A molybdenum trioxide material containing oxygen vacancies, and a preparation method and application thereof

Abstract

The application discloses a molybdenum trioxide material containing oxygen vacancies, which is prepared by a seed layer assisted hydrothermal method, and preparation raw materials include seed liquid and precursor solution; the chemical formula of the molybdenum trioxide material is MoO 3‑x , wherein 0

Description

Technical Field

[0001] This invention belongs to the field of energy storage materials technology, specifically relating to an oxygen-vacancy molybdenum trioxide material, its preparation method, and its application. Background Technology

[0002] With increasing international concern about energy security and climate change, developing sustainable energy conversion and storage technologies has become a global trend. Developing high-performance energy storage systems can not only promote the widespread use of electric vehicles, reduce dependence on fossil fuels, and mitigate the greenhouse effect, but it is also an effective way to utilize intermittent renewable energy on a large scale. Traditional nickel-metal hydride batteries and lead-acid batteries are gradually being phased out of the market due to their low energy density, environmental pollution, and poor cycle performance.

[0003] Currently, lithium-ion batteries are widely used in portable electronic devices. However, lithium resources are limited, and organic batteries pose serious safety hazards, making the development of lithium-ion batteries face numerous challenges. Therefore, developing safer and cheaper new flexible energy storage systems has become more attractive. Compared with commonly used lithium-ion batteries, aqueous zinc-ion batteries have attracted widespread attention due to their abundant reserves, low cost, high safety performance, high ionic conductivity, and simple battery assembly process, and are expected to become the next generation of green and environmentally friendly batteries. However, the development of aqueous zinc-ion batteries still faces significant challenges. The theoretical capacity of the zinc anode is relatively high (820 mAh g / g). -1 In contrast, the specific capacity of currently reported zinc-ion battery cathode materials is relatively low, resulting in lower energy density in aqueous zinc-ion batteries. Therefore, exploring high-performance cathode materials has become crucial in determining the performance of aqueous zinc-ion batteries.

[0004] Among the reported zinc-ion battery cathode materials, molybdenum trioxide (Mot) has attracted widespread attention due to its low cost, high theoretical capacity, and good electrochemical activity. However, its poor conductivity, easy solubility in neutral or weakly acidic aqueous electrolytes, and tendency to structural collapse during charge and discharge significantly limit its application range. Therefore, developing a Mot electrode material with a simple preparation process and excellent electrochemical performance is of great significance. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a molybdenum trioxide (MoO) rich in oxygen vacancies. 3-x )Material.

[0006] The present invention also proposes a method for preparing molybdenum trioxide materials containing oxygen vacancies.

[0007] The present invention also proposes a positive electrode.

[0008] This invention also proposes an aqueous zinc-ion battery.

[0009] According to one aspect of the present invention, a molybdenum trioxide material containing oxygen vacancies is provided, which is prepared by a seed-layer assisted hydrothermal method, wherein the raw materials include a seed solution and a precursor solution; the chemical formula of the molybdenum trioxide material is MoO. 3-x , of which 0 <x<1。

[0010] The seed layer method involves pretreating the substrate with a seed solution containing a molybdenum source, which gives the substrate surface active sites, thus accelerating nucleation and aiding growth during the hydrothermal reaction.

[0011] The molybdenum trioxide material containing oxygen vacancies of the present invention has at least the following beneficial effects:

[0012] This invention utilizes a seed-layer-assisted hydrothermal method to effectively grow oxygen-vacant molybdenum trioxide in situ on a substrate. The oxygen-vacant molybdenum trioxide of this invention exhibits a larger interlayer spacing, which is beneficial for zinc ion diffusion.

[0013] In some embodiments of the present invention, the molybdenum trioxide material containing oxygen vacancies is an α-orthorhombic phase.

[0014] In some embodiments of the present invention, the seed solution includes a molybdenum source and an inorganic acid.

[0015] In some embodiments of the present invention, the precursor solution includes a molybdenum source, an inorganic acid, and a surfactant.

[0016] In some embodiments of the present invention, the molybdenum source in the seed solution and the precursor is independently selected from at least one of sodium molybdate, ammonium molybdate, and potassium molybdate.

[0017] In some embodiments of the present invention, the inorganic acid in the seed liquid and the precursor is a strong inorganic acid, and is independently selected from at least one of nitric acid and hydrochloric acid.

[0018] In some embodiments of the present invention, the surfactant includes at least one of hexadecyltrimethylammonium bromide, dodecyldimethylbenzylammonium bromide, and pyridine salts.

[0019] According to some preferred embodiments of the present invention, the concentration of molybdenum source in the seed solution is 0.2-0.6 mol / L, for example 0.3 mol / L, 0.4 mol / L or 0.5 mol / L; and the concentration of hydrochloric acid is 1-3 mol / L, for example 2 mol / L.

[0020] According to some preferred embodiments of the present invention, in the precursor solution, the concentration of the molybdenum source is 0.02-0.20 mol / L, for example 0.05 mol / L, 0.10 mol / L or 0.15 mol / L; and the concentration of nitric acid is 3.5-7.6 mol / L, for example 4 mol / L, 5 mol / L, 6 mol / L or 7 mol / L.

[0021] According to some preferred embodiments of the present invention, the concentration of the surfactant in the precursor solution is 0.055-0.080 mol / L; preferably, the concentration of the surfactant is 0.06-0.08 mol / L; more preferably, the concentration of the surfactant is 0.065-0.075 mol / L, for example, about 0.07 mol / L.

[0022] According to another aspect of the present invention, a method for preparing a molybdenum trioxide material containing oxygen vacancies is provided, comprising the following steps:

[0023] The substrate was soaked in seed solution, removed, and dried on a heating plate to obtain a pretreated substrate with a seed layer growing on it.

[0024] The pretreated substrate and precursor solution are mixed and subjected to a hydrothermal reaction to obtain the molybdenum trioxide material containing oxygen vacancies.

[0025] The growth of the seed layer, i.e., the pretreatment of the substrate, plays a crucial role in the growth of molybdenum oxide materials. It provides growth sites for molybdenum oxide, making the synthesized material less prone to detachment from the substrate and enhancing its conductivity. Without this substrate pretreatment step, the growth area of ​​molybdenum oxide in the synthesized material is not uniform enough, which greatly affects the electrochemical performance of the material.

[0026] According to some preferred embodiments of the present invention, molybdenum trioxide nanowires containing oxygen vacancies can be directly grown on the substrate surface by a seed layer-assisted hydrothermal method. The incorporation of surfactants effectively reduces hexavalent molybdenum ions without dissolving the molybdenum trioxide material, providing more oxygen vacancy active sites, expanding the ion interlayer spacing, which is beneficial for ion insertion and extraction, resulting in higher capacity, good rate performance and cycling stability.

[0027] In some embodiments of the present invention, the substrate includes, but is not limited to, at least one of carbon cloth, carbon paper, and nickel foam.

[0028] According to some preferred embodiments of the present invention, the substrate is carbon cloth.

[0029] In some embodiments of the present invention, the substrate is soaked in the seed solution for 2 to 5 minutes.

[0030] In some embodiments of the present invention, the temperature of the heating plate is 320-360°C; preferably, the temperature of the heating plate is 330-360°C; for example, it can be about 330°C, about 340°C, about 350°C or about 360°C.

[0031] In some embodiments of the present invention, the drying time is 5-10 seconds.

[0032] In some embodiments of the present invention, the hydrothermal reaction temperature is 150–170°C; preferably, the hydrothermal reaction temperature is 155–165°C; for example, it can be about 160°C.

[0033] In some embodiments of the present invention, the hydrothermal reaction time is 4 to 8 hours; preferably, the hydrothermal reaction time is 5 to 7 hours; for example, it can be about 6 hours.

[0034] According to another aspect of the invention, a positive electrode is provided, comprising the above-described molybdenum trioxide material containing oxygen vacancies.

[0035] According to another aspect of the present invention, an aqueous zinc-ion battery is provided, which includes the above-described positive electrode.

[0036] In some embodiments of the present invention, the aqueous zinc-ion battery further includes a negative electrode, an electrolyte, and a separator.

[0037] According to some preferred embodiments of the present invention, the negative electrode can be one of zinc sheet, zinc powder, electroplated zinc, zinc foam or elemental material.

[0038] According to some preferred embodiments of the present invention, the diaphragm may be selected from at least one of nonwoven fabric, glass fiber, polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride or polycarbonate.

[0039] According to some preferred embodiments of the present invention, the electrolyte comprises a soluble zinc salt.

[0040] According to some more preferred embodiments of the present invention, the soluble zinc salt may be at least one of zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, zinc hexafluoroate, or zinc trifluoromethanesulfonate.

[0041] As used herein, when used in conjunction with numerical values, the term "about" means a set or range of values. For example, "about X" includes a range of values ​​that are ±10%, ±5%, ±2%, ±1%, ±0.5%, ±0.2%, or ±0.1% of X, where X is a numerical value. In one embodiment, the term "about" refers to a range of values ​​that are 5% more or less than a specific value. In another embodiment, the term "about" refers to a range of values ​​that are 2% more or less than a specific value. In yet another embodiment, the term "about" refers to a range of values ​​that are 1% more or less than a specific value.

[0042] This invention utilizes a seed-layer-assisted hydrothermal method to effectively grow molybdenum trioxide containing oxygen vacancies in situ on a substrate. Pre-treatment of the substrate leaves growth sites on its surface, which facilitates the growth of molybdenum oxide during the hydrothermal process, prevents it from detaching, strengthens the connection between the material and the substrate, and enhances the material's conductivity and stability.

[0043] The oxygen-vacant molybdenum trioxide prepared by this invention has a larger interlayer spacing, which is conducive to the diffusion of zinc ions. When used as a positive electrode material for zinc-ion batteries, it has higher capacity, good conductivity, good rate performance and cycle stability. Attached Figure Description

[0044] Figure 1 (a) is a high-magnification scanning electron microscope image of the molybdenum trioxide material prepared in Comparative Example 1; Figure 1 (b) is a high-magnification scanning electron microscope image of the molybdenum trioxide material containing oxygen vacancies prepared in Example 1;

[0045] Figure 2 (a) are the X-ray diffraction patterns of the molybdenum trioxide material with oxygen vacancies prepared in Example 1 and the molybdenum trioxide material prepared in Comparative Example 1. Figure 2 (b) shows the impedance characterization diagrams of the molybdenum trioxide material with oxygen vacancies prepared in Example 1 and the molybdenum trioxide material prepared in Comparative Example 1.

[0046] Figure 3 (a) shows the molybdenum trioxide electrode with oxygen vacancies in Example 1 and the molybdenum trioxide electrode in Comparative Example 1 at 5 mV·s. -1 The cyclic voltammetry curve below; Figure 3 (b) shows the molybdenum trioxide electrode containing oxygen vacancies in Example 1 and the molybdenum trioxide electrode in Comparative Example 1 at a current density of 1 A·g. -1 The constant current charge-discharge curve is shown below.

[0047] Figure 4 (a) is a rate performance graph of the molybdenum trioxide electrode with oxygen vacancies in Example 1 and the molybdenum trioxide electrode in Comparative Example 1. Figure 4(b) shows the molybdenum trioxide electrode containing oxygen vacancies in Example 1 and the molybdenum trioxide electrode in Comparative Example 1 at a current density of 1 A·g. -1 Constant current charge-discharge cycle performance diagram;

[0048] Figure 5 (a) shows the molybdenum trioxide electrodes containing oxygen vacancies prepared in Examples 1, 3, and 4 at 5 mV·s. -1 The cyclic voltammetry curve below; Figure 5 (b) The molybdenum trioxide electrodes containing oxygen vacancies prepared for Examples 1, 3, and 4 were tested at a current density of 1 A·g. -1 The constant current charge-discharge curve is shown below.

[0049] Figure 6 These are impedance characterization diagrams of the molybdenum trioxide electrodes containing oxygen vacancies prepared in Examples 1, 3, and 4. Detailed Implementation

[0050] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0051] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0052] Example 1

[0053] This embodiment provides a molybdenum trioxide material containing oxygen vacancies, the preparation method of which includes the following steps:

[0054] S1. Dissolve 2.5g Na2MoO4·2H2O and 5mL HCl (37wt%) completely in 20mL deionized water to form solution A (seed solution). Soak clean carbon cloth in solution A for 5min, then remove it and heat it on a 350℃ heating plate for 10-15s. Repeat the above steps 1-2 times to obtain pretreated carbon cloth.

[0055] S2. Add 0.3g of (NH4)6Mo7O 2410 mL of HNO3 (65 wt%) and 0.5 g of CTAB (hexadecyltrimethylammonium bromide) were dissolved in 10 mL of deionized water and stirred thoroughly until completely dissolved to form solution B (precursor solution). 20 mL of the precursor solution was poured into a 50 mL reactor. The pretreated carbon cloth from S1 was placed in the 50 mL reactor and reacted in a 160°C oven for 6 hours. After the reaction was complete, the carbon cloth was washed and dried to synthesize molybdenum trioxide (MoO2) containing oxygen vacancies. 3-x )Material.

[0056] Example 2

[0057] This embodiment provides a molybdenum trioxide material containing oxygen vacancies. The raw materials and preparation method are the same as in Embodiment 1, except that the hydrothermal reaction temperature in step S2 is 150°C.

[0058] Example 3

[0059] This embodiment provides an oxygen-vacancy molybdenum trioxide material. The raw materials and preparation method are the same as in Embodiment 1, except that the hydrothermal reaction temperature in step S2 is 170°C.

[0060] Example 4

[0061] This embodiment provides a molybdenum trioxide material containing oxygen vacancies. The raw materials and preparation method are the same as in Embodiment 1, except that the hydrothermal reaction time in step S2 is 4 hours.

[0062] Example 5

[0063] This embodiment provides a molybdenum trioxide material containing oxygen vacancies. The raw materials and preparation method are the same as in Embodiment 1, except that the hydrothermal reaction time in step S2 is 8 hours.

[0064] Comparative Example 1

[0065] This comparative example provides a molybdenum trioxide material, the preparation method of which includes the following steps:

[0066] S1. Dissolve 2.5g Na2MoO4·2H2O and 5mL HCl (37wt%) completely in 20mL deionized water to form solution A (seed solution). Soak clean carbon cloth in solution A for 5min, then remove it and heat it on a 350℃ heating plate for 10-15s. Repeat the above steps 1-2 times to obtain pretreated carbon cloth.

[0067] S2. Add 0.3g of (NH4)6Mo7O 24Dissolve 10 mL of HNO3 (65 wt%) in 10 mL of deionized water and stir thoroughly until completely dissolved to form solution B (precursor solution). Pour 20 mL of the precursor solution into a 50 mL reactor. Place the pretreated carbon cloth into the 50 mL reactor and place it in a 160 °C forced-air oven for 6 h. After the reaction is complete, clean and dry the carbon cloth to synthesize molybdenum trioxide (MoO3) material.

[0068] Comparative Example 2

[0069] This comparative example provides a molybdenum trioxide material, the preparation method of which includes the following steps:

[0070] 0.3g (NH4)6Mo7O 24 Dissolve 10 mL of HNO3 (65 wt%) in 10 mL of deionized water and stir thoroughly until completely dissolved to form a precursor solution. Pour 20 mL of the precursor solution into a 50 mL reactor. Place the carbon cloth into the 50 mL reactor and place it in a 160 °C forced-air oven for 6 h. After the reaction is complete, clean and dry the carbon cloth to obtain the synthesized molybdenum trioxide (MoO3) material.

[0071] Comparative Example 3

[0072] The raw materials and preparation method of this comparative example are the same as those in Example 1, except that the amount of CTAB in step S2 is 0.4g.

[0073] Comparative Example 4

[0074] The raw materials and preparation method of this comparative example are the same as those in Example 1, except that the amount of CTAB in step S2 is 0.6g.

[0075] Performance testing

[0076] The molybdenum trioxide material prepared in the above examples and comparative examples was used as a positive electrode material for an aqueous zinc-ion battery. Glass fiber was used as a separator, 2M Zn2SO4 was added as an electrolyte, and the battery was encapsulated into a button cell.

[0077] The molybdenum trioxide containing oxygen vacancies prepared in Example 1 and the molybdenum trioxide prepared in Comparative Example 1 were tested by thermal field emission scanning electron microscopy. The results are as follows: Figure 1 (a) Figure 1 As shown in (b), the two have similar morphologies, indicating that the prepared molybdenum trioxide containing oxygen vacancies did not undergo morphological changes.

[0078] Figure 2(a) Comparison of X-ray diffraction patterns of molybdenum trioxide containing oxygen vacancies prepared in Example 1 and molybdenum trioxide prepared in Comparative Example 1. It can be seen that both correspond well to the PDF card of molybdenum trioxide, and the molybdenum trioxide containing oxygen vacancies is slightly shifted to the left, indicating a larger interlayer spacing. Furthermore, Figure 2 The impedance diagram in (b) further confirms this, showing a lower impedance.

[0079] Figure 3 (a) Cyclic voltammetry curves of molybdenum trioxide containing oxygen vacancies prepared in Example 1 and molybdenum trioxide prepared in Comparative Example 1 at a scan rate of 5 mV / s. It can be seen that, compared to MoO3 prepared in Comparative Example 1, the MoO3 prepared in Example 1... 3-x A larger curve area suggests potentially better performance. Figure 3 (b) The molybdenum trioxide containing oxygen vacancies prepared in Example 1 and the molybdenum trioxide prepared in Comparative Example 1 were subjected to a current density of 1 A g. -1 The constant current charge-discharge curves under the given conditions show that MoO 3-x Its specific capacity is significantly higher than that of MoO3.

[0080] Figure 4 (a) Rate plots of molybdenum trioxide containing oxygen vacancies prepared in Example 1 and molybdenum trioxide prepared in Comparative Example 1 at different current densities. As can be seen from the figure, MoO 3-x Its rate performance is significantly better than that of MoO3. Figure 4 (b) is a constant current charge-discharge cycle life graph of the oxygen-vacancy-containing molybdenum trioxide prepared in Example 1 and the molybdenum trioxide prepared in Comparative Example 1. As can be seen from the graph, after 500 cycles, MoO... 3-x Its specific capacity is much higher than that of MoO3, which shows that MoO 3-x It exhibits good rate performance and cycle stability.

[0081] Furthermore, Examples 2-5 further modified the temperature and time based on Example 1. The molybdenum trioxide material synthesized at the temperatures of Examples 2-3 exhibited some uneven growth; the molybdenum trioxide material synthesized at the time limits of Examples 4-5 showed that the hydrothermal time had a certain impact on the growth length of the nanowires. Therefore, based on experimental optimization, the time and temperature set in Example 1 were optimal.

[0082] exist Figure 5 As can be seen from the cyclic voltammetry curve in (a), the area of ​​the curve in Example 1 is larger than that in Comparative Example 3 and Comparative Example 4. Figure 5 (b) indicates that Examples 1, 3, and 4 were performed at a current density of 1 A·g -1 The constant current charge-discharge curves under these conditions show significant differences. Meanwhile, from... Figure 6As can be seen from the impedance characterization diagram, the impedance value of Example 1 is smaller than that of Comparative Example 3 and Comparative Example 4, and it has better conductivity.

[0083] Unlike Example 1, Comparative Examples 3-4 only changed the amount of CTAB doping. The inventors found in the experiment that continuing to increase the doping amount did not lead to the formation of other new phases in the reaction, and the electrochemical performance was not further improved.

[0084] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A molybdenum trioxide material containing oxygen vacancies, characterized in that, The seed layer assisted hydrothermal method comprises the following steps: The substrate is soaked with the seed liquid, taken out, and dried on a heating plate to obtain a pretreated substrate with a seed layer; The pretreated substrate and the precursor solution are mixed to perform a hydrothermal reaction to obtain the molybdenum trioxide material; The preparation raw material comprises seed liquid and precursor solution; the chemical formula of the molybdenum trioxide material is MoO 3-x wherein 0 < x < 1. The seed liquid comprises a molybdenum source and hydrochloric acid; and the precursor solution comprises a molybdenum source, nitric acid and a surfactant; The molybdenum source in the seed liquid and the precursor is independently selected from at least one of sodium molybdate, ammonium molybdate and potassium molybdate; The surfactant comprises at least one of cetyltrimethylammonium bromide, dodecyl dimethyl benzyl ammonium bromide and pyridine salt; the concentration of nitric acid in the precursor solution is 3.5 7.6 mol / L; The concentration of the surfactant in the precursor solution is 0.055-0.080 mol / L.

2. The molybdenum trioxide material of claim 1, wherein, The concentration of the molybdenum source in the seed liquid is 0.2-0.6 mol / L, and the concentration of hydrochloric acid is 1-3 mol / L; and the concentration of the molybdenum source in the precursor solution is 0.02-0.20 mol / L.

3. The method of producing a molybdenum trioxide material according to claim 1 or 2, characterized in that, The seed layer assisted hydrothermal method comprises the following steps: The substrate is soaked with the seed liquid, taken out, and dried on a heating plate to obtain a pretreated substrate with a seed layer; The pretreated substrate and the precursor solution are mixed to perform a hydrothermal reaction to obtain the molybdenum trioxide material.

4. The preparation method according to claim 3, characterized in that, The substrate comprises at least one of carbon cloth, carbon paper and foamed nickel.

5. The production method according to claim 3 or 4, characterized by, The soaking time is 2-5 min; the temperature of the heating plate is 320-360 DEG C; and the drying time is 5-10 s.

6. The production method according to claim 3 or 4, characterized by, The hydrothermal reaction temperature is 150-170 DEG C; and the hydrothermal reaction time is 4-8 h.

7. An aqueous zinc-ion battery, characterized in that, The seed layer assisted hydrothermal method comprises the following steps: The substrate is soaked with the seed liquid, taken out, and dried on a heating plate to obtain a pretreated substrate with a seed layer; The pretreated substrate and the precursor solution are mixed to perform a hydrothermal reaction to obtain the molybdenum trioxide material.

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