KR20160134067A - Electrolyte membrane, preparing the same and fuel cell including the same - Google Patents

Abstract

The present invention relates to an electrolyte membrane, a method for preparing the same, and a fuel cell comprising the same. Provided is the electrolyte membrane, comprising: an inorganic ion conductor represented by chemical formula 1: M^1_(1-a)M^2_aP_xO_y; and a polymer represented by chemical formula 2 or by chemical formula 3. In the chemical formula 1: M^1 is a metal element having an oxidation state of 4; M^2 is a metal element having an oxidation state of 1, a metal element having an oxidation state of 2, or a metal element having an oxidation state of 3; and a, x, and y satisfies 0 <= a < 1, 1.5 <= x <= 3.5, and 5 <= y <= 13. In the chemical formula 2: L^1 to L^4 are independently a single bond, -C(=O)-, -O-, -S-, -S(=O)- or -S(=O)2-; m1 and m2 are independently an integer ranging from 0 to 100; and m1 + m2 is not 0. In the chemical formula 3: L^5 to L^7 are independently a single bond, -C(=O)-, -O-, -S-, -S(=O)- or -S(=O)_2-; and n is an integer ranging from 1 to 100.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrolyte membrane, a method of manufacturing the same, and a fuel cell including the electrolyte membrane.

An electrolyte membrane, a method of manufacturing the same, and a fuel cell including the same.

Recently, research on fuel cells as a fuel source of pollution-free automobiles, one of the researches on renewable energy, has received attention. Among them, PEMFC (Polymer Electrolyte Membrane Fuel Cell) has attracted great interest as a substitute for existing automobile engine due to its high energy efficiency, power characteristics and environmentally friendly characteristics.

In particular, PEMFCs operating at high temperature and humidification conditions of 100 ° C or higher, compared to PEMFCs operating at low temperatures, do not use a humidification device, so that it is known that the control of water management and the like is simple and the reliability of the system is high. In addition, since the resistance to poisoning of carbon monoxide (CO) at the fuel electrode is increased through the high-temperature operation, the impurity content criterion of the fuel can be relaxed and the reformer can also be simplified, and the concern about the high temperature humidification system is increasing.

The fluorine-based polymer electrolyte membranes (such as Nafion) currently used in general PEMFCs are difficult to operate at a high temperature due to a rapid increase in resistance due to dehydration when used at high temperature and low humidity, It is required to develop an electrolyte membrane for a fuel cell having chemical resistance and high ion conductivity.

One embodiment is to provide an electrolyte membrane having a high specific surface area and a high ionic conductivity.

Another embodiment is to provide a method for producing the electrolyte membrane.

Another embodiment is to provide a fuel cell comprising the electrolyte membrane.

One embodiment provides an electrolyte membrane comprising an inorganic ion conductor represented by the following formula (1) and a polymer represented by the following formula (2) or (3).

[Chemical Formula 1]

M ¹ _{1 - a} M ² _a P _x O _y

In Formula 1,

M ¹ is a tetravalent metal element,

M ² is a monovalent metal element, a divalent metal element or a trivalent metal element,

0? A <1, 1.5? X? 3.5, 5? Y? 13,

(2)

In Formula 2,

L ¹ to L ⁴ are each independently a single bond, -C (= O) - a, -, -O-, -S-, -S (= O) - or -S (= O) ₂

m1 and m2 are each independently an integer of 0 to 100, provided that m1 + m2 is not 0,

(3)

In Formula 3,

L ⁵ to L ⁷ are each independently a single bond, -C (= O) -, -O-, -S-, -S (= O) - or -S (= O) ₂ -, and

n is an integer of 1 to 100;

M ² may be a trivalent metal element.

The M ² may be at least one selected from the group consisting of Al, Fe, Ga, Y, In, Sb, Bi, La, (Sm).

The M ¹ may be Sn, Zr, Ti, Ce or Si.

X may be an integer of 2, and y may be an integer of 7.

The specific surface area of the inorganic ion conductor may be 4.0 m ² / g to 90.0 m ² / g.

The electrolyte membrane may include 5 to 30% by weight of the inorganic ion conductor represented by Formula 1 and 70 to 95% by weight of the polymer, based on the total amount of the electrolyte membrane.

The inorganic ion conductor may be a porous inorganic ion conductor.

The average diameter of the pores in the porous inorganic ion conductor may be 2 nm to 100 nm.

The average diameter of the pores in the porous inorganic ion conductor may be from 2 nm to 50 nm.

The polymer may have a weight average molecular weight of 10,000 g / mol to 500,000 g / mol.

Another embodiment provides a method of making a semiconductor ^device , comprising: preparing a tetravalent metal oxide (M ¹ ) oxide; Mixing the oxidized tetravalent metal element oxide with a trivalent metal oxide (M ² ) oxide to obtain a mixture; Adding a phosphoric acid (H ₃ PO ₄₎ to the mixture; Heat-treating the phosphoric acid-added mixture to prepare an inorganic ion conductor represented by Formula 1 below; Preparing a composition for forming an electrolyte membrane by adding the inorganic ion conductor and a polymer represented by the following formula 2 or 3 to a solvent; And casting the composition for forming an electrolyte membrane on a substrate and drying the electrolyte membrane.

[Chemical Formula 1]

M ¹ _{1 - a} M ² _a P _x O _y

In Formula 1,

M ¹ is a tetravalent metal element,

M ² is a trivalent metal element,

0? A <1, 1.5? X? 3.5, 5? Y? 13,

(2)

In Formula 2,

L ¹ to L ⁴ are each independently a single bond, -C (= O) - a, -, -O-, -S-, -S (= O) - or -S (= O) ₂

m1 and m2 are each independently an integer of 0 to 100, provided that m1 + m2 is not 0,

(3)

In Formula 3,

L ⁵ to L ⁷ are each independently a single bond, -C (= O) -, -O-, -S-, -S (= O) - or -S (= O) ₂ -, and

n is an integer of 1 to 100;

The heat treatment may be performed at 200 ° C to 500 ° C for 1 hour to 5 hours.

The step of preparing the oxidized tetravalent metal element oxide comprises mixing an anionic surfactant and a cation salt of the tetravalent metal oxide element with a cationic salt to prepare a mixture; Adjusting the pH of the mixture to prepare a suspension solution; And filtering the suspension solution, and then removing the anionic surfactant.

The inorganic ion conductor may be a porous inorganic ion conductor.

The average diameter of the pores in the porous inorganic ion conductor may be from 2 nm to 100 nm.

The polymer may have a weight average molecular weight of 10,000 g / mol to 500,000 g / mol.

The solvent may include dimethylacetamide, dimethylformamide, tetrahydrofuran, N-methylpyrrolidone or a combination thereof.

Another embodiment provides a fuel cell comprising the electrolyte membrane.

The fuel cell may be a polymer electrolyte fuel cell (PEMFC).

Other details of the embodiments of the present invention are included in the following detailed description.

An inorganic ion conductor having improved specific surface area and ion conductivity can be applied together with a polymer to provide an electrolyte membrane for a fuel cell having high ion conductivity.

1 is an exploded perspective view showing a fuel cell according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a membrane electrode assembly (MEA) constituting a fuel cell.
3 is a graph showing hydrogen ion conductivity of an electrolyte membrane according to Example 1, Example 2, and Comparative Example 1. FIG.
4 is a nitrogen adsorption / desorption isotherm graph of the porous electrolyte membrane according to Example 1. Fig.
5 is a graph showing the results of measurement of the specific surface area of the porous electrolyte membrane (Example 1) and the non-porous electrolyte membrane (Example 3) according to the heat treatment temperature.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

It is to be understood that where a layer, film, region, plate, or the like is referred to as being "on" another portion, unless stated otherwise in this specification, .

The electrolyte membrane according to one embodiment includes an inorganic ion conductor represented by the following Chemical Formula 1 and a polymer represented by Chemical Formula 2 or Chemical Formula 3 below.

[Chemical Formula 1]

M ¹ _{1 - a} M ² _a P _x O _y

In Formula 1,

M ¹ is a tetravalent metal element,

M ² is a monovalent metal element, a divalent metal element or a trivalent metal element,

0? A <1, 1.5? X? 3.5, 5? Y? 13,

(2)

In Formula 2,

L ¹ to L ⁴ are each independently a single bond, -C (= O) - a, -, -O-, -S-, -S (= O) - or -S (= O) ₂

m1 and m2 are each independently an integer of 0 to 100, provided that m1 + m2 is not 0,

(3)

In Formula 3,

L ⁵ to L ⁷ are each independently a single bond, -C (= O) -, -O-, -S-, -S (= O) - or -S (= O) ₂ -, and

n is an integer of 1 to 100;

For example, in Formula 2, each of L ¹ to L ⁴ may independently be a single bond, -O- or -S (= O) ₂ -.

For example, in Formula 3, each of L ⁵ to L ⁷ may independently be -C (= O) - or -O-.

The inorganic ion conductor may have a cubic or pseudo-cubic crystal structure. Here, "pseudocubic" refers to a rhombohedral structure similar to a cubic structure. This crystal structure can be confirmed by analyzing the interplanar spacing obtained from the X-ray diffraction experiment.

Specifically, the inorganic ion conductor is a structure in which a tetravalent metal oxide forms a face-centered cubic structure and is located at a corner and an innermost portion, and a phosphate group (P ₂ O ₇ ) is located at an edge region and bonds with a metal oxide .

In addition, the inorganic ion conductor may be porous including many pores of various sizes. That is, the inorganic ion conductor may be a porous inorganic ion conductor, and in this case, the average diameter of the pores in the porous inorganic ion conductor may be 2 nm to 100 nm, for example, 2 nm to 50 nm. By forming the inorganic ion conductor into a porous structure, the ionic conductivity of the inorganic ion conductor can be improved by adding a water-soluble property under conditions of no humidification or low humidification (<50% RH, for example, <30% RH).

The specific surface area of the inorganic ion conductor may be 4.0 m ² / g to 90.0 m ² / g, for example 8.4 m ² / g to 85.5 m ² / g.

When the specific surface area of the inorganic ion conductor is within the above range, it is possible to achieve hydrogen ion conductivity of 0.01 S / cm to 0.1 S / cm at 75 to 200 ° C and <30% RH, Can be expected.

The M ² may be a trivalent metal oxide such as aluminum (Al), iron (Fe), gallium (Ga), yttrium (Y), indium (In), antimony (Sb), bismuth (Bi) , Neodymium (Nd), and samarium (Sm).

The M ¹ may be any one selected from the group consisting of tin (Sn), zirconium (Zr), titanium (Ti), cerium (Ce), and silicon (Si).

For example, x may be an integer of 2, and y may be an integer of 7.

For example, as the most specific example of the inorganic ion conductor, the inorganic ion conductor may be SnP ₂ O ₇ , Sn _{0 .85} Al _{0 .15} P ₂ O ₇ , Sn _{0 .90} Al _{0 .10} P ₂ O ₇ , Sn _{0 .93} Al _{0 .07} P ₂ O ₇ or Sn _{0 .95} Al _{0 .05} P ₂ O ₇ , but are not limited thereto.

The electrolyte membrane may include 5 to 30% by weight of the inorganic ion conductor represented by Formula 1 and 70 to 95% by weight of the polymer, based on the total amount of the electrolyte membrane. For example, the electrolyte membrane may include 5 to 20% by weight of the inorganic ion conductor represented by Formula 1 and 80 to 95% by weight of the polymer, based on the total amount of the electrolyte membrane.

When the content of the inorganic ion conductor represented by the above formula (1) is less than 5% by weight, the conductivity improving effect can not be obtained due to the decrease of the ion conduction path and humidifying effect under low humidification conditions. There is a drawback that the dispersibility of the particles is reduced and the mechanical strength of the electrolyte membrane is reduced.

The polymer represented by Formula 2 or Formula 3 may have a weight average molecular weight of 10,000 g / mol to 500,000 g / mol.

For example, the polymer represented by Formula 2 may be a copolymer comprising a repeating unit represented by Formula 2-a and a repeating unit represented by Formula 2-b.

[Chemical Formula 2-a]

[Formula 2-b]

In the above general formulas (2-a) and (2-b)

L ¹ to L ⁴ each independently represents a single bond, -C (= O) -, -O-, -S-, -S (= O) - or -S (= O) ₂ -.

For example, the polymer represented by Formula 3 may be a compound containing a repeating unit represented by the following Formula 3-a.

[Formula 3-a]

In the above formula (3-a)

L ⁵ to L ⁷ each independently represents a single bond, -C (= O) -, -O-, -S-, -S (= O) - or -S (= O) ₂ -.

For example, the polymer may be an ionomer for improving adhesion of the catalyst layer and transferring hydrogen ions.

The ionomer may be a polymer resin having hydrogen ion conductivity, specifically, a polymer resin having at least one cation-exchange group selected from a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group, Can be used. More specifically, examples of the polymer include fluorine polymer, benzimidazole polymer, polyimide polymer, polyetherimide polymer, polyphenylene sulfide polymer, polysulfone polymer, polyether sulfone polymer, polyether ketone polymer, poly Ether-ether ketone-based polymer, and polyphenylquinoxaline-based polymer may be used. More specifically, poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), copolymer of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid group, sulfated polyether ketone, aryl ketone, poly 2,2'-m-phenylene) -5,5'-bibenzimidazole] and poly (2,5-benzimidazole [ ) May be used.

The ionomer may be used singly or in the form of a mixture, and may optionally be used together with a nonconductive compound for the purpose of further improving the adhesion with the polymer electrolyte membrane. The amount of the nonconductive compound to be used is preferably adjusted to suit the intended use.

Examples of the nonconductive compound include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoro (PVdF-HFP), dodecyltrimethoxysilane (DMSO), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer At least one selected from silbenzenesulfonic acid and sorbitol can be used.

For example, the polymer represented by Formula 2 may be sPAES (sulfonated poly (arylene ether sulfone)), and the polymer represented by Formula 3 may be PEEK (polyether ether letone).

The electrolyte membrane according to one embodiment may contain components other than the above-mentioned components in order to assist the hydrogen ion conduction. These other components include, for example, plasticizers, polyethers, and the like. Specific examples thereof include those having hydrogen ion conductivity and are not particularly limited as long as they are generally known. Examples of the plasticizer include dioctyl phthalate and the like, and examples of the polyether include polyethylene glycol and the like.

According to another aspect of the present invention, there is provided a method of manufacturing an electrolyte membrane, comprising: preparing a tetravalent metal oxide (M ¹ ) oxide; Mixing the oxidized tetravalent metal element oxide with a trivalent metal oxide (M ² ) oxide to obtain a mixture; Adding a phosphoric acid (H ₃ PO ₄₎ to the mixture; Heat-treating the phosphoric acid-added mixture to prepare an inorganic ion conductor represented by Formula 1 below; Preparing a composition for forming an electrolyte membrane by adding the inorganic ion conductor and a polymer represented by the following formula 2 or 3 to a solvent; And casting and drying the composition for forming an electrolyte film on a substrate.

[Chemical Formula 1]

M ¹ _{1 - a} M ² _a P _x O _y

In Formula 1,

M ¹ is a tetravalent metal element,

M ² is a trivalent metal element,

0? A <1, 1.5? X? 3.5, 5? Y? 13,

(2)

In Formula 2,

L ¹ to L ⁴ are each independently a single bond, -C (= O) - a, -, -O-, -S-, -S (= O) - or -S (= O) ₂

m1 and m2 are each independently an integer of 0 to 100, provided that m1 + m2 is not 0,

(3)

In Formula 3,

L ⁵ to L ⁷ are each independently a single bond, -C (= O) -, -O-, -S-, -S (= O) - or -S (= O) ₂ -, and

n is an integer of 1 to 100;

For example, in Formula 2, each of L ¹ to L ⁴ may independently be a single bond, -O- or -S (= O) ₂ -.

For example, in Formula 3, each of L ⁵ to L ⁷ may independently be -C (= O) - or -O-.

Doping in which the site of the tetravalent metal element is substituted with the site of the metal element having a lower oxidation number can be caused by adding the metal element oxide having the trivalent oxidation number to the tetravalent metal element oxide having the oxidation number.

By doping with a metal element with a low oxidation potential, defects are created in the solid, which in turn reacts with water vapor to introduce hydrogen ions into the solid, resulting in an increase in solid hydrogen ion concentration. Since the ionic conductivity is determined by the mobility and concentration of the ions, the ionic conductivity of the inorganic ionic conductor can be further improved by doping with a metal element having a low oxidation number as described above.

The heat treatment may be performed at 200 ° C to 500 ° C for 1 hour to 5 hours.

By heat-treating the mixture of the oxidized tetravalent metal element oxide, the trivalent metal element oxide and the phosphoric acid at 200 ° C to 300 ° C, pores originally present in the tetravalent metal element oxide are grown in various sizes, More pores can be formed, which are conduction paths of ions.

If the heat treatment temperature is less than 200 ° C, the desired ion conductivity can not be achieved because the composition of the inorganic ion conductor is not synthesized (solid phase reaction), and if the heat treatment temperature exceeds 500 ° C, A porous inorganic ion conductor can not be produced.

For example, the heat treatment temperature may be specifically 250 ° C. to 300 ° C., and the heat treatment time may be 2 hours to 3 hours, but is not limited thereto.

For example, the oxidized metal element oxide may be porous, and in this case, the inorganic ion conductor may be a porous inorganic ion conductor. In this case, the average diameter of the pores in the porous inorganic ion conductor may be 2 nm to 100 nm, for example, 2 nm to 50 nm.

The step of preparing the oxidized tetravalent metal element oxide comprises mixing an anionic surfactant and a cation salt of the tetravalent metal oxide element with a cationic salt to prepare a mixture; Adjusting the pH of the mixture to prepare a suspension solution; And filtering the suspension solution, and then removing the anionic surfactant.

The oxidized tetravalent metal element oxide, which is the porous structure thus formed, may have an average diameter of pores of 3 nm to 30 nm.

A plurality of pores formed in the tetravalent metal oxide of oxide having the porous structure are formed in a plurality of sizes and in a plurality of sizes by performing the heat treatment step performed after mixing with the trivalent metal oxide oxide and phosphoric acid, Can be formed into a porous inorganic ion conductor according to an embodiment of the present invention, by being formed into a porous body having a diameter of 2 nm to 100 nm, for example, 2 nm to 50 nm.

The above polymer is as described above.

The solvent may include, but is not limited to, dimethylacetamide, dimethylformamide, tetrahydrofuran, N-methylpyrrolidone, or combinations thereof.

In the step of casting and drying the composition for forming an electrolyte film on a substrate, the substrate may be a glass substrate, but is not limited thereto. The drying may be carried out in a vacuum atmosphere at 50 ° C to 150 ° C, for example, 60 ° C to 100 ° C for 9 hours to 15 hours, for example, 10 hours to 14 hours, but is not limited thereto.

Another embodiment provides a fuel cell comprising the electrolyte membrane.

For example, the fuel cell may be a polymer electrolyte fuel cell (PEMFC).

Hereinafter, a membrane electrode assembly according to another embodiment and a fuel cell employing the membrane electrode assembly will be described in detail.

First, the fuel cell has a structure in which a membrane electrode assembly is sandwiched by a separator, and is a cell that can operate even under high temperature and humidified conditions of 150 ° C or higher. Wherein the membrane electrode assembly includes a fuel electrode; Oxygen pole; And an electrolyte membrane sandwiched between the fuel electrode and the oxygen electrode.

The electrolyte membrane is as described above.

Hereinafter, each component of the membrane electrode assembly will be described in detail.

First, a fuel cell according to one embodiment will be described with reference to FIG. 1, and the membrane electrode assembly will be described with reference to FIG.

1 is an exploded perspective view showing a fuel cell according to an embodiment of the present invention,

2 is a schematic cross-sectional view of a membrane electrode assembly (MEA) constituting the fuel cell of FIG.

The fuel cell 100 shown in Fig. 1 has one unit cell 10 sandwiched between a pair of holders 30 and 30. The unit cell 10 is composed of a membrane electrode assembly 20 and bipolar plates 13 and 15 arranged on both sides in the thickness direction of the membrane electrode assembly 20. The bipolar plates 13 and 15 are made of a conductive metal or carbon and are bonded to the membrane electrode assembly 20 to function as a current collector and to form a membrane electrode assembly And fuel.

1, the number of unit cells 10 is one, but the number of unit cells is not limited to one, and may be increased to several tens to several hundreds depending on characteristics required for a fuel cell .

2, the membrane electrode assembly 20 includes an electrolyte membrane 21, an anode electrode 26 disposed on one surface of the electrolyte membrane 21 and including an anode gas diffusion layer 28, And a cathode electrode 27 including a cathode gas diffusion layer 25 located on one surface.

More specifically, the anode electrode (also referred to as "anode") is supplied with hydrogen gas from the outside through the diffusion layer of the anode in the fuel electrode,

As the electrode catalyst in the anode, platinum or platinum ruthenium catalyst is usually used, and the catalyst is supported on a carbon-based carrier such as carbon black.

[Reaction Scheme 1]

H ₂ ? 2H ⁺ + 2e

The hydrogen ions generated by the electrode reaction pass through the electrolyte membrane and move to the oxygen electrode. On the other hand, the electrons reach the oxygen electrode through the external circuit. And this current is taken out as electric power.

The cathode electrode (also referred to as "air electrode") is composed of a catalyst layer including an electrode catalyst and a gas diffusion layer. More specifically, at the oxygen electrode, the electrode reaction of the following reaction formula 2 proceeds.

As the electrode catalyst in the oxygen electrode, a platinum catalyst is usually used, and this catalyst is supported on a carbon-based carrier such as carbon black.

[Reaction Scheme 2]

1/2 O ₂ + 2H ⁺ + 2e H ₂ O

In the oxygen electrode, water molecules are generated on the catalyst by reacting hydrogen ions that have moved through the electrolyte and the electrons that have reached through the external circuit through the above reaction, and molecules introduced through the diffusion layer of the oxygen electrode from the outside.

Next, a method of manufacturing a fuel cell according to an embodiment having the above-described configuration will be described in detail below.

The fuel cell may be manufactured by first manufacturing a fuel electrode, an oxygen electrode, and an electrolyte membrane, fabricating a membrane electrode assembly using the membrane electrode assembly, and then using the membrane electrode assembly. Hereinafter, each step will be described in order.

The fuel electrode (anode) and the oxygen electrode (cathode) may be electrode layers that are in contact with the gas supplied when the fuel cell operates, and those produced by known techniques can be used.

Next, a membrane electrode assembly is manufactured using each of the electrodes and the electrolyte membrane fabricated as described above. As a method of producing a membrane electrode assembly, an electrolyte membrane may be sandwiched between a fuel electrode and an oxygen electrode. Specifically, for example, in the case of a solid polymer type fuel cell (PEFC), both sides of the electrolyte membrane obtained as described above are sandwiched by a catalyst layer as an electrode, and further a gas diffusion layer is provided and these are integrated to produce a membrane electrode assembly . Further, for the purpose of enhancing the adhesion between the electrode and the electrolyte membrane, the membrane electrode assembly can be pressed under pressure in the direction of the membrane surface.

In addition, the fuel cell according to one embodiment can be manufactured by a known method using the membrane electrode assembly obtained as described above. That is, the fuel cell stack can be manufactured by forming unit cells by interposing the both sides of the membrane electrode assembly obtained as described above with a separator such as a metal separator and arranging a plurality of unit cells.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the following examples and comparative examples are for illustrative purposes only and are not intended to limit the present invention.

( Example )

Example  1: Porous inorganic conductor Electrolyte membrane

(Preparation of Porous Sn _{0 .95} Al _{0 .05} O _{1 .975} Powder)

SDS (sodium dodecyl sulfate) was dissolved in deionized water such that about 2.5 wt%, and the molar ratio of the SDS and the metal salt _{(Na 2 SnO 3 · 3H 2} O, NaAlO 2) (Waco Chemicals) 1: Na so that the three ₂ SnO ₃ .3H ₂ O and NaAlO ₂ were added, followed by stirring at room temperature. The Na ₂ SnO ₃ · 3H ₂ O and NaAlO ₂ Is added such that the molar ratio is 0.95: 0.05.

To this solution was added a 36% hydrochloric acid solution and the pH of the solution was gradually lowered to 10, 8, 6, 4, and 2 while maintaining a holding time of 60 minutes per each pH to obtain a white suspension solution.

This was stirred at room temperature for 2 hours, and the formed solid product was filtered, washed with ethanol and dried to obtain a solid powder.

The solid powder was added to a mixed solution of ammonia water and ethanol and stirred at room temperature for 1 to 2 days. The formed solid product was filtered, washed with ethanol, and dried to obtain a porous Sn _{0 .95} Al _{0 .05} O _{1 .975} to obtain a powder.

(Preparation of porous inorganic ion conductor powder)

Sn _{0 .95} Al _{0 .05} O _{1 .975} and H ₃ PO ₄ obtained above were mixed so that the molar ratio of Sn and P was 1: 2, distilled water was added thereto to obtain a mixture, Followed by stirring and heat treatment to obtain a high-viscosity mixed paste.

The paste was transferred to a ceramic crucible and heat-treated at 250 ° C for 2.5 hours.

Then, the ground to cause a mass obtained after the above-described heat treatment to obtain a _{Sn 0 .95 Al 0 .05 P 2} O 7 in a powder state.

(Preparation of electrolyte membrane)

15% by weight of Sn _{0 .95} Al _{0 .05} P ₂ O ₇ and 85% by weight of a polymer represented by the following formula (2-1) were dissolved in dimethylacetamide (DMAc) Thereby preparing a composition for forming an electrolyte membrane.

The electrolyte membrane forming composition was ground and mixed in a ball mill, cast on a glass substrate, dried at 70 캜 for 12 hours in a vacuum atmosphere, and the membrane was separated from the glass substrate to prepare an electrolyte membrane.

[Formula 2-1]

(In the above formula (2-1)

a = 50, b = 50, weight average molecular weight = 130,000 g / mol).

Example  2: Porous inorganic oxide Electrolyte membrane

An electrolyte membrane was prepared in the same manner as in Example 1 except that the phosphoric acid (H ₃ PO ₄ ) mixing and the heat treatment were not performed.

Example  3: Non-porous  Inorganic conductor Electrolyte membrane

Commercially available non-porous SnO ₂ (Nanotek) was prepared,

An electrolyte membrane was prepared in the same manner as in Example 1 except that SnO ₂ was used and the phosphoric acid mixture was heat-treated at 500 ° C.

Comparative Example  One

The polymer represented by Formula 2-1 was used as an electrolyte membrane.

(evaluation)

Evaluation example  1: Measurement of ionic conductivity

The ionic conductivity of the electrolyte membrane prepared according to Example 1, Example 2, and Comparative Example 1 was measured and shown in FIG.

The conductivities of the electrolyte membranes prepared according to Examples 1 and 2 and Comparative Example 1 were measured using a Bekktec apparatus at 4 ° C under a hydrogen (H ₂ ) (flow rate: 500 SCCM) Probe-In Plane) method.

The results of the ionic conductivity evaluation are shown in Fig.

3 is a graph showing ion conductivity measured under humidifying conditions.

Referring to FIG. 3, it can be seen that the ionic conductivity of the electrolyte membrane according to Example 1 and Example 2 is superior to the ionic conductivity of the electrolyte membrane according to Comparative Example 1 under humidifying conditions. The composite electrolyte membrane including the porous inorganic material exhibits better ionic conductivity than the electrolyte membrane composed only of the polymer.

It is also understood that the electrolyte membrane according to Example 1 is superior in ion conductivity as compared with the ion conductivity of the electrolyte membrane according to Example 2. This indicates that the composite electrolyte membrane including the porous inorganic hydrogen ion conductor exhibits better ion conductivity than the composite electrolyte membrane containing the porous inorganic oxide.

It can be said that this is due to the effect of humidifying the membrane according to the content of the porous inorganic material and the effect of improving the conductivity by the dispersion of the inorganic hydrogen ion conductor.

Evaluation example  2: Evaluation of adsorption / desorption of nitrogen

The pore size distribution of the pores was measured by N ₂ adsorption-desorption isotherms and the Specific Brunauer-Emmett-Teller (BET) was calculated.

N ₂ adsorption-desorption isotherms were measured as a method of measuring the change in the amount of adsorption / desorption according to the relative pressure (P / P ₀ ) of nitrogen (N ₂ ) at a liquid nitrogen temperature of 77.3 K Respectively.

4 is a nitrogen adsorption / desorption isotherm graph of the porous electrolyte membrane according to Example 1. Fig.

Referring to FIG. 4, it can be seen that the pore diameter ranges from 2 nm to 100 nm.

The BET surface area was calculated in the adsorption region with a relative pressure (P / P ₀ ) of 0.05 to 0.20. The pore diameter distribution was calculated from the adsorption area curve (full range) by the Barrett-Joyner-Halenda (BJH) method and the results are shown in FIG.

5 is a graph showing the results of measurement of the specific surface area with respect to the porous inorganic electroconductive film (Example 1) and the non-porous inorganic electroconductive film (Example 3) according to the heat treatment temperature.

Referring to FIG. 5, it can be seen that when the porous SnO ₂ is used at a temperature within the range of 250 ° C. to 500 ° C. and below 300 ° C., more specifically around 250 ° C., the highest specific surface area is exhibited .

From this, it can be seen that when porous SnO ₂ is mixed with phosphoric acid and then heat-treated at 300 ° C or lower, it exhibits excellent porosity.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, And it goes without saying that the invention belongs to the scope of the invention.

100: Fuel cell
10: Unit cell
20: membrane electrode assembly
13, 15: bipolar plate
30: Holder
21: electrolyte membrane
23: cathode catalyst layer
24: anode catalyst layer
25: cathode gas diffusion layer
26: anode electrode
27: cathode electrode
28: anode gas diffusion layer

Claims (20)

An inorganic ion conductor represented by the following formula (1)
A polymer represented by the following formula (2) or (3)
An electrolyte membrane comprising:
[Chemical Formula 1]
M ¹ _{1 - a} M ² _a P _x O _y
In Formula 1,
M ¹ is a tetravalent metal element,
M ² is a monovalent metal element, a divalent metal element or a trivalent metal element,
0? A <1, 1.5? X? 3.5, 5? Y? 13,
(2)

In Formula 2,
L ¹ to L ⁴ are each independently a single bond, -C (= O) - a, -, -O-, -S-, -S (= O) - or -S (= O) ₂
m1 and m2 are each independently an integer of 0 to 100, provided that m1 + m2 is not 0,
(3)

In Formula 3,
L ⁵ to L ⁷ are each independently a single bond, -C (= O) -, -O-, -S-, -S (= O) - or -S (= O) ₂ -, and
n is an integer of 1 to 100;
The method according to claim 1,
Wherein M &lt; ^{2 &gt;} is a trivalent metal element.
The method according to claim 1,
Wherein M ² is Al, Fe, Ga, Y, In, Sb, Bi, La, Nd or Sm.
The method according to claim 1,
Wherein M ¹ is Sn, Zr, Ti, Ce or Si.
The method according to claim 1,
X is an integer of 2,
And y is an integer of 7.
The method according to claim 1,
Wherein the inorganic ion conductor has a specific surface area of 4.0 m ² / g to 90.0 m ² / g.
The method according to claim 1,
Wherein the electrolyte membrane has a ratio of the total amount of the electrolyte membrane to the total amount of the electrolyte membrane,
5% to 30% by weight of the inorganic ion conductor represented by the formula (1)
70% by weight to 95% by weight of the polymer,
&Lt; / RTI &gt;
The method according to claim 1,
Wherein the inorganic ion conductor is a porous inorganic ion conductor.
9. The method of claim 8,
Wherein an average diameter of the pores in the porous inorganic ion conductor is 2 nm to 100 nm.
9. The method of claim 8,
Wherein an average diameter of the pores in the porous inorganic ion conductor is 2 nm to 50 nm.
The method according to claim 1,
Wherein the polymer has a weight average molecular weight of 10,000 g / mol to 500,000 g / mol.
Preparing a tetravalent metal oxide (M ¹ ) oxide;
Mixing the oxidized tetravalent metal element oxide with a trivalent metal oxide (M ² ) oxide to obtain a mixture;
Adding a phosphoric acid (H ₃ PO ₄₎ to the mixture;
Heat-treating the phosphoric acid-added mixture to produce an inorganic ion conductor represented by Formula 1 below;
Preparing a composition for forming an electrolyte membrane by adding the inorganic ion conductor and a polymer represented by Formula 2 or 3 below to a solvent; And
Casting the composition for forming an electrolyte membrane on a substrate and drying
A method for producing an electrolyte membrane comprising:
[Chemical Formula 1]
M ¹ _{1 - a} M ² _a P _x O _y
In Formula 1,
M ¹ is a tetravalent metal element,
M ² is a trivalent metal element,
0? A <1, 1.5? X? 3.5, 5? Y? 13,
(2)

In Formula 2,
L ¹ to L ⁴ are each independently a single bond, -C (= O) - a, -, -O-, -S-, -S (= O) - or -S (= O) ₂
m1 and m2 are each independently an integer of 0 to 100, provided that m1 + m2 is not 0,
(3)

In Formula 3,
L ⁵ to L ⁷ are each independently a single bond, -C (= O) -, -O-, -S-, -S (= O) - or -S (= O) ₂ -, and
n is an integer of 1 to 100;
13. The method of claim 12,
Wherein the heat treatment is performed at 200 ° C to 500 ° C for 1 hour to 5 hours.
13. The method of claim 12,
Wherein the step of preparing the tetravalent metal oxide oxide comprises:
Preparing an admixture by mixing an anionic surfactant and a cationic salt of the above-described tetravalent metal element oxide;
Adjusting the pH of the mixture to prepare a suspension solution; And
Filtering the suspension solution, and then removing the anionic surfactant
Wherein the electrolyte membrane is made of a metal.
13. The method of claim 12,
Wherein the inorganic ion conductor is a porous inorganic ion conductor.
16. The method of claim 15,
Wherein an average diameter of pores in the porous inorganic ion conductor is 2 nm to 100 nm.
13. The method of claim 12,
Wherein the polymer has a weight average molecular weight of 10,000 g / mol to 500,000 g / mol.
13. The method of claim 12,
Wherein the solvent comprises dimethylacetamide, dimethylformamide, tetrahydrofuran, N-methylpyrrolidone or a combination thereof.
12. A fuel cell comprising an electrolyte membrane according to any one of claims 1 to 11.
20. The method of claim 19,
Wherein the fuel cell is a polymer electrolyte fuel cell (PEMFC).

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