阅读说明：本技术 烷基链修饰的共价有机框架膜在锂电池中的应用 (Application of alkyl chain modified covalent organic framework membrane in lithium battery ) 是由 张根 轩宇峰 许冰清 刘姿铔 潘遥遥 于 2021-07-08 设计创作，主要内容包括：本发明提供了一种烷基链修饰的共价有机框架膜在锂电池中的应用。所述的烷基链修饰的共价有机框架膜的结构式为作为正极材料应用于锂电池中能够有效抑制锂枝晶的产生。(The invention provides an application of an alkyl chain modified covalent organic framework film in a lithium battery. The structural formula of the alkyl chain modified covalent organic framework film is shown in the specification The lithium ion battery cathode material can effectively inhibit the generation of lithium dendrite when being applied to a lithium battery.)

1. The application of the covalent organic framework membrane modified by the alkyl chain in the lithium battery is characterized in that the covalent organic framework membrane modified by the alkyl chain is used as a positive electrode material, and the structural formula of the covalent organic framework membrane modified by the alkyl chain is as follows:

2. the use according to claim 1, wherein said alkyl chain modified covalent organic framework membrane is prepared by the steps of:

dissolving 1,3, 5-trimethylacylbenzene in dichloromethane to form an organic phase solution, dissolving an amino compound modified by an alkyl chain in an acetic acid aqueous solution to form an aqueous phase solution, dropwise adding the aqueous phase solution into the organic phase solution according to the molar ratio of 1,3, 5-trimethylacylbenzene to the amino compound modified by the alkyl chain of 2:3, sealing, performing two-phase interface film forming reaction at room temperature, washing after the reaction is finished, and drying to obtain the covalent organic framework film modified by the alkyl chain.

3. The use according to claim 2, wherein the concentration of 1,3, 5-trimethylacylbenzene in the organic phase solution is 0.01 to 0.3 mol/L; in the aqueous phase solution, the concentration of the amino compound modified by the alkyl chain is 0.01-0.3 mol/L.

4. The use according to claim 2, wherein the concentration of acetic acid in the aqueous acetic acid solution is 3 to 9mol/L, more preferably 6 mol/L.

5. The use according to claim 2, wherein the volume ratio of the organic phase solution to the aqueous phase solution is 1:1 to 1: 10.

6. The application of claim 2, wherein the washing method comprises washing with dichloromethane, ethanol and acetone sequentially, and the total washing time is 12-18 h.

7. The use according to claim 2, wherein the drying temperature is 45 to 50 ℃ and the drying time is 40 to 48 hours.

8. The use according to claim 1, wherein said alkyl chain modified covalent organic framework membrane is prepared by the steps of:

the preparation method comprises the steps of ultrasonically dissolving 1,3, 5-trimethylacylbenzene in a mixed solvent composed of 1, 3-dioxolane and ethylene glycol dimethyl ether, ultrasonically dissolving an alkyl chain modified amino compound in triethylene glycol dimethyl ether, then adding an acetic acid aqueous solution after mixing the two solutions according to the molar ratio of 1,3, 5-trimethylacylbenzene to the alkyl chain modified amino compound of 2:3, continuously ultrasonically mixing the two solutions until the two solutions are uniformly mixed, slowly dripping the mixed solution on a copper foil at room temperature, standing the copper foil, and carrying out in-situ polymerization to obtain the alkyl chain modified covalent organic framework film.

9. The use of claim 8, wherein the concentration of the aqueous acetic acid solution is 2 to 6 mol/L.

10. The application of claim 8, wherein the volume ratio of the 1, 3-dioxolane to the ethylene glycol dimethyl ether is 3: 1-1: 3, and the volume ratio of the mixed solution of the 1, 3-dioxolane and the ethylene glycol dimethyl ether to the triethylene glycol dimethyl ether is 1: 1.

Technical Field

The invention belongs to the field of covalent organic framework compounds, and particularly relates to an application of an alkyl chain modified covalent organic framework film in a lithium battery.

Background

The current commercial lithium ion battery has potential safety hazards such as short circuit, electrolyte leakage and the like due to the use of a large amount of flammable and explosive hazardous and toxic organic solvents. One of the most significant factors in causing explosion and leakage of lithium batteries is the growth of lithium dendrites. In the use of the lithium battery, the aging of the diaphragm and the anode material causes the lithium dendrite to slowly grow and gradually puncture the diaphragm, so that the electrolyte is unevenly distributed, the thermal stability is rapidly reduced, the effective components are lost, and the battery is invalid, the electrolyte leaks, the battery explodes and the like. Therefore, how to reasonably solve the growth of lithium dendrites to enhance the service life and safety index of lithium batteries is still a considerable work.

Covalent Organic Frameworks (COFs) materials are porous organic framework materials composed of light elements (C, N, O, etc.). COFs materials usually adopt a bottom-up synthesis strategy, various functional groups are introduced into synthesis, and corresponding functions and applications are more and more extensive while the structural diversity of the COFs materials is increased, such as the fields of photocatalysis, ion screening, gas adsorption and the like. Because of the characteristics of the COFs, such as porosity, regular structure, large specific surface area, various structures, etc., the COFs are widely applied to the aspects of catalysis, ion conduction, gas storage, compound separation and batteries.

The functional organic framework structure of the COFs material can avoid the situation that the COFs material is dissolved in organic electrolyte to a great extent, so that the stability of the structure of the porous COFs material is influenced. Document 1 discloses that COF materials prepared from 4 monomers are used as positive electrode materials of lithium batteries, and it is found that the batteries are discharged at 1C and 5C rates under initial capacities of 242.3mAh/g and 206.7mAh/g, respectively, the final capacity is only 182.3mAh/g, and the retention rate is only 86% (ACS applied materials)&interlaces, 2018,10(49): 42233-. Document 2 uses rGO membranes in lithium batteries and the measured current becomes stable during cycling, indicating that the membranes have some inhibitory effect on lithium dendrites. Initial capacity of the battery was 1386.9mAhg^-1Thereafter, the capacity remained stable at 1275.3mAhg for the 5 th and 50 th cycles, respectively^-1And 1169.4mAhg^-1But the capacity retention after 50 cycles was only 84.3% (angelw.chem.int.ed.2018, 57,16072.). The method inhibits the growth of lithium dendrites to a certain extent, thereby prolonging the service life of the lithium battery, and maintaining high capacity retention rate in a period of time, but only maintains about 85 percent of capacity in 50 cyclesAmount of the compound (A).

Disclosure of Invention

The invention provides an application of an alkyl chain modified covalent organic framework film in a lithium battery. When the covalent organic framework film modified by the alkyl chain is used as a positive electrode material and applied to a lithium battery, lithium dendrite can be effectively inhibited.

The alkyl chain modified covalent organic framework film (COF-C-2) is an amino compound ([ C-2, 2-NHNH) modified by three aldehydes in 1,3, 5-trimethylacylbenzene and alkyl chain₂]) The two amine groups are connected to form a hexagonal topological structure synthesized by covalent bond of-C ═ N-NH, and the structural formula is as follows:

the structural formula of the alkyl chain modified amino compound is as follows:

the structural formula of the 1,3, 5-trimethylacylbenzene is as follows:

the invention also provides a preparation method of the covalent organic framework membrane modified by the alkyl chain, which adopts an interfacial polymerization method and comprises the following steps:

dissolving 1,3, 5-trimethylacylbenzene in dichloromethane to form an organic phase solution, dissolving an amino compound modified by an alkyl chain in an acetic acid aqueous solution to form an aqueous phase solution, dropwise adding the aqueous phase solution into the organic phase solution according to the molar ratio of 1,3, 5-trimethylacylbenzene to the amino compound modified by the alkyl chain of 2:3, sealing, performing two-phase interface film forming reaction at room temperature, washing after the reaction is finished, and drying to obtain the covalent organic framework film modified by the alkyl chain.

Preferably, the concentration of the 1,3, 5-trimethylacylbenzene in the organic phase solution is 0.01-0.3 mol/L.

Preferably, the concentration of the amino compound modified by the alkyl chain in the aqueous phase solution is 0.01-0.3 mol/L.

Preferably, the concentration of acetic acid in the acetic acid aqueous solution is 3-9 mol/L, and more preferably 6 mol/L.

Preferably, the volume ratio of the organic phase solution to the aqueous phase solution is 1: 1-1: 10.

Preferably, the washing method is to wash with dichloromethane, ethanol and acetone sequentially, and the total washing time is 12-18 h.

Preferably, the drying temperature is 45-50 ℃, and the drying time is 40-48 h.

Further, the invention provides another preparation method of the covalent organic framework film modified by the alkyl chain, which comprises the following steps of in-situ polymerization on the surface of the copper foil:

the preparation method comprises the steps of ultrasonically dissolving 1,3, 5-trimethylacylbenzene in a mixed solvent composed of 1, 3-dioxolane and ethylene glycol dimethyl ether, ultrasonically dissolving an alkyl chain modified amino compound in triethylene glycol dimethyl ether, then adding an acetic acid aqueous solution after mixing the two solutions according to the molar ratio of 1,3, 5-trimethylacylbenzene to the alkyl chain modified amino compound of 2:3, continuously ultrasonically mixing the two solutions until the two solutions are uniformly mixed, slowly dripping the mixed solution on a copper foil at room temperature, standing the copper foil, and carrying out in-situ polymerization to obtain the alkyl chain modified covalent organic framework film.

Preferably, the concentration of the acetic acid aqueous solution is 2-6 mol/L.

Preferably, the volume ratio of the 1, 3-dioxolane to the ethylene glycol dimethyl ether is 3: 1-1: 3.

Preferably, the volume ratio of the mixed solution of the 1, 3-dioxolane and the ethylene glycol dimethyl ether to the triethylene glycol dimethyl ether is 1: 1.

Compared with the prior art, the invention has the following advantages:

(1) the preparation of the covalent organic framework film is realized through interface polymerization or simple and convenient operation of in-situ polymerization on the surface of the copper foil, alkyl chain modification is realized on the premise of ensuring the structural regularity of the covalent organic framework film, and the uniformity and stability of the pore channel of the covalent organic framework material are improved;

(2) the alkyl chain modified covalent organic framework film is applied to a lithium battery as a positive electrode material, the growth of lithium dendrites is simply and effectively inhibited through the repeated structural unit, and the capacity retention rate of the battery is still 87.56% after 150 cycles.

Drawings

FIG. 1 shows (a) COF-C-2 film, (b) COF-C-2 powder, (C) C-2,2-NHNH₂And (d) the XRD pattern of 1,3, 5-trimethylacylbenzene;

FIG. 2 shows (a) COF-C-2 film, (b) C-2,2-NHNH₂And (c) a Fourier transform infrared spectrum of 1,3, 5-trimethylacylbenzene;

FIG. 3 is a nitrogen adsorption diagram of a COF-C-2 film;

FIG. 4 shows an unmodified lithium copper cell and the use of C-2,2-NHNH₂A cycle efficiency map of a 1,3, 5-trimethylacylbenzene monomer modified LS electrolyte cell;

FIG. 5 is a graph of the cycling efficiency of COF-C-2 modified LS electrolyte lithium batteries;

FIG. 6 is a graph of the cycling efficiency of an unmodified LS cell and a COF-C-2 modified LS electrolyte cell;

FIG. 7 is a charge and discharge graph of LS electrolyte batteries modified with COF-C-2 and unmodified LS electrolyte batteries tested at cycle 5;

FIG. 8 is a charge and discharge curve of LS electrolyte batteries modified with COF-C-2 and non-modified LS electrolyte batteries tested at 185 th cycle.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below by way of embodiments with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Unless otherwise indicated in the context of the present application, the terms and abbreviations used in the present application are those well known to those skilled in the art; unless otherwise indicated below, the manufacturer is a conventional product that may be obtained by commercial purchase.

The alkyl chain modified amino compound can be obtained commercially or prepared by self, and the specific synthetic route is as follows:

the method comprises the following specific steps:

(1) compound 1 c: 1mmol of the compound 1a, 3mmol of the compound 1b and 1mmol of K₂CO₃To 30mL of Acetone (Acetone) in N₂Under the protective atmosphere of (1), reacting for 48 hours at 65 ℃, extracting with dichloromethane after the reaction is finished, washing with saturated saline solution, drying with anhydrous sodium sulfate, removing the solvent by spinning, and carrying out column layer separation with a developing agent to obtain a compound 1 c;

(2)C-2,2-NHNH₂: adding the compound 1C and hydrazine hydrate into 15mL of ethanol solution for reaction for 12 hours, freezing at low temperature, directly filtering, washing white solid with petroleum ether solvent for multiple times to obtain C-2,2-NHNH₂。

The electrolyte can be purchased commercially or prepared by self, and the specific preparation method is as follows:

LS electrolyte: 1.0mol/L lithium bistrifluoromethylenesulfonamide (LiTFSI) in 1.0% LiNO in 1,3 Dioxolane (DOL) glycol dimethyl ether (DME) at a volume ratio of 1:1₃And (3) solution.

Example 1

Synthesis of COF-C-2

(1) The method is synthesized by in-situ polymerization on the surface of a copper foil, and comprises the following specific steps:

4.3mg of amino group-containing monomeric alkyl chain-modified amino compound (C-2, 2-NHNH) was weighed₂) Then, 5mL of a glass tube was put in, and 5mL of 1, 3-dioxolane and ethylene glycol dimethyl ether (volume ratio 1: 1) the mixed solution of (1). 2.8mg of aldehyde group-containing monomer 1,3, 5-trimethylacylbenzene was weighed out, and added to a 5mL glass tube, and 5mL of triethylene glycol dimethyl ether was added. The two monomers were dissolved in the solvent separately by sonication, mixed, and then 0.1mL of a 3mol/L aqueous acetic acid solution was added to the mixed solution. Finally mixing the mixed solutionDropwise adding the COF-C-2 material on a copper foil, and standing for 24 hours to form a powdery COF-C-2 material, wherein the synthetic route is as follows:

(2) synthesized by interfacial polymerization, and comprises the following specific steps:

0.1mmol of 1,3, 5-trimethylacylbenzene was weighed out and dissolved in dichloromethane to form an organic phase solution, 0.15mmol of C-2,2-NHNH was weighed out₂Dissolving the organic solvent in 6mol/L acetic acid aqueous solution to form aqueous phase solution, gradually dropwise adding the aqueous phase solution to the top of the organic phase solution, sealing, performing film forming reaction for 40-48 h at room temperature through a two-phase interface, washing after the reaction is finished, and drying to obtain the covalent organic framework film COF-C-2 modified by the alkyl chain, wherein the synthetic route is as follows:

(3) the battery assembly method is as follows:

the copper foil with the COF-C-2 modification is used as a positive electrode material, the LS electrolyte is used as electrolyte, and the lithium sheet is used as a negative electrode sheet. The battery assembly is carried out in the vacuum glove box according to the sequence: and (3) placing the reed, the gasket, the lithium sheet and the diaphragm with the negative electrode shell facing upwards, dropwise adding electrolyte, placing the positive electrode sheet (facing downwards), and finally buckling the positive electrode shell. And the battery was sealed in a glove box and taken out of the pouch. Note that: the gasket, the positive plate, the diaphragm and the lithium plate are placed in the middle as much as possible, and plastic tweezers are used in the operation process.

(4) The service efficiency of the battery is tested, and the specific test method is as follows:

the model of the blue-electricity series battery test system adopted by the test is as follows: LANdct V7.3. The specific test process is as follows: the battery is placed in a constant temperature box at 25 ℃, and is fixed according to the anode and the cathode by using a special button battery clamp so as to be connected with the test of the blue-electricity series battery. And selecting a proper channel according to the test current required by the battery to be tested, and starting the channel.

Editing a test program according to the test requirements, wherein the test program comprises the following steps: standing for 12 hours; discharging at constant current of 565.2 muA for 2 hours; constant current charging at 565.2 muA, and continuing until the voltage is 1V; the test is finished after 500 times of circulation; data was recorded every 5 s. And after the setting is finished, closing and returning to a starting interface, selecting a data storage path, naming the file, and starting. The active material parameters were set and since the positive electrode of the test cell was copper foil, the active material was set directly to 1 mg. And finally, starting the program.

Comparative example 1

With C-2,2-NHNH₂And the mixed pressing sheet material of the 1,3, 5-trimethylacylbenzene monomer is used as a positive electrode material, the LS electrolyte is used as electrolyte, and the lithium sheet is used as a negative electrode sheet. The battery assembly is carried out in a vacuum glove box, and the specific implementation method is as follows:

in a glove box, weighing a mixture of 3: 2C-2, 2-NHNH₂1,3, 5-trimethylacylbenzene monomer is ground in an agate mortar for 15 minutes, 1g of uniformly mixed powder is poured into a powder tabletting machine (10MPa) for tabletting, and the tabletting size is similar to that of a copper foil. Subsequently, the battery assembly is carried out: and (3) putting the reed, the gasket, the lithium plate and the diaphragm into the negative electrode shell upward, dropwise adding the electrolyte, placing the pressing sheet and the positive plate, and finally buckling the positive electrode shell. And the battery was sealed in a glove box and taken out of the pouch. Note that: the gasket, the pressing sheet, the positive plate, the diaphragm and the lithium sheet are placed in the middle as much as possible, and plastic tweezers are used in the operation process.

Comparative example 2

Copper foil is used as a positive electrode material, LS electrolyte is used as electrolyte, and a lithium sheet is used as a negative electrode sheet. The battery assembly is carried out in a vacuum glove box, and the specific implementation method is as follows:

in the glove box, the battery assembly is carried out according to the sequence: and (3) putting the reed, the gasket, the lithium plate and the diaphragm into the negative electrode shell upward, dropwise adding the electrolyte, placing the pressing sheet and the positive plate, and finally buckling the positive electrode shell. And the battery was sealed in a glove box and taken out of the pouch. Note that: the gasket, the pressing sheet, the positive plate, the diaphragm and the lithium sheet are placed in the middle as much as possible, and plastic tweezers are used in the operation process.

FIG. 1 shows (a) COF-C-2 film, (b) COF-C-2 powder, (C) C-2,2-NHNH₂And (d) XRD of 1,3, 5-trimethylacylbenzene, the XRD patterns of COF-C-2 films prepared by the two synthesis methods are consistent, and the successful synthesis of the covalent organic framework COF-C-2 film modified by the alkyl chain can be confirmed.

FIG. 2 shows (a) COF-C-2 film, (b) C-2,2-NHNH₂And (C) Fourier transform infrared spectroscopy of 1,3, 5-trimethylacylbenzene, the infrared spectra of the COF-C-2 films prepared by the two synthesis methods are consistent, and the COF-C-2 films are seen to be 1226cm^-1And 1675cm^-lThe formation of C ═ N bonds can be confirmed by the infrared absorption peak of (a).

FIG. 3 is a nitrogen adsorption diagram of a COF-C-2 film, and the nitrogen adsorption diagrams of the COF-C-2 film prepared by two synthesis methods are consistent, which shows that the covalent organic framework film has rich specific surface area and pore distribution, and is very beneficial to the conduction of lithium ions.

FIG. 4 shows an unmodified lithium copper cell of comparative example 2 and C-2,2-NHNH used in comparative example 1₂And 1,3, 5-trimethylacylbenzene monomer modified LS electrolyte battery. Comparing the two, the charge-discharge efficiency of the unmodified lithium copper battery at the 100 th circle is 72.17 percent, and the charge-discharge efficiency is C-2,2-NHNH₂71.56% of the lithium copper battery modified by 1,3, 5-trimethylacylbenzene monomer, which is approximately the same as the above-mentioned battery, shows that C-2,2-NHNH₂And 1,3, 5-trimethylacylbenzene monomer do not function to suppress lithium dendrites.

FIG. 5 is a cycle efficiency graph of a COF-C-2 modified LS electrolyte lithium battery. At round 185, the COF-C-2 modified lithium battery still maintained 87.01% efficiency.

Fig. 6 is a graph of cycle efficiency for the unmodified LS electrolyte cell and the COF-C-2 modified LS electrolyte cell of comparative example 2. By comparison, the efficiency of the COF-C-2 modified LS electrolyte battery is still 87.56% after 150 cycles, and the efficiency of the unmodified LS electrolyte battery is only 53.89% remained, which shows that the COF-C-2 can greatly inhibit the growth of lithium dendrites.

FIG. 7 is a graph showing the charge and discharge curves of the LS electrolyte battery modified with COF-C-2 at cycle 5 and the LS electrolyte battery unmodified in comparative example 2. Upon initial cycling, it was found that the difference between charge and discharge of the LS electrolyte cell of COF-C-2 was smaller than that of the unmodified LS electrolyte cell.

FIG. 8 is a charge-discharge curve diagram of LS electrolyte battery modified with COF-C-2 at 185 th cycle and LS electrolyte battery unmodified in comparative example 2, and it can be seen that LS electrolyte battery modified with COF-C-2 can still inhibit the growth of lithium dendrite well after many cycles.