A light-assisted lithium-oxygen battery positive electrode catalyst Fe2O3@Mg 0.5 Method for preparing Ti2(PO4)3

Abstract

The application provides a light-assisted lithium-oxygen battery positive electrode catalyst Fe2O3@Mg 0.5 A preparation method of Ti2(PO4)3, the method comprises the following steps: adding a magnesium source, NH4H2PO4 and an iron source into deionized water and stirring uniformly; adding titanium tetraisopropoxide and ethylenediamine into a solvent; mixing the solutions obtained in the first two steps, and then transferring the mixed solution into a reaction kettle for heating; and after centrifugal cleaning and drying, the product is obtained. The Fe2O3@Mg 0.5 Ti2(PO4)3 has a higher recombination rate of photo-generated electrons and holes, and the light absorption wavelength is increased to 647 nm; in terms of the performance of the lithium-oxygen battery, the Fe2O3@Mg 0.5 Ti2(PO4)3-1.5:1 has the largest first discharge capacity of the full battery and the smallest overpotential in the light environment, which indicates that the combination of the two materials can effectively accelerate the conversion rate of lithium peroxide and improve the performance of the lithium-oxygen battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-oxygen battery technology, and in particular to a photo-assisted lithium-oxygen battery cathode catalyst Fe2O3@Mg. 0.5 Preparation method of Ti2(PO4)3. Background Technology

[0002] Lithium-oxygen batteries, with their theoretical energy density (3500 Wh kg⁻¹) comparable to that of petroleum, have attracted widespread attention in the field of pollution-free large-scale energy storage. However, during the discharge process of lithium-oxygen batteries, the insulating properties of Li-O₂ hinder the charging and discharging of energy and the Li₂. + Problems such as poor transport and uneven decomposition causing active materials to detach from the battery result in poor actual performance of lithium-oxygen batteries, making it difficult to achieve commercial applications.

[0003] Improving battery performance by controlling the Li₂O₂ conversion rate through catalysts is an effective approach. Currently, catalysts include noble metals, perovskite oxides, spinel oxides, and layered double hydroxides.<Controlledsynthesis ofα-Fe2O3nanostructures for efficient photocatalysis> In (DOI:10.1016 / j.matlet.2015.10.152), α-Fe2O3 microspheres were synthesized and showed good performance in the photocatalytic degradation of Rhodamine B. However, photogenerated electrons and holes can undergo direct recombination, indirect recombination, and Auger recombination on Fe2O3, which reduces the utilization rate of photogenerated electrons and holes.

[0004] To address these issues, future research may need to consider improving the utilization rate of photogenerated electrons and holes, or exploring other more effective composite catalysts. Summary of the Invention

[0005] In view of this, the present invention aims to propose a photo-assisted lithium-oxygen battery cathode catalyst Fe2O3@Mg 0.5 A method for preparing Ti2(PO4)3 is proposed to solve the above problems.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A photo-assisted lithium-oxygen battery cathode catalyst Fe2O3@Mg 0.5 A method for preparing Ti2(PO4)3, comprising the following steps:

[0008] S1. Add magnesium source, NH4H2PO4 and iron source to deionized water and stir until well mixed;

[0009] S2. Dissolve tetraisopropoxide and ethylenediamine in a solvent;

[0010] S3. Mix the solutions obtained from S1 and S2, then transfer them to a reaction vessel and heat. After centrifugation, washing, and drying, the product is Fe2O3@Mg. 0.5 Ti2(PO4)3.

[0011] Furthermore, PO4 in S1 3- With magnesium source Mg 2+ The molar ratio of the substances is 10:1 to 15:1.

[0012] Furthermore, Fe in the iron source 3+ With magnesium source Mg 2+ The molar ratio of the substances is 4:1 to 8:1.

[0013] Furthermore, the Mg in the tetraisopropoxide titanium and magnesium source 2+ The molar ratio of the substances is 4:1.

[0014] Furthermore, the magnesium source is any one of magnesium chloride, magnesium nitrate, magnesium chromate, or magnesium acetate.

[0015] Furthermore, the iron source is any one of ferric chloride, ferric nitrate, or ferric acetate.

[0016] Furthermore, the alkaline solution in S2 is ethylenediamine or dihydrogen phosphate, and the solvent is ethanol.

[0017] Furthermore, the heating temperature in S3 is 160-200℃, and the heating time is more than 12 hours.

[0018] This invention also provides a photo-assisted lithium-oxygen battery cathode catalyst Fe2O3@Mg prepared by the above-described preparation method. 0.5 Ti2(PO4)3.

[0019] This invention also provides a positive electrode for a lithium-oxygen battery, which is prepared by the following method: Fe2O3@Mg as described above... 0.5 Ti2(PO4)3 is mixed with conductive agent carbon black and binder PVDF, and then NMP is added to form a slurry. The slurry is then evenly coated onto carbon paper using a doctor blade.

[0020] Compared to existing technologies, the photo-assisted lithium-oxygen battery cathode catalyst Fe2O3@Mg described in this invention... 0.5 The preparation method of Ti2(PO4)3 has the following advantages:

[0021] The catalyst Fe2O3@Mg prepared in this invention 0.5 Mg in Ti2(PO4)3 0.5 Ti2(PO4)3 is Ax M y (PO4)3 nasicon-type materials exhibit various compositions and structures. A three-dimensional framework formed by two MO6 octahedra and three PO4 tetrahedra connected by shared corner oxides can effectively separate photogenerated electrons and holes. Among these, Mg... 0.5 The synthesis method of Ti2(PO4)3 is simpler. However, Mg 0.5 Ti2(PO4)3 materials have a weak ability to capture light, which limits the application of Mg. 0.5 The photocatalytic performance of Ti2(PO4)3. Fe2O3 exhibits outstanding light-harvesting ability among many semiconductors, absorbing visible light up to 620 nm. However, due to direct recombination, indirect recombination, and Auger recombination of photogenerated electrons and holes on Fe2O3, the utilization rate of photogenerated electrons and holes is reduced. This invention provides the composite material Fe2O3@Mg. 0.5 Ti2(PO4)3 can effectively enhance Mg 0.5 Ti2(PO4)3 enhances the light absorption capacity and improves the separation rate of photogenerated electrons and holes in Fe2O3, thereby reducing the overpotential of lithium-oxygen batteries. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 These are X-ray diffraction (XRD) patterns of the materials prepared in Example 2, Comparative Example 1, and Comparative Example 2 of the present invention.

[0024] Figure 2 The Fe2O3@Mg obtained in Example 2 of this invention 0.5 Scanning electron microscope image of Ti2(PO4)3-1.5:1;

[0025] Figure 3 The photoluminescence (PL) spectra of the materials prepared in Example 2 and Comparative Example 2 of this invention are shown below.

[0026] Figure 4 The ultraviolet absorption spectra of the materials prepared in Example 2 and Comparative Example 1 of this invention are shown below.

[0027] Figure 5 The full-cell discharge capacity curves of the materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention under light and dark conditions when applied to lithium-oxygen batteries;

[0028] Figure 6 This is a comparison of the first overpotential of the materials prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention when applied to lithium-oxygen batteries. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0030] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Example 1

[0032] Fe2O3@Mg 0.5 The preparation method of Ti2(PO4)3-1:1 includes the following steps:

[0033] S1. Add 0.643g (CH3COO)2Mg·4H2O (0.003mol), 3.451g NH4H2PO4 (0.03mol) and 4.848g Fe(NO3)3·9H2O (0.012mol) to 30ml of deionized water and stir at 300rpm for 15min.

[0034] S2. Dissolve 3.411g of tetraisopropoxide titanium (0.012mol) and 10ml of ethylenediamine (to provide an alkaline environment) in 30ml of ethanol;

[0035] S3. Mix the solutions from S1 and S2 and stir at 300 rpm for 30 min. Transfer the mixture to a 100 ml reactor and heat at 180°C for 20 h. After centrifugation, washing, and drying, obtain Fe2O3@Mg. 0.5 Ti2(PO4)3-1:1, where 1:1 represents Fe2O3 and Mg 0.5 The ratio of Ti2(PO4)3 is 1:1.

[0036] Preparation method of positive electrode sheet for lithium-oxygen battery:

[0037] The Fe2O3@Mg obtained above 0.5 Ti2(PO4)3- 1:1, conductive agent carbon black, and binder PVDF are mixed evenly in a mortar at a ratio of 6:3:1. An appropriate amount of NMP is added to form a slurry, which is then evenly coated onto carbon paper using a scraper to obtain the Fe2O3@Mg positive electrode for lithium-oxygen batteries. 0.5 Ti2(PO4)3-1:1.

[0038] Example 2

[0039] The difference between this embodiment and Example 1 is that the amount of Fe(NO3)3·9H2O added in S1 is 7.272g, and the resulting catalyst is named Fe2O3@Mg. 0.5 Ti2(PO4)3-1.5:1.

[0040] The remaining operations are the same as in Example 1.

[0041] Example 3

[0042] The difference between this embodiment and Example 1 is that the amount of Fe(NO3)3·9H2O added in S1 is 9.696g, and the resulting catalyst is named Fe2O3@Mg. 0.5 Ti2(PO4)3-2:1.

[0043] The remaining operations are the same as in Example 1.

[0044] Comparative Example 1

[0045] Mg(CH3COO)2 and NH4H2PO4 were added to deionized water at a molar ratio of 1:5, resulting in a final aqueous solution concentration of 2M. Then, 20 mL of this solution was added to 0.2M tetraisopropoxide and 50 mL of ethanol, and the mixture was transferred to a 100 mL hydrothermal reactor and heated at 120°C for 12 hours. After centrifugation and drying, Mg was obtained. 0.5 The preparation method of Ti2(PO4)3 electrode is the same as in Example 1.

[0046] Comparative Example 2

[0047] A mixture of 90 mL of water and anhydrous ethanol (volume ratio 1:1, anhydrous ethanol purity ≥99.7%) was prepared. 4 g of Fe(NO3)3·9H2O and 10 mL of ethylenediamine were added to the solution, and the mixture was incubated at 180°C for 20 hours. The powder was collected by centrifugation, yielding the Fe2O3 nanorods of Comparative Example 2. The electrode preparation method was the same as in Example 1.

[0048] Comparative Example 3

[0049] Mg 0.5 Ti2(PO4)3 and Fe2O3 nanorods were mixed at a molar ratio of 1:1 using a disperser at 300 rpm for 30 min to obtain Comparative Example 3, which was named Fe2O3@Mg. 0.5 Ti2(PO4)3-pure.

[0050] Electrolyte and separator: 1M LiTFSI@tetraethylene glycol dimethyl ether (TEGDME) is used as the electrolyte, and Whatman W / D glass fiber membrane (25mm thick) is used as the separator.

[0051] Battery assembly: Assemble the battery in the following order: negative electrode shell, lithium plate, separator, electrolyte, positive electrode plate, gasket, and positive electrode shell again. Use a button cell sealing machine to compact the assembly to obtain a Li-O2 battery. Charge-discharge tests should be conducted in an oxygen glove box. Test results are as follows.

[0052] Figure 1These are the X-ray diffraction (XRD) patterns of the materials prepared in Example 2, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 1 As can be seen, the XRD image of the material prepared in Example 2 is compared with that of Mg. 0.5 Comparing Ti2(PO4)3-PDF#86-0850 and Fe2O3-PDF#33-0664 cards, the synthesized material exhibits the characteristic peaks of both materials.

[0053] Figure 2 The Fe2O3@Mg obtained in Example 2 of this invention 0.5 Scanning electron microscope (SEM) image of Ti2(PO4)3-1.5:1. The Fe2O3@Mg synthesized in Experimental Example 2 can be seen. 0.5 Ti2(PO4)3-1.5:1 consists of ferric oxide nanorods with a diameter of approximately 100 nm and encapsulated amorphous Mg. 0.5 It is composed of Ti2(PO4)3.

[0054] Figure 3 The photoluminescence (PL) spectra of the materials prepared in Example 2 and Comparative Example 2 of this invention are shown. The recombination rate of photogenerated electrons and holes can be obtained through PL testing; the lower the intensity of the characteristic peak, the slower the recombination rate. Fe2O3@Mg 0.5 The higher peak intensity of Ti2(PO4)3-1.5:1 indicates that the composite rate of the material is improved after composite processing.

[0055] Figure 4 The ultraviolet absorption spectra of the materials prepared in Example 2 and Comparative Example 1 of this invention are shown below; Figure 4 It can be obtained that Mg 0.5 The light absorption wavelength of Ti2(PO4)3 is 551 nm, which increases to 647 nm after compositing. This indicates that compositing Fe2O3 can improve the light absorption capacity of the material.

[0056] Figure 5 The following are the full-cell discharge capacity curves of the materials prepared in the embodiments and comparative examples of this invention, applied to lithium-oxygen batteries under both light and dark conditions; through... Figure 5 It is possible to obtain: Fe2O3@Mg 0.5 Ti2(PO4)3-1.5:1 exhibits the highest initial discharge capacity of 14497 mAh / g under light conditions, Fe2O3@Mg 0.5 Ti2(PO4)3-1:1 has a capacity of 13377 mAh / g, Fe2O3@Mg 0.5 The Ti2(PO4)3-2:1 ratio is 9534 mAh / g, far exceeding that of Mg. 0.5The discharge capacity of Ti2(PO4)3 and Fe2O3 under light conditions demonstrates that the combination of these two materials can improve catalytic activity and enhance the performance of lithium-oxygen batteries. Furthermore, the comparative example of 3Fe2O3@Mg... 0.5 Ti2(PO4)3-pure can be found that if only Mg is used... 0.5 A simple physical mixture of Ti2(PO4)3 and Fe2O3 results in a full-cell discharge capacity only slightly higher than that of Mg alone. 0.5 Ti2(PO4)3 and Fe2O3 are slightly better, but still much worse than the composite, indicating that simple mixing cannot improve catalytic ability.

[0057] Figure 6 This is a comparison of the first overpotential of the materials prepared in the embodiments and comparative examples of the present invention when applied to lithium-oxygen batteries. Figure 6 It is possible to obtain Fe2O3@Mg 0.5 Ti2(PO4)3-1.5:1 exhibits the lowest overpotential under light conditions, a result consistent with the initial discharge capacity of the full cell.

[0058] In summary, the Fe2O3@Mg prepared in this invention... 0.5 Ti2(PO4)3 exhibits a higher recombination rate of photogenerated electrons and holes, increasing the light absorption wavelength to 647 nm; in terms of lithium-oxygen battery performance, Fe2O3@Mg 0.5 Ti2(PO4)3-1.5:1 exhibits the largest initial discharge capacity and the smallest overpotential in a light-bearing environment, indicating that the combination of the two materials can effectively accelerate the conversion rate of lithium peroxide and improve the performance of lithium-oxygen batteries.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A photo-assisted lithium-oxygen battery cathode catalyst Fe2O3@Mg 0.5 The method for preparing Ti2(PO4)3 is characterized by: The method includes the following steps: S1. Add magnesium source, NH4H2PO4 and iron source to deionized water and stir until well mixed; S2. Dissolve tetraisopropoxide and ethylenediamine in a solvent; S3. Mix the solutions obtained from S1 and S2, then transfer them to a reaction vessel and heat. After centrifugation, washing, and drying, the product yields Fe2O3@Mg. 0.5 Ti2(PO4)3; PO4 in S1 3- With magnesium source Mg 2+ The molar ratio of the substances is 10:1 to 15:1; Fe in iron source 3+ With magnesium source Mg 2+ The molar ratio of the substances is 4:1 to 8:1; Tetraisopropoxide titanium and magnesium source Mg 2+ The molar ratio of the substances is 4:1; The solvent in S2 is ethanol; The heating temperature in S3 is 160-200℃, and the heating time is more than 12 hours.

2. The photo-assisted lithium-oxygen battery cathode catalyst Fe2O3@Mg according to claim 1 0.5 The method for preparing Ti2(PO4)3 is characterized by: The magnesium source is any one of magnesium chloride, magnesium nitrate, magnesium chromate, or magnesium acetate.

3. The photo-assisted lithium-oxygen battery cathode catalyst Fe2O3@Mg according to claim 1 0.5 The method for preparing Ti2(PO4)3 is characterized by: The iron source is any one of ferric chloride, ferric nitrate, or ferric acetate.

4. A photo-assisted lithium-oxygen battery cathode catalyst Fe2O3@Mg prepared by the preparation method according to any one of claims 1-3 0.5 Ti2(PO4)3.

5. A positive electrode sheet for a lithium-oxygen battery, characterized in that: The electrode was prepared by the following method: Fe2O3@Mg as described in claim 4 was used... 0.5 Ti2(PO4)3 is mixed with conductive agent carbon black and binder PVDF, and then NMP is added to form a slurry. The slurry is then evenly coated onto carbon paper using a doctor blade.

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