Vanadium oxide material for aqueous zinc ion battery

Abstract

The invention discloses a vanadium oxide material for an aqueous zinc ion battery. The material is constructed by self-assembling small organic molecules on the surface of vanadium oxide at room temperature under the dual action of hydrogen bonds and hydrophilic functional groups. When the material is used as a positive electrode material, on one hand, small molecules are tightly adsorbed on the outer layer of the vanadium-based material through hydrogen bond acting force to inhibit dissolution and structure collapse of the vanadium-based material; on the other hand, the tail ends of the small organic molecules can adsorb water molecules, so that structure collapse caused by excessive water molecules rushing into the interlayer of the vanadium-based positive electrode material is prevented. In the electrochemical reaction period, the small molecular coating vanadium-based material shows high capacity and good cycling stability. The battery installed by the positive electrode material can stably circulate for 275 circles under the current density of 0.5 A g <-1 >, and the capacity can be kept at 270 mAh g <-1 >.

Description

Technical Field

[0001] The present invention belongs to the technical field of aqueous zinc-ion batteries, and particularly relates to a small molecule-coated vanadium oxide material for aqueous zinc-ion batteries. Background Art

[0002] Developing new green and renewable energy storage systems is a necessary prerequisite for solving the non-renewable energy crisis and ensuring the sustainable development of human society. Currently, the large-scale electrochemical energy storage mainly relies on lithium batteries and lead-acid batteries. However, due to the high risk and cost of lithium batteries, and the poor cycle stability, incomplete charge and discharge of lead-acid batteries, developing new batteries with high stability, low cost, and green pollution-free remains the research focus.

[0003] Aqueous zinc-ion batteries (ZIBs) are expected to be a solution for future large-scale energy storage due to their inherent safety, low cost, and ecological friendliness. In a typical ZIBs energy storage system, metallic zinc is used as the anode, the main material for storing zinc ions is used as the cathode, and an aqueous zinc salt solution is used as the electrolyte. So far, a series of cathode materials have been studied, including vanadium-based compounds, manganese-based compounds, Prussian blue analogs, and organic compounds. Among them, vanadium-based compounds have a flexible crystal structure and a high theoretical capacity, and have become ideal cathode candidate materials for high-performance aqueous ZIBs. However, exploring suitable cathode materials for aqueous zinc-ion batteries still faces many challenges, such as severe material dissolution and structural instability of the cathode materials. These problems may lead to rapid capacity decay, low cycle life, and serious battery failure. So far, a series of modification methods for vanadium-based cathode materials have been studied, and the current research methods mainly focus on pre-intercalation of vanadium-based materials, defect engineering, nanostructure modification, etc. Liang et al. prepared a polyaniline-coated polyoxovanadate cathode by in-situ polymerization, showing a high reversible specific capacity of 456.8 mAh g -1 (Chemical Engineering Journal 495(2024)153255), and Sun et al. coated 3,4-ethylenedioxythiophene (PEDOT) on the surface of hydrated vanadium pentoxide (Inorg. Chem. Front., 2023, 10, 4266–4275). However, in previous work, the capacity retention rate at low current density and the battery stability under long cycle numbers have not been well improved.

[0004] Through the retrieval of existing patent literature, it is found that CN 116914118 A discloses a cathode material for aqueous zinc-ion batteries, including phosphorus-containing hydroxy compound-modified V 2 O 5 , and the phosphorus-containing hydroxy compound includes one or more of hydroxymethylphenylphosphinic acid, hydroxyethylidene diphosphonic acid, and phosphoric acid; during preparation, V2 O 5 After mixing with hydrogen peroxide solution, a phosphorus-containing hydroxy compound solution is added for hydrothermal reaction to obtain the product. This solution solves the problem of poor cycling performance of aqueous zinc-ion batteries to a certain extent. However, its mechanism of action is mainly through the use of phosphorus-containing hydroxy compounds as interlayer pillars to stabilize the V 2 O 5 interlayer structure; and there are problems such as cumbersome preparation process and too high synthesis temperature (140 - 160 °C).

[0005] CN 119059557 A discloses a vanadium-based oxide@C composite material, its preparation method and application; it uses the reaction of vanadium-based materials and organic molecular monomers (linear or branched C1-C18 alkylamines and their derivatives) to generate a precursor, and then the precursor is subjected to a polymerization reaction in an oxygen atmosphere, a high-temperature carbonization reaction in an inert atmosphere or a reducing atmosphere, or directly the precursor is subjected to a high-temperature carbonization reaction in an inert atmosphere or a reducing atmosphere to obtain a vanadium-based oxide@C composite material. And by regulating different vanadium-based materials and organic molecular monomers, composite materials with different morphological structures and carbon contents can be constructed, solving the problem of poor conductivity of vanadium-based oxides and improving their performance in energy storage. The mechanism of action of this solution is mainly to improve the conductivity of the material through carbonization treatment (300 °C - 1200 °C). There are also problems such as too high preparation temperature. SUMMARY OF THE INVENTION

[0006] Based on the deficiencies of the above-mentioned existing technologies, how to enhance the material stability of vanadium-based cathode materials during the cycling process is a key step in improving the comprehensive performance of vanadium-based cathode materials; the present invention proposes a small molecule-coated vanadium oxide for aqueous zinc-ion batteries, providing a choice for the design of battery electrode materials. The small molecule-coated vanadium oxide refers to establishing an organic small molecule coating on the surface of vanadium oxide, and the small molecule-coated vanadium oxide is used as the active material of the positive electrode material for aqueous zinc-ion batteries. Through the dual action of hydrogen bonds and hydrophilic functional groups, this material can effectively prevent the dissolution and structural collapse of vanadium-based materials, enhance structural stability, and improve the performance of the positive electrode material for aqueous zinc-ion batteries from two aspects: preventing the dissolution of vanadium oxide and stabilizing the material structure, thereby significantly improving the cycling stability of aqueous zinc-ion batteries. Currently, in aqueous zinc-ion batteries, there is no introduction of this kind of small molecule-coated vanadium oxide.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] The present invention relates to a small molecule-coated vanadium oxide for aqueous zinc ion batteries. The small molecule-coated vanadium oxide is constructed by self-assembly of organic small molecules on the surface of vanadium oxide at 10-40 °C through the dual action of hydrogen bonds and hydrophilic functional groups. The small molecules with hydrophilic functional groups are adsorbed on the outer layer of vanadium oxide through hydrogen bond forces, and the organic small molecules can be self-assembled on the surface of vanadium oxide at 10-40 °C (such as room temperature).

[0009] As an embodiment of the present invention, the organic small molecules form a coating on vanadium oxide by an impregnation method. The reaction conditions are 10-40 °C. The organic small molecule functional groups are hydrophilic and can form hydrogen bonds with the oxygen atoms of vanadium oxide during the impregnation process. The vanadium oxide retains its original lamellar microstructure. The small particles of vanadium oxide stacked by lamellar nanolayers become smooth on the surface under the coating effect of the organic small molecules.

[0010] As an embodiment of the present invention, the organic small molecules form a coating on vanadium oxide by an impregnation method. The impregnation time is 8-12 h; after the impregnation is completed, it is taken out, washed and dried to obtain the small molecule-coated vanadium oxide for aqueous zinc ion batteries. Further, the drying is carried out at 70-90 °C for 8-12 h. The washing can be centrifugal washing with water and ethanol respectively for multiple times, such as three or four times.

[0011] As an embodiment of the present invention, the small molecule coating is formed by stacking nanoscale particles.

[0012] As an embodiment of the present invention, the organic small molecules contain phosphate groups and some of their functional groups are hydrophilic functional groups; the hydrophilic functional groups include any one of functional groups such as alkyl, hydroxyl, and amino groups. After the organic small molecules are coated on the surface of vanadium oxide. On the one hand, the hydrogen bonds connecting the organic small molecules and vanadium oxide can effectively isolate the direct contact between vanadium oxide and the aqueous electrolyte, well protecting the vanadium oxide and inhibiting the dissolution of the cathode material. On the other hand, the hydrophilic functional groups of the organic small molecules can well adsorb water molecules, preventing excessive water molecules from entering the interlayer and causing the structural collapse of vanadium oxide.

[0013] As an embodiment of the present invention, the organic small molecule is at least one of 3-aminopropylphosphonic acid, 2-aminoethylphosphonic acid, and diethyl phosphonate. Taking 3-aminopropylphosphonic acid as an example, from the perspective of hydrogen bond interaction: 3-aminopropylphosphonic acid (AEPA) has an amino group and a phosphoric acid group, and can form a strong adsorption with the surface of vanadium oxide (such as V2O5) through hydrogen bonds in the system of the present invention. This hydrogen bond force can not only effectively prevent the dissolution of vanadium oxide, but also adsorb water molecules through hydrophilic functional groups to prevent excessive water molecules from entering the interlayer of vanadium oxide, thereby enhancing the structural stability of the material. For example, when using phosphorus-containing hydroxy compounds (such as hydroxymethylphenylphosphinic acid, hydroxyethylidene diphosphonic acid, or phosphoric acid), although they also contain hydroxy and phosphoric acid groups, their molecular structures do not have the ability to form strong enough hydrogen bonds with the surface of vanadium oxide, especially in preventing water molecules from entering the interlayer, which is not as effective as 3-aminopropylphosphonic acid. Further, from the perspective of hydrophilicity and water molecule adsorption capacity, 3-aminopropylphosphonic acid has an amino group and a phosphoric acid group, and can adsorb water molecules in the aqueous electrolyte through hydrophilic functional groups to prevent water molecules from entering the interlayer of vanadium oxide, thereby avoiding structural collapse. For example, when using phosphorus-containing hydroxy compounds (such as hydroxymethylphenylphosphinic acid, hydroxyethylidene diphosphonic acid, or phosphoric acid), although they have a certain hydrophilicity, their molecular structures may not be able to effectively adsorb water molecules like 3-aminopropylphosphonic acid, especially in the problem of water molecules entering the interlayer, they may not provide sufficient protection. And when using linear or branched C1-C18 alkylamines and their derivatives (such as aniline), which mainly contain amino groups or alkyl groups, although the amino group can form hydrogen bonds with the surface of vanadium oxide, their molecular structures lack phosphoric acid groups and cannot further enhance the binding force with vanadium oxide like 3-aminopropylphosphonic acid, nor can they effectively adsorb water molecules. It can be seen that neither phosphorus-containing hydroxy compounds nor linear or branched C1-C18 alkylamines and their derivatives can effectively prevent the dissolution and structural collapse of vanadium oxide through the dual action of hydrogen bonds and hydrophilic functional groups, and thus cannot significantly improve the cycle stability of aqueous zinc-ion batteries.

[0014] In some embodiments, the construction includes the following steps: the hydrophilic organic small molecule is dissolved in any one of absolute ethanol, methanol, isopropanol, etc. to form a solvent, and the solute vanadium oxide is impregnated in the solvent. In an environment of 10-40 °C (such as room temperature), without a catalyst, the organic small molecule forms hydrogen bonds with the vanadium oxide, enabling the organic small molecule to be successfully established on the surface layer of the vanadium oxide, and regulating the morphology of the vanadium oxide to make it into smooth-surfaced nanoscale particles.

[0015] As an embodiment of the present invention, the selected vanadium oxide of the present invention has strong redox properties and relatively rich valence states, such as, V 2 O 3 、VO 2 、V2 O 5 etc. Among them, preferably V 2 O 5 。

[0016] As an embodiment of the present invention, the mass ratio of the organic small molecule to the vanadium oxide is 10:0.5 to 5.

[0017] As an embodiment of the present invention, during the self-assembly reaction process, mechanical stirring can be used to accelerate the reaction. The reaction stirring speed is 400 - 600 r / min, and the reaction time is 10 h - 15 h. If the time is too short or the stirring speed is too slow, it is not conducive to constructing the organic small molecule coating. If the time is too long, the reaction cost will increase.

[0018] As an embodiment of the present invention, the small molecule-coated vanadium oxide is used as the active material of the positive electrode of the aqueous zinc ion battery. When used as the positive electrode material, on the one hand, the small molecule is tightly adsorbed on the outer layer of the vanadium-based material through hydrogen bond force, inhibiting the dissolution and structural collapse of the vanadium-based material; on the other hand, the end of the organic small molecule can adsorb water molecules, preventing too many water molecules from flooding into the interlayer of the vanadium-based positive electrode material and causing structural collapse.

[0019] The present invention also provides a positive electrode material for an aqueous zinc ion battery, which contains the aforementioned small molecule-coated vanadium oxide.

[0020] As an embodiment of the present invention, the positive electrode material of the aqueous zinc ion battery is composed of an organic small molecule-coated vanadium oxide active material, a carbonaceous conductive agent, and a binder. Among them, the organic small molecule-coated vanadium oxide active material is 0.7 - 0.9 parts, the carbonaceous conductive agent is 0.05 - 0.2 parts, and the binder (such as PVDF) is 0.01 - 0.1 parts.

[0021] As an embodiment of the present invention, the separator of the aqueous zinc ion battery includes at least one of glass fiber, nanofibrillated cellulose separator, polypropylene (PP) separator, and polyethylene oxide (PEO) separator. The separator can block the direct contact between the positive and negative electrodes to prevent short circuit, and at the same time can also transfer zinc ions between the positive and negative electrodes through the electrolyte.

[0022] As an embodiment of the present invention, the electrolyte of the aqueous zinc ion battery includes at least one of zinc trifluoromethanesulfonate, zinc chloride, zinc nitrate, zinc trifluoromethanesulfonate, and zinc hexafluoride electrolyte. The electrolyte provides a part of the zinc ions during the charge and discharge process and can also be used as a medium for zinc ion transmission. The neutral aqueous electrolyte is green, environmentally friendly, and safe.

[0023] As an embodiment of the present invention, the carbonaceous conductive agent for the positive electrode material includes one or more combinations or mixed carbon materials such as carbon nanotubes, carbon fibers, graphene, graphene oxide, acetylene black, carbon black, etc. The carbonaceous conductive agent can accelerate the interfacial electron conduction of the positive electrode active material, reduce the overall contact resistance in the electrode, and reduce polarization.

[0024] As an embodiment of the present invention, the binder includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylic acid, polyaniline, and polypyrrole

[0025] As an embodiment of the present invention, the small molecule-coated vanadium oxide is used in an aqueous zinc-ion battery, with an open-circuit voltage of 1.4 - 1.5 V and a standing time of 4.5 - 6.5 h.

[0026] As an embodiment of the present invention, the small molecule-coated vanadium oxide is used in an aqueous zinc-ion battery. During the electrochemical reaction, the small molecule-coated vanadium-based material exhibits high capacity and good cycle stability. It can be cycled 275 times at a current density of 0.5 A g-1 without attenuation of the specific capacity.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) The preparation method of the present invention is simple, convenient, and low-cost, suitable for large-scale preparation of materials, and helps to promote the industrial development of aqueous zinc-ion batteries.

[0029] 1) The small molecule-coated vanadium oxide prepared by the present invention is modified on the basis of traditional lamellar vanadium oxide (vanadium pentoxide). The small molecules are firmly attached to vanadium pentoxide through chemical bonds. This coating significantly inhibits vanadium dissolution by avoiding direct contact between the electrolyte and the positive electrode.

[0030] 2) The present invention coats organic small molecules on the outer layer of vanadium oxide. The hydrophilic functional groups adsorb water molecules in the aqueous electrolyte to prevent water molecules from entering the interlayer of vanadium oxide; due to the hydrophilicity of the small molecules, the desolvation energy barrier of hydrated zinc ions can be greatly reduced, facilitating the interlayer diffusion of zinc ions.

[0031] 3) The small molecule-coated vanadium oxide produced for the positive electrode of an aqueous zinc-ion battery exhibits extremely excellent cycle stability and is expected to be widely used in the positive electrode materials and energy fields of aqueous zinc-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objectives, and advantages of the present invention will become more apparent:

[0033] Figure 1SEM image of small molecule coated vanadium oxide for aqueous zinc ion battery in Example 1;

[0034] Figure 2 TEM image of small molecule coated vanadium oxide for aqueous zinc ion battery in Example 1;

[0035] Figure 3 Raman spectrum of small molecule coated vanadium oxide for aqueous zinc ion battery in Example 1;

[0036] Figure 4 Infrared spectrum of small molecule coated vanadium oxide for aqueous zinc ion battery in Example 1;

[0037] Figure 5 Long cycle performance of small molecule coated vanadium oxide for aqueous zinc ion battery in Example 1;

[0038] Figure 6 Hydrophilicity calculation of small molecule coated vanadium oxide for aqueous zinc ion battery in Example 1;

[0039] Figure 7 Dissolution resistance test of small molecule coated vanadium oxide for aqueous zinc ion battery in Example 1. Detailed Description of the Invention

[0040] The present invention will be described in detail below with reference to the embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0041] Example 1

[0042] Using 3-aminopropylphosphonic acid (AEPA) and vanadium pentoxide with a molar ratio of 2:10 as the raw materials of the positive electrode active material, small molecule coated vanadium oxide for aqueous zinc ion battery with an organic small molecule coating was prepared by a simple room temperature impregnation method. It was centrifugally washed three times with water and ethanol respectively, and then dried in a vacuum oven at 80 °C for 12 h. Using the active material, conductive carbon black, and polyvinylidene fluoride (PVDF) binder with a mass ratio of 7:2:1 as the positive electrode material (Φ = 14 mm, active material ≈ 2.5 mg), an aqueous zinc ion battery was prepared and assembled with a 3M zinc trifluoromethanesulfonate electrolyte, a glass fiber separator, and a 0.03 mm thick zinc foil (Φ = 14 mm). As Figure 1 shown, the SEM scanning image of the layered strip-like vanadium oxide. The surface of the material is in a uniform and smooth state. As Figure 2 shown, a nanometer-thick uniform organic small molecule coating can be observed on the surface of the material. As Figure 3 and Figure 4As shown, the presence of P-O bonds in the Raman and infrared spectra proves the successful coating of small molecules. For the aqueous zinc-ion battery prepared with the small molecule-coated vanadium oxide as the positive electrode active material, at a current density of 0.5 A g -1 it can stably cycle nearly 300 times. Compared with vanadium pentoxide, its capacity can be maintained at 270 mAh g -1 , and there is no obvious attenuation in capacity, as Figure 5 shown. Small molecules have strong hydrophilicity, which inhibits the structural instability caused by water molecules entering the interlayer and also reconstructs the surface electron microenvironment of the positive electrode. The Zn 2+ solvation structure changes, as Figure 6 shown. This coating significantly inhibits vanadium dissolution by avoiding direct contact between the electrolyte and the positive electrode, as Figure 7 shown.

[0043] Example 2

[0044] Using 3-aminopropylphosphonic acid (AEPA) and vanadium pentoxide with a molar ratio of 1:10 as the raw materials for the positive electrode active material, a small molecule-coated vanadium oxide for aqueous zinc-ion batteries with an organic small molecule coating is prepared by a simple room-temperature impregnation method. Similarly, using the active material, conductive carbon black, and polyvinylidene fluoride (PVDF) binder with a mass ratio of 7:2:1 as the positive electrode material (Φ = 14 mm, active material ≈ 2.5 mg), an aqueous zinc-ion battery is prepared and assembled with 3M zinc trifluoromethanesulfonate electrolyte, glass fiber separator, and a 0.03-mm-thick zinc foil. For the aqueous zinc-ion battery prepared with the small molecule-coated vanadium oxide as the positive electrode active material, at a current density of 0.5 A g -1 it can stably cycle 200 times, and there is no obvious attenuation in its capacity compared with vanadium pentoxide.

[0045] Example 3

[0046] Using 3-aminopropylphosphonic acid (AEPA) and vanadium pentoxide with a molar ratio of 0.5:10 as the raw materials for the positive electrode active material, a small molecule-coated vanadium oxide for aqueous zinc-ion batteries with an organic small molecule coating is prepared by a simple room-temperature impregnation method. Using the active material, conductive carbon black, and polyvinylidene fluoride (PVDF) binder with a mass ratio of 7:2:1 as the positive electrode material (Φ = 14 mm, active material ≈ 2.5 mg), an aqueous zinc-ion battery is prepared and assembled with 3M zinc trifluoromethanesulfonate electrolyte, glass fiber separator, and a 0.03-mm-thick zinc foil. For the aqueous zinc-ion battery prepared with the small molecule-coated vanadium oxide as the positive electrode active material, at a current density of 0.5 A g -1 it can stably cycle 220 times, and its capacity remains relatively stable compared with vanadium pentoxide.

[0047] Example 4

[0048] Using 3-aminopropylphosphonic acid (AEPA) and vanadium pentoxide with a molar ratio of 3:10 as the raw materials for the cathode active material, a small molecule-coated vanadium oxide for aqueous zinc-ion batteries with an organic small molecule coating was prepared by a simple room-temperature impregnation method. Using an active material, conductive carbon black, and polyvinylidene fluoride (PVDF) binder with a mass ratio of 7:2:1 as the cathode material (Φ = 14 mm, active material ≈ 2.5 mg), an aqueous zinc-ion battery was prepared and assembled using a 3M zinc trifluoromethanesulfonate electrolyte, a glass fiber separator, and a 0.03 mm thick zinc foil. The aqueous zinc-ion battery prepared with the small molecule-coated vanadium oxide as the cathode active material can be stably cycled 200 times at a current density of 0.5 A g -1 and its capacity retention is relatively stable compared with vanadium pentoxide.

[0049] Example 5

[0050] Using 2-aminoethylphosphonic acid and vanadium pentoxide with a molar ratio of 2:10 as the raw materials for the cathode active material, a small molecule-coated vanadium oxide for aqueous zinc-ion batteries with an organic small molecule coating was prepared by a simple room-temperature impregnation method. Using an active material, conductive carbon black, and polyvinylidene fluoride (PVDF) binder with a mass ratio of 7:2:1 as the cathode material (Φ = 14 mm, active material ≈ 2.5 mg), an aqueous zinc-ion battery was prepared and assembled using a 3M zinc trifluoromethanesulfonate electrolyte, a glass fiber separator, and a 0.03 mm thick zinc foil. The aqueous zinc-ion battery prepared with the small molecule-coated vanadium oxide as the cathode active material has extremely stable cycling at a current density of 0.5 A g -1 and can be stably cycled 280 times.

[0051] Example 6

[0052] Using diethyl phosphonate and vanadium pentoxide with a molar ratio of 2:10 as the raw materials for the cathode active material, a small molecule-coated vanadium oxide for aqueous zinc-ion batteries with an organic small molecule coating was prepared by a simple room-temperature impregnation method. Using an active material, conductive carbon black, and polyvinylidene fluoride (PVDF) binder with a mass ratio of 7:2:1 as the cathode material (Φ = 14 mm, active material ≈ 2.5 mg), an aqueous zinc-ion battery was prepared and assembled using a 3M zinc trifluoromethanesulfonate electrolyte, a glass fiber separator, and a 0.03 mm thick zinc foil. The aqueous zinc-ion battery prepared with the small molecule-coated vanadium oxide as the cathode active material has extremely stable cycling at a current density of 0.5 A g -1 and can be stably cycled 285 times.

[0053] Comparative Example 1

[0054] Using hydroxyethylidene diphosphonic acid and vanadium pentoxide with a molar ratio of 2:10 as the raw materials for the positive electrode active material, a small molecule-coated vanadium oxide for aqueous zinc-ion batteries is prepared by a simple room-temperature impregnation method. Using the active material, conductive carbon black, and polyvinylidene fluoride (PVDF) binder with a mass ratio of 7:2:1 as the positive electrode material (Φ = 14 mm, active material ≈ 2.5 mg), an aqueous zinc-ion battery is prepared and assembled with a 3M zinc trifluoromethanesulfonate electrolyte, a glass fiber separator, and a 0.03-mm-thick zinc foil. For the aqueous zinc-ion battery prepared with the small molecule-coated vanadium oxide as the positive electrode active material, at a current density of 0.5 A g -1 the cycle stability is poor, and the capacity decay is obvious after 50 cycles.

[0055] Comparative Example 2

[0056] Using pure commercial vanadium pentoxide raw material as the positive electrode active material raw material, using the active material, conductive carbon black, and polyvinylidene fluoride (PVDF) binder with a mass ratio of 7:2:1 as the positive electrode material (Φ = 14 mm, active material ≈ 2.5 mg), an aqueous zinc-ion battery is prepared and assembled with a 3M zinc trifluoromethanesulfonate electrolyte, a glass fiber separator, and a 0.03-mm-thick zinc foil. The SEM scan of vanadium pentoxide shows irregular particles stacked by large lamellae, and the layer spacing is only 0.44 nm. For the aqueous zinc-ion battery prepared with the lamellar vanadium oxide as the positive electrode active material, at a current density of 0.5 A g -1 the Coulomb efficiency is extremely unstable, and the capacity decay is obvious, as Figure 5 shown.

[0057] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A small molecule coating vanadium oxide for aqueous zinc ion batteries, characterized in that: The small molecule coating vanadium oxide is constructed by self-assembly of organic small molecules on the surface of vanadium oxide at 10-40° C. through the dual action of hydrogen bonds and hydrophilic functional groups.

2. The small molecule coating vanadium oxide for aqueous zinc ion battery according to claim 1, characterized in that: The organic small molecules form a coating on the vanadium oxide by an impregnation method; the small molecule coating is formed by the accumulation of nano-scale particles.

3. The small molecule coating vanadium oxide for aqueous zinc ion battery according to claim 1, characterized in that: The organic small molecule contains a phosphate group, and some of its functional groups are hydrophilic functional groups; the hydrophilic functional groups include any one of an alkyl group, a hydroxyl group, and an amino group.

4. The small molecule coating vanadium oxide for aqueous zinc ion battery according to claim 1 or 3, characterized in that: The organic small molecule is at least one of 3-aminopropylphosphoric acid, 2-aminoethylphosphonic acid, and diethyl ethylphosphonate.

5. The small molecule coating vanadium oxide for aqueous zinc ion battery according to claim 1, characterized in that: The vanadium oxide is one or more of VO2, V2O5, and V2O3.

6. The small molecule coating vanadium oxide for aqueous zinc ion battery according to claim 1, characterized in that: The mass ratio of the organic small molecule to the vanadium oxide is 10:0.5-5.

7. The small molecule coating vanadium oxide for aqueous zinc ion battery according to claim 1, characterized in that: The small molecule coating vanadium oxide is used as an active substance of positive electrode material of aqueous zinc ion battery.

8. A positive electrode material for an aqueous zinc ion battery, characterized in that: Contains the small molecule coating vanadium oxide as described in any one of claims 1-7.

9. The aqueous zinc ion battery positive electrode material according to claim 8, characterized in that The positive electrode material is composed of a small molecule coating vanadium oxide active material, a carbonaceous conductive agent, and a binder; wherein the small molecule coating vanadium oxide active material accounts for 0.7 to 0.9 parts, the carbonaceous conductive agent accounts for 0.05 to 0.2 parts, and the binder accounts for 0.01 to 0.1 parts.

10. The aqueous zinc ion battery positive electrode material according to claim 8, characterized in that: Include at least one of the following technical features: A1. The separator of the aqueous zinc ion battery comprises at least one of glass fiber, nanocellulose separator, polypropylene separator and polyethylene oxide separator; A2, the electrolyte of the aqueous zinc ion battery comprises at least one of zinc trifluoromethanesulfonate, zinc chloride, zinc nitrate, zinc trifluoromethanesulfonate, and zinc hexafluoride electrolyte; A3. The carbonaceous conductive agent comprises a carbon material composed of one or more combinations or mixtures of carbon nanotubes, carbon fibers, graphene, graphene oxide, acetylene black, and carbon black; A4. The binder comprises at least one of polyvinylidene, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylic acid, polyaniline and polypyrrole.

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