A hydrogen-bonded organic framework material, its preparation method and application

Abstract

A hydrogen-bonded organic framework material of the present invention, its preparation method and application belong to the technical field of energy storage. The hydrogen-bonded organic framework material is 6,6',6''-(diquinoxaline[2,3-a:2',3'-c]phenazine-2,8,14-triacyl)tris(1,3,5-triazine-2,4-diamine), denoted as HOF-HATN; the preparation method is: using cyclohexanehexanone and 3,4-diaminobenzonitrile as raw materials, through Schiff base reaction, the obtained product is refluxed with dicyandiamide and potassium hydroxide in an organic solvent for 48 hours to obtain HOF-HATN; the hydrogen-bonded organic framework material is used as a positive electrode material to prepare an aqueous zinc-ion battery. The present invention has the advantages of easy synthesis, low cost, outstanding battery properties, easy mass production, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and relates to a hydrogen-bonded organic framework containing redox active sites as a cathode material for zinc-ion batteries. The hydrogen network in the hydrogen-bonded organic framework promotes the transport of hydrogen ions, thereby increasing the theoretical capacity of zinc-ion batteries. Background Art

[0002] Energy and environmental issues have always been regarded as the main challenges for maintaining the sustainable development of human society. This problem urgently requires scientists to seek efficient energy conversion devices and reliable energy storage systems with high specific energy, long life, and high safety.

[0003] Rechargeable secondary batteries have proven to be the most promising energy storage systems. As one of the most popular batteries, lithium-ion batteries have achieved great success in powering electronic products and electric vehicles, and are being considered for building energy storage power stations. However, the shortage of transition metal-based inorganic compound electrode materials has bottlenecked the development of commercial lithium-ion batteries. Secondly, high cost and many safety problems have further hindered the large-scale application of lithium-ion batteries. As an emerging and highly promising alternative energy storage system, aqueous zinc-ion batteries have attracted much attention due to their rich natural resources, inherent safety, and low cost.

[0004] Aqueous zinc-ion batteries have great application prospects in electrical energy storage due to their low cost, easy manufacturability, inherent safety, and environmental friendliness. In particular, metallic zinc is a highly compatible metal that can be directly used in aqueous electrolytes and has a large theoretical capacity of 820 mAh g -1and a lower redox potential of -0.76 V. However, the strong Coulomb repulsion between large-sized divalent zinc ions (usually hydrated) and the host lattice results in slow diffusion kinetics and large volume changes, leading to insufficient specific capacity and poor cycling stability. Therefore, the research on zinc-ion batteries is still in the early stage of development. The most commonly used cathode materials for zinc-ion batteries are inorganic electrode materials, and most inorganic materials contain transition metals, which are non-renewable resources and require high-temperature treatment processes. This not only consumes energy but also pollutes the environment. Secondly, the recycling and reuse of inorganic materials face more obstacles. In addition, the ionic radius of divalent zinc ions is relatively large. When zinc ions are inserted and extracted, it will cause irreversible deformation of the lattice of inorganic materials, resulting in stability decay. To overcome this problem, scientists have turned their attention to organic electrode materials. Organic electrode materials often adopt electron-deficient systems, and common functional groups include carbon-nitrogen double bonds, carbon-oxygen double bonds, etc. The structure of organic materials can also be precisely designed at the molecular level, which is very important for improving the performance of rechargeable aqueous zinc-organic batteries. However, organic electrode materials also have inherent disadvantages, that is, their poor conductivity, which is also the reason why the capacity of most organic electrode materials is relatively low. In addition, there is still controversy about the reaction mechanism of zinc-ion batteries. Zinc-ion batteries often use aqueous (ZnSO4, ZnOTF, ZnCl2, Zn(CH3COO)2, etc.) salt solutions as electrolytes, and these salt solutions tend to be acidic, which leads to the insertion of not only Zn 2+ but also H + during the reaction of zinc-ion batteries. According to previous reports, electrode materials can be roughly divided into three cases: only Zn 2+ is inserted; only H + is inserted; the co-insertion mode of Zn 2+ and H + . However, compared with Zn 2+ ions, H + is superior to Zn 2+ in reaction kinetics due to its small ionic radius and light atomic mass. Therefore, based on this principle, electrode materials favorable for H + insertion can be purposefully designed, which can effectively improve the capacity of the battery.

[0005] Hydrogen-bonded organic frameworks are a new type of crystalline multifunctional material, self-assembled from different organic building blocks (or metal-hydrogen-bonded organic frameworks (metal-organic components) and metal-organic cages) through non-covalent hydrogen-bonding interactions. The size and shape of the internal pores can be regulated by molecular design, and the chemical environment inside these pores can be used for some potential applications, such as storage, sensing, catalysis, etc. More importantly, the hydrogen network in hydrogen-bonded organic frameworks is conducive to the conduction of H + and increases the electrode's affinity for H+ Storage Summary of the Invention

[0006] The technical problem to be solved by the present invention is to improve the problems commonly existing in most current organic and inorganic electrode materials, such as low capacity, poor cycle stability, and unstable rate performance. Provided is a hydrogen-bonded organic framework material that can be used as a cathode material for zinc-ion batteries and a preparation method thereof.

[0007] The above technical problem is achieved through the following technical solutions:

[0008] A hydrogen-bonded organic framework material is 6,6',6”-(diquinoxaline[2,3-a:2',3'-c]phenazine-2,8,14-triacyl)tris(1,3,5-triazine-2,4-diamine), denoted as HOF-HATN, and the structure is as follows:

[0009]

[0010] A preparation method of a hydrogen-bonded organic framework material comprises the following steps:

[0011] 1) Using compound 1 and compound 2 as raw materials, through a Schiff base reaction, reflux at 140°C for 40 hours in acetic acid solution to synthesize compound 3. Compound 1 is cyclohexanehexone, and compound 2 is 3,4-diaminobenzonitrile; the structural formula of compound 3 is as follows:

[0012]

[0013] 2) Compound 3, compound 4, and potassium hydroxide are refluxed in an organic solvent for 48 hours, and the reaction is carried out in an inert gas atmosphere to obtain compound 5, namely HOF-HATN; due to the action of hydrogen bonds between molecules, a hydrogen-bonded organic framework HOF-HATN is formed; the organic solvent is selected from 2-methoxyethanol, DMSO, methanol, DMF, or THF, and compound 4 is dicyandiamide;

[0014] 3) Pour the obtained compound 5 into methanol, and the filtered product is washed thoroughly with boiling water and methanol, and dried under vacuum at 100°C to obtain the hydrogen-bonded organic framework material.

[0015] Preferably, in step 1), the molar ratio of compound 1 to compound 2 is 1:4, and the whole reaction is carried out in a nitrogen atmosphere.

[0016] Preferably, in step 2), the reaction is carried out in nitrogen, and the excess of compound 4 is the key to ensuring the successful progress of the reaction; the whole reaction process should avoid contact with air to prevent the oxidation of amino groups.

[0017] Application of a hydrogen-bonded organic framework material, which is used as a positive electrode material to prepare an aqueous zinc-ion battery, has the following steps:

[0018] 1) Mix HOF-HATN, acetylene black, and PVDF or CMC in a mass ratio of 4:5:1, add the solvent NMP or H2O, grind into a uniform slurry, and then coat it on a titanium foil using a coater;

[0019] 2) Place the coated titanium foil in an oven at 85°C for 12 hours to remove the residual solvent;

[0020] 3) Cut the dried titanium foil in step 2) into circular electrode sheets with a diameter of 12 mm for standby;

[0021] 4) Assembly of the battery: Adopt the standard of 2032 type button battery. Place the circular electrode sheet, separator, electrolyte, zinc sheet, gasket, spring sheet, and positive electrode shell in the negative electrode shell in sequence, and then encapsulate it with a sealing machine to obtain a 2032 type button battery for aqueous zinc ions. Then, perform constant current charge and discharge tests using a BlueTEC battery test system.

[0022] Preferably, in step 4), the electrolyte is an aqueous solution of ZnSO4 with a concentration of 1 M and a volume of 120 μL, and the separator is a glass fiber membrane.

[0023] Beneficial effects:

[0024] 1. The synthesized HOF-HATN of the present invention has good crystallinity, shows high capacity and good stability as the positive electrode material of the zinc-ion battery. At a current density of 50 mA g -1 , it shows a capacity of about 300 mAh g -1 . Even at a current density of 5 A g -1 , it can continuously cycle 10,000 times without obvious attenuation.

[0025] 2. As the positive electrode material of the zinc-ion battery, HOF-HATN can adsorb both Zn 2+ and H + . After calculation, 78% of the capacity of HOF-HATN comes from the insertion of H + , and the rest comes from the insertion of Zn 2+ . It is precisely due to the insertion of hydrogen ions that HOF-HATN has a high specific capacity.

[0026] 3. The HOF-HATN material of the present invention is easy to synthesize, has low cost, outstanding battery properties, and is easy to mass-produce. Description of the drawings

[0027] Figure 1 It is the FTIR diagram of the hydrogen-bonded organic framework HOF-HATN;

[0028] Figure 2 is the NMR chart of the hydrogen-bonded framework HOF-HATN;

[0029] Figure 3 is the XRD chart of the hydrogen-bonded organic framework HOF-HATN;

[0030] Figure 4 is the SEM chart of the hydrogen-bonded organic framework HOF-HATN;

[0031] Figure 5 is the charge-discharge curve of the hydrogen-bonded organic framework HOF-HATN as an electrode material for a zinc-ion battery at a current density of 50 mAh g -1 ;

[0032] Figure 6 is the rate chart of the hydrogen-bonded organic framework HOF-HATN as an electrode material for a zinc-ion battery;

[0033] Figure 7 is the cycle chart of the hydrogen-bonded organic framework HOF-HATN as an electrode material for a zinc-ion battery at a current density of 5 A g -1 ;

[0034] Figure 8 is the cyclic voltammetry curve chart of the hydrogen-bonded framework HOF-HATN as an electrode material for a zinc-ion battery;

[0035] Figure 9 is the impedance chart of the hydrogen-bonded organic framework HOF-HATN as an electrode material for a zinc-ion battery. Specific embodiments

[0036] The present invention provides a conjugated organic zinc-ion battery electrode material, and the electrode material is a hydrogen-bonded organic framework (HOF-HATN). The synthesis route of the hydrogen-bonded organic framework zinc-ion battery electrode material (HOF-HATN) is as follows:

[0037] Using cyclohexanehexone (denoted as compound 1) and 3,4-diaminobenzonitrile (denoted as compound 2) as raw materials, refluxing in acetic acid to synthesize compound 3

[0038]

[0039] Compound 3 is refluxed with dicyandiamide (compound 4) and potassium hydroxide in 2-methoxyethanol to obtain compound 5. Due to the action of intermolecular hydrogen bonds, a hydrogen network connected "head-to-head" is formed.

[0040]

[0041] Example 1

[0042] 1) Cyclohexanehexone (312 mg, 1 mmol) and 3,4-diaminobenzonitrile (532.6 mg, 4 mmol) were added to anhydrous acetic acid (60 mL) under a nitrogen atmosphere, and then refluxed at 140 °C for 40 h. After cooling to room temperature, the mixture was poured into water, then filtered and thoroughly washed with deionized water to remove the excess acid, and a light yellowish green solid (denoted as Compound 3) was collected. Finally, the obtained product was dried under vacuum at 100 °C (yield 82%).

[0043] 2) A mixture of Compound 3 (200 mg, 0.44 mmol), dicyandiamide (420.99 mg, 5.01 mmol) and potassium hydroxide (49.36 mg, 0.88 mmol) was added to a two-necked flask, 2-methoxyethanol (20 mL) was added thereto, and the mixture was stirred under a nitrogen atmosphere and refluxed at 140 °C for 48 h.

[0044] 3) After the obtained mixture was cooled to room temperature, it was filtered, washed thoroughly with boiling water and methanol, and then dried under vacuum at 100 °C to obtain a brown powdery solid, which was the hydrogen-bonded framework HOF-HATN. The obtained material was characterized by FTIR, NMR, XRD, and SEM, and the results are as Figures 1 to 4 shown, proving that HOF-HATN was successfully synthesized.

[0045] Example 2

[0046] The HOF-HATN synthesized in Example 1 was used as the positive electrode material of a zinc-ion battery to prepare an aqueous zinc-ion battery: HOF-HATN, acetylene black, PVDF or CMC were added in a mass ratio of 4:5:1, and ground into a uniform slurry with a solvent NMP, and then coated on a titanium foil using a coater, and then placed in an oven at 85 °C for 12 hours to remove the residual solvent, and cut into circular electrode sheets with a diameter of 12 mm for standby; according to the standard of 2032-type button battery, a circular electrode sheet, a separator, an electrolyte, a zinc sheet, a gasket, a spring piece, and a positive electrode shell were sequentially placed in the negative electrode shell, and then sealed with a sealing machine to obtain a 2032-type button battery for aqueous zinc ions, and then a constant current charge-discharge test was carried out using a blue electrochemical battery test system. From Figure 5 the charge-discharge curve, it can be seen that the battery prepared by the present invention exhibits a specific capacity of 300 mAh g -1 at a current density of 50 mA g -1 . At the same time, the rate performance of the HOF-HATN electrode was tested at different current densities. When the current density reached 2 A g -1 , the capacity could still reach 80 mAh g -1 . When the current returned to 100 mA g -1 again, the capacity could almost return to the initial capacity. At 5 A g-1 The stability of the battery was tested at a current density of, and the results are as follows Figure 7 shown. After 10,000 cycles, the cycle capacity hardly decreased. According to Figure 8 the CV curve shown, two pairs of obvious redox peaks can be seen, representing two redox processes. The reduction peak of HOF-HATN appearing at about 0.8 V corresponds to the insertion of one Zn 2+ , and then the reduction peak at about 0.4 V corresponds to the insertion of H + . To study the kinetic behavior of the battery, impedance tests were carried out on the battery, and the results are as follows Figure 9 shown. After cycling different numbers of times, the impedance increased slightly, which was caused by the deposition of some by-products on the electrode surface.

Claims

1. A hydrogen-bonded organic framework material, characterized in that, The hydrogen-bonded organic framework material described above is 6,6',6''-(diquinoxaline[2,3-a:2',3'-c]phenazine-2,8,14-triacyl)tris(1,3,5-triazine-2,4-diamine), denoted as HOF-HATN, and its structure is as follows:

2. A preparation method of the hydrogen-bonded organic framework material according to claim 1, comprising the following steps: 1) Using compound 1 and compound 2 as raw materials, through a Schiff base reaction, reflux at 140 °C in acetic acid solution for 40 hours to synthesize compound 3. Compound 1 is cyclohexanehexone, and compound 2 is 3,4-diaminobenzonitrile. The structural formula of compound 3 is as follows: 2) Compound 3, compound 4, and potassium hydroxide are refluxed in an organic solvent for 48 hours. The reaction is carried out in an inert gas atmosphere to obtain compound 5, namely HOF-HATN. Due to the action of hydrogen bonds between molecules, the hydrogen-bonded organic framework HOF-HATN is formed. The organic solvent is selected from 2-methoxyethanol, DMSO, methanol, DMF, or THF, and compound 4 is dicyandiamide. 3) Pour the obtained compound 5 into methanol, and the filtered product is thoroughly washed with boiling water and methanol, and dried in vacuo at 100 °C to obtain the hydrogen-bonded organic framework material.

3. The preparation method of a hydrogen-bonded organic framework material according to claim 2, wherein, In step 1), the molar ratio of compound 1 to compound 2 is 1:4, and the whole reaction is carried out in a nitrogen atmosphere.

4. The preparation method of a hydrogen-bonded organic framework material according to claim 2, characterized in that, In step 2), the reaction is carried out in nitrogen, and compound 4 is in excess; the whole reaction process avoids contact with air.

5. An application of the hydrogen-bonded organic framework material according to claim 1, which is used as a positive electrode material to prepare an aqueous zinc-ion battery, comprising the following steps: 1) Add HOF-HATN, acetylene black, PVDF, or CMC to the solvent NMP or H2O in a mass ratio of 4:5:1 and grind them into a uniform slurry, and then coat it on a titanium foil using a coater. 2) Place the coated titanium foil in an oven at 85 °C for 12 hours to remove the residual solvent. 3) Cut the titanium foil dried in step 2) into circular electrode sheets with a diameter of 12 mm for standby. 4) Assembly of the battery: Adopt the standard of 2032-type button battery. Place the circular electrode sheet, separator, electrolyte, zinc sheet, gasket, spring sheet, and positive electrode shell in the negative electrode shell in sequence, and then seal it with a packaging machine to obtain a 2032-type button battery for aqueous zinc ions. Then, perform a constant current charge-discharge test using a blue electrochemical battery test system.

6. The application of a hydrogen-bonded organic framework material according to claim 5, wherein In step 4), the electrolyte is an aqueous solution of ZnSO4 with a concentration of 1 M and a volume of 120 μL, and the separator is a glass fiber membrane.

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