JP2000260442A - Solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the manufacturing cost of a fuel cell and to enhance its manufacturing efficiency. SOLUTION: An electrolyte material is obtained by adding H3PO4 (85%) to plural metal oxide compounds, mixing and stirring them (S11), and the electrolyte is preheated for three hours at a temperature of 500 deg.C (S12). After the electrolyte preheated is fused at a temperature of 1450 deg.C for one hour (S13), it is, cooled (S14) and vitrified to obtain glass, and a solid electrolyte is completed by forming the glass into a desired shape. Glass ceramic produced through a crystallizing process, a grinding process, a forming process and a baking process by using the above glass may be used for the solid electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid oxide fuel cell used for cogeneration and the like.

[0002]

2. Description of the Related Art The principle of operation of a conventionally known solid oxide fuel cell (hereinafter referred to as a fuel cell) will be described with reference to the schematic configuration diagram of FIG. In FIG. 4, a porous oxygen electrode (cathode) 42 and a porous hydrogen electrode (anode) 43 are mounted on both sides of a solid electrolyte 41 having oxygen ion conductivity.
When oxygen gas O ₂ or air flows into the space 45 on the oxygen electrode 42 side, a reaction expressed by the following equation occurs.

_1/2 O ² + 2e ⁻ → O ^2- (1) Reduced oxygen ions O ²⁻ pass through a solid electrolyte 41 having oxygen ion conductivity to reach a hydrogen electrode 43. On the hydrogen electrode 43 side, a fuel gas such as hydrogen gas H ₂ or natural gas flows into the space 46, and the oxygen ion O ^{2 −} passing through the solid electrolyte 41 reacts with the following equation.

H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (2) As shown in FIG. 4, a load 44 is connected to an oxygen electrode 42 and a hydrogen electrode 43.
When connected to the anode, the oxygen electrode 42 side is the anode, and the hydrogen electrode 43
Voltage side becomes the cathode (2) right side of equation 2e ^- by developed across the load 44.

As the electrolyte material of the solid electrolyte 41 used in the fuel cell configured as described above, there are many materials using stabilized zirconia produced by dissolving an oxide such as yttrium in zirconia. The operating temperature of a fuel cell using stabilized zirconia as the electrolyte material is about 1000
Because of the high temperature of ℃, there has been an inconvenience that special materials such as ceramics and heat-resistant alloys, which are expensive in material cost and processing cost, must be used as constituent materials of the fuel cell. Further, in the case of a stack type fuel cell, there is a problem that the material cost and the processing cost are extremely increased due to the large number of constituent members. Therefore, attempts have been made to lower the operating temperature of the fuel cell.

[0006]

Generally, for example, (C
eO ₂ ) _0.8 (SmO _1.5 ) _0.2 (SDC) or (CeO ₂ ) _0.8
There is known a means for forming a solid electrolyte (hereinafter, referred to as a ceria-based solid electrolyte) using an electrolyte material composed of (GdO _1.5 ) _0.2 (GDC) to raise the operating temperature of a fuel cell to 700 to 800 ° C. .

However, there is a problem that the ceria-based solid electrolyte is reduced in a hydrogen atmosphere or the like. In a fuel cell using a ceria-based solid electrolyte,
When operating in a temperature range in which stainless steel can be used as a constituent member, one fuel cell using a solid electrolyte made of stabilized zirconia (zirconia-based solid electrolyte) is used.
Battery characteristics comparable to operating at a temperature of 000 ° C. cannot be obtained.

[0008] As described above, the development of operating temperature of a fuel cell at 700 to 800 ° C using a ceria-based solid electrolyte has been performed. However, components of the fuel cell (interconnector, holding plate, spring, etc.) have been developed. )), There has not been developed a solid electrolyte capable of reliably using stainless steel and operating a fuel cell at an optimum temperature of about 400 to 600 ° C. in cogeneration.

The present invention has been made on the basis of the above-mentioned problems, and has been made to improve an electrolyte material used for a solid electrolyte to reduce the operating temperature of a fuel cell and to improve the processability of the electrolyte material. To provide a solid oxide fuel cell with reduced manufacturing cost.

[0010]

According to the present invention, there is provided a solid electrolyte fuel cell comprising a solid electrolyte having ionic conductivity provided with an oxygen electrode and a hydrogen electrode. Wherein the solid electrolyte is formed by shaping glass containing a Ti group element (Ti, Zr, or Hf element) or an Al element into a desired shape.

[0011] The second invention is the first invention, wherein a glass of TiO ₂ · P ₂ O ₅ based on the solid electrolyte, the molar ratio of TiO ₂ and P ₂ O ₅ in the glass is 64:36 ~
76:24.

According to a third aspect of the present invention, in the first aspect, Al ₂ O ₃ .P ₂ O ₅ glass is used as the solid electrolyte, and a molar ratio of Al ₂ O ₃ to P ₂ O ₅ of the glass is used. Is 60: 40 ~
74:26.

According to a fourth aspect, in the first aspect, a ZrO ₂ · P ₂ O ₅ -based glass is used as the solid electrolyte, and the glass has a molar ratio of ZrO ₂ and P ₂ O ₅ of 64:36. ~
76:24.

According to a fifth aspect of the present invention, in the first aspect, an HfO ₂ · P ₂ O ₅ glass is used as the solid electrolyte, and the molar ratio of HfO ₂ to P ₂ O _{5 in the} glass is 64:36. ~
76:24.

A sixth invention is characterized in that, in the second or third invention, a glass ceramic obtained by crystallizing the glass is used as a solid electrolyte.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, first and second embodiments of the present invention will be described with reference to the drawings. First, in the first embodiment, the solid electrolyte (glass) is formed by adjusting the components of the vitrified electrolyte material (the first to fourth embodiments) to reduce the operating temperature of the fuel cell and to manufacture the solid electrolyte. This is to improve efficiency.

FIG. 1 shows a manufacturing process of a solid electrolyte using glass according to the first embodiment. In FIG. 1, step S11 shows a mixing / stirring process, in which a plurality of metal oxides are mixed with H ₃ PO _4.
(85%), mix and stir to obtain the electrolyte material. The electrolyte material is preheated at a temperature of 500 ° C. for 3 hours in a preheating step shown in step S12. The electrolyte material preheated as described above is used in step S1.
After melting at a temperature of 1450 ° C. for 1 hour in a melting step shown in Step 3, the glass is cooled and vitrified in a cooling step shown in Step S14 to obtain glass, and the glass is formed into a desired shape to complete a solid electrolyte. Let it.

Here, the vitrified electrolyte material will be described with reference to first to fourth embodiments.

(First Embodiment) In general, Na ₂ O.TiO ₂
30P ₂ O ₅ -based glass is known to be a Na ion conductor, and an alkali component (here, Na ₂ O) is contained in the Na ₂ O · TiO ₂ · 30P ₂ O ₅ -based glass. Otherwise, vitrification has been considered difficult. Therefore, the first
In this embodiment, an attempt was made to produce a TiO ₂ .P ₂ O ₅ -based glass (xTiO ₂ .yP ₂ O ₅ -based (x, y; natural number) glass) containing no Na ⁺ , and the TiO ₂ .P ₂ O It was investigated whether it is possible to use the ₅ series glass as a solid electrolyte (proton conductor).

First, the molar ratio of TiO ₂ to P ₂ O ₅ (TiO 2
₂ : P ₂ O ₅ ) was varied to form electrolyte materials A1 to A18, and the electrolyte materials A1 to A18 were vitrified to produce a solid electrolyte. The results are shown in Table 1 below. In Table 1, the circles in Table 1 indicate that vitrification was achieved.
The crosses indicate the case where vitrification could not be performed.

[0021]

[Table 1]

From the results shown in Table 1 above, TiO ₂ : P ₂ O
It can be seen that the electrolyte materials A7 to A13 having _{5 in} the range of 64:36 to 76:24 can be vitrified. As a result of measuring the electric conductivity (ion electric conductivity) of each solid electrolyte using the electrolyte materials A7 to A13 in which TiO ₂ : P ₂ O ₅ is in the range of 64:36 to 76:24, the electric conductivity of each solid electrolyte is substantially the same. The conductivity at a temperature of 600 ° C. was 10 ⁻¹ S / cm. When the conductivity at a temperature of 600 ° C. (10 ⁻¹ S / cm) was compared with the conductivity of a zirconia-based solid electrolyte at a temperature of 1000 ° C., it was confirmed that they were almost equivalent. .

FIG. 2 shows the electrolyte materials A7 to A1.
Electrolyte material A containing 70:30 of TiO ₂ : P ₂ O ₅
FIG. 11 is an Arrhenius plot showing the electrical conductivity (σ) characteristic with respect to temperature in the solid electrolyte using No. 10; As shown in FIG. 2, the solid electrolyte obtained by vitrifying the electrolyte material A10 (curve A in FIG. 2) has substantially the same conductivity as the zirconia-based solid electrolyte (curve B in FIG. 2) at a low temperature. Can be read.

Therefore, when TiO ₂ : P ₂ O ₅ is 64: 36-
A zirconia-based solid electrolyte is formed by using a TiO ₂ · P ₂ O ₅ -based glass within a range of 76:24.
(Curve B in FIG. 2), it is possible to obtain substantially the same conductivity,
It was confirmed that it is possible to configure a fuel cell that operates at a low temperature (600 ° C. or lower).

Second Embodiment Next, an Al ₂ O ₃ .P ₂ O ₅ system in which “Ti” is replaced with “Al” in the TiO ₂ .P ₂ O ₅ system glass shown in the first embodiment. Al ₂ O ₃
Molar ratio of P ₂ O ₅ and _{(Al 2 O 3: P 2} O 5) is formed an electrolyte material B1~B18 while varying, their electrolyte material B1~B18 tried to prepare a vitrified solid electrolyte ,
The results are shown in Table 2 below.

[0026]

[Table 2]

From the results shown in Table 2 above, Al ₂ O ₃ : P ₂
O ₅ is 60: 40-74: 26 electrolyte material B5~B12 that are within the scope of the read that it is possible to vitrification. _{Al 2 O 3: P 2 O} 5 is 60: 40-74: 26 result of measuring the conductivity at each of the solid-state electrolyte with electrolyte material B5~B12 that are within the scope of each substantially comparable conductivity obtained Conductivity at a temperature of 600 ° C. is 10 ⁻¹
S / cm.

Therefore, when Al ₂ O ₃ : P ₂ O ₅ is 60: 40-
The solid electrolyte using an electrolyte material of Al ₂ O ₃ .P ₂ O ₅ based glass in the range of 74:26 has a low temperature.
(600 ° C. or lower), it was confirmed that it was possible to construct a fuel cell.

Third Embodiment Next, the "Ti" (or Al ₂ O ₃ .P) of the TiO ₂ .P ₂ O ₅ -based glass shown in the first embodiment (or the second embodiment) will be described. “A” of ₂ O ₅ glass
l)) is replaced with “Zr” in a ZrO ₂ · P ₂ O ₅ system glass, in which the molar ratio between ZrO ₂ and P ₂ O ₅ (ZrO ₂ : P ₂ O 5
₅ ) is varied to form electrolyte materials C1 to C18,
The electrolyte materials C1 to C18 were vitrified to produce a solid electrolyte, and the results are shown in Table 3 below.

[0030]

[Table 3]

From the results shown in Table 3, ZrO ₂ : P ₂ O
It can be seen that the electrolyte materials C7 to C13 whose ₅ is in the range of 64:36 to 76:24 can be vitrified. As a result of measuring the electric conductivity of each of the solid electrolytes using the electrolyte materials C7 to C13 in which ZrO ₂ : P ₂ O ₅ is in the range of 64:36 to 76:24, substantially the same electric conductivity is obtained, Conductivity at a temperature of 600 ° C. is 10 ⁻¹ S
/ Cm.

Therefore, when ZrO ₂ : P ₂ O ₅ is 64: 36-
76:24, the solid electrolyte using an electrolyte material made of ZrO ₂ · P ₂ O ₅ based glass has a low temperature.
(600 ° C. or lower), it was confirmed that it was possible to construct a fuel cell.

(Fourth Embodiment) Next, the "Ti" (or Al ₂ O ₃ ) of the TiO ₂ .P ₂ O ₅ based glass shown in the first embodiment (or the second and third embodiments) is described. "Al" in · P ₂ O ₅ based glass, the glass of HfO ₂ · P ₂ O ₅ system which replaces the "Zr") glass ZrO ₂ · P ₂ O ₅ based on the "Hf", and HfO ₂ the molar ratio of _{P 2 O 5 (HfO 2:} P 2 O 5) and was variously changed to prepare the electrolyte material D1～D18, their electrolyte material D1～D18 tried to prepare a vitrified solid electrolyte, as a result Are shown in Table 4 below.

[0034]

[Table 4]

From the results shown in Table 4 above, HfO ₂ : P ₂ O
It can be seen that the electrolyte materials D7 to D13 having _{5 in} the range of 64:36 to 76:24 can be vitrified. As a result of measuring the electric conductivity of each solid electrolyte using the electrolyte materials D7 to D13 in which HfO ₂ : P ₂ O ₅ is in the range of 64:36 to 76:24, substantially the same electric conductivity is obtained, Conductivity at a temperature of 600 ° C. is 10 ⁻¹ S
/ Cm.

Therefore, HfO ₂ : P ₂ O ₅ is 64: 36-
76:24, a solid electrolyte using an electrolyte material composed of HfO ₂ · P ₂ O ₅ glass is used.
(600 ° C. or lower), it was confirmed that it was possible to construct a fuel cell.

As shown in the first to fourth embodiments, Ti
By using a glass containing a group element (Ti, Zr, or Hf) or Al, melting the glass, putting it into a mold, and molding, a solid electrolyte having various shapes can be easily produced.

Next, a second embodiment of the present invention will be described. In the second embodiment, the glass shown in the first and third embodiments is crystallized to form a solid electrolyte (glass ceramic;
6) to reduce the operating temperature of the fuel cell and improve production efficiency.

FIG. 3 shows a manufacturing process diagram of a solid electrolyte using glass ceramics according to the second embodiment. Note that components similar to those shown in FIG. 1 are omitted. In FIG. 3, step S31 indicates a crystallization step. In this step, the step shown in FIG.
The glass obtained through 11-S14) is crystallized. The crystallized glass is pulverized in a pulverizing step shown in step S32, and then pressed in a forming step shown in step S33 to be formed into a desired shape to obtain a formed body. Then, in the firing step shown in step S34, the molded body is fired to complete a solid electrolyte made of glass ceramic.

Here, the glass ceramics obtained through the manufacturing process shown in FIG. 3 will be described with reference to fifth and sixth embodiments.

(Fifth Embodiment) Using the glass (electrolyte materials A7 to A13 in Table 1) shown in the first embodiment, solid electrolytes made of glass ceramics were produced through the manufacturing steps shown in FIG. The conductivity (ionic conductivity) of these solid electrolytes was measured. As a result, each of the solid electrolytes had substantially the same conductivity, and the conductivity at 600 ° C. was 10-S · cm. Therefore, TiO ₂ : P ₂
TiO _2. O _{5 in} the range of 64:36 to 76:24
By using glass ceramics obtained by crystallizing P ₂ O ₅ glass as a solid electrolyte, low temperature (600
(° C. or less), it was confirmed that it was possible to construct a fuel cell that operates at a temperature of not more than (° C.).

(Sixth Embodiment) Using the glass shown in the third embodiment (electrolyte materials C7 to C13 in Table 3), solid electrolytes made of glass ceramics were produced through the manufacturing steps shown in FIG. The conductivity (ionic conductivity) of these solid electrolytes was measured. As a result, each of the solid electrolytes had substantially the same conductivity, and the conductivity at 600 ° C. was 10 ⁻¹ S · cm. Therefore, ZrO ₂ : P ₂
ZrO ₂ .O _{5 in} which O ₅ is in the range of 64:36 to 76:24
By using glass ceramics obtained by crystallizing P ₂ O ₅ glass as a solid electrolyte, low temperature (600
(° C. or less), it was confirmed that it was possible to construct a fuel cell that operates at a temperature of not more than (° C.).

[0043]

As described above, according to the present invention, Ti
A glass containing a group III element (Ti, Zr, or Hf) or an Al element can be easily formed into a solid electrolyte by using the glass, and at a temperature of 600 ° C. or lower using the solid electrolyte. Since a fuel cell that can operate can be configured, a metal material such as stainless steel can be used without using expensive ceramics or special heat-resistant materials, and is similar to a zirconia-based fuel cell that operates at a temperature of 1000 ° C. Battery characteristics can be obtained.

In the case where a fuel cell is formed by using a solid electrolyte obtained by crystallizing the glass (glass containing a Ti element or a Zr element), a fuel cell using a solid electrolyte made of the glass may Similar functions and effects can be obtained.

Therefore, it is possible to reduce the manufacturing cost of the fuel cell and to improve the manufacturing efficiency.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a solid electrolyte according to a first embodiment of the present invention.

FIG. 2 is an Arrhenius plot showing ionic conductivity characteristics with respect to temperature (first embodiment).

FIG. 3 is a manufacturing process diagram of a solid electrolyte according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a solid oxide fuel cell.

[Explanation of symbols]

 S11: Mixing / stirring step S12: Preheating step S13: Melting step S14: Cooling step S31: Crystallizing step S32: Pulverizing step S33: Forming step S34: Firing step

Continued on the front page F term (reference) 4G062 AA11 BB09 CC10 DA01 DB06 DB07 DC01 DD04 DD05 DE01 DF01 EA01 EA10 EB01 EC01 ED01 EE01 EF01 EG01 FA01 FB06 FB07 FC06 FC07 FD01 FE01 FF01 FG01 FH01 G01H01 GC01 FL01 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH18 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM23 NN25 5H026 AA06 BB00 EE12 HH05

Claims (6)

[Claims] 1. A solid electrolyte fuel cell comprising a solid electrolyte having ionic conductivity and an oxygen electrode and a hydrogen electrode, wherein the solid electrolyte is formed of glass containing a Ti group element or an Al element in a desired shape. A solid oxide fuel cell characterized by being molded into a solid electrolyte fuel cell. Wherein said solid electrolyte with a glass of TiO ₂ · P ₂ O ₅ system, the molar ratio of TiO ₂ and P ₂ O ₅ in the glass is 64: 36 to 76: characterized in that it is 24 The solid oxide fuel cell according to claim 1, wherein Wherein said solid electrolyte with Al ₂ O ₃ · P ₂ O ₅ based glass, the molar ratio of Al ₂ O ₃ and P ₂ O ₅ in the glass is 60: 40-74: 26 2. The solid oxide fuel cell according to claim 1, wherein: Wherein said solid electrolyte with a glass of ZrO ₂ · P ₂ O ₅ system, the molar ratio of ZrO ₂ and P ₂ O ₅ in the glass is 64: 36 to 76: characterized in that it is 24 The solid oxide fuel cell according to claim 1, wherein Wherein said solid electrolyte with a glass of HfO ₂ · P ₂ O ₅ system, the molar ratio of HfO ₂ and P ₂ O ₅ in the glass is 64: 36 to 76: characterized in that it is 24 The solid oxide fuel cell according to claim 1, wherein 6. The solid oxide fuel cell according to claim 2, wherein a glass ceramic obtained by crystallizing the glass is used as a solid electrolyte.