Preparation of MOF-5W materials and their application in improving the performance of aqueous zinc-ion batteries via pore confinement effect

Abstract

The invention proposes the preparation of MOF-5W material and the application of the material in improving the performance of aqueous zinc ion batteries through pore restriction effect, belonging to the technical field of electrochemistry. The invention prepares a MOF-5W material with a long rice morphology by a solvothermal method, the MOF-5W material is mixed with PVDF and NMP and ground, and then coated on a zinc foil, and the MOF-5W@Zn pole piece is prepared after drying and stamping. When the MOF-5W@Zn pole piece is used as a zinc negative electrode, the side reaction on the zinc negative electrode and the formation of zinc dendrites are effectively alleviated, thereby improving the reversibility of the zinc negative electrode, and the aqueous zinc ion battery assembled with the pole piece has good cycle stability and safety.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemistry, and in particular relates to the preparation of MOF-5W material and the application of the MOF-5W material in improving the performance of aqueous zinc ion batteries through a pore restriction effect. Background Art

[0002] Aqueous zinc-ion batteries have attracted widespread attention in the field of energy storage due to their low cost, high safety, and eco-friendliness. Metallic zinc has a high theoretical specific capacity (820 mAh g -1 ), low redox potential (-0.76V relative to standard hydrogen electrode), and excellent stability in air and water, making it one of the most promising energy storage materials for the next generation. However, the practical application of aqueous zinc-ion batteries still faces many problems, such as the growth of zinc dendrites and hydrogen evolution reaction. In order to solve these problems, various interface engineering studies have emerged, including zinc anode surface modification and electrolyte optimization strategies. Among them, the use of coating materials to construct a protective layer, the physical regulation of the internal channel size or the chemical regulation of the coordination structure can effectively guide the Zn 2+ Uniform deposition and limiting direct contact between free water and the Zn negative electrode, such as layered inorganic oxides, organic polymers and ordered porous crystal frameworks. Among them, metal-organic frameworks (MOFs) with ordered pore structures have many advantages for stabilizing the zinc negative electrode. Liu et al. mixed UIO-66 and PVDF and coated them on zinc foil to prepare MOF-PVDF zinc negative electrode. This MOF coating can form a nano-wetting effect with the electrolyte to form a zinc-philic interface. The symmetric battery composed of MOF-PVDF zinc negative electrode was 3mA·cm -2 Current density and 0.5 mAh cm -2 Wang et al. took advantage of the porosity and high hydrogen evolution overpotential of ZIF-8 and used it as the main material for the zinc negative electrode surface coating. The experiment showed that the zinc-iodine rechargeable battery using Zn@ZIF-8-500 as the negative electrode could stably cycle 500 times at 2.0A·g -1 It has a cycle life of 1600 cycles and excellent rate capability at a current density of 1.58kV.

[0003] However, the protective layers of MOF particles and polymer binder coatings reported are usually macroporous. There are actually two types of MOF channels in the coating that provide molecular migration. The ordered channels in the MOF crystals can make [Zn(H2O)6] 2+ Desolvation, directing Zn 2+ Uniform deposition, while the disordered spatial structure formed between MOF particles and polymer binder will expose and corrode the Zn negative electrode surface. Therefore, the MOF channel size is the key factor determining [Zn(H2O)6] 2+The key factor of desolvation behavior, which in turn affects the Zn 2+ However, in the past, MOF channel size has not been studied in depth. Therefore, a MOF material with a suitable channel size is studied to regulate the Zn 2+ The solvation structure is essential. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a preparation method of MOF-5W material and its application in improving the performance of aqueous zinc ion batteries through pore restriction effect. The present invention utilizes the size restriction effect of the metal organic framework channel of MOF-5W material to protect the zinc negative electrode, thereby improving the problems of zinc dendrite growth and hydrogen evolution reaction on the zinc surface during battery cycling. The present invention synthesizes pure phase MOF-5W by solvothermal method and coats it on zinc foil by grinding. MOF-5W material (size channel is ) can homogenize the flux of zinc ions, making [Zn(H2O)6] 2+ The MOF-5W surface activated sites can further accelerate the ion transfer and desolvation of hydrated zinc ions. The migration mechanism on the coating effectively alleviates the side reactions and the formation of zinc dendrites on the zinc anode, thereby improving the reversibility of the zinc anode.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a MOF-5W material comprises taking terephthalic acid and zinc acetate dihydrate as starting materials and preparing MOF-5W by a solvent thermal method.

[0007] Preferably, the preparation method of the MOF-5W material comprises the following steps:

[0008] Add terephthalic acid and sodium hydroxide to a mixed solution of deionized water and N,N-dimethylformamide (DMF), and stir evenly to prepare solution A;

[0009] Add zinc acetate dihydrate to a mixed solution of deionized water and DMF, and stir evenly to prepare solution B;

[0010] The solution A and the solution B are mixed and stirred in a water bath. After the stirring is completed, the solution is allowed to stand in the water bath. Finally, the product is washed and filtered using DMF and deionized water. The filtered product is freeze-dried to obtain MOF-5W powder. The MOF-5W powder is activated to obtain MOF-5W material.

[0011] Preferably, in the method for preparing the MOF-5W material, when preparing solution A, the mass ratio of terephthalic acid to sodium hydroxide is (2:3) to (5:1).

[0012] Preferably, in the method for preparing the MOF-5W material, when preparing solution B, the mass ratio of zinc acetate dihydrate to deionized water is (1:2) to (1:4).

[0013] Preferably, in the method for preparing the MOF-5W material, when preparing solution A and solution B, the volume ratio of deionized water to N,N-dimethylformamide is (1:2) to (2:1).

[0014] Preferably, in the preparation method of the MOF-5W material, the temperature of the water bath during stirring is 30 to 100° C., and the standing time of the water bath is 1 to 12 hours.

[0015] Preferably, in the preparation method of the MOF-5W material, the activation refers to activating the MOF-5W powder at 200° C. under normal pressure for 2 h.

[0016] A MOF-5W material prepared by the above method has a long rice morphology and a channel size of

[0017] The present invention also provides the use of the MOF-5W material in alleviating side reactions on a zinc negative electrode and inhibiting the formation of zinc dendrites.

[0018] Preferably, in the application of the MOF-5W material in alleviating side reactions on the zinc negative electrode and inhibiting the formation of zinc dendrites, the specific application method is: after mixing the MOF-5W material with polyvinylidene fluoride (PVDF), 1-methyl-2-pyrrolidone (NMP) is added for stirring, and after the mixture is stirred evenly, it is coated on a zinc foil, and dried at 60°C in vacuum for 6 hours, and a MOF-5W@Zn electrode sheet is prepared using a puncher (the diameter of the puncher used is 10 to 14 mm). The prepared MOF-5W@Zn electrode sheet can effectively alleviate the side reactions on the zinc negative electrode and inhibit the formation of zinc dendrites when used as a zinc negative electrode.

[0019] The present invention also provides the application of the MOF-5W material in improving the performance of aqueous zinc ion batteries through the pore restriction effect. MOF-5W is a partial hydrolysis product of MOF-5. MOF-5 will be converted into MOF-5W or other substances when exposed to humid air, but MOF-5W will not continue to convert. It has higher stability than MOF-5. After being stored for a long time, its XRD still has good crystallinity and purity, but the XRD of MOF-5 will change. Therefore, MOF-5W is another substance different from MOF-5, and has better crystallinity and purity.

[0020] Preferably, in the application of MOF-5W material in improving the cycle performance of zinc battery, the MOF-5W@Zn pole piece prepared by MOF-5W material is used as the negative electrode of zinc battery. For example, the MOF-5W@Zn pole piece prepared by MOF-5W material can be used as the negative electrode, and zinc sulfate solution (ZnSO4) can be used as the electrolyte to assemble a zinc ion battery, the concentration of the electrolyte is 0.5-3 mol / L, and the current density is 0.5-40 mA cm -2 The above zinc ion battery has good cycle stability and safety. The symmetrical battery assembled from the MOF-5W@Zn electrode prepared from MOF-5W material is 10mA·cm -2 Ultra-high current density and 10 mAh cm -2 Under the ultra-high surface capacity, the cycle lasted for more than 1100h without short circuit, which shows that the negative electrode has a good market application prospect. The above ZnSO4 electrolyte can also be replaced by Zn(CF3SO3)2 electrolyte or ZnCl2 electrolyte.

[0021] The MOF-5W material of the present invention can effectively reduce the contact angle between the zinc sulfate electrolyte and the zinc foil, thereby increasing the contact area between the electrolyte and the negative electrode of the battery. MOF-5W can induce zinc ions to be uniformly deposited on the surface of the pole piece during the cycle process to form a stable zinc negative electrode.

[0022] The present invention also provides the use of the MOF-5W material in preparing an aqueous zinc ion battery.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] (1) The raw material preparation of the present invention is simple and the preparation cost is low. The prepared MOF-5W material is coated on zinc foil as a coating to prepare a pole piece, and the assembled battery has good cycle stability. MOF-5W can effectively reduce the contact angle between zinc sulfate electrolyte and zinc foil, thereby increasing the contact area between the electrolyte and the negative electrode of the battery. MOF-5W can induce zinc ions to be uniformly deposited on the surface of the pole piece during the cycle to form a stable zinc negative electrode.

[0025] (2) The MOF-5W material prepared by the present invention can be used as a protective layer to homogenize the flux of zinc ions, making [Zn(H2O)6] 2+ The desolvation occurs spontaneously. In addition, the activated sites on the surface of MOF-5W can further accelerate the ion transfer and desolvation of hydrated zinc ions. The migration mechanism effectively alleviates the side reactions and the formation of zinc dendrites on the zinc anode, thereby improving the reversibility of the zinc anode.

[0026] (3) The method of the present invention is simple to prepare. The zinc ion battery negative electrode prepared by the method of the present invention has good cycle stability and safety. The symmetrical battery has a high cycle stability at 10 mA cm -2 Ultra-high current density and 10 mAh cm -2 With ultra-high surface capacity, the cycle lasted for more than 1100 hours without short circuit, which shows that the negative electrode has good market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0028] Figure 1 XRD patterns of MOF-5W obtained in Example 1 (a) and ZIF-7 and MOF-808 obtained in Comparative Example 1 (c) and Comparative Example 2 (b), respectively;

[0029] Figure 2 SEM images of MOF-5W prepared in Example 1(a) and ZIF-7 and MOF-808 obtained in Comparative Example 1(c) and Comparative Example 2(b), respectively;

[0030] Figure 3 Cross-sectional scans of MOF-5W prepared in Example 1 (a) and ZIF-7 and MOF-808 obtained in Comparative Example 1 (c) and Comparative Example 2 (b), respectively;

[0031] Figure 4 The wettability test of bare Zn (Bare Zn) and zinc negative electrode coated with MOF material obtained in Example 1 and Comparative Example 1 and Comparative Example 2 to 2M ZnSO4 electrolyte;

[0032] Figure 5 The symmetric cell composed of MOF-5W@Zn prepared in Example 1 and bare zinc was charged in 2M ZnSO4 electrolyte at 10 mA cm -2 The current density is 10 mAh cm -2 Long cycle test results under the surface capacity;

[0033] Figure 6 Symmetrical cells assembled with MOF-5W@Zn prepared in Example 1, ZIF-7@Zn obtained in Comparative Examples 1 and 2, MOF-808@Zn and bare zinc were tested in 2M ZnSO4 electrolyte at 1 mA·cm -2 Current density, 1 mAh cm -2 Comparison chart of the cycle performance of the surface capacity;

[0034] Figure 7Symmetrical cells assembled with MOF-5W@Zn prepared in Example 1, ZIF-7@Zn obtained in Comparative Examples 1 and 2, MOF-808@Zn and bare zinc were charged in 2M ZnSO4 electrolyte at 1 mAh·cm -2 Surface capacity and rate performance at different current densities;

[0035] Figure 8 Coulombic efficiency (CE) test results of the half-cells assembled using MOF-5W@Zn prepared in Example 1, ZIF-7@Zn and MOF-808@Zn obtained in Comparative Examples 1 and 2, respectively, as well as bare zinc as the negative electrode and Ti foil as the positive electrode in 2M ZnSO4 electrolyte;

[0036] Fig. 9 The Tafel curve test results of the three-electrode system with MOF-5W@Zn prepared in Example 1, ZIF-7@Zn and MOF-808@Zn obtained in Comparative Examples 1 and 2 respectively, and bare zinc as working electrodes, platinum as counter electrodes, and Ag / AgCl as reference electrodes;

[0037] Fig.10 The diffusion of zinc in the symmetric cells assembled with MOF-5W@Zn prepared in Example 1 and ZIF-7@Zn, MOF-808@Zn and bare zinc obtained in Comparative Examples 1 and 2 was tested by the time current method (CA);

[0038] Fig.11 The symmetric cell composed of MOF-5W@Zn prepared in Example 2 and bare zinc was used in 2M ZnSO4 electrolyte at 1 mA cm -2 The current density is 1 mAh cm -2 Comparison of deposition / stripping cycle performance under surface capacity;

[0039] Fig.12 The symmetric cell composed of MOF-5W@Zn prepared in Example 1 and bare zinc was charged in 1M ZnSO4 electrolyte at 5 mA·cm -2 The current density is 5 mAh cm -2 Comparison of deposition / stripping cycle performance under surface capacity;

[0040] Fig.13 The symmetric cell composed of MOF-5W@Zn prepared in Example 1 and bare zinc was charged in 2M Zn(CF3SO3)2 electrolyte at 15 mA·cm -2 The current density is 15 mAh cm -2 Comparison of deposition / stripping cycle performance under surface capacity;

[0041] Fig.14The symmetric cell composed of MOF-5W@Zn prepared in Example 3 and bare zinc was charged in 2M ZnSO4 electrolyte at 40 mA cm -2 The current density is 1 mAh cm -2 Comparison of deposition / stripping cycle performance under surface capacity;

[0042] Fig.15 The symmetric cell composed of MOF-5W@Zn prepared in Example 1 and bare zinc was charged in 2M ZnSO4 electrolyte at 10 mA cm -2 The current density is 5 mAh cm -2 Comparison of deposition / stripping cycle performance under surface capacity;

[0043] Fig.16 The battery assembled with the unactivated MOF-5W prepared in Comparative Example 3 was charged in 2M ZnSO4 electrolyte at 5 mA cm -2 The current density is 5 mAh cm -2 Comparison of deposition / stripping cycle performance under surface capacity;

[0044] Fig.17 The symmetric cell assembled with MOF-5W@Zn prepared in Example 4 was charged in 2M ZnSO4 electrolyte at 1 mA cm -2 The current density is 1 mAh cm -2 Deposition / stripping cycle performance diagram under the surface capacity;

[0045] Fig.18 The symmetric cell assembled with MOF-5W@Zn prepared in Example 5 was charged in 2M ZnSO4 electrolyte at 5 mA cm -2 The current density is 5 mAh cm -2 Deposition / stripping cycle performance diagram under the surface capacity;

[0046] Fig.19 The symmetric cell assembled with MOF-5W@Zn prepared in Example 6 was charged in 2M ZnSO4 electrolyte at 1 mA cm -2 The current density is 1 mAh cm -2 Deposition / stripping cycle performance diagram under the surface capacity;

[0047] Fig. 20 The electrochemical performance diagram of the MOF-5W@Zn / / NVO flexible battery prepared in the application example, where a is the CV curve of the full battery assembled with bare Zn and MOF-5W@Zn as the negative electrode; b is the CV curve at 0.5 A·g -1The cycling performance of the full battery assembled with bare Zn and MOF-5W@Zn as negative electrodes at a current density of 3 A·g; c is the rate performance of the full battery assembled with bare Zn and MOF-5W@Zn as negative electrodes; d is the rate performance of the MOF-5W@Zn / / NVO flexible battery at a current density of 3 A·g -1 e is the schematic diagram of the internal structure of the MOF-5W@Zn / / NVO flexible battery; f is the initial voltage of the MOF-5W@Zn / / NVO flexible battery; gi are the voltages of the MOF-5W@Zn / / NVO flexible battery in cutting, puncture and folding destructive tests, respectively. DETAILED DESCRIPTION

[0048] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0049] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0050] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0051] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0052] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0053] As introduced in the background technology section, aqueous zinc ion batteries will undergo a cycle due to the Zn 2+The uneven deposition produces dendrites that eventually pierce the separator and cause the battery to short-circuit, and the occurrence of hydrogen evolution reaction will seriously corrode the zinc negative electrode and eventually cause battery damage.

[0054] Based on this, the purpose of the present invention is to provide a method for using a simple solvent thermal synthesis raw material and a slurry coating method to prepare a zinc negative electrode that can effectively inhibit zinc dendrites and hydrogen evolution reactions. A MOF-5W material with a long rice morphology was synthesized by a solvent thermal method, and MOF-5W, polyvinylidene fluoride (PVDF) and 1-methyl-2-pyrrolidone (NMP) were ground and coated on zinc foil in different proportions, and then dried and stamped to prepare a suitable MOF-5W@Zn electrode. The composition ratio of MOF-5W on the surface of Zn foil can be controlled by adjusting the ratio of MOF-5W, PVDF and NMP added; the thickness of the MOF-5W coating on the surface of Zn foil can be controlled by adjusting the height of the scraper.

[0055] The test materials used in the examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels.

[0056] Normal pressure in the embodiments of the present invention refers to 1 atmosphere, and room temperature refers to 25±2°C.

[0057] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0058] Comparative Example 1

[0059] 0.528 g of zinc acetate dihydrate (Zn(CH3COO)2) and 1.180 g of benzimidazole were mixed and then completely dissolved in deionized water (300 mL). After stirring for 3 h, a white ZIF-7 precipitate was obtained after standing for 1 day. The ZIF-7 precipitate was carefully washed three times with ethanol and deionized water, dispersed in ethanol for 3 days and centrifuged. After that, the ZIF-7 powder was dried at 80 ° C for 12 h, the absorbed solvent was removed, and it was transferred to a vacuum oven and further activated at 180 ° C overnight to obtain activated ZIF-7.

[0060] Take 80 mg of activated ZIF-7 and 20 mg of polyvinylidene fluoride (PVDF) powder and add them to 1 mL of 1-methyl-2-pyrrolidone (NMP), grind and stir at room temperature for 8 hours to obtain a metal zinc negative electrode coating slurry. The prepared metal zinc negative electrode coating slurry is coated on zinc foil with a coating thickness of 10 microns, and vacuum dried at 60°C for 6 hours to obtain a ZIF-7@Zn electrode.

[0061] The ZIF-7@Zn electrodes were used as positive and negative electrodes to assemble a symmetrical battery. The electrolyte used was 2 mol L- 1 ZnSO4 solution, at 1 mA cm -2 The current density is 1 mAh cm -2 The deposition / stripping cycle performance test was carried out at the surface capacity.

[0062] Comparative Example 2

[0063] 0.648 g of ZrOCl2·8H2O and 0.140 g of H3BTC were added to a mixed solvent of DMF / CH2O2 (30 mL / 30 mL) and reacted at 120°C for 24 h in a 100 mL polytetrafluoroethylene reactor. The obtained precipitate was washed with DMF and methanol and dried in an oven at 80°C for 10 h to obtain MOF-808 powder, which was then soaked in anhydrous acetone for 3 days and finally dried in vacuum at 150°C for 24 h to obtain activated MOF-808.

[0064] Take 80 mg of activated MOF-808 and 20 mg of PVDF powder, add them to 1 mL of NMP, grind and stir at room temperature for 8 hours to obtain a metal zinc negative electrode coating slurry. The prepared metal zinc negative electrode coating slurry is coated on zinc foil with a coating thickness of 10 microns, and vacuum dried at 60°C for 6 hours to obtain a MOF-808@Zn electrode.

[0065] The MOF-808@Zn electrodes were used as positive and negative electrodes to assemble a symmetrical battery. The electrolyte used was 2 molL -1 ZnSO4 solution, at 1 mA cm -2 The current density is 1 mAh cm -2 The deposition / stripping cycle performance test was carried out at the surface capacity.

[0066] Example 1

[0067] 1.329g of terephthalic acid and 0.68g of sodium hydroxide were added to a mixed solution of 10mL of deionized water and 10mL of N,N-dimethylformamide (DMF), and stirred to obtain solution A. 3.512g of zinc acetate dihydrate was added to a mixed solution of 10mL of deionized water and 10mL of DMF, and stirred to obtain solution B. Solutions A and B were mixed and stirred in a water bath at 70°C for 10min. After stirring, the mixture was allowed to stand in a water bath at 70°C for 2 hours. Finally, the product was washed 3 times with N,N-dimethylformamide and deionized water respectively and filtered. The filtered product was placed in a freeze dryer and dried for 24h to obtain the reaction product MOF-5W powder. The MOF-5W powder was activated at 200°C for 2h under normal pressure to obtain activated MOF-5W. Take 80 mg of activated MOF-5W and 20 mg of polyvinylidene fluoride (PVDF) powder and add them to 1 mL of 1-methyl-2-pyrrolidone (NMP), grind and stir at room temperature for 8 hours to obtain a metal zinc negative electrode coating slurry. The prepared metal zinc negative electrode coating slurry is coated on a zinc foil with a 200-micron scraper. The thickness of the MOF-5W coating in this embodiment is 10 microns. It is vacuum dried at 60°C for 6 hours to obtain a MOF-5W@Zn pole piece.

[0068] The MOF-5W@Zn electrode of Example 1 and bare zinc (Zn) were assembled into symmetrical cells, and the electrolyte used was 2 mol L -1 (2M) ZnSO4 solution, at 1 mA cm -2 The current density is 1 mAh cm -2 The deposition / stripping cycle performance test was carried out at the surface capacity.

[0069] Figure 1 The XRD spectra of MOF-5W obtained in Example 1 (a) and ZIF-7 and MOF-808 obtained in Comparative Example 1 (c) and Comparative Example 2 (b), respectively, show that the obtained materials have good crystallinity and correspond to the reported XRD peaks. Figure 1The references in a are H. Yang, Z. Chang, Y. Qiao, H. Deng, X. Mu, P. He, H. Zhou, Angew. Chem. Int. Ed. 2020, 59, 9377-9381 (ZIF-7); b are H. Furukawa, F. Gandara, YB Zhang, J. Jiang, WL Queen, MR Hudson, OM Yaghi, J. Am. Chem. Soc. 2014, 136, 4369-4381 (MOF-808); c are L. Lu, C. Hu, Y. Zhu, H. Zhang, R. Li, Y. Xing, Cellulose 2018, 25, 4223-4238 (MOF-5W).

[0070] Figure 2 The SEM images of MOF-5W prepared in Example 1 (a) and ZIF-7 and MOF-808 obtained in Comparative Example 1 (c) and Comparative Example 2 (b) respectively show that the prepared samples of the example and the comparative example have good uniformity. MOF-5W has a long rice morphology and a channel size of ZIF-7 has a platelet-like morphology with a channel size of 2.94A; MOF-808 has a spherical morphology with a channel size of 10.1A.

[0071] Figure 3 From the cross-sectional scans of MOF-5W obtained in Example 1(a) and ZIF-7 and MOF-808 obtained in Comparative Example 1(c) and Comparative Example 2(b), respectively, it can be seen that the three MOF coatings constructed by MOF particles and polymer binders on the Zn negative electrode show a similar thickness of 10 μm.

[0072] Figure 4 The wettability of bare Zn (Bare Zn) and zinc negative electrode coated with MOF materials obtained in Example 1 and Comparative Examples 1 and 2 to 2MZnSO4 electrolyte was tested. The contact angle of MOF-5W with ZnSO4 electrolyte was 26.2°, which was much lower than that of the comparative material and bare zinc. This result shows that the MOF-5W material has a suitable molecular channel size and contains free carboxyl groups in its crystal structure, which improves the compatibility of the electrolyte and the electrode interface, and is beneficial to the transport of Zn ions and the formation of zinc-philic interfaces.

[0073] Figure 5 The symmetric cell composed of MOF-5W@Zn prepared in Example 1 and bare zinc was charged in 2M ZnSO4 electrolyte at 10 mA cm -2 Current density, 10 mAh cm -2According to the long cycle test results under the surface capacity, MOF-5W@Zn can stably cycle for more than 1100 hours under this condition, far exceeding the cycle life of bare zinc.

[0074] Figure 6 Symmetrical cells assembled with MOF-5W@Zn prepared in Example 1, ZIF-7@Zn obtained in Comparative Examples 1 and 2, MOF-808@Zn and bare zinc were charged in 2M ZnSO4 electrolyte at 1 mA·cm -2 Current density, 1 mAh cm -2 The cycle performance comparison chart of the surface capacity shows that the cycle life of the MOF-5W@Zn symmetrical battery is as long as 2500h, which is much better than ZIF-7@Zn, MOF-808@Zn and bare zinc.

[0075] Figure 7 Symmetrical cells assembled with MOF-5W@Zn prepared in Example 1, ZIF-7@Zn obtained in Comparative Examples 1 and 2, MOF-808@Zn and bare zinc were tested in 2M ZnSO4 electrolyte at 1 mAh cm -2 The surface capacity and rate performance at different current densities show that MOF-5W material exhibits excellent rate performance at up to 10 mA cm -2 The stable cycle can still be maintained at a current density of 2.

[0076] Figure 8 The MOF-5W@Zn prepared in Example 1 and the ZIF-7@Zn and MOF-808@Zn obtained in Comparative Examples 1 and 2, respectively, and bare zinc were used as negative electrodes, and Ti foil was used as positive electrodes. The assembled half-cells were subjected to Coulombic efficiency (CE) tests in 2M ZnSO4 electrolyte. Due to severe side reactions and dendrite growth, the Coulombic efficiency of bare zinc was the most unstable and the reversibility was the worst. In contrast, the MOF-5W@Zn negative electrode could stably cycle for 600 cycles at a higher Coulombic efficiency.

[0077] Fig. 9 Tafel curve test was carried out on the three-electrode system with MOF-5W@Zn prepared in Example 1, ZIF-7@Zn and MOF-808@Zn obtained in Comparative Examples 1 and 2 respectively, and bare zinc as working electrodes, platinum sheet as counter electrode, and Ag / AgCl as reference electrode. Compared with the bare zinc foil, the zinc foil coated with MOF material has less chance of being directly exposed to the water environment, and shows smaller corrosion potential and corrosion current. In particular, the improvement of corrosion resistance of MOF-5W material is most significant.

[0078] Fig.10The diffusion of zinc in the symmetrical battery assembled with MOF-5W@Zn prepared in Example 1, ZIF-7@Zn, MOF-808@Zn obtained in Comparative Examples 1 and 2, and bare zinc was tested by time current method (CA). For the symmetrical battery assembled with bare zinc anode, the current density continued to increase within 50s, indicating that Zn 2+ The two-dimensional diffusion is very serious. After the MOF layer is coated, it undergoes a short two-dimensional diffusion and then turns into three-dimensional diffusion. At the same time, compared with the ZIF-7 and MOF-808 layers, the MOF-5W@Zn layer has a lower diffusion current and a better ability to convert diffusion behavior, which indicates that the surface of zinc deposition is more uniform under the guidance of the MOF-5W coating.

[0079] The MOF-5W@Zn electrode of Example 1 and bare Zn were assembled into symmetrical cells and charged in 1M ZnSO4 electrolyte at 5 mA cm -2 The current density is 5 mAh cm -2 The deposition / stripping cycle performance was tested under the surface capacity of , and the deposition / stripping cycle performance comparison chart is shown in Fig.12 It can be seen that when the electrolyte concentration decreases, the MOF-5W coating can still effectively protect the zinc negative electrode, with a cycle life of up to 1100 hours, far exceeding that of bare zinc under the same test conditions.

[0080] The MOF-5W@Zn electrode of Example 1 and bare Zn were assembled into symmetrical cells and charged in 2M Zn(CF3SO3)2 electrolyte at 15 mA cm -2 The current density is 15 mAh cm -2 The deposition / stripping cycle performance was tested under the surface capacity of , and the deposition / stripping cycle performance comparison chart is shown in Fig.13 It can be seen that MOF-5W material has a high adaptability to different types of electrolytes and can be effectively cycled for more than 450 hours in Zn(CF3SO3)2 electrolyte, while the battery assembled with bare zinc is damaged after 80 hours of cycling.

[0081] The MOF-5W@Zn electrode of Example 1 and bare Zn were assembled into symmetrical cells and charged in 2M ZnSO4 electrolyte at 10 mA cm -2 The current density is 5 mAh cm -2 The deposition / stripping cycle performance was tested under the surface capacity of Fig.15 It can be seen that by changing the test conditions, the batteries assembled with MOF-5W materials have good cycle performance, high adaptability to different current densities and surface capacities, and are widely used.

[0082] Comparative Example 3 (MOF-5W not activated)

[0083] 1.329g of terephthalic acid and 0.68g of sodium hydroxide were added to a mixed solution of 10mL of deionized water and 10mL of N,N-dimethylformamide (DMF), stirred evenly to form solution A, and then 3.512g of zinc acetate dihydrate was added to a mixed solution of 10mL of deionized water and 10mL of DMF, stirred evenly to form solution B. Solutions A and B were mixed and stirred in a water bath at 70°C for 10min. After stirring, the mixture was allowed to stand in a water bath at 70°C for 2 hours. Finally, the product was washed and filtered with N,N-dimethylformamide and deionized water, and the filtered product was placed in a freeze dryer and dried for 24h to obtain the reaction product MOF-5W powder. 80mg of MOF-5W powder and 20mg of polyvinylidene fluoride (PVDF) powder were taken and added to 1mL of 1-methyl-2-pyrrolidone (NMP), and the metal zinc negative electrode coating slurry was obtained by grinding and stirring at room temperature for 8 hours. The prepared metal zinc negative electrode coating slurry was coated on the zinc foil with a 200 μm scraper (the thickness of the MOF-5W coating was the same as that of the coating in Example 1), and vacuum dried at 60° C. for 6 hours to obtain a MOF-5W@Zn electrode sheet.

[0084] The MOF-5W@Zn electrode of Comparative Example 3 and bare zinc were assembled into symmetrical batteries, and the electrolyte used was 2 molL -1 ZnSO4 solution, at 5 mA cm -2 The current density is 5 mAh cm -2 The deposition / stripping cycle performance test was carried out under the surface capacity of Fig.16 As shown, the experiment found that the modification effect of unactivated MOF-5W on the zinc negative electrode was poor, and the battery was damaged after 170 hours of cycling.

[0085] Example 2

[0086] 1.329g of terephthalic acid and 0.68g of sodium hydroxide were added to a mixed solution of 10mL of deionized water and 10mL of DMF, and stirred evenly to form solution A. Then 3.512g of zinc acetate dihydrate was added to a mixed solution of 10mL of deionized water and 10mL of DMF, and stirred evenly to form solution B. Solutions A and B were mixed and stirred in a water bath at 50°C for 10min. After stirring, the mixture was allowed to stand in a water bath at 50°C for 2 hours. Finally, the product was washed and filtered with N,N-dimethylformamide and deionized water, and the filtered product was placed in a freeze dryer and dried for 24h to obtain the reaction product MOF-5W powder. The MOF-5W powder was activated at 200°C for 2h under normal pressure to obtain activated MOF-5W. The preparation method of MOF-5W@Zn pole piece is the same as that in Example 1.

[0087] The MOF-5W@Zn electrode of Example 2 and bare zinc were assembled into symmetrical cells. -2 The current density is 1 mAh cm -2 The deposition / stripping cycle performance was tested under the surface capacity of , and the deposition / stripping cycle performance comparison chart is shown in Fig.11 , it can be seen that the battery assembled with MOF-5W prepared in a water bath at 50°C can be cycled for more than 900 hours, while bare zinc without coating short-circuit occurs in a shorter time.

[0088] Example 3

[0089] 1.329g of terephthalic acid and 0.68g of sodium hydroxide were added to a mixed solution of 10mL of deionized water and 10mL of DMF, and stirred to form solution A. 3.512g of zinc acetate dihydrate was added to a mixed solution of 10mL of deionized water and 10mL of DMF, and stirred to form solution B. Solutions A and B were mixed and stirred in a water bath at 70°C for 10 minutes. After stirring, the mixture was allowed to stand in a water bath at 70°C for 6 hours. Finally, the product was washed and filtered with N,N-dimethylformamide and deionized water, and the filtered product was placed in a freeze dryer and dried for 24 hours to obtain the reaction product MOF-5W powder. The MOF-5W powder was activated at 200°C for 2 hours under normal pressure to obtain activated MOF-5W. The preparation method of MOF-5W@Zn pole piece is the same as that in Example 1.

[0090] The MOF-5W@Zn sheet prepared in Example 3 and bare zinc were assembled into symmetrical cells and charged in 2M ZnSO4 electrolyte at 40 mA cm -2 The current density is 1 mAh cm -2 The deposition / stripping cycle performance was tested under the surface capacity of Fig.14 It can be seen that the preparation time cost of MOF-5W is low, and the experimental results of MOF-5W are not affected within the static time range specified by the present invention. The battery performance tested under the above conditions is better than that of bare zinc.

[0091] Example 4

[0092] 2.04g of terephthalic acid and 0.68g of sodium hydroxide were added to a mixed solution of 10mL of deionized water and 10mL of N,N-dimethylformamide (DMF), stirred evenly to form solution A, and then 3.512g of zinc acetate dihydrate was added to a mixed solution of 10mL of deionized water and 10mL of DMF, stirred evenly to form solution B. Solutions A and B were mixed and stirred in a water bath at 70°C for 10min. After stirring, the mixture was allowed to stand in a water bath at 70°C for 2 hours. Finally, the product was washed 3 times with N,N-dimethylformamide and deionized water respectively and filtered, and the filtered product was placed in a freeze dryer and dried for 24h to obtain the reaction product MOF-5W powder. The MOF-5W powder was activated at 200°C for 2h under normal pressure to obtain activated MOF-5W. The preparation method of MOF-5W@Zn pole piece is the same as that in Example 1.

[0093] The MOF-5W@Zn electrode and bare Zn were assembled into symmetrical batteries, and the electrolyte used was 2 mol L -1 ZnSO4 solution, at 1 mA cm -2 The current density is 1 mAh cm -2 The deposition / stripping cycle performance test was carried out under the surface capacity of Fig.17 As shown, it can be stably cycled for more than 800 hours under this condition, showing good electrochemical performance.

[0094] Example 5

[0095] 1.329g of terephthalic acid and 0.68g of sodium hydroxide were added to a mixed solution of 10mL of deionized water and 10mL of DMF, and stirred to obtain solution A. 2.5g of zinc acetate dihydrate was added to a mixed solution of 10mL of deionized water and 10mL of DMF, and stirred to obtain solution B. Solutions A and B were mixed and stirred in a water bath at 30°C for 10min. After stirring, the mixture was allowed to stand in a water bath at 30°C for 2 hours. Finally, the product was washed 3 times with N,N-dimethylformamide and deionized water respectively and filtered, and the filtered product was placed in a freeze dryer and dried for 24h to obtain the reaction product MOF-5W powder. The MOF-5W powder was activated at 200°C for 2h under normal pressure to obtain activated MOF-5W. The preparation method of MOF-5W@Zn pole piece is the same as that in Example 1.

[0096] The MOF-5W@Zn electrode and bare Zn were assembled into symmetrical batteries, and the electrolyte used was 2 mol L -1 ZnSO4 solution, at 5 mA cm -2 The current density is 5 mAh cm -2 The deposition / stripping cycle performance test was carried out under the surface capacity of Fig.18As shown, the MOF-5W synthesized in this example has a good modification effect and can be cycled for more than 500 hours.

[0097] Example 6

[0098] 1.329g of terephthalic acid and 0.68g of sodium hydroxide were added to a mixed solution of 10mL of deionized water and 20mL of DMF, and stirred evenly to obtain solution A. Then 3.512g of zinc acetate dihydrate was added to a mixed solution of 10mL of deionized water and 20mL of DMF, and stirred evenly to obtain solution B. Solutions A and B were mixed and stirred in a water bath at 100°C for 10min. After stirring, the mixture was allowed to stand in a water bath at 100°C for 2 hours. Finally, the product was washed 3 times with N,N-dimethylformamide and deionized water respectively and filtered, and the filtered product was placed in a freeze dryer and dried for 24h to obtain the reaction product MOF-5W powder. The MOF-5W powder was activated at 200°C for 2h under normal pressure to obtain activated MOF-5W. The preparation method of MOF-5W@Zn pole piece is the same as that in Example 1.

[0099] The MOF-5W@Zn electrode and bare Zn were assembled into symmetrical batteries, and the electrolyte used was 2 mol L -1 ZnSO4 solution, at 1 mA cm -2 The current density is 1 mAh cm -2 The deposition / stripping cycle performance test was carried out under the surface capacity of Fig.19 As shown, the battery assembled with MOF-5W prepared within the ratio range of water and DMF defined in the present invention can be cycled for more than 1000 h at a lower overpotential under this test condition.

[0100] Application Examples

[0101] In order to further study the positive effect of MOF coating on the electrochemical performance of zinc-based batteries, a series of electrochemical tests were carried out. NaV3O8·1.5H2O(NVO) / CNTs was used as the positive electrode, and MOF-5W@Zn of Example 1 was used as the negative electrode to assemble a Zn / / NVO button cell (the button cell is a full cell). In order to meet the needs of portable and wearable electronic products, the present invention uses MOF-5W@Zn as the negative electrode, polyacrylamide (PAM) hydrogel electrolyte and NVO / CNTs positive electrode to assemble MOF-5W@Zn / / NVO flexible battery. Fig. 20 The electrochemical performance diagram of the Zn / / NVO button battery and MOF-5W@Zn / / NVO flexible battery prepared in the application example. The CV curves of bare Zn and MOF-5W@Zn as negative electrodes are highly consistent ( Fig. 20 (a), indicating that MOF-5W coating does not affect the electrochemical behavior of NVO / CNTs.-1 At a current density of 2.5 Å, bare Zn can only support dozens of cycles, while the cycling capacity of MOF-5W@Zn is significantly improved, almost 100 times that of bare Zn ( Fig. 20 In addition, the Zn / / NVO button cell assembled with MOF-5W@Zn has better rate performance, which also verifies its better electrochemical stability ( Fig. 20 (c) The prepared Zn / / NVO button cell has a current density of 3A·g -1 286mAh·g -1 High capacity, almost no capacity decay after 1000 cycles, Coulombic efficiency up to 99.7% ( Fig. 20 d). MOF-5W@Zn / / NVO flexible battery (initial voltage see Fig. 20 f) in cutting ( Fig. 20 Middle g), puncture ( Fig. 20 Middle h), folded ( Fig. 20 It showed excellent electrochemical stability and safety in destructive tests such as (i), demonstrating the great potential of MOF-5W@Zn / / NVO flexible batteries in practical applications.

[0102] It can be seen from Example 1 and Comparative Examples 1-2 that the present invention utilizes a suitable MOF pore size to remove part of the bound water in the hydrated zinc ions to achieve a desolvation effect, thereby improving the electrochemical performance.

[0103] It can be seen from Example 1 and Comparative Example 3 that if it is not activated, the solvent molecules occupied in the middle pores of MOF cannot be removed in advance. Therefore, the present invention must first activate the MOF material. After removing the original solvent molecules, the internal pores of the MOF material can better transmit zinc ions.

[0104] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An application of MOF-5W material in improving the performance of aqueous zinc ion batteries through pore restriction effect, characterized in that: The MOF-5W material has a long rice morphology and a channel size of The preparation method of the MOF-5W material comprises the following steps: Add terephthalic acid and sodium hydroxide to a mixed solution of deionized water and N,N-dimethylformamide, and stir evenly to prepare solution A; Add zinc acetate dihydrate to a mixed solution of deionized water and N,N-dimethylformamide, and stir evenly to prepare solution B; The solution A and the solution B are mixed and stirred in a water bath. After the stirring is completed, the solution is allowed to stand in the water bath. Finally, the product is washed and filtered using N,N-dimethylformamide and deionized water. The filtered product is freeze-dried to obtain MOF-5W powder. The MOF-5W powder is activated to obtain MOF-5W material. When preparing solution A, the mass ratio of terephthalic acid to sodium hydroxide is (2:3) to (5:1); When preparing solution B, the mass ratio of zinc acetate dihydrate to deionized water is (1:2) to (1:4); When preparing solution A and solution B, the volume ratio of deionized water to N,N-dimethylformamide is (1:2) to (2:1); The temperature of the water bath during stirring is 30-100° C., and the standing time of the water bath is 1-12 hours.

2. Application of a MOF-5W material in alleviating side reactions on a zinc negative electrode and inhibiting the formation of zinc dendrites, characterized in that: The MOF-5W material is the MOF-5W material described in claim 1.

3. Application of a MOF-5W material in the preparation of an aqueous zinc ion battery, characterized in that: The MOF-5W material is the MOF-5W material described in claim 1.

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