KR20200036271A - Solid oxide fuel cell and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a solid oxide fuel cell and a manufacturing method thereof. The solid oxide fuel cell comprises: a cathode; and a current collector layer of a metal mesh material formed on the cathode. The current collector layer is formed only in a partial region including a region in contact with a gas inlet of the cathode. The present invention has an effect of reducing manufacturing costs.

Description

Solid oxide fuel cell and its manufacturing method {SOLID OXIDE FUEL CELL AND MANUFACTURING METHOD THEREOF}

The present application relates to a solid oxide fuel cell and its manufacturing method.

Recently, as the depletion of existing energy resources such as oil and coal is predicted, interest in energy that can replace them is increasing. As one of these alternative energies, fuel cells are particularly attracting attention due to advantages such as high efficiency, no emission of pollutants such as NOx and SOx, and abundant fuel used.

A fuel cell is a power generation system that converts chemical reaction energy of a fuel and an oxidant into electrical energy, and hydrocarbons such as hydrogen, methanol, and butane are used as fuel, and oxygen is used as an oxidant.

Fuel cells include polymer electrolyte fuel cells (PEMFC), direct methanol fuel cells (DMFC), phosphoric acid fuel cells (PAFC), alkaline fuel cells (AFC), molten carbonate fuel cells (MCFC), and solid oxide fuel And SOFCs.

In general, SOFC has a stack structure in which a plurality of unit cells (electrodes) and an anode (cathode) and an anode (anode) located on both sides of the electrolyte are stacked to generate high power. In order to combine the unit cells in a stack structure, an interconnect is used, and a current collector layer is inserted between the unit cells and the connection materials to improve the current collecting function. The current collecting layer serves to collect electricity generated in the cell where actual power generation occurs and to pass it to the next step.

The current collecting layer is a major component related to SOFC performance, and research on the current collecting layer has been continuously conducted, and in the case of a metal mesh mainly used as a material for the air current collector layer, the price is high, and the development of a manufacturing method to reduce it is high. This is a demand.

Korea Patent Publication No. 2012-0110787

This application intends to provide a solid oxide fuel cell and a method for manufacturing the same.

One embodiment of the present application,

Air cathode;

Anode;

An electrolyte layer provided between the air electrode and the fuel electrode; And

It includes a current collector layer of a metal mesh material formed on the opposite surface of the air electrode in contact with the electrolyte layer,

The current collector layer provides a solid oxide fuel cell that is formed only in a partial region including a region in contact with a gas inlet of the cathode.

In addition, another embodiment of the present application,

Forming a stack of a fuel electrode, an electrolyte layer, and an air electrode; And

Forming a current collecting layer by attaching a metal mesh to only a portion of the air electrode, on a surface opposite to the surface in contact with the electrolyte layer, including a region in contact with a gas inlet.

It provides a method for producing a solid oxide fuel cell comprising a.

In the solid oxide fuel cell according to an exemplary embodiment of the present application, metal ions are reduced and precipitated around the gas discharge portion to prevent the gas flow from being blocked.

In addition, since the expensive metal mesh is partially applied when forming the current collector layer, manufacturing cost is reduced.

1 is a view schematically showing a structure of a solid oxide fuel cell according to Comparative Examples and Examples.
2 is a view illustrating the interface between the cathode and the electrolyte layer using a scanning electron microscope (SEM) after operating the fuel cell of the comparative example for 3,000 hours.
3 is a view illustrating the interface between the cathode and the electrolyte layer by a scanning electron microscope (SEM) after operating the fuel cell of the embodiment for 3,000 hours.
4 is a diagram illustrating a region in which a current collector layer is formed according to an exemplary embodiment of the present application.
5 is a view schematically showing the principle of electricity generation of a solid oxide fuel cell.
FIG. 6 is a view showing a state in which a silver mesh is cut according to an exemplary embodiment of the present application.

Hereinafter, preferred embodiments of the present application will be described. However, the embodiments of the present application may be modified in various other forms, and the scope of the present application is not limited to the embodiments described below. In addition, the embodiments of the present application are provided to more fully describe the present application to those skilled in the art.

When a member is referred to as being “on” another member in the present specification, this includes not only the case where one member abuts another member, but also another member between the two members.

In the present specification, when a part “includes” a certain component, this means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

When metal ions are diffused in the metal mesh used as the material of the cathode current collector layer, this causes a change in the metal composition in the mesh, which not only lowers the durability of the current collector layer itself, but also precipitates metal by the reduction reaction of the metal ions. It can interfere with the flow. For example, looking at the case where the Ag mesh is introduced into the current collector layer as shown in FIG. 1, Ag diffused from the Ag mesh has a property of stabilizing with Ag oxide, so in the gas inlet where air is injected It will exist in a state of being bound with oxygen. However, the gas discharge portion (Gas outlet) when the potential of the electron around the Ag ⁺ ions are increased to meet the electronic silver deposited on the outer casing emissions can interfere with the flow of gas ^{(Ag + + 2e - → Ag} ).

Accordingly, the inventors of the present invention have solved the problem of silver precipitation by not forming an Ag mesh in the vicinity of the gas outlet as shown in the right figure of FIG. 1, and also reduced the process cost by reducing the amount of metal mesh used.

A solid oxide fuel cell according to an exemplary embodiment of the present application includes an anode; Anode; An electrolyte layer provided between the air electrode and the fuel electrode; And a current collector layer formed of a metal mesh material formed on an opposite surface of the air electrode in contact with the electrolyte layer, and the current collector layer includes a region in contact with a gas inlet of the air electrode. It is only formed. That is, a current collecting layer forming region and a current collecting layer non-forming region exist on the air electrode.

In one embodiment of the present application, the part means 10% to 80% of the total area of the cathode, preferably 30% to 50%. When the current collector layer is formed with an area of less than 10% of the total area of the cathode, the electron potential distribution becomes uneven due to the absolute decrease in the contact area, which can adversely affect electrode performance, and when it exceeds 80%, silver is reduced. There is a problem that the effect of the present invention to prevent the phenomenon of precipitation is negligible.

In one embodiment of the present application, the current collecting layer may be formed to include a region contacting a gas outlet. Specifically, as shown in FIG. 4, the current collector layer may be formed in a region in contact with the outside, including the gas discharge portion of the entire area of the cathode. If all the current collecting layers in the region contacting the gas outlet are removed, the electron potential distribution may be adversely affected.

In one embodiment of the present application, the mesh means that the metal wires cross each other and are formed in a lattice form, and the wire diameter and wire height of the metal wire are preferably 0.1 mm to 0.2 mm. . The grid includes 50 to 70 per square inch.

In one embodiment of the present application, the current collecting layer of the metal mesh material may be made of Ag mesh or Pt mesh, and preferably made of Ag mesh. Ag mesh has the advantage of low cost compared to other precious metal meshes.

In one embodiment of the present application, the thickness of the cathode may be 10 μm to 100 μm, preferably 30 μm to 70 μm, and more preferably 40 μm to 50 μm.

When the thickness of the cathode is included in the above range, it is possible to sufficiently secure a reaction area and at the same time reduce the cost.

In one embodiment of the present application, the porosity of the cathode may be 10% to 70%, preferably 20% to 50%, more preferably 30% to 40%.

When the porosity of the cathode is included in the above range, it is possible to prevent the problem of increasing the concentration polarization in gas diffusion due to excessive density, and has the advantage of ensuring adequate durability.

The pore diameter of the cathode may be 1 μm to 10 μm, and preferably 3 μm to 5 μm.

When the diameter of the pores of the cathode is included in the above range, there is an advantage that durability can be secured while reducing gas diffusion resistance.

In one embodiment of the present application, the cathode may include an inorganic material having oxygen ion conductivity. The inorganic material is yttria stabilized zirconium oxide (zirconia) (YSZ: (Y ₂ O ₃ ) _x (ZrO ₂ ) _1-x , x = 0.05 to 0.15), scandia stabilized zirconium oxide (ScSZ: (Sc ₂ O ₃ ) _x (ZrO ₂ ) _1-x , x = 0.05 ~ 0.15), samarium dope ceria (SDC: (Sm ₂ O ₃ ) _x (CeO ₂ ) _1-x , x = 0.02 ~ 0.4), gadolinium Dope ceria (GDC: (Gd ₂ O ₃ ) _x (CeO ₂ ) _1-x , x = 0.02 to 0.4), Lanthanum strontium manganese oxide (LSM), Lanthanum strontium cobalt ferrite (Lanthanum strontium cobalt ferrite (LSCF), Lanthanum strontium nickel ferrite (LSNF), Lanthanum calcium nickel ferrite (LCNF), Lanthanum strontium cobalt oxide (LSC) gadolinium strontium cobaltium oxide (GSC) strontium cobalt oxide (GSC), Lanthanum strontium ferrite (LSF), Samarium strontium cobalt acid It may include at least one of cargo (Samarium strontium cobalt oxide: SSC), Barium Strontium cobalt ferrite (BSCF), and Lanthanum strontium gallium magnesium oxide (LSGM).

The cathode comprises at least one of Lanthanum strontium cobalt ferrite (LSCF), Lanthanum strontium cobalt oxide (LSC) and Barium Strontium cobalt ferrite (BSCF), electrolyte It may further include the same inorganic material as the metal oxide. Specifically, when the electrolyte contains a ceria-based metal oxide, the cathode may further include a ceria-based metal oxide. More specifically, when the electrolyte includes gadolinium dope ceria (GDC), the cathode may further include gadolinium dope ceria (GDC).

In one embodiment of the present application, the cathode includes lanthanum strontium cobalt ferrite (LSCF), gadolinium dope ceria (GDC), and lanthanum strontium cobalt oxide (LSC).

The manufacturing method of the cathode is not particularly limited, for example, coating and drying and calcining the slurry for the cathode, or coating and drying the slurry for the cathode on a separate release paper to prepare a green sheet for the cathode, one or more An air cathode green sheet can be produced by firing alone or with a neighboring heterogeneous green sheet.

The cathode slurry includes inorganic particles having oxygen ion conductivity, and if necessary, the cathode slurry may further include at least one of a binder resin, a plasticizer, a dispersant, and a solvent. The binder resin, plasticizer, dispersant and solvent are not particularly limited, and conventional materials known in the art may be used.

The thickness of the green sheet for the cathode may be 10 μm or more and 100 μm or less.

Based on the total weight of the slurry for the cathode, the content of the inorganic particles having oxygen ion conductivity is 40% by weight or more and 70% by weight or less, the content of the solvent is 10% by weight or more and 30% by weight or less, and the content of the dispersant is 5% by weight or more and 10% by weight or less, the content of the plasticizer is 0.5% by weight or more and 3% by weight or less, and the binder may be 10% by weight or more and 30% by weight or less.

In an exemplary embodiment of the present application, the thickness of the current collector layer may be 100 μm to 500 μm, and preferably 300 μm to 400 μm, but is not limited thereto.

When the thickness of the current collector layer is included in the above range, there is an effect of sufficiently adhering to the air electrode.

FIG. 5 schematically shows the electricity generation principle of a solid oxide fuel cell, and the solid oxide fuel cell is composed of an electrolyte layer and an anode and a cathode formed on both sides of the electrolyte layer. do. Referring to FIG. 5, as air is electrochemically reduced at the cathode, oxygen ions are generated and the generated oxygen ions are transferred to the anode through the electrolyte layer. At the anode, fuel such as hydrogen, methanol, butane, etc. is injected, and the fuel is combined with oxygen ions to electrochemically oxidize and release electrons to generate water. The reaction causes electron movement to occur in the external circuit.

In one embodiment of the present application, the anode may include an inorganic material having oxygen ion conductivity. The inorganic material is yttria stabilized zirconium oxide (zirconia) (YSZ: (Y ₂ O ₃ ) _x (ZrO ₂ ) _1-x , x = 0.05 to 0.15), scandia stabilized zirconium oxide (ScSZ: (Sc ₂ O ₃ ) _x (ZrO ₂ ) _1-x , x = 0.05 ~ 0.15), samarium dope ceria (SDC: (Sm ₂ O ₃ ) _x (CeO ₂ ) _1-x , x = 0.02 ~ 0.4) and gadolinium Dope ceria (GDC: (Gd ₂ O ₃ ) _x (CeO ₂ ) _1-x , x = 0.02 ~ 0.4).

The thickness of the anode may be 10 μm to 1,000 μm. Specifically, the thickness of the anode may be 100 μm to 800 μm.

The porosity of the anode may be 10% to 50%. Specifically, the porosity of the anode may be 10% to 30%.

The pore diameter of the anode may be 0.1 μm to 10 μm. Specifically, the pore diameter of the anode may be 0.5 μm to 5 μm. More specifically, the pore diameter of the anode may be 0.5 μm to 2 μm.

The manufacturing method of the anode is not particularly limited, for example, coating and drying and firing the slurry for the anode, or coating and drying the anode slurry on a separate release paper to prepare a green sheet for the anode, and at least one anode For the green sheet alone or by firing with a green sheet of an adjacent layer, an anode can be produced.

The thickness of the green sheet for the anode may be 10 μm to 500 μm.

The anode slurry includes inorganic particles having oxygen ion conductivity, and if necessary, the anode slurry may further include at least one of a binder resin, a plasticizer, a dispersant, and a solvent, and the binder resin, a plasticizer, a dispersant, and The solvent is not particularly limited, and conventional materials known in the art may be used.

Based on the total weight of the slurry for the anode, the content of the inorganic particles having oxygen ion conductivity is 10% by weight to 30% by weight, the content of the solvent is 10% by weight to 30% by weight, and the content of the dispersant is 5% by weight % To 10% by weight, the content of the plasticizer is 0.5% to 3% by weight, the content of the binder may be 10% to 30% by weight.

The anode slurry may further include NiO. Based on the total weight of the slurry for the anode, the content of NiO may be 10% to 30% by weight.

The anode may be provided on a separate porous ceramic support or a porous metal support, or may include an anode support and an anode functional layer. At this time, the anode support is a layer containing the same inorganic material as the anode functional layer, but having a higher porosity and relatively thicker thickness than the anode functional layer, and supporting the other layer. The anode functional layer is provided between the anode support and the electrolyte layer. It may be a layer that plays a major role as an actual anode.

When the anode is provided on the porous ceramic support or the porous metal support, the green sheet for the prepared anode can be laminated on the fired porous ceramic support or the porous metal support and fired to produce the anode.

When the anode includes an anode support and an anode functional layer, a green sheet for the prepared anode functional layer can be laminated on the calcined anode support and fired to produce an anode.

When the anode includes an anode support and an anode functional layer, the thickness of the anode support may be 350 μm to 1,000 μm, and the thickness of the anode functional layer may be 5 μm to 50 μm.

The electrolyte layer may include an oxygen ion conductive inorganic material, and is not particularly limited as long as it has oxygen ion conductivity. Specifically, the oxygen ion conductive inorganic material of the electrolyte layer may include a composite metal oxide containing at least one selected from the group consisting of zirconium oxide, cerium oxide, lanthanum oxide, titanium oxide, and bismuth oxide based materials. You can. More specifically, the oxygen ion conductive inorganic material of the electrolyte layer is yttria stabilized zirconium oxide (YSZ: (Y ₂ O ₃ ) _x (ZrO ₂ ) _1-x , x = 0.05 to 0.15), Scandia Stabilized zirconium oxide (ScSZ: (Sc ₂ O ₃ ) x (ZrO ₂ ) _1-x , x = 0.05 ~ 0.15), samarium dope ceria (SDC: (Sm ₂ O ₃ ) x (CeO ₂ ) 1- x, x = 0.02 to 0.4) and gadolinium dope ceria (GDC: (Gd ₂ O ₃ ) x (CeO ₂ ) 1-x, x = 0.02 to 0.4).

The thickness of the electrolyte layer may be 10㎛ to 100㎛. Specifically, the thickness of the electrolyte layer may be 20㎛ to 50㎛.

The manufacturing method of the electrolyte layer is not particularly limited, for example, coating the slurry for the electrolyte layer to dry and calcining it, or coating and drying the slurry for the electrolyte layer on a separate release paper to prepare a green sheet for the electrolyte layer, and the electrolyte The green sheet for a layer can be calcined either alone or together with a green sheet of neighboring layers to produce an electrolyte layer.

The thickness of the green sheet for the electrolyte layer may be 10 μm to 100 μm.

The slurry for the electrolyte layer includes inorganic particles having oxygen ion conductivity, and if necessary, the slurry for the electrolyte layer may further include at least one of a binder resin, a plasticizer, a dispersant, and a solvent, and the binder resin, a plasticizer, a dispersant, and The solvent is not particularly limited, and conventional materials known in the art may be used.

Based on the total weight of the slurry for the electrolyte layer, the content of the inorganic particles having oxygen ion conductivity may be 40% to 70% by weight.

Based on the total weight of the slurry for the electrolyte layer, the content of the solvent is 10% to 30% by weight, the content of the dispersant is 5% to 10% by weight, the content of the plasticizer is 0.5% to 3% by weight, and the binder The content of may be 10% by weight to 30% by weight.

In the present specification, the green sheet refers to a film in the form of a film that can be processed in the next step, not a complete final product. In other words, the green sheet is coated with a coating composition containing inorganic particles and a solvent and dried in a sheet form, and the green sheet refers to a sheet in a semi-dry state that can maintain a sheet form while containing a little solvent.

The shape of the fuel cell is not limited, and may be, for example, coin, flat, cylindrical, horn, button, sheet or stacked.

A method of manufacturing a solid oxide fuel cell according to an exemplary embodiment of the present application includes forming a stack of an anode, an electrolyte layer, and an anode; And forming a current collecting layer by attaching a metal mesh to only a part of the area including a region in contact with a gas inlet on a surface opposite to the surface of the cathode that contacts the electrolyte layer; And removing a portion of the current collector layer in contact with a gas outlet.

In an exemplary embodiment of the present application, the forming of the laminate may include laminating an anode and an electrolyte layer prepared by the above-described method, and applying and drying the slurry for the cathode to the electrolyte layer.

In an exemplary embodiment of the present application, the method for manufacturing the solid oxide fuel cell may use the metal mesh 10% to 80% of the total area of the current collector layer, preferably 30% to 50% before forming the current collector layer. It may further include the step of cutting the area.

The cutting may be performed by stacking the metal mesh in multiple layers and cutting it as shown in FIG. 4 using a cutting device having a rectangular frame.

In one embodiment of the present application, the attachment may be performed using a strong adhesive, specifically a cyanoacrylate-based adhesive, but is not limited thereto.

In one embodiment of the present application, the metal mesh from which some areas are removed through cutting may be first attached to a rib that is part of an interconnect, and then attached to a cathode.

The method for manufacturing a solid oxide fuel cell according to an exemplary embodiment of the present application may cite the description of each configuration of the above-described solid oxide fuel cell.

Hereinafter, the present specification will be described in more detail through examples. However, the following examples are only intended to illustrate the present specification and are not intended to limit the present specification.

<Example: Preparation of SOFC>

Comparative example.

The solid oxide fuel cell used for the measurement was prepared with an anode support layer (ASL), an anode functional layer (AFL), an electrolyte layer (EL), and a cathode (CL, cathode layer).

The ASL slurry uses YSZ, NiO, and Carbon Black as inorganic materials, wherein the ratio of YSZ and NiO is 50:50 vol%, and based on the total weight of the slurry, carbon black is composed of 10 wt%.

In addition, the ASL slurry was added with a dispersant, a plasticizer, and a binder resin with a solvent, based on the total weight of the slurry, 23 wt% of a solvent, 6 wt% of a dispersant, 0.8 wt% of a plasticizer, and 19 wt% of a binder. The ASL slurry was tape-casted to obtain an ASL Green Sheet having a thickness of 100 μm to 200 μm.

The AFL slurry was the same as the ASL slurry and the organic material, but the composition ratio of YSZ and NiO was 60:40 vol% and carbon black was not included, and 20 μm thick AFL green sheet thinner than ASL was cast using this.

The EL slurry is the same as the ASL slurry and the organic material, but is composed of inorganic materials only with YSZ and GDC without NiO and carbon black, and using this, an EL green sheet having a thickness of 20 µm was cast.

Half cells were prepared by sequentially laminating ASL green sheets, AFL green sheets, and EL green sheets, followed by primary sintering at 1,220 ° C to 1,260 ° C and secondary sintering at 1,330 ° C to 1,370 ° C. At this time, the thicknesses of the ASL, AFL, and EL after sintering were 630 μm, 15 μm to 25 μm, and 5 μm to 15 μm, respectively.

Based on the total weight of the total composition, LG64 (LSCF6428 (La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ ): GDC (Ce _0.9 Gd _0.1 O _2-δ ) = 60wt%: 40wt%) is 60wt%, binder composition LG64 air cathode composition containing 40 wt% phosphorus ESL441 was prepared in a paste form using a 3 roll mill to prepare an LG64 air cathode composition.

On the electrolyte layer of the half cell prepared above, the LG64 cathode composition is applied by a screen printing method and dried, then two layers of LSC64 (La0.6Sr0.4CoO _3-δ ) are applied and dried, followed by heat treatment at 1,100 ℃ To form an air cathode. At this time, the area of the formed air electrode was 9 cm × 9 cm.

To the prepared fuel cell, nickel foam, which is an anode current collecting layer, was fixed to the cell using an adhesive.

On the cathode side of the manufactured fuel cell, a silver mesh (Nanotech Co., Ltd.) of 9 cm x 9 cm, which is an anode current collector layer, was attached to the cathode by applying an adhesive (Henkel Co., Loctite 401) and fixing it.

Example.

In the comparative example, by cutting the silver mesh as shown in FIG. 6 using a rectangular frame cutting machine, only 70% of the portion in contact with the gas inlet was left, and then attached in the same manner as in the comparative example. A fuel cell was prepared.

<Experimental Example: Performance evaluation of SOFC>

The SOFCs prepared in the Comparative Examples and Examples were operated for 3,000 hours under a current density of 500 mA / cm ² , respectively, and then the cathode and electrolyte interfaces were taken with a scanning electron microscope (SEM), respectively, and FIG. 2 (Comparative Example) and Attached to Figure 3 (Example). In the case of Figure 2, it can be seen that silver precipitated near the interface between the cathode and the electrolyte, which is a reduction of silver ions in the vicinity of the gas outlet. In the case of FIG. 3, since the current collecting layer in the vicinity of the gas discharge portion was removed, it can be confirmed that silver precipitation did not occur.

In conclusion, it has been proved that the solid oxide fuel cell according to an exemplary embodiment of the present application has an effect of improving durability while reducing the amount of silver mesh used.

Claims (9)

Air cathode;
Anode;
An electrolyte layer provided between the air electrode and the fuel electrode; And
It includes a current collector layer of a metal mesh material formed on the opposite surface of the air electrode in contact with the electrolyte layer,
The current collector layer is a solid oxide fuel cell that is formed only in a part of the region including a region in contact with a gas inlet of the cathode. The method according to claim 1,
The portion of the solid oxide fuel cell is 10% to 80% of the total area of the cathode. The method according to claim 1,
The current-conducting layer of the metal mesh material is made of Ag mesh. The method according to claim 1,
The current collector layer is a solid oxide fuel cell formed by including a region in contact with a gas outlet. Forming a stack of a fuel electrode, an electrolyte layer, and an air electrode; And
Forming a current collecting layer by attaching a metal mesh to only a portion of the air electrode, on a surface opposite to the surface in contact with the electrolyte layer, including a region in contact with a gas inlet.
Method of manufacturing a solid oxide fuel cell comprising a. The method according to claim 5,
A method of manufacturing a solid oxide fuel cell further comprising cutting the metal mesh to an area of 10% to 80% of the total area of the current collecting layer before forming the current collecting layer. The method according to claim 5,
The attachment is a method of manufacturing a solid oxide fuel cell that is performed using a cyanoacrylate-based adhesive. The method according to claim 6,
The metal mesh is a method of manufacturing a solid oxide fuel cell that is Ag mesh. The method according to claim 6,
The current collector layer is a method of manufacturing a solid oxide fuel cell that is formed to include a region in contact with a gas outlet (Gas outlet).

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