A method for preparing a metal organic framework coating to construct a water-based zinc ion battery negative electrode

Abstract

The application discloses a preparation method of a metal organic framework coating for constructing a water system zinc ion battery negative electrode, and the method comprises the following steps: mixing zinc ions, dimethyl imidazole and a regulator to prepare a ZIF-8 precursor solution; then centrifuging the ZIF-8 precursor solution to obtain a precipitate, adding an organic solvent and an appropriate amount of a binder into the precipitate to mix into a colloid, coating the colloid on a zinc negative electrode, drying and cooling; finally, performing high-temperature treatment on the electrode in an inert atmosphere, so that oligomers are fully polymerized, and the coating crystal type is optimized. Compared with a traditional method, the polymerization induction strategy is simple to operate and easy to control, the ZIF-8 coating prepared by the method is more dense and uniform, and there is no accumulated pore. The protection ability of the coating prepared by the new method for the zinc electrode is better than that of the MOF-based coating prepared by the traditional method, because the ZIF-8-M coating is more uniform, and the product formed after the transformation is also more uniform and dense.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of organic synthesis, in particular to a preparation method of a metal organic framework coating for constructing a water-based zinc ion battery negative electrode. BACKGROUND

[0002] The water-based zinc ion battery is a new type of battery, and has attracted extensive attention of researchers since being proposed. The negative electrode of the water-based zinc ion battery is zinc, which is different from lithium with high activity. The zinc cannot react with oxygen in the air, and is very safe. In addition, the zinc has limited activity, and cannot react with water, so that the water-based electrolyte can be used, and the toxic and harmful organic electrolyte is avoided. The positive electrode of the water-based zinc ion battery is manganese dioxide, which is also a non-toxic and harmless material. The water-based zinc ion battery has high theoretical capacity (820 mAh g-1, 5855 mAh cm-3) and low cost. Due to the advantages of the water-based zinc ion battery, the water-based zinc ion battery has become a research hotspot since being proposed. However, there is still a problem that is difficult to solve for the water-based zinc ion battery, that is, the instability of the zinc electrode. The instability of the zinc electrode is mainly caused by the non-uniform deposition of zinc ions on the zinc electrode. Diffusion is the first step in the deposition of zinc ions, and plays an important role in the deposition of zinc ions. Therefore, the deposition of zinc ions can be affected or controlled by controlling the diffusion of zinc ions.

[0003] Up to now, various materials have been reported to be used for limiting and guiding the diffusion of zinc ions. For example, the accumulation pores formed by the particulate material, and the gaps remaining in the solidification process of the organic matter can be used to guide and limit the diffusion of zinc ions, and the modified materials have better cycle stability than the bare zinc electrode. However, these materials have not completely solved the problem. The accumulation pores formed by the materials or the gaps formed during the forming process can control and limit the transmission of zinc ions to a certain extent, but the sizes of the accumulation pores or the gaps are different, and the distribution is uneven, which is not conducive to better control of the transmission of zinc ions. Therefore, it is of great significance to develop a MOF-based coating with a specific pore structure and an infinite expansion network structure. SUMMARY

[0004] The application aims at the above-mentioned problems, and provides a preparation process of high-strength and high-heat-resistance p-aramid nanometer paper, which is simple in process, excellent in product performance, environment-friendly and low in cost.

[0005] The preparation method of the metal organic framework coating for constructing the water-based zinc ion battery negative electrode comprises the following steps:

[0006] S1, mixing a methanol solution of dimethyl imidazole, a methanol solution of zinc ions and a triethylamine adjusting agent to prepare a ZIF-8 precursor solution;

[0007] S2, centrifuging the ZIF-8 precursor solution to obtain a precipitate, adding an organic solvent and a binder solution into the precipitate to mix into a colloid, coating on a zinc negative electrode, drying and cooling to form an oligomer;

[0008] S3, high-temperature treatment of the electrode in an inert atmosphere to fully polymerize the oligomer and optimize the coating crystal form.

[0009] In some embodiments, the concentration of the methanol solution of zinc ions is 1.2544 mol / L, the concentration of the methanol solution of dimethyl imidazole is 0.4571 mol / mL, the volume ratio of the methanol solution of zinc ions to the methanol solution of dimethyl imidazole is 1:1, and the molar ratio of the methanol solution of zinc ions to the regulator is 1:4-1:0.5.

[0010] In some embodiments, in the step S2, the organic solvent is methanol, and the binder solution is a DMF solution of polyvinylidene fluoride.

[0011] In some embodiments, in the step S2, the concentration of the DMF solution of polyvinylidene fluoride is 1 mg / mL, and the volume ratio of the methanol, the DMF solution of polyvinylidene fluoride, and the ZIF-8 precursor solution is 3:1:10.

[0012] In some embodiments, in the step S2, the drying temperature is 60-80℃, and the time is 2-3h.

[0013] In some embodiments, in the step S3, the inert gas is argon or nitrogen, and the treatment temperature is 120-200℃.

[0014] Compared with the prior art, the present application has the following advantages:

[0015] The present application provides a preparation method of a metal organic framework coating for constructing a water-based zinc ion battery negative electrode. The polymerization induction strategy is simple and easy to control, and the ZIF-8 coating prepared by the method is more dense and uniform, and has no accumulated pores. The protective ability of the coating prepared by the new method for the zinc electrode is better than that of the MOF-based coating prepared by the traditional method, because the ZIF-8-M coating is more uniform, and the product formed after the transformation is also more uniform and dense. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 ZIF-8-M coating crystal form (a) and SEM morphology (b) characterization;

[0017] Figure 2 Contact angle of ZIF-8-M / Zn electrode;

[0018] Figure 3SEM images of ZIF-8-M cross-sections with different thicknesses, (a) ZIF-8-M-30 / Zn, (b) ZIF-8-M / Zn,

[0019] (c) ZIF-8-M-80 / Zn;

[0020] Figure 4 (a) XRD characterization of ZIF-8-M / Zn electrodes treated at different temperatures, (b) SEM characterization of ZIF-8-M-R120, (c) SEM characterization of ZIF-8-M-R200;

[0021] Figure 5 Symmetric constant current charge-discharge test of ZIF-8-M-R120 / Zn electrode;

[0022] Figure 6 SEM images of MOF-based coatings prepared by traditional method;

[0023] Figure 7 Symmetric constant current charge-discharge test of bare zinc electrode, ZIF-8-P / Zn electrode, ZIF-8-M / Zn electrode. DETAILED DESCRIPTION

[0024] The application will be further described below in connection with specific embodiments. It should be understood that these embodiments are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that after reading the content of the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope of the appended claims.

[0025] Example 1:

[0026] Preparation of ZIF-8-M / Zn electrode

[0027] 0.186 g of zinc nitrate was weighed into 5 mL of methanol, which was dissolved in 5 mL of methanol, and was labeled as solution 1. 0.103 g of dimethylimidazole was weighed and dissolved in 5 mL of methanol, 160 μL of triethylamine was added, and ultrasonic dissolution was performed, which was labeled as solution 2. Solutions 1 and 2 were quickly mixed, stirred for 30 min, and then the mixed solution was transferred to a refrigerator for cold storage, ready for use.

[0028] 1 mL of ZIF-8 precursor solution was taken, centrifuged (5 min, 8000 rpm), the upper solution was removed, and then 300 μL of methanol and 100 μL of 1 mg / mL polyvinylidene fluoride DMF solution were added to the lower precipitate, which was ultrasonically dispersed. 50 μL of the turbid liquid obtained in the previous step was coated on a bare zinc electrode, which was then transferred to a sealed petri dish, dried in an 80°C oven for 2 h, and then naturally cooled for standby.

[0029] wherein, Figure 1 Fig. 1 (a) and (b) are characterization of ZIF-8-M coating, from XRD it can be basically confirmed that the coating is ZIF-8-M coating, the coating is a whole piece, not a particle accumulation, and the surface is smooth, dense, and has no accumulation hole;

[0030] Figure 2 Fig. 2 is the contact angle of ZIF-8-M / Zn electrode, compared with bare zinc electrode, the contact angle of the electrode after ZIF-8 coating with water is reduced, and the hydrophilic interface is changed, which is beneficial to the infiltration of electrolyte to the electrode;

[0031] Figure 3 Fig. 3 (b) is the SEM image of the cross section of ZIF-8-M / Zn electrode.

[0032] Example 2:

[0033] Preparation of ZIF-8-M-30 / Zn electrode

[0034] Take 1 mL of ZIF-8 precursor solution, centrifuge (5 min, 8000 rpm), remove the upper solution, then add 300 μL of methanol and 100 μL of 1 mg / mL polyvinylidene fluoride DMF solution to the lower precipitate, and ultrasonic dispersion. Take 30 μL of the turbid liquid obtained in the above step to coat the bare zinc.

[0035] wherein, Figure 3 Fig. 4 (a) is the SEM image of the cross section of ZIF-8-M-30 / Zn electrode.

[0036] Example 3:

[0037] Preparation of ZIF-8-M-80 / Zn electrode

[0038] Take 1 mL of ZIF-8 precursor solution, centrifuge (5 min, 8000 rpm), remove the upper solution, then add 300 μL of methanol and 100 μL of 1 mg / mL polyvinylidene fluoride DMF solution to the lower precipitate, and ultrasonic dispersion. Take 80 μL of the turbid liquid obtained in the above step to coat the bare zinc electrode, and then transfer it to a sealed culture dish, dry it in an 80°C oven for 2 h, and then naturally cool it for standby.

[0039] Example 4:

[0040] Preparation of ZIF-8-M-R120 / Zn electrode

[0041] The ZIF-8-M / Zn electrode is subjected to high temperature treatment for 4 h under nitrogen atmosphere using a tube furnace, and the temperature is 120°C.

[0042] wherein, Figure 4(a) (b) are XRD and SEM characterization of ZIF-8-M / Zn electrode treated at high temperature of 120℃ respectively, small concave and rod appear on the surface of ZIF-8 after heat treatment, because during heat treatment, oligomers tend to more perfect crystals, migration and formation.

[0043] Example 5:

[0044] Preparation of ZIF-8-M-R200 / Zn electrode

[0045] The ZIF-8-M / Zn electrode was treated at high temperature for 4h under nitrogen atmosphere using a tube furnace, and the temperature was 200℃.

[0046] wherein, Figure 4 (a) (c) are XRD and SEM characterization of ZIF-8-M / Zn electrode treated at high temperature of 120℃ respectively. Cracks appear on the ZIF-8 coating after treatment at 200℃, because the thermal expansion coefficient of ZIF-8 coating and zinc foil is different during heat treatment.

[0047] wherein, Figure 5 Symmetric electrode constant current charge-discharge test of ZIF-8-M-R120 / Zn electrode, the cycle life of ZIF-8-M / Zn electrode treated at 120℃ is about 1180h.

[0048] Comparative Example 1:

[0049] Preparation of ZIF-8-P / Zn electrode

[0050] The MOF-based coating prepared by the conventional method is as follows:

[0051] ZIF-8 particles and PVDF were weighed according to a mass ratio of 8:2, placed in a mortar and ground to mix uniformly, and then transferred to a weighing bottle. 450μL of DMF was added to every 100mg of the mixture, and after stirring for 12h, ZIF-8 particle slurry was obtained. The obtained ZIF-8 particle slurry was uniformly scraped onto a commercial zinc foil using an automatic coating machine, and then transferred to an 80℃ oven to dry most of the solvent, and then transferred to a 120℃ vacuum oven to dry for 12h to completely remove the solvent. The zinc foil coated with the ZIF-8 particle coating was cut into small round pieces with a diameter of 1.4cm to obtain a MOF particle modified zinc negative electrode.

[0052] wherein, Figure 6 The SEM image of the MOF-based coating prepared by the conventional method is shown in the figure, and it can be seen from the figure that the MOF-based coating prepared by the conventional method has a large number of stacking pores, while the ZIF-8 coating prepared by the present application is Figure 4 It can be seen that it is more dense and uniform, and has no stacking pores.

[0053] Figure 7 The symmetrical electrodes constant current charge-discharge test was carried out for the bare zinc electrode, ZIF-8-P / Zn electrode and ZIF-8-M / Zn electrode. As can be seen from the figure, the cycle life of the bare zinc is about 120h, the cycle life of the ZIF-8-P / Zn electrode is about 550h, and the cycle life of the ZIF-8-M / Zn electrode is as long as 2400h. The comparison of the cycle life of the symmetrical battery shows that the ZIF-8 coating plays a protective role for the zinc electrode, but the ZIF-8 coating obtained by the polymerization coating method has better protective performance for the zinc electrode, and the cycle life thereof is 20 times that of the bare zinc electrode and 4 times that of the ZIF-8-P / Zn under the same conditions. -2 The symmetrical electrodes constant current charge-discharge test was carried out for the bare zinc electrode, ZIF-8-P / Zn electrode and ZIF-8-M / Zn electrode. As can be seen from the figure, the cycle life of the bare zinc is about 120h, the cycle life of the ZIF-8-P / Zn electrode is about 550h, and the cycle life of the ZIF-8-M / Zn electrode is as long as 2400h. The comparison of the cycle life of the symmetrical battery shows that the ZIF-8 coating plays a protective role for the zinc electrode, but the ZIF-8 coating obtained by the polymerization coating method has better protective performance for the zinc electrode, and the cycle life thereof is 20 times that of the bare zinc electrode and 4 times that of the ZIF-8-P / Zn under the same conditions.

[0054] Finally, it should be noted that the skilled person in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and the description in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements shall fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for fabricating a metal-organic framework coating to construct a water-based zinc-ion battery anode, characterized in that, The method comprises the following steps: S1, mixing methanol solution of dimethyl imidazole, methanol solution of zinc ion and adjusting agent triethylamine to prepare ZIF-8 precursor solution; S2, centrifuging the ZIF-8 precursor solution to obtain precipitate, mixing organic solvent and binder solution in the precipitate to form colloid, coating on zinc negative electrode, drying and cooling to form oligomer; S3, high temperature treatment of electrode in inert atmosphere to make oligomer fully polymerize and optimize coating crystal form.

2. The production method according to claim 1, characterized by, The concentration of the methanol solution of zinc ion is 1.2544 mol / L, the concentration of the methanol solution of dimethyl imidazole is 0.4571 mol / mL, the volume ratio of the methanol solution of zinc ion to the methanol solution of dimethyl imidazole is 1:1, and the molar ratio of the methanol solution of zinc ion to the adjusting agent is 1:4-1:0.

5.

3. The production method according to claim 1, characterized by, In the step S2, the organic solvent is methanol, and the binder solution is DMF solution of polyvinylidene fluoride.

4. The production method according to claim 3, characterized by, In the step S2, the concentration of the DMF solution of polyvinylidene fluoride is 1 mg / mL, and the volume ratio of methanol, DMF solution of polyvinylidene fluoride and ZIF-8 precursor solution is 3:1:

10.

5. The preparation method according to claim 1, characterized in that, In the step S2, the drying temperature is 60-80℃, and the time is 2-3 h.

6. The method of claim 1, wherein, In the step S3, the inert atmosphere is argon or nitrogen, and the treatment temperature is 120-200℃.

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