CN112717731B

CN112717731B - Ion conductive film and preparation method thereof

Info

Publication number: CN112717731B
Application number: CN201911035114.9A
Authority: CN
Inventors: 蒋峰景; 周新杰; 钟宇光; 钟春燕
Original assignee: Shanghai Jiaotong University; Hainan Yeguo Foods Co Ltd
Current assignee: Shanghai Jiaotong University; Hainan Yeguo Foods Co Ltd
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2023-01-06
Anticipated expiration: 2039-10-29
Also published as: CN112717731A

Abstract

The invention provides an ion conductive film and a preparation method thereof, wherein the method comprises the following steps: a1: adding the ionic liquid into the sulfonated polymer solution to prepare a membrane casting solution; a2: casting the casting solution on a flat plate, and then drying to obtain a composite film; a3: and washing away the ionic liquid in the composite membrane, and then drying to obtain the porous membrane. The composite porous membrane prepared by the method has an asymmetric porous structure, has the characteristics of high mechanical strength, high proton conductivity and high ion selectivity, and can realize selective separation of ions. In addition, the invention also has the advantages of simple preparation process, economy, high efficiency and the like.

Description

Ion conductive film and preparation method thereof

Technical Field

The invention relates to a simple and efficient ion conductive membrane and a preparation method thereof, in particular to an asymmetric porous polymer membrane with an ion selection function and a preparation method thereof.

Background

The redox flow battery is a novel energy storage battery, realizes the storage and release of energy by using the oxidation-reduction reaction between different ions, and has the characteristics of long service life, high efficiency and easy regulation and control of capacity. The flow battery is used as a large-scale energy storage battery, and can be widely applied to the fields of new energy power generation systems, power grid peak regulation, off-grid power supply and the like.

In the flow battery, the ion selective membrane is a core component of the battery, and is required to provide a transmission condition for conductive protons while playing a role in blocking active substances of positive and negative electrodes. The proton conductivity, ion selectivity, stability, etc. of ion selective membranes have a great impact on the life, performance, and cost of the battery. Therefore, the membrane is required to have better ion selectivity (lower active ion permeability and better proton conductivity), better chemical stability and mechanical strength, and lower cost.

Currently, the ion selective membrane mainly used in the market is Nafion series perfluorosulfonic acid membrane of Dupont in the united states, which has excellent properties in terms of chemical stability, strength and life, but is expensive, and the main technology is grasped in a few countries of the day, the united states, and the like. Therefore, there is an urgent need to develop a low-cost high-performance ion selective membrane to meet the use requirements of the flow battery.

Taking an all-vanadium flow battery as an example, active materials vanadium ions and conductive protons in the electrolyte exist in the form of hydrated ions, the radius of the vanadium ions is obviously larger than that of the protons, and the conductive protons can pass through the membrane and can be blocked by a proper pore structure through a sieving mechanism. Meanwhile, the porous membrane has the characteristics of wide material selection range, low cost and strong stability. Therefore, the nano porous membrane can be used as a good substitute of a perfluorosulfonic acid membrane.

The porous membrane is usually prepared by a phase inversion method, a template method, a thermally induced phase separation method, or the like.

In the phase inversion method, a high molecular solution or a semi-dry solution of a continuous phase is put into a non-solvent solution, so that a high molecular polymer is rapidly separated out at an interface, and a porous structure is formed below a thin compact layer, thereby preparing the nano porous membrane. The porous membrane prepared by the phase separation method of the phase inversion method is widely applied to the flow battery. Yuyuyue Zhao et al (Advanced Functional Materials, 2016, 26, 210-218), zhizhang Yuan et al (Journal of Materials Chemistry a, 2017, 5, 6193-6199), patent CN201410776155.4, CN201610530366.9, CN 105201571868, etc. are reported in a sequential manner, using a phase inversion method as a preparation method of a membrane, or using a phase inversion method as a step in a preparation process of a porous membrane.

Summary the preparation method of phase inversion porous membrane reported in literature has found that:

(1) In many phase inversion porous membranes, the macro-porous side is mostly finger-shaped and is not ion-selective; an extremely thin compact layer can be formed on the surface close to the membrane, and plays a role in certain ion selectivity, but the thickness of the compact layer is extremely thin, and the compact layer is easy to break under external forces such as extrusion, stretching and the like, so that the function of the membrane is lost;

(2) The porous membrane prepared by the phase inversion method has the advantages that the thickness and the ion selectivity of the surface functional layer (dense layer) are difficult to control, and the consistency is poor.

(3) The porous film obtained by the phase inversion method is mostly inconvenient to realize the adjustment of the ionic conductivity and the selectivity.

In the template method, a small molecule substance is often used as a porogen, and after a dense film is formed, the small molecule substance is removed or treated by a method such as dissolution and hydrolysis to form a porous structure. Peng et al (Rsc adv.2017, 7 (4): 1852-1862), patent CN201710360200, CN201910477091 et al have successively reported that porous ion selective membranes are prepared by a template method.

Summary the findings of the template-based porous membrane preparation methods reported in the literature: the pore size and porosity of pore-forming by template method are affected by the size and agglomeration of pore-forming agent molecules and direct compatibility with polymer matrix, so that continuous regulation and control of pore size and porosity are inconvenient to realize.

In the thermally induced phase separation method, a homogeneous solution at a high temperature undergoes solid/liquid or liquid/liquid phase separation at a reduced temperature, thereby preparing a porous membrane of a high polymer. Matsuyama H (Journal of Applied Polymer Science, 2001, 79 (13): 2449-2455.) and Lloyd D R (Membrane Science, 1990.52. After literature analysis, the characteristics that the thermally induced phase separation process is difficult to control in the solvent volatilization stage and has larger influence on the performance of the membrane are found.

Disclosure of Invention

The invention provides an economical and efficient porous membrane preparation method, in particular to an ion selective membrane and a preparation method thereof, aiming at simply and conveniently obtaining a symmetrical and uniform continuous adjustable porous ion selective membrane. The ion selective permeable membrane prepared by the invention can be widely applied to the industrial fields of distillation, electrolysis, water treatment, lithium batteries, filtration, dialysis and the like, and has wide market prospect.

The purpose of the invention is realized by the following technical scheme:

the invention provides a preparation method of an ion-ion conductive membrane, which comprises the following steps:

a1: adding the ionic liquid into the sulfonated polymer solution to prepare a membrane casting solution;

a2: casting the casting solution on a flat plate, and then drying to obtain a composite film;

a3: washing away the ionic liquid in the composite membrane, and then drying to obtain the ionic conductive membrane;

the bacterial cellulose membrane is coated with silicon dioxide on the fiber surface, and the coating method comprises the following steps: 0.1mol of tetraethyl orthosilicate and 500ml of ethanol were mixed and stirred for 10 minutes to obtain a mixture A, and then 100cm of tetraethyl orthosilicate was added ² Adding 60g of deionized water into the mixture A, stirring for 10 minutes, adding 0.1mol of ammonia water into 40ml of ethanol to obtain a mixture B, slowly adding the mixture B into the mixture A, stirring for 12 hours, finally carrying out ultrasonic washing for three times by using the deionized water, and drying to obtain the bacterial cellulose membrane coated with the silicon dioxide.

Preferably, the step A2 further includes compounding the casting solution and the bacterial cellulose membrane, and then drying on a flat plate to obtain the bacterial cellulose composite membrane.

Preferably, the ionic liquid is N, N-diethylmethylamine-trifluoromethylsulfonate.

Preferably, the mass ratio of the ionic liquid to the sulfonated polymer in the casting solution is 1.

Preferably, the sulfonated polymer is one of sulfonated polyether sulfone, sulfonated polyether ether ketone or a combination thereof.

Preferably, the mass of the bacterial cellulose membrane is 3-20% of the mass of the sulfonated polymer.

The invention also provides an ion-conducting membrane prepared according to the method.

The principle of the invention is as follows: through the interaction between the ionic liquid and the sulfonated polymer molecules, the ionic liquid and the sulfonated polymer are separated in the drying process, and due to the density difference between the ionic liquid and the sulfonated polymer, a porous layer is formed on the lower side of the membrane, and a compact layer is formed on the upper side of the membrane, so that the ion-conducting membrane with an asymmetric structure, high mechanical strength, high proton conductivity and ion selectivity is finally obtained. Because the bacterial cellulose has higher mechanical strength, the enhanced ion-conducting membrane with obviously improved mechanical strength can be obtained by compounding the bacterial cellulose membrane.

Compared with the prior art, the invention has the following beneficial effects:

the composite porous membrane prepared by the method can realize the controllable adjustment of the compact layer, and the prepared asymmetric porous structure has the characteristics of high mechanical strength, high proton conductivity and high ion selectivity, can realize the selective separation of ions, and can be applied to all-vanadium flow battery cells. In addition, the invention also has the advantages of simple preparation process, economy, high efficiency and the like.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a scanning electron micrograph of a dense layer continuously controllable ion conductive membrane.

FIG. 2 is a graph showing the relationship between the proton conductivity of an ion-conducting membrane and the ionic liquid content in a casting solution.

FIG. 3 is a graph showing the relationship between the tensile strength of an ion-conducting membrane and the ionic liquid content in a casting solution.

FIG. 4 is a graph of vanadium ion permeability of an ion-conducting membrane as a function of ionic liquid content in the casting solution.

FIG. 5 is a graph of ion selectivity versus ionic liquid content in casting solutions.

Fig. 6 is a scanning electron micrograph of the ion-conductive film obtained in comparative example 1.

FIG. 7 is a scanning electron micrograph of the ion-conductive membrane obtained in comparative example 2.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the concept of the invention. All falling within the scope of the present invention.

Example 1

The embodiment provides an ion conductive membrane prepared by the method:

the ion conductive film comprises the following raw materials in parts by weight and is prepared through the following main points:

adding N, N-diethylmethylamine-trifluoromethanesulfonate into an N, N-dimethylformamide solution of sulfonated polyether sulfone to obtain a membrane casting solution, wherein the mass ratio of the ionic liquid to the sulfonated polymer is 1; and casting the casting solution on a glass plate, drying at 100 ℃ to obtain a composite membrane, cleaning the composite membrane with deionized water, and removing ionic liquid to obtain the ionic conductive membrane.

The sulfonated polyethersulfone ion selective membranes have structural and performance characteristics similar to those shown in FIGS. 1,2,3,4, 5.

Example 2

The embodiment provides an ion conductive membrane prepared by the method:

adding N, N-diethylmethylamine-trifluoromethanesulfonate into an N, N-dimethylformamide solution of sulfonated polyether sulfone to obtain a membrane casting solution, wherein the mass ratio of the ionic liquid to the sulfonated polymer is 2; and casting the membrane casting solution on a glass plate, drying at 80 ℃ to obtain a composite membrane, cleaning the composite membrane with deionized water, and removing ionic liquid to obtain the ionic conductive membrane.

The sulfonated polyethersulfone ion-selective membrane was similar in structure and performance characteristics to those shown in FIGS. 1,2,3,4, 5.

Example 3

The embodiment provides an ion-conducting membrane prepared by the method:

adding N, N-diethylmethylamine-trifluoromethylsulfonate into an N, N-dimethylacetamide solution of sulfonated polyether sulfone to obtain a membrane casting solution, wherein the mass ratio of the ionic liquid to the sulfonated polymer is 3; and casting the casting solution on a glass plate, drying at 120 ℃ to obtain a composite membrane, cleaning the composite membrane with deionized water, and removing ionic liquid to obtain the ionic conductive membrane.

The sulfonated polyethersulfone ion-selective membranes were similar in structure and performance characteristics to those shown in FIGS. 1,2,3,4, 5.

Example 4

The embodiment provides an ion conductive membrane prepared by the method:

adding N, N-diethylmethylamine-trifluoromethylsulfonate into an N, N-dimethylacetamide solution of sulfonated polyether-ether-ketone to obtain a membrane casting solution, wherein the mass ratio of the ionic liquid to the sulfonated polymer is 7; and casting the casting solution on a glass plate, drying at 100 ℃ to obtain a composite membrane, cleaning the composite membrane with deionized water, and removing ionic liquid to obtain the ionic conductive membrane.

The sulfonated polyetheretherketone ion selective membrane has structural and performance characteristics similar to those shown in figures 1,2,3,4, 5.

Example 5

The embodiment provides an ion conductive membrane prepared by the method:

adding N, N-diethylmethylamine-trifluoromethanesulfonate into an N, N-dimethylformamide solution of sulfonated polyether sulfone to obtain a membrane casting solution, wherein the mass ratio of the ionic liquid to the sulfonated polymer is 1; compounding the membrane casting solution and a bacterial cellulose membrane, wherein the mass of the bacterial cellulose membrane is 3% of that of the sulfonated polymer, then flatly paving the membrane on a glass plate, drying the membrane at 100 ℃ to obtain a bacterial cellulose composite membrane, washing the composite membrane by deionized water, and removing ionic liquid to obtain the ionic conductive membrane.

The bacterial cellulose composite sulfonated polyether ether ketone ion selective membrane has the structural and performance characteristics similar to those shown in figures 1,2,3,4 and 5, and the tensile strength is improved to 30.2 MPa.

Example 6

The embodiment provides an ion-conducting membrane prepared by the method:

the ion conductive film comprises the following raw materials in parts by weight and is prepared through the following key points:

adding N, N-diethylmethylamine-trifluoromethanesulfonate into an N, N-dimethylformamide solution of sulfonated polyether sulfone to obtain a membrane casting solution, wherein the mass ratio of the ionic liquid to the sulfonated polymer is 1; compounding the membrane casting solution and a bacterial cellulose membrane, wherein the mass of the bacterial cellulose membrane is 10% of that of the sulfonated polymer, then flatly paving the membrane on a glass plate, drying the membrane at 100 ℃ to obtain a bacterial cellulose composite membrane, cleaning the composite membrane by using deionized water, and removing ionic liquid to obtain the ionic conductive membrane.

The bacterial cellulose composite sulfonated polyether ether ketone ion selective membrane has the structural and performance characteristics similar to those shown in figures 1,2,3,4 and 5, and the tensile strength is improved to 56.1 MPa.

Example 7

The embodiment provides an ion-conducting membrane prepared by the method:

adding N, N-diethylmethylamine-trifluoromethanesulfonate into an N, N-dimethylformamide solution of sulfonated polyether sulfone to obtain a membrane casting solution, wherein the mass ratio of the ionic liquid to the sulfonated polymer is 1; compounding the membrane casting solution and a bacterial cellulose membrane, wherein the mass of the bacterial cellulose membrane is 20% of that of the sulfonated polymer, then flatly paving the membrane on a glass plate, drying the membrane at 100 ℃ to obtain a bacterial cellulose composite membrane, cleaning the composite membrane by using deionized water, and removing ionic liquid to obtain the ionic conductive membrane.

The bacterial cellulose composite sulfonated polyetheretherketone ion selective membrane has the structural and performance characteristics similar to those shown in figures 1,2,3,4 and 5, and the tensile strength is improved to 35.6 MPa.

Example 8

0.1mol of tetraethyl orthosilicate and 500ml of ethanol were mixed and stirred for 10 minutes to obtain a mixture A, and then 100cm of tetraethyl orthosilicate was added ² The bacterial cellulose membrane of (2) and 60g of deionized water were taken into mixture A and stirred for 10 minutes. 0.1mol of aqueous ammonia was taken up in 40ml of ethanol to give a mixture B. And slowly adding the B into the A, stirring for 12 hours, finally ultrasonically washing the mixture for three times by using deionized water, and drying to obtain the bacterial cellulose membrane coated with the silicon dioxide.

Adding N, N-diethylmethylamine-trifluoromethanesulfonate into an N, N-dimethylformamide solution of sulfonated polyether sulfone to obtain a membrane casting solution, wherein the mass ratio of the ionic liquid to the sulfonated polymer is 1; compounding the membrane casting solution and a bacterial cellulose membrane, wherein the mass of the bacterial cellulose membrane is 10% of that of the sulfonated polymer, then spreading the bacterial cellulose membrane on a glass plate, drying the bacterial cellulose membrane at 100 ℃ to obtain a bacterial cellulose composite membrane, washing the composite membrane by deionized water, and removing ionic liquid to obtain the ionic conductive membrane.

The bacterial cellulose composite sulfonated polyether ether ketone ion selective membrane has the structural and performance characteristics similar to those shown in figures 1,2,3,4 and 5, and the tensile strength is improved to 50.9 MPa.

Comparative example 1

This comparative example is essentially the same as the process of example 1, except that: the mass ratio of the ionic liquid to the sulfonated polymer in the membrane casting solution is 1:5.

the resulting ion-conducting membrane is a membrane having a symmetrical structure as shown in fig. 6, and the porous structure is not conspicuous, not having the asymmetrical structure shown in fig. 1.

Comparative example 2

This comparative example is essentially the same as the process of example 1, except that: the mass ratio of the ionic liquid to the sulfonated polymer in the membrane casting solution is 5:5.

the resulting ion-conducting membrane is a severely phase separated membrane as shown in fig. 7, without the asymmetric structure shown in fig. 1.

Comparative example 3

This comparative example is essentially the same as example 5 except that: the mass of the bacterial cellulose membrane was 1% of the mass of the sulfonated polymer.

The bacterial cellulose composite sulfonated polyetheretherketone ion selective membrane has the structural and performance characteristics similar to those shown in figures 1,2,3,4 and 5, the tensile strength is improved to 26.3MPa, and the reinforcing effect is not obvious.

Comparative example 4

This comparative example is essentially the same as example 5, except that: the mass of the bacterial cellulose membrane was 25% of the mass of the sulfonated polymer.

The bacterial cellulose composite sulfonated polyether ether ketone ion selective membrane has the structural and performance characteristics similar to those shown in figures 1,2,3,4 and 5, the tensile strength is improved to 19.7MPa, and the tensile strength is reduced on the contrary.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims

1. A preparation method of an ion conductive membrane is characterized by comprising the following steps:

a1, adding ionic liquid into a sulfonated polymer solution to prepare a membrane casting solution;

a2, compounding the membrane casting solution and the bacterial cellulose membrane, and then drying on a flat plate to obtain a bacterial cellulose composite membrane;

a3, washing away the ionic liquid in the composite membrane, and then drying to obtain the ionic conductive membrane;

the fiber surface of the bacterial cellulose membrane is coated with silicon dioxide, and the coating method comprises the following steps: 0.1mol of tetraethyl orthosilicate and 500ml of ethanol were mixed and stirred for 10 minutes to obtain a mixture A, and then 100cm of tetraethyl orthosilicate was added ² Adding 60g of deionized water into the mixture A, stirring for 10 minutes, adding 0.1mol of ammonia water into 40ml of ethanol to obtain a mixture B, slowly adding the mixture B into the mixture A, stirring for 12 hours, finally carrying out ultrasonic washing for three times by using the deionized water, and drying to obtain the bacterial cellulose membrane coated with the silicon dioxide.

2. The method of making an ion-conducting membrane according to claim 1, wherein the ionic liquid is N, N-diethylmethylamine-triflate.

3. The method of preparing an ion-conducting membrane according to claim 1, wherein the sulfonated polymer is one or a combination of sulfonated polyether sulfone and sulfonated polyether ether ketone.

4. The method for preparing an ion-conducting membrane according to claim 1, wherein the mass ratio of the ionic liquid to the sulfonated polymer in the casting solution is 1.

5. The method of making an ion-conducting membrane according to claim 1, wherein the mass of the bacterial cellulose membrane is 3% to 20% of the mass of the sulfonated polymer.

6. An ion-conducting membrane prepared according to the method for preparing an ion-conducting membrane according to any one of claims 1 to 5.