WO2016064181A1 - Method for reducing membrane permeability of vanadium ion, and vanadium redox battery comprising membrane prepared by same - Google Patents

Abstract

The present invention relates to a method for reducing permeability of a vanadium ion of a cation exchange membrane. Moreover, the present invention relates to a vanadium redox battery which comprises a membrane that has been modified by means of the method such that a vanadium ion, which is to be used in the vanadium redox battery, has low permeability.

Description

Method for reducing membrane permeability for vanadium ions and vanadium redox battery comprising membrane prepared by the method

This application claims the benefit of the date of application of Russian Patent Application No. 2014142533, filed with the Russian Patent Office on October 21, 2014, the entire contents of which are incorporated herein.

The present invention relates to a method for reducing the permeability to vanadium ions of a cation exchange membrane. The invention also relates to a vanadium redox battery comprising a membrane modified by the method to provide low permeability to vanadium ions for use in a vanadium redox battery.

While industrial development requires more and more energy, the world reserves of non-renewable energy sources are rapidly and continually depleted, which has led to the discovery of new energy sources and the development of methods for their industrial use in modern science and industry. Made one of our top priorities. The lack of powerful energy batteries is a major challenge for large-scale implementation of sustainable energy, solar and wind as alternative renewable energy sources. The lack of energy-intensive batteries that can be charged quickly is also a major constraint that hinders large-scale manufacturing and use of electric vehicles.

Recent vanadium redox batteries are considered as one of the most promising new batteries due to the particular combination of energy efficiency, capital cost, lifecycle cost and the absence of specific requirements [G. Kean, AA Shah, FC Walsh. Int . J. Energy Res., 2011, DOI: 10. 1002 / er . 1863 ]. In redox batteries, two redox couples are used as the electroactive material for energy storage by oxidation and reduction reactions. As described in some publications [A. Rarasuraman, TM Lim, C. Menictas, M. SKyllas-Kazacos. Review of material research and development for vanadium redox flow battery applications. Electrochimica Acta , 101 (2013) 27-40; AU Patent No. 575247, AU Patent No. 696452, AU Patent No. 704534, US Patent Nos. 6143443 and 6562514], the principle of action of vanadium redox batteries is based on the ability of vanadium to exist at four oxidation degrees V (II), V (III), V (IV) and V (V). The general battery comprises a tank having an anode electrolyte containing the tank and V (II) / V (III ) having a pair of cathode electrolyte containing the VO ₂ ⁺ / VO ²⁺ pair. The electrolyte from the tanks circulates through a stack of electrochemical cells connected in series or in parallel by a pump to react with the inert electrodes. Each electrochemical cell comprises a negative half cell containing a ₂ ⁺ VO and VO ²⁺ ion positive half-cell and V (III) and V (II) ion-containing. The two half cells are isolated by an ion exchange membrane (IEM), which allows vanadium ions with different oxidation states to move through the membrane, which can result in a loss of battery operating capacity when mixed. It is the main component of the battery to prevent. Thus, in addition to low permeability to vanadium ions, the ideal membrane should have high hydrogen conductivity, good chemical stability in acidic solutions, high stability to oxidizers V (V) and reducing agent V (II) and high mechanical strength.

The above-mentioned conditions because perfluorinated membranes made from sulfo-containing copolymers such as Nafion® having different amounts of sulfo residues made in DuPont have high hydrogen conductivity, good durability against electrolyte solutions and sufficiently high mechanical strength. Most satisfied with them. The main disadvantage of such membranes is their high vanadium ion permeability, which is the reason for the self-discharge rate of the battery which leads to a decrease in the effect of the battery.

Many attempts have been reported early to reduce membrane permeability for vanadium ions and to improve membrane operating parameters.

One such attempt is the use of membranes made of alternative polymeric materials and the development of "sandwich" type composite membranes. Polysulfones and derivatives thereof are alternative polymers and copolymers (eg EP patent 0790658), mixtures of two or more polymers (eg US patent application 2011/0136016), copolymers (eg US patent application No. 2011/0318644 and No. 2012/0196188, X. Luo et al., J. Phys. Chem . B, 2005, 109, 20310-20314 ), polypropylene / sulfo polyetheretherketone treated with tungstophosphoric acid [ C . Jia et al., is used to J. Power Sources, 2010, 195, 4380-4383]. However, a common disadvantage of all the aforementioned methods is that the reduction in membrane permeability for vanadium ions is insufficient compared to Nafion membranes (approximately 2-10 times).

Many attempts have been made to modify Nafion membranes to reduce the permeability of vanadium ions, for example applying an isophthaloyl dichloride coating to the surface of a Nafion polyanion or polycation via interfacial polymerization on the surface of the Nafion membrane. To convert the sulfo groups incorporated in the complex of polyethyleneimine adsorbed on the Nafion surface to chloro-sulfo groups. [QTLuo, HM Zhang, J. Chen, P. Qian, YF Zhai , J. Membr . Sci ., 2008, 311, 98 ], to obtain a polycation barrier by chemical polymerization of pyrrole and aniline on the membrane surface [B. Schwenzer, S. Kim, M. Vijayakumar, ZG Yang, J. Liu, J. Membr . Sci ., 2011, 3 372, 11 ; J. Zeng, C. Jiang, Y. Wang, J. Chen, S. Zhu, B. Zhao, R. Wang, Electrochem . Commun ., 2008, 10, 372 ], blocking the surface with an inorganic material such as tetraethoxysilane via a sol-gel reaction carried out in situ [J. Xi, Z. Wu, X. Qiu, L. Chen, J. Power Sources, 2007, 166, 531 ; D. Schulte, J. Drillkens, B. Schulte, DU Sauer, J. Electrochem . Soc ., 2010, 157, A989 ; X. Teng, Y. Zhao, J. Xi, Z. Wu, X. Qiu, L. Chen, J. Membr . Sci ., 2009, 341, 149 ; N. Wang, S. Peng, D. Lu, S. Liu, Y. Liu, K Huang, J Solid State Electrochem ., 2011, 1 ], or compounding with polyvinylidene fluoride [Z. Mai, H. Zhang, X. Li, S. Xiao, J. Power Sources, 2011, 196, 5737 ]. Attempts to modify the Nafion membrane described above provide a reduction in permeability to vanadium ions, resulting in a decrease in self discharge rate and an increase in coulomb efficiency and energy efficiency compared to the original Nafion membrane. However, the foregoing attempts can reduce the membrane permeability of vanadium ions up to 10 times. See, B. Schwenzer, S. Kim, M. Vijayakumar, ZG Yang, J. Liu, J. Membr . Sci ., 2011, 372, 11 ] showed that aniline polymerization on the surface of Nafion membranes reduced the membrane permeability of vanadium ions by more than two orders of magnitude, but more accurate data using available analytical methods Did not provide.

The closest approach to the invention is described in LANeves, J. Benavente, IM Coelhoso, JG Crespo. J. Membr . Sci ., 2010, 347, 42 and LANeves, IM Coelhoso, JG Crespo. J. Membr . Sci ., 2010, 360, 363 , which describe the introduction of large amounts of cationic surfactants into the Nafion membrane for fuel cells in the form of ionic liquid cations. The main purpose of this document was to reduce the moisture net loss occurring in the Nafion membrane at high temperatures, which adversely affects membrane performance in fuel cells. The cationic surfactant was added to the membrane by incubating the membrane in 40% (w / w) aqueous solution of the surfactant. The cationic surfactant was actually embedded in the Nafion membrane, the degree of incorporation of the surfactant in the membrane reached to the maximum (up to approximately 90% of the Nafion sulfonate groups associated with the surfactant), which was constant after about 20 hours of incubation It was shown that this resulted in a significant decrease in membrane permeability for methanol and gas. The moisture loss at high temperatures of the modified membranes was significantly reduced. However, the document is not intended to reduce the membrane permeability of vanadium ions, and this study does not include evidence that the modification of the membrane by cationic surfactants affects the permeability of vanadium ions.

Another group of researchers reported: WU Xue-Wen, LIU Su-Qin, HUANG Ke-Long. Characteristics of CTAB as Electrolyte Additive for Vanadium Redox Flow Battery. Journal of Inorganic Materials Vol. 2010, 25 No. 6. 641- 646] have described the use of a cationic surfactant cetyltrimethylammonium bromide (cetyltrimethylammonium bromide) as an electrolyte additive, designed for the vanadium redox battery. The introduction of surfactant into the electrolyte composition increases the concentration of the electrolyte by increasing the solubility of V (V) ions, promotes the oxidation / reduction reaction V (IV) / V (V), improves the operation of the electrode, It has been shown to have a positive effect on battery performance because of lower transport resistance. However, the reduction of membrane permeability for vanadium ions was not the purpose of this study, and there was no evidence that the above modification with cationic surfactants had an effect on membrane permeability for vanadium ions.

Thus, in recent years, there is a significant need for the development of a simple and feasible method for using modified membranes in vanadium redox batteries, especially in Nafion, which significantly reduces the permeability of cation exchange membranes to vanadium ions.

The present invention relates to a method for reducing the permeability to vanadium ions of a cation exchange membrane. The present invention also provides a vanadium redox battery comprising a membrane modified by the method to provide low permeability for vanadium ions for use in a vanadium redox battery.

One embodiment of the present invention provides a method for reducing the permeability of a membrane to vanadium ions. Specifically, the method includes introducing the cationic surfactant to the membrane surface and at least a portion of the membrane by incubating the membrane in an aqueous solution or saline solution containing the cationic surfactant or a mixture of the cationic surfactant. According to one example, the membrane is a cation exchange membrane. According to another example, the membrane is a polymer membrane having sulfo groups.

According to the present invention, the decrease in permeability to vanadium ions is achieved by introducing a cationic surfactant (cS) into the membrane by incubating the membrane in an aqueous solution or saline solution containing a cationic surfactant or a mixture of the cationic surfactants. . The term “incorporation of a surfactant into the membrane” means that the cationic surfactant (cS) can be located on the surface of the membrane and / or inside the membrane, preferably both on and inside the membrane. .

The method according to this embodiment of the present invention allows to reduce the membrane permeability to vanadium ions, 5 times, more preferably about 10 times compared to the original unmodified membrane permeability when measuring the permeability of vanadium ion VO ²⁺ More preferably about 100-fold, even more preferably about 1,000-fold, even more preferably about 10,000-fold, even more preferably about 100,000-fold or more.

Another embodiment of the present invention provides an vanadium redox battery comprising an anode, a cathode, and a separator provided between the anode and the cathode, wherein the separator is a membrane manufactured by the above-described method.

Another embodiment of the present invention includes an anode, a cathode and a separator provided between the anode and the cathode, wherein the separator is a cationic surfactant or a mixture of cationic surfactants on at least part of the surface of the membrane and inside the membrane. It provides a vanadium redox battery that is a film provided in. Such a film can be prepared by the method described above.

The membrane according to the embodiments of the present invention has a low permeability to vanadium ions, 6x10 ^-7 cm ² min ^-1 or less, 5x10 ^-7 cm ² min ^-1 or less, when measuring the permeability of vanidyl ion VO ²⁺ , more Preferably 1x10 ^-7 cm ² min ^-1 or less, even more preferably 1x10 ^-8 cm ² min ^-1 or less, even more preferably 1x10 ^-9 cm ² min ^-1 or less, even more preferably 1x10 ^-10 cm ² min ^-1 or less.

The vanadium redox flow battery comprising the modified membrane according to the present invention has a low permeability to vanadium ions, so that a high concentration of salt does not break the bond between the membrane and the surfactant.

The method according to one embodiment of the present invention is a method of reducing the permeability of vanadium ions of the membrane.

Specifically, the method includes introducing the cationic surfactant to the membrane surface and at least a portion of the membrane by incubating the membrane in an aqueous solution or saline solution containing the cationic surfactant or a mixture of the cationic surfactant.

In the present invention, the term "incubation" means exposing the membrane to a solution. Exposure includes contact.

According to one embodiment, the membrane is a cation exchange membrane. The membrane used as the cation exchange membrane is not particularly limited. For example, the cation exchange membrane to the anionic groups such as sulfo _{(-SO 3 H), -SO 3} - M +, -COOH, -COO - M +, -PO 3 H 2, -PO 3 H - M ⁺ and -PO ₃ ^2- 2M ⁺ of the polymer film may be used having at least one functional group, where M is a monovalent cation, such as Li, Na or K cations.

According to another embodiment, the membrane is a polymer membrane having sulfo groups.

According to the above embodiment, when the sulfo group-containing cation exchange polymer membrane is incubated in an aqueous solution or saline solution containing a cationic surfactant (cS) or a mixture of the cationic surfactant, the cationic surfactant charged opposite to the membrane. By introducing (cS), a decrease in permeability to vanadium ions is achieved.

According to another embodiment, the cationic surfactant has a hydrophobic moiety, and the membrane includes a hydrophobic fragment. The hydrophobic moiety of the cationic surfactant and the hydrophobic fragment of the membrane can have a hydrophobic interaction. For example, the hydrophobic moiety of the cationic surfactant is an alkyl moiety.

Experimental studies conducted by the present inventors (more specifically Examples 4 and 5) show that most of the amount of surfactant in the membrane by exposing sulfo containing membranes, such as Nafion-117, in a solution of cationic surfactant. Is bound (approximately surfactant 1 ions per sulfo group of the membrane), and no significant leaching of the cationic surfactant (cS) from the membrane occurs even if the membrane is incubated for a long time in distilled water or heated in water and / or sulfuric acid. It was. Thus, the main action force of the cationic surfactant binding to the membrane is the electrostatic interaction between the groups of the cationic surfactant and the sulfo groups of the membrane, while between the alkyl moiety of the surfactant and the hydrophobic fragment of the membrane. Hydrophobic interactions could be assumed to provide additional stabilization of the final structure.

According to the present invention, as the polymer membrane having the sulfo group, a sulfone group-containing polymer membrane prepared by an industrial or experimental method for film formation can be used, and non-limiting examples are tetrafluoro having different content of sulfo groups. Copolymers of ethylene, such as Nafion®, can be used. Specifically, Nafion 112, Nafion 115, Nafion 117, Nafion 125, Nafion 212, Nafion NR211, Nafion NR212, Nafion 1110, Nafion XL and the like.

The membrane may comprise two or more materials, examples of which include one or two or more polymers comprising sulfo groups, and / or one or two or more polymers containing carboxyl groups, and / or phosphor-groups. One or two or more polymers, and further one or two or more nonionic polymers.

According to one embodiment, the membrane may be subsequently heated in a hydrogen peroxide solution, in a sulfuric acid solution, and in distilled water prior to modification with a cationic surfactant.

According to one embodiment, the membrane may be subjected to subsequent boiling in a hydrogen peroxide solution, in a sulfuric acid solution, and in distilled water after modification by a cationic surfactant.

According to an exemplary embodiment, the membrane may be continuously boiled in hydrogen peroxide solution, sulfuric acid solution, and distilled water before and after reforming by a cationic surfactant.

According to one embodiment, the cationic surfactant includes a compound represented by Formula 1 or Formula 2 or a mixture thereof.

[Formula 1]

[Formula 2]

In Chemical Formulas 1 and 2,

R ₁ is hydrogen, methyl or ethyl,

R ₂ is hydrogen, methyl, ethyl, phenyl, phenylmethyl, hydroxymethyl or hydroxyethyl,

R ₃ is hydrogen, C ₁ to C ₂₀ alkyl, C ₆ to C ₂₀ aryl, C ₇ to C ₂₀ arylalkyl, C ₁ to C ₂₀ hydroxyalkyl, (CH ₂ CH ₂ O) _n R, Or (CH ₂ ) _p COO ⁻ , where n is an integer from 4 to 100, R is hydrogen or alkyl of C ₁ to C ₂₀ , p is an integer from 1 to 12,

R ₄ is C ₈ to C ₂₀ alkyl, C ₈ to C ₂₀ hydroxyalkyl, -COOR ',-R "COOR"' or -R "OCOR"', where R' and R "'are C ₈ To C ₂₀ alkyl, R ″ is C ₁ to C ₃ alkylene;

R ₅ is C ₈ to C ₂₀ alkyl, -COOR ',-R "COOR"' or -R "OCOR"', where R' and R "'are alkyl of C ₈ to C ₂₀ and R" is C ₁ to C ₃ alkylene;

X is an anionic group.

According to one example, R ₁ is H, —CH ₃ , or —C ₂ H ₅ .

According to one embodiment, R ₂ is H, —CH ₃ , —C ₂ H ₅ , —C ₆ H ₅ , —CH ₂ C ₆ H ₅ , —CH ₂ OH, or —C ₂ H ₄ OH.

According to one embodiment, R ₃ is H, -CH ₃ , -C ₂ H ₅ , -C ₆ H ₅ , -CH ₂ C ₆ H ₅ , -CH ₂ OH, -C ₂ H ₄ OH, (CH ₂ CH ₂ O) _n R (where n is an integer from 4 to 100, R is hydrogen or C ₁ -C ₂₀ alkyl), C ₈ -C ₁₈ alkyl.

According to one example, R ₄ is C ₈ -C ₂₀ alkyl, (CH ₂ ) _m OH (where m is an integer from 8 to 20) or — (CH ₂ ) _k OC (O) (CH ₂ ) _l where k Is an integer of 1 to 3, l is an integer of 8 to 18).

According to one example, R ₅ is C ₈ -C ₂₀ alkyl, or — (CH ₂ ) _k OC (O) (CH ₂ ) ₁ , where k is an integer from 1 to 3 and l is an integer from 8 to 18. .

In one example, X is _{^{-Cl -, -Br -, -CH 3}} OSO 3 -, or -C ₂ H ₅ OSO ₃ ^- a.

According to one embodiment, the cationic surfactant includes a surfactant having a double tail, and examples thereof include didecyldimethylammonium bromide, dioctadecyldimethylammonium bromide and the like.

According to one embodiment, the cationic surfactant includes betaine, for example, GENAGEN alkylamidopropyl betaines (CABN) and GENAGEN alkyldimethyl betaines (LAB), which have C ₈ -C ₁₈ alkyl. It is provided by GLOBALAMINES.

According to one embodiment, the cationic surfactant has a hydroxyl group in the side chain, for example Praepagen HY.

According to one embodiment, the introduction of the cationic surfactant into the membrane may cause the membrane to be in an aqueous solution or saline solution containing the cationic surfactant or a mixture thereof from about 100 ^° C. to about 10 ^o can be carried out by maintaining at a temperature of C. Reducing the temperature can reduce the adsorption rate of the cationic surfactant in the membrane and can reduce the solubility of the cationic surfactant, thus increasing the time required for membrane incubation in solution.

According to one embodiment, the concentration of cationic surfactant in the solution is about 10 ^-5 M to about 1 M, preferably 10 ^-3 M to 0.5 M, more preferably 10 ^-2 M to 0.1 M. Lowering the surfactant concentration below ^5-10 mM may need to increase the incubation time of the membrane in solution.

The absolute amount of cationic surfactant in the solution is determined by the degree of packing D of the desired membrane:

D = [cS] _bound / [SO ₃ H] _membr (1)

Wherein [cS] _bound is the amount of cationic surfactant _bound to the membrane (molar number) and [SO ₃ H] _membr is the absolute amount of sulfo residues in the membrane (molar number).

[SO ₃ H] _membr = (m-m _H2O ) / 1100

Where m is the mass (gram, g) of the swollen membrane, m _{H 2 O} is the mass of water in the sample calculated from the experimentally determined degree of swelling of the membrane, and 1100 is the gram equivalent of Nafion 117 used in the examples. And dry Nafion weight per sulfo group. If another polymer is used as the material of the membrane, 1100 may be replaced by the dry weight per sulfo group of the polymer.

The absolute amount of cationic surfactant in the solution required to obtain the desired degree of packing D is determined by equation (1) assuming that the surfactant binds quantitatively, so [cS] _bound is the value of the cationic surfactant in the solution. Equivalent to the total amount. If it is desired to obtain the maximum degree of filling of the membrane, the surfactant in solution may be present in excess.

The retention time of the membrane in the cationic surfactant or a mixture solution of the cationic surfactant may be determined by the concentration of the cationic surfactant, the chemical properties of the cationic surfactant and the membrane, and the processing temperature. In general, the membrane incubation time in the surfactant solution varies from about 1 hour to several weeks, more preferably from 10 hours to 48 hours.

According to an exemplary embodiment, the cationic surfactant solution may further include at least one of inorganic and / or organic salts and alkali metal ions.

As the inorganic and / or organic salt, water-soluble low molecular weight materials may be used, such as chloride, bromide, sulfate, phosphate, carbonate, acetate, oxalate and the like. Examples of the metal counterion include sodium, potassium, lithium, cesium, calcium, magnesium, lanthanum, copper, nickel ions, and the like. The fact that the modified membrane maintains extremely low permeability to vanadium ions when left in contact with high salt and acid concentrations (eg, 1 M MgSO ₄ , 1 M VOSO ₄ , 2.5 MH ₂ SO ₄ ) (at least 3 weeks). Indicates that such high concentrations of salts do not break the bond between the membrane and the surfactant and consequently do not interfere with the bond.

According to one embodiment, the cationic surfactant solution may further include an inorganic or organic acid. Examples of the inorganic or organic acid include hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, citric acid and the like.

The process according to the invention is 5 times, more preferably about 10 times, even more preferably about 100 times, even more preferably about 1,000 times, even more when comparing the membrane's permeability to vanadium ions with its original unmodified membrane permeability. Preferably at least about 10,000 times, even more preferably at least about 100,000 times.

Membranes obtained by the introduction of cationic surfactants by the method according to the invention have a low permeability to vanadium ions, 6x10 ^-7 cm ² min ^-1 or less, more preferably when measuring the permeability of vanadium ions VO ^{2+ 1} × ^{10 −7} cm ² min ⁻¹ or less, even more preferably ¹ × 10 ⁻⁹ cm ² min ⁻¹ or less, even more preferably ¹ × ^{10 −10} cm ² min ⁻¹ or less.

According to one embodiment, there is provided a vanadium redox battery comprising an anode, a cathode and a separator provided between the anode and the cathode, wherein the separator is a membrane manufactured by the above-described method.

According to one embodiment, an anode, a cathode and a separator provided between the anode and the cathode, the separator is a cationic surfactant or a mixture of the cationic surfactant is a membrane provided on the surface of the membrane and at least part of the inside of the membrane It provides a vanadium redox battery.

Determination of Membrane Vanadium Permeability for Ions

Membrane permeability for vanadium ions is characterized by the permeability of vanadil ion V (IV) using a cell consisting of two identical half cells separated by the studied membrane. A 1 M VOSO ₄ aqueous solution in 2.5 M sulfuric acid was placed in one half cell through a specific opening and 1 M MgSO ₄ solution in 2.5 MH ₂ SO ₄ was placed in another half cell. The volume of each solution was 0.8 ml and the working area of the membrane in contact with the VOSO ₄ / MgSO ₄ solution was 0.875 cm ² . The filled cell was left at room temperature without stirring. To determine the permeability of the initial (unmodified) membrane, 10-200 mkl aliquots are taken from a half cell containing MgSO ₄ after 30-60 minutes after filling for further measurement of vanadium ion concentration through the membrane. It was. When determining the permeability of the modified membrane, aliquots of the solution were taken from the half cell containing MgSO ₄ 4-30 days after filling.

The vanadium ion concentration was measured as follows using a color reaction with 4- (2-pyridylazo) resosocinol (4- (2-pyridylazo) resorcinol (PAR)). In a 10 ml volumetric flask, approximately 1 volume of 1 M Na-acetate buffer (pH 6.5), 0.5 ml of PAR 0.1% aqueous solution, the sample solution and 2.5 M sulfuric acid to neutralize the pH to 6.2-6.7 5M NaOH was added. The solution volume was adjusted to the required value (10 ml) with distilled water (distilled twice). The volume (separation) of the test solution was chosen such that the final vanadium concentration in the volumetric flask containing PAR was in the range of about 4 × 10 ⁻⁶ to 2 × 10 ⁻⁵ M. The solution was mixed thoroughly and the absorption spectra were recorded in the 450-600 nm range and the optical density was measured at a wavelength of 540 ± 2 nm corresponding to the maximum absorbance of the composite PAR-V (IV) at pH 6.2-6.7.

As a control, all reagents (acetate buffer, PAR and NaOH), except that an aliquot of a 1 M solution of MgSO ₄ in 2.5 MH ₂ SO ₄ was added in a volume equivalent to that of the corresponding sample solution instead of the sample solution. A solution containing was used.

The extinction coefficient (e _M ) was determined by a calibration curve according to Bouguer-Lambert A = (A ⁵⁴⁰ -A ⁵⁴⁰ k) = e _M lc, where A ⁵⁴⁰ Is the optical density of the analyte complex with PAR at 540 nm, A ⁵⁴⁰ _k is the optical density of the control solution with PAR at 540 nm, e _M is the molar extinction coefficient, l is the optical path, c is the concentration of V (IV) which is the vanadyl ion which forms a complex with PAR. PAR is present in sufficient excess. The experimentally measured e _M is e _M ⁵⁴⁰ = 3.57 10 ⁴ lx mol ^{- 1} x cm ^{- 1} , which is described for the PAR complex with V (V) in the concentration range 0.1-1.2 mkg / ml [ J. Schneider, lJ Csanyi , Mikcohimica Acta, 1976, coincides with the II, 271- 282] The ^{_{e M 545 = 3.45 10 4 lx}} mol -1 x cm -1 reported.

In order to demonstrate the aforementioned method of measuring vanadium ions in the presence of sulfuric acid and magnesium sulfate, a specific control study with vanadium standard solution was conducted. That is, 10 mkl of standard VOSO ₄ solution (1 mg / ml) was added to a set of 10 ml volumetric flasks, each containing 1 ml of 1 M Na-acetate buffer (pH 6.5), 0.5 ml of 0.1% aqueous PAR solution, and 2.5 MH. ₂ contains a 1 M MgSO ₄ 0 to 0.8 ml of SO _4. The corresponding equivalent volume of 5 M NaOH (ie 0-0.8 ml) was added to each flask for neutralization. After mixing the reagents, the volume of the sample was adjusted to 10 ml with distilled water (distilled twice). The pH of the obtained sample was adjusted in the range of 6.2 to 6.5. Quantification of the A = (A ⁵⁴⁰ -A ⁵⁴⁰ k) values obtained under different contents of MgSO ₄ and H ₂ SO ₄ was carried out to determine the amount of vanadium sulfate with magnesium sulfate with a final concentration of up to 0.25 M and sulfuric acid (up to 0.25 M). It does not affect the accuracy and correctness of the.

The concentration of V (IV) in the complex with PAR was calculated from the Burger-Lambert equation using experimentally measured optical densities A ⁵⁴⁰ and A ⁵⁴⁰ _k and experimentally measured extinction coefficients. To determine the concentration of V (IV) in the half cell that passed through the membrane, i.e. with MgSO ₄ , the dilution of the sample was considered as follows when preparing the complex with PAR: C _{V (IV)} = C _{meas X} V _flask / V _sample , where C _{V (IV)} is the vanadium ion concentration in the half cell containing magnesium sulfate, C _meas is the measured vanadium concentration in the complex with PAR, and V _flask is the preparation of the complex with PAR The volume of the volumetric flask used (usually 10 ml) and V _sample is the volume of aliquot taken from the half-cell with MgSO ₄ and added to the volumetric flask to prepare a complex with PAR.

Vanadium (IV) membrane permeability for ions (P) is described in [ChuankunJia, Jianguo Liu , Chuanwei Yan . Journal of Power Sources, was calculated according to the equation (2) given in 2010, 195, 4380-4383]:

V × c (t) / t = S × P / L (c _A -c (t)), (2)

Where P is the membrane permeability (cm ² min ⁻¹ ), V is the volume of the solution in the half-cell containing magnesium sulfate (0.8 ml in this case), and c (t) is MgSO at time t after cell filling. Experimentally measured concentration of vanadium ions in a half-cell containing ₄ ,

t is the time in minutes,

S is the membrane area in contact with the solution (S = 0.785 cm ² in this case),

L is the thickness of the membrane in cm

c _A is the initial concentration of vanadium ions in the half-cell containing VOSO ₄ (1 M).

Naturally, the rate of dispersion of ions through the membrane depends on the difference in their concentration on both sides of the membrane and therefore decreases with time. Therefore, the transmittance value calculated from relation (2) is leveled with time. In cases where the permeability of the membrane is low, the rate of ion dispersion can be estimated to be nearly constant over time ( J. Xi et all, J. Mater. Chem., 2008, 18, 1232-12314) .

The thickness of the membrane was measured in micrometers.

Membranes according to some embodiments of the present invention have a low permeability to vanadium ions. The permeability is 6x10 ^-7 cm ² min ^-1 or less, 5x10 ^-7 cm ² min ^-1 or less, more preferably 1x10 ^-7 cm ² min ^-1 or less, even more preferably, when measuring the permeability of vanadil ion VO ²⁺ . 1 × 10 ⁻⁹ cm ² min ⁻¹ or less, even more preferably ¹ × ^{10 −10} cm ² min ⁻¹ or less.

In membranes according to embodiments of the invention, the number of cationic groups of the cationic surfactant per one anionic group (eg, sulfo group) in the membrane is from about 0.01 to about 2, preferably from about 0.2 to about 1, more preferably about 0.5 to about 1.

The thickness of the film can be determined depending on the purpose.

According to the present invention, surfactant modifications result in a significant decrease in membrane ion conductivity.

Exemplary embodiments of the present invention may be applied to the construction and manufacturing method of a vanadium redox battery known in the art, except for including the membrane. The vanadium redox battery stores an anode electrolyte and supplies the anode electrolyte to the anode, an anode electrolyte storage part for receiving the anode electrolyte leaked from the anode, a cathode electrolyte, a cathode electrolyte supplied to the cathode, and a cathode The method may further include a cathode electrolyte storage unit configured to receive the spilled cathode electrolyte.

Although the invention is described in more detail in the following examples, the details described herein should not be construed as limitations.

Example

Example 1 (comparative example)

The Nafion membrane (Nafion 117, DuPont) was continuous in distilled water (1 hour), 3% H ₂ O ₂ (1.5 hours), distilled water (1 hour), 0.5 MH ₂ SO ₄ (1.5 hours), distilled water (1 hour) Prepared by boiling. The permeability of the membrane to ion V (IV) was measured using the method described above. The thickness of the swollen film in water or in 2.5 MH ₂ SO ₄ was 60 micrometers. Within 30 and 60 minutes after cell filling, the concentration of vanadium ions in the half cell containing MgSO ₄ was 28 mM and 47 mM, respectively. The average permeability of the membrane calculated by equation (2) was 6.2 × 10 ⁻⁶ cm ² / min (30 min incubation) and 5.2 × 10 ⁻⁶ cm ² min ⁻¹ (filled cells were incubated at room temperature for 60 minutes). . The ion conductivity of the membrane was measured by standard impedance spectroscopy method and was 0.1 S / sm.

Example 2

A water-swelled Nafion membrane (Nafion 1110, DuPont) having a scale of about 4 × 3 cm was prepared as described in Example 1, placed in 20 ml of 10 mM dodecyltrimethylammonium chloride solution and left at room temperature for 16 hours. The membrane was then washed thoroughly with distilled distilled water twice and placed in the cell to measure the permeability to vanadium. Exactly within a week, the solution from the half-cell containing magnesium sulfate is quantified and transferred to a 10 ml volumetric flask, the necessary reagents are added for the determination of vanadium concentration according to the procedure described above, and the volume is adjusted to 10 ml. The solution was stirred thoroughly, the pH of the product (pH = 6.4) was adjusted and the absorbance measured. The concentration of vanadium ions in the half-cell containing MgSO ₄ was 0.1 mM. The thickness of the membrane after the modification was 65 micrometers. The membrane permeability calculated using Equation (2) was 6.6 × 10 ⁻¹¹ cm ² / min. The ion conductivity of the membrane was 0.003 S / sm.

Example 3

Nafion membrane (Nafion117) was prepared as described in Example 1. The prepared membrane (approximately 3 × 3 cm) was placed in 15 ml of a 15 mM solution of dodecylamine hydrochloride. That is, 10 g DDA (dodecylamine) was mixed with 15 ml distilled water twice and then adjusted to pH 2 by addition of concentrated HCl solution. Vials were placed in an incubator and incubated at 50 ^° C. for one day to dissolve the surfactant. The membranes were placed in glass jars containing the surfactant solution and held for 7 days at a temperature controller of 50 ^° C. Membrane permeability was measured as described in Example 2. Seven days after cell loading, the vanadium concentration in the half-cell containing MgSO ₄ was 0.06 mM. The film thickness was 65 mkm. The membrane permeability calculated using Equation (2) was 3.94 × 10 ⁻¹¹ cm ² / min. The ion conductivity of the membrane was 0.0017 S / sm.

Example 4

The effect of membrane incubation time in the cationic surfactant solution on the permeability to vanadium ions was studied. To this end, 5 samples (approximately 4 × 3 cm) of five Nafion-117 membranes prepared as described in Example 1 were placed in 15 ml of 10 mM solution of undecylpyridinium bromide, respectively, at room temperature for 1 hour, 3 hours, 5 hours, 16 hours and 24 hours were maintained. The membrane was washed with water and the permeability was measured as described in Example 2. The measurement results are summarized in Table 1.

Membrane treatment time	Sampling moment after filling the cell	VO 2+ concentration in half-cell with MgSO 4 , mM	Membrane permeability, cm 2 / min
1 hours	3 hours	12	4.4 × 10 -7
3 hours	3 days	0.3	4.6 × 10 -10
5 hours	7 days	0.6	3.9 × 10 -10
16 hours	7 days	0.6	3.9 × 10 -10
24 hours	7 days	0.3	2.0 × 10 -10

The data indicate that only 3 hours of incubation of the membrane in a 10 mM solution of cationic surfactant reduces approximately 10 times the membrane permeability to vanadium as compared to the original unmodified Nafion membrane.

Example  5

The effect of the degree of membrane modification on the permeability of vanadil ions of the membrane was evaluated. The Nafion-117 membrane sample prepared as described above was modified with a cationic surfactant cetyl pyridinium chloride (CPC), and the concentration of cationic surfactant in the solution was determined by absorbance values at maximum l = 259 nm. It can be measured spectrophotometrically (molar extinction coefficient = e _m 4100 l mol ^-1 cm ^-1 ).

The experiment was performed as follows. Each of three membrane samples (2 × 2 cm in size) weighing about 0.1 g were placed in separate glass bottles containing 5 ml of distilled water twice and different amounts of CPC.

To determine the absolute amount of sulfo-residues (moles) in each sample of the membrane, the water content in the swollen membrane sample was measured by drying the swollen membrane sample until constant weight at 50 ^° C. The water content of the previously prepared Nafion-117 membrane in water in the swollen state was 25%. Given the fact that the gram equivalent of Nafion 117, corresponding to the dry weight of Nafion per one sulfo group, is 1100, the absolute amount of sulfo groups in the sample of each membrane was as follows:

_{[SO 3 H] membr = 0.1} g × 0.75 / 1100 g / mol = 6.82 × 10 - 5 mol.

Assuming that all sulfo-groups in the membrane can bind the ions of the cationic surfactant, 1.36 ml of 10 mM CPC (molar ratio of Sample No. 1, [CPC] / [SO ₃ ] = 0.2), 10 ml CPC 3.4 ml (Molar ratio of sample number 2, [CPC] / [SO ₃ ] = 0.5) and 6.82 ml of 10 mM CPC (molar ratio of sample number 3, [CPC] / [SO ₃ ] = 1.0) were added to the samples. The CPC concentration in the solution was determined spectroscopically for each solution within 2 and 5 days. The amount [cS] _bound of the surfactant bound to the membrane was measured by decreasing the CPC concentration in the surrounding medium.

Within 2 days, most of the surfactant appeared to be adsorbed on the membrane (residual CPC concentration in solution did not exceed 2% of the added amount.

Thus, three samples of the modified membrane with the degree of modification (filling) of the membrane D = [cS] _bound / [SO ₃ H] of 0.2, 0.5 and 1 were obtained and the membrane permeability to vanadium ions as described in Example 2 And for measurement of membrane ion conductivity. The results are summarized in Table 2.

Membrane filling degree	Sampling moment after cell loading	VO 2+ concentration in half-cell with MgSO 4 , mM	Membrane permeability cm 2 / min	Membrane ion conductivity
Unmodified membrane	0.5 hour	28	6.2 × 10 -6	0.1
0.2	2 hours	10	5.5 × 10 -7	0.09
0.5	3 days	6	9.2 × 10 -9	0.017
One	7 days	0.1	6.6 × 10 -11	0.0016

The data presented above show that even at a small degree of filling (D = 0.2), the permeability of the membrane to vanadium ions is reduced by almost 10 times. The equimolar binding of surfactant (one surfactant ion per one sulfo group of the membrane) indicates a decrease of approximately 100,000 times permeability.

Example 6

Nafion membranes (Nafion1100, DuPont) were prepared as described in Example 1. Water-swelled membranes having a scale of about 4 × 3 cm were prepared, placed in 15 ml of 15 mM dodecylpyridinium chloride solution and left to hold at room temperature for 16 hours. Membrane permeability was measured as described in Example 2. Within 21 days of cell loading, the vanadium concentration in the half-cell containing MgSO ₄ was 3 mM. The thickness of the swollen modified film was 65 micrometers. The membrane permeability calculated using Equation (2) was 6.6 × 10 ⁻¹⁰ cm ² / min. The ion conductivity of the membrane was 0.0017 S / sm.

Example 7

Nafion membrane (Nafion 1110, DuPont) was prepared as described in Example 1. Prepared membranes having a scale of about 3 × 3 cm were placed in 15 ml of 10 mM cetylpyridinium chloride solution and incubated at about 100 ^° C. for 7 hours. Membrane permeability was measured as described in Example 2. Seven days after cell loading, the vanadium concentration in the half-cell with MgSO ₄ was 0.1 mM. The film thickness was 65 micrometers. The membrane permeability calculated using Equation (2) was 6.6 × 10 ⁻¹¹ cm ² / min. The ion conductivity of the membrane was 0.0016 S / sm.

Example 8

Nafion membrane (Nafion 1110, DuPont) was prepared as described in Example 1. The prepared membrane (approximately 3 × 3 cm) was placed in 15 ml of cetyltrimethylammonium bromide 70 mM solution and incubated at about 50 ^° C. for 48 hours. Membrane permeability was measured as described in Example 2. After 430 hours (approximately 18 days) of cell loading, the vanadium concentration in the half-cell with MgSO ₄ was 0.089 mM. The membrane permeability calculated using Equation (2) was 2.3 × 10 ⁻¹¹ cm ² / min.

Example 9

Nafion membrane (Nafion-117) was prepared as described in Example 1. The prepared membrane (approximately 3 × 4 cm) was placed in 10 ml of Praepagen HY solution. As it described by the manufacturer's instructions, Praepagen HY of the general formula _{R 1 R 2 R 3 R 4} N + X -, where _{R 1 = R 2 = CH 3} , R 3 = (CH 2) 2 OH, R 4 = C ₁₀ is an aqueous solution of -C ₂₀ alkyl, mainly C ₁₂ (approximately 65-70%) and C ₁₄ (about 23-28%) mixture, approximately 40% (wt) of the X = Cl the cationic surfactant mixtures of the. To 10 ml of distilled water distilled twice to prepare a solution, 75 mkl of Praepagen HY about 40% solution was added.

The membrane was placed in the solution prepared above and kept at room temperature for 20 hours. Membrane permeability was measured as described in Example 2. Seven days after cell loading, the vanadium concentration in the half-cell with MgSO ₄ was 0.5 mM. The film thickness was 65 mkm. The membrane permeability calculated using Equation (2) was 3.3 × 10 ⁻¹⁰ cm ² / min. The ion conductivity of the membrane was 0.0017 S / sm.

Example 10

The binding stability of the cationic surfactant to the membrane was studied. For this purpose, the membrane obtained according to Example 6 was incubated for two weeks in 50 ml of twice distilled water. The amount of desorbed surfactant (dodecylpyridinium chloride, DDPC) was determined spectroscopically (e _M = 4100 l mol ^{- 1} cm ^-1 ). The DDPC concentration in the solution was 1.5 × 10 ⁻⁵ M, which corresponds to a degree of desorption of less than 1%. The membrane permeability calculated using Equation (2) did not change as compared to the initial modified membrane of Example 6 and was 6.6 × 10 ⁻¹⁰ cm ² / min.

Example 11

The effect of high temperatures on the binding stability of cationic surfactants to membranes was studied. For this purpose, the membrane obtained according to Example 6 was boiled in 100 ml of distilled water for 1 hour. The DDPC concentration in the solution could not be determined by spectroscopy, indicating that the degree of desorption was less than 1%. The membrane permeability calculated using Equation (2) did not change, and was 6.6 × 10 ⁻¹⁰ cm ² / min.

Example 12

The effect of preparation in sulfuric acid on cationic surfactant / membrane binding was studied. For this purpose the membrane prepared according to Example 6 was boiled continuously for 1 hour in 40 ml of 0.5 MH ₂ SO _{4 and} 40 ml of distilled water distilled twice for 1 hour. The membrane permeability calculated using Equation (2) increased 1.6 × 10 ⁻⁹ cm ² / min, or about 2.4 times, and remained below about 1,000 times compared to the permeability of the original unmodified membrane.

Example 13

Nafion membrane (Nafion 1110, DuPont) was prepared as described in Example 1. The prepared membrane (about 3 x 3 cm) was placed in 15 ml of 10 mM cetylpyridinium chloride solution and kept at room temperature for 2 hours. The membrane was washed thoroughly with water and annealed at 150 ^° C. for 24 hours. Stop the film After overnight incubation in 50 ml of distilled water twice, its permeability was measured as described in Example 2. The vanadium concentration in the half-cell with MgSO ₄ after 7 days of cell loading was 0.1 mM. The film thickness was 65 mkm. The membrane permeability calculated using Equation (2) was 6.6 × 10 ⁻¹¹ cm ² / min.

Example 14

Nafion membranes (Nafion1100, DuPont) were prepared as described in Example 1. A water-swelled membrane prepared (0.23 g) was placed in 20 ml of 0.005 M of didecyldimethylammonium bromide ([cS] / [SO ₃ H] _membr = 0.7) and incubated for 36 hours at room temperature. Membrane permeability was measured as described in Example 2. After 11 days of cell loading, the vanadium concentration in the half-cell with MgSO ₄ was 0.9 mM. The film thickness was 65 mkm. The membrane permeability calculated using Equation (2) was 4.0 × 10 ⁻¹⁰ cm ² / min. The ion conductivity of the membrane was 0.0017 S / sm.

Example 15

Nafion membrane (Nafion-1100) was prepared as described in Example 1. A water-swelled, prepared membrane having a weight of 0.29 g was placed in 20 ml of 0.005 M of didecyldimethylammonium bromide solution ([cS] / [SO ₃ H] _membr = 0.55) and incubated at room temperature for 24 hours. Membrane permeability was measured as described in Example 2. Four days after cell loading, the vanadium concentration in the half-cell with MgSO ₄ was 0.03 mM. The film thickness was 65 mkm. The membrane permeability calculated using Equation (2) was 3.5 × 10 ⁻¹¹ cm ² / min.

Example 16

Nafion membrane (Nafion-117) was prepared as described in Example 1. A membrane prepared with water-swell (0.22 g) was placed in 30 ml of 0.01 M of didecyldimethylammonium bromide solution ([cS] / [SO ₃ H] _membr = 2) and incubated at room temperature for 24 hours. Membrane permeability was measured as described in Example 2. After 11 days (261 hours) of cell loading, the vanadium concentration in the half-cell with MgSO ₄ was 0.06 mM. The film thickness was 65 mkm. The membrane permeability calculated using Equation (2) was 2.3 × 10 ⁻¹¹ cm ² / min.

Example 17

Nafion membrane (Nafion 1110) was prepared as described in Example 1. Water-swelled membranes (0.22 g) were placed in 30 ml of 0.005 M of didecyldimethylammonium bromide solution ([cS] / [SO ₃ H] _membr = 1.02) and incubated at 50 ^° C. for 24 hours. . Membrane permeability was measured as described in Example 2. After 11 days of cell loading, the vanadium concentration in the half-cell with MgSO ₄ was 0.13 mM. The film thickness was 65 mkm. The membrane permeability calculated using Equation (2) was 5.5 × 10 ⁻¹¹ cm ² / min. The ion conductivity of the membrane was 0.001 S / sm.

Example 18

To prepare 30 ml of a 0.01 M solution of decylamine in 0.01 M acetic acid, a surfactant sample was placed in a 0.01 M solution of acetic acid and left to stay overnight at 50 ^° C. to dissolve the surfactant. A water-swelled, prepared membrane of Nafion-117 (0.17 g) was placed in 30 ml of 0.01 M solution of decylamine in 0.01 M acetic acid and maintained at 50 ^° C. for 1 week. Membrane permeability was measured as described in Example 2. The membrane permeability calculated using Equation (2) was 1.2 × 10 ⁻¹⁰ cm ² / min.

Example 19

Nafion membranes (Nafion1100, DuPont) were prepared as described in Example 1. A membrane prepared with water-swell (0.19 g) was placed in 20 ml of 0.005 M dioctadecyldimethylammonium bromide solution ([cS] / [SO ₃ H] _membr = 0.76) and incubated at 50 ^° C. for 36 hours. Membrane permeability was measured as described in Example 2. After 22 days of cell loading, the vanadium concentration in the half-cell with MgSO ₄ was 15.5 mM. The film thickness was 65 mkm. The membrane permeability calculated using Equation (2) was 7.2 × 10 ⁻⁸ cm ² / min.

Claims (21)

1. Incorporating the cationic surfactant into the membrane surface and at least a portion of the membrane by incubating the membrane in an aqueous solution or saline solution containing the cationic surfactant or a mixture of the cationic surfactant to improve the membrane's permeability to vanadium ions. How to reduce.
2. The method of claim 1, wherein the membrane is a cation exchange membrane.
3. The method of claim 1, wherein the membrane is a polymer membrane having sulfo groups.
4. The method of claim 1, wherein after introducing the cationic surfactant into the membrane, the permeability of vanadil VO ²⁺ ions is reduced by at least five times as compared to the original unmodified membrane.
5. The method of claim 1, wherein the cationic surfactant has a hydrophobic moiety and the membrane comprises a hydrophobic fragment.
6. The method of claim 1, further comprising the step of subsequently heating the membrane in hydrogen peroxide solution, in sulfuric acid solution, and in distilled water before, after, or before introduction of the cationic surfactant.
7. The method of claim 1, wherein the membrane comprises a polymer having sulfo groups and at least one other polymer.
8. The method of claim 1, wherein the cationic surfactant comprises a compound represented by the following Chemical Formula 1 or 2 or a mixture thereof:

   [Formula 1]

   

   [Formula 2]

   

   In Chemical Formulas 1 and 2,

   R ₁ is hydrogen, methyl or ethyl,

   R ₂ is hydrogen, methyl, ethyl, phenyl, phenylmethyl, hydroxymethyl or hydroxyethyl,

   R ₃ is hydrogen, C ₁ to C ₂₀ alkyl, C ₆ to C ₂₀ aryl, C ₇ to C ₂₀ arylalkyl, C ₁ to C ₂₀ hydroxyalkyl, (CH ₂ CH ₂ O) _n R, Or (CH ₂ ) _p COO ⁻ , where n is an integer from 4 to 100, R is hydrogen or alkyl of C ₁ to C ₂₀ , p is an integer from 1 to 12,

   R ₄ is C ₈ to C ₂₀ alkyl, C ₈ to C ₂₀ hydroxyalkyl, -COOR ',-R "COOR"' or -R "OCOR"', where R' and R "'are C ₈ To C ₂₀ alkyl, R ″ is C ₁ to C ₃ alkylene;

   R ₅ is C ₈ to C ₂₀ alkyl, -COOR ',-R "COOR"' or -R "OCOR"', where R' and R "'are alkyl of C ₈ to C ₂₀ and R" is C ₁ to C ₃ alkylene;

   X is an anionic group.
9. The method of claim 1, wherein the cationic surfactant comprises a surfactant having a double tail, an amphoteric betaine or a surfactant having a hydroxyl group in the side chain.
10. The method of claim 1, wherein the incubation is 100 ^o C to 10 ^o carried out at a temperature of C.
11. The method of claim 1, wherein the concentration of cationic surfactant in the aqueous solution or saline solution is 10 ⁻⁵ M to 1 М.
12. The method of claim 1, wherein the aqueous solution or saline solution further comprises at least one of an inorganic salt, an organic salt, an alkali metal ion, an inorganic acid and an organic acid.
13. A vanadium redox battery comprising an anode, a cathode and a separator provided between the anode and the cathode, wherein the separator is a membrane prepared by the method according to any one of claims 1 to 12.
14. Vanadium redox, including an anode, a cathode, and a separator provided between the anode and the cathode, wherein the separator is a cationic surfactant or a mixture of the cationic surfactants provided on at least part of the surface of the membrane and inside the membrane. battery.
15. 15. The vanadium redox battery of claim 14, wherein the ratio of the number of cationic groups of the cationic surfactant bound to the membrane per sulfo group in the membrane is 0.01 to 2.
16. The vanadium redox battery of claim 14, wherein the membrane is a cation exchange membrane.
17. The vanadium redox battery of claim 14, wherein the membrane is a polymer membrane having sulfo groups.
18. The vanadium redox battery of claim 14, wherein the cationic surfactant has a hydrophobic moiety and the membrane comprises a hydrophobic fragment.
19. The vanadium redox battery of claim 14, wherein the membrane comprises a polymer having sulfo groups and at least one other polymer.
20. The vanadium redox battery of claim 14, wherein the cationic surfactant comprises a compound represented by the following Formula 1 or 2 or a mixture thereof:

    [Formula 1]

    

    [Formula 2]

    

    In Chemical Formulas 1 and 2,

    R ₁ is hydrogen, methyl or ethyl,

    R ₂ is hydrogen, methyl, ethyl, phenyl, phenylmethyl, hydroxymethyl or hydroxyethyl,

    R ₃ is hydrogen, C ₁ to C ₂₀ alkyl, C ₆ to C ₂₀ aryl, C ₇ to C ₂₀ arylalkyl, C ₁ to C ₂₀ hydroxyalkyl, (CH ₂ CH ₂ O) _n R, Or (CH ₂ ) _p COO ⁻ , where n is an integer from 4 to 100, R is hydrogen or alkyl of C ₁ to C ₂₀ , p is an integer from 1 to 12,

    R ₄ is C ₈ to C ₂₀ alkyl, C ₈ to C ₂₀ hydroxyalkyl, -COOR ',-R "COOR"' or -R "OCOR"', where R' and R "'are C ₈ To C ₂₀ is alkyl and R ″ is C ₁ to C ₃ alkylene;

    R ₅ is C ₈ to C ₂₀ alkyl, -COOR ',-R "COOR"' or -R "OCOR"', where R' and R "'are alkyl of C ₈ to C ₂₀ and R" is C ₁ to C ₃ alkylene;

    X is an anionic group.
21. The vanadium redox battery of claim 14, wherein the cationic surfactant comprises a surfactant having a double tail, an amphoteric betaine, or a surfactant having a hydroxyl group in a side chain.