KR20190089324A - Solid oxide fuel cell and manufacturing method thereof - Google Patents

Abstract

One embodiment of the present invention provides a method for manufacturing a solid oxide fuel cell comprising an anode, a cathode, and an electrolyte layer provided between the anode and the cathode. The method comprises a step of forming the cathode using slurry comprising a mixture of a compound represented by chemical formula 1 and Co oxide on the electrolyte layer. The chemical formula 1 is represented by: Ba_1-xSr_xB_1-yB′_yO_3±δ. According to the present invention, the durability of the solid oxide fuel cell can be enhanced.

Description

SOLID OXIDE FUEL CELL AND MANUFACTURING METHOD THEREOF FIELD OF THE INVENTION [0001]

The present invention relates to a solid oxide fuel cell including an anode, a cathode, and an electrolyte layer provided between the anode and the cathode, and a method of manufacturing the same.

Recently, as the exhaustion of existing energy resources such as oil and coal is predicted, interest in energy that can replace them is increasing. As one of such alternative energies, fuel cells have attracted particular attention due to their advantages such as high efficiency, no emission of pollutants such as NOx and SOx, and abundant fuel.

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

BACKGROUND ART Fuel cells include a polymer electrolyte fuel cell (PEMFC), a direct methanol fuel cell (DMFC), a phosphoric acid fuel cell (PAFC), an alkaline fuel cell (AFC), a molten carbonate fuel cell (MCFC) And a battery (SOFC).

It is also necessary to study a metal air secondary battery using a cathode of a metal secondary battery as an air electrode by applying the principle of a cathode of a fuel cell.

Korean Patent Laid-Open Publication No. 2012-0110787

The present application is directed to a solid oxide fuel cell including an anode, a cathode, and an electrolyte layer provided between the anode and the cathode, and a method of manufacturing the same.

In one embodiment of the present application,

A method of manufacturing a solid oxide fuel cell comprising an anode, a cathode, and an electrolyte layer provided between the anode and the cathode,

And forming a cathode on the electrolyte layer using a slurry containing a mixture of a compound represented by the following formula (1) and a Co oxide.

[Chemical Formula 1]

Ba _{1 - x} Sr _x B _{1 - y} B ' _y O _{3 隆}

In Formula 1,

B and B 'are different from each other and selected from Mn, Fe, Co, Ni, Cu, Ti, Nb,

0 < x? 1, 0? Y? 1, 0?

Further, another embodiment of the present application,

A solid oxide fuel cell comprising an anode, a cathode, and an electrolyte layer disposed between the anode and the cathode,

Wherein the cathode comprises a mixture of a compound represented by Formula 1 and a Co oxide.

The solid oxide fuel cell according to one embodiment of the present application is characterized in that durability can be improved by forming a cathode using a mixture of the compound represented by Formula 1 and Co oxide. In particular, the Co oxide prevents the decomposition of Sr in formula (1), thereby improving the durability of the solid oxide fuel cell.

In addition, the solid oxide fuel cell according to one embodiment of the present application has an advantage that the interface between the electrolyte and the cathode is stable.

In addition, the solid oxide fuel cell according to one embodiment of the present application has an advantage of having high battery performance with reproducibility.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an electricity generation principle of a solid oxide fuel cell. FIG.
2 schematically shows an embodiment of a battery module including a fuel cell.
3 is a SEM photograph showing an interface between a conventional LSCF cathode and a GDC electrolyte layer.

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

In this specification, when a part is referred to as "including " an element, it is to be understood that it may include other elements as well, without departing from the other elements unless specifically stated otherwise.

Generally, a cathode of a solid oxide fuel cell (SOFC) is a perovskite material of ABO ₃ structure. At this time, high electrical conductivity can be expected by doping the A site with the element Sr to generate oxygen defects which become channels for electron transfer.

However, since such a material has an unstable property of decomposing Sr at high temperature, it may cause a serious durability problem due to the characteristics of an SOFC driven at 600 to 800 ° C. In fact, in a previous study evaluating long-term durability, it was confirmed that needle-shaped strontium oxide (Strontium Oxide) was formed at the interface between the LSCF cathode and the electrolyte layer as shown in FIG.

In the present application, strontium oxide (Strontium Oxide) and cobalt oxide, which forms a stable perovskite phase, are included in the cathode of the solid oxide fuel cell to solve the durability problem.

1 schematically shows an electricity generation principle of a solid oxide fuel cell. The solid oxide fuel cell includes an electrolyte layer and an anode and a cathode formed on both surfaces of the electrolyte layer. do. 1 showing the principle of electricity generation of a solid oxide fuel cell, air is electrochemically reduced at the cathode to generate oxygen ions, and the generated oxygen ions are transferred to the anode through the electrolyte layer. In the anode, fuel such as hydrogen, methanol, butane, etc. is injected and the fuel is combined with oxygen ions and electrochemically oxidized to generate electrons to generate water. This reaction causes electrons to migrate to the external circuit.

A manufacturing method of a solid oxide fuel cell according to an embodiment of the present application is a manufacturing method of a solid oxide fuel cell including an anode, a cathode, and an electrolyte layer provided between the anode and the cathode, And forming a cathode using a slurry comprising a mixture of a compound represented by the following formula (1) and a Co oxide.

[Chemical Formula 1]

Ba _{1 - x} Sr _x B _{1 - y} B ' _y O _{3 隆}

In Formula 1,

B and B 'are different from each other and selected from Mn, Fe, Co, Ni, Cu, Ti, Nb,

0 < x? 1, 0? Y? 1, 0?

In one embodiment of the present application, the content of the Co oxide may be 1 to 10% by weight, and 3 to 7% by weight, based on the total weight of the compound represented by the formula (1). It is difficult to confirm the quantitative ratio of Sr oxide decomposed from the cathode by long-term driving. However, when the Co oxide is included in the above range, the Sr oxide is trapped, thereby deteriorating the performance. However, when the content of the Co oxide is out of the above range, the three-phase interface (TPB) of the cathode, which is a site where an electrochemical reaction occurs, may be blocked and adversely affect the performance.

In one embodiment of the present application, the compound (BSCF) represented by the above formula (1) as a cathode has a high oxygen diffusion coefficient and can be expected to have superior performance over the conventional LSCF. As a result of measuring the ASR of the symmetry cell using the LSCF and BSCF cathodes containing 5 wt% of Co oxide, the cathode of the present invention showed a better value at 650 ° C at 1.99 and 0.52 ohm x cm ² , respectively It looked.

In one embodiment of the present application, the Co oxide may be CoO or Co ₃ O ₄ . Since the CoO is converted to Co ₃ O ₄ in the range of 600 to 700 ° C. in the air atmosphere, the Co oxide may exist in the form of Co ₃ O ₄ at the operating temperature of the SOFC of the middle-low temperature.

In one embodiment of the present application, the average particle size of the compound (BSCF) and the Co oxide represented by the formula (1) may be 3.27 탆 and 3.87 탆, respectively, and 25.4 S / cm and 3.35 S / cm It can have electrical conductivity.

In one embodiment of the present application, B in the above formula (1) is Co and B 'is more preferably Fe. In the present invention, the more preferable composition of formula (1) is the same as x = 0.5 and y = 0.2.

In one embodiment of the present application, the slurry comprising the mixture of the compound represented by Formula 1 and the Co oxide may further include a binder resin and a solvent. In addition, the slurry may further include a plasticizer and a dispersant if necessary. Here, the binder resin, plasticizer, dispersant and solvent are not particularly limited, and conventional materials known in the art can be used.

The solid content of the slurry is 64.4% by weight. The solid content of the slurry may be 95% by weight of the compound represented by the formula (BSCF) and 5% by weight of the Co oxide. The binder resin, the plasticizer and the solvent may each contain 22.7% by weight of an ethyl cellulose binder solution, 5.2% by weight of dibutyl phthalate, and 7.7% by weight of butyl carbitol.

In one embodiment of the present application, in addition to the step of forming the cathode, materials and methods known in the art can be used for forming the anode, the electrolyte layer, and the like.

The anode may include an inorganic substance having oxygen ion conductivity so as to be applicable to an anode for a solid oxide fuel cell. Of the inorganic type it is not particularly limited, and the inorganic material is yttria (yttria) zirconium stabilized oxide (zirconia) (YSZ: (Y 2 O 3) x (ZrO 2) 1-x, x = 0.05 ~ 0.15), scandia It stabilized zirconia _{(ScSZ: (Sc 2 O 3} ) x (ZrO 2) 1-x, x 0.05 ~ 0.15), samarium-doped ceria (ceria) (SDC: (Sm 2 O 3) x (CeO 2) 1-x , x = 0.02 to 0.4) and gadolinium doped ceria (GDC: (Gd ₂ O ₃ ) _x (CeO ₂ ) _1-x , x = 0.02 to 0.4).

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

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

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

The method for producing the anode is not particularly limited. For example, the anode slurry is coated and dried and fired, the anode slurry is coated on a separate release paper and dried to prepare an anode green sheet, The anode can be fired together with the green sheet for the green sheet or the green sheet for the neighboring layer.

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

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, the plasticizer, The solvent is not particularly limited, and conventional materials known in the art can be used.

Wherein the content of the inorganic particle having oxygen ion conductivity is 10 wt% to 30 wt%, the content of the solvent is 10 wt% to 30 wt%, the content of the dispersant is 5 wt% % To 10 wt%, the plasticizer content is 0.5 wt% to 3 wt%, and the binder content is 10 wt% to 30 wt%.

The anode slurry may further include NiO. The content of the NiO may be 10 wt% to 30 wt% based on the total weight of the anode slurry.

The anode may be provided on a separate porous ceramic support or porous metal support, or it may comprise 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 supporting another layer having a higher porosity and relatively thicker thickness than the anode functional layer, and the anode functional layer is provided between the anode support and the electrolyte layer It may be a layer which is mainly running as the anode.

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

When the anode includes the anode support and the anode functional layer, the anode can be manufactured by laminating the green sheet for the anode functional layer on the fired anode support and then firing the green sheet.

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

The electrolyte layer may contain an oxygen ion conductive inorganic substance and is not particularly limited as long as it has oxygen ion conductivity. Specifically, the oxygen ion conductive inorganic material of the electrolyte layer includes a composite metal oxide including at least one selected from the group consisting of a zirconium oxide-based material, a cerium oxide-based material, a lanthanum oxide-based material, a titanium oxide-based material, and a bismuth oxide- . More particularly, the oxygen ion conductive inorganic material of the electrolyte layer are yttria (yttria) stabilized zirconium oxide (zirconia) (YSZ: (Y 2 O 3) x (ZrO 2) 1-x, x = 0.05 ~ 0.15), scandia Stabilized zirconium oxide (ScSZ: (Sc ₂ O ₃ ) x (ZrO ₂ ) _{1 -x} , x = 0.05 to 0.15), samarium doped ceria (SDC: (Sm ₂ O ₃ ) x (CeO ₂ ) x, x = 0.02 to 0.4) and gadolinium doped 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 from 10 탆 to 100 탆. Specifically, the thickness of the electrolyte layer may be 20 占 퐉 to 50 占 퐉.

The method for producing the electrolyte layer is not particularly limited. For example, a method of coating a slurry for an electrolyte layer, drying and firing the slurry for the electrolyte layer, or coating a slurry for an electrolyte layer on a separate release paper to dry the electrolyte layer, The green sheet for layer may be fired together with the green sheet of the layer for the layer alone or an adjacent layer to prepare the electrolyte layer.

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

The slurry for an electrolyte layer may include inorganic particles having oxygen ion conductivity. 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. The binder resin, the plasticizer, The solvent is not particularly limited, and conventional materials known in the art can be used.

The content of the inorganic particle having oxygen ion conductivity may be 40 wt% to 70 wt% based on the total weight of the slurry for the electrolyte layer.

Wherein the content of the solvent is 10 wt% to 30 wt%, the content of the dispersant is 5 wt% to 10 wt%, the content of the plasticizer is 0.5 wt% to 3 wt% based on the total weight of the slurry for the electrolyte layer, May be 10 wt% to 30 wt%.

In this specification, the green sheet means a film in the form of a film in a state where it can be processed in the next step, which is 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 semi-dry sheet capable of maintaining a sheet form while containing a slight amount of solvent.

The solid oxide fuel cell according to one embodiment of the present application is a solid oxide fuel cell comprising an anode, a cathode, and an electrolyte layer provided between the anode and the cathode, wherein the cathode contains the compound And a mixture of Co oxides.

The cathode layer, which is the final product, has a porous structure and may have a thickness of 10 to 50 탆. The compound (BSCF) and the Co oxide represented by the formula (1) in the cathode may exist in a uniformly mixed composite form.

The shape of the fuel cell is not limited, and may be, for example, a coin, a flat plate, a cylinder, a horn, a button, a sheet or a laminate.

The fuel cell may be specifically used as a power source for an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage device.

The present specification provides a battery module including a fuel cell as a unit cell.

2 schematically shows an embodiment of a battery module including a fuel cell, wherein the fuel cell includes a battery module 60, an oxidizer supply portion 70, and a fuel supply portion 80. [

The battery module 60 includes one or more than one of the above-described fuel cells as a unit cell, and includes a separator interposed therebetween when two or more unit cells are included. The separator prevents the unit cells from being electrically connected and transmits the fuel and the oxidant supplied from the outside to the unit cell.

The oxidant supply unit 70 serves to supply the oxidant to the battery module 60. As the oxidizing agent, oxygen is typically used, and oxygen or air can be injected into the oxidizing agent supplying portion 70 and used.

The fuel supply unit 80 serves to supply fuel to the battery module 60 and includes a fuel tank 81 for storing fuel and a pump 82 for supplying the fuel stored in the fuel tank 81 to the battery module 60 ). As the fuel, gas or liquid hydrogen or hydrocarbon fuel may be used. Examples of hydrocarbon fuels include methanol, ethanol, propanol, butanol or natural gas.

Hereinafter, the present invention will be described in more detail by way of examples. However, the following embodiments are intended to illustrate the present disclosure and are not intended to limit the present disclosure.

< Example >

< Example  1>

1. Electrolyte / anode slurry production step

50% by weight of GDC, 10% by weight of a dispersant, 1% by weight of a plasticizer and 10% by weight of an acrylic binder were mixed with the remaining solvent to prepare an electrolyte slurry.

30% by weight of GDC, 30% by weight of NiO, 10% by weight of dispersant, 3% by weight of plasticizer and 10% by weight of acrylic binder were mixed with the remaining solvent to prepare an anode functional layer slurry. The anode support layer slurry also contains 20 wt% of GDC, 20 wt% of NiO, 10 wt% of pore former, 10 wt% of dispersant, 10 wt% of plasticizer, and 30 wt% of acrylic binder with the remaining solvent Respectively.

2. Tape making and lamination step

The prepared slurry was coated with a doctor blade to prepare green sheet for each solid electrolyte membrane, green sheet for anode function layer and green sheet for anode support layer. Each green sheet was laminated to produce a green sheet laminate for a solid oxide fuel cell (SOFC).

3. Sintering step

A green sheet laminate for a solid oxide fuel cell was simultaneously sintered at 1400 to prepare a sintered body.

4. Cathode slurry production step

A composite (average particle size of 64.4% by weight of the _{3.27㎛ BSCF (Ba 0. 5 Sr} 0. 5 Co 0. 8 Fe 0. The ₂ O _{3 -δ)} with a mean particle size of the 3.87㎛ uniformly mixed Co ₃ O ₄ , A BSCF: Co ₃ O ₄ weight ratio of 95: 5), 22.7 wt% ethyl cellulose binder and 7.7 wt% DBP plasticizer, and a remaining amount of butyl carbitol solvent were placed on a 3-roll mill To prepare an anode printing slurry.

5. Cathode printing step

The prepared cathode functional layer printing slurry was applied to the sintered electrolyte of the sintered body using a screen printer. After drying, the cathode active layer slurry was printed in the same manner.

6. Cathode sintering step

The cathode layer was sintered at 900 to 1,100 to prepare a solid oxide fuel cell (SOFC).

< Experimental Example  1>

The ASR of the LSCF and BSCF cathodes containing 5 wt% of Co oxide was measured for the cathode performance evaluation.

The evaluation cell was fabricated as a symmetric type of electrode / GDC / electrode structure. The GDC support was press molded with ULSA powder and made into a pellet of 1.9 mm thickness and annealed at 1,723 K for 5 hours for dense structure. Each of the cathode slurries was coated on both sides of the support in a size of about 5.9 mm and sintered at 1,100 ° C. Pt mesh and wire were used as the current collector, and Pt paste was applied to the surface of the electrode, followed by heat treatment at 950 ℃.

Each completed cell was evaluated by Electrochemical Impedance Spectroscopy (EIS) via EC-lab software. The ASR value was calculated by subtracting the value of the intersection between the high frequency and low frequency and the real axis in the Nyquist plot.

The measurement proceeded at 650 ° C OCV condition and the cathode of the present invention showed better values with ASR of 1.99 ohm x cm ² , 0.52 ohm x cm ² for LSCF and BSCF cathodes containing Co oxide, respectively.

As described above, the solid oxide fuel cell according to one embodiment of the present application is characterized in that durability can be improved by forming a cathode using a mixture of the compound represented by Formula 1 and the Co oxide. In particular, the Co oxide prevents the decomposition of Sr in formula (1), thereby improving the durability of the solid oxide fuel cell.

In addition, the solid oxide fuel cell according to one embodiment of the present application has an advantage that the interface between the electrolyte and the cathode is stable.

In addition, the solid oxide fuel cell according to one embodiment of the present application has an advantage of having high battery performance with reproducibility.

60: Battery module
70: oxidant supplier
80: fuel supply unit
81: Fuel tank
82: Pump

Claims (7)

A method of manufacturing a solid oxide fuel cell comprising an anode, a cathode, and an electrolyte layer provided between the anode and the cathode,
And forming a cathode on the electrolyte layer by using a slurry containing a mixture of a compound represented by the following formula (1) and a Co oxide:
[Chemical Formula 1]
Ba _{1 - x} Sr _x B _{1 - y} B ' _y O _{3 隆}
In Formula 1,
B and B 'are different from each other and selected from Mn, Fe, Co, Ni, Cu, Ti, Nb,
0 &lt; x? 1, 0? Y? 1, 0? [2] The method of claim 1, wherein the content of the Co oxide is 1 to 10% by weight based on the total weight of the compound represented by the formula (1). The method of claim 1, wherein the content of the Co oxide is 3 to 7 wt% based on the total weight of the compound represented by the formula (1). The method of claim 1, wherein B in the formula (1) is Co and B 'is Fe. The method of claim 1, wherein the Co oxide is CoO or Co ₃ O ₄ . A solid oxide fuel cell comprising an anode, a cathode, and an electrolyte layer disposed between the anode and the cathode,
Wherein the cathode comprises a mixture of a compound represented by the following formula (1) and a Co oxide:
[Chemical Formula 1]
Ba _{1 - x} Sr _x B _{1 - y} B ' _y O _{3 隆}
In Formula 1,
B and B 'are different from each other and selected from Mn, Fe, Co, Ni, Cu, Ti, Nb,
0 &lt; x? 1, 0? Y? 1, 0? The solid oxide fuel cell according to claim 6, wherein B in the formula (1) is Co and B 'is Fe.

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