Preparation method and application of SnO2 / MOF-5 composite negative electrode material

Abstract

The invention belongs to the technical field of preparation of electrode materials, and discloses a preparation method and application of a SnO2 / MOF-5 composite negative electrode material, the SnO2 / MOF-5 composite negative electrode material comprises a matrix metal organic framework MOF-5, SnO2 nanoparticles are attached to the matrix MOF-5, and the molar ratio of stannous chloride dihydrate to zinc nitrate hexahydrate in the synthesis process is 1: (3-9). Preparing SnO2 / MOF-5 composite materials with different SnO2 loading capacities by utilizing a solvothermal method; and after the sample is cooled to room temperature, washing and vacuum drying are carried out, and SnO2 / MOF-5 is obtained. When in use, the SnO2 / MOF-5 composite material is uniformly coated on the surface of a zinc sheet by a blade coating method. The material can be used as an electrode to be applied to an aqueous zinc ion battery. The material can effectively inhibit the negative electrode side reaction of the aqueous zinc ion battery.

Description

Technical Field

[0001] This invention relates to a method for preparing an electrode material and its application, and more specifically, to a method for preparing a MOF-5 / SnO2 composite electrode material and its application. Background Technology

[0002] Rechargeable batteries occupy a crucial position in the global energy system. Zinc resources are abundant and relatively inexpensive, and aqueous zinc-ion batteries, using aqueous solutions as electrolytes, offer significantly higher safety than lithium-ion batteries that use organic electrolytes. Furthermore, zinc metal anodes possess a high theoretical capacity (820 mAh g⁻¹). -1 Due to its low redox potential (-0.76 V vs. SHE), aqueous zinc-ion batteries have attracted widespread attention in the academic community.

[0003] Despite the promising application prospects of aqueous zinc-ion batteries, their performance and cycle life are still constrained by several issues. The main problems with the negative electrode are as follows: First, uneven deposition of zinc ions on the negative electrode surface during cycling can easily lead to the growth of electrolytic zinc dendrites, which may puncture the separator and cause a short circuit. Second, commonly used zinc sheet negative electrodes have poor stability in aqueous electrolytes, easily undergoing hydrogen evolution reactions during cycling, accompanied by corrosion and passivation. Furthermore, continuous side reactions and irreversible deformation of the electrode structure during zinc deposition / dissolution further exacerbate the degradation of battery performance. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the present invention aims to provide a SnO2 / MOF-5 composite anode material with high zinc affinity; another purpose of the present invention is to provide a method for preparing SnO2 / MOF-5@Zn aqueous zinc ion anode.

[0005] The SnO2 / MOF-5 composite anode material includes metal-organic framework material MOF-5 and zinc-loving metal oxide SnO2, with SnO2 uniformly attached to the surface of MOF-5.

[0006] The preparation method of the SnO2 / MOF-5 composite anode material adopts a solvothermal one-pot method, including the following steps: Zinc nitrate hexahydrate was placed in a reaction flask, DMF was added and stirred to dissolve it. Then, terephthalic acid, triethylamine, and stannous chloride dihydrate were added to the solution in sequence and stirred to dissolve. The mixture was then transferred to a reaction vessel, sealed and heated. After the reaction was completed, the mixture was allowed to cool to room temperature naturally. The solid was then separated from the mixture by centrifugation, and the sample was washed with DMF and ethanol and dried under vacuum to obtain SnO2 / MOF-5 powder.

[0007] The molar ratio of stannous chloride dihydrate to zinc nitrate hexahydrate is 1:3~9; the molar ratio of zinc nitrate hexahydrate to terephthalic acid is 3:1; and the molar ratio of zinc nitrate hexahydrate to triethylamine is 0.72:1. In the mixed solution, the concentration of zinc nitrate hexahydrate is 0.090 M, the concentration of terephthalic acid is 0.030 M, and the concentration of triethylamine is 0.125 M.

[0008] Preferably, the molar ratio of stannous chloride dihydrate to zinc nitrate hexahydrate is 1:6.

[0009] The temperature of the sealed heating is 80~150℃, and the heating time is 12~24 h.

[0010] The vacuum drying temperature is 40~100℃, and the drying time is 6~24 h.

[0011] Application of the above SnO2 / MOF-5 composite anode material in aqueous zinc-ion batteries.

[0012] SnO2 / MOF-5 and PVDF are mixed and ground thoroughly according to the ratio. Then NMP is added and stirred to form a suspension. The suspension is then evenly coated onto the clean zinc sheet surface using a scraper. After drying and allowing the solvent to evaporate, the sheet is sliced.

[0013] Further, the mass ratio of SnO2 / MOF-5 to PVDF is (7~9):(3~1); preferably, the mass ratio of SnO2 / MOF-5 to PVDF is 9:1.

[0014] The concentration of the SnO2 / MOF-5 composite anode material in NMP is 0.650~0.750 g / mL.

[0015] Furthermore, the stirring time was 6 hours after adding NMP; The drying conditions are: vacuum drying at 50~100 ℃ for 6~24 h.

[0016] The beneficial effects of this invention are as follows: In this invention, SnO2, with its high zinc affinity and ionic conductivity, serves as a preferential nucleation site to guide Zn formation. 2+ Uniform deposition; while MOF-5 acts as an ion sieve and physical barrier, utilizing its regular channels to promote Zn deposition. 2+ The coating synergistically suppresses side reactions by transporting and restricting the passage of water molecules. When the molar ratio of stannous chloride dihydrate to zinc nitrate hexahydrate is 1:6, the synthesized SnO2 / MOF-5 material exhibits optimal overall performance, achieving an optimal balance between interfacial ionic conductivity and side reaction suppression. Thanks to this synergistic effect, a symmetric cell assembled with the modified zinc anode achieves a current density of 1 mAcm⁻¹.-2 Under certain conditions, it can cycle stably for more than 2400 hours, which is 20 times the cycling time of bare zinc, and the deposition overpotential is significantly lower than that of symmetric cells assembled with bare zinc. Attached Figure Description

[0017] Figure 1 The X-ray diffraction patterns of the powder materials prepared in Examples 1-3 and Comparative Example 2 are shown below. Figure 2 These are scanning electron microscope (SEM) images of the powder materials prepared in Examples 1-3; Figure 3 Transmission electron microscope (TEM) images of the powder material prepared in Example 2; Figure 4 EIS images of Zn / / Zn symmetric cells assembled from electrode sheets prepared in Examples 1-3 and Comparative Examples 1-2 before cycling; Figure 5 The coulombic efficiency diagrams are shown for the asymmetric cells (Zn / / Cu) assembled from the electrode sheets prepared in Example 2 and Comparative Examples 1-2. Figure 6 The rate performance of Zn / / Zn symmetric cells assembled from the electrode sheets prepared in Example 2 and Comparative Examples 1-2; Figure 7 The above are charge-discharge curves of Zn / / Zn symmetric cells assembled from the electrode sheets prepared in Example 2 and Comparative Examples 1-2. The test conditions were a current density of 1 mA cm⁻¹. -2 The surface area capacity is 1 mAh cm⁻¹ -2 ; Figure 8 The XRD pattern of the zinc electrode in the Zn / / Zn symmetric cell assembled from the electrode sheets prepared in Example 2 and Comparative Example 1 after cycling. Figure 9 SEM images of zinc electrodes after cycling of Zn / / Zn symmetric cells assembled from the electrode sheets prepared in Example 2 and Comparative Example 1. Detailed Implementation

[0018] Unless otherwise specified, all materials, reagents, and instruments used in the following examples are commercially available. Zinc sulfate heptahydrate (ZnSO4·7H2O, ≥ 99%), N-methylpyrrolidone (NMP, ≥ 99.9%), zinc nitrate hexahydrate (Zn(NO3)2·6H2O, ≥ 99%), N,N-dimethylformamide (DMF, ≥ 99%), triethylamine, stannous chloride dihydrate, and terephthalic acid were purchased from Aladdin Co. Ltd. (China). Polyvinylidene fluoride (PVDF, 99%) was purchased from Shenzhen Kejing Electromechanical Co., Ltd. (China). Zinc foil (100 μm) was purchased from Tengfeng metal Co. Ltd. (China). Example 1

[0019] A method for synthesizing a SnO2 / MOF-5 composite anode material includes the following steps: Step (1): Take zinc nitrate hexahydrate into a reaction flask, add DMF and stir to dissolve, so that the final concentration of zinc nitrate in the reaction flask is 0.090 M; then add terephthalic acid to the solution and stir to dissolve, so that the concentration is 0.030 M; then add triethylamine and stir to dissolve, so that the concentration is 0.125 M; finally add stannous chloride dihydrate and stir to dissolve, so that the concentration is 0.030 M. Transfer the above mixed solution to a reaction vessel, seal and heat to 110°C, and keep at this temperature for 12 h.

[0020] In step (2), after the reaction was completed and the mixture was naturally cooled to room temperature, the solid was separated from the mixture by centrifugation and the sample was washed with DMF and ethanol. The solid was dried in a vacuum environment at 60°C for 10 h to obtain SnO2 / MOF-5 (1:3) powder.

[0021] Example 2

[0022] A method for synthesizing a SnO2 / MOF-5 composite anode material includes the following steps: Step (1): Zinc nitrate hexahydrate was placed in a reaction flask, and DMF was added and stirred to dissolve it, bringing the final concentration of zinc nitrate in the reaction flask to 0.090 M. Then, terephthalic acid was added to the solution and stirred to dissolve it, bringing the concentration to 0.030 M. Subsequently, triethylamine was added and stirred to dissolve it, bringing the concentration to 0.125 M. Finally, stannous chloride dihydrate was added and stirred to dissolve it, bringing the concentration to 0.015 M. The above mixed solution was transferred to a reaction vessel, sealed, and heated to 110°C, and kept at this temperature for 12 h.

[0023] In step (2), after the reaction was completed and the mixture was naturally cooled to room temperature, the solid was separated from the mixture by centrifugation and the sample was washed with DMF and ethanol. The solid was dried in a vacuum environment at 60°C for 10 h to obtain SnO2 / MOF-5 (1:6) powder.

[0024] Example 3

[0025] A method for synthesizing a SnO2 / MOF-5 composite anode material includes the following steps: Step (1): Zinc nitrate hexahydrate was placed in a reaction flask, and DMF was added and stirred to dissolve it, bringing the final concentration of zinc nitrate in the reaction flask to 0.090 M. Then, terephthalic acid was added to the solution and stirred to dissolve it, bringing the concentration to 0.030 M. Subsequently, triethylamine was added and stirred to dissolve it, bringing the concentration to 0.125 M. Finally, stannous chloride dihydrate was added and stirred to dissolve it, bringing the concentration to 0.010 M. The above mixed solution was transferred to a reaction vessel, sealed, and heated to 110°C, and kept at this temperature for 12 h.

[0026] In step (2), after the reaction was completed and the mixture was naturally cooled to room temperature, the solid was separated from the mixture by centrifugation and the sample was washed with DMF and ethanol. The solid was dried in a vacuum environment at 60°C for 10 h to obtain SnO2 / MOF-5 (1:9) powder.

[0027] Comparative Example 1 A method for preparing an aqueous zinc-ion battery anode includes the following steps: Take a clean zinc sheet, first use 3000-grit sandpaper to polish one side of the zinc sheet until it is shiny, then use 10000-grit sandpaper to polish it, and finally use ethanol to clean the surface of the zinc sheet.

[0028] Comparative Example 2 (Synthesis of MOF-5 without SnO2 doping) A method for synthesizing an aqueous zinc-ion battery anode material includes the following steps: Step (1): Take zinc nitrate hexahydrate into a reaction flask, add DMF and stir to dissolve, so that the final concentration of zinc nitrate in the reaction flask is 0.090 M; then add terephthalic acid to the solution and stir to dissolve, so that the concentration is 0.030 M; finally add triethylamine and stir to dissolve, so that the concentration is 0.125 M. Transfer the above mixed solution to a reaction vessel, seal and heat to 110 °C, and keep at this temperature for 12 h.

[0029] In step (2), after the reaction was completed and the mixture was allowed to cool naturally to room temperature, the solid was separated from the mixture by centrifugation, and the sample was washed with DMF and ethanol. The solid was dried in a vacuum environment at 60 °C for 10 h to obtain MOF-5 powder.

[0030] Application Examples: The powders obtained in Examples 1-3 and Comparative Example 2 were used as active materials and ground thoroughly with PVDF at a mass ratio of 9:1. An appropriate amount of NMP was added and stirred. The mixture was then coated onto the surface of a clean zinc sheet, dried at 60°C for 12 hours, and then sliced.

[0031] The performance of the negative electrodes prepared in Examples 1-3 and Comparative Examples 1-2 was tested. Battery performance testing was conducted using the Blue Battery Testing System and Chenhua Electrochemical Workstation. The physical properties of the zinc electrode surface after long-cycle testing were characterized using scanning electron microscopy and X-ray diffraction. To test the electrochemical performance of the negative electrodes, Zn / / Zn symmetric cells and Zn / / Cu asymmetric cells were used, employing the negative electrode sheets prepared in the above examples and comparative examples, with glass fiber separators, and assembled into CR2032 button cells for electrochemical performance testing. To characterize the morphology and material composition of the electrode surface after cycling, the battery electrodes after long-cycle testing were analyzed using scanning electron microscopy and X-ray diffraction.

[0032] Figure 1 The XRD patterns of the powder materials prepared in Examples 1-3 and Comparative Example 2 are shown. The test results show that the diffraction peaks of SnO2 / MOF-5 materials with different SnO2 contents are consistent with those of MOF-5, with characteristic diffraction peaks of MOF-5 observed at positions such as 6.8°, 9.7°, and 13.7°. The intensity of the (200) crystal plane gradually decreases with increasing SnO2 content. Furthermore, the peak at 6.9° shifts to lower diffraction angles, indicating that the addition of SnO2 leads to an expansion of the lattice structure of MOF-5.

[0033] Figure 2 Scanning electron microscope (SEM) images of the powder materials prepared in Examples 1-3. The test results show that the SnO2 / MOF-5 materials with different SnO2 contents in Examples 1-3 (…) Figure 2 The morphology of (a)-(c) shows that the SnO2 / MOF-5 (1:6) material ( Figure 2 (b) has a regular hexahedral structure with tin dioxide attached to the surface of MOF-5, while SnO2 / MOF-5 materials with other SnO2 contents all exhibit irregular morphologies.

[0034] Figure 3 This is a transmission electron microscope (TEM) image of the powder material prepared in Example 2. The test results show that SnO2 is uniformly attached to the surface of MOF-5.

[0035] Figure 4The images show the EIS diagrams of Zn / / Zn symmetric cells assembled from the electrode sheets prepared in Examples 1-3 and Comparative Examples 1-2 before cycling. The test results show that the charge transfer resistance of the zinc anode after MOF-5 modification is significantly reduced. With the increase of SnO2 content in SnO2 / MOF-5, the charge transfer resistance is much lower than that of bare zinc and MOF-5 modified zinc anodes. The SnO2 / MOF-5 (1:6) sample exhibits the lowest charge transfer resistance. The moderate SnO2 content introduces excellent conductive sites such as Sn-O bonds, improving the overall ionic conductivity of the material, without severely damaging the main framework structure of MOF-5, thus providing both efficient ion transport channels and maintaining a good physical barrier effect.

[0036] Figure 5 Coulombic efficiency plots of Zn / / Cu asymmetric cells assembled from the electrode sheets prepared in Example 2 and Comparative Examples 1-2. Test conditions were a current density of 1 mA cm⁻¹. -2 Area capacity 1 mAh cm -2 Test results show that the half-cell assembled using the zinc anode modified with SnO2 / MOF-5 (1:6) can stably cycle for more than 1500 cycles, which is far greater than the half-cell assembled with bare zinc (200 cycles) obtained in Comparative Document 1 and MOF-5@Zn (750 cycles) obtained in Comparative Document 2, and the average coulombic efficiency is as high as 99.18%.

[0037] Figure 6 The graphs show the rate performance test results of Zn / / Zn symmetric cells assembled from the electrode sheets prepared in Example 2 and Comparative Examples 1-2. The current density test range is 1~5 mA cm⁻¹. -2 (The increase is 1 mA cm) -2 During the test, the battery underwent 10 charge-discharge cycles at different current densities. After the test, the battery maintained a current density of 1 mA cm⁻¹. -2 Long-cycle charge-discharge tests were conducted at a current density of [value missing]. The test results show that the battery assembled using the zinc anode modified with SnO2 / MOF-5 (1:6) exhibits a smaller polarization voltage and better stability.

[0038] Figure 7 The coulombic efficiency plots are shown for the Zn / / Cu asymmetric cells assembled from the electrode sheets prepared in Example 2 and Comparative Examples 1-2. The test conditions were a current density of 1 mA cm⁻¹. -2 Area capacity 1 mAh cm -2Test results show that the symmetric cell assembled with the SnO2 / MOF-5 (1:6) modified zinc anode can be stably cycled for 1200 h, which is much longer than the symmetric cell assembled with bare zinc (250 h) obtained in Comparative Document 1 and MOF-5@Zn (510 h) obtained in Comparative Document 2.

[0039] Figure 8 The XRD patterns of Example 2 and Comparative Example 1 after zinc metal dissolution / deposition electrochemical testing are shown. The test results indicate that the bare zinc electrode in Comparative Example 1, after cycling, exhibits a characteristic peak of basic zinc sulfate at position 8.5°. Furthermore, a symmetrical cell assembled using the SnO2 / MOF-5 (1:6) modified zinc electrode from Example 2 achieves a current density of 1 mA cm⁻¹. -2 Area capacity 1 mAh cm -2 After 50 cycles, the peak intensity of the (002) crystal plane was much higher than that of the symmetric cell assembled with bare zinc after cycling at the same current, indicating that SnO2 / MOF-5 can induce zinc metal to preferentially deposit along the (002) crystal plane, reducing the irreversibility during cycling.

[0040] Figure 9 SEM images of zinc metal dissolution / deposition electrochemical tests performed in Examples 2 and 1. The test results show that zinc is uniformly deposited on the zinc sheet surface using the SnO2 / MOF-5 (1:6) modified zinc anode. Figure 9 (a) Zinc dendrites formed on the surface of the bare zinc electrode after cycling. Figure 9 (b) The above results all demonstrate that the zinc anode modified with SnO2 / MOF-5 (1:6) inhibits the production of basic zinc sulfate to a certain extent, maintains the stability of the reversible reaction, improves the utilization rate of zinc during the zinc plating / dezincification process, and enhances the cycle stability of the battery.

Claims

1. A SnO2 / MOF-5 composite anode material, characterized in that, It includes metal-organic framework material MOF-5 and zinc-loving metal oxide SnO2, with SnO2 attached to the surface of MOF-5.

2. The preparation method of the SnO2 / MOF-5 composite anode material as described in claim 1, characterized in that, Includes the following steps: Zinc nitrate hexahydrate was placed in a reaction flask, DMF was added and stirred to dissolve it. Then, terephthalic acid, triethylamine, and stannous chloride dihydrate were added to the solution in sequence and stirred to dissolve. The mixture was then transferred to a reaction vessel, sealed and heated. After the reaction was completed, the mixture was allowed to cool to room temperature naturally. The solid was then separated from the mixture by centrifugation, and the sample was washed with DMF and ethanol and dried under vacuum to obtain SnO2 / MOF-5 powder.

3. The preparation method according to claim 2, characterized in that, The molar ratio of stannous chloride dihydrate to zinc nitrate hexahydrate is 1:3~9; the molar ratio of zinc nitrate hexahydrate to terephthalic acid is 3:1; and the molar ratio of zinc nitrate hexahydrate to triethylamine is 0.72:

1. In the mixed solution, the concentration of zinc nitrate hexahydrate is 0.090 M, the concentration of terephthalic acid is 0.030 M, and the concentration of triethylamine is 0.125 M.

4. The preparation method according to claim 3, characterized in that, The molar ratio of stannous chloride dihydrate to zinc nitrate hexahydrate is 1:

6.

5. The preparation method according to claim 2, characterized in that, The temperature of the sealed heating is 80~150℃, and the heating time is 12~24 h.

6. The preparation method according to claim 2, characterized in that, The vacuum drying temperature is 40~100℃, and the drying time is 6~24 h.

7. The application of the SnO2 / MOF-5 composite anode material as described in claim 1 in aqueous zinc-ion batteries.

8. The application as described in claim 7, characterized in that, The steps are as follows: mix SnO2 / MOF-5 composite anode material with PVDF in proportion and grind thoroughly. Then add NMP and stir to form a suspension. Then use a scraper to evenly coat the suspension onto the surface of a clean zinc sheet. After drying and waiting for the solvent to evaporate, slice the sheet.

9. The application as described in claim 8, characterized in that, The mass ratio of SnO2 / MOF-5 to PVDF is (7~9):(3~1); the concentration of the SnO2 / MOF-5 composite anode material in NMP is 0.650~0.750 g / mL; the stirring time after adding NMP is 6 h; the drying conditions are: vacuum drying at 50~100 ℃ for 6~24 h.

10. The application as described in claim 9, characterized in that, The mass ratio of SnO2 / MOF-5 to PVDF is 9:1.

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