Electrochemical cell, electrochemical cell stack, method for producing electrochemical cell, and method for producing electrochemical cell stack

文档序号：1821744 发布日期：2021-11-09 浏览：22次中文

阅读说明：本技术 电化学电池单元、电化学电池堆、电化学电池单元的制造方法和电化学电池堆的制造方法 (Electrochemical cell, electrochemical cell stack, method for producing electrochemical cell, and method for producing electrochemical cell stack ) 是由嘉久和孝喜多洋三中村雅俊于 2020-06-01 设计创作，主要内容包括：本公开的电化学电池单元,具备：平板型的膜-电极接合体,其是使电解质膜、配置于所述电解质膜的一个面的第1电极层和配置于所述电解质膜的另一个面的第2电极层层叠而构成的；第1集电部,其与所述膜-电极接合体的所述第1电极层接触；互连器,其与所述第1集电部电连接；第2集电部,其与所述膜-电极接合体的所述第2电极层接触；以及由金属材料构成的外周部,其与所述互连器和所述电解质膜一起包围所述第1电极层的外周从而形成向所述第1电极层引导内部气体的气体导入空间。(An electrochemical cell of the present disclosure includes: a flat-plate membrane-electrode assembly in which an electrolyte membrane, a 1 st electrode layer disposed on one surface of the electrolyte membrane, and a 2 nd electrode layer disposed on the other surface of the electrolyte membrane are laminated; a 1 st collector portion in contact with the 1 st electrode layer of the membrane-electrode assembly; an interconnector electrically connected to the 1 st power collecting unit; a 2 nd collector portion in contact with the 2 nd electrode layer of the membrane-electrode assembly; and an outer peripheral portion made of a metal material that surrounds an outer periphery of the 1 st electrode layer together with the interconnector and the electrolyte membrane to form a gas introduction space that guides an internal gas to the 1 st electrode layer.)

1. An electrochemical cell stack includes a cell and a mounting base portion,

the unit has:

a flat-plate membrane-electrode assembly in which an electrolyte membrane, a 1 st electrode layer disposed on one surface of the electrolyte membrane, and a 2 nd electrode layer disposed on the other surface of the electrolyte membrane are laminated;

a 1 st collector portion in contact with the 1 st electrode layer of the membrane-electrode assembly;

an interconnector electrically connected to the 1 st power collecting unit;

a 2 nd collector portion in contact with the 2 nd electrode layer of the membrane-electrode assembly; and

an outer peripheral portion made of a metal material that surrounds an outer periphery of the 1 st electrode layer together with the interconnector and the electrolyte membrane to form a gas introduction space that introduces an internal gas into the 1 st electrode layer,

the mounting base portion has a fixing portion for electrically connecting and fixing the 2 nd power collecting portion of one of the cells and the interconnector of the other of the cells between the adjacent cells, and the fixing portion is formed of an electrically insulating member.

2. The electrochemical cell stack of claim 1,

the outer peripheral portion has an inflow portion for allowing the internal gas to flow into the gas introduction space, and a discharge portion for discharging the internal gas used for the electrochemical reaction of the membrane-electrode assembly from the gas introduction space,

the mounting base portion has a gas supply passage that communicates with the gas introduction space via the inflow portion and supplies the internal gas to the gas introduction space.

3. The electrochemical cell stack of claim 1 or 2,

the electrically insulating member is a ceramic member.

4. The electrochemical cell stack of claim 2 or 3,

the gas recovery unit is provided to recover the internal gas discharged from the gas introduction space through the discharge unit.

5. The electrochemical cell stack of any of claims 2 to 4,

the inflow portion and the discharge portion provided in the outer peripheral portion are provided at positions symmetrical with respect to the membrane-electrode assembly when viewed in a plane in a stacking direction of the cells.

6. The electrochemical cell stack of claim 5,

the membrane-electrode assembly has a circular shape.

7. The electrochemical cell stack of any one of claims 2 to 6,

the opening width dimensions of the inflow portion and the discharge portion are within the range of the projection width of the membrane-electrode assembly in the flow direction of the internal gas.

8. The electrochemical cell stack of any one of claims 1 to 7,

the outer peripheral portion is joined to the electrolyte membrane by means of any one selected from glass, ceramic, and silver solder.

9. The electrochemical cell stack of any one of claims 1 to 8,

the metal material constituting the outer peripheral portion is stainless steel.

10. An electrochemical cell comprising:

a 1 st collector portion in contact with the 1 st electrode layer of the membrane-electrode assembly;

an interconnector electrically connected to the 1 st power collecting unit;

a 2 nd collector portion in contact with the 2 nd electrode layer of the membrane-electrode assembly; and

and an outer peripheral portion made of a metal material that surrounds an outer periphery of the 1 st electrode layer together with the interconnector and the electrolyte membrane, thereby forming a gas introduction space that guides an internal gas to the 1 st electrode layer.

11. The electrochemical cell of claim 10,

the outer peripheral portion has an inflow portion for allowing the internal gas to flow into the gas introduction space, and an exhaust portion for exhausting the internal gas, which is used for the electrochemical reaction of the membrane-electrode assembly, from the gas introduction space.

12. The electrochemical cell of claim 11,

13. An electrochemical cell according to any one of claims 10 to 12,

the membrane-electrode assembly has a circular shape.

14. The electrochemical cell of claim 11,

the opening width dimensions of the inflow portion and the discharge portion are within the range of the projection width of the membrane-electrode assembly in the flow direction of the internal gas.

15. An electrochemical cell according to any one of claims 10 to 14,

the outer peripheral portion is joined to the electrolyte membrane by means of any one selected from glass, ceramic, and silver solder.

16. A method for manufacturing an electrochemical cell according to claim 10, comprising:

step 1: applying a 1 st paste to a 1 st joint portion, and applying a 2 nd paste having conductivity to a 2 nd joint portion, the 1 st joint portion joining the outer peripheral portion and a surface of the electrolyte membrane on the 2 nd electrode layer side, the 2 nd joint portion joining a surface of the 2 nd electrode layer on a side where the 2 nd current collecting portion is provided and the 2 nd current collecting portion, the 1 st paste being any one selected from a glass sealant, a ceramic adhesive, and a silver solder;

step 2: press-bonding the outer peripheral portion and the electrolyte membrane at the 1 st bonding portion, and press-bonding the 2 nd electrode layer and the 2 nd current collecting portion at the 2 nd bonding portion; and

step 3: firing the 1 st joint and the 2 nd joint together at 800 to 900 ℃ to form the unit.

17. A method for manufacturing an electrochemical cell stack according to claim 1, comprising:

step 3: firing the 1 st joint and the 2 nd joint together at 800 to 900 ℃ to form the unit;

step 4: applying a glass sealant or a ceramic adhesive to a 3 rd joint portion, the 3 rd joint portion joining the unit formed in the 3 rd step and the mounting base portion; and

step 5: and firing the 3 rd joint at a temperature lower than the firing temperature in the 3 rd step.

Technical Field

The present disclosure relates to electrochemical cells, electrochemical cell stacks, methods of manufacturing electrochemical cells, and methods of manufacturing electrochemical cell stacks.

Background

As the electrochemical cell, for example, a fuel cell in which a fuel electrode layer is disposed on one surface of a membrane-electrode assembly and an air electrode layer is disposed on the other surface thereof, and power is generated by supplying a fuel gas containing hydrogen to the fuel electrode layer and supplying an oxidant gas to the air electrode layer can be exemplified. Alternatively, a hydrogen generator that generates hydrogen from high-temperature water vapor by applying a voltage to the membrane-electrode assembly can be exemplified.

However, in the fuel cell, high power generation output cannot be obtained by 1 unit cell or 1 unit cell (unit) in which a collector electrode or the like is attached to a unit cell. Therefore, the fuel cell realizes high power generation output by stacking (integrating) a plurality of single cells or units. Hereinafter, a structure in which a single cell or a cell is stacked is referred to as a battery cell.

When the shape of the cell constituting the battery cell is, for example, a flat plate shape, a load of a predetermined magnitude is applied to the entire battery cell along the stacking direction of the cell. This can reduce the electrical contact resistance between the electrode layer and the current collecting portion in the cell while maintaining the gas tightness between the cells (for example, patent document 1). However, in order to realize such a structure, an expensive and large-sized joint member capable of applying an appropriate load at a high temperature is required.

Thus, cylindrical flat-type battery cells in which a cylindrical type and a flat type are mixed have been proposed (for example, patent documents 2 and 3). The cylindrical flat cell can be stacked (integrated) by inserting a plurality of cylindrical flat cells into a long manifold into which a fuel gas is introduced. Therefore, the cylindrical flat-plate battery cell can have a simple structure that does not require a fastening load to be applied to the stack.

Prior art documents

Patent document

Patent document 1: japanese patent No. 5368333

Patent document 2: japanese patent No. 5119257

Patent document 3: japanese patent No. 4018922

Disclosure of Invention

However, in the conventional battery cells (the battery cells disclosed in patent documents 2 and 3), gas leakage of internal gas and cell rupture cannot be sufficiently prevented.

The present disclosure proposes, as an example, an electrochemical cell capable of preventing gas leakage of internal gas and cell rupture with a simple structure.

An electrochemical cell of the present disclosure includes:

a 1 st collector portion in contact with the 1 st electrode layer of the membrane-electrode assembly;

an inter connector (inter connector) electrically connected to the 1 st power collecting unit;

a 2 nd collector portion in contact with the 2 nd electrode layer of the membrane-electrode assembly; and

In order to solve the above-described problems, one embodiment of an electrochemical cell stack according to the present disclosure includes a cell and a mounting base portion,

the unit has:

a 1 st collector portion in contact with the 1 st electrode layer of the membrane-electrode assembly;

an interconnector electrically connected to the 1 st power collecting unit;

a 2 nd collector portion in contact with the 2 nd electrode layer of the membrane-electrode assembly; and

The present disclosure is configured as described above, and an effect of preventing gas leakage of internal gas and cell breakage with a simple structure is obtained.

Drawings

Fig. 1 is a side view showing an example of the structure of an electrochemical cell according to an embodiment of the present disclosure.

Fig. 2 is a plan view showing an example of the structure of the electrochemical cell shown in fig. 1.

Fig. 3 is a cross-sectional view a-a of the electrochemical cell shown in fig. 1.

Fig. 4 is a B-B sectional view of a cell provided in the electrochemical cell shown in fig. 2.

Fig. 5 is a view schematically showing the positional relationship between the outer peripheral portion and the membrane-electrode assembly when the cell provided in the electrochemical cell of the present disclosure is viewed from the stacking direction.

Fig. 6 is a side view showing an example of the structure of an electrochemical cell according to modification 1 of the embodiment of the present disclosure.

Fig. 7 is a perspective view showing an example of the structure of the electrochemical cell shown in fig. 6.

Fig. 8 is a cross-sectional view of a cell having the electrochemical cell shown in fig. 6.

Fig. 9 is a view schematically showing the cross-sectional shape of a cell and the flow of internal gas in an electrochemical cell according to modification 2 of the present disclosure.

Fig. 10 is a view schematically showing the cross-sectional shape of a cell and the flow of internal gas in which the width of the inflow portion differs from that of modification 2 of the present disclosure.

Fig. 11 is a flowchart illustrating an example of a method for manufacturing an electrochemical cell according to the present disclosure.

Fig. 12 is a diagram schematically illustrating the process carried out in step S1 illustrated in fig. 11.

Fig. 13 is a diagram schematically illustrating the process carried out in step S2 illustrated in fig. 11.

Detailed Description

(pass through which one embodiment of the present invention is obtained)

The present inventors have conducted intensive studies on the electrochemical battery cells disclosed in patent documents 1 to 3. First, the electrochemical cell according to patent document 1 has a structure in which flat plate type cells are stacked. Here, in order to allow the oxidant gas and the fuel gas to communicate with each other in the stacking direction of the flat-plate cell, the gas manifold is also used as the fastening shaft space. As described above, the electrochemical cell according to patent document 1 requires a mechanism for pressurizing the flat-plate cell in the stacking direction, and also requires a structure for conducting the oxidizing gas and the fuel gas. Therefore, the electrochemical cell according to patent document 1 has problems in versatility and cost reduction.

On the other hand, the electrochemical cells according to patent documents 2 and 3 have the following structures: cylindrical flat plate-shaped cells made of ceramic and having a plurality of gas passages and composed of an inner electrode, a solid electrolyte and an outer electrode are connected to each other by a current collecting member through a conductive paste. One end of each of the connected cylindrical flat plate units is inserted into a manifold for supplying fuel gas, and is sealed by adhesion with a glass sealant or the like, thereby stacking the units.

In the battery cells according to patent documents 2 and 3, a separator or the like for preventing the leakage of the oxidizing gas to the fuel electrode side is not required, and a simple structure can be provided. In particular, in patent document 2, since elastic support members are disposed at both ends of the stacked cylindrical flat plate type unit, it is possible to absorb warpage of ceramics and the like without providing an expensive fastening member.

However, in the electrochemical cells according to patent documents 2 and 3, it is necessary to manufacture a cylindrical flat plate cell having a special shape composed of an inner electrode, a solid electrolyte, and an outer electrode made of ceramic, which requires a plurality of gas passages. Therefore, a general flat-plate type membrane-electrode assembly cannot be used. Thus, it was found that: the electrochemical cells according to patent documents 2 and 3 have a problem that it is difficult to apply a flat membrane-electrode assembly that is commonly used. Further, it has been found that a cylindrical flat plate type cell having a special shape is difficult to apply and use: there is also a problem in reducing the cost.

In addition, the electrochemical cell according to patent documents 2 and 3 has a structure in which one end of a plurality of cylindrical flat plate-shaped units made of ceramic is inserted into the fuel gas manifold and is sealed by bonding with a glass sealing agent or the like, as described above. Thus, it was found that: it is difficult to provide a structure capable of ensuring sufficient durability against thermal stress generated by displacement of the cylindrical flat plate type unit due to temperature change.

Further, since the cylindrical flat plate type unit is made of ceramic, it has low thermal conductivity and poor heat dissipation compared with a metal member or the like. Therefore, the following problems arise: when the current density is increased to further improve the performance of the electrochemical cell or to reduce the size of the electrochemical cell, the electrochemical cell is subjected to heat. Thus, it was found that: the electrochemical cells according to patent documents 2 and 3 are difficult to be configured to improve performance and to be compact.

Then, the present inventors have made extensive studies on these problems, and as a result, have obtained the following findings. That is, first, the cell is configured such that a fuel electrode (1 st electrode layer) of a ceramic flat plate battery (membrane-electrode assembly) is surrounded by a metal outer peripheral portion, for example, to form a gas introduction space for introducing an internal gas (for example, a fuel gas containing hydrogen). This structure can prevent gas leakage of the internal gas. Moreover, the oxidizing gas supplied to the air electrode (2 nd electrode layer) side can be prevented from leaking to the 1 st electrode layer side. In addition, it was found that: since the outer peripheral portion is formed of a thin metal material, even if the membrane-electrode assembly is displaced due to a temperature change, the influence of the displacement can be absorbed by the deflection of the outer peripheral portion, and the membrane-electrode assembly can be prevented from cracking.

In addition, it was found that: by configuring such that adjacent cells are connected to each other via the current collecting portion and the plurality of cells are fixed to the mounting base portion via the fixing portion made of the electrically insulating member, short-circuiting of each cell can be prevented. In addition, it was also found that: since a joining mechanism for pressurization is not required as in the conventional flat plate type unit structure having a flat plate type membrane-electrode assembly, a simple structure can be provided. Also, in the present disclosure, the following modes are provided.

An electrochemical cell stack according to claim 1 of the present disclosure includes a cell and a mounting base portion,

the unit has:

a 1 st collector portion in contact with the 1 st electrode layer of the membrane-electrode assembly;

an interconnector electrically connected to the 1 st power collecting unit;

a 2 nd collector portion in contact with the 2 nd electrode layer of the membrane-electrode assembly; and

According to the above configuration, the plurality of units are fixed by the mounting base portion configured by using the electrically insulating member. Therefore, each unit is electrically insulated by the mounting base portion, and short-circuiting can be prevented. Further, since a joining mechanism for pressurization is not required as in the conventional flat-plate type unit structure having a flat-plate type membrane-electrode assembly, a simple structure can be provided.

In the cell, the interconnector, the electrolyte membrane, and the outer peripheral portion made of a metal material form a gas introduction space, and therefore gas leakage of the internal gas can be prevented. Further, even when the cell is exposed to a high temperature and the membrane-electrode assembly is displaced, the outer peripheral portion is made of a thin metal material and can be bent, and therefore, the pressure generated by the displacement can be absorbed. Therefore, the membrane-electrode assembly can be prevented from being broken in the cell.

Therefore, the electrochemical cell according to claim 1 of the present invention has an effect that gas leakage of the internal gas and cell rupture can be prevented with a simple structure.

The electrochemical cell stack according to claim 2 of the present disclosure may have the following structure: in the aforementioned aspect 1, the outer peripheral portion includes an inflow portion that allows the internal gas to flow into the gas introduction space, and an exhaust portion that exhausts the internal gas that has been used in the electrochemical reaction of the membrane-electrode assembly from the gas introduction space, and the mounting base portion includes a gas supply passage that communicates with the gas introduction space via the inflow portion and supplies the internal gas to the gas introduction space.

According to the above configuration, since the mounting base portion includes the gas supply passage, it is not necessary to provide the gas supply passage separately from the mounting base portion. Therefore, the device structure can be miniaturized.

In the electrochemical cell stack according to claim 3 of the present disclosure, in addition to the above-described 1 st or 2 nd aspect, the electrically insulating member may be a ceramic member.

According to the above configuration, since the mounting base portion is formed using a ceramic member, it is possible to provide heat resistance and electrical insulation. Therefore, it is possible to prevent a short circuit from occurring between the plurality of cells fixed by the mounting base portion.

An electrochemical cell stack according to claim 4 of the present disclosure may further include a gas recovery unit that recovers the internal gas discharged from the gas introduction space through the discharge unit, in addition to the above-described 2 nd or 3 rd aspect.

According to the above configuration, since the gas recovery portion is provided, the internal gas discharged from the gas introduction space through the discharge portion can be recovered from all of the cells and mixed and homogenized.

However, as the utilization rate of the internal gas by the electrochemical reaction increases, the concentration of a combustible gas such as hydrogen contained in the internal gas decreases. Further, due to the difference in the utilization rate of the internal gas in each unit, the concentration of the combustible gas contained in the internal gas discharged from the discharge portion of each unit differs.

Here, for example, a configuration can be conceived in which the discharged internal gas is burned by the combustion section. In such a configuration, when the internal gas discharged from the discharge portion of each cell is directly burned by the combustion portion, if the internal gas contains an amount of the combustible gas whose concentration is reduced to such an extent that the combustion by the combustion portion is inhibited, the internal gas is not burned, and thus a local misfire occurs.

However, in the electrochemical cell stack according to claim 4 of the present invention, the discharged internal gas can be mixed by the gas recovery unit to make the combustible gas concentration uniform. Therefore, occurrence of a local misfire can be prevented.

An electrochemical cell stack according to claim 5 of the present disclosure is configured such that, in any one of the above-described aspects 2 to 4, the inflow portion and the discharge portion provided in the outer peripheral portion are provided at positions symmetrical with respect to the membrane-electrode assembly in a plan view of the cell stacking direction.

According to the above configuration, the internal gas can be efficiently supplied to the 1 st electrode layer of the membrane-electrode assembly in the gas introduction space.

The position symmetrical with respect to the membrane-electrode assembly may be a position symmetrical with respect to the center of the membrane-electrode assembly.

In the electrochemical cell stack according to claim 6 of the present disclosure, in addition to the above-described aspect 5, the membrane-electrode assembly may have a circular shape.

According to the above configuration, since the membrane-electrode assembly has a circular shape, the strength can be improved as compared with a square-shaped membrane-electrode assembly, for example.

An electrochemical cell stack according to claim 7 of the present disclosure may be configured such that, in any one of the above-described aspects 2 to 6, the opening width dimensions of the inflow portion and the discharge portion are within a range of a projection width of the membrane-electrode assembly in a flow direction of the internal gas.

According to the above configuration, as compared with the configuration in which the opening width dimensions of the inflow portion and the discharge portion are equal to or larger than the projection width of the membrane-electrode assembly in the flow direction of the internal gas, the internal gas can be supplied more uniformly to the 1 st electrode layer of the membrane-electrode assembly without depending on the shape (for example, circular or square) of the membrane-electrode assembly.

An electrochemical cell stack according to claim 8 of the present disclosure is the electrochemical cell stack according to any one of the above-described 1 to 7, wherein the outer peripheral portion is joined to the electrolyte membrane via any one selected from glass, ceramic, and silver solder.

According to the above configuration, the internal gas can be sealed so as not to flow out from the gas introduction space to the outside. In addition, the cell can have a strength capable of withstanding high temperatures even when exposed to high temperatures.

Further, even if the membrane-electrode assembly contracts and expands due to a temperature change, the electrolyte membrane is joined to the outer peripheral portion via any one of glass, ceramic, and silver solder, and therefore, the stress caused by the displacement of the membrane-electrode assembly can be absorbed by the outer peripheral portion.

In the electrochemical cell stack according to claim 9 of the present disclosure, in any one of the above-described 1 st to 8 th aspects, the metal material constituting the outer peripheral portion may be stainless steel.

According to the above configuration, since the metal material constituting the outer peripheral portion is stainless steel, the outer peripheral portion can sufficiently have oxidation resistance and strength even when the cell is exposed to high temperatures. Further, the outer peripheral portion can have a thermal expansion coefficient close to that of the ceramic mainly constituting the film-electrode assembly. Therefore, the generation of thermal stress or the like at the joint portion between the outer peripheral portion and the electrolyte membrane can be suppressed to the minimum.

An electrochemical cell according to claim 10 of the present disclosure includes:

a 1 st collector portion in contact with the 1 st electrode layer of the membrane-electrode assembly;

an interconnector electrically connected to the 1 st power collecting unit;

a 2 nd collector portion in contact with the 2 nd electrode layer of the membrane-electrode assembly; and

An electrochemical cell according to claim 11 of the present disclosure is the above-described 10 th aspect, wherein the outer peripheral portion includes an inflow portion that allows the internal gas to flow into the gas introduction space, and an exhaust portion that exhausts the internal gas that is used in the electrochemical reaction of the membrane-electrode assembly from the gas introduction space.

An electrochemical cell according to claim 12 of the present disclosure is the aforementioned 11 th aspect, wherein the inflow portion and the discharge portion provided in the outer peripheral portion are provided at positions symmetrical with respect to the membrane-electrode assembly when viewed in a plane in a stacking direction of the cell.

An electrochemical cell according to claim 13 of the present disclosure is the electrochemical cell according to any one of the above-described 10 th to 12 th aspects, wherein the membrane-electrode assembly has a circular shape.

An electrochemical cell according to claim 14 of the present disclosure is the aforementioned 11 th aspect, wherein the inflow portion and the discharge portion have opening widths within a range of a projected width of the membrane-electrode assembly in a flow direction of the internal gas.

An electrochemical cell according to claim 15 of the present disclosure is the electrochemical cell according to any one of the above-described 10 th to 14 th aspects, wherein the outer peripheral portion is joined to the electrolyte membrane via any one selected from glass, ceramic, and silver solder.

A method for manufacturing an electrochemical cell according to claim 16 of the present disclosure is a method for manufacturing an electrochemical cell including a cell and a mounting base portion, the cell including:

a 1 st collector portion in contact with the 1 st electrode layer of the membrane-electrode assembly;

an interconnector electrically connected to the 1 st power collecting unit;

a 2 nd collector portion in contact with the 2 nd electrode layer of the membrane-electrode assembly; and

the mounting base portion has a fixing portion for electrically connecting and fixing the 2 nd power collecting portion of one of the cells and the interconnector of the other of the cells between the adjacent cells, the fixing portion being formed of an electrically insulating member,

the manufacturing method comprises the following steps:

step 3: firing the 1 st joint and the 2 nd joint together at 800 to 900 ℃ to form the unit.

According to the above method, since the 1 st joint part and the 2 nd joint part can be fired together in the 3 rd step, the process can be shortened as compared with a method in which firing is performed separately. In addition, the following problems can be prevented: when different pastes are fired in separate steps, the paste fired in the previous step is remelted when the paste different from the former paste is fired in the subsequent step.

A method for manufacturing an electrochemical cell stack according to claim 17 of the present disclosure includes:

step 3: firing the 1 st joint and the 2 nd joint together at 800 to 900 ℃ to form the unit;

step 4: applying a glass sealant or a ceramic adhesive to a 3 rd joint portion, the 3 rd joint portion joining the unit formed in the 3 rd step and the mounting base portion; and

step 5: and firing the 3 rd joint at a temperature lower than the firing temperature in the 3 rd step.

According to the above method, the temperature of firing the 3 rd joint in the 5 th step is lower than the temperature of firing the 1 st joint and the 2 nd joint in the 3 rd step. Therefore, during firing of the 3 rd joint, re-melting of the 1 st paste at the 1 st joint and the 2 nd paste at the 2 nd joint can be suppressed. Therefore, the 1 st to 3 rd joint portions can be joined reliably.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same or corresponding constituent elements are denoted by the same reference numerals throughout the drawings, and the description thereof may be omitted.

[ embodiment ]

An electrochemical cell stack 100 according to an embodiment of the present disclosure is a battery cell including a flat-plate-type membrane-electrode assembly 34, in which the flat-plate-type membrane-electrode assembly 34 is configured by laminating an electrolyte membrane 32, a 1 st electrode layer 31 disposed on one surface of the electrolyte membrane 32, and a 2 nd electrode layer 33 disposed on the other surface of the electrolyte membrane 32. In the embodiment of the present disclosure, a structure of a solid oxide fuel cell including the membrane-electrode assembly 34 having a flat plate square shape is described as an example. However, the electrochemical cell stack 100 is not limited to the solid oxide fuel cell, and may be a water electrolysis stack for producing hydrogen or the like from high-temperature water vapor by applying a voltage to the membrane-electrode assembly 34. The shape of the membrane-electrode assembly 34 of the electrochemical cell stack 100 is not limited to a flat square shape, and may be, for example, a flat circular shape.

The structure of the electrochemical cell stack 100 according to the embodiment of the present disclosure will be described below with reference to fig. 1 to 4. Fig. 1 is a side view showing an example of the structure of an electrochemical cell stack 100 according to an embodiment of the present disclosure. Fig. 2 is a plan view showing an example of the structure of the electrochemical cell stack 100 shown in fig. 1. Fig. 3 is a cross-sectional view a-a of the electrochemical cell stack 100 shown in fig. 1. Fig. 4 is a B-B sectional view of the electrochemical cell 41 included in the electrochemical cell stack 100 shown in fig. 2.

Note that, in fig. 1, the flow of the internal gas (for example, fuel gas) is shown by a dotted arrow, and in fig. 2, the flow of the oxidant gas is shown by a solid arrow. In addition, in fig. 3, only the cross-sectional shape of the coupled electrochemical cells 41 cut at a-a is shown. In fig. 4, the cross-sectional shape of any 1 electrochemical cell 41 cut at B-B is shown.

As shown in fig. 1 and 2, the electrochemical cell stack 100 includes an electrochemical cell 41 and a mounting base portion 42. As shown in fig. 3, the electrochemical cell 41 includes, in addition to the membrane-electrode assembly 34 described above: a 1 st current collecting portion 35 in contact with the 1 st electrode layer 31 of the membrane-electrode assembly 34; an interconnector 36 electrically connected to the 1 st collector portion 35; a 2 nd collector unit 40 in contact with the 2 nd electrode layer 33 of the membrane-electrode assembly 34; and an outer peripheral portion 39 made of a metal material that surrounds the outer periphery of the 1 st electrode layer 31 together with the interconnector 36 and the electrolyte membrane 32 to form a gas introduction space 50 that guides the internal gas to the 1 st electrode layer 31.

More specifically, as shown in fig. 3, the electrochemical cell 41 has a flat square shape as follows: on one surface in the stacking direction, a metal interconnector 36 is provided, and on the other surface, the 2 nd electrode layer 33 in contact with the electrolyte membrane 32 is exposed, and the side periphery of the electrochemical cell 41 is surrounded by a metal outer peripheral portion 39. The interconnector 36 electrically connected to the 1 st current collecting portion 35 includes, for example, the 1 st current collecting portion 35 and the interconnector 36 in contact with each other.

[ Membrane-electrode Assembly ]

The membrane-electrode assembly 34 includes an electrolyte membrane 32, a 1 st electrode layer 31, and a 2 nd electrode layer 33. The electrolyte membrane 32 of the membrane-electrode assembly 34 may be made of YSZ ceramics that conducts oxygen ions. Alternatively, Barium Zirconate (BZY) containing yttrium or barium zirconate (BZYb) containing ytterbium, which conducts protons, may be used. In this way, the membrane-electrode assembly 34 may be an oxygen ion type in which oxygen ions pass through the inside of the electrolyte membrane 32, or a proton type in which hydrogen ions pass through the inside of the electrolyte membrane 32.

When the electrochemical cell stack 100 is used as a single solid oxide fuel cell, the operating temperature is about 600 to 800 ℃. In particular, when an electrolyte membrane having proton conductivity is used as the electrolyte membrane 32, the operating temperature of the solid oxide fuel cell can be reduced to about 600 ℃.

The 1 st electrode layer 31 of the membrane-electrode assembly 34 functions as a so-called fuel electrode in a solid oxide fuel cell. The 1 st electrode layer 31 may be made of metal such as Pt, Au, Ag, Pb, Ir, Ru, Rh, Ni, Fe, or ceramics. The 1 st electrode layer 31 may be composed of only 1 of these metals, or may be composed of an alloy containing 2 or more of these metals.

On the other hand, the 2 nd electrode layer 33 included in the membrane-electrode assembly 34 functions as a so-called air electrode in the solid oxide fuel cell. The 2 nd electrode layer 33 may be composed of any one selected from lanthanum strontium cobalt composite oxide (LSC), lanthanum strontium cobalt iron composite oxide (LSCF), and lanthanum strontium iron composite oxide (LSF).

In the electrochemical cell stack 100 according to the embodiment, the fuel gas is supplied as the internal gas to the 1 st electrode layer 31, and the oxidant gas is supplied to the 2 nd electrode layer 33, so that power is generated in the membrane-electrode assembly 34.

The internal gas may be, for example, a high-temperature gas containing hydrogen generated from the raw material gas by a reforming reaction in the reformer. Examples of the raw material gas include hydrocarbon gases such as city gas and propane gas. In addition, natural gas, naphtha (naphtha), coal gasification gas, or the like may be used. The raw gas may be hydrogen gas or a mixed gas of hydrogen gas and hydrocarbon gas. The raw material gas may be 1 kind of gas, or a mixture or a combination of a plurality of kinds of gases. The raw gas may contain an inert gas such as nitrogen or argon. Further, a gas obtained by gasifying a solid or liquid raw material may be used as the raw material gas, or a hydrogen gas obtained by reforming a gas other than the above-described hydrocarbon gas may be used as the raw material gas. On the other hand, the oxidizing gas is preferably air which is safe and inexpensive, but may be a mixed gas of oxygen and another gas.

The internal gas is supplied to the gas supply passage 45 provided in the mounting base portion 42 via a gas pipe (not shown) disposed outside the electrochemical cell stack 100. Then, the gas is uniformly distributed to the electrochemical cells 41 in the gas supply passage 45, and is introduced into the gas introduction space 50 formed in the outer peripheral portion 39 of each electrochemical cell 41. On the other hand, as shown in fig. 2, the oxidizing gas flows in a direction perpendicular to the flow direction of the internal gas and is supplied to the 2 nd electrode layer 33.

The shape of the membrane-electrode assembly 34 is not limited to a rectangular flat plate, and may be a circular flat plate, a polygonal flat plate, or the like. In this case, the shape of the outer peripheral portion 39 is adapted to the shape of the membrane-electrode assembly 34, and the shapes of the 1 st current collecting portion 35 and the 2 nd current collecting portion 40 are changed.

In the electrochemical cell stack 100, the shapes and types of the membrane-electrode assemblies 34 incorporated in the plurality of electrochemical cells 41 to be connected may be the same or different. When the electrochemical cell stack 100 is manufactured, cost reduction can be achieved by selecting the most suitable membrane-electrode assembly 34.

[ 1 st collector part, 2 nd collector part ]

The 1 st and 2 nd power collecting portions 35 and 40 collect power from the surfaces of the 1 st and 2 nd electrode layers 31 and 33. The 1 st current collecting portion 35 electrically connects the 1 st electrode layer 31 and the interconnector 36, and the 2 nd current collecting portion 40 electrically connects the 2 nd electrode layer 33 and the interconnector 36 provided in the adjacent electrochemical cell 41.

The 1 st current collecting portion 35, which electrically connects the 1 st electrode layer 31 and the interconnector 36, is mainly made of nickel steel since the 1 st electrode layer 31 side is a reducing atmosphere. On the other hand, the 2 nd current collecting portion 40 electrically connecting the 2 nd electrode layer 33 and the interconnector 36 of the adjacent electrochemical cell 41 is mainly made of a ferritic stainless steel material having excellent oxidation resistance because the 2 nd electrode layer 33 side is in a high-temperature oxidation atmosphere.

In the electrochemical cell 41, the 1 st current collecting portion 35 in contact with the interconnector 36 may be configured such that a plurality of cut-and-raised portions are formed in a nickel plate. That is, the 1 st power collecting unit 35 may be: the interconnector 36 is configured such that a current collecting portion base material of a nickel plate and a plurality of cut-and-raised portions 60 (see fig. 9 described later) rising from the current collecting portion base material toward the 1 st electrode layer 31 by cutting are arranged so as to contact the 1 st electrode layer 31. When the 1 st current collecting portion 35 is configured in this way, electrical contact between the 1 st electrode layer 31 and the interconnector 36 can be secured, and the cut-and-raised portion 60 has elasticity, and thus can follow displacement of the membrane-electrode assembly 34. Further, the plurality of cut-and-raised portions 60 can improve the diffusivity of the internal gas in the 1 st electrode layer 31.

In the electrochemical cell 41, the 2 nd electrode layer 33 and the 2 nd current collecting portion 40 are bonded by the 2 nd paste 46 having conductivity. The 2 nd paste 46 is a paste having sufficiently small resistance at the contact even in a high-temperature environment. The 2 nd current collecting portion 40 is joined to the interconnector 36 of the adjacent electrochemical cell 41 at an end portion different from the end portion joined to the 2 nd electrode layer 33 in an electrically connected state by welding, caulking, or the like. In this way, the adjacent electrochemical cells 41 are connected and electrically connected to each other via the 2 nd current collecting unit 40. The 2 nd collector portion 40 may be formed in a pantograph shape (see fig. 2 and 3) so as to be deformable. However, the 2 nd power collecting unit 40 is not limited to such a shape, and may have a structure in which a plurality of cut-and-raised portions are formed, similarly to the 1 st power collecting unit 35. Alternatively, the 2 nd current collecting part 40 may be formed of dimples, metal mesh, metal foam, or the like.

[ interconnectors ]

The interconnector 36 is a member that electrically connects the electrochemical cells 41 to each other and collects electricity generated in the electrochemical cells 41. Electricity generated in the electrochemical cell 41 is supplied to the interconnector 36 via the 1 st and 2 nd current collecting units 35 and 40. The interconnector 36 can be a plate material having a thickness of 0.2 to 2.0mm, for example, made of ferritic stainless steel.

Current collecting members (not shown) having output terminals are provided at both ends of the group of electrochemical cells 41 connected in series, that is, both ends of the electrochemical cell stack 100. The current collecting member may be a plate for collecting current or a wire for collecting current. When the electrochemical cell stack 100 is used as a cell of a solid oxide fuel cell, electricity generated in each electrochemical cell 41 is obtained from current collecting members at both ends of the electrochemical cell stack 100 and used as electricity.

[ outer peripheral part ]

As shown in fig. 3, the outer peripheral portion 39 is joined to the electrolyte membrane 32 of the membrane-electrode assembly 34 at one end by the 1 st paste 49 with a pitch (margin for paste) of about 2 to 10mm, and is welded to the interconnector 36 at the other end all around. Further, in the case where the outer peripheral portion 39 and the interconnector 36 are joined by metal welding, durability is superior to the case where ceramic members are joined by firing, which is advantageous.

As described above, the outer peripheral portion 39 can surround the outer peripheries of the 1 st electrode layer 31 and the 1 st power collecting portion 35 together with the interconnector 36 and the electrolyte membrane 32. With this structure, the electrochemical cell 41 can form the gas introduction space 50 for introducing the internal gas into the 1 st electrode layer 31. The outer peripheral portion 39 can be formed of, for example, thin ferritic stainless steel (e.g., 0.05 to 0.15mm in thickness t).

When the outer peripheral portion 39 is formed of ferritic stainless steel in this manner, the material for manufacturing the electrochemical cell 41 can be made at low cost. Further, even when the electrochemical cell 41 is exposed to high temperature during power generation, the outer peripheral portion 39 can have sufficient oxidation resistance and strength. The outer peripheral portion 39 can have a thermal expansion coefficient close to that of the ceramic mainly constituting the film-electrode assembly 34. Therefore, the generation of thermal stress and the like in the joined portion between the outer peripheral portion 39 and the electrolyte membrane 32 and the inside of the membrane-electrode assembly 34 can be minimized.

In addition, the 1 st paste 49 may be any one selected from glass, ceramic, and silver solder. Since the outer peripheral portion 39 is joined to the electrolyte membrane 32 by the 1 st paste 49, the inner gas can be sealed so as not to flow out from the gas introduction space 50 to the outside. In addition, the electrochemical cell 41 can have a strength capable of withstanding high temperatures even when exposed to high temperatures. Further, even if the membrane-electrode assembly 34 contracts and expands due to a temperature change, the electrolyte membrane 32 is joined to the outer peripheral portion 39 via any one selected from glass, ceramic, and silver solder, and therefore, the stress caused by the displacement of the membrane-electrode assembly 34 can be absorbed by the outer peripheral portion 39. Therefore, the membrane-electrode assembly 34 can be prevented from being cracked or peeled off.

Further, an inflow portion 37 is provided in a portion of an outer peripheral portion 39 of an end portion of the electrochemical cell 41 disposed on the side where the electrochemical cell is attached to the attachment base portion 42, and a discharge portion 38 is provided in a portion of the outer peripheral portion 39 of the end portion of the electrochemical cell 41 disposed on the side opposite to the side where the inflow portion 37 is provided. Further, the apparatus is configured to: the gas supply passage 45 provided in the mounting base portion 42 and the gas introduction space 50 communicate with each other via the inflow portion 37.

As shown in fig. 5, the inflow portion 37 and the discharge portion 38 provided in the outer peripheral portion 39 are provided at positions symmetrical with respect to the membrane-electrode assembly 34 (particularly, with respect to the center O of the membrane-electrode assembly 34) when viewed in plan in the stacking direction of the electrochemical cells 41. Fig. 5 is a view schematically showing the positional relationship between the outer peripheral portion 39 and the membrane-electrode assembly 34 when the electrochemical cells 41 included in the electrochemical cell stack 100 according to the present disclosure are viewed from the stacking direction. When the inflow portion 37 and the discharge portion 38 are provided in the positional relationship as shown in fig. 5 in the outer peripheral portion 39, the internal gas can be efficiently supplied to the 1 st electrode layer 31 of the membrane-electrode assembly 34 in the gas introduction space 50.

The opening width of each of the inflow portion 37 and the discharge portion 38 when the electrochemical cell 41 is viewed in plan in the stacking direction is set within the range of the projection width of the membrane-electrode assembly 34 in the flow direction of the internal gas. Therefore, the internal gas can be uniformly supplied to the 1 st electrode layer 31 regardless of whether the membrane-electrode assembly 34 has a flat square shape or a flat circular shape as described above. The relationship between the opening width of each of the inflow portion 37 and the discharge portion 38 and the projection width of the membrane-electrode assembly 34 in the flow direction of the internal gas will be described in detail later.

Since the outer peripheral portion 39 is configured to surround the outer periphery of the 1 st electrode layer 31 together with the interconnector 36 and the electrolyte membrane 32 and form the gas introduction space 50, the internal gas does not leak from the portions other than the inflow portion 37 and the discharge portion 38, and gas leakage of the internal gas can be prevented. Even if gas leaks from the gas introduction space 50, the gas leakage site can be easily identified and repaired as compared with a structure in which the gas introduction space is formed of ceramic.

Even when the electrochemical cell 41 is exposed to high temperature and the membrane-electrode assembly 34 is displaced, the outer peripheral portion 39 is made of a thin metal material and can be bent, and therefore, stress generated by the displacement can be absorbed. Therefore, the membrane-electrode assembly 34 can be prevented from being broken in the electrochemical cell 41.

(mounting base part)

As shown in fig. 1 and 4, the mounting base portion 42 includes a fixing portion 43 made of an electrically insulating member, and the fixing portion 43 fixes the plurality of electrochemical cells 41 in a state where the 2 nd current collecting portion 40 of one electrochemical cell 41 and the interconnector 36 of the other electrochemical cell 41 are electrically connected between the adjacent electrochemical cells 41. Further, the mounting base portion 42 includes: and a gas supply passage 45 communicating with the gas introduction space 50 formed by the outer peripheral portion 39 and supplying an internal gas (for example, a fuel gas) to the gas introduction space 50.

That is, the electrochemical cell stack 100 has the following structure: a plurality of electrochemical cells 41 are arranged and coupled in the stacking direction, and one end of each electrochemical cell 41 is inserted into and fixed to a fixing portion 43 of a mounting base portion 42 that supplies internal gas. The fixing portion 43 includes a slit-shaped insertion portion 43a formed in the mounting base portion 42 and a seal joining portion 43b joining the end portion of the electrochemical cell 41 inserted into the insertion portion 43a to the mounting base portion 42. That is, the insertion portion 43a is a slit-shaped gap having a shape corresponding to the a-a cross-sectional shape of the electrochemical cell 41, and the end portion of the electrochemical cell 41 is inserted into the gap to fix the contact surface between the electrochemical cell 41 and the mounting base portion 42 by the seal joint portion 43 b. At least the surface of the insertion portion 43a that contacts the electrochemical cell 41 and the seal joint portion 43b are formed of electrically insulating members.

That is, the mounting base portion 42 is required to have electrical insulation properties because it is in direct contact with the electrochemical cells 41 having different voltages. In the electrochemical cell stack 100 according to the embodiment, at least the surface of the insertion portion 43a that contacts the electrochemical cell 41 is formed of an insulating member such as ceramic. Further, as the seal joint portion 43b, the following can be exemplified: a glass sealing agent or a ceramic adhesive agent that can achieve both electrical insulation and gas sealing between the mounting base portion 42 and the electrochemical cell 41. In the electrochemical cell stack 100 according to the embodiment, at least the surface of the insertion portion 43a that contacts the electrochemical cell 41 in the structure of the mounting base portion 42 is made of an electrically insulating member such as ceramic, but the entire mounting base portion 42 may be made of an electrically insulating member.

The internal gas flowing through the gas supply passage 45 of the mounting base portion 42 is supplied from the mounting base portion 42 to the electrochemical cell 41 through the internal gas inflow portion 37 provided in the outer peripheral portion 39 of the electrochemical cell 41. When the internal gas passes through the gas introduction space 50 of the electrochemical cell 41, hydrogen contained in the internal gas is consumed by the electrochemical reaction on the surface of the 1 st electrode layer 31. The internal gas in which hydrogen is consumed is discharged to the outside of the electrochemical cell 41 through the discharge unit 38.

The number of electrochemical cells 41 fixed and connected to the mounting base 42 can be varied according to the required amount of power generation. That is, the electrochemical cells 41 may be arranged in 1 row as shown in fig. 1 and 2, or may be arranged in 2 or more rows.

The number of electrochemical cells 41 fixed and connected to the mounting base portion 42 varies depending on the amount of power generation required in the solid oxide fuel cell or the like, the electrode area of the membrane-electrode assembly 34, the current density, and the like. For example, in the case where the solid oxide fuel cell is a power generation device for general household use, the number of connections of the electrochemical cells 41 and the area of the electrode layer of the electrochemical cells 41 are determined so that about DC780W (about AC700W) can be obtained.

When the primary surfaces of the 1 st electrode layer 31 and the 2 nd electrode layer 33 of the membrane-electrode assembly 34 mounted on the electrochemical cells 41 are square with one side being about 100mm, for example, 15 to 40 electrochemical cells 41 are connected. Since the electromotive force of each electrochemical cell 41 is about 0.8V, the electromotive force of about 12 to 32V and a large direct current of 20 to 30A can be obtained by connecting the electrochemical cells 41 in series. In the case of a large-sized commercial product, the number of electrochemical cells 41 connected may be further increased.

As described above, the internal gas supplied to each electrochemical cell 41 through the gas supply passage 45 of the mounting base 42 is guided to the gas introduction space 50 of each electrochemical cell 41 through the inflow portion 37 of the outer peripheral portion 39, and is used for the electrochemical reaction of the membrane-electrode assembly 34. The internal gas used for the electrochemical reaction is discharged to the outside as an exhaust gas through the discharge portion 38 of the outer peripheral portion 39 provided at the end portion of each electrochemical cell 41 on the side opposite to the side fixed to the mounting base portion 42. Further, the oxidant gas is supplied to the 2 nd electrode layer 33 of the electrochemical cell 41, and after being used for the electrochemical reaction of the membrane-electrode assembly 34, the oxidant gas is discharged as an exhaust gas.

The exhaust gas of the internal gas discharged through the discharge portion 38 is mixed with the exhaust gas of the oxidizing gas, is burned by a combustion portion (not shown), and is converted into combustion heat. In fig. 2, as the internal gas exhaust portion 38, 3 circular holes of about Φ 1.5mm are formed in each of the electrochemical cells 41. The opening shape of the discharge portion 38 is preferably a circular hole in consideration of combustibility, but the number, the diameter, and the pitch of the holes are not limited to these, and any suitable configuration may be used as long as it can suppress blow-off of flames, fire, and the like.

The mounting base portion 42 has the fixing portion 43 and the gas supply passage 45, but when the gas supply passage 45 is separately provided, the mounting base portion may have only the fixing portion 43.

In the electrochemical cell stack 100 according to the embodiment, as described above, the exhaust gases after the power generation are diffused and combusted directly above the exhaust portion 38. Since the metal outer peripheral portion 39 is heated by the combustion heat, the membrane-electrode assembly 34, which is important for power generation, is not directly heated, and the durability of the electrochemical cell 41 can be improved.

However, in the membrane-electrode assembly 34, due to the influence of a difference in thermal physical property values between the 3 layers including the thermal expansion coefficient, residual stress at the time of sintering, deformation stress at the time of reduction in the 1 st electrode layer 31 (fuel electrode layer), and the like, so-called uneven displacement in a garlic-like shape in which the central portion of the membrane-electrode assembly 34 becomes convex, warpage between the members, deformation, and the like occur. The electrochemical cell 41 according to the embodiment is configured such that the membrane-electrode assembly 34 is fixed by the metal outer peripheral portion 39 and the elastic first current collecting portion 35 and second current collecting portion 40. Therefore, in the electrochemical cell 41 according to the embodiment, the deformation due to the difference in thermal expansion coefficient or the like can be dispersed and absorbed by the outer peripheral portion 39, the 1 st power collecting portion 35, and the 2 nd power collecting portion 40. Therefore, the electrochemical cell 41 according to the embodiment can protect the membrane-electrode assembly 34, and reduce stress generated on the adhesive surface of the membrane-electrode assembly 34 due to deformation caused by a difference in thermal expansion coefficient or the like, thereby improving durability.

In addition, in the electrochemical cell stack 100, since the general flat-plate type membrane-electrode assembly 34 can be used as described above, it is possible to make use of the electrochemical cell stack, compared with the conventional electrochemical cell according to patent documents 2 and 3 using a cylindrical flat-plate type cell having a special shape, and it is possible to reduce the cost.

[ modification 1]

An electrochemical cell stack 100 according to modification 1 of the embodiment of the present disclosure will be described with reference to fig. 6 to 8. Fig. 6 is a side view showing an example of the structure of an electrochemical cell stack 100 according to modification 1 of the embodiment of the present disclosure. Fig. 7 is a perspective view showing an example of the structure of the electrochemical cell stack 100 shown in fig. 6. Fig. 8 is a cross-sectional view of the electrochemical cell unit 41 included in the electrochemical cell stack 100 shown in fig. 6. In fig. 6, the flow direction of the internal gas is shown by a broken-line arrow. In fig. 7, the flow direction of the internal gas and the exhaust gas of the internal gas is shown by broken line arrows, and the flow direction of the oxidant gas and the exhaust gas of the oxidant gas is shown by solid line arrows. Fig. 8 shows the cross-sectional shape when the electrochemical cell 41 is cut at the same B-B cross section as in fig. 4.

As shown in fig. 6 to 8, the electrochemical cell stack 100 according to modification 1 is configured to further include a gas recovery unit 44 in the electrochemical cell stack 100 according to the embodiment. The electrochemical cell stack 100 according to modification 1 has the same configuration as the electrochemical cell stack 100 according to the embodiment except that the gas recovery unit 44 is provided, and therefore the same members are denoted by the same reference numerals and the description thereof is omitted.

The gas recovery unit 44 recovers internal gas discharged from the gas introduction space 50 through the discharge unit 38 formed in the outer peripheral portion 39 of the electrochemical cell 41. That is, the gas recovery unit 44 is disposed at a position facing the mounting base unit 42, and fixes the other end portion of the electrochemical cell 41 fixed to the mounting base unit 42 on the opposite side from the one end portion.

As shown in fig. 8, the gas recovery unit 44 has a discharge-side fixing portion 48 formed of an electrically insulating member for fixing the other end portion of the electrochemical cell 41. The discharge-side fixing portion 48 has the same configuration as the fixing portion 43. That is, the discharge-side fixing portion 48 is constituted by a slit-shaped insertion portion 48a formed in the gas recovery portion 44 and a seal joint portion 48b joining the portion of the electrochemical cell 41 inserted into the insertion portion 48a to the gas recovery portion 44. At least the surface of the insertion portion 48a that contacts the electrochemical cell 41 and the seal joint portion 48b are formed of electrically insulating members. As the sealing joint portion 48b, a glass sealing agent or a ceramic adhesive agent that can achieve both electrical insulation and gas sealing between the gas recovery portion 44 and the electrochemical cell 41 can be exemplified. In the electrochemical cell stack 100 according to modification 1, at least the surface of the insertion portion 48a that contacts the electrochemical cell 41 in the structure of the gas recovery portion 44 is made of an electrically insulating member such as ceramic, but the entire gas recovery portion 44 may be made of an electrically insulating member.

The gas recovery unit 44 has a gas discharge path 47 that communicates with a gas introduction space 50 formed by the outer peripheral portion 39 through the discharge portion 38 and discharges to the outside an off-gas of the internal gas discharged from the gas introduction space 50. The exhaust gas of the internal gas discharged from the gas introduction space 50 through the discharge portion 38 flows through the gas discharge passage 47 and is guided to the outside of the electrochemical cell stack 100.

As shown in fig. 7, the electrochemical cell stack 100 according to modification 1 has a so-called double support beam support structure in which the electrochemical cell 41 is supported by both the mounting base portion 42 and the gas recovery portion 44. That is, the mounting base portion 42 is erected on one side, and the gas recovery portion 44 is erected on the other side. A plurality of electrochemical cells 41 may be arranged so as to be laterally spaced from each other.

As described above, in the electrochemical cell stack 100 according to modification 1, the electrochemical cells 41 can be supported by the double support beams because: the outer peripheral portion 39 of the electrochemical cell 41 and the interconnector 36 are made of metal, and absorb displacement of the membrane-electrode assembly 34 due to a temperature change, so that cracking does not occur. In addition, since the electrochemical cell 41 can be fixed and supported at both ends by the double support beam support structure, the structure of the electrochemical cell stack 100 according to modification 1 is strengthened.

As shown in fig. 7, an electrochemical cell stack 100 according to modification 1 is configured such that: the oxidizing gas is circulated between the electrochemical cells 41, the internal gas is supplied from one end of the mounting base portion 42 formed long in the stacking direction of the electrochemical cells 41, and the off gas of the internal gas is discharged from one end of the gas recovery portion 44 formed long in the stacking direction.

With such a configuration, the off gas of the internal gas discharged from the gas recovery unit 44 can be guided to an arbitrary place by using, for example, a pipe. Therefore, it is not necessary to provide a combustion portion directly above the discharge portion 38 of the electrochemical cell 41, and the degree of freedom in the arrangement of the electrochemical cell stack 100 and the degree of freedom in the design of the solid oxide fuel cell including the electrochemical cell stack 100 can be increased.

As shown in fig. 6 and 8, the internal gas, which is a part of the hydrogen contained in the gas introduction space 50 of the electrochemical cell 41 and is consumed by the electrochemical reaction of the membrane-electrode assembly 34, is discharged from the electrochemical cell 41 as an exhaust gas through the discharge unit 38. The exhaust gas discharged at this time becomes a lean hydrogen gas containing a large part of incombustible components such as water vapor and carbon dioxide. In particular, when the fuel utilization rate is set higher than the fuel utilization rate set in normal power generation, the concentration of hydrogen contained in the exhaust gas of the internal gas is reduced to the vicinity of the combustion limit. Further, due to fluctuations in the flow rate of the internal gas supplied to each electrochemical cell 41, fluctuations in the hydrogen concentration contained in the internal gas, and the like, the exhaust gas containing hydrogen at a concentration exceeding the combustion limit is also contained in the exhaust gas of the internal gas discharged from the electrochemical cell 41. Therefore, if the off-gas of the internal gas discharged from the discharge portion 38 of each electrochemical cell 41 is directly combusted together with the off-gas of the oxidizing gas, there may be cases where partial fire, incomplete combustion, or the like occurs.

Therefore, when the fuel utilization rate is set higher than that in the normal power generation, it is difficult to perform stable heating in a configuration in which the exhaust gas of the internal gas is directly combusted directly above the exhaust portion 38 and the combustion heat is used as a heat source such as a heating reformer. Therefore, when the combustion heat of the exhaust gas of the internal gas is used as a heat source for heating the reformer or the like, the system may be unstable.

However, in the electrochemical cell stack 100 according to modification 1, the other end of the plurality of electrochemical cells 41 is joined to the gas recovery portion 44, and the off gas of the internal gas discharged through the discharge portion 38 can be collected and homogenized in the gas recovery portion 44 and supplied to a combustor (not shown). Therefore, stable combustion can be maintained even when the fuel utilization rate is set high.

Modification example 2 and simulation analysis

An electrochemical cell stack 100 according to modification 2 of the embodiment of the present disclosure will be described with reference to fig. 9 and 10. Fig. 9 is a diagram schematically showing the cross-sectional shape of the electrochemical cell 41 and the flow of internal gas in the electrochemical cell stack 100 according to modification 2 of the present disclosure. Fig. 10 is a view schematically showing the cross-sectional shape of the electrochemical cell 41 and the flow of internal gas in which the width of the inflow portion 37 is different from that in modification 2 of the present disclosure.

Fig. 9 and 10 show the cross-sectional shape of the electrochemical cell 41 cut at the position C-C shown in fig. 1, and schematically show the numerical simulation results of the gas flow when the internal gas is supplied to the electrochemical cell 41 by arrows. Fig. 9 shows a case where the opening width of each of the inflow portion 37 and the discharge portion 38 is smaller than the width (i.e., the projected width) of the membrane-electrode assembly 34. On the other hand, fig. 10 shows a case where the opening width of each of the inflow portion 37 and the discharge portion 38 is larger than the width (i.e., the projected width) of the membrane-electrode assembly 34, unlike modification 2.

In fig. 9 and 10, a plurality of rectangular members are arranged in a row in the membrane-electrode assembly 34. It shows a cut-and-raised portion 60 formed on the 1 st current collecting portion 35 where the internal gas collides, diffuses, mixes, and the 1 st electrode layer 31 and the 1 st current collecting portion 35 are electrically connected. In fig. 9 and 10, the cut-and-raised portions 60 are arranged at equal intervals and have the same shape, but the present invention is not limited thereto.

As shown in fig. 9 and 10, in the structure of the electrochemical cell stack 100 according to the embodiment, the shape of the membrane-electrode assembly 34 having a square plate shape was changed to a circular plate shape, and studies were made. When the membrane-electrode assembly 34 is formed in a flat circular shape, the strength can be improved as compared with the membrane-electrode assembly 34 formed in a flat square shape. However, when the membrane-electrode assembly 34 is formed in a flat circular shape, if it is assumed that the internal gas flows straight from the inflow portion 37 to the discharge portion 38, the distance that flows over the 1 st electrode layer 31 becomes longer as the distance approaches the center of the circle. When the internal gas is made to flow straight from the inflow portion 37 to the discharge portion 38 in this manner, the distance of flow over the 1 st electrode layer 31 varies. Therefore, it is necessary to adopt a structure in which the internal gas is distributed as uniformly as possible on the 1 st electrode layer 31. The electrochemical cell stack 100 shown in fig. 9 and 10 has a structure in which the cut-and-raised portion 60 is provided in the first current collecting portion 35 to diffuse the internal gas in the gas introducing space 50.

According to the above-described configuration, in the electrochemical cell stack 100 according to modification 2, as shown in fig. 9, the opening width dimensions of the inflow portion 37 and the discharge portion 38 when the electrochemical cells 41 are viewed in plan in the stacking direction are set within the range of the projection width of the membrane-electrode assembly 34 in the flow direction of the internal gas. In other words, it is set that: when the electrochemical cell 41 is viewed in plan in the stacking direction, the opening width of each of the inflow portion 37 and the discharge portion 38 is within the width of the membrane-electrode assembly 34 perpendicular to the flow direction of the internal gas. The flow direction of the internal gas is from the inflow portion 37 to the discharge portion 38.

On the other hand, in the electrochemical cell stack 100 having a different projection width from that of modification 2, as shown in fig. 10, the opening width dimensions of the inflow portion 37 and the discharge portion 38 are set to be larger than the range of the projection width of the membrane-electrode assembly 34 in the flow direction of the internal gas.

Therefore, the following steps are carried out: in the electrochemical cell stack 100 shown in fig. 10, the flow rate of the internal gas flowing along the outer periphery of the membrane-electrode assembly 34 becomes large, and the internal gas cannot be efficiently supplied to the 1 st electrode layer 31. Specifically, as a result of the simulation analysis, the flow rate of the internal gas flowing through the circular portion (1 st electrode layer 31) was 81% of the total flow rate, and the flow rate of the internal gas flowing through the outer periphery of the circular portion (1 st electrode layer 31) was 19% of the total flow rate. That is, the internal gas passes through not only the 1 st electrode layer 31 where the flow rate is most required but also the outer periphery of the 1 st electrode layer 31 where the resistance is small, and is not uniformly supplied in the 1 st electrode layer 31. Therefore, an electrochemical reaction with good efficiency cannot be performed. In particular, when the fuel utilization rate is set higher than that in the normal power generation, hydrogen depletion occurs, which causes a failure.

In contrast, in the electrochemical cell stack 100 according to modification 2 shown in fig. 9, although the membrane-electrode assembly 34 is a circular shape in which a drift current is likely to occur as described above, the flow rate of the internal gas flowing through the circular portion (the 1 st electrode layer 31) was 99.2% of the total flow rate, and the flow rate of the internal gas flowing through the outer periphery of the circular portion was 0.8% of the total flow rate as a result of simulation analysis. From the results, it is understood that: by setting the opening width dimensions of the inflow portion 37 and the discharge portion 38 within the range of the projection width of the membrane-electrode assembly 34 in the flow direction of the internal gas, the internal gas can be supplied to the 1 st electrode layer 31 uniformly and efficiently. In particular, it is known that: it is preferable that the opening width of each of the inflow portion 37 and the discharge portion 38 is set to a range of not more than half the projection width of the membrane-electrode assembly 34 in the flow direction of the internal gas, and to a size that allows a necessary flow rate of the internal gas to flow through the gas introduction space 50.

As a result of a power generation experiment in which the electrochemical cell stack 100 according to modification example 2 was mounted on a solid oxide fuel cell, power generation was possible even when the fuel utilization rate was set to a high level (for example, about 85%). This is considered to be because: in the internal gas exhaust portion 38 having the lowest hydrogen concentration, by reducing the opening width of the exhaust portion 38, all the internal gas flowing through the gas introduction space 50 can be collected and exhausted. This effect can be obtained not only when the shape of the membrane-electrode assembly 34 is the circular shape described above but also when the membrane-electrode assembly is a square shape.

(method of manufacturing electrochemical cell)

Next, an example of a method for manufacturing the electrochemical cell stack 100 according to the embodiment will be described with reference to fig. 11 to 13. Fig. 11 is a flowchart illustrating an example of a method for manufacturing the electrochemical cell stack 100 according to the present disclosure. Fig. 12 is a diagram schematically illustrating the process carried out in step S1 illustrated in fig. 11. Fig. 13 is a diagram schematically illustrating the process carried out in step S2 illustrated in fig. 11.

As shown in fig. 11 and 12, first, the 1 st paste 49 is applied to the 1 st joining part 70 joining the outer peripheral part 39 and the surface of the electrolyte membrane 32 on the 2 nd electrode layer 33 side, and the 2 nd paste 46 having conductivity is applied to the 2 nd joining part 71 joining the surface of the 2 nd electrode layer 33 on the side where the 2 nd current collecting part 40 is provided and the 2 nd current collecting part 40 (step S1). The 1 st paste 49 is any paste selected from a glass sealing agent, a ceramic adhesive, and a silver solder.

Next, as shown in fig. 11 and 13, the outer peripheral portion 39 and the electrolyte membrane 32 are pressure-bonded to each other at the 1 st bonding portion 70, and the 2 nd electrode layer 33 and the 2 nd current collecting portion 40 are pressure-bonded to each other at the 2 nd bonding portion 71 (step S2). As shown in fig. 13, a load for joining the outer peripheral portion 39 and the electrolyte membrane 32 at the 1 st joint portion 70 is applied via a spacer (spacer)80 provided between the outer peripheral portion 39 and the 2 nd current collecting portion 40 in order to secure a region of the 2 nd current collecting portion 40 where the cut-and-raised portion 60 is formed. On the other hand, a load for joining the 2 nd electrode layer 33 and the 2 nd current collecting portion 40 at the 2 nd joining portion 71 is applied to the cut-and-raised portion 60 of the 2 nd current collecting portion 40. In the state where the 1 st joint 70 and the 2 nd joint 71 are pressure-bonded in step S2, the 1 st joint 70 and the 2 nd joint 71 are fired at 800 to 900 ℃ together to form the electrochemical cell 41 (step S3).

In this way, in step S3, since the 1 st joint 70 and the 2 nd joint 71 can be fired together, the process can be shortened as compared with a method in which firing is performed separately. When the electrochemical cell stack 100 is used in a solid oxide fuel cell, the operating temperature of the solid oxide fuel cell is about 600 to 800 ℃. Therefore, it is preferable that the firing temperature in step S3 be higher than the operating temperature of the solid oxide fuel cell and be equal to or lower than the temperature that the stainless steel member constituting the interconnector 36 and the outer peripheral portion 39 can withstand. That is, it is preferable to perform firing in a furnace at a temperature ranging from 800 to 900 ℃ (for a duration of about 20 minutes to 1 hour).

After the electrochemical cell 41 is formed as described above, the formed electrochemical cell 41 is joined to the fixing portion 43 (the 3 rd joining portion) of the mounting base portion 42. That is, a glass sealant or a ceramic adhesive is applied to the fixing portion 43 (the 3 rd joint portion) where the electrochemical cell 41 and the mounting base portion 42 are joined (step S4). The fixing portion 43 (No. 3 joint) is fired at a temperature lower than the firing temperature (800 to 900 ℃) of step S3 (step S5). The firing temperature in step S5 can be set to, for example, 100 to 200 ℃.

As described above, since the temperature of firing at the fixing portion 43 (the 3 rd joint) in step S5 is lower than the temperature of firing at the 1 st joint 70 and the 2 nd joint 71 in step S3, it is possible to suppress the 1 st paste of the 1 st joint 70 and the 2 nd paste of the 2 nd joint from being remelted at the time of firing at the fixing portion 43 (the 3 rd joint). Therefore, the 1 st to 3 rd joint portions can be joined reliably.

In the case of the electrochemical cell stack 100 according to the modification further including the gas recovery unit 44, one end of the formed electrochemical cell 41 is joined to the fixing portion 43 (the 3 rd joining portion) of the mounting base portion 42, and the other end is joined to the discharge-side fixing portion 48 of the gas recovery unit 44. That is, in step S4, the glass sealing agent or the ceramic adhesive is applied to the fixing portion 43 (the 3 rd joint portion) and the discharge-side fixing portion 48. Then, in the next step S5, the anchor 43 (No. 3 joint) and the discharge-side anchor 48 are fired together at a temperature (e.g., 100 to 200 ℃) lower than the firing temperature (e.g., 800 to 900 ℃) of the step S3.

Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions. Therefore, the foregoing description should be construed as exemplary only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and/or function may be varied substantially without departing from the spirit of the invention.

Industrial applicability

The electrochemical cell of the present disclosure can be widely applied to an electrochemical cell constituted by a plurality of electrochemical cells such as a solid oxide type electrolytic cell.

Description of the reference numerals

31 st electrode layer

32 electrolyte membrane

33 No. 2 electrode layer

34 electrode assembly

35 1 st collector

36 interconnection device

37 inflow part

38 discharge part

39 outer peripheral portion

40 nd 2 nd collector

41 electrochemical cell

42 mounting base part

43 fixed part

43a insertion part

43b sealing the joint

44 gas recovery unit

45 gas supply path

46 nd 2 nd paste

47 gas discharge path

48 discharge side fixing part

48a insertion part

48b sealing joint

49 1 st paste

50 gas introduction space

60 cut-and-raised part

70 st joint part

71 No. 2 joining part

80 spacer

100 electrochemistry

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Electrochemical cell, electrochemical cell stack, method for producing electrochemical cell, and method for producing electrochemical cell stack

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