A Covalent Organic Framework Material for Zinc Anode Coating, Its Preparation and Application

Abstract

The present invention relates to a covalent organic framework material for zinc negative electrode coating, its preparation and application. First, 1,4-benzenediboronic acid and 1,3,6,8-tetrabromopyrene are added to a mixed alkaline solvent, and then a catalyst is added. Liquid nitrogen freezing and vacuum pumping are cycled, and then the obtained mixture is subjected to a heating reaction. After the reaction is completed, filtration, washing, and vacuum drying are carried out to obtain the covalent organic framework material COF. The protective layer of the present invention can reduce the polarization of the electrode and effectively inhibit the growth of zinc dendrites, effectively improving the electrochemical performance of zinc ion batteries. The COF material prepared by this method, as the protective layer of the zinc ion battery negative electrode, has the advantages of low cost and environmental friendliness, and has high cycle stability, significantly improving the capacity of zinc ion batteries. It has great application potential in the fields of aqueous zinc ion batteries, energy storage, and environmental protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of new battery electrode materials, and relates to a covalent organic framework material for zinc negative electrode coating, its preparation and application. Background Art

[0002] At present, the demand for developing sustainable and environmentally friendly new energy is increasing year by year. At the same time, clean energy power stations also require safer large-scale energy storage systems. Among many energy storage systems, aqueous rechargeable zinc-ion batteries have great application prospects in large-scale energy storage due to their own safety and low cost. Compared with commercial lithium-ion batteries, zinc metal has the advantages of high mass specific capacity, rich resources, low price, and environmental friendliness. Although zinc metal has many above-mentioned advantages, during the charge and discharge cycle of the battery, due to the uneven deposition of metallic zinc on the surface of the negative electrode, zinc dendrites will be formed. As the zinc dendrites grow continuously, the Coulomb efficiency and capacity of the battery will decrease accordingly, which will greatly reduce the service life of the zinc-ion battery. Coating an artificial protective layer directly on the surface of the zinc negative electrode can directly slow down the growth of zinc dendrites and achieve a high-stability battery life, and this method has many choices and low price. For example, Chinese Patent CN201910764753.2 discloses a kaolin material (composed of Al2O3 and SiO2) for the modification coating of zinc metal negative electrodes, which has a uniform mesoporous structure and can effectively improve the cycle stability of zinc-ion batteries, but there are also problems such as poor conductivity, which is not conducive to the transmission of electrons. Summary of the Invention

[0003] The purpose of the present invention is to provide a covalent organic framework material for zinc negative electrode coating, its preparation and application, so as to solve problems such as the growth of zinc dendrites in the battery cycle of zinc metal negative electrodes.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] One of the technical solutions of the present invention provides a preparation method of a COF material for zinc negative electrode coating. First, 1,4-benzenediboronic acid and 1,3,6,8-tetrabromopyrene are added to a mixed alkaline solvent, then a catalyst is added, and liquid nitrogen freezing and vacuum pumping are cycled, and then the obtained mixture is heated for reaction. After the reaction is completed, filtration, washing, and vacuum drying are carried out to obtain the target product.

[0006] Furthermore, the molar ratio of 1,4-benzenediboronic acid to 1,3,6,8-tetrabromopyrene is 1:1 to 1:2.

[0007] Further, the mixed alkaline solvent is a mixed solvent of N,N-dimethylformamide and an alkaline solution, wherein the volume ratio of N,N-dimethylformamide to the alkaline solution is (1:5) to (1:10).

[0008] Furthermore, the alkaline solution is one of 2 mol / L potassium carbonate and sodium carbonate.

[0009] Further, the catalyst is tetrakis(triphenylphosphine)palladium, and the molar ratio of the amount of the catalyst used to 1,4-benzenediboronic acid is 0.1 to 0.2:100.

[0010] Further, the temperature of the heating reaction is 80 to 150 °C, and the time is 24 to 72 h.

[0011] The technical solution of the present invention provides a COF material for a zinc negative electrode coating, which is prepared by using the preparation method described in any one of the above, and the structural formula of the COF material is as follows:

[0012]

[0013] The third technical solution of the present invention provides an application of a COF material for a zinc negative electrode coating, and the covalent organic framework material is used to prepare a zinc negative electrode coating.

[0014] Further, the process of preparing the zinc negative electrode coating is specifically as follows:

[0015] Take the COF material and mix it with a binder, add an organic solvent, grind it evenly to obtain a slurry, and then coat it on the pretreated zinc foil and dry it in vacuum to obtain an electrode sheet with a zinc negative electrode coating on its surface.

[0016] Furthermore, the thickness of the zinc foil is 20 to 100 μm.

[0017] Furthermore, the vacuum drying is specifically: vacuum treatment at 60 to 90 °C for 16 to 24 h.

[0018] Furthermore, the diameter of the electrode sheet is 10 to 12 mm.

[0019] Furthermore, the thickness of the coated slurry is 5 to 20 μm.

[0020] Furthermore, the binder is polyvinylidene fluoride or polytetrafluoroethylene, and the mass ratio of the COF material to the binder is (8 to 9):(2 to 1).

[0021] Furthermore, the zinc foil pretreatment process is: polish the commercial zinc foil with sandpaper to remove the zinc oxide on its surface; then ultrasonically clean the polished zinc foil with ethanol. Preferably, the mesh number of the sandpaper used is 600 - 1200 mesh.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The protective layer can reduce the polarization of the electrode and effectively inhibit the growth of zinc dendrites, effectively improving the electrochemical performance of the zinc-ion battery.

[0024] (2) The COF material prepared by this method as the protective layer of the zinc-ion battery negative electrode has the advantages of low cost and environmental friendliness, and has high cycle stability performance, significantly improving the capacity of the zinc-ion battery.

[0025] (3) It has great application potential in the fields of aqueous zinc-ion batteries, energy storage, and environmental protection. Brief Description of the Drawings

[0026] Figure 1 is the surface morphology diagram of the COF material prepared by the present invention;

[0027] Figure 2 is the long-term cycling performance diagram of the symmetric battery assembled with the zinc negative electrode based on the COF material coating of the present invention;

[0028] Figure 3 is the long-term cycling performance diagram of the symmetric battery assembled with the commercial zinc foil negative electrode;

[0029] Figure 4 is the surface morphology diagram of the symmetric battery assembled with the zinc negative electrode based on the COF material coating of the present invention after 50 cycles;

[0030] Figure 5 is the surface morphology diagram of the symmetric battery assembled with the commercial zinc foil negative electrode after 50 cycles;

[0031] Figure 6 is the comparison diagram of the rate performance of the full battery assembled with the zinc negative electrode based on the COF material coating of the present invention and the commercial zinc foil and MnO2;

[0032] Figure 7 is the long-term cycling performance diagram of the symmetric battery assembled with the zinc negative electrode based on the COF-1 material coating. Detailed Embodiments

[0033] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0034] In the following embodiments, unless otherwise specified, the raw materials or treatment techniques are all conventional commercially available raw materials or conventional treatment techniques in the art.

[0035] Example 1

[0036] A preparation method of a zinc negative electrode modified with a COF material is as follows:

[0037] (1) First, weigh 38.8 mg of 1,4-benzenediboronic acid as monomer 1 and weigh 25.6 mg of 1,3,6,8-tetrabromopyrene as monomer 2 (the molar ratio of monomer 1 to monomer 2 is 2:1), and place monomer 1 and monomer 2 in a round-bottom flask. Second, add 4 mL of N,N-dimethylformamide and 0.8 mL of 2 mol / L potassium carbonate aqueous solution as a mixed solvent, then add 4.8 mg of tetrakis(triphenylphosphine)palladium. Finally, perform the two processes of liquid nitrogen freezing for 5 min and vacuum pumping for 5 min in cycles 3 times.

[0038] (2) Place the substance obtained in step (1) in an oil bath and heat it at 120 °C for 24 h, then stop the reaction. Subsequently, after cooling to room temperature, centrifuge to obtain the COF material with the electron microscopic morphology as shown in Figure 1 shown.

[0039] (3) First, weigh 40 mg of the COF material obtained in step (2) and place it in a mortar. Second, add 10 mg of polyvinylidene fluoride as a binder and place it in the mortar. Finally, add 0.5 mL of the organic solvent N-methylpyrrolidone to the mortar and grind for 30 min to form a uniform slurry.

[0040] (4) First, polish the zinc foil with sandpaper to remove the zinc oxide on its surface, then ultrasonically clean the polished zinc foil with ethanol and dry it to obtain the cleaned zinc sheet. Second, uniformly coat the slurry of the uniformly ground COF material on the surface of the cleaned zinc foil by a doctor blade method, and the coating thickness is 11 μm. Finally, place the modified zinc metal in a vacuum drying oven and dry it at 80 °C for 12 hours to obtain a zinc negative electrode modified with a COF material.

[0041] For the zinc foil prepared according to this example, using 3M ZnSO4 as the electrolyte and a glass fiber as the separator, assemble a symmetric cell with the modified zinc foil as both the positive and negative electrodes, and test the polarization potential and cycle stability of the symmetric cell. Among them, the cycle stability of the symmetric cell based on the zinc negative electrode modified with the COF material is as shown in Figure 2 shown, and the cycle stability of the symmetric cell of the commercial zinc negative electrode is as shown in Figure 3 shown. The results show that the commercial zinc foil symmetric cell shows a short-circuit phenomenon after about 130 hours of cycling, which means that serious side reactions such as hydrogen evolution and corrosion occur during cycling, resulting in non-uniform electroplating / stripping of zinc. While the symmetric cell based on the zinc negative electrode modified with the COF material can continuously maintain stability for 1500 hours, showing good cycle stability.

[0042] The surface morphology of the symmetric cell with the zinc anode modified by the COF material after 50 cycles is as follows Figure 4 shown, and the surface morphology diagram of the symmetric cell with the commercial zinc anode after 50 cycles is as follows Figure 5 shown. The results show that the zinc anode modified with the COF material also significantly improves the growth of zinc dendrites.

[0043] Example 2

[0044] (1) First, weigh 116.4 mg of 1,4-benzenediboronic acid as monomer 1 and 76.8 mg of 1,3,6,8-tetrabromopyrene as monomer 2 (the molar ratio of monomer 1 to monomer 2 is 2:1), and place monomer 1 and monomer 2 in a round-bottom flask. Second, add 12 mL of N,N-dimethylformamide and 2.4 mL of 2 mol / L potassium carbonate aqueous solution as a mixed solvent, then add 14.4 mg of tetrakis(triphenylphosphine)palladium as a catalyst. Finally, perform the two processes of liquid nitrogen freezing for 5 min and vacuum pumping for 5 min in cycles 3 times.

[0045] (2) Place the substance obtained in step (1) in an oil bath and heat it at 150 °C for 24 h, then stop the reaction. Subsequently, cool it to room temperature and centrifuge to obtain the COF material.

[0046] (3) First, weigh 45 mg of the COF material obtained in step (2) and place it in a mortar. Second, add 5 mg of polyvinylidene fluoride as a binder and place it in the mortar. Finally, add 0.3 mL of the organic solvent N-methylpyrrolidone to the mortar and grind for 30 min to form a uniform slurry.

[0047] (4) First, polish the zinc foil with sandpaper to remove the zinc oxide on its surface, then ultrasonically clean the polished zinc foil with ethanol and dry it to obtain the cleaned zinc foil. Second, uniformly coat the slurry of the uniformly ground COF material on the surface of the cleaned zinc foil by the doctor blade method, and the coating thickness is 8 μm. Finally, place the modified zinc foil in a vacuum drying oven and dry it at 90 °C for 12 hours to obtain the zinc anode modified with the COF material. For the zinc metal sheet prepared according to this example, 3M ZnSO4 is used as the electrolyte, and glass fiber is used as the separator. The modified zinc metal sheet is used as the negative electrode and assembled with the MnO2 positive electrode to form a full cell, and the rate performance of the full cell is tested. The results are as follows Figure 6 shown. At different current densities, the discharge capacity of the COF@Zn / MnO2 full cell prepared with the negative electrode coated with the covalent organic framework material prepared according to the present invention is greater than that of the Zn / MnO2 full cell prepared with the commercial zinc foil, indicating that the rate performance of Zn / MnO2 is much inferior to that of the full cell with the negative electrode of the zinc coated with the COF material.

[0048] Comparative Example 1

[0049] This comparative example is basically the same as Example 1, and the only difference is that 1,4-benzenediboronic acid is replaced with 4,7-diboronopinanediol ester-2,1,3-benzothiadiazole. An aqueous zinc-ion symmetric battery was assembled and then the cycle performance test was carried out on a LAND battery test system. The results show that the COF-1 obtained when the monomer is 4,7-diboronopinanediol ester-2,1,3-benzothiadiazole, and the cycle performance of the battery using this material as the coating material is not good, and its cycle performance curve is as Figure 7 shown.

[0050] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of a zinc negative electrode coating based on a covalent organic framework material, characterized in that, Mix the covalent organic framework material with a binder, add an organic solvent, grind evenly to obtain a slurry, and then coat it on the pretreated zinc foil and dry it under vacuum to obtain an electrode sheet with a zinc negative electrode coating on the surface. The structural formula of the covalent organic framework material is as follows: The binder is polyvinylidene fluoride or polytetrafluoroethylene, and the mass ratio of the covalent organic framework material to the binder is (8-9):(2-1); the thickness of the zinc foil is 20-100 μm; the vacuum drying is specifically: vacuum treatment at 60-90 °C for 16-24 h; the diameter of the electrode sheet is 10-12 mm. The preparation process of the covalent organic framework material is specifically: first add 1,4-benzenediboronic acid and 1,3,6,8-tetrabromopyrene to a mixed alkaline solvent, then add a catalyst, cycle through liquid nitrogen freezing and vacuum pumping, and then heat the resulting mixture for reaction. After the reaction is completed, it is filtered, washed, and dried under vacuum.

2. The preparation method of a zinc negative electrode coating based on a covalent organic framework material according to claim 1, characterized in that, The molar ratio of 1,4-benzenediboronic acid to 1,3,6,8-tetrabromopyrene is 1:1 to 1:

2.

3. The preparation method of a zinc negative electrode coating based on a covalent organic framework material according to claim 1, characterized in that, The mixed alkaline solvent is a mixed solvent of N,N-dimethylformamide and an alkali solution, where the volume ratio of N,N-dimethylformamide to the alkali solution is (1:5)-(1:10).

4. The preparation method of a zinc negative electrode coating based on a covalent organic framework material according to claim 3, characterized in that, The alkali solution is one of 2 mol / L potassium carbonate and sodium carbonate.

5. The preparation method of a zinc negative electrode coating based on a covalent organic framework material according to claim 1, wherein, The catalyst is tetrakis(triphenylphosphine)palladium, and the molar ratio of the amount of the catalyst used to 1,4-benzenediboronic acid is 0.1-0.2:

100.

6. The preparation method of a zinc negative electrode coating based on a covalent organic framework material according to claim 1, characterized in that, The temperature of the heating reaction is 80-150 °C, and the time is 24-72 h.

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