A ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material and its preparation method and application

Abstract

The present invention provides a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material and its preparation method and application. The present invention first obtains a polypyrrole Schiff base polymer through a simple aldehyde-amine reaction and oxidative polymerization process, then obtains a ZIF-67 / polypyrrole Schiff base composite material through in situ growth, and finally obtains a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material through carbonization. The preparation method of the present invention is simple and low in cost; the obtained ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material can accelerate Li + The ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material obtained in this invention exhibits excellent electrochemical properties in lithium-sulfur batteries, including high reversible specific capacity, excellent rate capability, and cycling stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy electronic materials, and specifically relates to a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material and a preparation method and application thereof. Background Art

[0002] With the development of society, the consumption of fossil fuels is increasing, and the environmental problems caused by their combustion are becoming more and more serious. This has prompted people to develop alternative and sustainable renewable energy sources. However, the effective use of these energy sources requires efficient and economical energy storage systems. Among various energy storage systems, lithium-sulfur batteries are considered to be one of the most promising energy storage systems due to their advantages such as high theoretical specific capacity, high energy density, low cost, and environmental friendliness (Fang R, Zhao S, Sun Z, et al. More reliable lithium-sulfur batteries: status, solutions and prospects, Adv. Mater. 2017, 29(48): 1606823.). However, despite these potential advantages, the development of lithium-sulfur batteries is still subject to some limitations and challenges, including the poor conductivity of sulfur, the easy volume expansion during the conversion between sulfur and Li2S, and the easy dissolution of polysulfides in the electrolyte during the charge and discharge process, resulting in a "shuttle effect". In order to solve various problems in the application of lithium-sulfur batteries, scientific and technological personnel have conducted a lot of research work and found that reasonable design and optimization of the membrane interlayer structure is a method that can effectively improve the reversible capacity, Coulombic efficiency and cycle stability of lithium-sulfur batteries (Li C, Liu R, Xiao Y, et al. Recent progress of separators in lithium-sulfurbatteries, Energy Storage Mater. 2021, 40: 439-460.).

[0003] Chinese patent document CN115939662A discloses a method for preparing a carbonized Zn-MOF-modified separator for lithium-sulfur batteries, as well as its products and applications. ZIF-67 is placed in a tubular furnace and, under nitrogen protection, heated at a rate of 10°C / min to 500°C, 700°C, and 900°C for 12 hours to obtain a series of carbonized ZIF-67 materials. The metal cations in these materials have a strong catalytic effect on polysulfide conversion, inhibiting the dissolution of polysulfides, slowing the shuttle effect, and improving the battery's cycling performance. The carbonized porous skeleton structure not only has good lithium ion conductivity but also facilitates rapid electron conduction, enhancing the battery's rate performance. However, the reversible specific capacity and rate performance of the separator material obtained in this invention for lithium-sulfur batteries still need to be improved, and relevant data such as cycling performance have not been disclosed.

[0004] Therefore, it is urgent to seek a high-performance lithium-sulfur battery separator interlayer with a simple preparation method and low cost. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a ZIF-67 / polypyrrole Schiff base derived carbon interlayer material and its preparation method and application. The present invention first obtains a polypyrrole Schiff base polymer through a simple aldehyde-amine reaction and oxidative polymerization process, then obtains a ZIF-67 / polypyrrole Schiff base composite material through in situ growth, and finally obtains a ZIF-67 / polypyrrole Schiff base derived carbon interlayer material through carbonization. The preparation method of the present invention is simple and has low cost; the obtained ZIF-67 / polypyrrole Schiff base derived carbon interlayer material can accelerate Li + The ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material obtained in this invention exhibits excellent electrochemical properties in lithium-sulfur batteries, including high reversible specific capacity, excellent rate capability, and cycling stability.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for preparing a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material comprises the following steps:

[0008] (1) dissolving melamine and pyrrole-2-carboxaldehyde in a solvent to obtain a mixed solution; adding a catalyst to carry out an aldehyde-amine reaction; adding pyrrole, fully dispersing it, adding an oxidant, carrying out an oxidative polymerization reaction, and then performing solid-liquid separation, washing, and drying to obtain a polypyrrole Schiff base polymer;

[0009] (2) fully dispersing a polypyrrole Schiff base polymer, a surfactant, and a cobalt salt in a solvent, adding 2-methylimidazole, reacting, solid-liquid separation, washing, and drying to obtain a ZIF-67 / polypyrrole Schiff base composite material;

[0010] (3) The ZIF-67 / polypyrrole Schiff base composite material was carbonized to obtain the ZIF-67 / polypyrrole Schiff base derived carbon interlayer material.

[0011] Preferably according to the present invention, in step (1), the solvent is deionized water.

[0012] According to the preferred embodiment of the present invention, in step (1), the mass ratio of melamine to pyrrole-2-carboxaldehyde is 0.5-3:0.5-2, preferably 1.26:0.6-1.2, more preferably 1.26:0.8-1, and most preferably 1.26:0.95; the volume ratio of melamine to deionized water is 0.5-3:50-80 g / mL, preferably 1-1.5:60 g / mL.

[0013] Preferably, according to the present invention, in step (1), the method for preparing the mixed solution comprises the steps of: adding melamine to a solvent, stirring at 60-90° C. until fully dissolved; then adding pyrrole-2-carboxaldehyde, stirring at 60-90° C. for 10-60 minutes to obtain a mixed solution.

[0014] According to the preferred embodiment of the present invention, in step (1), the catalyst is glacial acetic acid; and the volume ratio of melamine mass to catalyst is 0.5-3:0.5-2 g / mL, preferably 1-1.5:1 g / mL.

[0015] According to the preferred embodiment of the present invention, in step (1), the amide reaction temperature is 60 to 90° C., the amide reaction time is 1 to 10 h, and the amide reaction is carried out under stirring conditions.

[0016] According to the preferred embodiment of the present invention, in step (1), the mass ratio of melamine to pyrrole is 0.5-3:0.1-3 g / mL, preferably 1-1.5:0.1-1 g / mL, and more preferably 1.26:0.5 g / mL.

[0017] According to the present invention, preferably, in step (1), the oxidant is an aqueous solution of ferric chloride, wherein the mass concentration of ferric chloride is 0.01 to 0.1 g / mL; the volume ratio of the mass of ferric chloride to pyrrole in the oxidant is 0.2 to 1:0.1 to 1 g / mL, preferably 0.5 to 1:0.5 g / mL.

[0018] According to the preferred embodiment of the present invention, in step (1), the temperature of the oxidative polymerization reaction is -5 to 5°C, the time of the oxidative polymerization reaction is 10 to 30 hours, and the oxidative polymerization reaction is carried out under stirring conditions.

[0019] Preferably, according to the present invention, in step (2), the cobalt salt is Co(NO3)2·6H2O, the surfactant is cetyltrimethylammonium bromide (CTAB), and the solvent is deionized water.

[0020] According to the present invention, preferably, in step (2), the mass ratio of the polypyrrole Schiff base polymer, the surfactant and the cobalt salt is 0.1-1:0.1-0.8:0.1-3, preferably 0.4:0.2:0.4-2, more preferably 0.4:0.2:0.4-0.8, and most preferably 0.4:0.2:0.6; the volume ratio of the polypyrrole Schiff base polymer to deionized water is 0.1-1:60 g / mL.

[0021] According to the present invention, preferably, in step (2), the mass ratio of cobalt salt to 2-methylimidazole is 0.1-3:0.5-2, preferably 0.4-2:1.2, more preferably 0.4-0.8:1.2, and most preferably 0.6:1.2.

[0022] According to the preferred embodiment of the present invention, in step (2), the reaction temperature is room temperature, the reaction time is 1 to 3 hours, and the reaction is carried out under stirring conditions.

[0023] According to the present invention, preferably, in step (3), the carbonization temperature is 500-1200°C, the carbonization time is 0.5-10h, the carbonization atmosphere is an inert gas, and the heating rate is 0.5-10°C / min; preferably, the carbonization temperature is 600-950oC, the carbonization time is 0.5-4h, and the inert gas is nitrogen or argon; further preferably, the carbonization temperature is 850-950°C, and the carbonization time is 0.5-1.5h.

[0024] A ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material is prepared by the above method.

[0025] Preferably, according to the present invention, the microscopic morphology of the ZIF-67 / polypyrrole Schiff base derived carbon interlayer material is coral-like.

[0026] The above-mentioned ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material is used as a separator material for lithium-sulfur batteries.

[0027] According to a preferred embodiment of the present invention, the application method includes the steps of: grinding and mixing ZIF-67 / polypyrrole Schiff base derived carbon interlayer material, Super P and PVDF, adding N-methylpyrrolidone (NMP), mixing thoroughly to obtain a mixed slurry, and then coating it on one side of a polypropylene (PP) diaphragm, and drying to obtain a diaphragm modified with a ZIF-67 / polypyrrole Schiff base derived carbon interlayer. Preferably, the mass ratio of ZIF-67 / polypyrrole Schiff base derived carbon interlayer material, Super P and PVDF is 5 to 7:2 to 4:1; the loading amount of ZIF-67 / polypyrrole Schiff base derived carbon interlayer material in the diaphragm modified with a ZIF-67 / polypyrrole Schiff base derived carbon interlayer is 1 to 1.5 mg / cm 2 .

[0028] According to a preferred embodiment of the present invention, the preparation method of the positive electrode of a lithium-sulfur battery is as follows: sublimed sulfur and Super P are ground and mixed uniformly, and the mixture is calcined to obtain a mixture; the mixture is mixed with PVDF, and NMP is added and mixed uniformly to obtain a uniform slurry; the slurry is evenly coated on one side of an aluminum foil, and the positive electrode of the lithium-sulfur battery is obtained after drying. Preferably, the mass ratio of sublimed sulfur to Super P is 4 to 7:4; the calcination temperature is 155 to 160°C, the calcination time is 10 to 14 hours, and the calcination atmosphere is argon or nitrogen; the mass ratio of the mixture to PVDF is 8 to 10:1; the area loading of S in the lithium-sulfur battery positive electrode is 1 to 2 mg / cm 2 .

[0029] According to the present invention, the negative electrode of the lithium-sulfur battery is lithium; the electrolyte is a mixed solution of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and LiNO3, wherein the solvent is a mixture of dioxolane and ethylene glycol dimethyl ether, the volume ratio of dioxolane and ethylene glycol dimethyl ether is 1:1, the concentration of LiNO3 is 1-3wt%, and the concentration of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is 0.5-2mol / L.

[0030] The present invention has the following technical features and beneficial effects:

[0031] (1) In the present invention, melamine and pyrrole-2-carboxaldehyde undergo an aldehyde-amine reaction, followed by graft copolymerization under the action of an oxidant to prepare a polypyrrole Schiff base polymer. Subsequently, ZIF-67 nanosheets are grown on the surface of the polypyrrole Schiff base polymer through an in situ growth strategy. Finally, coral-like ZIF-67 / polypyrrole Schiff base-derived carbon is synthesized for the first time by a high-temperature heat treatment method. The present method utilizes inexpensive and readily available raw materials, is simple to prepare, is environmentally friendly, and is low-cost, making it suitable for industrial production.

[0032] (2) The ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material of the present invention has a developed pore structure and an ideal specific surface area, a high nitrogen doping amount, and abundant cobalt nanoparticle active sites. As an interlayer material for lithium-sulfur battery separators, it can not only accelerate the Li + It can effectively inhibit the shuttle of lithium polysulfide through the synergistic effect of "physical barrier-chemical adsorption-catalytic conversion". And its high conductivity and uniform pore size distribution can not only improve the electron transfer rate during the redox conversion of polysulfide, but also facilitate the Li + Uniform transmission, thereby inhibiting the growth of lithium dendrites.

[0033] (3) The ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material of the present invention is applied to the interlayer material of lithium-sulfur batteries and exhibits excellent electrochemical properties, including high reversible specific capacity, excellent rate performance and excellent cycle stability, which provides a possibility for the industrialization of lithium-sulfur batteries with high specific capacity and excellent cycle performance.

[0034] (4) The surfactant added during the preparation process of the present invention decomposes during the carbonization process, which increases the carbon interlayer spacing of the ZIF-67 / polypyrrole Schiff base-derived carbon, which is beneficial for the diffusion of the electrolyte and the exposure of the catalyst active sites. The carbonization temperature of the present invention needs to be appropriate. Excessively high temperatures can easily lead to the collapse of the pore structure of the carbon material and a decrease in the specific surface area, which will significantly deteriorate the specific capacity, rate capability, and cycle stability of the assembled lithium-sulfur battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a scanning electron microscope image of the ZIF-67 / polypyrrole Schiff base composite material (sample S-1) prepared in Example 1;

[0036] Figure 2 This is a scanning electron microscope image of the coral-like ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material (sample S-2) prepared in Example 1;

[0037] Figure 3 Nitrogen adsorption-desorption curve (a) and pore size distribution curve (b) of sample S-2;

[0038] Figure 4 The rate performance diagram (a) and cycle stability diagram (b) of the lithium-sulfur battery assembled using sample S-2 as the interlayer;

[0039] Figure 5 This is a scanning electron microscope image of the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material (sample S-3) prepared in Comparative Example 1;

[0040] Figure 6The rate performance diagram (a) and cycle stability diagram (b) of the lithium-sulfur battery assembled using the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material (sample S-4) prepared in Comparative Example 2. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to specific embodiments and drawings, but is not limited thereto.

[0042] Meanwhile, the experimental methods described in the following examples, unless otherwise specified, are conventional methods; the reagents and materials, unless otherwise specified, can be obtained from commercial channels.

[0043] Example 1:

[0044] A method for preparing a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material comprises the following steps:

[0045] (1) Weigh 1.26g of melamine and dissolve it in 60mL of deionized water. Stir the mixture magnetically in an oil bath, heat to 80℃, and stir until fully dissolved to obtain a melamine aqueous solution. Weigh 0.95g of pyrrole-2-carboxaldehyde and add it to the melamine aqueous solution. Stir the mixture magnetically at 80℃ for 30min to form a mixed solution of melamine and pyrrole-2-carboxaldehyde. Measure 1mL of glacial acetic acid and add it to the mixed solution. Continue stirring magnetically at 80℃ for 6h until the solution turns yellow. Measure 0.5mL of pyrrole and add it to the yellow solution. Disperse the pyrrole completely in the solution by ultrasonic vibration. Then transfer the solution to a cold bath at 0℃ and stir mechanically for 20min. Weigh 0.976g of FeCl3·6H2O and dissolve it in 50mL of deionized water. Slowly add the solution to the yellow solution containing pyrrole monomer at 0℃ and continue stirring mechanically for 24h. The obtained suspension was subjected to solid-liquid separation at a centrifugal speed of 8000 r / min, the precipitate was washed by centrifugation with deionized water, and the solid product was freeze-dried to obtain a polypyrrole Schiff base polymer.

[0046] (2) 0.4 g of freeze-dried polypyrrole Schiff base polymer, 0.2 g of CTAB, and 0.6 g of Co(NO3)2·6H2O were added to 60 mL of deionized water and magnetically stirred at room temperature for 20 min. 1.2 g of 2-methylimidazole was added to the mixed solution, and magnetic stirring was continued at room temperature for 2 h. The resulting purple suspension was subjected to solid-liquid separation at a speed of 8000 r / min. The precipitate was centrifuged and washed with deionized water. The solid product was freeze-dried to obtain a ZIF-67 / polypyrrole Schiff base composite.

[0047] (3) The ZIF-67 / polypyrrole Schiff base composite material was heated to 900°C under Ar protection at a heating rate of 5°C / min, carbonized for 1 h, and naturally cooled to room temperature to obtain a black ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material.

[0048] Figure 1 、 2 They are SEM images of the ZIF-67 / polypyrrole Schiff base composite material (sample S-1) prepared in step (2) of this embodiment and the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material (sample S-2) prepared in step (3); Figure 1 and Figure 2 It can be seen that sample S-1 and sample S-2 are nano-flake and coral-like, respectively, with uniform size.

[0049] Figure 3 a and b are the nitrogen adsorption-desorption curve and pore size distribution curve of sample S-2, respectively. It can be calculated that the specific surface area of ​​S-2 is 304.4 m 2 / g, with an average pore size of 4.2nm. The large specific surface area and ideal porous structure can provide more active sites for capturing lithium polysulfides, and the rich porous structure is conducive to rapid ion transfer / diffusion.

[0050] The ZIF-67 / polypyrrole Schiff base derived carbon interlayer material prepared in this embodiment was used to assemble a lithium-sulfur battery. The steps were as follows: sublimed sulfur and Super P were mixed and ground into a uniform mixture at a mass ratio of 6:4, and then transferred to a tube furnace and kept at a constant temperature of 155°C for 12 hours under an Ar atmosphere. After taking out the mixture of sublimated sulfur and Super P, it was mixed with PVDF at a mass ratio of 9:1, and NMP was added and mixed to obtain a uniform slurry. The uniform slurry was evenly coated on one side of the aluminum foil, and then kept in a vacuum oven at 60°C for 12 hours to evaporate the remaining NMP. The aluminum foil loaded with sublimated sulfur was cut into discs with a diameter of 1.2 cm to obtain a lithium-sulfur battery positive electrode (S) with an area loading of approximately 2 mg / cm 2 ). Similarly, ZIF-67 / polypyrrole Schiff base derived carbon, Super P and PVDF were ground in a mass ratio of 6:3:1, and NMP was used as a solvent to finally obtain a uniform slurry. The uniform slurry was evenly coated on one side of a polypropylene (PP) diaphragm (thickness 25 μm), and then the remaining NMP was dried in a vacuum oven at 40 ° C to obtain a diaphragm modified with a ZIF-67 / polypyrrole Schiff base derived carbon interlayer (wherein the loading amount of the ZIF-67 / polypyrrole Schiff base derived carbon interlayer material was 1.1 mg / cm 2). The lithium-sulfur battery positive electrode prepared above, the separator modified with ZIF-67 / polypyrrole Schiff base derived carbon interlayer and the metal lithium negative electrode were added with appropriate amount of electrolyte and assembled into a CR-2032 button-type lithium-sulfur battery in an argon-protected glove box. The electrolyte was a 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution, and the solvent was a mixture of dioxolane and ethylene glycol dimethyl ether (DOL / DME, V DOL / V DME =1:1), and the additive is 2wt% LiNO3.

[0051] Carry out rate performance and cycle stability tests under 1C conditions, such as Figure 4 As shown, the assembled lithium-sulfur battery exhibits good rate performance (0.1C: 1544.3mAh / g; 1C: 1106.4mAh / g; 3C: 911.2mAh / g) and excellent cycle stability (after 300 cycles at 1C, the specific capacity is still 798.2mAh / g).

[0052] Example 2:

[0053] A method for preparing a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material comprises the following steps:

[0054] (1) Weigh 1.26g of melamine and dissolve it in 60mL of deionized water. Stir the mixture magnetically in an oil bath, heat to 80℃, and stir until fully dissolved to prepare a melamine aqueous solution. Weigh 0.95g of pyrrole-2-carboxaldehyde and add it to the melamine aqueous solution. Stir the mixture magnetically at 80℃ for 30min to form a mixed solution of melamine and pyrrole-2-carboxaldehyde. Measure 1mL of glacial acetic acid and add it to the mixed solution. Continue stirring magnetically at 80℃ for 6h until the solution turns yellow. Measure 0.5mL of pyrrole and add it to the yellow solution. Disperse the pyrrole completely in the solution by ultrasonic vibration. Then transfer the solution to a cold bath at 0℃ and stir mechanically for 20min. Weigh 0.976g of FeCl3·6H2O and dissolve it in 50mL of deionized water. Slowly add it to the yellow solution containing pyrrole monomer at 0℃ and continue stirring mechanically for 24h. The obtained suspension was subjected to solid-liquid separation at a centrifugal speed of 8000 r / min, the precipitate was washed by centrifugation with deionized water, and the solid product was freeze-dried to obtain a polypyrrole Schiff base polymer.

[0055] (2) 0.4 g of freeze-dried polypyrrole Schiff base polymer, 0.2 g of CTAB, and 0.6 g of Co(NO3)2·6H2O were added to 60 mL of deionized water and magnetically stirred at room temperature for 20 min. 1.2 g of 2-methylimidazole was added to the mixed solution, and magnetic stirring was continued at room temperature for 2 h. The resulting purple suspension was subjected to solid-liquid separation at a speed of 8000 r / min. The precipitate was centrifuged and washed with deionized water. The solid product was freeze-dried to obtain a ZIF-67 / polypyrrole Schiff base composite.

[0056] (3) The ZIF-67 / polypyrrole Schiff base composite material was heated to 600°C under Ar protection at a heating rate of 5°C / min, carbonized for 1 h, and naturally cooled to room temperature to obtain a black powder.

[0057] A lithium-sulfur battery was assembled using the derived carbon interlayer material prepared in this example according to the method of Example 1, and rate performance and cycle stability tests under 1C conditions were performed. The assembled lithium-sulfur battery exhibited the following rate performance: 0.1C: 1256.5 mAh / g; 1C: 880.3 mAh / g; 3C: 670.5 mAh / g; and cycle stability: after 300 cycles at 1C, the specific capacity was only 610.3 mAh / g.

[0058] Example 3:

[0059] A method for preparing a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material comprises the following steps:

[0060] (1) Weigh 1.26g of melamine and dissolve it in 60mL of deionized water. Stir the mixture magnetically in an oil bath, heat to 80℃, and stir until fully dissolved to prepare a melamine aqueous solution. Weigh 0.95g of pyrrole-2-carboxaldehyde and add it to the melamine aqueous solution. Stir the mixture magnetically at 80℃ for 30min to form a mixed solution of melamine and pyrrole-2-carboxaldehyde. Measure 1mL of glacial acetic acid and add it to the mixed solution. Continue stirring magnetically at 80℃ for 6h until the solution turns yellow. Measure 0.5mL of pyrrole and add it to the yellow solution. Disperse the pyrrole completely in the solution by ultrasonic vibration. Then transfer the solution to a cold bath at 0℃ and stir mechanically for 20min. Weigh 0.976g of FeCl3·6H2O and dissolve it in 50mL of deionized water. Slowly add it to the yellow solution containing pyrrole monomer at 0℃ and continue stirring mechanically for 24h. The obtained suspension was subjected to solid-liquid separation at a centrifugal speed of 8000 r / min, the precipitate was washed by centrifugation with deionized water, and the solid product was freeze-dried to obtain a polypyrrole Schiff base polymer.

[0061] (2) 0.4 g of freeze-dried polypyrrole Schiff base polymer, 0.2 g of CTAB, and 0.6 g of Co(NO3)2·6H2O were added to 60 mL of deionized water and magnetically stirred at room temperature for 20 min. 1.2 g of 2-methylimidazole was added to the mixed solution, and magnetic stirring was continued at room temperature for 2 h. The resulting purple suspension was subjected to solid-liquid separation at a speed of 8000 r / min. The precipitate was centrifuged and washed with deionized water. The solid product was freeze-dried to obtain a ZIF-67 / polypyrrole Schiff base composite.

[0062] (3) The ZIF-67 / polypyrrole Schiff base composite material was heated to 900°C under Ar protection at a heating rate of 5°C / min, carbonized for 4 h, and naturally cooled to room temperature to obtain a black powder.

[0063] A lithium-sulfur battery was assembled using the derived carbon interlayer material prepared in this example according to the method of Example 1, and rate performance and cycle stability tests under 1C conditions were performed. The assembled lithium-sulfur battery exhibited the following rate performance: 0.1C: 1280.4 mAh / g; 1C: 896.7 mAh / g; 3C: 683.5 mAh / g; and cycle stability: after 300 cycles at 1C, the specific capacity was still 702.3 mAh / g.

[0064] Example 4:

[0065] A method for preparing a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material comprises the following steps:

[0066] (1) Weigh 1.26 g of melamine and dissolve it in 60 mL of deionized water. Stir the mixture in an oil bath with magnetic stirring, heat to 80 °C, and stir until fully dissolved to prepare a melamine aqueous solution. Weigh 0.95 g of pyrrole-2-carboxaldehyde and add it to the melamine aqueous solution. Stir the mixture at 80 °C for 30 min to form a mixed solution of melamine and pyrrole-2-carboxaldehyde. Measure 1 mL of glacial acetic acid and add it to the mixed solution. Continue stirring at 80 °C for 6 h until the solution turns yellow. Measure 0.5 mL of pyrrole and add it to the yellow solution. Disperse the pyrrole completely in the solution by ultrasonic vibration. Then transfer the solution to a cold bath at 0 °C and stir mechanically for 20 min. Weigh 0.976 g of FeCl3·6H2O and dissolve it in 50 mL of deionized water. Slowly add the solution to the yellow solution containing pyrrole monomer at 0 °C and continue stirring mechanically for 24 h. The obtained suspension was subjected to solid-liquid separation at a centrifugal speed of 8000 r / min, the precipitate was washed by centrifugation with deionized water, and the solid product was freeze-dried to obtain a polypyrrole Schiff base polymer.

[0067] (2) 0.4 g of freeze-dried polypyrrole Schiff base polymer, 0.2 g of CTAB, and 2 g of Co(NO3)2·6H2O were added to 60 mL of deionized water and magnetically stirred at room temperature for 20 min. 1.2 g of 2-methylimidazole was added to the mixed solution, and magnetic stirring was continued at room temperature for 2 h. The resulting purple suspension was subjected to solid-liquid separation at a speed of 8000 r / min. The precipitate was centrifuged and washed with deionized water. The solid product was freeze-dried to obtain a ZIF-67 / polypyrrole Schiff base composite.

[0068] (3) The ZIF-67 / polypyrrole Schiff base composite material was heated to 900°C under Ar protection at a heating rate of 5°C / min, carbonized for 1 h, and naturally cooled to room temperature to obtain a black powder.

[0069] A lithium-sulfur battery was assembled using the derived carbon interlayer material prepared in this example according to the method of Example 1, and rate performance and cycle stability tests under 1C conditions were performed. The assembled lithium-sulfur battery exhibited the following rate performance: 0.1C: 1422.8 mAh / g; 1C: 979.6 mAh / g; 3C: 805.8 mAh / g; and the cycle stability was as follows: after 300 cycles at 1C, the specific capacity was only 580.5 mAh / g.

[0070] Example 5:

[0071] A method for preparing a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material comprises the following steps:

[0072] (1) Weigh 1.26g of melamine and dissolve it in 60mL of deionized water. Stir the mixture magnetically in an oil bath, heat to 80℃, and stir until fully dissolved to obtain a melamine aqueous solution. Weigh 0.6g of pyrrole-2-carboxaldehyde and add it to the melamine aqueous solution. Stir the mixture magnetically at 80℃ for 30min to form a mixed solution of melamine and pyrrole-2-carboxaldehyde. Measure 1mL of glacial acetic acid and add it to the mixed solution. Continue stirring magnetically at 80℃ for 6h until the solution turns yellow. Measure 0.5mL of pyrrole and add it to the yellow solution. Disperse the pyrrole completely in the solution by ultrasonic vibration. Then transfer the solution to a cold bath at 0℃ and stir mechanically for 20min. Weigh 0.976g of FeCl3·6H2O and dissolve it in 50mL of deionized water. Slowly add the solution to the yellow solution containing pyrrole monomer at 0℃ and continue stirring mechanically for 24h. The obtained suspension was subjected to solid-liquid separation at a centrifugal speed of 8000 r / min, the precipitate was washed by centrifugation with deionized water, and the solid product was freeze-dried to obtain a polypyrrole Schiff base polymer.

[0073] (2) 0.4 g of freeze-dried polypyrrole Schiff base polymer, 0.2 g of CTAB, and 0.6 g of Co(NO3)2·6H2O were added to 60 mL of deionized water and magnetically stirred at room temperature for 20 min. 1.2 g of 2-methylimidazole was added to the mixed solution, and magnetic stirring was continued at room temperature for 2 h. The resulting purple suspension was subjected to solid-liquid separation at a speed of 8000 r / min. The precipitate was centrifuged and washed with deionized water. The solid product was freeze-dried to obtain a ZIF-67 / polypyrrole Schiff base composite.

[0074] (3) The ZIF-67 / polypyrrole Schiff base composite material was heated to 900°C under Ar protection at a heating rate of 5°C / min, carbonized for 1 h, and naturally cooled to room temperature to obtain a black powder.

[0075] A lithium-sulfur battery was assembled using the derived carbon interlayer material prepared in this example according to the method of Example 1, and rate performance and cycle stability tests under 1C conditions were performed. The assembled lithium-sulfur battery exhibited the following rate performance: 0.1C: 1263.2 mAh / g; 1C: 870.5 mAh / g; 3C: 649.7 mAh / g; and the cycle stability was as follows: after 300 cycles at 1C, the specific capacity was only 564.8 mAh / g.

[0076] Comparative Example 1

[0077] A method for preparing a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material is as described in Example 1, except that in step (3), the carbonization temperature is 1300° C., and the remaining steps and conditions are the same as in Example 1.

[0078] The SEM image of the material (sample S-3) prepared in this comparative example is as follows Figure 5 As shown. Figure 5 It can be seen that the sample S-3 has an irregular microstructure as a whole.

[0079] A lithium-sulfur battery was assembled using the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material prepared in this comparative example according to the method of Example 1, and the rate performance and cycle stability under 1C conditions were tested. The assembled lithium-sulfur battery exhibited extremely poor rate performance (0.1C: 1022.4 mAh / g; 1C: 737.3 mAh / g; 3C: 565.7 mAh / g) and extremely poor cycle stability (after 300 cycles at 1C, the specific capacity was only 450.1 mAh / g).

[0080] Comparative Example 2

[0081] A method for preparing a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material is as described in Example 1, except that CTAB is not added in step (2). The remaining steps and conditions are the same as in Example 1.

[0082] The ZIF-67 / polypyrrole Schiff base derived carbon interlayer material prepared in this comparative example was used to assemble a lithium-sulfur battery according to the method of Example 1, and the rate performance and cycle stability under 1C conditions were tested. Figure 6 As shown. Figure 6 It can be seen that the lithium-sulfur battery assembled according to the method of Example 1 using the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material prepared in this comparative example exhibited unsatisfactory rate performance (0.1C: 1229.0 mAh / g; 1C: 795.1 mAh / g; 3C: 597.5 mAh / g) and unsatisfactory cycle performance (after 300 cycles at 1C, the specific capacity was only 519.8 mAh / g).

[0083] The results of the examples show that the preparation method of the present invention is simple and has a unique morphology. The obtained derived carbon interlayer material can enable lithium-sulfur batteries to have a high specific capacity, good rate capability and excellent cycle stability.

Claims

1. A method for preparing a ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material, comprising the steps of: (1) dissolving melamine and pyrrole-2-carboxaldehyde in a solvent to obtain a mixed solution; adding a catalyst to carry out an aldehyde-amine reaction; adding pyrrole, fully dispersing it, adding an oxidant, carrying out an oxidative polymerization reaction, and then performing solid-liquid separation, washing, and drying to obtain a polypyrrole Schiff base polymer; (2) fully dispersing a polypyrrole Schiff base polymer, a surfactant, and a cobalt salt in a solvent, adding 2-methylimidazole, reacting, solid-liquid separation, washing, and drying to obtain a ZIF-67 / polypyrrole Schiff base composite material; (3) The ZIF-67 / polypyrrole Schiff base composite material was carbonized to obtain the ZIF-67 / polypyrrole Schiff base derived carbon interlayer material.

2. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 1, characterized in that: In step (1), one or more of the following conditions are included: i. The solvent is deionized water; ii. A method for preparing a mixed solution comprising the steps of: adding melamine to a solvent and stirring at 60-90° C. until fully dissolved; then adding pyrrole-2-carboxaldehyde and stirring at 60-90° C. for 10-60 minutes to obtain a mixed solution; iii. The catalyst is glacial acetic acid; the mass ratio of melamine to the catalyst is 0.5-3:0.5-2 g / mL; iv. The amide reaction temperature is 60-90° C., the amide reaction time is 1-10 h, and the amide reaction is carried out under stirring conditions.

3. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 2, wherein: The mass ratio of melamine to the volume ratio of the catalyst is 1-1.5:1 g / mL.

4. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 1, wherein: In step (1), the mass ratio of melamine to pyrrole-2-carboxaldehyde is 0.5-3:0.5-2; and the volume ratio of melamine to deionized water is 0.5-3:50-80 g / mL.

5. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 4, characterized in that: The mass ratio of melamine to pyrrole-2-carboxaldehyde is 1.26:0.6-1.2; the volume ratio of melamine to deionized water is 1-1.5:60 g / mL.

6. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 1, characterized in that: In step (1), one or more of the following conditions are included: i. The mass ratio of melamine to pyrrole is 0.5-3:0.1-3 g / mL; ii. The oxidant is an aqueous solution of ferric chloride, wherein the mass concentration of ferric chloride is 0.01-0.1 g / mL; the mass ratio of ferric chloride to pyrrole in the oxidant is 0.2-0.8:0.1-1 g / mL; iii. The temperature of the oxidative polymerization reaction is -5 to 5°C, the time of the oxidative polymerization reaction is 10 to 30 hours, and the oxidative polymerization reaction is carried out under stirring conditions.

7. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 6, characterized in that: Include one or more of the following conditions: i. The mass ratio of melamine to pyrrole is 1-1.5:0.1-1 g / mL; ii. The mass ratio of ferric chloride to pyrrole in the oxidant is 0.5-0.6:0.5 g / mL.

8. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 1, characterized in that: In step (2), one or more of the following conditions are included: i. The cobalt salt is Co(NO3)2·6H2O, the surfactant is cetyltrimethylammonium bromide (CTAB), and the solvent is deionized water; ii. The mass ratio of cobalt salt to 2-methylimidazole is 0.1-3:0.5-2; iii. The reaction temperature is room temperature, the reaction time is 1-3 hours, and the reaction is carried out under stirring conditions.

9. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 8, characterized in that: The mass ratio of cobalt salt to 2-methylimidazole is 0.4-2:1.

2.

10. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 1, characterized in that: In step (2), the mass ratio of the polypyrrole Schiff base polymer, the surfactant and the cobalt salt is 0.1-1:0.1-0.8:0.1-3; and the volume ratio of the polypyrrole Schiff base polymer to deionized water is 0.1-1:60 g / mL.

11. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 10, characterized in that: In step (2), the mass ratio of the polypyrrole Schiff base polymer, the surfactant and the cobalt salt is 0.4:0.2:0.4-2.

12. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 1, wherein: In step (3), the carbonization temperature is 500-1200° C., the carbonization time is 0.5-10 h, the carbonization atmosphere is an inert gas, and the heating rate is 0.5-10° C. / min.

13. The method for preparing the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material according to claim 12, characterized in that: The carbonization temperature is 600-950°C, the carbonization time is 0.5-4h, and the inert gas is nitrogen or argon.

14. A ZIF-67 / polypyrrole Schiff base derived carbon interlayer material, characterized in that: Prepared by the method according to any one of claims 1 to 13.

15. The ZIF-67 / polypyrrole Schiff base derived carbon sandwich material according to claim 14, characterized in that: The microscopic morphology of the ZIF-67 / polypyrrole Schiff base-derived carbon interlayer material is coral-like.

16. The use of the ZIF-67 / polypyrrole Schiff base derived carbon sandwich material according to claim 14, characterized in that: Separator materials for lithium-sulfur batteries.

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