KR20190026530A - Separator of redox flow battery, preparation method for separator of flow battery, and redox flow battery - Google Patents

Abstract

The present invention relates to a separator of a redox flow battery capable of maintaining high cell efficiency due to high durability, low internal resistance, and low crossover properties of a charged active material in a redox flow battery, a method for manufacturing the separator of a redox flow battery, and a redox flow battery. The separator of the redox flow battery comprises: a porous substrate; and an ion conductive resin filled in pores of the porous substrate.

Description

TECHNICAL FIELD [0001] The present invention relates to a redox flow battery separator, a redox flow battery manufacturing method, and a redox flow battery,

The present invention relates to a separator for redox flow battery, a method for manufacturing redox flow battery, and a redox flow battery. More particularly, the present invention relates to a separator for a redox flow cell having high durability, low internal resistance, and low crossover characteristics of a charged active material, And a redox flow battery.

Existing power generation systems, such as thermal power generation using nuclear fossil fuels and large-scale greenhouse gas and environmental pollution problems, and nuclear power generation, which have the problems of stability of the facility itself or waste disposal problems, have various limitations and are more environmentally friendly and highly efficient Research on the development of energy and the development of power supply system using it has been greatly increased.

Particularly, the power storage technology makes it possible to utilize renewable energy which is greatly influenced by external conditions in a wider and wider range, and the efficiency of power utilization can be further increased. And research and development have been increasing.

The redox flow cell is an oxidation / reduction cell that can convert the chemical energy of the active material directly into electrical energy. It stores renewable energy with high output fluctuation depending on the external environment such as sunlight and wind power and converts it into high quality power Energy storage system. Specifically, in the redox flow cell, the electrolyte containing the active material causing the oxidation / reduction reaction circulates between the opposite electrode and the storage tank, and charging / discharging proceeds.

The redox flow cell basically includes a tank storing different active materials in oxidation states, a pump circulating the active material during charging / discharging, and a unit cell divided into a separation membrane. The unit cell includes an electrode, an electrolyte, and a separation membrane do.

The separator of the redox flow cell is a core material that generates current flow through the movement of ions generated in response to the anode and cathode electrolyte during charge discharge. Currently, it is common to use separators for rechargeable batteries such as lithium batteries, lead batteries, fuel cells and the like, but this prior separator has a problem in that it causes a high crossover of the charged active material between the positive and negative electrode electrolytes, The efficiency and the charge amount are lowered and the resistance to bromine or vanadium ions is not sufficient, so that it is difficult to sufficiently secure the lifetime of the battery.

US Patent No. 4,190,707 and Korean Patent No. 1042931 disclose a microporous separator for an alkaline battery or a secondary battery. However, such a conventional porous separator has a disadvantage in that a crossover of a charged active material between a positive electrode and a negative electrode electrolyte required in a redox- And a method capable of securing resistance to bromine is not provided.

U.S. Patent No. 4,190,707 Korea Patent No. 1042931

The present invention provides a separation membrane of a redox flow cell which can achieve high efficiency performance and can reduce the cost cost remarkably due to the characteristics of high durability, low internal resistance and low crossover of the charged active material in the redox flow battery .

The present invention also provides a method for producing the separator of the redox flow cell.

Furthermore, the present invention provides a redox flow cell including the separator.

According to one embodiment of the present invention, a porous substrate; And an ion conductive resin filled in the pores of the porous substrate, wherein the ion conductive resin comprises a hydrophilic ion cluster.

According to another embodiment of the present invention, there is provided a method of manufacturing a porous substrate, comprising: filling an ion conductive resin solution containing an ion conductive resin, propylene carbonate and an organic solvent in pores of a porous substrate; Drying the porous substrate filled with the ion conductive resin solution in the pores; And a step of impregnating the dried porous substrate with deionized water to remove propylene carbonate.

According to another embodiment of the present invention, there is provided a redox flow cell comprising the separation membrane.

Hereinafter, a separator of a redox flow cell, a method of preparing a redox flow cell, and a redox flow cell according to a specific embodiment of the present invention will be described in detail.

According to one embodiment of the present invention, a porous substrate; And an ion conductive resin filled in the pores of the porous substrate, wherein the ion conductive resin comprises a hydrophilic ion cluster.

Conventional separator membranes for redox flow batteries have a problem of high raw material costs, low chemical resistance, and high crossover of charged active materials between the positive and negative electrode electrolytes.

However, when the separator is used as a separator of a redox flow cell, the present inventors have found that the ion conductive resin has a low internal resistance and improves the cell efficiency by reducing the crossover phenomenon of the charged active material between the anode and the cathode electrolyte In particular, it has been confirmed through experiments that the problem of the high internal resistance of the filling film can be solved by controlling the size of the hydrophilic ion clusters contained in the ion conductive resin in particular, and completed the invention.

In addition, it is possible to reduce the raw material cost compared to the pure ion conductive membrane by preparing the separation membrane by filling the pores of the porous substrate with the ion conductive resin, and it is possible to form a pinhole in the separation membrane by the zinc dendrite formed during the operation of the redox flow cell And the durability can be improved.

Hereinafter, the porous separator of the redox flow cell of the embodiment will be described in more detail.

The separator for the redox flow battery comprises a porous substrate and an ion conductive resin filled in the pores of the porous substrate, wherein the ion conductive resin comprises a hydrophilic ion cluster. The hydrophilic ion cluster has a diameter of 5.5 to 7 nm as measured by small-angle X-ray scattering (SAXS). ( D _c ) of the hydrophilic ion clusters according to the following general formula (1) obtained by the measurement by the small-angle X-ray scattering (SAXS) is 5.5 to 7 nm.

[Formula 1]

d _c = (6 Vc /?) ^1/3

In the above general formula (1), Vc is a volume of cubic lattice determined by the following general formula (2)

[Formula 2]

Vc = {Δ V / (1 + Δ V)} d 3 + N P V P

D is the Bragg spacing determined by the following general formula 3, N _P is the number of ion exchange sites, V _P is the volume of the ion exchange site volume of ion exchange site), DELTA V is the volume change of the membrane before and after water swelling,

[Formula 3]

d (Bragg spacing) = 2? / q

In Formula 3, q is a scattering factor determined by the following Formula 4,

[Formula 4]

q = (4? /?) * sin (2? / 2)

In the general formula (4),? Is the wavelength of the X-ray and? Is the scattering angle.

The ion conductive resin filled in the pores of the porous base material is a polymer easily selective ion exchange. When a separation membrane including a porous base material filled with such a polymer is used in a redox flow cell, a cross of the charged active material between the anode and the cathode electrolyte Over phenomenon can be selectively prevented and battery efficiency can be improved. In addition, there is an advantage that cost of raw materials can be reduced by using only expensive pore portions of the porous base material by filling it with an expensive ion conductive resin.

However, in the case of the separation membrane in which the ion conductive resin is filled in the pores of the porous substrate, there is a problem in that the internal resistance is larger than that of the separation membrane composed only of the ion conductive resin. However, By controlling the diameter of the hydrophilic ion cluster to 5.5 to 7 nm, the internal resistance of the separation membrane can be lowered.

Specifically, the ion conductive resin is composed of a hydrophobic region in which a main chain is assembled and a hydrophilic region in which a side chain of a hydrophilic functional group is assembled, and the ion is divided into a plurality of channels located in a hydrophilic region, Ion clusters. The plurality of hydrophilic ion clusters are continuous in the thickness direction of the separation membrane, and thus function as a movement path of ions.

Therefore, the larger the average diameter of the hydrophilic ion clusters is, the easier the ions can pass. As a result, the larger the average diameter of the clusters of the hydrophilic ions, the lower the internal resistance of the separation membrane.

As the ion conductive resin, various polymers having ion conductive functional groups may be used. Specifically, polymers having functional groups having cation exchange ability can be used. For example, sulfonated tetrafluoroethylene-based polymer, sulfonated polyimide (sPI), sulfonated poly (arylene ether sulfone), sPAES, Sulfonated polyetheretherketone (sPEEK), sulfonated polyetherketone (sPEK), polyvinylidene fluoride-graft-poly (styrene sulfonic acid) ), PVDF-g-PSSA), and sulfonated poly (fluorenyl ether ketone).

The ion conductive resin may be a sulfonated tetrafluoroethylene-based polymer. Ethylene-based polymer to the sulfonated tetrafluoroethylene is Nafion (Nafion ^®, Dupont), Aquitania rain (Aquivion ^®, Solvay), play lukewarm ^{(Flemion TM, AGC chemicals company)} , or know, Flex (Aciplex ^TM, Asahi Kasei) days .

The ion conductive resin may be contained in an amount of 20 to 70% by weight, 25 to 45% by weight, or 27 to 35% by weight based on the total weight of the redox flowable battery separator. If the content of the ion conductive resin is less than 20% by weight, the effect of improving the cell efficiency may be insignificant. If it exceeds 70% by weight, the cost of the raw material may increase.

The porous substrate is a sheet having a plurality of pores (110). The porous substrate includes at least one selected from the group consisting of polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polyamide, polyimide, polybenzoxazole, polyethylene terephthalate, polyethylene, polysulfone and polyether sulfone can do.

The porous substrate may have an average porosity of 30 to 70% by volume, 40 to 60% by volume, or 45 to 55% by volume. When the average porosity is less than 30% by volume, the content of the ion- The battery efficiency of the toxic flow cell may be deteriorated, and if it exceeds 70% by volume, the durability may be deteriorated.

The pores of the porous substrate may have an average particle diameter of 10 to 200 nm, 15 to 40 nm, or 20 to 35 nm. If the average particle diameter is less than 10 nm, the internal resistance of the separation membrane may increase or the cell efficiency may deteriorate. Durability may be deteriorated.

The porous substrate may have a thickness of 5 to 700 μm, 15 to 90 μm, or 25 to 80 μm. If the thickness is less than 5 μm, the durability may deteriorate. If the thickness is more than 700 μm, have.

The separator for the redox flow battery may further include a coating layer including an ion conductive resin on at least one surface of the porous substrate. When a coating layer is formed on the porous substrate, the thickness ratio of the coating layer and the porous substrate may be 1: 3 to 300, 1: 4 to 25, or 1: 5 to 20. If the thickness ratio is less than 1: 3, the cost of the raw material may increase due to excessive use of the ion conductive resin. If the thickness ratio is more than 1: 300, the effect of increasing the electric efficiency due to addition of the coating layer may not be exhibited any more.

The separator for the redox flow battery according to the embodiment may further include silica filled in pores of the porous substrate. The silica may allow the electrolyte to penetrate into the separator for the redox flow battery more easily. The silica particles may include a siloxane structure which is a bond between a silicon atom and an oxygen atom. In the siloxane structure, a monofunctional (M), a difunctional (D) functional group may be present depending on the number of organic groups bonded to silicon atoms ), Trifunctional (T), and quadrifunctional (Q).

The silica may comprise wet silica, dry silica or mixtures thereof.

Precipitated silica is a silica prepared by using silicate sodium silicate as a raw material, precipitating silica by neutralizing the aqueous solution, filtering and drying the silica; Or silica produced through a hydrolysis reaction using alkoxysilane instead of sodium silicate. The average particle diameter of the wet silica may be 100 to 200 nm, 120 to 190 nm, or 140 to 180 nm.

The fumed silica may include silica prepared by pyrolyzing tetrachlorosilane (SiCl ₄ ) at a high temperature (1100 ° C.) or silica produced by heating the obtained silica or silica under high temperature and vacuum and depositing it on a cold surface have. The dry silica may have an average particle size of 4 to 30 nm, 8 to 25 nm, or 12 to 20 nm.

According to another embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: filling an ion conductive resin solution containing an ion conductive resin, propylene carbonate and an organic solvent in pores of a porous substrate; Drying the porous substrate filled with the ion conductive resin solution in the pores; And a step of impregnating the dried porous substrate with deionized water to remove the propylene carbonate.

1 is a view schematically showing a method for producing a separator for a redox flow battery according to an embodiment.

Specifically, the separation membrane for redox flow battery includes a step of filling an ion conductive resin solution 210 containing an ion conductive resin 250, propylene carbonate, and an organic solvent in pores 110 of the porous base material 100 can do. As a method for filling the pores of the porous substrate with the ion conductive resin solution, there is a method of impregnating the porous substrate with a container contained in the ion conductive resin solution, or by directly pouring the ion conductive resin solution into the porous substrate A method of filling the pores with the above ion conductive resin solution can be used.

After the step of filling the pores 110 of the porous substrate 100 with the ion conductive resin solution 210, the ion conductive resin solution may be coated on both surfaces of the porous substrate to form the coating layers 230 and 240 . A part of the ion conductive resin solution coated on both surfaces of the porous substrate may be supplemented into the pores to increase the content of the ion conductive resin 250 and the propylene carbonate in the pores.

The ion conductive resin solution 210 may include an ion conductive resin 250, propylene carbonate, and an organic solvent.

The content of the ion conductive resin 250 includes the above-mentioned contents in the embodiment, and it may be, for example, Nafion. The content of the ion conductive resin may be 2 to 20% by weight, 5 to 15% by weight, or 10 to 13% by weight based on the total weight of the ion conductive resin solution 210. If the content of the ion conductive resin does not satisfy the above-described range, it may be difficult for the ion conductive resin to be effectively filled in the porous base material 100.

In the case of the separation membrane in which the ion conductive resin 250 is contained in the pores 110 of the porous substrate 100, there is a problem in that the internal resistance is larger than that of the separation membrane composed only of the ion conductive resin. However, in the separation membrane manufacturing method according to another embodiment, the internal resistance of the separation membrane can be lowered by preparing the separation membrane by incorporating the propylene carbonate into the ion conductive resin solution 210.

Specifically, the ion conductive resin is composed of a hydrophobic region in which a main chain is assembled and a hydrophilic region in which a side chain of a hydrophilic functional group is assembled, and the ion is divided into a plurality of channels located in a hydrophilic region, Ion clusters. The plurality of hydrophilic ion clusters are continuous in the thickness direction of the separation membrane, and thus function as a movement path of ions.

Accordingly, in the separation membrane manufacturing method according to another embodiment of the present invention, the diameter of the hydrophilic ion clusters contained in the ion conductive resin can be controlled to a large extent by filling the porous substrate with the propylene carbonate together with the ion conductive resin.

Specifically, the ion conductive resin is composed of a hydrophobic region in which a main chain is assembled and a hydrophilic region in which a side chain of a hydrophilic functional group is assembled, and the ion is divided into a plurality of channels located in a hydrophilic region, Ion clusters. The plurality of hydrophilic ion clusters are continuous in the thickness direction of the separation membrane, and thus function as a movement path of ions.

Therefore, the larger the average diameter of the hydrophilic ion clusters is, the easier the ions can pass. As a result, the larger the average diameter of the clusters of the hydrophilic ions, the lower the internal resistance of the separation membrane.

The propylene carbonate, which controls the diameter of the hydrophilic ion clusters contained in the ion conductive resin 250, is removed through a process of impregnating the ion conductive resin 250 with deionized water. Finally, the separator to be finally prepared does not contain propylene carbonate, The cell efficiency of the flow cell is not affected.

The content of the propylene carbonate may be 1 to 50% by weight, 2 to 40% by weight, and 5 to 30% by weight based on the total weight of the ion conductive resin solution 210. If the content of the propylene carbonate is less than 1% by weight, the internal resistance of the separator may be large, and if it exceeds 50% by weight, the battery efficiency may be reduced.

The organic solvent of the ion conductive resin solution 210 may be selected from the group consisting of n-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc), dipropylene glycol (DPG), ethylene glycol Propylene glycol (PG) and isopropyl alcohol (IPA).

On the other hand, the ion conductive resin solution 210 may further include silica, and the silica includes the above-mentioned contents in the embodiment.

In another embodiment of the present invention, a method for manufacturing a separator for a redox flow battery may include drying the porous substrate 100 in which the ion conductive resin solution 210 is filled in the pores 110.

When the porous substrate 100 filled in the pores 110 is dried, the organic solvent in the pores is removed. As a result, the ion conductive resin 250 and propylene carbonate may remain in the pores of the porous substrate. On the other hand, when the drying process is performed after the coating layers 230 and 240 are further formed on the upper and lower surfaces of the porous substrate, the ion conductive resin and propylene carbonate may remain in the pores of the porous substrate, have.

The drying may be performed at 50 to 150 DEG C for 30 minutes to 4 hours. If the drying takes place at a temperature of less than 50 ° C. or for a time of less than 30 minutes, the solvent may not be sufficiently removed, which may affect the physical properties of the ion conductive resin and may occur at temperatures above 150 ° C., For a period of time, denaturation may occur in the membrane, which may affect the cell efficiency.

After the drying step, the dried porous substrate 100 may be impregnated with deionized water to remove the propylene carbonate. Through this impregnation process, the propylene carbonate contained in the pores 110 of the porous substrate or on one side of the porous substrate can be dissolved in deionized water and removed. As a result, the hydrophilic ion clusters having a larger diameter due to the propylene carbonate still remain in a state of increased diameter even after the propylene carbonate is removed, so that the internal resistance of the separation membrane can be lowered.

The method for producing a separator for a redox flow battery according to another embodiment further comprises a post-treatment step of immersing the porous substrate 100 from which the propylene carbonate has been removed in at least one selected from the group consisting of water, sulfuric acid and hydrogen peroxide . Such a post-treatment process may be carried out at 25 to 100 DEG C for 1 to 10 hours.

According to another aspect of the present invention, there is provided a redox flow cell including the separation membrane.

The redox-sulm cell may be a zinc-bromine redox flow cell or a vanadium redox flow cell.

The redox flow battery may include a unit cell including the separator and the electrode, a tank storing different active materials having different oxidation states, and a pump circulating the active material between the unit cell and the tank at the time of charging and discharging.

The content of the separator includes the above-described contents of the embodiment.

According to the present invention, there is provided a redox flow cell capable of improving battery efficiency due to high durability, low internal resistance, and low crossover characteristics of a charged active material in a redox flow battery, A separator, a method of manufacturing a separator of a redox flow cell, and a redox flow cell.

1 is a view schematically showing a method for producing a separator for a redox flow battery according to an embodiment.
2 is a photograph of a cross section of a separator for a redox flow battery according to Example 1, taken by a scanning electron microscope.
FIG. 3 is a schematic view of a single cell to confirm the performance of the separator of Example 1 and Comparative Example 1. FIG.
4 is a graph showing the charge / discharge performance evaluation results of a single cell including the separator of Example 1 and Comparative Example 1. Fig.

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

Example 1

Nafion (Nafion D520, DuPont) was dissolved in about 5% by weight of isophthalic acid (IPA) in water and spray-dried at a temperature of about 80 ° C to obtain Nafion particles. 10% by weight of Nafion particles and 30% by weight of propylene carbonate thus prepared were dissolved in n-methyl-2-pyrrolidone (NMP) to prepare an ion conductive resin solution.

A porous polypropylene film (porosity: 60% by volume, thickness: 20 탆) containing a plurality of pores having a particle diameter of 14 to 48 nm was impregnated in the ion conductive resin solution for about 5 minutes. Thereafter, a coating layer of the conductive resin solution was formed on one surface of the porous polypropylene film impregnated with the ion conductive resin solution. The coated porous polypropylene film was dried at 60 DEG C for 2 hours. The dried porous polypropylene film was impregnated with deionized water to remove propylene carbonate to finally prepare a redox flow battery separator.

Comparative Example 1

The membrane was used as a separator without further treatment on SF-601 (polyethylene porous separator containing silica, thickness: 0.6 mm, porosity: 50 to 60%).

Comparative Example 2

A separator for a redox flow battery was prepared in the same manner as in Example 1 except that 30 wt% of n-methyl-2-pyrrolidone (NMP) solvent was used in place of 30 wt% of propylene carbonate in the ion conductive resin solution .

Experimental Example 1: Cross section observation of membrane

The cross section of the separation membrane of Example 1 was photographed by scanning electron microscope and is shown in Fig. According to Fig. 2, it was confirmed that the thickness of the porous substrate filled with pores of Nafion was 18 mu m and the thickness of the coating layer made of nafion was 3 mu m.

Experimental Example 2: Incineration X-ray scattering (SAXS; Diameter measurement of hydrophilic ion clusters by small angle x-ray scattering

Diameters of the hydrophilic ion clusters included in the separation membrane were determined by measuring the separation membranes of Example 1 and Comparative Example 2 with SAXS (RIGAKU, D / MAX-2500). Specifically, the wavelength (?) Of the X-ray beam used in the experiment was 1.5406 nm, the scattering pattern result was analyzed, and the analysis result was substituted into the general formulas 1 to 4 to calculate the diameter ( d _c ) And the results are shown in Table 1 below.

[Formula 1]

d _c = (6 Vc /?) ^1/3

In the above general formula (1), Vc is a volume of cubic lattice determined by the following general formula (2)

[Formula 2]

Vc = {Δ V / (1 + Δ V)} d 3 + N P V P

D is the Bragg spacing determined by the following general formula 3, N _P is the number of ion exchange sites, V _P is the volume of the ion exchange site volume of ion exchange site), DELTA V is the volume change of the membrane before and after water swelling,

[Formula 3]

d (Bragg spacing) = 2? / q

In Formula 3, q is a scattering factor determined by the following Formula 4,

[Formula 4]

q = (4? /?) * sin (2? / 2)

In the general formula (4),? Is the wavelength of the X-ray and? Is the scattering angle.

In the formula 2, N _P and Δ V are obtained by the following general formulas 5 and 6, respectively.

[Formula 5]

N _{P = [N A ρ P / M} eq (1 + Δ V] d 3

In Equation 5, N _A is Avogadro's number, M _eq is equivalent weight, ρ _P is the density of the membrane, and Δ V is the number expansion of the membrane, water swelling) volume change,

[Formula 6]

Δ V = ρ _P Δm / ρ _w

In Equation (6),? M is the change amount of the mass before and after the water swelling of the separator, and ? _W is the density of water.

Diameter of ion cluster (nm) Example 1 6.09 Comparative Example 2 4.75

According to Table 1, it was confirmed that the diameter of the ion clusters of Example 1 was larger than the diameter of the ion clusters of Comparative Example 1.

Experimental Example 3: Evaluation of charging / discharging performance

In order to confirm the performance of the separator of Example 1 and Comparative Example 1, a unit cell was fabricated as shown in FIG. The unit cell includes a flow frame 50 for forming a flow path so that the electrolyte can move symmetrically to the separation membrane 60, an electrode 40 for moving electrons, an end plate 30 serving as a unit cell shape support and support Consists of. The electrolytic solution of the electrolytic solution container is supplied to a unit cell through a pump and charged and discharged by applying an electric current through a charge / discharge unit 70.

The electrolytic solution stored in the electrolyte container contains ZnBr ₂ (2.25M), ZnCl ₂ (0.5M), Br ₂ (5mL / L) and 1-methyl-1-ethyl pyrrolidonium bromide Each of the cathodes was 30 mL, and the supply rate of the electrolyte supplied from the electrolytic circulation pump was 70 RPM per minute.

The single cells produced from the separators of Example 1 and Comparative Example 1 were subjected to one cycle of charging and discharging, one cycle of stripping was set to one cycle, and energy efficiency, voltage efficiency and charge efficiency were measured, Lt; tb >

At this time, Wonatec product was used as a charge / discharge device. Under the room temperature condition, the total charge amount of the system was 2.98 Ah, the electrolyte utilization rate was 40% (SOC 40), the charge was 20 mA / cm 2 and the discharge was 20 mA / cm 2.

unit: % Energy efficiency Voltage efficiency Charge efficiency Example 1 80.3 86.9 92.5 Comparative Example 1 73.4 83.1 88.3

4 is a graph showing the results of the charge and discharge performance evaluation according to the embodiment of the present invention. As can be seen from Table 2, the unit cell including the separator of Example 1 includes the separator of Comparative Example 1 It was confirmed that energy efficiency, voltage efficiency and charge efficiency were significantly better than those of the conventional method.

30: End plate
40: electrode
50: Flow frame
60: membrane
70: charge / discharge unit
100: Porous substrate
110: Groundwork
210: ion conductive resin solution
230, 240: Coating layer
250: ion conductive resin

Claims (19)

A porous substrate; And
And an ion conductive resin filled in the pores of the porous substrate,
Wherein the ion conductive resin comprises a hydrophilic ion cluster.
The method according to claim 1,
Wherein the hydrophilic ion cluster has a hydrophilic ion cluster diameter of 5.5 to 7 nm as measured by small-angle X-ray scattering (SAXS).
The method according to claim 1,
Wherein the hydrophilic ion clusters have a diameter ( d _c ) of 5.5 to 7 nm according to the following general formula (1), which is obtained by the measurement by small-angle X-ray scattering (SAXS)
[Formula 1]
d _c = (6 Vc /?) ^1/3
In the above general formula (1), Vc is a volume of cubic lattice determined by the following general formula (2)
[Formula 2]
Vc = {Δ V / (1 + Δ V)} d 3 + N P V P
D is the Bragg spacing determined by the following general formula 3, N _P is the number of ion exchange sites, V _P is the volume of the ion exchange site volume of ion exchange site), DELTA V is the volume change of the membrane before and after water swelling,
[Formula 3]
d (Bragg spacing) = 2? / q
In Formula 3, q is a scattering factor determined by the following Formula 4,
[Formula 4]
q = (4? /?) * sin (2? / 2)
In the general formula (4),? Is the wavelength of the X-ray and? Is the scattering angle.
The method according to claim 1,
And a coating layer disposed on at least one side of the porous substrate,
Wherein the coating layer comprises an ion conductive resin.
5. The method of claim 4,
Wherein the coating layer and the porous substrate have a thickness ratio of 1: 3 to 300.
The method according to claim 1,
The porous substrate has an average porosity of 30 to 70% by volume,
Wherein the porous substrate has pores having an average particle size of 10 to 200 nm.
The method according to claim 1,
The porous substrate includes at least one selected from the group consisting of polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polyamide, polyimide, polybenzoxazole, polyethylene terephthalate, polyethylene, polysulfone and polyether sulfone Separator for redox flow battery.
The method according to claim 1,
The ion conductive resin may be at least one selected from the group consisting of a sulfonated tetrafluoroethylene-based polymer, a sulfonated polyimide (sPI), a sulfonated poly (arylene ether sulfone), sPAES, , Sulfonated polyetheretherketone (sPEEK), sulfonated polyetherketone (sPEK), polyvinylidene fluoride-graft-poly (styrene sulfonic acid, PVDF-g-PSSA, and sulfonated poly (fluorenyl ether ketone).
9. The method of claim 8,
The sulfonated tetrafluoroethylene-based polymer may be selected from the group consisting of Nafion ^® , Dupont, Aquivion ^® , Solvay, Flemion ^™ , AGC chemicals company, or Aciplex ^™ (Asahi Kasei) , Separator for redox flow battery.
The method according to claim 1,
Wherein the ion conductive resin is contained in an amount of 20 to 70% by weight based on the total weight of the separator.
The method according to claim 1,
Further comprising silica filled in the pores of the porous substrate.
12. The method of claim 11,
The silica is wet silica, dry silica or mixtures thereof,
The wet silica has an average particle diameter of 100 to 200 nm,
Wherein the dry silica has an average particle diameter of 4 to 30 nm.
Filling an ion conductive resin solution containing an ion conductive resin, propylene carbonate and an organic solvent in the pores of the porous substrate;
Drying the porous substrate filled with the ion conductive resin solution in the pores; And
And impregnating the dried porous substrate with deionized water to remove the propylene carbonate.
14. The method of claim 13,
The content of the ion conductive resin is 2 to 20% by weight based on the total weight of the ion conductive resin solution,
Wherein the content of the propylene carbonate is 1 to 50% by weight based on the total weight of the ion conductive resin solution.
14. The method of claim 13,
Wherein the ion conductive resin solution further comprises silica.
14. The method of claim 13,
The organic solvent is selected from the group consisting of n-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc), dipropylene glycol (DPG), ethylene glycol (EG), propylene glycol Alcohol (IPA). ≪ RTI ID = 0.0 > 11. < / RTI >
14. The method of claim 13,
Further comprising coating the ion conductive resin solution on at least one surface of the porous substrate filled with the ion conductive resin solution to form a coating layer.
14. The method of claim 13,
Further comprising a post-treatment step of immersing the porous substrate from which the propylene carbonate has been removed in a solution containing at least one selected from the group consisting of water, sulfuric acid and hydrogen peroxide.
12. A redox flow cell comprising the separator of any one of claims 1 to 12.

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