KR101595829B1 - Seperator membrane made of ion-conducting polymer comprising partially branched multiblock copolymer and redox flow batteries comprising the same - Google Patents

Abstract

The present invention relates to a separation membrane fabricated from an ion conductive polymer containing a partial branch block copolymer, and a redox flow battery having the separation membrane.
The separation membrane prepared from the ion conductive polymer containing the partial branched block copolymer according to the present invention can provide excellent ion conductivity, mechanical strength and chemical stability. Further, the redox flow battery having the separation membrane according to the present invention can exhibit excellent cell performance even when it is repeatedly charged / discharged dozens of times, and can maintain a high discharge charge retention ratio.

Description

TECHNICAL FIELD The present invention relates to a separator prepared from an ion conductive polymer including a branched branch block copolymer and a redox flow battery having the same.

The present invention relates to a separation membrane fabricated from an ion conductive polymer containing a partial branch block copolymer, and a redox flow battery having the separation membrane.

Efforts are being made to save fossil fuels or to apply renewable energy to more fields by improving the use efficiency to solve problems of depletion of fossil fuels and environmental pollution. Renewable energy sources such as solar and wind power have been used more efficiently than before, but these energy sources are intermittent and unpredictable. Due to these characteristics, dependence on these energy sources is limited, and the ratio of renewable energy sources among the primary power sources is very low.

BACKGROUND ART Rechargeable batteries provide a simple and efficient method of storing electric power, so that they have been miniaturized to increase their mobility, and efforts to utilize them as an intermittent auxiliary power source or a power source for a small household appliance such as a laptop, a tablet PC, and a mobile phone have been continued.

Redox Flow Battery (RFB) is a secondary battery that can store and store energy for a long time by repeated charging and discharging by electrochemical reversible reaction of electrolyte. The stack and electrolyte tanks, which depend on the capacity and output characteristics of the battery, are independent of each other, so that the battery design is free and the installation space is limited.

The redox flow battery has a load leveling function that can cope with the sudden increase in power demand installed in a power plant, a power system, or a building, and has a function to compensate or suppress the power failure or the instantaneous undervoltage. It is an energy storage technology and suitable for large-scale energy storage.

These redox flow cells consist of two separate electrolytes. One stores the electroactive material in the negative electrode reaction and the other stores the positive electrode reaction. In an actual redox flow cell, the electrolyte reaction is different between the positive electrode and the negative electrode, and there is a flow of the electrolytic solution, so a pressure difference occurs between the positive electrode and the negative electrode. The reaction of the positive and negative electrode electrolytes in the entire vanadium-based redox flow battery, which is a typical redox flow battery, is as follows.

Therefore, a separation membrane with improved physical and chemical durability is required to overcome the pressure difference between both electrodes and to exhibit excellent cell performance even when charging and discharging are repeated. However, there is a disadvantage that resistance increases due to an increase in the thickness of the separating film in order to improve the physical durability.

Accordingly, the present inventors have made intensive studies to find a separation membrane for a redox flow cell having improved ionic conductivity and physical and chemical durability. As a result, it has been found that an ion exchange membrane made of an ion conductive polymer including a hydrophilic block and a hydrophobic block capable of partially bonding to each other has high mechanical Strength and excellent ionic conductivity, and a redox flow battery comprising the same as a separation membrane was fabricated. It was confirmed that the battery had excellent medium / long-term durability while exhibiting excellent cell performance, and completed the present invention.

An object of the present invention is to provide a separation membrane fabricated from an ion conductive polymer containing a partial branched block copolymer and a redox flow battery having the separation membrane.

In a first aspect of the present invention, there is provided a separation membrane for a redox flow cell produced from an ion conductive polymer comprising a partially branched multiblock copolymer, wherein the partial branched block copolymer comprises a hydrophilic first polymer A first block; A second block derived from a hydrophobic second polymer having two or more reactors respectively participating in a polymerization reaction at both ends so as to form a branching point forming a side chain on the main chain; And a third block made of a hydrophobic third polymer, wherein the first block is represented by the following formula (1), the hydrophobic second block is represented by the following formula (2), and the third block is represented by the following formula Thereby providing a separation film characterized by being displayed.

[Chemical Formula 1]

(2)

(3)

In Formula 1,

A is a single bond or an electron withdrawing group - (C = O) -, - (P = O) -, - (SO ₂ ) -, -CF ₂ - or - (C (CF ₃ ) ₂ ) -;

B and B 'each independently represent -O-, -S-, -NH- or -NR ₁₃ - as a single bond or electron donor group, wherein R ₁₃ is a C 1 to C 6 alkyl group;

M is a hydrogen atom or an alkali metal;

Ar is an aromatic molecule or aromatic molecule group substituted with at least one sulfonic acid group (-SO ₃ H) or its alkali metal salt;

a and b each represent an integer belonging to 0 to 10,

k is an integer belonging to 1 to 4,

c is an integer belonging to 1 to 10,000,

In Formula 2 or Formula 3,

R ₁ to R ₄ and R ₁ 'to R ₄ ' each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkyl group substituted with a halogen, an allyl group, a cyano group, an aryl group, a sulfonic acid group, , Perfluoroalkyl groups, perfluoroalkylaryl groups optionally containing one or more oxygen, nitrogen or sulfur atoms on the chain, perfluoroaryl groups or -O-perfluoroaryl groups;

D ₁ , D ₂ , D ₁ 'and D ₂ ' are each independently -O-, -S-, -NH- or -NR ₁₄ - as an electron donor group, wherein R ₁₄ is a C 1 to C 6 alkyl group;

_{J 1, J 2, J 1} ' _2, and J' is a bond or an electron withdrawing group one are each independently - (C = O) -, - (P = O) -, - (SO 2) -, -CF 2 - or _{- (C (CF 3) 2} ) -,

E and E 'are each independently -O-, -S-, -NH- or -NR ₁₅ - as an electron donor group, wherein R ₁₅ is a C 1 to C 6 alkyl group;

또는

,Ar and Ar 'each independently represent a group selected from the group consisting of an unsubstituted or substituted with at least one halogen atom (-X), an alkyl group halogen-substituted alkyl group, an allyl group, a cyano group, an aryl group, a sulfonic acid group, a phosphoric acid group, An aryl group substituted with a functional group selected from the group consisting of a perfluoroalkyl group, a perfluoroaryl group and an -O-perfluoroaryl group, optionally containing one or more oxygen, nitrogen or sulfur atom in its chain, , A naphthyl group, an anthracenyl group,

or

,

P and P 'are each independently a single bond, a group selected from -O-, -S-, -NH- or -NR ₁₆ - (R ₁₆ is a C 1 to C 6 alkyl group) as an electron donor group, a - (C = O) -, - (P = O) -, - (SO 2) -, -CF 2 -, - (C (CH 3) 2) - or _{- (C (CF 3) 2} ) - ,

R ₅ to R ₁₂ and R ₅ 'to R ₁₂ ' each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkyl group substituted with a halogen, an allyl group, a cyano group, an aryl group, a sulfonic acid group, , A perfluoroalkyl group, a perfluoroalkylaryl group optionally containing one or more oxygen, nitrogen or sulfur atoms in its chain, a perfluoroaryl group or an -O-perfluoroaryl group,

In the above formulas (1) to (3), the sulfonic acid group, phosphoric acid group and acetic acid group may be in the form of an alkali metal salt;

p and p 'each represent an integer belonging to 1 to 1000,

q and q 'each represent an integer belonging to 0 to 5,

w and w 'are integers belonging to 1 to 10, respectively.

A second aspect of the present invention provides a redox flow battery having the separation membrane according to the present invention.

Hereinafter, the present invention will be described in detail.

The term "redox flow battery" of the present invention means that an electrolyte containing an electroactive species flows through an electrochemical cell, which reversibly converts chemical energy into electricity, A rechargeable fuel cell, which is a type of flow cell, is a reversible fuel cell in which all electro-active components are dissolved in an electrolyte. Gravity feed systems are used, but mainly the additional electrolyte is stored externally, typically in a separate tank, and is pumped through the cells of the reactor. Flow cells can be quickly recharged by replacing the electrolyte solution (in a manner similar to replenishing the fuel tank of an internal combustion engine) while at the same time recovering the spent material for re-energization. In such a redox flow battery, the energy of the cell is determined by the electrolyte volume, for example, the tank size, and the power by the electrode size, for example, the reactor size, so that the energy is completely decoupled from the power similarly to other fuel cells.

Unlike other batteries, such a redox flow battery is an aqueous solution in which an electroactive species is not a solid, and a mechanism for storing energy by an oxidation / reduction reaction of ions in the anode 21 and the cathode 22 Respectively. The positive electrode electrolyte and the negative electrode electrolyte for causing the above-described reaction are stored in separate storage tanks (not shown), respectively, and are introduced into the cell housing 51 through the electrolyte inflow ports 31 and 41 formed in the cell housing 51 And has a circulation system that contacts the anode 21 and the cathode 22 to cause a reaction and then flows out through the respective electrolyte outlets 32 and 42. The battery is discharged by connecting an electric load to an external circuit including an electric load to allow a current to flow, and conversely, an external power source is connected to the battery to allow the electric current to flow. In general, a cathodic electrolyte is charged when the redox couple is oxidized to the higher of the two states, and is discharged when the redox is reduced to the lower state. In the negative electrode electrolyte solution, the opposite phenomenon appears.

As described above, most redox flow cells are composed of two separate electrolytes. One stores the electroactive material in the negative electrode reaction and the other stores the positive electrode reaction. At this time, the negative electrode is defined as the anode and the positive electrode is defined as the cathode in discharging to prevent confusion. The charge will be reversed. Fresh or used electrolytes can be circulated and stored in a single storage tank. Or the concentration of the electroactive material can be individually adjusted. An ion exchange membrane is used as a separator to prevent mixing of electroactive species which may cause chemical breakdown.

The term "separation membrane" of the present invention refers to an ion exchange membrane introduced to prevent mixing of electroactive species in the redox flow cell, and a common counter ion carrier ) Passes through the separation film. For example, in a bromine-polysulfide system in which Na ₂ S ₂ is converted to Na ₂ S ₄ at the anode and Br ₂ is converted to ₂ Br at the cathode, excess Na ⁺ ions at the anode to maintain electro- Lt; / RTI > Similarly, in a vanadium system where V ^{2 +} is oxidized to V ^{3 +} at the anode and V ^{5 +} is reduced to V ^{4 +} at the cathode, the hydronium ion (H ₃ O ⁺ ) is injected through the proton- And moves to the cathode.

In an actual redox flow cell, the electrolyte reaction is different between the positive electrode and the negative electrode, and there is a flow of the electrolytic solution, so a pressure difference occurs between the positive electrode and the negative electrode. Therefore, it is preferable that the separation membrane has excellent physical strength so as not to be broken by such a pressure difference.

The separation membrane of the present invention is formed of an ion conductive polymer comprising a partial branched block copolymer, wherein the partial branched polymer is a hydrophilic first polymer; A second block derived from a hydrophobic second polymer having two or more reactors respectively participating in a polymerization reaction at both ends so as to form a branching point forming a side chain on the main chain; And a third block, optionally made of a hydrophobic third polymer.

For example, in the case of using a hydrophilic polymer having a hydrophilic polymer having one reactor participating in polymerization reaction at both ends and a hydrophobic polymer having one reactor participating in a polymerization reaction at both ends, Unlike linear block copolymers, one embodiment of the present invention comprises adding a hydrophobic polymer having two or more reactive groups at both ends, each of which participates in a polymerization reaction, so as to form a branching point that forms side branches on the main chain To form a partial branched block copolymer, which is used as a material for a separation membrane.

Since the separation membrane according to the present invention is made of a polymer including a partial branched block copolymer, it can have both advantages of a block copolymer and a branched polymer. In other words, it is possible to form a densely & locally sulfonated structure, which is superior in the fine phase separation characteristic in which phase separation between a hydrophilic domain and a hydrophobic domain is effectively performed, Amorphousity is increased as compared with the coalescence, and the solubility in the organic solvent is better. Therefore, considering that the membrane production process is based on a solution process, there is an advantage that it can be manufactured more easily by using the polymer.

The partial branched block copolymer forming the separation membrane according to the present invention preferably has a hydrophilic block composed of a hard carbon-carbon bond and a hydrophobic second block and / or a hydrophobic third block is a flexible ether (Arylene ether) containing an ether bond (-O-). The term " poly (arylene ether) " When the first hydrophilic block made of a hydrophilic first polymer is composed of a hard carbon-carbon bond, it is excellent in dimensional stability, and a phenyl ring substituted with a sulfonic acid ) Has excellent chemical stability against various radicals since it does not contain an ether bond. By using a block copolymer containing a hydrophilic first block as a part, it is possible to provide a separator for a battery which exhibits high ionic conductivity and at the same time has excellent chemical stability. On the other hand, the hydrophobic second block and / or the hydrophobic third block can impart flexibility to the polymer by including a poly (arylene ether) containing an ether bond as a skeleton.

The polymer forming the separation membrane according to the present invention may be a polymer characterized in that the repeating units of the first to third blocks are arranged in a random, alternating, or sequential manner, Lt; / RTI > When sufficiently limited, the molar ratio of each repeating unit can be varied variously.

According to the present invention, a first hydrophilic block oligomer is represented by the following formula (1), wherein a phenylene repeating unit is a backbone and at least one sulfonic acid group acid group; -SO ₃ H) or an alkali metal salt thereof. The Ar of Formula 1, which is preferably introduced to impart hydrophilicity, may be phenyl, naphthyl, thiophenyl or pyridinyl substituted with one or more sulfonic acid groups or an alkali metal salt thereof, but is not limited thereto.

The halogen element is a substituent that is widely introduced for the reaction such as condensation and substitution because it is excellent in reactivity when it is introduced as a substituent to an organic compound due to high electronegativity due to high effective nuclear charge. Accordingly, in the hydrophobic second polymer having two or more reactors each participating in a polymerization reaction at both ends so as to form branching points forming side branches on the main chain, which is represented by the general formula (2) . That is, X and X 'are preferably halogen atoms. The halogen element may be F (fluorine), Cl (chlorine), Br (bromine), I (iodine) or the like. More preferably, X and X 'in Formula 2 may each independently be a chlorine atom.

On the other hand, excessive branching can promote the gelation of the polymer. The gelation is caused by the cross-linking system, and the gel does not flow in a rectified state, which is different from the liquid state, so that it is difficult to manufacture the membrane as the separation membrane of the present invention. Accordingly, in order to prevent gelation due to excessive branching, the ion conductive polymer according to the present invention may further comprise a hydrophobic third block polymer represented by the above formula (3).

The separation membrane of the present invention can be produced by using any known molding method as the partial branched block copolymer which is the ion conductive polymer.

For example, the polymer is dissolved in a solvent such as N-methylpyrrolidone (NMP), dimethylformamide, dimethylsulfoxide or dimethylacetamide, and the solution is poured into a plate such as a glass plate The polymer can be dried to obtain a film of several to several hundreds of μm, preferably 10 to 120 μm, more preferably 50 to 100 μm thick, and then desorbed from the plate. The above-mentioned solvent is only illustrative, and the scope of the present invention is not limited thereto. Conventional organic solvents may be used as long as they dissolve the polymer and can be evaporated under the drying condition. Specifically, the same organic solvent as that used in the preparation of the polymer may be used.

Or by decreasing the rate of dimensional change, the ion conductive polymer may be impregnated into a nanofiber support to prepare a reinforced composite membrane. The "nano web support" is composed of a collection of nanofibers connected three-dimensionally irregularly and discontinuously and thus comprises a number of uniformly distributed pores. And thus includes a plurality of uniformly distributed pores.

Preferably, the nanoweb support can be selected from materials that do not have electrochemical activity. Non-limiting examples of materials constituting the nano web support include polyimide, polymethylpentene, polyester, polyacrylonitrile, polyvinylamide, polyethylene, polypropylene, polyvinyl fluoride, polyvinyl difluoride, nylon, Polybenzoxazole, polyethylene terephthalate, polytetrafluoroethylene, polyarylene ether sulfone, polyether ether ketone or a combination thereof. That is, the nano web supporter itself has no electrochemical activity, but exhibits the characteristics of the ion exchange membrane through the impregnated ion conductive polymer. As a result, the heat resistance, the chemical resistance, and the mechanical properties can be improved as compared with the separation membrane produced only by the ion conductive polymer.

The ion-conductive polymer may be filled in the nano-web supporter using a supporting or impregnating process, but the present invention is not limited thereto. Various methods known in the art such as a laminating process, a spray process, a screen printing process, and a doctor blade process may be used .

According to a specific embodiment of the present invention, the prepared polymer is dissolved in NMP and poured into a silicon mold having a predetermined size and dried at 60 to 100 ° C, preferably 70 to 90 ° C for 12 to 36 hours, preferably 18 to 30 hours So that a film can be obtained. The polymer was impregnated into a polyimide nano web support to prepare a reinforced composite membrane. The obtained membrane may be washed with a sulfuric acid solution and distilled water in order to convert the membrane prepared in the form of sodium salt into a proton-type polymer membrane.

It is preferable that the isolation film has a thickness of 10 mu m to 1000 mu m. If the thickness of the separator is less than 10 탆, the mechanical strength and shape stability may be deteriorated. If the thickness is more than 1000 탆, the resistance loss may increase.

The branched branched block copolymer for forming the separation membrane of the present invention may have a skeleton containing a repeating unit represented by the following general formula (4)

[Chemical Formula 4]

Wherein each letter in Formula (4) is as defined in Formulas (1) to (3)

l and m each independently represents an integer of 1 or more, and n represents an integer of 0 or more,

Wherein t and t 'correspond to t and t' representing the number of substituents X and X 'in the monomer represented by the formula (2), respectively, and are the number of branch bonds with neighboring blocks.

는 2개의 이웃한 블록과의 가지결합 가능한 분기점을 나타내기 위하여 사용한 표기형식이다. 즉, 상기 화학식 4로 표기되는 고분자는 양 말단에 위치한 분기점으로부터 2개의 이웃한 블록과 가지결합을 형성할 수 있음을 나타낸다. 예컨대, 하나의 결합으로는 고분자의 주쇄골격을 형성하면서 다른 하나 결합자리를 통해 다른 친수성 또는 소수성 블록과 가지결합을 형성할 수 있다.
In the present invention

Is a notation format used to indicate branch points that can be combined with two neighboring blocks. That is, the polymer represented by the formula (4) can form branch bonds with two neighboring blocks from the branching points located at both ends. For example, one bond may form a main chain skeleton of a polymer while forming a branch bond with another hydrophilic or hydrophobic block through another bond site.

The partial branched block copolymer for forming the separation membrane of the present invention, that is, the partial branched block copolymer represented by the general formula (4) has the total number (l) of the units forming all the hydrophilic first blocks: the number of the hydrophobic second blocks and the hydrophobic And the sum (m + n) of the number of the third blocks = 0.1: 1 to 100: 1. For example, when the molar ratio is less than 0.1: 1, ionic conductivity is almost zero. When the molar ratio is 100: 1 or more, the polymer is dissolved in water and can not act as an actual separator. More preferably 0.1: 1 to 50: 1, and even more preferably 0.1: 1 to 30: 1.

The ratio of the number of hydrophobic second blocks to the number of hydrophobic third blocks is preferably such that the proportion of the branch type hydrophobic second blocks does not exceed 50% in order to prevent gelation due to excessive branching. Further, for effective phase separation and molecular weight increase, it is preferably 2% or more. If this is represented by the relationship of n and m, 0.5? N / (m + n) < 1 can be preferably satisfied.

Preferably, the ion conductive polymer comprising the branched branch block copolymer forming the separation membrane according to the present invention has Mn (number-average molecular weight) of 10,000 to 1,000,000 or Mw (weight-average molecular weight) of 10,000 to 10,000,000. weight-average molecular weight). When the molecular weight is low, for example, when it is 10,000 or less, film formation is difficult, the moisture content is increased, and it is easily decomposed by the attack of radical, so that conductivity and durability may be decreased. On the other hand, in the case where the molecular weight is high, for example, 1,000,000 or more, the rapidly increasing viscosity may make the preparation of the polymer solution and molding into a film difficult, making the film production process impossible.

및

로서, P는 -(SO₂)-, R₅ 내지 R₁₂, 및 R₅' 내지 R₁₂'은 모두 수소원자, P는 -(SO₂)-, R₅ 내지 R₁₂, 및 R₅' 내지 R₁₂'은 모두 수소원자; w=2이며, q=1인 격리막일 수 있다.
In one embodiment of the partial branched block copolymer represented by the general formula (4) for forming the separation membrane of the present invention, A is - (C = O) -; Ar is phenyl substituted with one sulfonic acid group or its sodium salt; a and b are each 0, and R ₁ , R ₁ 'and R ₂ to R ₅ are both a hydrogen atom; D ₁ , D ₂ , D ₁ 'and D ₂ ' are both -O-; J ₁ , J ₂ , J ₁ 'and J ₂ ' are both - (C═O) -; E and E 'are -O-; Ar ' and Ar ''

And

Wherein P is - (SO ₂ ) -, R ₅ to R ₁₂ and R ₅ 'to R ₁₂ ' are all hydrogen atoms, P is - (SO ₂ ) -, R ₅ to R ₁₂ and R ₅ ' R ₁₂ 'are all hydrogen atoms; w = 2, and q = 1.

The redox flow battery according to the present invention is a redox flow battery having a positive electrode, a positive electrode electrolyte, a separator according to the present invention, a negative electrode electrolyte and a negative electrode.

The positive electrode and the negative electrode may be electrode materials conventionally used in the art. For example, carbon felt, carbon nonwoven fabric, graphite felt, graphite plate and the like can be used, but the present invention is not limited thereto.

1, the battery includes a cell housing 51 having a predetermined size, an ion exchange membrane 11 disposed across the center of the cell housing, an ion exchange membrane 11 disposed inside the cell housing, (21) and a cathode (22) electrode located on both sides of the left and right sides separated by the exchange membrane, and an upper electrode and a lower electrode formed on the upper and lower ends of the cell housing on the side where the anode electrode is located, And a cathode electrolyte inlet (31) and a cathode electrolyte outlet (32), which are formed at the upper and lower ends of the cell housing on the side of the cathode electrode, for performing the inflow and outflow of the electrolyte used for the cathode electrode 41 and a cathode electrolyte outlet 42.

Preferably, the redox flow cell according to the present invention comprises a V (IV) / V (V) redox couple as a cathode electrolyte and a pre-vanadium-based redox couple using a V (II) / V Redox battery; A vanadium-based redox battery using a halogen redox couple as a cathode electrolyte and a V (II) / V (III) redox couple as a cathode electrolyte; A polysulfide bromine redox cell using a halogen redox couple as a positive electrode electrolyte and a sulfide redox couple as a negative electrode electrolyte; Or a zinc-bromine (Zn-Br) redox battery using a zinc redox couple as a positive electrode electrolyte and a zinc redox couple as a negative electrode electrolyte.

The separation membrane prepared from the ion conductive polymer containing the partial branched block copolymer according to the present invention can provide excellent ion conductivity, mechanical strength and chemical stability. In addition, the redox flow battery having such a structure can exhibit excellent cell performance even when it is repeatedly charged / discharged dozens of times and can maintain a high discharge charge retention ratio.

1 is a schematic view showing a configuration of a general redox flow battery.
FIG. 2 is a ¹ H NMR spectrum of a partially crosslinked block copolymer P1 according to an embodiment of the present invention. FIG.
Figure 3 is a ¹ H NMR spectrum of a partially bonded block copolymer P2 according to one embodiment of the present invention.
FIG. 4 is a ¹ H NMR spectrum of a partially crosslinked block copolymer P3 according to an embodiment of the present invention. FIG.
5 is a graph illustrating the performance of a single cell having a P1 polymer ion exchange membrane according to an embodiment of the present invention. And the discharge charge amount according to the charge / discharge repetition times.
FIG. 6 is a diagram illustrating energy efficiency, Coulomb efficiency, and voltage efficiency change according to the number of charge / discharge repetitions of a single cell having a P1 polymer ion exchange membrane according to an embodiment of the present invention.
FIG. 7 is a graph showing a discharge charge retention ratio according to the number of times of charge / discharge repetition of a single cell having a P1 polymer ion-exchange membrane according to an embodiment of the present invention.
8 is a graph showing the performance and efficiency of a single cell having a P1 polymer ion exchange membrane and a reinforced composite membrane containing P1 (P1 + nanoweb) according to an embodiment of the present invention as a separation membrane. The performance and the discharge charge retention ratio were measured while repeating charging / discharging and compared with the performance of the cell having Nafion 212.
9 is a view showing an image of a reinforced composite membrane obtained by repeatedly charging / discharging a single cell having a reinforced composite membrane containing a P1 polymer according to an embodiment of the present invention as a separation membrane more than 85 times.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited to these examples.

Manufacturing example  1: hydrophilic monomer ( M1 ) Synthesis of

100 g (398 mmol) of 2,5-dichlorobenzophenone (2,5-DCBP) was added to 150 ml of concentrated sulfuric acid and the solution was completely dissolved. fuming sulfuric acid (150 ml) was dropped dropwise to the temperature of 80 ° C and stirred for 16 hours. After lowering the temperature to room temperature, it was poured into a large amount (about 2 L) of ice-cold water and 200 g of NaCl was added. The resulting white powder was filtered and dissolved in about 2 L of deionized water. 10% NaOH was added until the pH reached 6 to 7, and 150 g of NaCl was added to precipitate again. The precipitate was filtered and completely dried, and then the solution was added to about 1 L of dimethylsulfoxide (DMSO) and stirred. The solution was filtered and the filtered solution was evaporated to remove the solvent, and the crude product was recrystallized twice with deionized water and dried in vacuo for 24 hours. 84 g of sodium 3 '- (2,5-dichlorobenzophenone) sulfonate (2,5-SDCBP) was obtained through the above procedure.

Manufacturing example  2: Hydrophobic block intermediate ( O1 - OH ) Synthesis of

28.9 g (100.5 mmol) of bis (4-chlorophenyl) sulfone (DCPS), 20 g (107.4 mmol) of 4,4'-dihydroxyphenyl and 17.8 g (128.9 mmol) of K ₂ CO ₃ were dissolved in 250 ml of DMAc (dimethylacetamide) and 120 ml of toluene. After stirring at 145 占 폚 for 3 hours, the temperature was raised to 165 占 폚, the toluene was evaporated completely, and further stirred for 24 hours while maintaining the temperature. The temperature was lowered to room temperature, filtered, and the filtrate was poured into methanol to obtain a precipitate. The precipitate obtained was washed once with hot methanol, filtered and dried in a vacuum oven. Through the above procedure, 42.8 g of the compound O1-OH (Mn = 5.6K) was obtained.

Manufacturing example  3: Combination of branches  Possible hydrophobic block polymers ( O1 ) Synthesis of

10 g (1.79 mmol) of O1-OH synthesized in Preparation Example 2 was added to 2,5-dichloro-4'-fluorobenzophenone (2,5-DCFBP) 1.21 g (4.48 mmol) and K ₂ CO ₃ (0.30 g, 2.15 mmol) were dissolved in 100 ml of DMAc (dimethylacetamide) and 50 ml of toluene. After stirring at 145 占 폚 for 3 hours, the temperature was raised to 165 占 폚, the toluene was evaporated completely, and further stirred for 24 hours while maintaining the temperature. The reaction solution was filtered at room temperature, and the filtrate was poured into methanol to obtain a precipitate. The precipitate obtained was washed once with hot methanol, filtered and dried in a vacuum oven. Through the above procedure, 10.3 g of compound O1 was obtained.

Manufacturing example  4: Hydrophobic block polymer ( O2 ) Synthesis of

The O1-OH 10 g (1.79 mmol ) synthesized in Preparative Example 2 4-Chloro-4'-fluoro Robben non jope (4-chloro-4'-fluorobenzophenone ; CFBP) 1.05 g (4.48 mmol) and K ₂ Was dissolved in 100 ml of DMAc (dimethylacetamide) and 50 ml of toluene together with 0.30 g (2.15 mmol) of CO ₃ . After stirring at 145 占 폚 for 3 hours, the temperature was raised to 165 占 폚, the toluene was evaporated completely, and further stirred for 24 hours while maintaining the temperature. The reaction solution was filtered at room temperature, and the filtrate was poured into methanol to obtain a precipitate. The precipitate obtained was washed once with hot methanol, filtered and dried in a vacuum oven. Through the above procedure, 10.4 g of compound O2 was obtained.

Manufacturing example  5: Partially Branch  Block copolymer ( P1 - P3 ) And preparation of polymer membrane using the same

< P1 Synthesis of &gt;

0.17 g of NiBr ₂ , 1.5 g of triphenylphosphine and 3.2 g of zinc were dissolved in 10 ml of DMAc, and the mixture was stirred at 80 ° C for 30 minutes to obtain a solution prepared in Preparation Examples 1, 3 and 4, respectively A solution obtained by dissolving 4 g of a hydrophilic monomer (2,5-SDCBP; M1), 0.13 g of an oligomerizable hydrophobic block polymer (O1) and 1.2 g of a hydrophobic block polymer (O2) in 20 ml of DMAc was added. The mixture was further stirred for about 8 hours while maintaining the temperature, and the temperature was lowered to room temperature. The mixture was poured into an ethanol / hydrochloric acid mixed solution (9: 1, v / v) to remove zinc and washed with hot ethanol and hot distilled water. The synthesized block copolymer was dried at 80 DEG C under vacuum to obtain 3.2 g of a polymer (P1). The polymer was prepared in the form of a sodium salt. Mn = 77.8 kg / mol, Mw = 168.4 kg / mol.

The synthesized P1 polymer was identified by ¹ H NMR and the results are shown in Fig.

< P2 Synthesis of &gt;

0.17 g of NiBr ₂ , 1.5 g of triphenylphosphine and 3.2 g of zinc were dissolved in 10 ml of DMAc, and the mixture was stirred at 80 ° C for 30 minutes to prepare a solution prepared in each of Examples 1, 3 and 4 A solution of 4 g of a hydrophilic monomer (2,5-SDCBP; M1), 0.39 g of an oligomerizable hydrophobic block polymer (O1) and 0.94 g of a hydrophobic block polymer (O2) in 20 ml of DMAc was added. The mixture was further stirred for about 8 hours while maintaining the temperature, and the temperature was lowered to room temperature. The mixture was poured into an ethanol / hydrochloric acid mixed solution (9: 1, v / v) to remove zinc and washed with hot ethanol and hot distilled water. The synthesized block copolymer was dried in a vacuum of 80 캜 to obtain 3.4 g of a polymer (P2). The polymer was prepared in the form of a sodium salt. Mn = 89.6 kg / mol, Mw = 242.8 kg / mol.

The synthesized P2 polymer was identified by ¹ H NMR and the results are shown in FIG.

< P3 Synthesis of &gt;

0.17 g of NiBr ₂ , 1.5 g of triphenylphosphine and 3.2 g of zinc were dissolved in 10 ml of DMAc, and the mixture was stirred at 80 ° C for 30 minutes to prepare a solution prepared in each of Examples 1, 3 and 4 A solution of 4 g of a hydrophilic monomer (2,5-SDCBP; M1), 0.17 g of a bondable hydrophobic block polymer (O1) and 1.6 g of a hydrophobic block polymer (O2) in 20 ml of DMAc was added. The mixture was further stirred for about 8 hours while maintaining the temperature, and the temperature was lowered to room temperature. The mixture was poured into an ethanol / hydrochloric acid mixed solution (9: 1, v / v) to remove zinc and washed with hot ethanol and hot distilled water. The synthesized block copolymer was dried at 80 DEG C under vacuum to obtain 3.2 g of a polymer (P3). The polymer was prepared in the form of a sodium salt. Mn = 74.6 kg / mol, Mw = 172.4 kg / mol.

The synthesized P3 polymer was identified by ¹ H NMR and the results are shown in FIG.

&Lt; Preparation of polymer membrane &

Each of the synthesized polymers P1 to P3 was dissolved in 5 ml of N-methyl-2-pyrrolidone (NMP) in an amount of 0.5 g each, and the polymer was poured into a silicone mold and dried at 80 DEG C for 24 hours to obtain a membrane. The membrane thus prepared was converted into a protonic form of the above formula (P1 to P3) in a 1.5 M sulfuric acid aqueous solution and distilled water for 24 hours, respectively, in the form of a sodium salt.

Experimental Example  1: Partially Branch  Block copolymer ( P1 - P3 Comparison of Characteristics of Polymer Membranes Prepared by

The physical properties of the polymer membranes (P1 to P3) prepared by the method described in Production Example 5 and the Nafion 212 polymer membranes commercialized as Comparative Examples were measured and compared.

First, the proton conductivity was measured at 100% relative humidity at 25 ° C and 80 ° C using an AC impedance analyzer (Solatron 1280, Impedance / gain phase analyzer). Four prove conductivity cells were measured in the in-phase direction in the range of 0.1 to 20 kHz. The temperature was maintained for 30 minutes in the thermo-hygrostat chamber before measurement, and the conductivity was calculated by the following equation.

Where I is the distance between the electrodes, R is the impedance of the film, and S is the surface area over which the protons move.

Next, the degree of dimensional change was measured. The volume of the wet film (V _wet ) was measured after immersing the membrane in distilled water for 24 hours to measure the degree of dimensional change, and the wet film was vacuum dried again at 120 ° C for 24 hours to measure the volume (V _dry ). These measured values were substituted into the following equations to calculate the degree of dimensional change.

Finally, water uptake (WU) was measured. The water absorption rate was calculated by measuring the mass of the wet film (W _wet ) and the mass of the dried film (W _dry ) using the following equation.

The molecular weight was measured by measuring intrinsic viscosity. In order to measure the intrinsic viscosity, the prepared polymer was dissolved in NMP and the viscosity of the solution prepared at a concentration of 0.5 g / dl was measured in a 25 ° C. thermostat using a Ube load viscometer.

The results thus obtained are summarized in Table 1 below.

Example  1: Partially Branch  Block copolymer ( P1 ) &Lt; / RTI &gt; Redox Flow  Battery configuration and performance evaluation

The membrane containing the P1 polymer was cut into a size of 70 mm × 50 mm out of the 55 μm thick proton-type ion exchange membrane containing the P1 to P3 polymer prepared according to the above Preparation Example, (11), and the charge / discharge test and efficiency of the cell were measured. The results are shown in FIGS. 5 to 7.

Specifically, the single cell was made of carbon felt having a thickness of 5 mm, which was treated with an anode and a cathode material by heat and acid, respectively. The electrode frame material was acrylic and the end plate material was Hexion bakelite. V (IV) / V (V) redox couple was used as the anode electrolyte and V (II) / V (III) redox couple was used as the cathode electrolyte.

In order to improve the dimensional stability of the ion exchange membrane, a single cell (P1 + nanoweb) with a reinforced composite membrane prepared by impregnating a niobium support of polyimide (PI) with P1 was fabricated under the same conditions. As a comparative example, a single cell (Nafion 212) in which Nafion, which is widely used as an ion conductor in a conventional redox flow cell, was introduced as an ion exchange membrane was prepared by the same method. The single cell equipped with the ion-exchange membrane (P1) made of the P1 polymer and the reinforced composite membrane (P1 + nano-web) including P1 and the Nafion 212 having the Nafion 212 were subjected to the same method The charge / discharge test and the efficiency were measured to compare the performance. The results are shown in FIG. Table 2 compares the performance of each single cell with numerical values.

The driving test for evaluating the performance of the single cell was performed at room temperature, i.e., at 25 캜. The flow rate of the electrolyte was fixed at 40 ml / min. The charge proceeded to 1.6 V with a current density of 50 mA / cm ² and the discharge proceeded to 1.0 V with the same current density. All single cells were charged / discharged 100 times in order to test the durability.

As shown in FIGS. 5 to 7, a single cell having a P1 ion exchange membrane exhibits excellent cell performance even when it is repeatedly charged / discharged dozens of times, and has a high level of energy efficiency (EE), coulombic efficiency (CE) and voltage efficiency (VE) as well as the discharge charge retention ratio was high, and even when used repeatedly 70 times or more, the retention ratio was 80% or more.

As shown in FIG. 8, when a single cell equipped with a reinforced composite membrane including P1 and a Nafion 212 ion exchange membrane was compared with a cell performance and discharge charge retention ratio, a single cell having a P1 ion exchange membrane or a P1- It showed a similar or high value as compared with the conventional single cell having Nafion 212 ion exchange membrane and exhibited a higher discharge charge retention ratio. In particular, although the performance of all cells tends to decrease with repeated charging / discharging, the performance decrease rate of the cell with P1 or P1 enhanced composite membrane is gentler than 70% Cells with a P1 ion exchange membrane showed higher performance in repeated cells. That is, P1 is an ion conductor excellent in the initial discharging charge retention ratio, which is almost equal to that of a cell equipped with an ion exchange membrane and having a comparable or better middle / long-term discharge charge retention ratio, when compared with a cell equipped with an ion exchange membrane. However, the performance of the cell equipped with the P1-reinforced composite membrane in the cell repeated 70 times was abruptly decreased, and the discharge charge retention rate rapidly decreased at a point exceeding 60 times. This phenomenon is repeatedly used Which may be due to membrane damage. For example, FIG. 9 shows an image of a P1-enhanced composite membrane separated from a cell in which charge / discharge was repeated 85 times or more. From this, it was confirmed that some of the reinforced composite membranes were damaged, and it was possible to deduce that the damage of the membranes drastically reduced the cell performance and the discharge charge retention ratio.

11: Separation membrane (ion exchange membrane)
21: anode
22: cathode
31: anode electrolyte inlet
32: anode electrolyte outlet
41: cathode electrolyte inlet
42: cathode electrolyte outlet
51: cell housing

Claims (16)

A separator for a redox flow cell produced from an ion conductive polymer comprising a partially branched multiblock copolymer,
Wherein the partially branched block copolymer comprises a first block made of a hydrophilic first polymer; A second block derived from a hydrophobic second polymer having two or more reactors respectively participating in a polymerization reaction at both ends so as to form a branching point forming a side chain on the main chain; And a third block, optionally made of a hydrophobic third polymer,
Wherein the first block is represented by the following Formula 1,
Wherein the hydrophobic second block is represented by the following general formula (2)
Wherein the third block is represented by the following chemical formula 3:
[Chemical Formula 1]

(2)

(3)

In Formula 1,
A is a single bond or an electron withdrawing group - (C = O) -, - (P = O) -, - (SO ₂ ) -, -CF ₂ - or - (C (CF ₃ ) ₂ ) -;
B and B 'each independently represent -O-, -S-, -NH- or -NR ₁₃ - as a single bond or electron donor group, wherein R ₁₃ is a C 1 to C 6 alkyl group;
M is a hydrogen atom or an alkali metal;
Ar is an aromatic molecule or aromatic molecule group substituted with at least one sulfonic acid group (-SO ₃ H) or its alkali metal salt;
a and b each represent an integer belonging to 0 to 10,
k is an integer belonging to 1 to 4,
c is an integer belonging to 1 to 10,000,

In Formula 2 or Formula 3,
R ₁ to R ₄ and R ₁ 'to R ₄ ' each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkyl group substituted with a halogen, an allyl group, a cyano group, an aryl group, a sulfonic acid group, , Perfluoroalkyl groups, perfluoroalkylaryl groups optionally containing one or more oxygen, nitrogen or sulfur atoms on the chain, perfluoroaryl groups or -O-perfluoroaryl groups;
D ₁ , D ₂ , D ₁ 'and D ₂ ' are each independently -O-, -S-, -NH- or -NR ₁₄ - as an electron donor group, wherein R ₁₄ is a C 1 to C 6 alkyl group;
_{J 1, J 2, J 1} ' _2, and J' is a bond or an electron withdrawing group one are each independently - (C = O) -, - (P = O) -, - (SO 2) -, -CF 2 - or _{- (C (CF 3) 2} ) -,
E and E 'are each independently -O-, -S-, -NH- or -NR ₁₅ - as an electron donor group, wherein R ₁₅ is a C 1 to C 6 alkyl group;
Ar and Ar 'each independently represent a group selected from the group consisting of an unsubstituted or substituted with at least one halogen atom (-X), an alkyl group halogen-substituted alkyl group, an allyl group, a cyano group, an aryl group, a sulfonic acid group, a phosphoric acid group, An aryl group substituted with a functional group selected from the group consisting of a perfluoroalkyl group, a perfluoroaryl group and an -O-perfluoroaryl group, optionally containing one or more oxygen, nitrogen or sulfur atom in its chain, , A naphthyl group, an anthracenyl group,

or

,
P and P 'are each independently a single bond, a group selected from -O-, -S-, -NH- or -NR ₁₆ - (R ₁₆ is a C 1 to C 6 alkyl group) as an electron donor group, a - (C = O) -, - (P = O) -, - (SO 2) -, -CF 2 -, - (C (CH 3) 2) - or _{- (C (CF 3) 2} ) - ,
R ₅ to R ₁₂ and R ₅ 'to R ₁₂ ' each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkyl group substituted with a halogen, an allyl group, a cyano group, an aryl group, a sulfonic acid group, , A perfluoroalkyl group, a perfluoroalkylaryl group optionally containing one or more oxygen, nitrogen or sulfur atoms in its chain, a perfluoroaryl group or an -O-perfluoroaryl group,

In the above formulas (1) to (3), the sulfonic acid group, phosphoric acid group and acetic acid group may be in the form of an alkali metal salt;
p and p 'each represent an integer belonging to 1 to 1000,
q and q 'each represent an integer belonging to 0 to 5,
w and w 'are integers belonging to 1 to 10, respectively.
The method according to claim 1,
Wherein the first to third blocks are arranged in a random, alternating, block, or sequential manner.
The method according to claim 1,
Ar in Formula 1 is phenyl, naphthyl, thiophenyl or pyridinyl substituted with at least one sulfonic acid group or an alkali metal salt thereof.
The method according to claim 1,
Wherein the ion conductive polymer has a number-average molecular weight (M _n ) of 10,000 to 1,000,000 or a weight-average molecular weight (M _w ) of 10,000 to 10,000,000.
The method according to claim 1,
Wherein the partial branched block copolymer has a skeleton containing a repeating unit represented by the following formula (4):
[Chemical Formula 4]

Each letter in formula (4) is as defined in claim 1,
l and m are each independently an integer of 1 or more, and n is an integer of 0 or more.
6. The method of claim 5,
Wherein the partial branched block copolymer has l: m + n (molar ratio) of 0.1: 1 to 100: 1.
6. The method of claim 5,
0.5? N / (m + n) <1.
The method according to claim 1,
A is - (C = O) -;
Ar is phenyl substituted with one sulfonic acid group or its sodium salt;
a and b are each 0,
R ₁ to R ₄ , and R ₁ 'to R ₄ ' are both hydrogen atoms;
D ₁ , D ₂ , D ₁ 'and D ₂ ' are both -O-;
J ₁ , J ₂ , J ₁ 'and J ₂ ' are both - (C═O) -;
E and E 'are -O-;
Ar ' and Ar ''

And

, P is - (SO ₂ ) -, R ₅ to R ₁₂ , and R ₅ 'to R ₁₂ ' are both hydrogen atoms;
w = 2,
q = 1.
The method according to claim 1,
Wherein the separation membrane is a composite membrane formed by impregnating a nanoparticle support with a polymer membrane or an ion conductive polymer forming the ion conductive polymer itself.
10. The method of claim 9,
Wherein the nano web support is selected from the group consisting of polyimide, polymethylpentene, polyester, polyacrylonitrile, polyvinylamide, polyethylene, polypropylene, polyvinyl fluoride, polyvinyl difluoride, nylon, polybenzoxazole, polyethylene terephthalate , Polytetrafluoroethylene, polyarylene ether sulfone, polyether ether ketone, and combinations thereof.
A redox flow battery comprising a positive electrode, a positive electrode electrolyte, a separation membrane according to any one of claims 1 to 10, a negative electrode electrolyte and a negative electrode.
12. The method of claim 11,
The redox flow battery includes a cell housing 51 having a predetermined size,
An ion exchange membrane 11 disposed across the center of the cell housing,
An anode (21) and a cathode (22) electrode located on both left and right sides separated by the ion exchange membrane inside the cell housing,
A positive electrode electrolyte inlet 31 and a positive electrode electrolyte outlet 32 formed at the upper and lower ends of the cell housing on the side where the positive electrode is located to perform the inflow and outflow of the electrolyte used for the positive electrode,
And a negative electrode electrolyte inlet (41) and a negative electrode electrolyte outlet (42) formed at the upper and lower ends of the cell housing on the side of the cathode electrode to perform the inflow and outflow of the electrolyte used for the negative electrode.
12. The method of claim 11,
Wherein the cathode is a pre-vanadium-based redox battery using a V (IV) / V (V) redox couple as the positive electrode electrolyte and a V (II) / V (III) redox couple as a negative electrode electrolyte. battery.
12. The method of claim 11,
Wherein the cathode is a vanadium-based redox battery in which a halogen redox couple is used as the positive electrode electrolyte and a redox couple of V (II) / V (III) is used as a negative electrode electrolyte.
12. The method of claim 11,
Characterized in that the battery is a polysulfide bromine redox battery using a halogen redox couple as the positive electrode electrolyte and a sulfide redox couple as the negative electrode electrolyte.
12. The method of claim 11,
Wherein the battery is a zinc-bromine (Zn-Br) redox battery using a halogen redox couple as the positive electrode electrolyte and a zinc redox couple as a negative electrode electrolyte.

Images