CN113725421B - Preparation method and application of covalent organic framework material modified zinc cathode - Google Patents

Abstract

The invention provides a preparation method and application of a zinc cathode modified by a covalent organic framework material, which are used for solving the problems of easy corrosion and uncontrollable growth of dendritic crystals existing in a zinc metal cathode in the electrochemical charge-discharge process and improving the poor cycling stability of a zinc ion battery caused by corrosion of the zinc cathode and growth of the dendritic crystals. The invention mixes the covalent organic framework material with hydrophilic group, coordination group, rich regular pore structure and strong corrosion resistance with the conductive material and the binder, and then coats the mixture on the surface of the zinc cathode to form a modified coating with a specific thickness. The hydrophilic group of the covalent organic framework material enhances the hydrophilicity of the zinc cathode, so that the wettability of the electrolyte is improved; the coordination group has coordination induction effect on zinc ions, and the aim of inhibiting the growth of zinc dendrites is fulfilled; the coating has good corrosion resistance, and can effectively prevent the corrosion of the zinc cathode in the charging and discharging process, thereby improving the cycle stability of the water system zinc ion battery taking zinc metal as the cathode.

Description

Preparation method and application of zinc anode based on covalent organic framework material modification

technical field

The invention relates to the technical field of zinc ion batteries, in particular to a method for preparing a zinc negative electrode modified with a covalent organic framework material and an application thereof.

Background technique

Extensive use of fossil energy has exacerbated the energy shortage and caused serious environmental pollution. The development and utilization of renewable energy such as solar energy and wind energy is imminent. However, there are problems such as instability and discontinuity in the use of renewable energy and the process of grid connection. Safe and efficient energy storage and conversion equipment can effectively realize the "peak shifting and valley filling" of the power grid and the storage of renewable energy, which has become the focus and difficulty of people's research. In addition, with the rapid development of various mobile devices and intelligent equipment, all kinds of electric vehicles, mobile phones, drones, etc. in our daily life also need to be equipped with safe, environmentally friendly high-performance battery systems. For example, lithium-ion batteries with organic systems have high specific capacity and good cycle stability and have become mainstream commodities in the field of secondary batteries. However, due to problems such as limited lithium resources, flammable electrolyte, and lithium dendrite growth, lithium-ion batteries also have problems such as high cost and great safety hazards. Electric vehicles and electric bicycles with lithium-ion battery systems have problems such as spontaneous combustion and explosion, which have aroused people's attention to battery safety. Therefore, developing a safer and more efficient battery system has become an important topic in the field of energy storage and conversion.

Aqueous secondary batteries have attracted much attention because they avoid flammable organic electrolyte systems. Aqueous zinc-ion batteries have attracted extensive attention from researchers due to their low cost, safe and non-toxic raw materials, environmental friendliness, abundant resources, and high energy density, and have become one of the most potential aqueous energy storage devices.

As an anode material for zinc-ion batteries, zinc metal has the advantages of abundant reserves, high theoretical capacity (820 mAh/g), low oxidation-reduction potential (-0.76 V), and environmental friendliness, making it an anode with the most potential for practical application. However, during the electrochemical charge-discharge process, zinc metal anodes will suffer from corrosion, dendrite growth and other problems, which seriously affect the cycle stability of zinc-ion batteries. Therefore, the modification of zinc metal anode has become an important scientific and technical problem. An excellent zinc anode should have the characteristics of good electrolyte wettability, excellent zinc ion conductivity, uniform electric field distribution, and no dendrite growth. At present, there are corresponding research literatures and patents dedicated to the modification of metallic zinc anodes. Patent 202011502235.2 uses a modified polyacrylonitrile coating to protect the zinc anode to improve the performance of the zinc anode. However, the strength and mechanical properties of polyacrylonitrile materials are poor, and there is a problem of instability in the acidic electrolyte for a long time. Patent 202011619692.X is a kind of mixed slurry of organic high polymer powder and inorganic powder used in the field of zinc metal negative electrode modification. Although such composites can optimize zinc nucleation sites, they have poor electrical conductivity and cannot provide a uniform electric field. Patent 202010818783.X adopts a spontaneous reaction method to form a ZnxM modified layer on the surface of the metal zinc anode. M is a layered structure material with a large interlayer distance, such as vanadium-based oxides, manganese-based oxides, layered hydroxides, Prussian Blue compounds, Mxene compounds. This patent mainly uses inorganic compounds to modify the zinc negative electrode, but the functional group of the formed modification layer is single, and the pore structure cannot be adjusted. Patent 202010865269.1 uses a metal-organic framework (MOF) to modify the zinc anode to improve its electrochemical behavior. However, although MOF can regulate surface functional groups and pore structure, MOF materials have poor conductivity, poor stability, and poor long-term stability in electrolyte. Zheng et al., Science 366, 645-648 reported that the direction of zinc dendrite growth can be controlled by graphene coating; there are also literature and patent reports on the growth of Al ₂ O ₃ and Fe ₂ O ₃ on the surface of zinc anode by atomic layer deposition technology , TiO ₂ and other metal oxides as the protective layer of zinc metal. However, these methods are difficult to achieve excellent zinc anodes at the same time, and technical modifications with multiple characteristics (good electrolyte wettability, good acid and alkali resistance, adjustable zinc ion conduction channels, and limited zinc dendrite growth) are required. need.

Covalent organic framework (COF) material is a kind of organic framework material linked by covalent bonds. It has strong structural stability, and also has the advantages of easy modification of functional groups and easy regulation of pore structure. Through design, experiment and practice Organically compounding it with conductive materials as a protective coating is expected to develop a zinc anode that is hydrophilic, can conduct zinc ions, and inhibits the growth of zinc dendrites.

Contents of the invention

Aiming at the above technical problems, the present invention proposes a method for preparing a zinc negative electrode modified by a covalent organic framework material and its application. The covalent organic framework material with hydrophilic groups, coordination groups, rich regular pore structure and strong corrosion resistance After the frame material is mixed with a conductive material and a binder, it is coated on the surface of the zinc negative electrode to form a modified coating with a specific thickness. Among them, the hydrophilic group enhances the hydrophilicity of the zinc metal negative electrode, thereby improving the wettability of the electrolyte; The purpose of inhibiting the growth of zinc dendrites is achieved through the coordination between the coordination group and zinc ions; and its special regular pore structure can improve the conductivity of zinc ions, and the coating has good corrosion resistance, which can effectively prevent zinc metal Corrosion of the negative electrode, thereby improving the cycle stability of the aqueous zinc-ion battery with zinc metal as the negative electrode.

In order to achieve the above object, the technical solution of the present invention is achieved in that:

A method for preparing a zinc negative electrode based on the modification of a covalent organic framework material, using a covalent organic framework material containing a hydrophilic group and coordinating with zinc as a coating, and coating the zinc surface, the steps are as follows:

(1) Add the monomer 1 containing the hydrophilic group and the monomer 2 containing the coordination group into the mixed solvent. Under the condition of the presence of the catalyst, the liquid nitrogen freezing is carried out in circulation, and the vacuum pumping process is 2~5 Times, wherein, the monomer 1 is trialdehyde phloroglucinol;

(2) The substance obtained in step (1) is subjected to a heating reaction, and after the reaction is completed, it is washed and vacuum-dried to obtain a covalent organic framework material;

(3) mixing the covalent organic framework material obtained in step (2) with a conductive material and a binder, adding an organic solvent, and uniformly grinding to form a slurry;

(4) Coating the slurry obtained in step (3) on the cleaned zinc metal sheet, and vacuum drying to obtain a zinc metal sheet modified with a covalent organic framework material as a coating.

Preferably, monomer 2 is 2,5-diamino-1,4-dihydroxybenzene dihydrochloride or 2,6-diaminoanthraquinone, and the molar ratio of monomer 1 to monomer 2 is (1:1)~ (1:2).

Preferably, the mixed solvent is a mixed solvent of 1,4-dioxane and mesitylene, wherein the volume ratio of 1,4-dioxane to mesitylene is (1:10)~(10: 1), the total mass of monomer 1 and monomer 2 dissolved in 100 mL of mixed solvent is 2-5 g.

Preferably, the catalyst is 6 mol/L acetic acid aqueous solution, and the volume ratio of the mixed solvent to the catalyst solution is 100: (10-20 ).

Preferably, the temperature of the heating reaction is 100-160 ^o C, and the heating reaction time is 72 h.

Preferably, the conductive material is any one or a combination of acetylene black, carbon black, carbon nanotubes, polyaniline or polythiophene, and the binder is polyvinylidene fluoride or polytetrafluoroethylene, wherein the covalent organic The mass ratio of the frame material, the conductive material and the adhesive is 100:(1~200):(1~30).

Preferably, the organic solvent is any one or a combination of N-methylpyrrolidone, ethanol, methanol or ethylene glycol, and every 1 mL of organic solvent dissolves and disperses the covalent organic framework material, conductive material and binder. The total mass is 50~200mg.

Preferably, the zinc metal sheet is cleaned by acid, distilled water and absolute ethanol respectively, the acid is a hydrochloric acid solution of 0.1-0.5 mol/L, the time of pickling, the time of distilled water washing and the time of absolute ethanol washing are all 5-60 min.

Preferably, the coating method is any one of scraping coating, spin coating or drop coating, the temperature of vacuum drying after coating is 60~120 ^o C, and the time of vacuum drying after coating is 6~24 h, wherein the coating The loading capacity of the layer is 0.01~5 mg/cm ² .

Preferably, the application of the zinc negative electrode preparation method based on the modification of the covalent organic framework material in the field of aqueous zinc ion batteries.

Beneficial effects of the present invention:

1. In the present invention, it will have hydrophilic groups (hydroxyl groups), coordination groups (aldehyde groups (-CHO), imine bonds (-C=N-)), regular pore structure, and good corrosion resistance The COF material is used for the surface modification of zinc metal, and a zinc negative electrode for zinc ion batteries with good electrolyte infiltration, zinc ion conduction, and zinc dendrite suppression is obtained. The contact angle of the modified zinc metal negative electrode changed from 87.8 ^o to 60.4 ^o , indicating that the hydrophilicity was significantly improved (test results in Example 1), which was helpful for the infiltration of the electrolyte.

2. In the present invention, it will have hydrophilic group (hydroxyl group), coordination group (aldehyde group (-CHO), imine bond (-C=N-)), regular pore structure, and good corrosion resistance The COF material is used for the surface modification of zinc metal, and a zinc negative electrode for zinc ion batteries with good electrolyte infiltration, zinc ion conduction, and zinc dendrite suppression is obtained. Due to the rich pore structure of COF material, excellent zinc ion conduction function can be realized, which improves the electrochemical performance of zinc anode. At a current density of 1 mA/cm ² , the polarization potential of the symmetrical battery assembled with the modified zinc metal was reduced to 28 mV (the test result of Example 1).

3. In the present invention, it will have hydrophilic groups (hydroxyl groups), coordination groups (aldehyde groups (-CHO), imine bonds (-C=N-)), regular pore structure, and good corrosion resistance The COF material is used for the surface modification of zinc metal, and a zinc negative electrode for zinc ion batteries with good electrolyte infiltration, zinc ion conduction, and zinc dendrite suppression is obtained. Because COF materials are rich in groups such as hydroxyl groups and nitrogen-containing double bonds, these functional groups have a certain coordination effect with zinc ions, which can limit the growth of zinc dendrites during charge and discharge. The modified zinc symmetric battery can be cycled for more than 125 h at a current density of 1 mA/cm ² , with no significant change in the polarization potential, and no significant change in the morphology of the electrode sheet before and after the reaction (test results in Example 1).

4. In the present invention, a kind of good electrolytic solution infiltrating prepared, zinc metal that can conduct zinc ions and inhibit zinc dendrites is used as the negative electrode of the aqueous zinc ion battery, the positive electrode is selected from a-phase MnO ₂ , the diaphragm is selected from glass fiber, and the electrolyte When it is 2 M ZnSO ₄ +0.1 M MnSO ₄ , the specific capacity can reach more than 450 mAh/g after 50 cycles in the zinc-ion battery assembled at a current density of 0.1 A/g, showing a high specific capacity. (the beneficial effect of embodiment 1).

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a flowchart of the steps of Embodiment 1 of the present invention.

Fig. 2 is an electron micrograph of the covalent organic framework material obtained in Example 1 of the present invention.

Fig. 3 is the structural formula of the covalent organic framework material obtained in Example 1 of the present invention.

Figure 4 is a comparison chart of the contact angle measurement results of the covalent organic framework material modified zinc anode and the blank zinc anode in Example 1 of the present invention, wherein a is the contact angle measurement result of the blank zinc anode, and b is the covalent organic framework material modification Diagram of the contact angle measurement results of the zinc anode.

Figure 5 is a comparison diagram of electron micrographs before and after the electrochemical cycle of the covalent organic framework material modified zinc negative electrode obtained in Example 1 of the present invention and the blank zinc negative electrode, wherein, a is the SEM morphology of the blank zinc negative electrode before the reaction Figure, b is the SEM topography of a blank zinc negative electrode after 50 cycles, c is the SEM topography of the covalent organic framework material in Example 1 of the present invention before the zinc negative electrode is modified, and d is the covalent organic framework material in Example 1 of the present invention. The SEM image of the frame material modified zinc anode after 50 cycles.

Fig. 6 is a performance comparison diagram of two symmetrical batteries corresponding to the covalent organic framework material modified zinc anode and the blank zinc anode in Example 1 of the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

A method for preparing a zinc negative electrode based on a covalent organic framework material modification, as shown in Figure 1, the steps are as follows:

(1) First, weigh 21 mg of trialdehyde phloroglucinol as monomer 1, and weigh 21 mg of 2,5-diamino-1,4-dihydroxybenzene dihydrochloride as monomer 2 (monomer 1 and The molar ratio of monomer 2 is 1:1.5), put monomer 1 and monomer 2 in a glass bottle; secondly, add 0.7 mL 1,4-dioxane and 0.7 mL mesitylene as a mixed solvent, where The volume ratio of 1,4-dioxane and mesitylene is 1, which means that the total mass of monomer 1 and monomer 2 dissolved in 100 mL of mixed solvent is 3 g; again, add 6 mol/L of acetic acid 0.233 mL of aqueous solution was used as the catalyst, which was equivalent to adding 16.6 mL of catalyst solution per 100 mL of mixed solvent; finally, two processes of freezing with liquid nitrogen for 5 min and vacuum pumping for 5 min were cycled three times.

(2) The material obtained in step (1) was placed in a blast drying oven at 120 o ^C for 72 h to terminate the reaction, and then dried in a vacuum oven at 120 ^o C for 12 h to obtain an electron micrograph COF material as shown in Figure 2 and structural formula in Figure 3.

(3) First, weigh 21 mg of the COF material obtained in step (2) and put it in a mortar; secondly, weigh 6 mg of acetylene black as a conductive material and 3 mg of PVDF as a binder and put it in a mortar; finally , add 0.3 mL of organic solvent NMP into the mortar, and grind for 30 min to form a homogeneous slurry.

(4) First, soak the zinc metal sheet in 0.1 mol/L hydrochloric acid solution, distilled water, and absolute ethanol solution for 10 min in order to clean; secondly, dry the cleaned zinc sheet; thirdly, the steps ( 3) The uniformly ground COF slurry is evenly coated on the surface of the cleaned zinc sheet by scraping, and the COF material loading is controlled to 0.2 mg/cm ² ; finally, the modified zinc metal is placed in a vacuum drying oven , and dried at 80°C for 12 hours to obtain a COF material-modified zinc anode. Among them, the test results of the contact angle of the modified zinc metal sheet and the blank zinc metal sheet are shown in Fig. 4 .

According to the zinc metal sheet prepared in this example, 2 M ZnSO ₄ + 0.1 M MnSO ₄ was used as the electrolyte, glass fiber was used as the separator, and the modified zinc metal sheet was used as the electrode sheet to assemble a symmetrical battery, and the polarization of the symmetrical battery was tested. Potential and cycle stability. The electron micrographs of the electrode sheets of the symmetrical battery before and after cycling are shown in Figure 5, and the cycle stability of the symmetrical battery is shown in Figure 6.

Example 2

A method for preparing a zinc negative electrode based on the modification of a covalent organic framework material. The difference between this example and Example 1 is that in step (1) of this example, the mass of monomer 1 is 15.3 mg, and the mass of monomer 2 is 2,6-diaminoanthraquinone, the mass of monomer 2 is 41.4 mg, 1,4-dioxane in the mixed solvent is 0.4 mL, mesitylene in the mixed solvent is 1.0 mL, and 1,4- The volume ratio of dioxane and mesitylene is 0.4, that is, the total mass of monomer 1 and monomer 2 dissolved in 100 mL of mixed solvent is 4.05 g; in step (2) of this example, the reaction is heated The temperature is 100 ^oC ; in step (3) of this example, the weighed COF material is 50 mg, the weighed acetylene black is 40 mg, the weighed PVDF is 10 mg, and 0.3 mL of NMP and 0.3 mL Ethanol was used as an organic solvent; in step (4) of this embodiment, the COF material loading was controlled to be 0.4 mg/cm ² .

It is worth noting that in this example, 2 M ZnSO ₄ + 0.1 M MnSO ₄ was used as the electrolyte, glass fiber was used as the diaphragm, and the modified zinc metal sheet was used as the electrode sheet to assemble a symmetrical battery, and the polarization of the symmetrical battery was tested. Potential and cycle stability.

Other steps in this embodiment are the same as those in Embodiment 1, and will not be repeated here.

Example 3

A method for preparing a zinc negative electrode based on the modification of a covalent organic framework material. The difference between this example and Example 1 is that in step (1) of this example, the mass of monomer 1 is 42 mg, and the mass of monomer 2 is The mass is 42 mg, the 1,4-dioxane in the mixed solvent is 0.38 mL, and the mesitylene in the mixed solvent is 3.82 mL, which is equivalent to the total amount of dissolved monomer 1 and monomer 2 in 100 mL of mixed solvent. The mass is 2 g, and the acetic acid aqueous solution is 0.42 mL, which is equivalent to adding 10 mL of the catalyst solution per 100 mL of the mixed solvent; in step (2) of this example, the drying time in the vacuum oven is 24 h; In step (3) of this example, 100 mg of the COF material obtained in step (2) was weighed, 1 mg of carbon nanotubes was weighed as a conductive material, 1 mg of PTFE was weighed as a binder, and the organic solvent was 2.04 mL ethylene glycol, the grinding time is 10 min; in step (4) of this example, the hydrochloric acid solution is 0.15 mol/L, the coating method is drop coating, and the COF material loading is controlled to 0.01 mg/cm ² .

It is worth noting that in this example, 2 M ZnSO ₄ + 0.1 M MnSO ₄ was used as the electrolyte, glass fiber was used as the diaphragm, and the modified zinc metal sheet was used as the electrode sheet to assemble a symmetrical battery, and the polarization of the symmetrical battery was tested. Potential and cycle stability.

Other steps in this embodiment are the same as those in Embodiment 1, and will not be repeated here.

Example 4

A method for preparing a zinc negative electrode based on the modification of a covalent organic framework material. The difference between this example and Example 1 is that in step (1) of this example, the mass of monomer 1 is 42 mg, and the mass of monomer 2 is is 42 mg, 1,4-dioxane is 1.527 mL, and mesitylene is 0.153 mL as a mixed solvent, and the volume ratio of 1,4-dioxane and mesitylene is 10, which is equivalent to 100 mL of mixed solvent The total mass of dissolved monomers in the solution is 5 g, and the aqueous acetic acid solution is 0.336 mL, which is equivalent to adding 20 mL of catalyst solution per 100 mL of mixed solvent; The temperature in the vacuum oven is 140 °C, the temperature in the vacuum oven is 80 ^oC , and the drying time is 24 h; mg and polyaniline 100 mg as the conductive material, PVDF 30 mg as the binder, 1.65 mL of NMP as the organic solvent, and the grinding time is 60 min; The COF material loading was 5 mg/cm ² .

It is worth noting that in this example, 2 M ZnSO ₄ + 0.1 M MnSO ₄ was used as the electrolyte, glass fiber was used as the diaphragm, and the modified zinc metal sheet was used as the electrode sheet to assemble a symmetrical battery, and the polarization of the symmetrical battery was tested. Potential and cycle stability.

Other steps in this embodiment are the same as those in Embodiment 1, and will not be repeated here.

Example 5

A method for preparing a zinc negative electrode based on the modification of a covalent organic framework material. The difference between this example and Example 1 is that in step (1) of this example, the mass of monomer 1 is 84.0 mg, and the mass of monomer 2 is 107.2 mg of 2,6-diaminoanthraquinone, 2.39 mL 1,4-dioxane and 2.39 mL mesitylene as a mixed solvent, the volume ratio of 1,4-dioxane and mesitylene is 1, Equivalent to 4 g of the total mass of dissolved monomers in 100 mL of mixed solvent, 0.717 mL of acetic acid aqueous solution, equivalent to 15 mL of catalyst solution added to 100 mL of mixed solvent; in step (2) of this example , the temperature in the blast drying oven is 160°C, and the drying in the vacuum oven is 24 h; in step (3) of this example, weigh 100 mg of the COF material obtained in step (2), and 12.5 mg of graphene As a conductive material, 12.5 mg of PTFE was used as a binder, 1.25 mL of methanol was used as an organic solvent, and the grinding time was 60 min; in step (4) of this example, the hydrochloric acid solution was 0.2 mol/l, and the coating method was spin Coating, control the COF material loading to 1 mg/cm ² .

It is worth noting that in this example, 2 M ZnSO ₄ + 0.1 M MnSO ₄ was used as the electrolyte, glass fiber was used as the diaphragm, and the modified zinc metal sheet was used as the electrode sheet to assemble a symmetrical battery, and the polarization of the symmetrical battery was tested. Potential and cycle stability.

Other steps in this embodiment are the same as those in Embodiment 1, and will not be repeated here.

Example 6

A method for preparing a zinc negative electrode based on the modification of a covalent organic framework material. The difference between this example and Example 1 is that in step (1) of this example, the monomer 2 is 35.7 mg of 2,6-diamino Anthraquinone, 0.9 mL of 1,4-dioxane and 0.5 mL of mesitylene as a mixed solvent, the volume ratio of 1,4-dioxane and mesitylene is 1.8, which is equivalent to 100 mL of mixed solvent The total mass of dissolved monomers is 4.05 g, and the acetic acid aqueous solution is 0.14 mL, which is equivalent to adding 10 mL of catalyst solution per 100 mL of mixed solvent; in step (2) of this embodiment, the temperature in the vacuum oven is 130 ^oC , and the drying time is 24 h; in step (3) of this example, weigh 60 mg of the COF material obtained in step (2), 15 mg of carbon black and 15 mg of polythiophene as conductive materials, PTFE 10 mg as a binder, 0.5 mL of ethylene glycol and 0.5 mL of ethanol as an organic solvent, and the grinding time is 20 min; in step (4) of this example, the coating method is spin coating, and the COF material loading is controlled It is 2 mg/cm ² .

It is worth noting that in this example, 2 M ZnSO ₄ + 0.1 M MnSO ₄ was used as the electrolyte, glass fiber was used as the diaphragm, and the modified zinc metal sheet was used as the electrode sheet to assemble a symmetrical battery, and the polarization potential of the symmetrical battery was tested. and cycle stability.

Other steps in this embodiment are the same as those in Embodiment 1, and will not be repeated here.

Example 7

A method for preparing a zinc negative electrode based on the modification of a covalent organic framework material. The difference between this example and Example 1 is that in step (1) of this example, the monomer 2 is 14 mg of 2,5 diamino- 1,4 dihydroxybenzene dihydrochloride (the molar ratio of monomer 1 and monomer 2 is 1:1), 0.7 mL of 1,4-dioxane and 0.7 mL of mesitylene as a mixed solvent, 1 , the volume ratio of 4-dioxane and mesitylene is 1, which is equivalent to 2.5 g of the total mass of dissolved monomers in 100 mL of mixed solvent, adding 0.233 mL of 6 mol/L aqueous acetic acid as a catalyst, equivalent to The volume of the catalyst solution added to 100 mL of mixed solvent was 16.6 mL; two cycles of freezing with liquid nitrogen for 5 min and vacuum pumping for 5 min were carried out twice. In step (3) of this example, weigh 21 mg of the COF material obtained in step (2), 6 mg of graphene as a conductive material, and 3 mg of PVDF as a binder; in step (4) of this example , the coating method is blade coating, and the COF material loading is controlled to be 0.5 mg/cm ² .

It is worth noting that in this example, 2 M ZnSO ₄ + 0.1 M MnSO ₄ was used as the electrolyte, glass fiber was used as the diaphragm, and the modified zinc metal sheet was used as the electrode sheet to assemble a symmetrical battery, and the polarization potential of the symmetrical battery was tested. and cycle stability.

Other steps in this embodiment are the same as those in Embodiment 1, and will not be repeated here.

Example 8

A method for preparing a zinc negative electrode based on the modification of a covalent organic framework material. The difference between this example and Example 1 is that in step (1) of this example, the monomer 2 is 31.5 mg of 2,5 diamino- 1,4 dihydroxybenzene dihydrochloride (the molar ratio of monomer 1 and monomer 2 is 1:2), 1 mL of 1,4-dioxane and 1 mL of mesitylene as a mixed solvent, 1 , the volume ratio of 4-dioxane and mesitylene is 1, which is equivalent to 2.625 g of the total mass of dissolved monomers in 100 mL of mixed solvent, adding 0.333 mL of 6 mol/L aqueous acetic acid as a catalyst, equivalent The volume of the catalyst solution added to 100 mL of the mixed solvent was 16.6 mL; the process of freezing with liquid nitrogen for 5 min and vacuum pumping for 5 min was repeated 5 times. In step (3) of this example, weigh 21 mg of the COF material obtained in step (2), 6 mg of carbon nanotubes as a conductive material, and 3 mg of PTFE as a binder; in step (4) of this example ), the coating method is drop coating, and the COF material loading is controlled at 1 mg/cm ² .

It is worth noting that in this example, 2 M ZnSO ₄ + 0.1 M MnSO ₄ was used as the electrolyte, glass fiber was used as the diaphragm, and the modified zinc metal sheet was used as the electrode sheet to assemble a symmetrical battery, and the polarization potential of the symmetrical battery was tested. and cycle stability.

In addition, the technical features involved in the various embodiments of the present invention described above can be combined with each other as long as there is no conflict with each other. The following table is a list of some key reaction conditions for implementation cases 1-8:

Table 1. Specific implementation conditions for implementation cases 1-8

Example of implementation effect

After the zinc negative electrode prepared in Example 1 was assembled into a battery as an electrode sheet, the electrochemical performance test was performed, and the steps were as follows:

1. Assembly of Zinc Symmetrical Cells

Die the metal zinc electrode sheets of the above examples into discs with a diameter of 13 mm, use glass fibers as separators, and use 2 M ZnSO ₄ +0.1 M MnSO ₄ solution as electrolyte, assemble CR-2032 button cells and use The packaging machine was used for packaging, and then the electrochemical performance test was performed after standing still for more than 12 h.

2. Assembly of Aqueous Zn-ion Batteries

The metal zinc electrode sheet of the above-mentioned embodiment is punched into a disc with a diameter of 8 mm, and the a-phase _MnO is selected as the positive electrode, the glass fiber is used as the separator, and the 2 M ZnSO ₄ +0.1 M MnSO ₄ solution is used as the electrolyte, The CR-2032 button cells were assembled and packaged with a packaging machine, and then left to stand for more than 12 h before the electrochemical performance test.

3. Electrochemical performance test

Fig. 5 is a comparison diagram of electron microscope photos before and after the reaction between the COF modified zinc negative electrode sheet and the blank zinc negative electrode obtained in Example 1 of the present invention. As can be seen from the figure, after 50 cycles, more zinc dendrites appeared on the surface of the blank zinc anode, but the zinc electrode sheet modified by COF maintained a good shape stability, indicating the excellent effect of this COF material modification.

Fig. 6 is a performance comparison diagram of two symmetrical batteries corresponding to the COF-modified zinc negative electrode sheet and the blank zinc negative electrode in Example 1 of the present invention. It can be seen from the figure that at a current density of 1 mg/cm ² , the polarization potential of the symmetrical battery is below 28 mV, confirming the good stability of the modified zinc anode.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (8)

1. A preparation method of a covalent organic framework material modified zinc cathode is characterized in that a covalent organic framework material which contains hydrophilic groups and has coordination with zinc ions is used as a coating and coated on the surface of zinc, and the preparation method comprises the following steps:

(1) Adding a monomer 1 containing a hydrophilic group and a monomer 2 containing a coordination group into a mixed solvent, and circularly performing liquid nitrogen freezing and vacuum pumping processes for 2~5 times in the presence of a catalyst, wherein the monomer 1 is trialdehyde phloroglucinol; monomer 2 is 2,5 diamino-1,4 dihydroxybenzene dihydrochloride; the molar ratio of the monomer 1 to the monomer 2 is (1:1) - (1:2);

(2) Heating the substance obtained in the step (1) for reaction, and washing and vacuum drying the substance after the reaction is finished to obtain a covalent organic framework material;

(3) Mixing the covalent organic framework material obtained in the step (2) with a conductive material and a binder, adding an organic solvent, and grinding uniformly to form slurry; the conductive material in the step (3) is any one or a combination of several of carbon black, carbon nano tubes, polyaniline or polythiophene, the binder is polyvinylidene fluoride or polytetrafluoroethylene, and the mass ratio of the covalent organic framework material to the conductive material to the binder is 100: (1 to 200): (1 to 30);

(4) And (4) coating the slurry obtained in the step (3) on the cleaned zinc metal sheet, and performing vacuum drying to obtain the zinc metal sheet modified by taking the covalent organic framework material as a coating.

2. The method for preparing the zinc anode based on covalent organic framework material modification according to claim 1, wherein the mixed solvent in the step (1) is a mixed solvent of 1,4-dioxane and mesitylene, wherein the volume ratio of 1,4-dioxane to mesitylene is (1.

3. The preparation method of the covalent organic framework material modification-based zinc anode according to claim 1, wherein the catalyst in the step (1) is a 6 mol/L acetic acid aqueous solution, and the volume ratio of the mixed solvent to the catalyst solution is 100: (10 to 20).

4. The preparation method of the zinc anode based on covalent organic framework material modification of claim 1, wherein the temperature of the heating reaction in the step (2) is 100-160 ℃ ^o C, heating for a reaction time of 72 h.

5. The preparation method of the zinc anode based on covalent organic framework material modification according to claim 1, wherein the organic solvent in the step (3) is any one or a combination of N-methylpyrrolidone, ethanol, methanol or ethylene glycol, and the total mass of the covalent organic framework material, the conductive material and the binder dissolved and dispersed in the organic solvent is 50-200 mg per 1 mL.

6. The preparation method of the zinc cathode modified based on the covalent organic framework material as claimed in claim 1, wherein the zinc metal sheet in the step (4) is respectively washed by acid, distilled water and absolute ethyl alcohol, the acid is 0.1 to 0.5 mol/L hydrochloric acid solution, and the time of acid washing, the time of distilled water washing and the time of absolute ethyl alcohol washing are all 5 to 60 min.

7. The preparation method of the covalent organic framework material-modified zinc negative electrode as claimed in claim 1, wherein the coating manner in the step (4) is blade coating, spin coating or drop coating, and the temperature of vacuum drying after coating is 60 to 120 ℃ ^o C, the vacuum drying time after coating is 6 to 24 hours, wherein the loading capacity of the coating after coating is 0.01 to 5 mg/cm ² 。

8. The application of the preparation method of the zinc cathode based on the modification of the covalent organic framework material according to any one of claims 1 to 7 in the field of aqueous zinc ion batteries.

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