KR102387430B1 - Electrolyte membrane, preparing the same and fuel cell including the same - Google Patents

Abstract

[화학식 3]

(상기 화학식 1 내지 화학식 3에 대한 설명은 명세서에 정의된 바와 같다.)An electrolyte membrane comprising an inorganic ion conductor represented by the following Chemical Formula 1 and a polymer represented by the following Chemical Formula 2 or Chemical Formula 3, a manufacturing method thereof, and a fuel cell including the same are provided.
[Formula 1]
M ¹ _{1 - a} M ² _a P _x O _y
[Formula 2]

[Formula 3]

(The description of Formulas 1 to 3 is as defined in the specification.)

Description

Electrolyte membrane, manufacturing method thereof, and fuel cell including same

It relates to an electrolyte membrane, a method for manufacturing the same, and a fuel cell including the same.

Recently, research on fuel cells as a fuel source for pollution-free vehicles, which is one of new and renewable energy-related studies, has been attracting attention. Among them, Polymer Electrolyte Membrane Fuel Cell (PEMFC) is attracting great attention as a replacement for existing automobile engines due to its high energy efficiency, output characteristics, and eco-friendly characteristics.

In particular, compared to PEMFCs operating at low temperatures, PEMFCs operating at a high temperature of 100° C. or higher and without humidification do not use a humidifier, so it is known that the control of water management is simple and the system reliability is high. In addition, since the resistance to carbon monoxide (CO) poisoning in the anode increases through high-temperature operation, the impurity content standard of the fuel can be relaxed and the reformer can also be simplified, thereby increasing interest in a high-temperature non-humidifying system.

Fluorine-based polymer electrolyte membranes (such as Nafion, etc.) currently used in general PEMFCs have a problem in that they are difficult to operate at high temperatures due to rapid increase in resistance due to dehydration when used at high temperature and low humidity. There is a need to develop an electrolyte membrane for fuel cells with chemical properties and high ionic conductivity.

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

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

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

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

[Formula 1]

M ¹ _{1 - a} M ² _a P _x O _y

In Formula 1,

M ¹ is a metal element having a tetravalent oxidation number,

M ² is a metal element having a monovalent oxidation number, a metal element having an oxidation number divalent, or a metal element having an oxidation number trivalent,

0 ≤ a < 1, 1.5 ≤ x ≤ 3.5, 5 ≤ y ≤ 13,

[Formula 2]

In Formula 2,

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

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

[Formula 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 -,

n is an integer from 1 to 100;

The M ² may be a metal element having a trivalent oxidation number.

M ² is aluminum (Al), iron (Fe), gallium (Ga), yttrium (Y), indium (In), antimony (Sb), bismuth (Bi), lanthanum (La), neodymium (Nd) or samarium (Sm).

M ¹ may be tin (Sn), zirconium (Zr), titanium (Ti), cerium (Ce), or silicon (Si).

The 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 wt% to 30 wt% of the inorganic ion conductor represented by Chemical Formula 1 and 70 wt% to 95 wt% of the polymer with respect to 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 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 includes the steps of preparing an oxide of a tetravalent metal element (M ¹ ); obtaining a mixture by mixing the oxide of a metal element having an oxidation number of tetravalent and an oxide of a metal element having an oxidation number of trivalent (M ² ); adding phosphoric acid (H ₃ PO ₄ ) to the mixture; preparing an inorganic ion conductor represented by the following Chemical Formula 1 by heat-treating the phosphoric acid-added mixture; preparing a composition for forming an electrolyte membrane by adding the inorganic ion conductor and a polymer represented by Formula 2 or Formula 3 to a solvent; and casting the composition for forming an electrolyte membrane on a substrate and drying the composition.

[Formula 1]

M ¹ _{1 - a} M ² _a P _x O _y

In Formula 1,

M ¹ is a metal element having a tetravalent oxidation number,

M ² is a metal element having a trivalent oxidation number,

0 ≤ a < 1, 1.5 ≤ x ≤ 3.5, 5 ≤ y ≤ 13,

[Formula 2]

In Formula 2,

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

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

[Formula 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 -,

n is an integer from 1 to 100;

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

The preparing of the elemental metal oxide having an oxidation number of tetravalent may include preparing a mixture by mixing an anionic surfactant and a cationic salt of the elemental oxide of the oxidation number of tetravalent; preparing a suspension solution by adjusting the pH of the mixture; and after filtering the suspension solution, 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 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 including the electrolyte membrane.

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

The specific details of other embodiments of the invention are included in the detailed description below.

An electrolyte membrane for a fuel cell having high ionic conductivity can be provided by applying an inorganic ion conductor with improved specific surface area and ion conductivity together with a polymer.

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 the hydrogen ion conductivity of the electrolyte membranes according to Examples 1, 2 and Comparative Example 1.
4 is a nitrogen adsorption/desorption isotherm graph of the porous electrolyte membrane according to Example 1. FIG.
5 is a graph showing the measurement results 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, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

Unless otherwise specified in the specification, when a part such as a layer, film, region, plate, etc. is "on" another part, it is not only when the other part is "directly on" but also when there is another part in the middle. include

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

[Formula 1]

M ¹ _{1 - a} M ² _a P _x O _y

In Formula 1,

M ¹ is a metal element having a tetravalent oxidation number,

M ² is a metal element having a monovalent oxidation number, a metal element having an oxidation number divalent, or a metal element having an oxidation number trivalent,

0 ≤ a < 1, 1.5 ≤ x ≤ 3.5, 5 ≤ y ≤ 13,

[Formula 2]

In Formula 2,

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

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

[Formula 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 -,

n is an integer from 1 to 100;

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

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

The inorganic ion conductor may have a cubic or pseudo-cubic crystal structure. Herein, the term "pseudocube" refers to a rhombohedral structure that is almost similar to a cubic structure. Such a crystal structure can be confirmed by analyzing the interplanar distance obtained through an X-ray diffraction experiment.

Specifically, in the inorganic ion conductor, a metal oxide having a tetravalent oxidation number forms a face-centered cubic structure and is positioned at the corner and face-centered portion, and a phosphate group (P ₂ O ₇ ) is positioned in the edge region to bond with the metal oxide. has

In addition, the inorganic ion conductor may be porous including a plurality of 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 pores in the porous inorganic ion conductor may be 2 nm to 100 nm, such as 2 nm to 50 nm. By forming the inorganic ion conductor in a porous structure, the ionic conductivity of the inorganic ion conductor may be improved by adding a water-containing property under no humidification or low humidity (<50% RH, for example, <30% RH) conditions.

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 becomes possible to achieve hydrogen ion conductivity of 0.01 S/cm to 0.1 S/cm at 75° C. to 200° C. and <30% RH, thereby improving the performance of the electrolyte membrane for fuel cells. can be expected

The M ² is a trivalent metal element, for example, aluminum (Al), iron (Fe), gallium (Ga), yttrium (Y), indium (In), antimony (Sb), bismuth (Bi), lanthanum (La) , may be any one selected from the group consisting of neodymium (Nd) and samarium (Sm).

M ¹ may be, for example, 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 is 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 is not limited thereto.

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

When the content of the inorganic ion conductor represented by Formula 1 is less than 5% by weight, the conductivity-improving effect cannot be achieved due to a decrease in the ion conduction pass and moisture-containing effect under low humidity conditions, and when it exceeds 30% by weight, inorganic There are disadvantages in that the dispersibility of 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 including a repeating unit represented by Formula 2-a and a repeating unit represented by Formula 2-b.

[Formula 2-a]

[Formula 2-b]

In Formula 2-a and Formula 2-b,

L ¹ to L ⁴ are each independently 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 including a repeating unit represented by Formula 3-a below.

[Formula 3-a]

In Formula 3-a,

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

For example, the polymer may be an ionomer to improve adhesion of the catalyst layer and transfer hydrogen ions.

The ionomer may use a polymer resin having hydrogen ion conductivity, and 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, and derivatives thereof in the side chain. can be used More specifically, fluorine-based polymer, benzimidazole-based polymer, polyimide-based polymer, polyetherimide-based polymer, polyphenylene sulfide-based polymer, polysulfone-based polymer, polyethersulfone-based polymer, polyether ketone-based polymer, poly At least one polymer resin selected from an ether-ether ketone-based polymer and a polyphenylquinoxaline-based polymer may be used. More specifically, poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, sulfided polyether ketone, aryl ketone, poly( 2,2'-m-phenylene)-5,5'-bibenzimidazole [poly(2,2'-m-phenylene)-5,5'-bibenzimidazole] and poly(2,5-benzimidazole) ) may be used at least one polymer resin selected from.

The ionomer may be used in the form of a single substance or a mixture, and may optionally be used together with a non-conductive compound in order to further improve adhesion to the polymer electrolyte membrane. The amount of the non-conductive compound is preferably adjusted to suit the purpose of use.

The non-conductive compound includes polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), ethylene/tetrafluoro ethylene/tetrafluoroethylene (ETFE), ethylene chlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), dode At least one selected from silbenzenesulfonic acid and sorbitol may be used.

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

In the electrolyte membrane according to an embodiment, components other than those described above may be included to assist in hydrogen ion conduction. Such other components include, for example, plasticizers, polyethers, and the like. Specific examples of these are 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 polyether includes polyethylene glycol.

A method of manufacturing an electrolyte membrane according to another embodiment includes the steps of preparing an oxide of a metal element having a tetravalent oxidation number (M ¹ ); obtaining a mixture by mixing the oxide of a metal element having an oxidation number of tetravalent and an oxide of a metal element having an oxidation number of trivalent (M ² ); adding phosphoric acid (H ₃ PO ₄ ) to the mixture; preparing an inorganic ion conductor represented by the following Chemical Formula 1 by heat-treating the phosphoric acid-added mixture; preparing a composition for forming an electrolyte membrane by adding the inorganic ion conductor and a polymer represented by Formula 2 or Formula 3 to a solvent; and casting the composition for forming an electrolyte film on a substrate and drying the composition.

[Formula 1]

M ¹ _{1 - a} M ² _a P _x O _y

In Formula 1,

M ¹ is a metal element having a tetravalent oxidation number,

M ² is a metal element having a trivalent oxidation number,

0 ≤ a < 1, 1.5 ≤ x ≤ 3.5, 5 ≤ y ≤ 13,

[Formula 2]

In Formula 2,

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

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

[Formula 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 -,

n is an integer from 1 to 100;

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

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

By adding the metal element oxide having the oxidation number of trivalent to the metal element oxide having the oxidation number of tetravalent, doping may occur in which the site of the metal element having the oxidation number of tetravalent is replaced with the site of the element of the metal having the lower oxidation number.

By doping with a metal element having a low oxidation number, defects are created in the solid, and this bonding introduces hydrogen ions into the solid by reaction with water vapor, and consequently increases the hydrogen ion concentration in the solid. Since ionic conductivity is determined by ion mobility and concentration, the ionic conductivity of the inorganic ion 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 a mixture of an elemental metal oxide having a tetravalent oxidation number, an elemental metal oxide having an oxidation number trivalent, and phosphoric acid at 200° C. to 300° C., the pores originally present in the metal element oxide having a tetravalent oxidation number are grown in various sizes and in a number of hydrogen More pores serving as conduction paths of ions may be formed.

When the heat treatment temperature is less than 200 ° C, the composition of the inorganic ion conductor is not synthesized (solid phase reaction), the desired ionic conductivity cannot be achieved, and when the heat treatment temperature exceeds 500 ° C, the pores are collapsed , so that a porous inorganic ion conductor cannot be produced.

For example, the heat treatment temperature may specifically be 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 tetravalent 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 preparing of the elemental metal oxide having an oxidation number of tetravalent may include preparing a mixture by mixing an anionic surfactant and a cationic salt of the elemental oxide of the oxidation number of tetravalent; preparing a suspension solution by adjusting the pH of the mixture; and after filtering the suspension solution, removing the anionic surfactant.

In the porous structure formed in this way, the tetravalent metal element oxide may have an average pore diameter of 3 nm to 30 nm.

A plurality of pores formed in the porous structure of the metal element oxide having a tetravalent oxidation number are formed in more various sizes and in a plurality by passing a heat treatment step performed after mixing with a trivalent metal element oxide and phosphoric acid, and the average of pores By forming a porosity of 2 nm to 100 nm in diameter, such as 2 nm to 50 nm, the porous inorganic ion conductor according to an embodiment of the present invention can be prepared.

The polymer is the same as described above.

The solvent may include, but is not limited to, dimethylacetamide, dimethylformamide, tetrahydrofuran, N-methylpyrrolidone, or a combination 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. In addition, the drying may be performed 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 including 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 battery capable of operating at a high temperature of 150° C. or more and in no humidification conditions. The membrane electrode assembly may include an anode; oxygen electrode; An electrolyte membrane interposed between the fuel electrode and the oxygen electrode is provided.

The electrolyte membrane is the same as described above.

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

First, a fuel cell according to an exemplary embodiment will be described with reference to FIG. 1 , and the membrane electrode assembly will be described with reference to FIG. 2 .

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

FIG. 2 is a schematic cross-sectional view of a membrane electrode assembly (MEA) constituting the fuel cell of FIG. 1 .

In the fuel cell 100 shown in FIG. 1 , one unit cell 10 is sandwiched by a pair of holders 30 and 30 . The unit cell 10 includes a membrane electrode assembly 20 and bipolar plates 13 and 15 disposed on both sides of the membrane electrode assembly 20 in the thickness direction. The bipolar plates 13 and 15 are made of conductive metal, carbon, or the like, and by bonding to the membrane electrode assembly 20 respectively, function as a current collector and provide oxygen to the catalyst layer of the membrane electrode assembly 20 . and supply fuel.

In addition, in the fuel cell 100 shown in FIG. 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 the fuel cell. .

As shown in FIG. 2, the membrane electrode assembly 20 is an electrolyte membrane 21, an anode electrode 26 positioned on one surface of the electrolyte membrane 21 and including an anode gas diffusion layer 28, and the other of the electrolyte membrane. It has a structure including a cathode electrode 27 including a cathode gas diffusion layer 25 positioned on one surface.

The anode electrode (also referred to as “anode”) is more specifically, in the anode, hydrogen gas is supplied from the outside through the diffusion layer of the anode, and the electrode reaction of Reaction Formula 1 below proceeds.

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

[Scheme 1]

H ₂ → 2H ⁺ + 2e

Hydrogen ions generated by the electrode reaction pass through the electrolyte membrane and move to the oxygen electrode. On the other hand, electrons pass through an external circuit to reach the oxygen electrode. This current is taken out as electric power to the outside.

The cathode electrode (also referred to as “cathode”) includes a catalyst layer containing an electrode catalyst and a gas diffusion layer. More specifically, in the oxygen electrode, the electrode reaction of Reaction Formula 2 proceeds.

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

[Scheme 2]

1/2 O ₂ + 2H ⁺ + 2e → H ₂ O

In the oxygen electrode, electrons arriving through the external circuit by the reaction, hydrogen ions that have migrated through the electrolyte membrane, and molecules introduced from the outside through the diffusion layer of the oxygen electrode react on the catalyst to generate water.

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

The fuel cell can be manufactured by first manufacturing an anode, an oxygen electrode, and an electrolyte membrane, and then using the membrane electrode assembly to manufacture a membrane electrode assembly. Hereinafter, each process is demonstrated in turn.

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

Next, a membrane electrode assembly is manufactured using each electrode and electrolyte membrane prepared as described above. As a method of manufacturing the membrane electrode assembly, the electrolyte membrane may be sandwiched between the fuel electrode and the oxygen electrode. Specifically, for example, in the case of a solid polymer fuel cell (PEFC), both sides of the electrolyte membrane obtained as described above are interposed as catalyst layers as electrodes, and a gas diffusion layer is further provided to integrate them to produce a membrane electrode assembly. . In addition, for the purpose of increasing the adhesion between the electrode and the electrolyte membrane, the pressure may be applied in the direction of the membrane surface of the membrane electrode assembly.

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

Hereinafter, the present invention will be described in more detail through Examples and Comparative Examples, but the following Examples and Comparative Examples are for illustrative purposes 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 0.975} powder)

Sodium dodecyl sulfate (SDS) was dissolved in deionized water to a concentration of about 2.5 wt%, and Na ₂ SnO ₃ .3H ₂ O, NaAlO ₂ ) (Waco Chemicals) was dissolved in deionized water so that the molar ratio was 1:3. ₂ SnO ₃ ·3H ₂ O and NaAlO ₂ were added, followed by stirring at room temperature. At this time, Na ₂ SnO ₃ ·3H ₂ O and NaAlO ₂ is added so that the molar ratio is 0.95:0.05.

By adding a 36% hydrochloric acid solution to the solution, a white suspension solution was obtained while stepwise lowering the pH of the solution to 10, 8, 6, 4, 2 while maintaining a holding time of 60 minutes for each pH.

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 aqueous ammonia and ethanol, stirred at room temperature for 1-2 days, and the formed solid product was filtered, washed with ethanol and dried to remove SDS from porous _{Sn 0.95 Al 0.05} O _1.975 powder _was obtained.

(Preparation of porous inorganic ion conductor powder)

Sn 0.95 Al _{0.05 O 0.975} and H ₃ PO ₄ obtained above are mixed so that the molar ratio of Sn and P is 1: ₂ , _and distilled water is added thereto to obtain a mixture, and the mixture is _heated at about 200° C. was stirred and heat treated 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 mass obtained after the above-described heat treatment was pulverized with a mortar to obtain Sn _0.95 Al _0.05 P _{2 O 7} in _a powder state.

(Production of electrolyte membrane)

_After mixing the Sn _0.95 Al _0.05 P _{2 O 7} 15% by weight and 85% by weight of the polymer represented by the following Chemical Formula 2-1, this was added to dimethylacetamide (DMAc) and dissolved, A composition for forming an electrolyte membrane was prepared.

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

[Formula 2-1]

(In 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 phosphoric acid (H ₃ PO ₄ ) mixing and heat treatment were not carried out.

Example 3: non-porous inorganic conductor electrolyte membrane

Prepare a commercially available non-porous SnO ₂ (Nanotek),

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

comparative example One

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

(evaluation)

evaluation example 1: Measurement of ionic conductivity

The ionic conductivity of the electrolyte membranes prepared according to Examples 1, 2 and Comparative Example 1 was measured and shown in FIG. 3 .

The conductivity of the electrolyte membranes prepared according to Examples 1, 2 and Comparative Example 1 was measured using Bekktec equipment at 90° C. for hydrogen (H ₂ ) (flow rate: 500 SCCM) in 4 probe-in plane ( It is evaluated using the Probe-In Plane method.

The ionic conductivity evaluation result is as shown in FIG. 3 .

3 is a graph showing the ionic conductivity measured in a humidified condition.

Referring to FIG. 3 , it can be seen that the electrolyte membranes according to Examples 1 and 2 have excellent ionic conductivity under humidified conditions as compared to the ionic conductivity of the electrolyte membrane according to Comparative Example 1. The composite electrolyte membrane including the porous inorganic material exhibits better ionic conductivity than the electrolyte membrane made of only polymer.

In addition, it can be seen that the electrolyte membrane according to Example 1 has excellent ionic conductivity compared to the ionic conductivity of the electrolyte membrane according to Example 2. This indicates that the composite electrolyte membrane including the porous inorganic hydrogen ion conductor exhibits superior ionic conductivity than the composite electrolyte membrane including the porous inorganic oxide.

This can be said to be due to the moisture-containing effect in the film due to the inclusion of the porous inorganic material and the effect of improving the conductive properties according to the dispersion of the inorganic hydrogen ion conductor.

evaluation example 2: Evaluation of nitrogen adsorption/desorption

Pore size distribution was measured by nitrogen adsorption/desorption evaluation (N ₂ adsorption-desorption isotherms), and specific surface area (Specific Brunauer-Emmett-Teller (BET)) was calculated.

Figure 4 shows the adsorption/desorption isotherms _of nitrogen 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 shown in

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 diameter of the pores is distributed in the range of 2 nm to 100 nm.

The BET surface area was calculated in the adsorption region of the relative pressure (P/P ₀ ) 0.05 to 0.20. The pore diameter distribution was calculated by the Barrett-Joyner-Halenda (BJH) method from the adsorption area curve (full range), and the results are shown in FIG. 5 .

5 is a graph showing the measurement results of specific surface areas for a porous inorganic conductor electrolyte membrane (Example 1) and a non-porous inorganic conductor electrolyte membrane (Example 3) according to the heat treatment temperature.

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

From this, it can be seen that porous SnO ₂ exhibits excellent porosity when heat-treated at 300° C. or less after mixing with phosphoric acid.

Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and it is possible to carry out various modifications within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and this also It goes without saying that it falls within 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)

delete delete delete delete delete delete delete delete delete delete delete Preparing an oxide of a tetravalent metal element (M ¹ );
obtaining a mixture by mixing the oxide of a metal element having an oxidation number of tetravalent and an oxide of a metal element having an oxidation number of trivalent (M ² );
adding phosphoric acid (H ₃ PO ₄ ) to the mixture;
preparing an inorganic ion conductor represented by the following Chemical Formula 1 by heat-treating the phosphoric acid-added mixture;
preparing a composition for forming an electrolyte membrane by adding the inorganic ion conductor and a polymer represented by Formula 2 or Formula 3 to a solvent; and
Casting the composition for forming an electrolyte film on a substrate and drying the composition
A method of manufacturing an electrolyte membrane comprising:
[Formula 1]
M ¹ _{1 - a} M ² _a P _x O _y
In Formula 1,
M ¹ is a metal element having a tetravalent oxidation number,
M ² is a metal element having a trivalent oxidation number,
0 ≤ a < 1, 1.5 ≤ x ≤ 3.5, 5 ≤ y ≤ 13,
[Formula 2]

In Formula 2,
L ¹ to L ⁴ are each independently a single bond, -C(=O)-, -O-, -S-, -S(=O)-, or -S(=O) ₂ -,
m1 and m2 are each independently an integer from 0 to 100, provided that m1 + m2 is not 0;
[Formula 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 -,
n is an integer from 1 to 100;
13. The method of claim 12,
The heat treatment is a method of manufacturing an electrolyte membrane that is carried out at 200 ° C. to 500 ° C. for 1 hour to 5 hours.
13. The method of claim 12,
The step of preparing the metal element oxide having a tetravalent oxidation number,
preparing a mixture by mixing an anionic surfactant and a cationic salt of an oxide of a tetravalent metal element;
preparing a suspension solution by adjusting the pH of the mixture; and
After filtering the suspension solution, removing the anionic surfactant
A method of manufacturing an electrolyte membrane comprising a.
13. The method of claim 12,
The method for producing an electrolyte membrane wherein the inorganic ion conductor is a porous inorganic ion conductor.
16. The method of claim 15,
A method of manufacturing an electrolyte membrane having an average diameter of pores in the porous inorganic ion conductor of 2 nm to 100 nm.
13. The method of claim 12,
The polymer is a method of manufacturing an electrolyte membrane having a weight average molecular weight of 10,000 g / mol to 500,000 g / mol.
13. The method of claim 12,
The solvent is a method of manufacturing an electrolyte membrane comprising dimethylacetamide, dimethylformamide, tetrahydrofuran, N-methylpyrrolidone, or a combination thereof.
A fuel cell comprising an electrolyte membrane manufactured by the method of any one of claims 12 to 18.
20. The method of claim 19,
The fuel cell is a polymer electrolyte fuel cell (PEMFC).

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