KR102079846B1 - Method for operating solid oxide fuel cell and solid oxide fuel cell operated thereby - Google Patents

Abstract

The present specification relates to a method of operating a solid oxide fuel cell and a solid oxide fuel cell operated by the same.

Description

METHOD FOR OPERATING SOLID OXIDE FUEL CELL AND SOLID OXIDE FUEL CELL OPERATED THEREBY}

The present specification relates to a method of operating a solid oxide fuel cell and a solid oxide fuel cell operated by the same.

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 the alternative energy sources, the fuel cell has received particular attention due to its advantages such as high efficiency, no pollutants such as NOx and SOx, and abundant fuel.

A fuel cell is a power generation system that converts chemical reaction energy of fuel and oxidant into electrical energy. Hydrogen, hydrocarbons such as methanol, butane, and the like are typically used as fuel, and oxygen is used as the 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 fuels. Batteries (SOFC) and the like.

On the other hand, it is also necessary to study the metal air secondary battery for manufacturing the air electrode of the metal secondary battery as the cathode by applying the principle of the cathode of the fuel cell.

Republic of Korea Patent Publication No. 2016-0059419 (2016.05.26 published)

The present specification is to provide a method for operating a solid oxide fuel cell and a solid oxide fuel cell operated by the same.

The present specification provides a method for operating a solid oxide fuel cell including an anode including an anode including at least one of a composite metal oxide represented by Chemical Formula 1, and an electrolyte including a ceria-based metal oxide between the anode and the cathode. Adjusting a driving temperature of the solid oxide fuel cell while supplying a gas containing oxygen to the fuel electrode and the air electrode, respectively; Supplying a gas containing oxygen to the air electrode, and supplying nitrogen and hydrogen to the fuel electrode to reduce NiO of the fuel electrode to Ni; Supplying a gas containing oxygen to the cathode and supplying hydrogen to the reduced fuel electrode to drive the solid oxide fuel cell; And increasing or shortening oxygen vacancies (δ) of the composite metal oxide by supplying nitrogen to the anode and the cathode, respectively, before or after the reduction of the anode. .

[Formula 1]

A _1-x Sr _x Co _1-y Fe _y O _3-δ

In Formula 1, 0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, 0.01 ≦ δ ≦ 0.1, and A is Ba or La.

In addition, the present specification is driven according to the driving method, and includes a fuel electrode, an air electrode including at least one of a composite metal oxide represented by the following formula (2) and an electrolyte provided between the fuel electrode and the air electrode and containing a ceria-based metal oxide. A solid oxide fuel cell comprising: a solid oxide fuel cell in which an open circuit voltage (OCV) of the solid oxide fuel cell increases as the flow rate of hydrogen supplied to the anode increases when the solid oxide fuel cell is driven. do.

[Formula 2]

A _1-x Sr _x Co _1-y Fe _y O _3-δ

In Formula 2, 0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, 0.2 ≦ δ ≦ 0.5, and A is Ba or La.

The electrolyte of the solid oxide fuel cell according to the present specification has an advantage of smoothly injecting oxygen ions from the cathode.

An electrolyte including a ceria-based metal oxide according to an exemplary embodiment of the present specification may have improved reduction durability against hydrogen.

An electrolyte including a ceria-based metal oxide according to an exemplary embodiment of the present specification may improve OCV characteristics and cell performance.

1 is a schematic diagram showing the electricity generation principle of a solid oxide fuel cell.
2 is a view schematically showing an embodiment of a battery module including a fuel cell.
3 is a graph of OCV change before and after treatment in 600 ℃ nitrogen atmosphere of Example 1.
Figure 4 is a graph of the OCV change before and after treatment in 650 ℃ nitrogen atmosphere of Example 2.
FIG. 5 is a graph showing changes in OCV with increasing flow rate of hydrogen after treatment in a nitrogen atmosphere of 650 ° C. of Example 2. FIG.
6 is a graph of OCV change with increasing flow rate of hydrogen in the comparative example.

Hereinafter, the present specification will be described in detail.

The present specification provides a method of operating a solid oxide fuel cell including an anode including an anode including at least one of a composite metal oxide represented by Formula 1, and an electrolyte provided between the anode and the cathode and including a ceria-based metal oxide. do.

[Formula 1]

A _1-x Sr _x Co _1-y Fe _y O _3-δ

In Formula 1, 0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, 0.01 ≦ δ ≦ 0.1, and A is Ba or La.

The operating method of the solid oxide fuel cell may include adjusting a driving temperature of the solid oxide fuel cell while supplying a gas containing oxygen to the fuel electrode and the air electrode, respectively;

Supplying a gas containing oxygen to the air electrode, and supplying nitrogen and hydrogen to the fuel electrode to reduce NiO of the fuel electrode to Ni;

Supplying a gas containing oxygen to the cathode and supplying hydrogen to the reduced fuel electrode to drive the solid oxide fuel cell; And

Before or after the reduction step of the anode, and supplying nitrogen to the anode and the cathode, respectively, comprising the step of increasing the oxygen vacancy (δ) of the composite metal oxide.

The operating method of the solid oxide fuel cell includes adjusting the driving temperature of the solid oxide fuel cell while supplying a gas containing oxygen to the fuel electrode and the air electrode, respectively.

The driving temperature of the solid oxide fuel cell may be 550 ° C. or more and 700 ° C. or less.

The operating method of the solid oxide fuel cell may include preparing a solid oxide fuel cell in which the fuel electrode, the electrolyte, and the air electrode are sequentially stacked before adjusting to the driving temperature;

Placing and assembling the solid oxide fuel cell between at least two separators;

Applying a sealant on the solid oxide fuel cell;

Removing the additive in the sealant by raising the temperature while supplying a gas containing oxygen to the fuel electrode and the air electrode, respectively; And

The method may further include sealing the solid oxide fuel cell with the sealant by pressurizing the solid oxide fuel cell.

In the manufacturing of the solid oxide fuel cell by sequentially stacking the anode, the electrolyte, and the cathode, the cathode may include at least one of a composite metal oxide represented by the following Chemical Formula 1.

[Formula 1]

A _1-x Sr _x Co _1-y Fe _y O _3-δ

In Formula 1, 0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, 0.01 ≦ δ ≦ 0.1, and A is Ba or La.

The sealant may include a glass powder, and may further include an additive including at least one of a binder, a plasticizer, a dispersant, and a solvent. The binder, plasticizer, dispersant, and solvent are not particularly limited, and conventional materials known in the art may be used.

The sealant may further include a metal oxide.

In the removing of the additive in the sealant, additives such as binders, plasticizers, dispersants, and solvents other than the glass powder may be removed, and when the metal oxide is further included, the additives except the glass powder and the metal oxide may be removed.

Sealing the solid oxide fuel cell may move to a position where an additive is removed and a fluid sealant is pressurized to be sealed and fills an empty space to seal the solid oxide fuel cell.

In the step of removing the additive in the sealant, the final elevated temperature may be 700 ° C. or more and 800 ° C. or less, and specifically 700 ° C. or more and 730 ° C. or less.

When the final elevated temperature of the step of removing the additive in the sealant is 700 ° C or more and 800 ° C or less and the driving temperature of the solid oxide fuel cell is 600 ° C or more and 650 ° C or less, the temperature is raised to add the additive in the sealant. After removal, the cooling may be performed to a driving temperature of the solid oxide fuel cell.

The operating method of the solid oxide fuel cell includes supplying a gas containing oxygen to the cathode, and supplying nitrogen and hydrogen to the anode to reduce NiO of the anode to Ni.

The reducing step of the anode may be performed at a driving temperature of a solid oxide fuel cell.

In the reducing step of the anode, based on the flow rate of nitrogen, the percentage of the flow rate of hydrogen may be 1% or more and 100% or less.

In the reducing step of the anode, the anode may be reduced by supplying nitrogen and hydrogen to the anode until the anode is sufficiently reduced. In the reducing step of the anode, it can be confirmed whether the anode is sufficiently reduced by measuring an open circuit voltage (OCV). Specifically, while reducing the anode, when the open circuit voltage is 940mV or more, or when the open circuit voltage is increased by 2% or more, it can be considered that the anode is sufficiently reduced.

The time for reducing the fuel electrode is not particularly limited as long as the fuel electrode is sufficiently reduced, but if necessary, nitrogen and hydrogen may be supplied to the fuel electrode for 0.5 to 24 hours to reduce the fuel electrode.

The operating method of the solid oxide fuel cell includes increasing oxygen vacancy (δ) of the composite metal oxide by supplying nitrogen to the anode and the cathode, respectively, before or after the reduction step of the anode.

The step of increasing the oxygen vacancy may be performed at a driving temperature of the solid oxide fuel cell.

In the increase of the oxygen vacancies, the time for supplying nitrogen to the fuel electrode and the air electrode, respectively, may be 0.5 hours or more and 2 hours or less.

In the increase of the oxygen vacancies, the temperature for supplying nitrogen to the fuel electrode and the air electrode may be 550 ° C. or more and 800 ° C. or less. If the temperature is lower than 550 ° C, the partial pressure of oxygen may drop sharply and the structure of the cathode may be destroyed. At temperatures higher than 800 ° C., oxygen partial pressures cannot be formed arbitrarily.

In the increase of the oxygen vacancy, the temperature for supplying nitrogen to the fuel electrode and the air electrode may be 550 ° C. or more and 650 ° C. or less.

In the increase of the oxygen vacancy, the oxygen vacancy of the composite metal oxide may be increased, and the change (Δδ) of the oxygen vacancy of the composite metal oxide represented by Equation 1 may be 0.1 or more and 0.49 or less.

[Equation 1]

Δδ = δ _f -δ _i

In Equation 1, δ _f is the oxygen pore value of the composite metal oxide after the increasing step of the oxygen pore, δ _i is the oxygen pore value of the composite metal oxide before the step of increasing the oxygen pore.

Oxygen pores (δ) of the composite metal oxide after the increase of the oxygen pores may be 0.2 or more and 0.5 or less.

In the step of increasing the oxygen vacancies and oxygen partial pressure of the solid oxide fuel cell (Po ₂₎ it is at least 10 ^-12 bar 10 ^- may be up to ⁵ bar. In this case, oxygen pores can be stably increased while maintaining the perovskite structure of the cathode.

The operating method of the solid oxide fuel cell includes supplying a gas containing oxygen to the cathode and supplying hydrogen to the reduced anode to drive the solid oxide fuel cell.

The ceria-based metal oxide of the electrolyte has a high ion conductivity, but has a disadvantage of low chemical stability. Specifically, the ceria-based metal oxides are easily reduced to trivalent Ce tetravalent ions by hydrogen, and the reduced ceria-based metal oxides have increased characteristics of electron conduction so that current flows.

Thus, when the electrolyte includes a reduced ceria-based metal oxide, current may flow between the air electrode and the fuel electrode by the electrolyte. As the current flows between the cathode and the anode, the open circuit voltage (OCV) may decrease, and the energy conversion efficiency of the fuel cell may decrease.

According to the exemplary embodiment according to the present specification, the cathode including the composite metal oxide having increased oxygen pores in the oxygen pores increase step may increase oxygen ion conductivity.

Injection of oxygen ions (O ^2- ) into the electrolyte from the cathode with increased oxygen ion conductivity can be facilitated, and the oxygen ions injected from the cathode oxidize the electrolyte, thereby increasing the area maintained by the oxygen ions. And the area reduced by the hydrogen flowing from the anode supplied with hydrogen is reduced, so that the reduction durability of the electrolyte including the ceria-based metal oxide as a whole can be improved.

In the increasing step of the oxygen vacancy, the composite metal oxide having increased oxygen vacancy may include at least one of the composite metal oxide represented by the following formula (2).

[Formula 2]

A _1-x Sr _x Co _1-y Fe _y O _3-δ

In Chemical Formula 2,

0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, 0.2 ≦ δ ≦ 0.5, and A is Ba or La.

When the solid oxide fuel cell is driven, an open circuit voltage (OCV) of the solid oxide fuel cell may increase as the flow rate of hydrogen supplied to the anode increases.

In the range of hydrogen flow rate in which the flow rate of hydrogen supplied to the anode increases from 5cc / cm ² to 125cc / cm ² and the fuel utilization rate (U _f ) according to Equation 2 below for hydrogen supplied to the anode is 80% or less, The open circuit voltage (OCV) of the solid oxide fuel cell may increase.

[Equation 2]

^{_{U f = e - / H feed}} Ⅹ 100

In Equation 2, e ⁻ is the number of electrons generated by the fuel, and H _feed is the number of hydrogen atoms supplied to the anode.

The fuel utilization rate is a value representing the number of electrons generated as a percentage of the injected fuel (the number of hydrogen atoms). If we inject a small amount of fuel assuming a constant current draw, the efficiency of using fuel increases, and if we inject too little fuel to increase fuel utilization, all the injected fuel cannot be converted into electrons, so we can extract the desired current. There will be no.

A flow rate range of less than 80% fuel utilization means that a certain amount of flow rate (more than 5 cc / cm ² ) can be injected to show a constant voltage, and in the case of ceria-based electrolytes, more hydrogen is injected. In this case, the electrolyte gradually decreases, indicating that the open circuit voltage (OCV) may gradually decrease.

In the solid oxide fuel cell, the cathode has both electrical conductivity and oxygen ion conductivity, but electrical conductivity and oxygen ion conductivity generally have a trade off relationship that is incompatible with each other. However, although it is preferable that the cathode has high electrical conductivity as an electrode, oxygen ion conductivity is also a required characteristic for oxygen ions formed at the cathode to be well transferred to the electrolyte.

The composite metal oxide represented by the formula (1) is affected by the electrical conductivity and the oxygen ion conductivity related to the oxygen _pore ( _δ ) value by the kind of the metals of A, Sr, Co and Fe and the content ratio thereof.

The cathode may be made of a material having a higher electrical conductivity than the oxygen ion conductivity, and the characteristics of the material may be maintained after sealing the solid oxide fuel cell of the present disclosure and before the increase of the oxygen vacancies is performed. By performing the step of increasing the oxygen vacancy, the oxygen treatment of the cathode material may be further removed by nitrogen treatment to increase oxygen deficiency, thereby increasing the oxygen void _δ of the cathode material. At this time, in the increase of the oxygen vacancy, the metal of the A, Sr, Co and Fe of the cathode material is almost unchanged, the electrical conductivity is maintained and the oxygen ion conductivity can be increased by increasing the oxygen deficiency of the cathode material.

In the case where the inorganic particles having the increased oxygen vacancy ( _δ ) value are selected from the step for preparing the cathode of the solid oxide fuel cell by performing the step of increasing the oxygen vacancy of the present specification, the oxygen vacancy ( _δ ) value is obtained. The ratio of the metals of A, Sr, Co and Fe may change to reach the required electrical conductivity, and the oxygen vacancy ( _δ ) value is reduced due to exposure to high temperatures in the process of sintering and sealing of the cathode, and thus oxygen ions. Conductivity may be reduced.

Herein is driven according to the driving method, a solid comprising a fuel electrode, an air electrode including at least one of a composite metal oxide represented by the following formula (2) and an electrolyte provided between the fuel electrode and the air electrode and containing a ceria-based metal oxide As the oxide fuel cell, when the solid oxide fuel cell is driven, an open circuit voltage (OCV) of the solid oxide fuel cell increases as the flow rate of hydrogen supplied to the anode increases.

[Formula 2]

A _1-x Sr _x Co _1-y Fe _y O _3-δ

In Formula 2, 0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, 0.2 ≦ δ ≦ 0.5, and A is Ba or La.

FIG. 1 schematically illustrates the principle of electricity generation of a solid oxide fuel cell. The solid oxide fuel cell includes an electrolyte layer, an anode, and a cathode formed on both surfaces of the electrolyte layer. do. Referring to FIG. 1, which illustrates a principle of electricity generation of a solid oxide fuel cell, oxygen ions are generated as the air is electrochemically reduced in the cathode, and the generated oxygen ions are transferred to the anode through the electrolyte layer. In the anode, fuel such as hydrogen, methanol, butane, and the like are injected, and the fuel is combined with oxygen ions to oxidize electrochemically, thereby producing electrons and generating water. This reaction causes the movement of electrons in the external circuit.

The cathode may include at least one of the composite metal oxides represented by the following Chemical Formula 2.

[Formula 2]

A _1-x Sr _x Co _1-y Fe _y O _3-δ

In Formula 2, 0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, 0.2 ≦ δ ≦ 0.5, and A is Ba or La.

The cathode may include at least one of a composite metal oxide represented by Formula 3 and a composite metal oxide represented by Formula 4.

[Formula 3]

Ba _1-x Sr _x Co _1-y Fe _y O _3-δ

In Formula 3, 0.2≤x≤0.5, 0.6≤y <1, 0.2≤δ≤0.5,

[Formula 4]

La _1-x Sr _x Co _1-y Fe _y O _3-δ

In Formula 4, 0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, and 0.2 ≦ δ ≦ 0.5.

In Chemical Formulas 2 to 4, y may be each independently 0.8 or less than 1.

The cathode may further include an inorganic material of the electrolyte, and may further include a ceria-based metal oxide, and more specifically, may further include at least one of samarium dope ceria and gadolinium dope ceria.

When the electrolyte layer includes gadolinium dope ceria, the air electrode may further include gadolinium dope ceria which is an inorganic material of the electrolyte layer.

The cathode may further include a lanthanum strontium cobalt oxide (LSC).

The cathode may have a thickness of 10 μm or more and 100 μm or less. Specifically, the cathode may have a thickness of 20 μm or more and 50 μm or less.

The porosity of the air electrode may be 10% or more and 50% or less. Specifically, the porosity of the air electrode may be 10% or more and 30% or less.

The pore diameter of the air electrode may be 0.1 μm or more and 10 μm or less. Specifically, the diameter of the pores of the air electrode may be 0.5 ㎛ or more and 5 ㎛ or less. More specifically, the diameter of the pores of the air electrode may be 0.5 ㎛ or more and 2 ㎛ or less.

The manufacturing method of the cathode is not particularly limited, for example, by coating a slurry for the cathode and drying and baking it, or by coating and drying the cathode slurry on a separate release paper to prepare a cathode green sheet, at least one cathode The green sheet may be fired alone or with the green sheets of neighboring heterogeneous layers to prepare an air electrode.

The cathode green sheet may have a thickness of 10 μm or more and 100 μm or less.

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

Based on the total weight of the slurry for the cathode, the content of the composite metal oxide particles represented by the formula (2) is 40% to 70% by weight, the solvent content is 10% to 30% by weight of the dispersant The content may be 5 wt% or more and 10 wt% or less, the content of the plasticizer may be 0.5 wt% or more and 3 wt% or less, and the binder may be 10 wt% or more and 30 wt% or less.

The anode may include an inorganic material having oxygen ion conductivity, so that the anode may be applied to the anode for a solid oxide fuel cell. The type of the inorganic material is not particularly limited, but 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 to 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 fuel electrode may include the same inorganic material as the metal oxide of the electrolyte. Specifically, when the electrolyte includes a ceria-based metal oxide, the fuel electrode may include a ceria-based metal oxide. More specifically, when the electrolyte includes gadolinium dope ceria, the anode may include gadolinium dope ceria.

The fuel electrode may have a thickness of 300 μm or more and 800 μm or less. Specifically, the thickness of the anode may be 500 μm or more and 700 μm or less.

The porosity of the anode may be 10% or more and 50% or less. Specifically, the porosity of the anode may be 10% or more and 30% or less.

The pore diameter of the anode may be 0.1 μm or more and 10 μm or less. Specifically, the diameter of the pores of the anode may be 0.5 ㎛ or more and 5 ㎛ or less. More specifically, the diameter of the pores of the anode may be 0.5 ㎛ or more and 2 ㎛ or less.

The manufacturing method of the anode is not particularly limited, for example, by coating the slurry for the anode and drying and baking it, or coating the anode slurry on a separate release paper and dried to produce a green sheet for the anode, at least one anode The green sheet may be fired alone or with the green sheets of adjacent heterogeneous layers to manufacture a fuel electrode.

The anode green sheet may have a thickness of 500 μm or more and 1000 μm or less.

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

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

The anode slurry may further include NiO. Based on the total weight of the slurry for the anode, the content of NiO may be 30 wt% or more and 60 wt% or less.

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. In this case, the anode support is a layer including the same inorganic material as the anode functional layer but having a higher porosity and a relatively thicker thickness than the anode functional layer to support another layer, and the anode functional layer is provided between the anode support and the electrolyte layer to be actually used. It may be a floor which plays a main role as an anode.

When the anode is provided on the porous ceramic support or the porous metal support, the manufactured anode green sheet may be laminated on the fired porous ceramic support or the porous metal support, and then fired to manufacture the anode.

When the anode includes an anode support and an anode functional layer, the manufactured anode sheet may be laminated on the baked anode support and then fired to manufacture the anode.

When the anode includes the anode support and the anode functional layer, the thickness of the anode support may be 300 μm or more and 800 μm or less, and the thickness of the anode function layer may be 5 μm or more and 50 μm or less.

The electrolyte may include a ceria-based metal oxide.

The ceria-based metal oxide is not particularly limited as long as it is a ceria-based metal oxide having oxygen ion conductivity. Specifically, the ceria-based metal oxide may include at least one of samarium dope ceria and gadolinium dope ceria, and more specifically, may include gadolinium dope ceria. .

The thickness of the electrolyte may be 10 μm or more and 100 μm or less. Specifically, the electrolyte may have a thickness of 20 μm or more and 50 μm or less.

The manufacturing method of the electrolyte is not particularly limited, for example, by coating an electrolyte slurry and drying and baking it, or by coating and drying the electrolyte slurry on a separate release paper to prepare an electrolyte green sheet, and at least one electrolyte The green sheet may be fired alone or with the green sheets of adjacent heterogeneous layers to prepare an electrolyte.

The electrolyte green sheet may have a thickness of 10 μm or more and 100 μm or less.

The slurry for the electrolyte may include ceria-based metal oxide particles, and if necessary, the slurry for the anode 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.

Based on the total weight of the slurry for the electrolyte layer, the content of the ceria-based metal oxide particles may be 40 wt% or more and 70 wt% or less.

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

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-dried state that can maintain a sheet form while containing some solvent.

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

Specifically, the fuel cell may be used as a power source of 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 illustrates an embodiment of a battery module including a fuel cell, wherein the fuel cell includes a battery module 60, an oxidant supply unit 70, and a fuel supply unit 80.

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

The oxidant supply unit 70 serves to supply the oxidant to the battery module 60. Oxygen is typically used as the oxidant, and may be used by injecting oxygen or air into the oxidant supply unit 70.

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

Hereinafter, the present specification will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the present specification, but not to limit the present specification.

EXAMPLE

Example 1

Stack 8 sheets of anode support (GDC / NiO) green sheet with thickness of 120㎛, and one anode functional layer (GDC / NiO) green sheet with thickness of 80㎛ on it, electrolyte (GDC) green sheet with thickness of 20㎛ The laminated body which laminated two sheets sequentially was manufactured. After cutting the laminate, sintering was performed at a final temperature of 1500 ° C. for 3 hours on a porous ceramic setter. Air electrode slurry (LSCF6428 above electrolyte surface (La Sr _{0 0 6 4 0 2} Fe Co _{0 8} O ₃ weight ratio of _-δ, δ <0.1), GDC, and LSC mixture, LSCF, GDC, and LSC is _3:... 2 : 5) The SOFC cell was fabricated by screen printing and baking at a final temperature of 1000 ° C. to 1100 ° C.

After confirming that the OCV was maintained at 0.925V by reducing the anode of the SOFC cell with hydrogen, both the cathode and the anode formed a nitrogen atmosphere at 600 ° C. and maintained for 1 hour. After 1 hour of exposure to nitrogen, air and hydrogen were again supplied to the cathode and the anode to confirm the improved OCV characteristics as 0.94V as shown in FIG. 3.

At this time, in the nitrogen atmosphere, the flow rate of nitrogen was 500 cc / cm ² , and the supply of air and fuel was stopped.

Example 2

In Example 1, after confirming that the OCV of the SOFC cell subjected to nitrogen treatment at 600 ° C. was maintained at 0.94 V, both the cathode and the anode formed a nitrogen atmosphere at 650 ° C. and maintained for 1 hour. After 1 hour of exposure to nitrogen, air and hydrogen were again supplied to the cathode and the anode to confirm the improved OCV characteristics as 0.956V as shown in FIG. 4.

At this time, except that the temperature was changed to 650 ℃ nitrogen forming conditions are the same as in the embodiment.

In addition, when increasing the hydrogen flow rate from 10cc / cm ² to 500cc / cm ² it can be seen that the OCV increases as shown in FIG.

Comparative Example 1

After confirming that the OCV is maintained at 0.925V by reducing the anode of the SOFC cell manufactured in the same manner as in Example 1, the OCV is measured by directly supplying air and hydrogen to the cathode and the anode, respectively, without forming a nitrogen atmosphere. did.

At this time, when increasing the hydrogen flow rate from 10cc / cm ² to 500cc / cm ² it was confirmed that the OCV value decreases as shown in FIG.

Experimental Example 1

Oxygen partial pressure in nitrogen atmosphere (100cc), hydrogen atmosphere (100cc), mixed atmosphere of nitrogen and hydrogen (100cc each) was measured using an oxygen sensor at 550 ° C, 600 ° C, 650 ° C and 800 ° C. The oxygen partial pressure for each temperature was calculated based on Equation 3. The results are shown in Table 1 below, with each value representing log (Po ₂ / bar).

[Equation 3]

E ⁰ : Standard electrode potential

R: gas constant

T ： Absolute temperature (K)

Z: Valence of solution ions

A ： reduction and activity of oxidant

F ： Faraday's constant (= 96,485 C / mol)

In Table 1, the oxygen partial pressure for each temperature according to the gas atmosphere was calculated and expressed through Equation 3. Through Table 1, it is possible to predict the conditions that can effectively form the oxygen vacancies (vacancy) of the cathode.

When the oxygen partial pressure (log (Po ₂ / bar)) is -12 or less, the perovskite structure of the cathode is rapidly collapsed, and when the oxygen partial pressure is -5 or more, oxygen vacancies are hardly formed. Through this, it can be seen that the oxygen vacancies can be increased while maintaining the perovskite structure of the cathode in the oxygen pores in which nitrogen is supplied.

60: battery module
70: oxidant supply
80: fuel supply
81: fuel tank
82: pump

Claims (10)

A method of operating a solid oxide fuel cell including a fuel electrode, an air electrode including at least one of a composite metal oxide represented by Formula 1, and an electrolyte provided between the fuel electrode and the air electrode and containing a ceria-based metal oxide,
Adjusting a driving temperature of the solid oxide fuel cell while supplying a gas containing oxygen to the fuel electrode and the air electrode, respectively;
Supplying a gas containing oxygen to the air electrode, and supplying nitrogen and hydrogen to the fuel electrode to reduce NiO of the fuel electrode to Ni;
Supplying a gas containing oxygen to the cathode and supplying hydrogen to the reduced fuel electrode to drive the solid oxide fuel cell; And
Before or after the reduction step of the anode, the method of operating a solid oxide fuel cell comprising supplying nitrogen to the anode and the cathode, respectively, to increase the oxygen vacancy (δ) of the composite metal oxide.
[Formula 1]
A _1-x Sr _x Co _1-y Fe _y O _3-δ
In Chemical Formula 1,
0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, 0.01 ≦ δ ≦ 0.1, and A is Ba or La. The method of claim 1, wherein the ceria-based metal oxide comprises at least one of samarium dope ceria and gadolinium dope ceria. The method of claim 1, wherein the driving temperature of the solid oxide fuel cell is 550 ° C or more and 700 ° C or less. The method of operating a solid oxide fuel cell of claim 1, wherein, in the reducing step of the anode, the percentage of the flow rate of the hydrogen is 1% or more and 100% or less based on the flow rate of the nitrogen. The method of operating a solid oxide fuel cell as set forth in claim 1, wherein a change (Δδ) of oxygen vacancies of the composite metal oxide represented by Formula 1 is 0.1 or more and 0.49 or less.
[Equation 1]
Δδ = δ _f -δ _i
In Equation 1, δ _f is the oxygen pore value of the composite metal oxide after the increasing step of the oxygen pore, δ _i is the oxygen pore value of the composite metal oxide before the step of increasing the oxygen pore. The method of operating a solid oxide fuel cell of claim 1, wherein an oxygen pore δ of the composite metal oxide after the increase of the oxygen pore is 0.2 or more and 0.5 or less. The method of operating a solid oxide fuel cell as set forth in claim 1, wherein, in the step of increasing the oxygen vacancy, a time for supplying nitrogen to the fuel electrode and the air electrode, respectively, is 0.5 hours or more and 2 hours or less. The method of operating a solid oxide fuel cell as set forth in claim 1, wherein, in the step of increasing the oxygen vacancy, a temperature for supplying nitrogen to the fuel electrode and the air electrode, respectively, is 550 ° C or more and 650 ° C or less. Driven according to any one of claims 1 to 8,
A solid oxide fuel cell comprising a fuel electrode, an air electrode including at least one of a composite metal oxide represented by Formula 2, and an electrolyte provided between the fuel electrode and the air electrode and containing a ceria-based metal oxide,
A solid oxide fuel cell in which an open circuit voltage (OCV) of the solid oxide fuel cell increases as the flow rate of hydrogen supplied to the anode increases when the solid oxide fuel cell is driven:
[Formula 2]
A _1-x Sr _x Co _1-y Fe _y O _3-δ
In Chemical Formula 2,
0.2 ≦ x ≦ 0.5, 0.6 ≦ y <1, 0.2 ≦ δ ≦ 0.5, and A is Ba or La. The hydrogen flow rate according to claim 8, wherein the flow rate of hydrogen supplied to the anode increases from 5cc / cm ² to 125cc / cm ² and the fuel utilization rate (Uf) according to Equation 2 for hydrogen supplied to the anode is 80% or less. In the range, the solid oxide fuel cell of which the open circuit voltage (OCV) of the solid oxide fuel cell is increased:
[Equation 2]
U _f = e ^- / H _feed
In Equation 2, e ⁻ is the number of electrons generated by the fuel, and H _feed is the number of hydrogen atoms supplied to the anode.

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