010] In a first aspect, the present invention provides a method for preparing a vanadium-based metal oxide@rGO composite aerogel, the preparation method comprising the following steps:

[0011] (1) dissolving a vanadium-based oxide precursor in an organic solvent to obtain a vanadium-based oxide precursor solution, and subjecting the vanadium-based oxide precursor solution to a microwave reaction to obtain vanadium-based metal oxide nanoparticles;

[0012] The vanadium-based oxide precursor includes at least one of vanadium oxytriisopropoxide (VO(OiPr)3), vanadium oxytrichloride (VOCl3) and vanadium oxyoxalate (VO(C2O4));

[0013] The vanadium-based metal oxide nanoparticles are selected from V2O3, VO 1.52 (OH) 0.77 and VO2;

[0014] (2) dispersing the vanadium-based metal oxide nanoparticles in a dispersion of graphene oxide nanosheets to perform electrostatic self-assembly, freeze-drying, and then calcining under a protective atmosphere to obtain a vanadium-based metal oxide@rGO composite aerogel.

[0015] In the present invention, the vanadium-based metal oxide nanoparticles refer to particles with a diameter of less than 500 nm.

[0016] The method of the present invention selects a specific type of vanadium-based oxide precursor to be dissolved in an organic solvent, and uses a microwave reaction method to obtain vanadium-based metal oxide nanoparticles of a specific composition. The nanoscale particle size can fully expose the electroactive sites in the material, which is beneficial to the Zn 2+ The nanoparticles are then fixed to the surface of graphene oxide (GO) nanosheets through electrostatic self-assembly. After calcination, the GO is converted into reduced GO (rGO), enhancing the material's conductivity. The highly conductive rGO improves charge transfer kinetics, while the lamellar rGO also serves to immobilize the nanoparticles, inhibiting their aggregation during charge and discharge, thereby mitigating structural collapse.

[0017] By using the method of the present invention, vanadium triisopropoxide is used as a vanadium-based oxide precursor to form V2O3 nanoparticles, and vanadium trichloride is used as a vanadium-based oxide precursor to form VO 1.52 (OH) 0.77 Ammonium metavanadate and vanadyl oxalate can be used as precursors of vanadium-based oxides to form VO2.

[0018] In the method of the present invention, the organic solvent needs to meet the following conditions: it can dissolve the vanadium-based oxide precursor and does not participate in the synthesis reaction of the vanadium-based metal oxide nanoparticles during the microwave reaction.

[0019] The vanadium-based metal oxide@rGO composite aerogel prepared by the method of the present invention is used as the positive electrode of a zinc ion battery, has good cycle life, rate performance and high discharge specific capacity, and has good application potential.

[0020] The method of the present invention utilizes simple microwave synthesis, electrostatic self-assembly and calcination processes, has simple steps, is safe and reliable, does not cause harm or pollution to personnel or the environment, and is easy to promote and use.

[0021] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0022] Preferably, the organic solvent in step (1) comprises at least one of benzyl alcohol, ethylene glycol and diethylene glycol.

[0023] Preferably, the concentration of the vanadium-based oxide precursor in the vanadium-based oxide precursor solution in step (1) is 100 mmol / L to 200 mmol / L, for example, it can be 100 mmol / L, 120 mmol / L, 130 mmol / L, 150 mmol / L, 160 mmol / L, 170 mmol / L, 180 mmol / L, 190 mmol / L or 200 mmol / L, etc.

[0024] Preferably, the temperature of the microwave reaction in step (1) is 180°C to 220°C, for example, it can be 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C or 220°C.

[0025] Preferably, the microwave reaction in step (1) is carried out in the microwave reactor, which is provided with a microwave reaction tube for containing the reactants, and the microwave reactor is heated to a set temperature under a certain power.

[0026] Preferably, the power is 500W to 1200W, for example, 500W, 550W, 600W, 650W, 700W, 750W, 800W, 850W, 900W, 950W, 1000W, 1050W, 1100W, 1150W, or 1200W. If the power is too low, the precursor reaction will be insufficient; if the power is too high, the heating rate will be too fast, the reaction will be more intense, the nanoparticle size distribution will be larger, and some particles will agglomerate, affecting the material properties.

[0027] Preferably, the microwave reaction time in step (1) is 10 min to 30 min, for example, 10 min, 15 min, 20 min, 25 min or 30 min.

[0028] Preferably, the microwave reaction in step (1) is accompanied by stirring, and the stirring speed is 500 rpm to 700 rpm, for example, 500 rpm, 550 rpm, 600 rpm, 650 rpm or 700 rpm.

[0029] As a preferred technical solution of the preparation method of the present invention, in step (2), the mass ratio of the vanadium-based metal oxide nanoparticles to the graphene oxide nanosheets is 1:(0.1-0.5), for example, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4 or 1:0.5, etc.

[0030] Preferably, in step (2), the method of dispersing the vanadium-based metal oxide nanoparticles in the dispersion of graphene oxide nanosheets comprises:

[0031] First, the vanadium-based metal oxide nanoparticles are dispersed in an aqueous solution of a surfactant to obtain a first solution, and the dispersion of graphene oxide nanosheets is mixed with the first solution and stirred evenly.

[0032] Preferably, the surfactant includes 2-(2-(2-methoxyethoxy)ethoxy)acetic acid and sodium dodecylbenzenesulfonate.

[0033] Preferably, the concentration of the surfactant aqueous solution is 40 mL / L to 60 mL / L, for example, 40 mL / L, 45 mL / L, 50 mL / L, 55 mL / L, or 60 mL / L. The concentration refers to the volume of the surfactant contained in 1 L of aqueous solution. For example, if the concentration of the aqueous solution is 40 mL / L, it means that 1 L of aqueous solution contains 40 mL of surfactant.

[0034] Preferably, the dispersion method is ultrasonic dispersion.

[0035] Preferably, the concentration of the vanadium-based metal oxide nanoparticles in the first solution is 10 mg / mL to 20 mg / mL, for example, 10 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 18 mg / mL or 20 mg / mL.

[0036] Preferably, the gas in the protective atmosphere in step (2) includes at least one of nitrogen, helium, argon or neon.

[0037] Preferably, the calcination temperature in step (2) is 250°C to 300°C, for example, 250°C, 260°C, 270°C, 280°C, 290°C or 300°C.

[0038] Preferably, the calcination time in step (2) is 1 h to 3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h.

[0039] Preferably, the heating rate of the calcination in step (2) is 1°C / min to 5°C / min, for example, 1°C / min, 2°C / min, 3°C / min, 4°C / min or 5°C / min.

[0040] In a second aspect, the present invention provides a vanadium-based metal oxide @ rGO composite aerogel, wherein the vanadium-based metal oxide @ rGO composite aerogel is prepared by the preparation method described in the first aspect, wherein the vanadium-based metal oxide @ rGO composite aerogel comprises reduced graphene oxide nanosheets and vanadium-based metal oxide nanoparticles dispersed on the reduced graphene oxide nanosheets, wherein the vanadium-based metal oxide is selected from V2O3, VO 1.52 (OH) 0.77 , VO2 or at least one of them.

[0041] In a third aspect, the present invention provides a positive electrode, comprising the vanadium-based metal oxide@rGO composite aerogel described in the first aspect.

[0042] In a fourth aspect, the present invention provides an aqueous zinc ion battery, comprising the positive electrode described in the third aspect.

[0043] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The method of the present invention selects a specific type of vanadium-based oxide precursor to be dissolved in an organic solvent, and uses a microwave reaction method to obtain vanadium-based metal oxide nanoparticles of a specific composition. The nanoscale particle size can fully expose the electroactive sites in the material, which is beneficial to the Zn 2+The nanoparticles are then fixed to the surface of graphene oxide (GO) nanosheets through electrostatic self-assembly. After calcination, the GO is converted into reduced GO (rGO), enhancing the material's conductivity. The highly conductive rGO improves charge transfer kinetics, while the lamellar rGO also serves to immobilize the nanoparticles, inhibiting their aggregation during charge and discharge, thereby mitigating structural collapse.

[0046] (2) The vanadium-based metal oxide@rGO composite aerogel prepared by the method of the present invention is used as the positive electrode of zinc ion batteries, has good cycle life, rate performance and high discharge specific capacity, and has good application potential.

[0047] (3) The method of the present invention utilizes simple microwave synthesis, electrostatic self-assembly, and calcination processes, and has simple steps. Moreover, the reaction process is safe and reliable, does not cause harm or pollution to personnel or the environment, and is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the preparation process of vanadium-based metal oxide@rGO composite aerogel. DETAILED DESCRIPTION

[0049] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0050] The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0051] In the embodiment of the present invention, nanoparticles refer to particles with a diameter of less than 500 nm.

[0052] Example 1

[0053] This embodiment provides a method for preparing a vanadium-based metal oxide@rGO composite aerogel, comprising the following steps:

[0054] (1) Weigh 183.15 mg of vanadyl triisopropoxide and 5 ml of anhydrous benzyl alcohol, transfer them to a 10 ml microwave reaction tube, and stir until the solid powder is completely dissolved. Insert the microwave reaction tube into the cavity of a microwave reactor, and set the microwave reactor parameters as follows: heating power of 800 W, maximum temperature of 200°C, and heating time of 20 min. The product after the reaction is centrifuged to obtain a precipitate, which is then washed several times with ether to obtain V2O3 nanoparticles.

[0055] (2) V2O3 nanoparticles were dispersed in an aqueous solution containing the surfactant MEEAA (MEEAA concentration was 50 mL / L) to obtain a first solution, in which the concentration of V2O3 nanoparticles in the first solution was 15 mg / mL. Subsequently, a graphene oxide (GO) nanosheet dispersion (GO concentration was 5 mg / mL) was added, and the mass ratio of V2O3 nanoparticles to GO nanosheets was controlled to be 1:0.2. After stirring evenly, the mixture was freeze-dried to obtain a V2O3@GO composite aerogel.

[0056] (3) V2O3@GO was placed in a tubular furnace and calcined at 300°C in a N2 atmosphere for 2 h. Graphene oxide was reduced and converted into reduced graphene oxide rGO, and finally V2O3@rGO composite aerogel was obtained.

[0057] Example 2

[0058] This embodiment provides a method for preparing a vanadium-based metal oxide@rGO composite aerogel, comprising the following steps:

[0059] (1) Weigh 129.98 mg of vanadium oxytrichloride and 5 ml of anhydrous benzyl alcohol and transfer them to a 10 ml microwave reaction tube and stir until the solid powder is completely dissolved. Insert the microwave reaction tube into the cavity of the microwave reactor and set the parameters of the microwave reactor as follows: heating power of 600 W, maximum temperature of 200 ° C, and heating time of 20 min. The product after the reaction is centrifuged to obtain the precipitate, and washed with ether several times to obtain VO 1.52 (OH) 0.77 Nanoparticles.

[0060] (2) VO 1.52 (OH) 0.77 The nanoparticles are dispersed in an aqueous solution containing a surfactant MEEAA (MEEAA concentration is 50 mL / L) to obtain a first solution, wherein the VO 1.52 (OH) 0.77 The concentration of nanoparticles was 15 mg / mL, and then graphene oxide (GO) nanosheet dispersion (GO concentration was 5 mg / mL) was added to control VO 1.52 (OH) 0.77 The mass ratio of nanoparticles to GO nanosheets was 1:0.2. After stirring evenly, VO was freeze-dried to obtain 1.52 (OH) 0.77 @GO composite aerogel.

[0061] (3) VO 1.52 (OH) 0.77 @GO was placed in a tube furnace and calcined at 300℃ in N2 atmosphere for 2h to obtain VO 1.52 (OH)0.77 @rGO composite aerogel.

[0062] Example 3

[0063] This embodiment provides a method for preparing a vanadium-based metal oxide@rGO composite aerogel, comprising the following steps:

[0064] (1) Weigh 150.20 mg of vanadyl triisopropoxide and 5 ml of anhydrous benzyl alcohol, transfer them to a 10 ml microwave reaction tube, and stir until the solid powder is completely dissolved. Insert the microwave reaction tube into the cavity of a microwave reactor, and set the microwave reactor parameters as follows: heating power of 1000 W, maximum temperature of 180°C, and heating time of 30 min. The product after the reaction is centrifuged to obtain a precipitate, which is then washed several times with ether to obtain V2O3 nanoparticles.

[0065] (2) V2O3 nanoparticles were dispersed in an aqueous solution containing the surfactant MEEAA (MEEAA concentration was 60 mL / L) to obtain a first solution, in which the concentration of V2O3 nanoparticles in the first solution was 20 mg / mL. Subsequently, a graphene oxide (GO) nanosheet dispersion (GO concentration was 7 mg / mL) was added, and the mass ratio of V2O3 nanoparticles to GO nanosheets was controlled to be 1:0.1. After stirring evenly, the mixture was freeze-dried to obtain a V2O3@GO composite aerogel.

[0066] (3) V2O3@GO was placed in a tubular furnace and calcined at 250°C in a N2 atmosphere for 3 h. Graphene oxide was reduced and converted into reduced graphene oxide rGO, and finally V2O3@rGO composite aerogel was obtained.

[0067] Example 4

[0068] This embodiment provides a method for preparing a vanadium-based metal oxide@rGO composite aerogel, comprising the following steps:

[0069] (1) Weigh 170.55 mg of vanadium trichloride 173.3 and 5 ml of anhydrous benzyl alcohol and transfer them to a 10 ml microwave reaction tube and stir until the solid powder is completely dissolved. Insert the microwave reaction tube into the cavity of the microwave reactor and set the parameters of the microwave reactor as follows: heating power 800 W, maximum temperature 220 ° C, heating time 10 min. The product after the reaction is centrifuged to obtain the precipitate, and washed with ether several times to obtain VO 1.52 (OH) 0.77 Nanoparticles.

[0070] (2) VO 1.52 (OH) 0.77The nanoparticles were dispersed in an aqueous solution containing a surfactant MEEAA (MEEAA concentration of 40 mL / L) to obtain a first solution in which the concentration of V2O3 nanoparticles was 10 mg / mL. Subsequently, a dispersion of graphene oxide (GO) nanosheets (GO concentration of 5 mg / mL) was added to control the VO 1.52 (OH) 0.77 The mass ratio of nanoparticles to GO nanosheets was 1:0.5, and the mixture was stirred evenly and freeze-dried to obtain VO 1.52 (OH) 0.77 @GO composite aerogel.

[0071] (3) VO 1.52 (OH) 0.77 @GO was placed in a tube furnace and calcined at 275℃ in N2 atmosphere for 1.5h to obtain VO 1.52 (OH) 0.77 @rGO composite aerogel.

[0072] Example 5

[0073] The difference between this embodiment and embodiment 1 is that in step (1), the maximum temperature and heating time of microwave heating are the same, and the heating power is changed to 200W.

[0074] Example 6

[0075] The difference between this embodiment and embodiment 1 is that in step (1), the maximum temperature and heating time of microwave heating are the same, and the heating power is changed to 1500W.

[0076] Example 7

[0077] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of V2O3 nanoparticles to GO nanosheets is controlled to be 1:0.03.

[0078] Example 8

[0079] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of V2O3 nanoparticles to GO nanosheets is controlled to be 1:0.6.

[0080] Comparative Example 1

[0081] The difference between this comparative example and Example 1 is that triisopropoxyvanadium is replaced by ammonium vanadate, anhydrous benzyl alcohol is replaced by deionized water, and the amount of vanadium element is controlled to be the same as that in Example 1.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 1 is that step (2) and step (3) are not performed, and the product is VO 1.52(OH) 0.77 Nanoparticles, without reduced graphene oxide.

[0084] Preparation of zinc ion battery:

[0085] (1) Preparation of positive electrode sheets: The products of each embodiment and comparative example were used as positive electrode materials. The positive electrode materials, conductive carbon black, and polyvinylidene fluoride were dispersed in an appropriate amount of N-methylpyrrolidone at a mass ratio of 7:2:1. The mixture was stirred evenly to form a slurry of appropriate consistency, which was then coated on a commercial titanium foil. The positive electrode sheets were obtained after drying at 80°C under vacuum. The loading amount of the positive electrode material was 1±0.1 mg / cm 2 ;

[0086] (2) Preparation of negative electrode sheet: Commercial zinc foil was sanded with sandpaper to remove the surface oxide layer, wiped clean with alcohol, and then punched into a circular sheet to obtain the negative electrode sheet;

[0087] (3) Preparation of electrolyte: Using zinc sulfate heptahydrate as the solute and deionized water as the solvent, a 2 mol / L zinc sulfate solution was prepared as the zinc ion battery electrolyte;

[0088] (4) Assemble the battery cell and inject the electrolyte in the order of negative electrode shell-negative electrode sheet-diaphragm-positive electrode sheet-gasket-spring-positive electrode shell to obtain a zinc ion battery. The amount of electrolyte used is 150 mL, the battery shell model is CR2032, and the separator model is glass fiber separator (GF / D).

[0089] Performance testing:

[0090] (1) Discharge capacity test: After the battery is activated, it is discharged at a constant current of 1 A / g in the voltage range of 0.3-1.4 V to obtain the discharge capacity.

[0091] (2) Rate performance test: In the voltage range of 0.3-1.4 V, constant current discharge is performed at a current of 10 A / g to obtain a discharge capacity of 10 A / g. The ratio of this capacity to the discharge capacity of 1 A / g is the rate performance.

[0092] (3) Cycling performance test: At a voltage range of 0.3 to 1.4 V, constant current charge and discharge cycles were performed at a current of 1 A / g for 500 cycles. The ratio of the discharge capacity after 500 cycles to the discharge capacity after the first cycle was the cycle capacity retention rate. The higher the cycle capacity retention rate, the better the cycling performance.

[0093] See Table 1 for the results.

[0094] Table 1

[0095]

[0096] In summary, the method of the present invention selects a specific type of vanadium-based oxide precursor to be dissolved in an organic solvent, and a microwave reaction method is used to obtain vanadium-based metal oxide nanoparticles of a specific composition. Furthermore, the nanoparticles are fixed on the surface of graphene oxide (GO) nanosheets by electrostatic self-assembly, and calcined to obtain vanadium-based metal oxide @ rGO composite aerogel. The vanadium-based metal oxide @ rGO composite aerogel can effectively improve the discharge capacity, rate performance and cycle performance of the material. The capacity retention rate is above 189.4 mAh / g, preferably above 261.5 mAh / g; the rate performance is above 44.2%, preferably above 57.8%; the capacity retention rate after 500 cycles is above 71.2%, preferably above 88.4%.

[0097] By comparing Example 1 with Examples 5-6, it can be seen that when the microwave power is low, the reaction is incomplete, and part of the precursor is converted into nanoparticles, resulting in insufficient capacity. When the microwave power is too high, the reaction is complete and the capacity of the nanoparticles is higher. However, the high power causes a more violent reaction, and part of the nanoparticles aggregate, resulting in a rate performance lower than that of Example 1.

[0098] By comparing Example 1 with Examples 7-8, it can be seen that when the graphene load is small, the nanoparticles are unevenly dispersed in the slurry and partially agglomerated, which affects the discharge capacity, and the rate performance deteriorates more and the cycle performance also decreases; when the load is large, the performance is affected by the process and yield, and all performances are reduced.

[0099] By comparing Example 1 with Comparative Example 1, it can be seen that in the absence of benzyl alcohol solvent and the precursor used is not a vanadium-based oxide, the precursor cannot be converted into nanoparticles, and large particles larger than 1 micron are formed. The performance is significantly different from that of nanoparticles, and the product fails before 500 cycles.

[0100] By comparing Example 1 with Comparative Example 2, it can be seen that when the nanoparticles are not loaded on rGO, they are easily agglomerated, resulting in degradation of the discharge capacity, rate performance and cycle performance.

[0101] The applicant states that the present invention is intended to illustrate the detailed methods of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed methods, that is, it does not mean that the present invention must rely on the above-described detailed methods in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for various raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a vanadium-based metal oxide @rGO composite aerogel, characterized in that: The preparation method comprises the following steps: (1) dissolving a vanadium-based oxide precursor in an organic solvent to obtain a vanadium-based oxide precursor solution, and subjecting the vanadium-based oxide precursor solution to a microwave reaction to obtain vanadium-based metal oxide nanoparticles; The vanadium-based oxide precursor includes at least one of vanadium oxytriisopropoxide, vanadium oxytrichloride and vanadium oxyoxalate; The vanadium-based metal oxide nanoparticles are selected from V2O3, VO 1.52 (OH) 0.77 and VO2; (2) dispersing the vanadium-based metal oxide nanoparticles in a dispersion of graphene oxide nanosheets to perform electrostatic self-assembly, freeze-drying, and then calcining under a protective atmosphere to obtain a vanadium-based metal oxide@rGO composite aerogel.

2. The preparation method according to claim 1, characterized in that The organic solvent in step (1) comprises at least one of benzyl alcohol, ethylene glycol and diethylene glycol; Preferably, the concentration of the vanadium-based oxide precursor in the vanadium-based oxide precursor solution in step (1) is 100 mmol / L to 200 mmol / L.

3. The preparation method according to claim 1 or 2, characterized in that The temperature of the microwave reaction in step (1) is 180° C. to 220° C.; Preferably, the microwave reaction in step (1) is carried out in the microwave reactor, wherein the microwave reactor is provided with a microwave reaction tube, wherein the microwave reaction tube is used to hold the reactant, and the microwave reactor is raised to a set temperature under a certain power; Preferably, the power is 500W to 1200W; Preferably, the microwave reaction time in step (1) is 10 min to 30 min; Preferably, the microwave reaction in step (1) is accompanied by stirring, and the stirring speed is 500 rpm to 700 rpm.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (2), the mass ratio of the vanadium-based metal oxide nanoparticles to the graphene oxide nanosheets is 1:(0.1-0.5).

5. The preparation method according to any one of claims 1 to 4, characterized in that In step (2), the method of dispersing the vanadium-based metal oxide nanoparticles in the dispersion of graphene oxide nanosheets includes: First, the vanadium-based metal oxide nanoparticles are dispersed in an aqueous solution of a surfactant to obtain a first solution, and the dispersion of graphene oxide nanosheets is mixed with the first solution and stirred evenly.

6. The preparation method according to claim 5, characterized in that The surfactant includes 2-(2-(2-methoxyethoxy)ethoxy)acetic acid and sodium dodecylbenzenesulfonate; Preferably, the concentration of the aqueous solution of the surfactant is 40 mL / L to 60 mL / L; Preferably, the dispersion method is ultrasonic dispersion; Preferably, the concentration of the vanadium-based metal oxide nanoparticles in the first solution is 10 mg / mL to 20 mg / mL.

7. The preparation method according to any one of claims 1 to 6, characterized in that The gas in the protective atmosphere of step (2) includes at least one of nitrogen, helium, argon or neon; Preferably, the calcination temperature in step (2) is 250° C. to 300° C.; Preferably, the calcination time in step (2) is 1 h to 3 h; Preferably, the heating rate of the calcination in step (2) is 1°C / min to 5°C / min.

8. A vanadium-based metal oxide@rGO composite aerogel, characterized in that: The vanadium-based metal oxide @ rGO composite aerogel is prepared by the preparation method according to any one of claims 1 to 7, wherein the vanadium-based metal oxide @ rGO composite aerogel comprises reduced graphene oxide nanosheets and vanadium-based metal oxide nanoparticles dispersed on the reduced graphene oxide nanosheets, wherein the vanadium-based metal oxide is selected from V2O3, VO 1.52 (OH) 0.77 , VO2 or at least one of them.

9. A positive electrode, characterized in that The positive electrode includes the vanadium-based metal oxide@rGO composite aerogel according to claim 8.

10. An aqueous zinc ion battery, characterized in that: The aqueous zinc ion battery comprises the positive electrode according to claim 9.

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