Preparation method of metal organic framework diaphragm

Abstract

The invention belongs to the technical field of sodium-ion battery diaphragms, and particularly discloses a preparation method of a metal organic framework diaphragm, and the preparation method comprises the following steps: S1, preparing hierarchical pore MIL-101-Fe; and S2, preparing the MIL-101-Fe / PP diaphragm. According to the preparation method of the metal organic framework diaphragm provided by the invention, the prepared metal organic framework diaphragm is applied to a sodium ion battery, and the ion migration rate and the ion conductivity can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium ion battery diaphragms, and in particular relates to a method for preparing a metal organic framework diaphragm. Background Art

[0002] Sodium-ion batteries are secondary batteries (rechargeable batteries) that work similarly to lithium-ion batteries, relying mainly on the movement of sodium ions between the positive and negative electrodes. Sodium-ion batteries are mainly composed of positive and negative electrode materials, electrolytes, separators, and positive and negative electrode shells.

[0003] With the rapid development of sodium battery technology, the development of sodium-ion batteries with higher energy density is imperative. High-energy-density sodium-ion batteries require higher ion transfer rates. The sodium ion migration rate and ion conductivity of the sodium battery separator directly affect the electrochemical performance and safety performance of the sodium-ion battery. However, the sodium ion migration rate and ion conductivity of the current sodium battery separator are not ideal. Therefore, there is an urgent need for a separator with high ion migration rate and ion conductivity, while meeting thermal stability and corrosion resistance, and good electrolyte wettability. Summary of the invention

[0004] The purpose of the present invention is to overcome the above problems existing in the prior art and provide a method for preparing a metal organic framework membrane. The prepared metal organic framework membrane is applied to sodium ion batteries to improve the ion migration rate and ion conductivity.

[0005] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0006] A method for preparing a metal organic framework membrane, the method comprising the following steps:

[0007] S1: Preparation of multi-level pore MIL-101-Fe

[0008] Add iron salt and terephthalic acid to N, N-dimethylformamide, then add deionized water, stir evenly to prepare a mixed solution, transfer the mixed solution to a microwave reactor for crystallization for 8-24 hours to prepare a brown-yellow colloid, cool the microwave reactor to room temperature, take out the brown-yellow colloid in the microwave reactor, wash the brown-yellow colloid with N, N-dimethylformamide solution and methanol solution respectively, transfer to a constant temperature box for drying after washing, and obtain multi-level porous MIL-101-Fe after drying;

[0009] S2: Preparation of MIL-101-Fe / PP separator

[0010] The multi-level porous MIL-101-Fe was placed in a PVDF-HFP / NMP solution and stirred thoroughly to form a mixed uniform liquid. The mixed uniform liquid was coated on a polypropylene diaphragm and dried to prepare a MIL-101-Fe / PP diaphragm.

[0011] Further, in step S1, the iron salt is FeCl 3 -6H 2 O, Fe 2 (SO 4 ) 3 -9H 2 O, Fe(NO 3 ) 3 -9H 2 O and Fe(CH 3 COO 2 -4H 2 Any one or more of O can be mixed in any proportion.

[0012] Further, in the mixed solution, the molar concentration ratio of the iron salt to terephthalic acid is 2:(1-2);

[0013] In the mixed solution, the molar concentration of terephthalic acid is 0.10-0.20 mol / L.

[0014] Furthermore, in the mixed solution, the volume ratio of deionized water to N,N-dimethylformamide is (0.05-0.67):1.

[0015] Furthermore, during the crystallization process in the microwave reactor, the crystallization temperature is 120-200°C.

[0016] Furthermore, in step S1, the brown-yellow colloid is washed with N,N-dimethylformamide solution and methanol solution respectively. The specific process is: first, the brown-yellow colloid is washed with N,N-dimethylformamide solution for 3 times, and then washed with methanol solution for 3 times.

[0017] Furthermore, in step S1, during the drying process in the constant temperature oven, the drying temperature is 100-150° C. and the drying time is 8-12 hours.

[0018] Furthermore, in step S2, in the mixed homogeneous solution, the mass ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution is (1-3): (0.5-2).

[0019] Furthermore, the mass concentration of the PVDF-HFP / NMP solution is 5-10%.

[0020] Furthermore, in step S2, the drying temperature is 50-70°C.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention provides a method for preparing a metal organic framework diaphragm, in which a layer of MIL-101-Fe functional coating containing a multi-level porous metal organic framework structure is coated on the surface of a polypropylene diaphragm. Since the nanochannels inside the metal organic framework material MOF and the intergranular channels with negative charges will limit the migration of anions, the migration number of sodium ions in the prepared diaphragm is increased, thereby increasing the sodium ion migration rate and ionic conductivity, and improving the rate performance of the battery.

[0023] 2. The present invention provides a method for preparing a metal organic framework diaphragm. During the preparation process, a microwave reactor is used for crystallization. The non-contact heating characteristics of microwave radiation are used to help achieve uniform heating of the reaction system, thereby improving the quality and crystallinity of the product. Microwave heating can complete the synthesis reaction at a lower temperature and in a shorter time. Compared with traditional hydrothermal or solvent thermal methods, microwave-assisted synthesis is more efficient and energy-saving. The microwave-assisted synthesis product can be more easily separated from the reaction system, and there are almost no by-products, thereby simplifying the processing steps.

[0024] 3. The present invention provides a method for preparing a metal organic framework diaphragm. The prepared diaphragm has the characteristics of good thermal stability, good corrosion resistance, etc., and also has good electrolytic wettability. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention provides a method for preparing a metal organic framework membrane, the preparation method comprising the following steps:

[0027] S1: Preparation of multi-level pore MIL-101-Fe

[0028] Adding iron salt and terephthalic acid to N,N-dimethylformamide, adding deionized water, stirring evenly, to prepare a mixed solution; wherein the molar concentration ratio of the iron salt to the terephthalic acid in the mixed solution is 2:(1-2);

[0029] In the mixed solution, the molar concentration of terephthalic acid is 0.10-0.20 mol / L;

[0030] In the mixed solution, the volume ratio of deionized water and N, N-dimethylformamide is (0.05-0.67):1;

[0031] Iron salt is FeCl 3 -6H 2 O, Fe 2 (SO 4 ) 3 -9H 2 O, Fe(NO 3 ) 3 -9H 2 O and Fe(CH 3 COO 2 -4H 2 Any one or more of O are mixed in any proportion;

[0032] The mixed solution was transferred to a microwave reactor and crystallized at 120-200° C. for 8-24 h to obtain a brown-yellow colloid;

[0033] The microwave reactor was cooled to room temperature, and the brown-yellow colloid in the microwave reactor was taken out. The brown-yellow colloid was first washed with N,N-dimethylformamide solution for 3 times, and then washed with methanol solution for 3 times;

[0034] After washing, the mixture was transferred to a thermostatic oven and dried at 100-150°C for 8-12 hours to obtain multi-level porous MIL-101-Fe;

[0035] S2: Preparation of MIL-101-Fe / PP separator

[0036] The multi-level porous MIL-101-Fe is placed in a PVDF-HFP / NMP solution with a mass concentration of 5-10%, and stirred thoroughly to form a mixed uniform solution;

[0037] Wherein, in the mixed homogeneous solution, the mass ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution is (1-3): (0.5-2), preferably (0.55-0.60): 1;

[0038] The mixed uniform liquid was coated on a polypropylene diaphragm and dried at 50-70° C. to prepare a MIL-101-Fe / PP diaphragm.

[0039] The following are specific examples. In the following examples, unless otherwise specified, all raw materials can be obtained from commercial sources.

[0040] Example 1

[0041] This embodiment provides a method for preparing a metal organic framework membrane, and the preparation method comprises the following steps:

[0042] S1: Preparation of multi-level pore MIL-101-Fe

[0043] 2.5 mmol FeCl 3 -6H 2 O, 2.5mmol terephthalic acid, added to 15ml N,N-dimethylformamide, then added 5ml deionized water, after stirring evenly, transferred to a microwave reactor equipped with microwave assistance, crystallized at 120°C for 24h to prepare a brown-yellow colloid; after the reactor was cooled to room temperature, the obtained brown-yellow colloid was washed three times with N'N-dimethylformamide solution and methanol solution respectively, transferred to a 100°C constant temperature box, and dried for 12h to obtain multi-level porous MIL-101-Fe;

[0044] S2: Preparation of MIL-101-Fe / PP separator

[0045] The multi-level porous MIL-101-Fe was placed in a PVDF-HFP / NMP solution with a mass concentration of 7%, wherein the weight ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution was 55%, and stirred thoroughly to form a mixed uniform liquid. The mixed uniform liquid was then coated on a PP diaphragm with a coating machine, and after being fully dried at 50°C, a MIL-101-Fe / PP diaphragm was prepared.

[0046] Example 2

[0047] This embodiment provides a method for preparing a metal organic framework membrane, and the preparation method comprises the following steps:

[0048] S1: Preparation of multi-level pore MIL-101-Fe

[0049] 20mmol Fe(NO 3 ) 3 -9H 2 O, 15mmol terephthalic acid, added to 60ml N,N-dimethylformamide, then added 10ml deionized water, after stirring evenly, transferred to a microwave reactor equipped with microwave assistance, crystallized at 140°C for 24h to prepare a brown-yellow colloid; after the reactor was cooled to room temperature, the obtained brown-yellow colloid was washed three times with N'N-dimethylformamide solution and methanol solution respectively, and then transferred to a 100°C constant temperature box and dried for 6h to obtain multi-level porous MIL-101-Fe;

[0050] S2: Preparation of MIL-101-Fe / PP separator

[0051] The multi-level porous MIL-101-Fe was placed in a PVDF-HFP / NMP solution with a mass concentration of 7%, wherein the weight ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution was 58%, and stirred thoroughly to form a mixed uniform liquid. The mixed uniform liquid was then coated on a PP diaphragm with a coating machine, and after being fully dried at 50°C, a MIL-101-Fe / PP diaphragm was prepared.

[0052] Example 3

[0053] This embodiment provides a method for preparing a metal organic framework membrane, and the preparation method comprises the following steps:

[0054] S1: Preparation of multi-level pore MIL-101-Fe

[0055] 30mmol Fe(NO 3 ) 3 -9H 2 O, 15mmol terephthalic acid, added to 100ml N,N-dimethylformamide, then added 10ml deionized water, after stirring evenly, transferred to a microwave reactor equipped with microwave assistance, crystallized at 130°C for 10h, and a brown-yellow colloid was prepared; after the reactor was cooled to room temperature, the brown-yellow colloid was washed three times with N'N-dimethylformamide solution and methanol solution respectively, and then transferred to a 100°C thermostat and dried for 6h to obtain multi-level porous MIL-101-Fe;

[0056] S2: Preparation of MIL-101-Fe / PP separator

[0057] The multi-level porous MIL-101-Fe was placed in a PVDF-HFP / NMP solution with a mass concentration of 8%, wherein the weight ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution was 56%, and stirred thoroughly to form a mixed uniform liquid. The mixed uniform liquid was then coated on a PP diaphragm with a coating machine, and after being fully dried at 50°C, a MIL-101-Fe / PP diaphragm was prepared.

[0058] Example 4

[0059] This embodiment provides a method for preparing a metal organic framework membrane, and the preparation method comprises the following steps:

[0060] S1: 40 mmol FeCl 3 -6H 2O, 30mmol terephthalic acid, added to 150ml N,N-dimethylformamide, then added 50ml deionized water, after stirring evenly, transferred to a microwave reactor equipped with microwave assistance, crystallized at 160°C for 16h to prepare a brown-yellow colloid; after the reactor was cooled to room temperature, the obtained brown-yellow colloid was washed three times with N'N-dimethylformamide solution and methanol solution respectively, and then transferred to a 120°C constant temperature box and dried for 10h to obtain multi-level porous MIL-101-Fe;

[0061] S2: Preparation of MIL-101-Fe / PP separator

[0062] The multi-level porous MIL-101-Fe was placed in a PVDF-HFP / NMP solution with a mass concentration of 8%, wherein the weight ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution was 60%, and stirred thoroughly to form a mixed uniform liquid. The mixed uniform liquid was then coated on a PP diaphragm with a coating machine, and after being fully dried at 60°C, a MIL-101-Fe / PP diaphragm was prepared.

[0063] Example 5

[0064] This embodiment provides a method for preparing a metal organic framework membrane, and the preparation method comprises the following steps:

[0065] S1: 21mmol FeCl 3 -6H 2 O, 21mmol terephthalic acid, added to 200ml N,N-dimethylformamide, then added 10ml deionized water, after stirring evenly, transferred to a microwave reactor equipped with microwave assistance, crystallized at 120°C for 24h, and a brown-yellow colloid was prepared; after the reactor was cooled to room temperature, the brown-yellow colloid was washed three times with N'N-dimethylformamide solution and methanol solution respectively, and then transferred to a 100°C thermostat and dried for 12h to obtain multi-level porous MIL-101-Fe;

[0066] S2: Preparation of MIL-101-Fe / PP separator

[0067] The multi-level porous MIL-101-Fe was placed in a PVDF-HFP / NMP solution with a mass concentration of 5%, wherein the weight ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution was 60%, and stirred thoroughly to form a mixed uniform liquid. The mixed uniform liquid was then coated on a PP diaphragm with a coating machine, and after being fully dried at 50°C, a MIL-101-Fe / PP diaphragm was prepared.

[0068] Example 6

[0069] This embodiment provides a method for preparing a metal organic framework membrane, and the preparation method comprises the following steps:

[0070] S1: 66.8 mmol FeCl 3 -6H 2 O, 33.4mmol terephthalic acid, added to 100ml N,N-dimethylformamide, then added 67ml deionized water, after stirring evenly, transferred to a microwave reactor equipped with microwave assistance, crystallized at 200℃ for 8h, and prepared a brown-yellow colloid; after the reactor was cooled to room temperature, the obtained brown-yellow colloid was washed three times with N'N-dimethylformamide solution and methanol solution respectively, and then transferred to a 150℃ constant temperature box and dried for 8h to obtain multi-level porous MIL-101-Fe;

[0071] S2: Preparation of MIL-101-Fe / PP separator

[0072] The multi-level porous MIL-101-Fe was placed in a PVDF-HFP / NMP solution with a mass concentration of 10%, wherein the weight ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution was 1:2, and stirred thoroughly to form a mixed uniform liquid. The mixed uniform liquid was then coated on a PP diaphragm with a coating machine, and after being fully dried at 70°C, a MIL-101-Fe / PP diaphragm was prepared.

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing a metal organic framework membrane, and the preparation method comprises the following steps:

[0075] S1: 40 mmol FeCl 3 -6H 2 O, 30mmol terephthalic acid, added to 150ml N, N-dimethylformamide, then added 50ml deionized water, after stirring evenly, transferred to a polytetrafluoroethylene liner, and hydrothermally crystallized at 160℃ for 16h to prepare a brown-yellow colloid; after the reactor was cooled to room temperature, the obtained brown-yellow colloid was washed three times with N'N-dimethylformamide solution and methanol solution respectively, and then transferred to a 120℃ constant temperature box and dried for 10h to obtain multi-level porous MIL-101-Fe;

[0076] S2: Preparation of MIL-101-Fe / PP separator

[0077] The multi-level porous MIL-101-Fe was placed in a PVDF-HFP / NMP solution with a mass concentration of 8%, wherein the weight ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution was 60%, and stirred thoroughly to form a mixed uniform liquid. The mixed uniform liquid was then coated on a PP diaphragm with a coating machine, and after being fully dried at 60°C, a MIL-101-Fe / PP diaphragm was prepared.

[0078] Comparative Example 2

[0079] The comparative example provides a conventional polymer base film material PP diaphragm with a pore size of 0.2, a porosity of 32%, and a base film thickness of 16 μm.

[0080] Experimental example

[0081] The ion migration rate of the MIL-101-Fe / PP membrane prepared in the above examples and comparative examples was evaluated by an electrochemical method, and the ion migration number was calculated by the classic Bruce-Vincent method; and the conductivity was measured by impedance testing. The results are shown in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] Compared with the prior art, the ion migration number of the prior art diaphragm is 0.25-0.40 and the conductivity is 0.5-0.8ms / cm;

[0086] It can be seen from the data in Table 1 that the ion migration number and conductivity of the MIL-101-Fe / PP diaphragm prepared in the embodiment are significantly improved compared with the prior art;

[0087] Specifically, it can be seen from Example 4 and Comparative Example 1 that Comparative Example 1 adopts a hydrothermal method to prepare the multi-level porous MIL-101-Fe, and Example 4 adopts a microwave-assisted heating method, and its ion migration number and conductivity are improved compared with Comparative Example 1, indicating that the microwave-assisted heating method can not only shorten the crystallization time and improve the crystallization efficiency, but also improve the thermal stability of the prepared diaphragm; moreover, microwave-assisted heating also has the advantages of high efficiency and energy saving.

[0088] The invention provides a method for preparing a metal organic framework diaphragm. A layer of MIL-101-Fe functional coating containing a multi-level porous metal organic framework structure is coated on the surface of a polypropylene diaphragm. Since nanochannels inside the metal organic framework material MOF and intergranular channels with negative charges limit the migration of anions, the migration number of sodium ions in the prepared diaphragm is increased, thereby increasing the sodium ion migration rate and ion conductivity, and improving the rate performance of the battery.

[0089] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0090] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a metal organic framework membrane, characterized in that: The preparation method comprises the following steps: S1: Preparation of multi-level pore MIL-101-Fe Add iron salt and terephthalic acid to N, N-dimethylformamide, then add deionized water, stir evenly to prepare a mixed solution, transfer the mixed solution to a microwave reactor for crystallization for 8-24 hours to prepare a brown-yellow colloid, cool the microwave reactor to room temperature, take out the brown-yellow colloid in the microwave reactor, wash the brown-yellow colloid with N, N-dimethylformamide solution and methanol solution respectively, transfer to a constant temperature box for drying after washing, and obtain multi-level porous MIL-101-Fe after drying; S2: Preparation of MIL-101-Fe / PP separator The multi-level porous MIL-101-Fe was placed in a PVDF-HFP / NMP solution and stirred thoroughly to form a mixed uniform liquid. The mixed uniform liquid was coated on a polypropylene diaphragm and dried to prepare a MIL-101-Fe / PP diaphragm.

2. The method for preparing a metal organic framework membrane according to claim 1, characterized in that: In step S1, the iron salt is any one or more of FeCl3-6H2O, Fe2(SO4)3-9H2O, Fe(NO3)3-9H2O and Fe(CH3COO)2-4H2O mixed in any proportion.

3. The method for preparing a metal organic framework membrane according to claim 1, characterized in that: In the mixed solution, the molar concentration ratio of the iron salt to terephthalic acid is 2:(1-2); In the mixed solution, the molar concentration of terephthalic acid is 0.10-0.20 mol / L.

4. The method for preparing a metal organic framework membrane according to claim 1, characterized in that: In the mixed solution, the volume ratio of deionized water to N,N-dimethylformamide is (0.05-0.67):

1.

5. The method for preparing a metal organic framework membrane according to claim 1, characterized in that: During the crystallization process in the microwave reactor, the crystallization temperature is 120-200°C.

6. The method for preparing a metal organic framework membrane according to claim 1, characterized in that: In step S1, the brown-yellow colloid is washed with N,N-dimethylformamide solution and methanol solution respectively. The specific process is as follows: the brown-yellow colloid is first washed with N,N-dimethylformamide solution for 3 times, and then washed with methanol solution for 3 times.

7. The method for preparing a metal organic framework membrane according to claim 1, characterized in that: In step S1, during the drying process in the constant temperature oven, the drying temperature is 100-150°C and the drying time is 8-12 hours.

8. The method for preparing a metal organic framework membrane according to claim 1, characterized in that: In step S2, in the mixed homogeneous solution, the mass ratio of the multi-level porous MIL-101-Fe to the PVDF-HFP / NMP solution is (1-3): (0.5-2).

9. The method for preparing a metal organic framework membrane according to claim 1, characterized in that: The mass concentration of the PVDF-HFP / NMP solution is 5-10%.

10. The method for preparing a metal organic framework membrane according to claim 1, characterized in that: In step S2, the drying temperature is 50-70°C.

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