An electrodriven membrane and a method for its preparation

Abstract

The application provides an electrically driven membrane and a preparation method thereof, and belongs to the technical field of ion exchange membranes. In the application, one side of a porous base membrane is contacted with a two-dimensional nanomaterial water dispersion liquid, the porous base membrane and the two-dimensional nanomaterial layer are combined through electrostatic interaction, the two-dimensional nanomaterial is stabilized, water nanochannels are constructed, and the electrically driven membrane flux is improved; the two-dimensional nanomaterial layer is deposited on the surface of the porous base membrane to form wrinkles and stacks, the specific surface area and hydrophilicity are increased, and the electrically driven membrane flux is improved; the two-dimensional nanomaterial and the rigid support function can induce more nanoscale through pores in the porous base membrane, widen the pore size distribution range, and improve the electrically driven membrane flux; then the two-dimensional nanomaterial layer and the polyamines in the crown ether-polyamine mixed aqueous solution are connected through hydrogen bonds, a vertical growth topological template is provided for the polyamines and the subsequent polyacyl chloride layer and the polyamine crosslinking, disorder accumulation and excessive crosslinking are avoided, and the electrically driven membrane flux is improved.

Description

Technical Field

[0001] This invention relates to the field of ion exchange membrane technology, and in particular to an electrically driven membrane and its preparation method. Background Technology

[0002] As the global energy structure shifts towards cleaner and lower-carbon energy, lithium batteries, with their advantages of high energy density and long cycle life, have been widely used in new energy vehicles, portable electronic devices, and energy storage systems, driving explosive growth in the lithium battery industry. However, throughout the entire life cycle of lithium batteries, from cathode material synthesis and cell manufacturing to the dismantling and recycling of used lithium batteries, a large amount of lithium-containing waste liquid is generated.

[0003] Currently, membrane-electrodialysis separation technology is used to recover lithium waste liquid. This method offers high lithium separation selectivity, high purity of the recovered product, and is environmentally friendly. However, the low flux during lithium recovery leads to liquid accumulation, hindering large-scale utilization. For example, existing technologies using functionalized polyvinylidene fluoride ion exchange membranes for lithium recovery only achieve a flux of 2.55 mol·m⁻¹. -2 ·h -1 . Summary of the Invention

[0004] The purpose of this invention is to provide an electrically driven membrane and its preparation method, wherein the electrically driven membrane prepared by the preparation method of this invention has a large flux.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing an electrically driven membrane includes the following steps: The active surface of the porous base membrane is brought into contact with the aqueous dispersion of two-dimensional nanomaterials for the first adsorption, thereby forming a two-dimensional nanomaterial layer on the surface of the porous base membrane. The two-dimensional nanomaterial layer is contacted with a mixed aqueous solution of crown ether-polyamine to perform a second adsorption, thereby forming a crown ether-polyamine layer on the surface of the two-dimensional nanomaterial layer. The crown ether-polyamine layer is contacted with an aqueous glutaraldehyde solution to perform a Schiff base reaction, thereby generating a crown ether-polyimide layer on the surface of the two-dimensional nanomaterial layer. The crown ether-polyimide layer is contacted with an oil-phase solution of polyacrylamide chloride to perform nucleophilic substitution, thereby forming a polyacrylamide chloride layer on the surface of the crown ether-polyimide layer; The polyacrylamide layer is brought into contact with a polyamine aqueous solution to undergo a crosslinking reaction, forming a reverse interface polyamide layer on the surface of the crown ether-polyimide layer, thus obtaining an electrically driven film.

[0006] Preferably, the concentration of the two-dimensional nanomaterials in the aqueous dispersion is 0.02~0.08 mg / mL.

[0007] Preferably, the two-dimensional nanomaterials in the two-dimensional nanomaterial layer include one or more of rigid metal covalent organic frameworks, rigid nonmetal covalent organic frameworks, rigid metal carbides, and MXene.

[0008] Preferably, the mass concentration of crown ether in the crown ether-polyamine mixed aqueous solution is 0.1-0.6%, and the mass concentration of polyamine in the crown ether-polyamine mixed aqueous solution is 0.5-1%.

[0009] Preferably, the polyamine in the crown ether-polyamine mixed aqueous solution includes polyethyleneimine, m-phenylenediamine, or piperazine.

[0010] Preferably, the crown ether comprises 12-crown-4, 15-crown-5, 18-crown-6 or dibenzo-18-crown-6 ether.

[0011] Preferably, the mass concentration of the polyacryl chloride in the oil phase solution of the polyacryl chloride is 0.1~0.3%.

[0012] Preferably, the polyacryl chloride includes oxaloyl chloride, terephthaloyl chloride, or trimesoyl chloride.

[0013] The present invention also provides an electrically driven membrane prepared by the preparation method described above, comprising a porous base membrane, a two-dimensional nanomaterial layer, a crown ether-polyimide layer and a reverse interface polyamide layer stacked sequentially.

[0014] This invention provides a method for preparing an electro-driven membrane, comprising the following steps: contacting the active surface of a porous base membrane with an aqueous dispersion of two-dimensional nanomaterials for a first adsorption, forming a two-dimensional nanomaterial layer on the surface of the porous base membrane; contacting the two-dimensional nanomaterial layer with a mixed aqueous solution of crown ether and polyamine for a second adsorption, forming a crown ether-polyamine layer on the surface of the two-dimensional nanomaterial layer; contacting the crown ether-polyamine layer with an aqueous solution of glutaraldehyde to perform a Schiff base reaction, generating a crown ether-polyimide layer on the surface of the two-dimensional nanomaterial layer; contacting the crown ether-polyimide layer with an oil-phase solution of polyacrylamide chloride for nucleophilic substitution, forming a polyacrylamide chloride layer on the surface of the crown ether-polyimide layer; and contacting the polyacrylamide chloride layer with an aqueous solution of polyamine to perform a crosslinking reaction, forming a reverse interface polyamide layer on the surface of the crown ether-polyimide layer, thereby obtaining the electro-driven membrane. This invention introduces a layer of two-dimensional nanomaterials onto the surface of a porous base membrane by contacting the active surface of the membrane with an aqueous dispersion of two-dimensional nanomaterials. The two layers bond through electrostatic interaction, stabilizing the two-dimensional nanomaterials, constructing water nanochannels, and improving the electro-driven membrane flux. The deposition and stacking of the two-dimensional nanomaterial layer on the porous base membrane surface forms wrinkles and stacks, significantly increasing its specific surface area and hydrophilicity, further enhancing the electro-driven membrane flux. The rigid support of the two-dimensional nanomaterial structure induces the formation of more nanoscale through-pores within the porous base membrane, broadening the pore size distribution range and improving the electro-driven membrane flux. Then, the two-dimensional nanomaterial layer is contacted with a crown ether-polyamine mixed aqueous solution. The two-dimensional nanomaterials and polyamine are linked by hydrogen bonds, providing a vertical growth topological template for the crosslinking of the polyamine and subsequent polyacrylamide chloride layers, preventing disordered accumulation and excessive crosslinking, and providing a rapid transport path for lithium-ion wastewater, thus improving the electro-driven membrane flux. The results of the examples show that the electro-driven membrane flux provided by this invention can reach 4.32 mol·h⁻¹. -1 ·m -2 . Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the preparation process of the electrically driven membrane in an embodiment of the present invention. Figure 2 The images are SEM images magnified 1000x and 8000x respectively of the surface of the electro-driven membrane in Example 3 of the present invention, the electro-driven membrane in Comparative Example 1, the electro-driven membrane in Comparative Example 4, and the simple porous base membrane. Figure 3 The images are SEM images magnified 2000x and 8000x respectively of the cross-sections of the electro-driven membrane in Example 3 of the present invention, the electro-driven membrane in Comparative Example 1, the electro-driven membrane in Comparative Example 4, and the untreated porous base membrane. Figure 4 The flux and lithium-magnesium ion selectivity of the electro-driven membranes prepared by glutaraldehyde and water at different volume ratios in Examples 1-4 and Comparative Example 1 of this invention are shown. Figure 5The flux and lithium-magnesium ion selectivity of the electrically driven membranes prepared in Examples 3, 5-7 and Comparative Example 2 at different mass concentrations of 15% HCl are shown in the figure. Figure 6 The flux and lithium-magnesium ion selectivity of the electrodriven membranes prepared in Examples 3, 8-10 and Comparative Example 3 of the present invention at different mass concentrations of MXene are shown in the figure. Figure 7 The graphs show the flux and lithium-magnesium ion selectivity of the electro-driven membranes prepared from MXene aqueous dispersions at different standing times in Examples 3, 11-13 and Comparative Example 3 of this invention. Figure 8 A photograph of a self-made four-chamber electrodialysis device; Figure 9 This is a schematic diagram of a self-made four-chamber electrodialysis device. Detailed Implementation

[0016] This invention provides a method for preparing an electrically driven membrane, comprising the following steps: The active surface of the porous base membrane is brought into contact with the aqueous dispersion of two-dimensional nanomaterials for the first adsorption, thereby forming a two-dimensional nanomaterial layer on the surface of the porous base membrane. The two-dimensional nanomaterial layer is contacted with a mixed aqueous solution of crown ether-polyamine to perform a second adsorption, thereby forming a crown ether-polyamine layer on the surface of the two-dimensional nanomaterial layer. The crown ether-polyamine layer is contacted with an aqueous glutaraldehyde solution to perform a Schiff base reaction, thereby generating a crown ether-polyimide layer on the surface of the two-dimensional nanomaterial layer. The crown ether-polyimide layer is contacted with an oil-phase solution of polyacrylamide chloride to perform nucleophilic substitution, thereby forming a polyacrylamide chloride layer on the surface of the crown ether-polyimide layer; The polyacrylamide layer is brought into contact with a polyamine aqueous solution to undergo a crosslinking reaction, forming a reverse interface polyamide layer on the surface of the crown ether-polyimide layer, thus obtaining an electrically driven film.

[0017] In this invention, the active surface of a porous base membrane is brought into contact with an aqueous dispersion of two-dimensional nanomaterials for initial adsorption, thereby forming a two-dimensional nanomaterial layer on the surface of the porous base membrane.

[0018] In one embodiment of the present invention, the porous base membrane can be made of polyethersulfone, polysulfone, or polyvinylidene fluoride. The present invention, by defining a porous base membrane as the substrate of the composite membrane, provides mechanical strength and structural stability for the subsequently coated functional layers, preventing deformation or damage to the functional layers during use.

[0019] In one embodiment of the present invention, the porous base membrane can be pretreated before use; the pretreatment may include sequential acid immersion, a first water wash, a first natural air drying, an alkaline immersion, a second water wash, and a second natural air drying. In one embodiment of the present invention, the acid immersion can use sulfuric acid, hydrochloric acid, or nitric acid, and the concentration of the hydrochloric acid can be 1-2 mol / L; the alkaline immersion can use an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide, and the concentration of sodium hydroxide in the sodium hydroxide aqueous solution can be 1-2 mol / L, and the concentration of potassium hydroxide in the potassium hydroxide aqueous solution can be 1-2 mol / L. In one embodiment of the present invention, the first and second water washes can use ultrapure water, and the washing time can be stopped when the porous base membrane reaches neutrality. The present invention removes inorganic impurities, metal ions, and oxide residues from the surface and pores of the porous base membrane through pretreatment, cleaning the pores and ensuring uniform and unobstructed pore size.

[0020] In one embodiment of the present invention, the two-dimensional nanomaterials in the aqueous dispersion may include one or more of rigid metal covalent organic frameworks, rigid nonmetal covalent organic frameworks, rigid metal carbides, and MXene. In this invention, the two-dimensional nanomaterial layer is deposited on the surface of a porous membrane to form wrinkles and stacks, significantly increasing its specific surface area and hydrophilicity, thereby improving the electro-driven membrane flux. The rigid support of the rigid structure of the two-dimensional nanomaterials can induce the formation of more nanoscale through-pores within the porous membrane, broadening the pore size distribution range and further improving the electro-driven membrane flux.

[0021] In one embodiment of the present invention, the concentration of the two-dimensional nanomaterials in the aqueous dispersion can be 0.02~0.08 mg / mL. In specific embodiments of the present invention, the concentration of the two-dimensional nanomaterials in the aqueous dispersion can be 0.02 mg / mL, 0.04 mg / mL, 0.06 mg / mL, or 0.08 mg / mL. The present invention ensures a more ordered layer arrangement and fewer defects by limiting the concentration of the two-dimensional nanomaterials in the aqueous dispersion.

[0022] In this invention, the electrostatic interaction of the porous base membrane and the adsorption of two-dimensional nanomaterials can stabilize the two-dimensional nanomaterials, construct water nanochannels, and improve the flux of the electrically driven membrane.

[0023] This invention does not impose any particular limitation on the contact method between the active surface of the porous base membrane and the aqueous dispersion of two-dimensional nanomaterials; any contact method well-known in the art can be used. As one embodiment of this invention, the contact method may be to pour the aqueous dispersion of nanomaterials onto one side of the porous base membrane. As another embodiment of this invention, the first adsorption time may be 10-120 min, 30-100 min, or 50-80 min. This invention ensures that the two-dimensional nanomaterials can be uniformly distributed on the surface of the porous base membrane or within the pores of the porous base membrane by limiting the first adsorption time.

[0024] In one embodiment of the present invention, after the first adsorption is completed, the product after the first adsorption is subjected to a first post-processing; the first post-processing includes sequentially removing the unadsorbed two-dimensional nanomaterial aqueous dispersion, washing with pure water, and air drying. The present invention does not specifically limit the method of removing the unadsorbed two-dimensional nanomaterial aqueous dispersion; any removal method well-known in the art can be used to remove the two-dimensional nanomaterial aqueous dispersion not adsorbed on the porous base membrane surface. In one embodiment of the present invention, the removal of the unadsorbed two-dimensional nanomaterial aqueous dispersion can be achieved by rinsing with deionized water. The present invention does not specifically limit the number of times the pure water is washed; any number of pure water washings well-known in the art can be used to remove the unadsorbed two-dimensional nanomaterials from the porous base membrane surface. The present invention does not specifically limit the method of air drying; any air drying method well-known in the art can be used to remove the pure water. In one embodiment of the present invention, the air drying can be achieved by using a hair dryer.

[0025] After forming a two-dimensional nanomaterial layer on the surface of the porous base film, the two-dimensional nanomaterial layer is contacted with a crown ether-polyamine mixed aqueous solution to perform a second adsorption, thereby forming a crown ether-polyamine layer on the surface of the two-dimensional nanomaterial layer.

[0026] In one embodiment of the present invention, the crown ether in the crown ether-polyamine mixed aqueous solution may include 12-crown-4, 15-crown-5, 18-crown-6, or dibenzo-18-crown-6 ether. The present invention utilizes the molecular recognition and ion-selective complexation properties of crown ethers to specifically improve the selective transport / retention capacity of lithium ions, thereby enhancing the separation precision and functional specificity of the membrane.

[0027] In one embodiment of the present invention, the mass concentration of crown ether in the crown ether-polyamine mixed aqueous solution can be 0.1% to 0.6%. In specific embodiments of the present invention, the mass concentration of crown ether in the crown ether-polyamine mixed aqueous solution can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.6%. The present invention further improves the selective transport / retention capacity for lithium ions and enhances the separation accuracy and functional specificity of the membrane by limiting the mass concentration of crown ether in the crown ether-polyamine mixed aqueous solution.

[0028] In one embodiment of the present invention, the polyamine in the crown ether-polyamine mixed aqueous solution may include polyethyleneimine, m-phenylenediamine, or piperazine. The present invention limits the hydrogen bonding interaction between the polyamine and the crown ether, while simultaneously forming hydrogen bonding interactions with the two-dimensional nanomaterials, thus preventing crown ether detachment and reducing lithium-ion separation efficiency. In another embodiment of the present invention, the mass concentration of the polyamine in the crown ether-polyamine mixed aqueous solution may be 0.5-1% or 0.6-0.8%. By limiting the mass concentration of the polyamine, the present invention further ensures hydrogen bonding interactions with both the crown ether and the two-dimensional nanomaterials, further improving the stability of the crown ether.

[0029] In this invention, the two-dimensional nanomaterial layer is in contact with the crown ether-polyamine mixed aqueous solution. The two-dimensional nanomaterial and the polyamine are connected by hydrogen bonds, providing a topological template for the vertical growth of the polyamine and the subsequent cross-linking of the polyacrylamide layer with the polyamine, avoiding disordered accumulation and excessive cross-linking, providing a fast transport path for lithium ion wastewater, and improving the flux of the electro-driven membrane.

[0030] This invention does not impose any particular limitation on the contact method between the two-dimensional nanomaterial layer and the crown ether-polyamine mixed aqueous solution; any contact method well-known in the art can be used. As one embodiment of this invention, the contact method may be to pour the crown ether-polyamine mixed aqueous solution onto the surface of the two-dimensional nanomaterial layer. As another embodiment of this invention, the second adsorption time may be 5-10 minutes or 6-8 minutes. This invention ensures that the crown ether-polyamine can be uniformly distributed on the surface of the two-dimensional nanomaterial layer by limiting the second adsorption time.

[0031] In one embodiment of the present invention, after the second adsorption is completed, the product after the second adsorption can be subjected to a second post-processing; the second post-processing may include sequentially removing the unadsorbed crown ether-polyamine mixed aqueous solution, washing with pure water, and air drying. The present invention does not specifically limit the method of removing the unadsorbed crown ether-polyamine mixed aqueous solution; any removal method well-known in the art can be used to remove the crown ether-polyamine mixed aqueous solution not adsorbed on the surface of the two-dimensional nanomaterial layer. The present invention does not specifically limit the number of times the pure water is washed; any number of pure water washes well-known in the art can be used to remove the unadsorbed crown ether-polyamine mixed aqueous solution from the surface of the two-dimensional nanomaterial layer. The present invention does not specifically limit the method of air drying; any air drying method well-known in the art can be used to remove the pure water. In one embodiment of the present invention, the air drying can be performed using a hair dryer.

[0032] After forming a crown ether-polyamine layer on the surface of the two-dimensional nanomaterial layer, the present invention contacts the crown ether-polyamine layer with an aqueous solution of glutaraldehyde to perform a Schiff base reaction, thereby generating a crown ether-polyimide layer on the surface of the two-dimensional nanomaterial layer.

[0033] In one embodiment of the present invention, the volume ratio of glutaraldehyde to water in the glutaraldehyde aqueous solution can be (1~5):100. In specific embodiments of the present invention, the volume ratio of glutaraldehyde to water in the glutaraldehyde aqueous solution can be 1:100, 2:100, 3:100, 4:100, or 5:100. The present invention ensures sufficient Schiff base reaction with the polyamine in the crown ether-polyamine layer by limiting the volume ratio of glutaraldehyde to water in the glutaraldehyde aqueous solution.

[0034] In this invention, the polyamine in the crown ether-polyamine layer reacts with glutaraldehyde in an aqueous solution of glutaraldehyde to obtain a polyimide.

[0035] The present invention does not impose any particular limitation on the contact method between the crown ether-polyamine layer and the glutaraldehyde aqueous solution; any contact method well known in the art can be used. As one embodiment of the present invention, the contact method may be to pour the glutaraldehyde aqueous solution onto the surface of the crown ether-polyamine layer.

[0036] In this invention, during the Schiff base reaction, the carbon atom on the aldehyde group of glutaraldehyde forms a C=N bond with the nitrogen atom on the primary amine of the polyamine, reducing the number of aldehyde groups and making the polymer network more compact. This locks the crown ether within the dense cross-linked network, thereby improving the stability of the crown ether in the electro-driven membrane. As one embodiment of this invention, the Schiff base reaction temperature can be room temperature, and the reaction time can be 5-10 min or 6-8 min. This invention enhances the Donnan repulsion effect of the electro-driven membrane by limiting the Schiff base reaction time to ensure sufficient reaction between glutaraldehyde and the polyamine to generate C=N bonds; and by reducing the number of aldehyde groups, it makes the polymer network more compact, locking the crown ether within the dense cross-linked network, thereby improving the stability of the crown ether in the electro-driven membrane.

[0037] After the Schiff base reaction is completed, the product of the Schiff base reaction undergoes a third post-treatment; the third post-treatment may include sequential removal of unreacted glutaraldehyde aqueous solution and air drying. The present invention does not specifically limit the method of removing the unreacted glutaraldehyde aqueous solution; any removal method well-known in the art can be used to remove the glutaraldehyde aqueous solution that has not reacted with the polyamine in the crown ether-polyamine layer. The present invention also does not specifically limit the method of air drying; any air drying method well-known in the art can be used to remove pure water. As one embodiment of the present invention, the air drying can be performed using a hair dryer.

[0038] After forming a crown ether-polyimide layer on the surface of the two-dimensional nanomaterial layer, the present invention contacts the crown ether-polyimide layer with an oil phase solution of polyacrylamide chloride to perform nucleophilic substitution, thereby forming a polyacrylamide chloride layer on the surface of the crown ether-polyimide layer.

[0039] In one embodiment of the present invention, the polyacrylamide chloride in the oil phase solution may include oxaloyl chloride, terephthaloyl chloride, or trimesoyl chloride. In another embodiment, the oil phase solvent in the oil phase solution may be chlorobenzene, dichloromethane, ethylcyclohexane, toluene, n-hexane, or cyclohexane. In yet another embodiment, the mass concentration of the polyacrylamide chloride in the oil phase solution may be 0.1-0.3%, or 0.2-0.3%. The present invention limits the mass concentration of the polyacrylamide chloride in the oil phase solution to ensure the subsequent formation of an ultrathin, continuous, and defect-free polyamide active layer with the polyamine.

[0040] In this invention, polyacyl chlorides can form amide bonds with hydrogen-containing amino groups on the polyimide in the crown ether-polyimide layer, so as to carry out a reverse interfacial crosslinking reaction with the polyamine aqueous solution.

[0041] This invention does not impose any particular limitation on the contact method between the crown ether-polyimide layer and the oil phase solution of the polyacrylamide chloride; any contact method well known in the art can be used. In one embodiment of this invention, the contact method may be to pour the oil phase solution of the polyacrylamide chloride onto the surface of the crown ether-polyimide layer. In another embodiment of this invention, the nucleophilic substitution temperature may be room temperature, and the nucleophilic substitution time may be 1-3 minutes. This invention ensures sufficient reaction between the polyacrylamide chloride and the polyimide in the crown ether-polyimide layer by limiting the temperature and time of nucleophilic substitution.

[0042] After nucleophilic substitution, the present invention performs a fourth post-processing on the product after nucleophilic substitution; the fourth post-processing may include sequentially removing the unreacted polyacrylamide chloride oil phase solution and air drying. The present invention does not have a particular limitation on the method of removing the unreacted polyacrylamide chloride oil phase solution; any removal method well-known in the art can be used to remove the polyacrylamide chloride oil phase solution that has not reacted with the polyimide in the crown ether-polyimide layer. The present invention also does not have a particular limitation on the method of air drying; any air drying method well-known in the art can be used to remove pure water. As one embodiment of the present invention, the air drying can be performed using a hair dryer.

[0043] After forming a polyacrylamide layer on the surface of the crown ether-polyimide layer, the present invention contacts the polyacrylamide layer with a polyamine aqueous solution to carry out a crosslinking reaction, thereby forming a reverse interface polyamide layer on the surface of the crown ether-polyimide layer to obtain an electrically driven film.

[0044] In one embodiment of the present invention, the polyamine in the aqueous polyamine solution may include polyethyleneimine, m-phenylenediamine, or piperazine. In another embodiment of the present invention, the mass concentration of the polyamine in the aqueous polyamine solution may be 0.5-1.0% or 0.6-0.8%. The present invention controls the crosslinking reaction by limiting the mass concentration of the polyamine, thereby preparing an ultrathin, continuous, uniform, and defect-free polyamide active layer.

[0045] The present invention does not impose any particular limitation on the contact method between the polyacrylamide layer and the polyamine aqueous solution; any contact method well known in the art can be used. As one embodiment of the present invention, the contact method may be to pour the polyamine aqueous solution onto the surface of the polyacrylamide layer.

[0046] In this invention, the polyamine aqueous solution is poured into the polyacrylamide chloride layer during the crosslinking reaction, reducing the direct contact between water molecules and the polyacrylamide chloride, thereby significantly inhibiting the formation of carboxyl side reactions. The amine groups in the polyamine undergo nucleophilic addition-elimination reactions with the acrylamide chloride groups to form amide bonds, while simultaneously removing HCl. The resulting polyamide layer with a reverse interface is more easily exposed at the membrane-water interface, enhancing the positive charge on the electro-driven membrane surface and improving the selective separation of lithium ions. Furthermore, it avoids oxidation and loss of function caused by exposure of the two-dimensional nanomaterial layer to air. As one embodiment of this invention, the crosslinking temperature can be room temperature, and the crosslinking time can be 5-10 min or 6-8 min. This invention ensures the preparation of an ultrathin, continuous, uniform, and defect-free polyamide active layer by limiting the crosslinking temperature and time.

[0047] After the crosslinking reaction is completed, the product of the crosslinking reaction is subjected to a fifth post-processing. This fifth post-processing may include sequentially removing unreacted polyamine aqueous solution, air drying, baking, sealing, and refrigeration. The present invention does not have a specific limitation on the method of removing the unreacted polyamine aqueous solution; any removal method well-known in the art can be used to remove the unreacted polyamine aqueous solution. The present invention does not have a specific limitation on the method of air drying; any air drying method well-known in the art can be used to remove pure water. In one embodiment of the present invention, the air drying can be done using a hair dryer. In another embodiment of the present invention, the baking temperature can be 30-60°C, and the baking time can be 30-90 minutes. The present invention does not have a specific limitation on the sealing method; any sealing method well-known in the art can be used to seal the electrically driven membrane. The present invention does not have a specific limitation on the refrigeration method; any refrigeration method well-known in the art can be used to refrigerate the electrically driven membrane.

[0048] This invention introduces a layer of two-dimensional nanomaterials onto the surface of a porous base membrane by contacting one side of the membrane with an aqueous dispersion of two-dimensional nanomaterials. The two layers bond through electrostatic interaction, stabilizing the two-dimensional nanomaterials, constructing water nanochannels, and improving the electro-driven membrane flux. The deposition and stacking of the two-dimensional nanomaterial layer on the porous base membrane surface forms wrinkles and stacks, significantly increasing its specific surface area and hydrophilicity, further enhancing the electro-driven membrane flux. The rigid support of the two-dimensional nanomaterial structure induces the formation of more nanoscale through-pores within the porous base membrane, broadening the pore size distribution range and improving the electro-driven membrane flux. Then, the two-dimensional nanomaterial layer is contacted with a crown ether-polyamine mixed aqueous solution. The two-dimensional nanomaterials and polyamine are linked by hydrogen bonds, providing a vertical growth topological template for the cross-linking of the polyamine and subsequent polyacrylamide layers, preventing disordered accumulation and excessive cross-linking, and providing a rapid transport path for lithium-ion wastewater, thus improving the electro-driven membrane flux.

[0049] The present invention also provides an electrically driven membrane prepared by the preparation method described above, comprising a porous base membrane, a two-dimensional nanomaterial layer, a crown ether-polyimide layer and a reverse interface polyamide layer stacked sequentially.

[0050] In one embodiment of the present invention, the electrically driven membrane provided by the present invention comprises a porous base membrane. By defining the porous base membrane as the substrate of the composite membrane, the present invention provides mechanical strength and structural stability for the subsequently coated functional layers, preventing deformation or damage to the functional layers during use.

[0051] As one embodiment of the present invention, the electro-driven membrane provided by the present invention includes a two-dimensional nanomaterial layer disposed on the surface of a porous base membrane. The present invention significantly increases the specific surface area and hydrophilicity of the porous base membrane by limiting the deposition and stacking of the two-dimensional nanomaterial layer on the surface of the porous base membrane, thereby improving the electro-driven membrane flux. The rigid support effect of the rigid structure of the two-dimensional nanomaterial can induce the formation of more nanoscale through-pores inside the porous base membrane, broadening the pore size distribution range and improving the electro-driven membrane flux.

[0052] In this invention, the porous base membrane and the two-dimensional nanomaterial layer are electrostatically adsorbed.

[0053] As one embodiment of the present invention, the electrically driven membrane provided by the present invention includes a crown ether-polyimide layer disposed on the surface of a two-dimensional nanomaterial layer. The present invention can fix the crown ether by limiting the polyimide in the crown ether-polyimide layer, preventing its detachment; the crown ether has molecular recognition and ion-selective complexation properties, which can specifically improve the selective transport / retention capacity of lithium ions, enhancing the separation accuracy and functional specificity of the membrane.

[0054] In this invention, the two-dimensional nanomaterial layer and the crown ether-polyimide layer are adsorbed via hydrogen bonding.

[0055] In one embodiment of the present invention, the electrically driven film provided by the present invention further includes a reverse interface polyamide layer disposed on the surface of the crown ether-polyimide layer. The present invention enhances the selective separation of lithium ions by defining the reverse interface polyamide layer; and can prevent the two-dimensional nanomaterial layer from being exposed to air and thus oxidizing and losing its function.

[0056] In one embodiment of the present invention, the total thickness of the two-dimensional nanomaterial layer, crown ether-polyamine layer, crown ether-polyimide layer, polyacrylamide layer, and reverse interface polyamide layer in the electro-driven membrane can be 200 nm to 450 nm, 250 nm to 400 nm, or 300 nm to 350 nm. The present invention, by limiting the thickness of the electro-driven membrane, ensures the mechanical strength and structural stability of the membrane, improves selectivity and anti-permeation performance, facilitates the formation of uniform, dense, and defect-free ion transport channels, reduces ion leakage, concentration gradient permeation, and co-current ion leakage, and improves separation selectivity and flux.

[0057] In an embodiment of the present invention, the process flow diagram for the preparation of the electrically driven film is as follows: Figure 1 As shown: MXene is poured onto the PES surface to form an MXene layer, then a mixed aqueous solution containing 15-crown 5 and PEI is poured onto the MXene layer to form a 15-crown 5-PEI layer, then an aqueous solution of glutaraldehyde is poured onto the 15-crown 5-PEI layer to form a crown ether-polyimide layer, then an aqueous solution of TMC is poured onto the 15-crown 5-polyimide layer to form a TMC layer, and finally an aqueous solution of PEI is poured onto the TMC layer to form a reverse interface polyamide layer, thus obtaining an electrodriven membrane.

[0058] The electro-driven membrane provided by this invention has high flux and good selectivity for lithium ions.

[0059] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0060] Example 1 The polyethersulfone porous membrane was placed in a beaker containing 50 mL of 1 mol / L HCl aqueous solution and treated at room temperature for 30 min. The membrane was then removed and rinsed with ultrapure water until the surface pH of the membrane was neutral. The membrane was then air-dried. The dried membrane was then placed in 50 mL of 1 mol / L NaOH aqueous solution and treated in a water bath at 60 °C for 2 h. The membrane was then removed and rinsed with ultrapure water until the surface pH of the membrane was neutral. The membrane was then air-dried. The above-mentioned polyethersulfone porous base membrane was fixed in a polytetrafluoroethylene modified membrane tank. MXene aqueous dispersion was poured onto the active surface of the naturally air-dried polyethersulfone porous base membrane and allowed to stand for 10 minutes. After washing with deionized water to remove unadsorbed two-dimensional nanomaterials, the membrane was washed multiple times with ultrapure water. Then, the membrane was air-dried with a blower to form an MXene layer on the surface of the polyethersulfone porous base membrane. The mass concentration of MXene in the MXene aqueous dispersion was 0.02 mg / mL. A mixed aqueous solution of polyethyleneimine-15-crown-5 was poured onto the surface of the MXene layer and allowed to stand for 10 minutes. After removing excess mixed aqueous solution of polyethyleneimine-15-crown-5 by pouring a polytetrafluoroethylene modified membrane bath, the solution was dried using a blower to form a 15-crown-5-polyethyleneimine layer on the surface of the MXene layer. The mass concentration of polyethyleneimine in the mixed aqueous solution of polyethyleneimine-15-crown-5 was 0.75 wt%, and the mass concentration of 15-crown-5 in the mixed aqueous solution of polyethyleneimine-15-crown-5 was 0.4 wt%. A glutaraldehyde aqueous solution was poured onto the surface of a 15-crown-5-polyethyleneimine layer and reacted with a Schiff base for 10 minutes. After removing excess glutaraldehyde aqueous solution by pouring out a polytetrafluoroethylene modified membrane, the membrane was dried again using a blower to form a crown ether-polyimine layer on the surface of the MXene layer. The volume concentration of glutaraldehyde in the glutaraldehyde aqueous solution was 1%. A hexane solution of trimesoyl chloride was poured onto the surface of the crown ether-polyimide layer and reacted for 3 minutes. After removing excess trimesoyl chloride solution from the polytetrafluoroethylene modified membrane, the membrane was allowed to air dry naturally, resulting in a trimesoyl chloride layer on the surface of the crown ether-polyimide layer. The mass concentration of trimesoyl chloride in the hexane solution was 0.1%. A 0.75wt% aqueous solution of polyethyleneimine was poured onto the surface of the trimesoyl chloride layer for a reverse interfacial polymerization reaction for 10 min. Then, the layer was removed and dried in a 60℃ oven for 30 min to obtain an electrically driven film with a total thickness of 432.9 nm, consisting of a two-dimensional nanomaterial layer, a crown ether-polyamine layer, a crown ether-polyimide layer, a polyacrylamide layer, and a reverse interfacial polyamide layer.

[0061] Example 2 The difference between this embodiment and Embodiment 1 is that the volume concentration of glutaraldehyde in the glutaraldehyde aqueous solution is 2%; the rest is the same as in Embodiment 1, and an electrically driven membrane is obtained.

[0062] Example 3 The difference between this embodiment and Embodiment 1 is that the volume concentration of glutaraldehyde in the glutaraldehyde aqueous solution is 3%; the rest is the same as in Embodiment 1, and an electrically driven membrane is obtained.

[0063] Example 4 The difference between this embodiment and Embodiment 1 is that the volume concentration of glutaraldehyde in the glutaraldehyde aqueous solution is 4%; the rest is the same as in Embodiment 1, and an electrically driven membrane is obtained.

[0064] Example 5 The difference between this embodiment and Embodiment 3 is that the mass concentration of 15-crown-5 in the mixed aqueous solution of polyethyleneimine-15-crown-5 is 0.1 wt%; the rest is the same as in Embodiment 1, and an electrically driven membrane is obtained.

[0065] Example 6 The difference between this embodiment and Example 3 is that the mass concentration of 15-crown-5 in the mixed aqueous solution of polyethyleneimine-15-crown-5 is 0.2 wt%; the rest is the same as in Example 1, and an electrically driven membrane is obtained.

[0066] Example 7 The difference between this embodiment and Embodiment 3 is that the mass concentration of 15-crown-5 in the mixed aqueous solution of polyethyleneimine-15-crown-5 is 0.6wt%; the rest is the same as in Embodiment 1, and the thickness of the electrically driven film is ~.

[0067] Example 8 The difference between this embodiment and Example 3 is that the mass concentration of MXene in the MXene aqueous dispersion is 0.04 mg / mL; the rest is the same as in Example 1, and an electrically driven membrane is obtained.

[0068] Example 9 The difference between this embodiment and Example 3 is that the mass concentration of MXene in the MXene aqueous dispersion is 0.06 mg / mL; the rest is the same as in Example 1, and an electrically driven membrane is obtained.

[0069] Example 10 The difference between this embodiment and Example 3 is that the mass concentration of MXene in the MXene aqueous dispersion is 0.08 mg / mL; the rest is the same as in Example 1, and an electrically driven membrane is obtained.

[0070] Example 11 The difference between this embodiment and Example 3 is that: the MXene aqueous dispersion is poured onto the active surface of the naturally air-dried polyethersulfone porous base membrane and left to stand for 30 minutes; the rest is the same as in Example 1, and an electrically driven membrane is obtained.

[0071] Example 12 The difference between this embodiment and Embodiment 3 is that: the MXene aqueous dispersion is poured onto one side of the naturally air-dried polyethersulfone porous base membrane and left to stand for 60 minutes; the rest is the same as in Embodiment 1, and an electrically driven membrane is obtained.

[0072] Example 13 The difference between this embodiment and Example 3 is that: the MXene aqueous dispersion was poured onto one side of the naturally air-dried polyethersulfone porous base membrane and left to stand for 120 min; the rest was the same as in Example 1, and the total thickness of the two-dimensional nanomaterial layer, crown ether-polyamine layer, crown ether-polyimide layer, polyacrylamide layer and reverse interface polyamide layer in the electrically driven membrane was 376.8 nm.

[0073] Comparative Example 1 The difference between this comparative example and Example 3 is that no glutaraldehyde aqueous solution was added; otherwise, it is the same as Example 1, and an electrically driven membrane is obtained, the structure of which is a polyethersulfone porous base membrane, an MXene layer, a 15-crown-5-polyethylene polyamine layer and a reverse interface polymerization layer stacked in sequence.

[0074] Comparative Example 2 The difference between this comparative example and Example 3 is that 15-crown-5 is not added; otherwise, it is the same as Example 1, and the structure of the electrically driven membrane is a polyethersulfone porous base membrane, an MXene layer, a polyethyleneimine layer, and a reverse interface polymerization layer stacked sequentially.

[0075] Comparative Example 3 The difference between this comparative example and Example 3 is that no MXene aqueous dispersion is added; otherwise, it is the same as Example 1, with the structure consisting of a polyethersulfone porous base membrane, a 15-crown-5-polyethyleneimine layer, and a reverse interface polymerization layer stacked sequentially to obtain an electrically driven membrane.

[0076] Comparative Example 4 The difference between this comparative example and Example 3 is that: no MXene aqueous dispersion was added; no 15-crown-5 was added; no glutaraldehyde aqueous solution was added; the structure is an interfacial polymerization and reverse interfacial polymerization layer obtained by reacting a polyethersulfone porous base membrane, polyethyleneimine, a hexane solution of trimesoyl chloride and polyethyleneimine in sequence.

[0077] The electrically driven film in Example 3 was named #M using scanning electron microscopy. 0.02 / 10 C 0.4 G3), the electrically driven film in Comparative Example 1 (named #M) 0.02 / 10 C 0.4 The surface morphology of the electro-driven membrane (named #PTP) in Comparative Example 4 and the untreated porous base membrane (PES) was characterized, and the results are as follows: Figure 2 As shown in the figures: Figure a is a surface morphology image magnified 1000 times. It can be seen that the surface of the simple porous base film has black pores, corresponding to the pores of the porous base film. The pores of the electrically driven film in Comparative Example 4 are shallower. The pores on the surface of the electrically driven film in Comparative Example 1 are relatively deeper than those in Comparative Example 4. No pores are visible on the surface of the porous base film in Example 3. Figure b is a surface morphology image magnified 8000 times. It can be seen more clearly that the surface of the pure porous base film has a highly open structure with high surface porosity, and the pore size is significantly larger than the diameter of the hydrated particles of the ion structure to be separated. The surface of the electrically driven film in Comparative Example 4 is thin and relatively... A loose polyamide (PA) layer covers the membrane surface; in Comparative Example 1, the electrodriven membrane surface shows more obvious wrinkling, which is attributed to the electrostatic attraction and steric hindrance effect of MXene and 15-crown 5 on polyethyleneimine, which attracts polyethyleneimine and delays diffusion, resulting in significant local activation and lateral inhibition of subsequent crosslinking reactions; the electrodriven membrane surface in Example 3 becomes dense, with particles uniformly distributed on the surface. This is because the reaction of glutaraldehyde with the polyethyleneimine Schiff base yields a denser layer, and allows 15-crown 5 to be uniformly distributed on the membrane surface, thereby further improving selectivity.

[0078] The scanning electron microscope named the electrically driven film in Example 3 #M 0.02 / 10 C0.4 G3), the electrically driven film in Comparative Example 1 (named #M) 0.02 / 10 C 0.4 The cross-sectional morphology of the electro-driven membrane (named #PTP) in Comparative Example 4 and the untreated porous base membrane (PES) was characterized, and the results are as follows: Figure 3 As shown in the figures: Figure c is a cross-sectional morphology diagram magnified 2000 times, and Figure d is a cross-sectional morphology diagram magnified 8000 times. It can be observed that the simple porous base film has no selective layer. The selective layer thickness of Comparative Example 4 #PTP is 293.4 nm, indicating the successful formation of the PA modified layer; the selective layer thickness of Comparative Example 1 is 376.8 nm, which is thicker than that of Comparative Example 4, indicating the successful loading of the MXene layer and 15 crown 5, thereby increasing its thickness; the selective thickness of Example 3 is 432.9 nm, indicating that the reaction of glutaraldehyde with polyethyleneimine Schiff base further forms a polymer cross-linked network layer.

[0079] Electrodialysis was performed on the electrically driven membranes prepared in Examples 1-4 and Comparative Example 1 using a self-made four-chamber electrodialysis apparatus. A physical image of the apparatus is shown below. Figure 8 As shown: It consists of a desalination chamber, a concentration chamber, two electrode chambers, and two ruthenium-titanium (Ru-Ti) coated electrodes; the test schematic diagram is shown below. Figure 9 As shown, the test conditions were: the electrode chamber was continuously circulated with 0.2 M Na₂SO₄ solution; the desalination chamber was purged with 0.1 M Li₂SO₄ solution. + / Mg 2+ A binary chloride solution was concentrated by adding 0.01 M KCl solution. The effective area of ​​the membrane was 7.065 cm². 2 The applied current density ranges from 5 to 30 mA·cm. -2 All solutions were pumped at 20 mL / min using a peristaltic pump. -1 The system was circulated at a constant flow rate; then, samples were taken before and after the electrodialysis test and analyzed by ion chromatography. The flux and lithium-magnesium ion selectivity were calculated, and the results are as follows: Figure 4 As shown. The lithium flux of the electrically driven membranes prepared in Examples 1-4 and Comparative Example 1 were 3.34783, 2.76629, 3.09947, 4.32749, and 3.34783 mol·h⁻¹, respectively. -1 ·m -2Among them, the flux was highest when the volume ratio of glutaraldehyde to water was 3:100. This is because the Schiff base reaction polymer network becomes denser, which is more conducive to improving the steric hindrance of cation transport. Therefore, the permeability of the modified membrane increases with the increase of glutaraldehyde volume concentration. However, excessive glutaraldehyde volume concentration will lead to an overly dense membrane surface, thereby reducing permeability. The lithium-magnesium selectivity of the electrodriven membranes prepared in Examples 1-4 and Comparative Example 1 were 1.65406, 1.50881, 3.00228, 4.4175, and 1.65406, respectively. Among them, the lithium-magnesium ion selectivity was highest when the volume ratio of glutaraldehyde to water was 3:100. This is because an appropriate amount of glutaraldehyde, as a crosslinking agent, can stabilize and regularize the polymer network structure, optimize the pore size and charge distribution inside the membrane while maintaining the continuity of ion transport channels, reduce non-selective diffusion, and thus improve the lithium-magnesium ion separation selectivity.

[0080] Electrodialysis was performed on the electrically driven membranes prepared in Examples 3, 5-7 and Comparative Example 2 using a self-made four-chamber electrodialysis apparatus. Samples before and after the electrodialysis test were then subjected to ion chromatography to calculate the flux and lithium-magnesium ion selectivity. The results are as follows: Figure 5 As shown in the figure, the lithium flux of the electrically driven films prepared in Examples 3, 5-6, and Comparative Example 2 are 4.32749, 3.4059, 3.66801, 4.05163, and 3.76812 mol·h⁻¹, respectively. -1 ·m -2 The lithium-magnesium ion selectivity of the electrically driven membranes prepared in Examples 3, 5-7 and Comparative Example 2 were 4.4175, 2.07493, 2.31818, 1.65147 and 1.84639, respectively. The lithium-ion flux and lithium-magnesium ion selectivity were highest when the mass concentration of 15 crown 5 was 0.4%.

[0081] Electrodialysis was performed on the electrically driven membranes prepared in Examples 3, 8-10, and Comparative Example 3 using a self-made four-chamber electrodialysis apparatus. Samples before and after the electrodialysis test were then subjected to ion chromatography to calculate the flux and lithium-magnesium ion selectivity. The results are as follows: Figure 6 As shown, the lithium flux of the electrically driven membranes prepared in Examples 3, 8-10, and Comparative Example 3 were 4.32749, 2.53857, 2.0602, 2.72121, and 3.18812 mol·h⁻¹, respectively. -1 ·m -2 The lithium-magnesium ion selectivity of the electrically driven membranes prepared in Examples 3, 8-10 and Comparative Example 3 were 4.4175, 3.49531, 1.99577, 1.33522 and 3.65642, respectively. The lithium-ion flux and lithium-magnesium ion selectivity were highest when the mass-volume concentration of MXene was 0.02.

[0082] Electrodialysis was performed on the electrically driven membranes prepared in Examples 3, 11-13, and Comparative Example 3 using a self-made four-chamber electrodialysis apparatus. Samples before and after the electrodialysis test were then subjected to ion chromatography to calculate the flux and lithium-magnesium ion selectivity. The results are as follows: Figure 7 As shown, the lithium flux of the electrically driven membranes prepared in Examples 3, 11-13, and Comparative Example 3 were 4.32749, 2.66542, 3.67718, 3.64509, and 3.18812 mol·h⁻¹, respectively. -1 ·m -2 The lithium-magnesium ion selectivities were 4.4175, 3.02408, 2.04905, 2.56498, and 3.65642, respectively. The lithium-magnesium ion flux and selectivity were highest when the MXene settling time was 10 min. This is because at 10 min, MXene nanosheets only underwent shallow, uniform deposition, with no significant agglomeration, forming only ultrathin, ordered two-dimensional channels on the membrane surface. When the settling time was extended to 30 min, MXene nanosheets underwent short-term irreversible agglomeration due to interlayer van der Waals forces and hydrogen bonding, forming dense agglomerate patches that directly blocked most of the effective transport channels on the membrane surface, reducing flux. Further extending the settling time to 60 and 120 min, prolonged settling caused localized loosening and cracking of the dense MXene agglomerates, re-opening some blocked channels and increasing flux.

[0083] In summary, the electrically driven membrane prepared by the method of the present invention has high flux and good lithium-ion selectivity.

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an electrically driven membrane, comprising the following steps: The active surface of the porous base membrane is brought into contact with the aqueous dispersion of two-dimensional nanomaterials for the first adsorption, thereby forming a two-dimensional nanomaterial layer on the surface of the porous base membrane. The two-dimensional nanomaterial layer is contacted with a mixed aqueous solution of crown ether-polyamine to perform a second adsorption, thereby forming a crown ether-polyamine layer on the surface of the two-dimensional nanomaterial layer. The crown ether-polyamine layer is contacted with an aqueous glutaraldehyde solution to perform a Schiff base reaction, thereby generating a crown ether-polyimide layer on the surface of the two-dimensional nanomaterial layer. The crown ether-polyimide layer is contacted with an oil-phase solution of polyacrylamide chloride to perform nucleophilic substitution, thereby forming a polyacrylamide chloride layer on the surface of the crown ether-polyimide layer; The polyacrylamide layer is brought into contact with a polyamine aqueous solution to undergo a crosslinking reaction, forming a reverse interface polyamide layer on the surface of the crown ether-polyimide layer, thus obtaining an electrically driven film.

2. The preparation method according to claim 1, characterized in that, The concentration of the two-dimensional nanomaterials in the aqueous dispersion is 0.02~0.08 mg / mL.

3. The preparation method according to claim 1, characterized in that, The two-dimensional nanomaterials in the two-dimensional nanomaterial layer include one or more of rigid metal covalent organic frameworks, rigid nonmetal covalent organic frameworks, rigid metal carbides, and MXene.

4. The preparation method according to claim 1, characterized in that, The crown ether-polyamine mixed aqueous solution has a crown ether mass concentration of 0.1-0.6% and a polyamine mass concentration of 0.5-1%.

5. The preparation method according to claim 1 or 4, characterized in that, The polyamines in the crown ether-polyamine mixed aqueous solution include polyethyleneimine, m-phenylenediamine, or piperazine.

6. The preparation method according to claim 1 or 4, characterized in that, The crown ether in the crown ether-polyamine mixed aqueous solution includes 12-crown-4, 15-crown-5, 18-crown-6 or dibenzo-18-crown-6 ether.

7. The preparation method according to claim 1, characterized in that, The mass concentration of the polyacryl chloride in the oil phase solution is 0.1~0.3%.

8. The preparation method according to claim 1 or 7, characterized in that, The polyacyl chlorides include oxaloyl chloride, terephthaloyl chloride, or trimesoyl chloride.

9. The electrically driven membrane according to any one of claims 1 to 8 comprises a porous base membrane, a two-dimensional nanomaterial layer, a crown ether-polyimide layer and a reverse interface polyamide layer stacked sequentially.

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