KR102728980B1 - Ion transport polymer, method for preparing the same and electrolyte membrane comprising the same - Google Patents

Abstract

The present invention relates to an ion transfer polymer, a method for producing the same, and an electrolyte membrane comprising the same. More specifically, the ion transfer polymer comprises polyphenylene having only carbon-carbon bonds in its main chain, thereby exhibiting excellent chemical durability and mechanical stability when introduced into a battery as an electrolyte membrane, thereby improving long-term use stability.

Description

Ion transport polymer, method for preparing the same, and electrolyte membrane comprising the same {ION TRANSPORT POLYMER, METHOD FOR PREPARING THE SAME AND ELECTROLYTE MEMBRANE COMPRISING THE SAME}

The present invention relates to an ion transfer polymer, a method for producing the same, and an electrolyte membrane comprising the same.

A fuel cell is an energy conversion device that directly converts the chemical energy of fuel into electrical energy. In other words, a fuel cell is a power generation method that uses fuel gas and an oxidizer and produces electricity by utilizing the electrons generated during their redox reaction. The membrane-electrode assembly (MEA) of a fuel cell is the part where the electrochemical reaction of hydrogen and oxygen occurs, and is composed of an anode, a cathode, and an electrolyte membrane (ion exchange membrane).

A redox flow battery (RFB) is an electrochemical storage device that directly stores the chemical energy of an active substance as electrical energy by charging and discharging the active substance contained in an electrolyte through oxidation and reduction. The unit cell of a redox flow battery includes an electrode, an electrolyte, and an electrolyte membrane (ion exchange membrane).

Fuel cells and redox flow batteries are being researched and developed as next-generation energy sources due to their high energy efficiency and environmentally friendly characteristics of low pollutant emissions.

The most important component in fuel cells and redox flow cells is the electrolyte membrane capable of cation exchange, namely the proton exchange membrane (PEM). The electrolyte membrane material must have excellent proton (hydrogen ion) conductivity, prevention of electrolyte crossover, high thermal and chemical stability, excellent mechanical properties, and low swelling ratio.

Electrolyte membranes currently used in fuel cells and redox flow cells are largely divided into fluorine-based and hydrocarbon-based.

Electrolyte membranes using fluorinated polymer materials are based on perfluorosulfonic acid polymer membranes, and DuPont's Nafion is a representative example. Fluorinated polymers such as Nafion generally exhibit excellent chemical stability and proton conductivity at high relative humidity (HR) and low temperatures, but their practical battery applications are limited due to disadvantages such as high cost, high methanol permeability, insufficient thermomechanical properties above 80°C, and environmental hazards associated with disposal.

Accordingly, many studies are being conducted with a focus on non-fluorinated polymeric proton-conducting materials with low cost and high performance. Specifically, various hydrocarbon polymers such as polybenzimidazole, polybenzoxazole, poly(ether sulfone), poly(ether ketone)s, etc. are being applied to the production of electrolyte membranes for fuel cells or redox flow batteries. These hydrocarbon polymers are receiving much attention because their synthesis process is environmentally friendly and they exhibit high mechanical strength and thermal stability compared to fluorinated polymers.

However, in order to secure proton conductivity at the level of fluorine-based electrolyte membranes, electrolyte membranes using these hydrocarbon-based polymers introduce hydrophilic ionic groups such as ether groups and sulfonic acid groups. As a result, excessive swelling due to moisture causes mechanical properties to deteriorate, reducing the chemical durability of the electrolyte membrane and causing some of the sulfonated resin to be eluted.

To complement these problems, a method was proposed to introduce a cross-linking structure through covalent bonds into the raw resin to lower the water solubility of the electrolyte membrane and suppress the dissolution of the resin.

For example, Korean Patent Publication No. 2015-0118675 discloses that the low mechanical strength of a hydrocarbon-based electrolyte membrane can be improved by manufacturing a separator for a redox flow battery using a partially branched block copolymer including a hydrophilic block and a hydrophobic polymer having two or more reactive groups capable of being partially branched.

These patents have improved the mechanical properties of hydrocarbon-based electrolyte membranes to some extent, but the effects are not sufficient, and the polymers obtained by crosslinking are difficult to synthesize and manufacture membranes using, and the fluidity of the polymers decreases due to the increase in the glass transition temperature (T _g ), so that the mechanical properties, chemical durability, and long-term stability of the membranes are insufficient. Therefore, there is a growing need for the development of electrolyte membranes that exhibit excellent proton conductivity and high thermal, chemical, and mechanical stabilities and that can maintain them in the long term.

Korean Patent Publication No. 2015-0118675 (October 23, 2015), Separator manufactured from ion-conducting polymer including partially branched block copolymer and redox flow battery having the same

Accordingly, the inventors of the present invention conducted a multifaceted study to solve the above problem and, as a result, confirmed that mechanical and chemical stability are improved when a novel polyphenylene polymer containing only carbon-carbon bonds in the main chain is used as an electrolyte membrane material, thereby completing the present invention.

Therefore, the purpose of the present invention is to provide an ion transport polymer having excellent mechanical properties and chemical durability.

In addition, another object of the present invention is to provide a method for producing the ion transfer polymer.

In addition, another object of the present invention is to provide a fuel cell and a redox flow battery including the electrolyte membrane.

To achieve the above object, the present invention provides an ion transfer polymer comprising polyphenylene represented by the following chemical formula 1:

[Chemical Formula 1]

(In the above chemical formula 1, n and m follow the description in the specification.)

The above ion-transporting polymer may have a weight average molecular weight of 3.0×10 ⁵ to 1.0×10 ⁶ .

The above ion-transporting polymer may have a number average molecular weight of 1.0×10 ⁵ to 8.0×10 ⁵ .

In addition, the present invention provides an electrolyte membrane comprising the ion transfer polymer.

The ionic conductivity of the above electrolyte membrane can be 0.03 to 0.2 S/cm.

The ion exchange capacity value of the above electrolyte membrane can be 0.5 to 2.0 mmol/g.

The thickness of the above electrolyte membrane may be 20 to 100 ㎛.

In addition, the present invention provides a membrane-electrode assembly including the electrolyte membrane.

In addition, the present invention provides a fuel cell including the membrane-electrode assembly.

In addition, the present invention provides a redox flow battery including an electrolyte membrane.

In addition, the present invention provides a method for producing an ion transport polymer comprising polyphenylene of the chemical formula 1.

The ion transport polymer according to the present invention comprises polyphenylene composed only of carbon bonds without any heteroatoms in the polymer main chain, so that no attack reaction by nucleophiles such as hydrogen peroxide, hydroxide anions, and radicals occurs, and thus the chemical durability and mechanical stability of the electrolyte membrane are excellent, and thus it has the advantage of being usable for long periods of time.

Figure 1 is a graph showing the results of NMR measurement according to Experimental Example 1 of the present invention.
Figure 2 is a graph showing the results of GPC measurement according to Experimental Example 1 of the present invention.
Figure 3 is a graph showing the results of chemical durability evaluation according to Experimental Example 1 of the present invention.

Hereinafter, the present invention will be described in more detail.

The terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as having meanings and concepts that conform to the technical idea of the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to explain his or her own invention in the best manner.

The terminology used herein is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In the present invention, it should be understood that the terms “comprise” or “have” are intended to specify that a feature, number, step, operation, component, part or combination thereof described in the specification is present, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

In this specification, “electrolyte membrane” is a membrane capable of exchanging ions, and may mean a separation membrane, an ion exchange membrane, an ion transfer membrane, an ion conductive membrane, an electrolyte membrane, an ion exchange electrolyte membrane, an ion transfer electrolyte membrane, an ion conductive electrolyte membrane, an ion exchange electrolyte membrane, an ion transfer electrolyte membrane, or an ion conductive electrolyte membrane.

Fuel cells and redox flow batteries are attracting attention as next-generation large-capacity secondary batteries due to their superior power generation efficiency, large-capacity, and environmental friendliness.

In these fuel cells, redox flow cells, and energy storage systems, the electrolyte membrane is a key component that determines performance and durability, but since Korea currently does not have the relevant technology, it relies entirely on imports despite the very high price.

The electrolyte membrane currently used is a fluorine-based electrolyte membrane represented by Nafion. This has excellent performance and low-temperature durability, but it is very expensive, the synthesis process is not environmentally friendly, and the electrolyte crossover is severe, and the physical properties deteriorate rapidly at high temperatures.

For this purpose, an electrolyte membrane using a hydrocarbon polymer has been proposed, and since hydrocarbon electrolyte membranes are superior to fluorine-based electrolyte membranes in terms of mechanical strength and thermal stability and do not cause environmental pollution during manufacturing, much research on hydrocarbon-based electrolyte membranes is currently being conducted.

However, since the hydrocarbon polymer used in the electrolyte membrane contains a hydrophilic ionic group as described above and is generally synthesized using a nucleophilic aromatic substitution reaction (S _N Ar), the main chain of the hydrocarbon polymer inevitably contains a C-hetero atom (O or S) bond. This bond with the hydrophilic ionic group or hetero atom is decomposed by hydrogen peroxide, oxygen radicals, or anions generated when the battery is operated, so the hydrocarbon electrolyte membrane has weak chemical durability and mechanical properties, and has the disadvantage of having problems with long-term use.

Accordingly, the present invention provides an ion transfer polymer including a polyphenylene polymer in which the main chain of the polymer consists only of carbon-carbon bonds, so as to ensure that the hydrocarbon-based electrolyte membrane has excellent cation conductivity while also improving chemical durability, mechanical properties, and long-term stability.

Specifically, the ion transfer polymer according to the present invention comprises polyphenylene represented by the following chemical formula 1:

[Chemical Formula 1]

(In the above chemical formula 1,

n and m are mole fractions, each independently a real number greater than 0 and equal to 1, and m is 1-n.)

In the above chemical formula 1, n and m are mole fractions with respect to the entire polymer, and preferably, n may be 0.1 to 0.9, and m may be 0.1 to 0.9.

In the present invention, the polyphenylene of the chemical formula 1 contains only carbon-carbon bonds in the main chain, and therefore has superior chemical durability and mechanical properties compared to conventional hydrocarbon polymers manufactured by a nucleophilic substitution reaction, and thus has structural characteristics advantageous for long-term use.

In addition, the ion transport polymer according to the present invention includes two types of repeating units as shown in the chemical formula 1, and the arrangement of each repeating unit is expressed as above for convenience, but is not particularly limited in the present invention. For example, the repeating unit may be random, alternating, or block.

The above ion transfer polymer may have a weight average molecular weight (M _w ) of 3.0×10 ⁵ to 1.0×10 ⁶ , preferably 3.0×10 ⁵ to 5.0×10 ⁵ . If the weight average molecular weight of the ion transfer polymer is less than the above range, there is a problem of brittleness, and conversely, if it exceeds the above range, the efficiency of the film forming process may be reduced due to ultra-high viscosity.

The above ion transfer polymer may have a number average molecular weight (M _n ) of 1.0×10 ⁵ to 8.0×10 ⁵ , preferably 1.0×10 ⁵ to 2.0×10 ⁵ . If the number average molecular weight of the ion transfer polymer is less than the above range, there is a problem of brittleness, and conversely, if it exceeds the above range, the viscosity may be too high, which may deteriorate the film forming processability.

In addition, the ion transport polymer may have a polydispersity index (PDI) of 1.5 to 5.0. Here, the term “polydispersity index” used in the present invention means a value obtained by dividing the weight average molecular weight by the number average molecular weight, and means weight average molecular weight/number average molecular weight (M _w /M _n ).

In addition, the present invention provides a method for producing the above-described ion transport polymer.

The method for producing an ion transport polymer according to the present invention includes a step of performing a polymerization reaction of a monomer of chemical formula 2, a monomer of chemical formula 3, and a ketone crosslinker of chemical formula 4 in the presence of a catalyst, as shown in the following reaction scheme 1:

[Reaction Formula 1]

(In the above chemical formula 1,

n and m are mole fractions, each independently a real number greater than 0 and equal to 1, and m is 1-n.)

In the case of polyphenylene polymers manufactured using conventional catalysts, they have a rigid chemical structure and are brittle, making them difficult to use as electrolyte membranes. However, the method for manufacturing an ion transfer polymer suggested in the present invention includes a ketone cross-linking agent represented by chemical formula 4, thereby enabling the manufacture of an ion transfer polymer including polyphenylene of chemical formula 1 having a high molecular weight and improved mechanical properties through a simple process.

The ketone cross-linking agent of the above chemical formula 4 acts as a brancher to connect or cross-link polymer chains. The ketone cross-linking agent of the above chemical formula 4 can be directly synthesized through a method commonly performed in the art or can be purchased as a commercially available product and used.

The monomer of the above chemical formula 2 is 2,5-dichlorobenzophenone (2,5-DCBP), and the monomer of the above chemical formula 3 is sulfonated 2,5-dichlorobenzophenone, which can be directly synthesized using a method commonly performed in the art or can be purchased and used as a commercially available product.

The catalyst includes nickel bromide, zinc, and triphenylphosphine. In the manufacturing method according to the present invention, by mixing and reacting compounds of chemical formulas 2 to 4 using the catalyst, it is possible to manufacture an ion transfer polymer including polyphenylene composed only of carbon-carbon bonds without carbon-hetero atom bonds in the polymer main chain.

The above polymerization reaction is carried out in a solvent phase, and the solvent may be an organic solvent. The organic solvent is not particularly limited, but for example, toluene, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, xylene, benzene, n-butyl acetate, methylcyclohexane, dimethylcyclohexane, etc. may be used.

The above polymerization reaction can be carried out at a temperature range of room temperature to 100°C, preferably room temperature to 60°C, for 3 to 6 hours, and the reaction temperature or time may vary depending on the conditions.

In addition, the present invention provides an electrolyte membrane comprising the above-described ion transport polymer.

In the present invention, the electrolyte membrane includes an ion transfer polymer including polyphenylene of the chemical formula 1 described above, thereby exhibiting good ion conductivity and having superior chemical durability and mechanical properties compared to conventional membranes, thereby enabling long-term use when introduced into a battery.

The ionic conductivity of the above electrolyte membrane may be 0.03 to 0.2 S/cm. If the ionic conductivity of the above electrolyte membrane is below the above range, there is a problem that the resistance is large during charging and discharging, making charging difficult. On the other hand, if it exceeds the above range, the durability of the membrane may be reduced.

The ion exchange capacity (IEC) value of the above electrolyte membrane may be 0.5 to 2.0 mmol/g, preferably 0.9 to 1.5 mmol/g. When the ion exchange capacity value is within the above range, ion channels are formed in the electrolyte membrane and the ion transfer polymer may exhibit ion conductivity.

The thickness of the electrolyte membrane may be 20 to 100 ㎛, preferably 25 to 50 ㎛. If the thickness of the electrolyte membrane is less than the above range, there may be a problem with durability or permeability that may be vulnerable to the flow pressure between electrolytes when applied during battery charging and discharging, and on the contrary, if it exceeds the above range, the membrane resistance may be large, which may deteriorate the charge and discharge performance.

In addition, the present invention provides a membrane-electrode assembly including an anode; a cathode; and the above-described electrolyte membrane between the anode and the cathode.

The above membrane electrode assembly (MEA) refers to a joint of electrodes (anode and cathode) where an electrochemical catalytic reaction of fuel and air occurs and a polymer membrane where hydrogen ion transport occurs, and is a single integrated unit in which the electrodes (anode and cathode) and the electrolyte membrane are bonded.

In the present invention, the membrane-electrode assembly can be manufactured in a form in which the catalyst layer of the cathode and the catalyst layer of the anode are in contact with the electrolyte membrane, and can be manufactured by a conventional method known in the art. For example, the membrane-electrode assembly can be manufactured by thermally compressing at 100 to 400° C. while the anode; the cathode; and the electrolyte membrane positioned between the anode and the cathode are in close contact with each other.

The above cathode may include a cathode catalyst layer and a cathode gas diffusion layer. The cathode gas diffusion layer may further include a cathode microporous layer and a cathode substrate.

The above anode may include an anode catalyst layer and an anode gas diffusion layer. The above anode gas diffusion layer may further include an anode microporous layer and an anode substrate.

In a fuel cell, the most basic unit that generates electricity is a membrane-electrode assembly (MEA), which consists of an electrolyte membrane and a cathode and an anode formed on both sides of the electrolyte membrane. The principle of electricity generation in a fuel cell is that at the cathode, an oxidation reaction of fuel such as hydrogen or a hydrocarbon such as methanol or butane occurs, generating hydrogen ions (H ⁺ ) and electrons (e ^- ), and the hydrogen ions move to the anode through the electrolyte membrane. At the anode, the hydrogen ions transferred through the electrolyte membrane react with an oxidizing agent such as oxygen and electrons to produce water. This reaction causes the movement of electrons to the external circuit.

The catalyst layer of the above cathode is where the oxidation reaction of the fuel occurs, and a catalyst selected from the group consisting of platinum, ruthenium, osmium, a platinum-ruthenium alloy, a platinum-osmium alloy, a platinum-palladium alloy, and a platinum-transition metal alloy can be preferably used. The catalyst layer of the above anode is where the reduction reaction of the oxidizing agent occurs, and platinum or a platinum-transition metal alloy can be preferably used as the catalyst. The above catalysts can be used as they are or supported on a carbon-based carrier.

The process of introducing the above catalyst layer can be performed by a conventional method known in the art, for example, the catalyst layer can be formed by directly coating the catalyst ink on the electrolyte membrane or by coating the gas diffusion layer. At this time, the coating method of the catalyst ink is not particularly limited, but spray coating, tape casting, screen printing, blade coating, die coating, or spin coating methods can be used. The catalyst ink can be typically composed of a catalyst, a polymer ionomer, and a solvent.

The above gas diffusion layer functions as a current conductor and as a passage for the reaction gas and water, and has a porous structure. Therefore, the gas diffusion layer may be formed by including a conductive substrate. Carbon paper, carbon cloth or carbon felt can be preferably used as the conductive substrate. The gas diffusion layer may further include a microporous layer between the catalyst layer and the conductive substrate. The microporous layer can be used to improve the performance of the fuel cell under low-humidity conditions, and serves to reduce the amount of water escaping from the gas diffusion layer, thereby ensuring that the electrolyte membrane is sufficiently wet.

In addition, the present invention provides a fuel cell including two or more of the above-described membrane-electrode assemblies; a stack including a bipolar plate provided between the membrane-electrode assemblies; a fuel supply unit for supplying fuel to the stack; and an oxidizer supply unit for supplying an oxidizer to the stack.

The above fuel cell is an energy conversion device that directly converts the chemical energy of fuel into electrical energy. In other words, a fuel cell is a power generation method that uses fuel gas and an oxidizer and produces electricity by utilizing electrons generated during their redox reaction.

The above fuel cell can be manufactured using the membrane-electrode assembly (MEA) described above according to a conventional method known in the art. For example, it can be manufactured by configuring the membrane-electrode assembly (MEA) manufactured above and a bipolar plate.

The above fuel cell comprises a stack, a fuel supply unit, and an oxidizer supply unit. The stack comprises one or more of the above-described membrane electrode assemblies, and when two or more membrane electrode assemblies are included, a separator interposed between them. The separator prevents the membrane electrode assemblies from being electrically connected and transfers fuel and oxidizer supplied from the outside to the membrane electrode assemblies. The oxidizer supply unit supplies an oxidizer to the stack. Oxygen is typically used as the oxidizer, and oxygen or air can be injected by a pump and used.

The above fuel supply unit serves to supply fuel to the stack, and may be composed of a fuel tank for storing fuel and a pump for supplying fuel stored in the fuel tank to the stack. Hydrogen or hydrocarbon fuel in a gaseous or liquid state may be used as the fuel. Examples of the hydrocarbon fuel include methanol, ethanol, propanol, butanol, or natural gas.

The above fuel cell may be a polymer electrolyte fuel cell, a direct liquid fuel cell, a direct methanol fuel cell, a direct formic acid fuel cell, a direct ethanol fuel cell, or a direct dimethyl ether fuel cell.

When the electrolyte membrane according to the present invention is used as an ion exchange membrane of a fuel cell, the above-described effects can be exhibited.

In addition, the present invention provides a redox flow battery including a positive electrode cell including a positive electrode and a positive electrode electrolyte; a negative electrode cell including a negative electrode and a negative electrode electrolyte; and the above-described electrolyte membrane provided between the positive electrode cell and the negative electrode cell.

The above redox flow battery (oxidation-reduction flow battery) is an electrochemical storage device that directly stores the chemical energy of the active material as electrical energy in a system in which the active material contained in the electrolyte is oxidized and reduced to be charged and discharged. The redox flow battery utilizes the principle that when electrolytes containing active materials with different oxidation states meet across an ion exchange membrane, electrons are exchanged to perform charging and discharging. In general, a redox flow battery is composed of a tank containing an electrolyte, a battery cell where charging and discharging occur, and a circulation pump for circulating the electrolyte between the tank and the battery cell, and a unit cell of the battery cell includes an electrode, an electrolyte, and an ion exchange membrane.

When the electrolyte membrane according to the present invention is used as an ion exchange membrane of a redox flow battery, the above-described effects can be exhibited.

In the present invention, the redox flow battery can be manufactured according to a conventional method known in the art, except that it includes an electrolyte membrane according to the present invention.

Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical idea of the present invention, and it is natural that such changes and modifications fall within the scope of the appended patent claims.

Examples and Comparative Examples

[Example 1]

A 250 mL three-necked round bottomed flask equipped with a Dean-Stark trap, a nitrogen inlet, and a mechanical stirrer was charged with 0.310 g (0.00142 mmol) of nickel bromide (NiBr ₂ ), 2.618 g (0.00998 mmol) of triphenylphosphine (PPh ₃ ), and 5.230 g (0.080 mmol) of zinc as a catalyst. 10 mL of N,N-dimethylacetamide (DMAc) was added and the reaction was allowed to activate the catalyst.

Next, 3.6411 g (0.014 mmol) of 2,5-dichlorobenzophenone (2,5-DCBP), 1.9423 g (0.0055 mmol) of sulfonated 2,5-dichlorobenzophenone, and 0.1444 g (0.0002 mmol) of a ketone cross-linker of chemical formula 4 were dissolved in 10 mL of N,N-dimethylacetamide (DMAc) and placed into the flask, and the temperature was increased to 90°C to allow the reaction to proceed for 4 hours.

Thereafter, the temperature of the obtained mixture was lowered to room temperature, poured into 10 wt% hydrochloric acid/acetone, and the precipitated solid was filtered and dried to obtain an ion transfer polymer.

[Comparative Example 1]

Nafion 115 was used as an ion transport polymer.

Experimental Example 1. Property Evaluation

The physical properties of the ion transport polymers of the above examples and comparative examples were measured and the results are shown in Tables 1 to 3 and Figures 1 to 3 below. The physical property evaluation method is as follows.

(1) ¹ H NMR (Nuclear Magnetic Resonance) Measurement

The ion transfer polymer according to the example was dissolved in CDCl ₃ solvent and measured using an NMR spectrometer (Bruker 700 MHz NMR, Bruker).

(2) Molecular weight measurement

The ion transport polymer manufactured in the example was dissolved in Tetra Hydro Furan (THF) at a concentration of 4000 ppm, and the number average molecular weight and weight average molecular weight were measured using gel permeation chromatography (GPC (0 to 100,000 g/mol).

Average molecular weight Weight average molecular weight PDI Example 1 130,000 437,000 3.35

(3) Measurement of ion conductivity and ion exchange capacity values

An electrolyte membrane having a thickness of 50 ㎛ was manufactured by casting a 20 wt% transparent solution obtained by dissolving the ion transport polymer manufactured in the example in dimethyl sulfoxide (DMSO) at 80°C.

The ionic conductivity of the membrane was measured by immersing a 1 cm × 3 cm square electrolyte membrane sample in distilled water, stabilizing it for 20 to 30 minutes, and then applying a constant alternating current to both ends of the electrolyte membrane sample at 100% humidity and 25°C and measuring the AC potential difference that occurs at the center of the electrolyte membrane sample. The ionic conductivity measuring device used was a Scribner membrane test system (MTS-740) equipped with a Newton´s 4th Ltd. (N4L) impedance analysis interface (PSM 1735) capable of measuring ionic conductivity in the through-plane of the sample.

A titration method was used to determine the ion exchange capacity of the membrane (DW Seo, YD Lim, SH Lee, IS Jeong, DI Kim, JH Lee, and WG Kim, Int . J. Hydrogen Energy 37, 6140 (2012)). The acid form (H ⁺ ) membrane was converted to the sodium salt form by exchanging H ⁺ ions and Na ⁺ ions by immersion in a 1.0 M NaCl solution for 24 h. Afterwards, the exchanged H ⁺ ions in the solution were titrated with 0.05 N NaOH solution.

The theoretical IEC calculated from the degree of sulfonation (DS) was calculated using the following mathematical expression 1.

[Mathematical formula 1]

IEC (mmol/g) = mmol concentration of ion / dry film weight at 25°C

Ion exchange capacity value
[mmol/g] Ionic conductivity
[S/cm] Example 1 1.1 0.034

(4) Measurement of vanadium permeability

The vanadium permeability of the electrolyte membrane using the ion transport polymers of Example 1 and Comparative Example 1 was measured.

Vanadium permeability was measured as the concentration of VO2+ in a 1M _MgSO4 in 2M _{H2SO4 solution} over time using an electrolyte membrane placed _between 1M _VOSO4 in 2M _H2SO4 solution on one side and 1M _MgSO4 in 2M _{H2SO4 solution} on the other side. The active area was 7.69 cm2, the volume was ₂₀₀ ^ml , and the measurement was performed at room temperature.

_VO2 ⁺ permeability
(㎠/min) Example 1 0 Comparative Example 1 5.84x10 ^-6

(5) Chemical durability

The chemical durability of the electrolyte membrane using the ion transport polymers of Example 1 and Comparative Example 1 was evaluated.

After impregnating the electrolyte membrane manufactured with the above polymer in an electrolyte solution under the condition of 1.6 V-3.5 H VO ₂ ⁺ , the chemical durability of the membrane was evaluated through a UV test every week.

Figure 1 shows the chemical structure of the ion transfer polymer confirmed using ¹ H NMR. The chemical shift values of 2,5-dichlorobenzophenone (2,5-DCBP) represented by Chemical Formula 2 showed a phenyl ring proton peak at 7.4 to 7.8 ppm, and the sulfonated 2,5-dichlorobenzophenone represented by Chemical Formula 3 also showed a phenyl ring proton peak at 7.4 to 7.8 ppm. In the case of the ion transfer polymer of Example 1 manufactured according to the present invention, it can be confirmed that the phenyl ring proton peak appeared at 7.0 to 8.0 ppm, and the corresponding proton peak shifted downfield and a broader peak was formed.

The molecular weight of the ion transfer polymer according to the present invention is as shown in Table 1, and the ion conductivity and ion exchange capacity values of the electrolyte membrane manufactured from the ion transfer polymer of the example are as shown in Table 2.

In addition, as shown in Table 3, in the case of the electrolyte membrane including the ion transfer polymer according to Example 1, it can be confirmed that the permeability of vanadium ions is significantly lower than that of the Nafion 115 electrolyte membrane of Comparative Example 1 because the polymer main chain is composed of carbon-carbon bonds. From these results, it can be predicted that the performance of the electrolyte membrane including the ion transfer polymer according to the present invention is excellent because the crossover of vanadium ions (VO ₂₊ ⁾ due to the Donnan effect can be effectively suppressed.

In addition, in the case of the electrolyte membrane including the ion transfer polymer according to Example 1 through FIG. 3, when impregnated in harsh electrolyte conditions for more than one month, there was almost no change from V ⁵⁺ in the electrolyte to V ⁴⁺ , which confirms that the membrane has excellent chemical durability because there is no mutual influence even under harsh electrolyte conditions. From these results, it can be seen that the electrolyte membrane including the ion transfer polymer according to the present invention has improved chemical durability compared to the electrolyte membrane including Comparative Example 1 because the main chain does not include a hetero atom.

Claims (13)

delete delete delete delete delete delete delete delete delete delete As shown in the following reaction scheme 1,
A method for producing an ion transfer polymer comprising polyphenylene of chemical formula 1, comprising the step of performing a polymerization reaction of a monomer of chemical formula 2, a monomer of chemical formula 3, and a ketone crosslinking agent of chemical formula 4 in the presence of a catalyst:
[Reaction Formula 1]

(In the above chemical formula 1,
n and m are mole fractions, each independently a real number greater than 0 and equal to 1, and m is 1-n.) In Article 11,
A method for producing a polyphenylene polymer, wherein the catalyst comprises nickel bromide, zinc and triphenylphosphine. In Article 11,
A method for producing a polyphenylene polymer, wherein the above polymerization reaction is performed at a temperature range of room temperature to 100°C.