KR102674321B1 - Metal support type solid oxide fuel cell including contacting layer - Google Patents

Abstract

A metal support type solid oxide fuel cell including a contact layer is provided. A metal support type solid oxide fuel cell including a contact layer includes a metal support, a contact layer sequentially stacked on top of the metal support, a fuel electrode layer, an electrolyte layer, and an air electrode layer, and the contact layer is inserted into the fuel cell. By alleviating the difference in microstructure between layers and providing a gradient in microstructure, a solid oxide fuel cell with increased lifespan and improved thermal cycle characteristics is provided.

Description

Metal support type solid oxide fuel cell including contacting layer}

The present invention relates to a solid oxide fuel cell (SOFC), and more specifically to a metal support type solid oxide fuel cell including a contact layer.

The metal support type solid oxide fuel cell is a new concept solid oxide fuel cell that can increase mechanical strength and sealing efficiency by reducing the thickness of the ceramic element by using metal as a support instead of the anode of the current anode support type fuel cell. . The metal support type solid oxide fuel cell can at least solve the sealing problem between the fuel electrode and the separator by having the metal support act as a separator for the ceramic support type fuel cell. In addition, since metal processing processes are more accessible than ceramic processing processes, fuel cell performance can be improved through flow path processing, etc., and manufacturing costs are also expected to be significantly reduced.

In addition, since the metal support type solid oxide fuel cell is resistant to thermal and mechanical shock and is capable of rapid thermal cycling, the thermal and mechanical reliability, which is a weakness of existing solid oxide fuel cell stacks and systems, is greatly improved, leading to the commercialization of solid oxide fuel cells. can make it possible.

The manufacturing method of the metal support type solid oxide fuel cell involves lamination of green sheets manufactured by tape casting the metal support, the powder forming the anode layer, and the solid electrolyte layer, respectively, and then co-firing in a reducing atmosphere (co- There is a method of firing.

However, the above method precisely controls the thermal expansion coefficient and sintering shrinkage rate of each of the solid electrolyte layer, anode layer, and metal support, and adjusts the composition, particle size, surface roughness, and firing atmosphere of the metal so that the metal support has sufficient porosity even after high-temperature co-firing. There is a problem that must be precisely controlled. In addition, in the case of fuel cells manufactured using this manufacturing method, sintering shrinkage of the substrate does not occur during sintering, so in the wet powder process, the thin metal plate interferes with the shrinkage of the solid electrolyte layer, resulting in remaining pores and cracks due to local sintering. When a crack occurs, there is a problem in that a crossover phenomenon occurs when the anode gas and air meet through the solid electrolyte layer.

Korean Patent Publication No. 10-2013-0031466

The problem to be solved by the present invention is to insert a contact layer between the metal support and the anode layer to prevent the difference in gas flow and large strain between the layers due to the difference in microstructure between the metal support and the anode layer. To provide a metal support type solid oxide fuel cell with reduced stress.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

In order to achieve the above technical problem, one aspect of the present invention provides a metal support type solid oxide fuel cell including a contact layer. A metal support type solid oxide fuel cell includes a metal support, a contact layer laminated on top of the metal support, which passes gas and electricity while acting as a buffer in terms of microstructure, and a contact layer laminated on top of the contact layer, and ionized oxygen ions are injected. An anode layer that combines hydrogen to produce water and electrons, laminated on top of the anode layer, a solid electrolyte layer that prevents hydrogen and air from mixing and allows oxygen ions to pass through, and laminated on the top of the solid electrolyte layer, It may include an air electrode layer that produces oxygen ions by reducing the injected air.

A protective layer may be included between the electrolyte layer and the air cathode layer.

The protective layer may include Ce _1-y Ln _y O _2-β (Ln=Gd, Sm, Nd or La, y=0.1∼0.3, β=0∼0.2).

It may include a current collector stacked on top of the air cathode layer.

The metal support may be any one of Ni metal, Ni-Fe alloy, and STS (Stainless Steel).

The anode layer may be either a NiO and rare earth-doped zirconia composite or a NiO and rare earth-doped ceria composite.

The anode layer is a perovskite-based oxide and CeO ₂ , wherein the perovskite-based oxide is A' _x B' _y O ₃ (where 0≤x≤1, 0≤y≤1, A'=La, Sr, one or more of Ba, Pr, Sm; B'=one or more of Ti, Y, Sc, Cr, V, Mn, Co, Fe, Ni, Mo, Nb, Al, Mg, Ca).

The composition of the cathode layer includes a perovskite-based oxide, and the perovskite-based oxide is A' _x B' _y O ₃ (where 0≤x≤1, 0≤y≤1, and A'=La , Sr, Ba, Pr, Sm; B'=one or more of Ti, Y, Sc, Cr, V, Mn, Co, Fe, Ni, Mo, Nb, Al, Mg, Ca).

The composition of the air cathode layer may further include at least one of a sintered powder mixture of rare earth-doped ceria or a pore former.

The electrolyte layer may be any one of rare earth-doped zirconia-based oxide, rare earth-doped ceria-based oxide, and perovskite-based oxide.

The perovskite-based oxide may be La _1-x A _x Ga _1-y B _y O ₃ (A=Sr, Ba; B=Mg, Ca).

The contact layer may be a mixture of components of the metal support and components of the anode layer.

The metal support component of the contact layer and the anode layer component may have a composition ratio of 7:3 to 3:7.

The average particle size of the contact layer may be 0.3 ㎛ to 30 ㎛.

The thickness of the contact layer may be 5 ㎛ to 50 ㎛.

The thermal expansion coefficient of the contact layer may be 10 (ppm/℃) to 20 (ppm/℃).

As described above, according to the present invention, a contact layer exists between the metal support layer and the anode layer, thereby mitigating the difference in microstructure caused by the difference in density and particle size between the metal support layer and the anode layer. The stability of the fuel cell can be improved by alleviating deformation and facilitating the flow of gas. Additionally, the contact layer can suppress interlayer delamination by acting as a buffer to alleviate the difference in thermal expansion coefficient between the metal support layer and the anode layer.

Figure 1 is a schematic diagram showing the structure of a metal support type solid oxide fuel cell including a contact layer according to an embodiment of the present invention.
Figure 2 is a cross-sectional view comparing the microstructure of a Ni-based metal support type solid oxide fuel cell before and after reduction.
Figure 3 is a cross-sectional view comparing the microstructure of the STS-based metal support type solid oxide fuel cell.
Figure 4 shows the radius of curvature formed when a contact layer or an anode layer is laminated on the top of a metal support, respectively.

Hereinafter, in order to explain the present invention in more detail, preferred embodiments according to the present invention will be described in more detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.

The terminology used in this specification is only for referring to examples and is not intended to limit the invention. As used herein, singular forms include plural forms unless phrases clearly indicate the contrary. As used in the specification, the meaning of “comprising” specifies a specific characteristic, area, integer, step, operation, element and/or component, and the presence of another specific property, area, step, operation, element, component and/or group. This does not exclude addition.

In addition, all terms including technical and scientific terms used in this specification have the same meaning as those generally understood by those skilled in the art in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted as having meanings consistent with related technical literature and currently disclosed content, and are not interpreted in ideal or very formal meanings unless defined.

In the drawings herein, the thicknesses of layers and regions are exaggerated for clarity. Like reference numerals refer to like elements throughout the specification.

Solid oxide fuel cell including a contact layer

Figure 1 is a schematic diagram showing the structure of a metal support type solid oxide fuel cell including a contact layer according to an embodiment of the present invention. Referring to FIG. 1, the metal support type solid oxide fuel cell 10 including the contact layer includes a contact layer 12 laminated on top of a metal support 11 and an anode layer 13 laminated on the top, The solid electrolyte layer 14 may be stacked on top of the anode layer, and the air electrode layer 16 may be stacked on top of the solid electrolyte layer. Additionally, a protective layer 15 may be stacked between the solid electrolyte layer 14 and the air cathode layer 16, and a current collector 17 may be stacked on top of the air cathode layer 16.

The metal support 11 has a small decrease in electrical conductivity due to high-temperature oxidation, has redox stability, and has a thermal expansion coefficient of 5 to 20 (ppm/℃), specifically 10 to 15 (ppm/℃). Phosphorus material is preferred. The reason for limiting the thermal expansion coefficient of the metal support like this is to reduce the difference in thermal expansion coefficient between the metal support and each ceramic functional layer laminated on it to prevent peeling of the functional layer or bending of the cell due to differences in thermal expansion coefficient between each component. am.

Materials for metal supports having such characteristics include any one of Ni, Ni-Fe alloy, and STS (Stainless Steel), and the STS may be particularly ferritic stainless steel. Product name There are STS434L and Crofer22H, product name of German company Tyssenkrupp.

According to one embodiment of the present invention, the contact layer 12 may be laminated on the metal support 11, and the anode layer 13 may be laminated on the contact layer 12.

In the anode layer 13, hydrogen, which is a fuel injected from the outside, and ionized oxide ions moving from the solid electrolyte layer 14 combine to generate water and electrons. The ceramic precursor powder, which is a component of the anode layer 13, is a composite of NiO and rare earth-doped zirconia (Zr _1-x D _x O ₂ (D= Y, Sc, La, Ce, Pr, Nd, Pm, Sm , Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; x= _0.1∼0.3 )) or NiO and rare earth-doped ceria (Ce _{1-x D} , Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; Additionally, the composite may further include any one or more of perovskite-based oxide and CeO ₂ . At this time, the perovskite-based _{oxide is} A _' B'=Ti, Y, Sc, Cr, V, Mn, Co, Fe, Ni, Mo, Nb, Al, Mg, Ca), and specifically, La _1-x A _x Ga _1-y It may include B _y O ₃ (A=Sr, Ba; B=Mg, Ca).

According to one embodiment of the present invention, the composition ratio of nickel (Ni) and rare earth-doped zirconia in the anode layer 13 may be 6:4 to 4:6, specifically 5.5:4.5 to 4.5:5.5. It can be, and more specifically, it can be 5:5.

On the other hand, the perovskite is a structured compound in the form of ABO ₃ , where the A site is occupied by one or more of the elements lanthanum (La), Sr, Ba, Sm, and Pr, and the B site is occupied by manganese ( It may be composed of some or all of the following elements: Mn), Ti, Cr, V, Ni, Co, Fe, Al, Nb, Mo Mg, and Ca.

According to one embodiment of the present invention, the average thickness of the anode layer 13 is suitably in the range of 5 to 50 ㎛, more preferably 10 to 30 ㎛, and even more preferably 15 to 25 ㎛.

The contact layer 12 passes gas and electricity and functions as a buffer in terms of microstructure. Specifically, the metal support 11 and the anode layer 13 have a large difference in density and particle size, which may cause a difference in gas flow and a large strain between layers. Therefore, by placing the contact layer 12 between the metal support 11 and the anode layer 13, it can serve as a buffer to alleviate microstructural differences. Additionally, the contact layer 12 may serve to suppress interlayer peeling due to a difference in thermal expansion coefficient between the metal support 11 and the anode layer 13.

At this time, the composition of the contact layer 12 may be a mixture of the components of the metal support 11 and the components of the anode layer 13. Specifically, the component of the contact layer 12 may be a mixture of NiO ₂ or Crofer22H, which is a component of the metal support 11, and rare earth-doped zirconia, which is a component of the anode layer 13. At this time, the composition ratio of the components of the metal support 11 and the components of the anode layer 13 in the contact layer 12 may be 9:1 to 3:7, and specifically 8:2 to 4:6. It can be, and more specifically, it can be 7:3 to 6:4.

The average thickness of the contact layer 12 is preferably in the range of 5 to 50 ㎛, more preferably 20 to 40 ㎛, and even more preferably 20 to 30 ㎛. If the thickness of the contact layer 12 is too thin, there is a possibility that some parts of the anode layer 13 and the metal support 11 are in direct contact due to the influence of the surface roughness of the metal support 11, resulting in a partial diffusion reaction. If this is high and too thick, electrical resistance may increase.

According to one embodiment of the present invention, a solid electrolyte layer 14 may be stacked on top of the anode layer 13. The solid electrolyte layer 14 prevents hydrogen and air from mixing and allows only oxygen ions to pass through. Additionally, the component of the solid electrolyte layer 14 may be rare earth-doped zirconia, rare earth-doped ceria, or perovskite-based oxide.

The average thickness of the solid electrolyte layer 14 is in the range of 5 to 30 ㎛, more preferably 10 to 20 ㎛. The performance of the solid oxide fuel cell cell increases as the thickness of the solid electrolyte layer 14 decreases, which compensates for the low ionic conductivity by reducing the internal resistance. However, if it is too thin, the solid electrolyte layer (14) is damaged due to the roughness of the substrate. If a crossover phenomenon occurs where fuel gas and air directly meet through a local defect in 14), not only does the electromotive force decrease, but a hot spot occurs centered on that area, deteriorating the performance of the cell. can be reduced to Accordingly, the solid electrolyte layer 14 may be required to have an appropriate thickness at a level where a crossover phenomenon does not occur.

Meanwhile, an air cathode layer 16 may be laminated on the solid electrolyte layer 14. The air cathode layer 16 can produce oxygen ions by reducing air supplied from the outside. Additionally, the components of the air cathode layer 16 may include a conductor containing perovskite-based oxide alone or a pore-forming agent such as a sintered powder mixture of rare earth-doped ceria and graphite powder. The perovskite-based oxide and rare earth-doped ceria may be the same as defined above.

Specifically, the perovskite-based oxide contained in the cathode layer 16 is La _1-x Sr _x Co _y Fe _1-y O _3-δ (where x = 0.2 to 0.5, y = 0.2 to 1, and δ =0∼0.3). In particular, the conductor mixed with perovskite oxide is one or more La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ , GdCoO _3-δ and Re _x Sr _1-x CoO _3-δ (Re=La, Sm , Pr, 0.5<x<0.8 and δ=0∼0.3). Using these compounds can be useful because they have higher ionic conductivity than most perovskite-based oxides. In some cases the mixture may comprise in the range of 20 to 50 wt. %, in other cases in the range of 30 to 45 wt. %, in other cases in the range of 35 to 45 wt. %, or approximately 40 wt. % rare earth-doped ceria as previously defined. there is. This helps to improve the compatibility between the solid electrolyte layer 14 and the cathode layer 16 both in terms of chemistry and the aforementioned thermal expansion, and since these ceria have a high charge transport rate, their inclusion is beneficial to the solid electrolyte layer. It is possible to ensure a good charge transport rate between (14) and the air cathode layer (16).

More specifically, the air cathode layer 16 may include a perovskite-based oxide such as LSM (La _0.8 Sr _0.2 MnO ₃ ) and ScSZ (Sc-doped ZrO ₂ ). Meanwhile, the LSM is used as a material for an air electrode or a solid electrolyte layer 14 made of rare earth-doped ceria or perovskite-based oxide La _1-x A _x Ga _1-y B _y O ₃ (A=Sr, Ba; When B=Mg, Ca;

Meanwhile, high-performance anode materials such as LSCF ((La _0.6 Sr _0.4 )(Co _0.2 Fe _0.8 )O ₃ ) and BSCF (Br _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ ) are used as the air cathode layer 16 instead of LSM. Alternatively, when rare earth-doped zirconia is used as the solid electrolyte layer 14, an additional protective layer 15 may be required to be inserted between the solid electrolyte layer 14 and the cathode layer 16. Additionally, the average thickness of the air cathode layer 16 may preferably be in the range of 10 to 50 ㎛.

The protective layer 15 is located between the solid electrolyte layer 14 and the cathode layer 16 to prevent diffusion of the composition between the layers, thereby suppressing the generation of impurities, and Ce _1-y Ln _y O _2-β (Ln=Gd, Sm, Nd or La, y=0.1∼0.3, β=0∼0.2). Here, the protective layer 15 is a solid electrolyte layer 14 made of Ce _1-x Ln _x O _2-δ (Ln=La, Gd, Sm, Nd or Y, x=0.1∼0.3, δ=0∼0.2). Compared to , y may be greater than x, and β may be greater than δ.

Additionally, according to one embodiment of the present invention, a current collector 17 may be additionally laminated on top of the air cathode layer 16. The current collector 17 can collect current from the cells in the stack. At this time, the current collector 17 may be any electrically conductive ceramic material, and may generally be a perovskite such as lanthanum strontium copper oxide (LSC).

Below, a preferred experimental example is presented to aid understanding of the present invention. However, the following experimental examples are only intended to aid understanding of the present invention, and the present invention is not limited by the following experimental examples.

<Manufacturing examples>

Manufacturing Example 1: Ni-based metal support type solid oxide fuel cell

Ni _1-x Fe _x Preparation of a metal support consisting of (x = 0 ~ 1)

A ball mill process was performed by mixing NiO (Kceracell, 99.9%, (d50) ∼ 0.7 ㎛) and Fe ₂ O ₃ (LTS Research laboratories, 99.9%) in a 5:5 volume ratio. Afterwards, the powder obtained by drying was manufactured into pellets of 1 g each (approximately 1 mm thick) using a mold with a diameter of 20 mm (pressing pressure: 50 MPa). The produced pellets were pre-sintered at 900°C for 2 hours.

Preparation of contacting layer

To manufacture the contact layer, slurry production was first performed. The slurry contains NiO (Kceracell, 99.9%) as a metal support component and 8YSZ ((Y ₂ O ₃ ) _0.08 (ZrO ₂ ) _0.92 , Kceracell, 99.9%, (d50) ∼ 0.2 ㎛) or ScSZ-6 ( Corn starch was added to the raw material powder mixed with 6 mol% Sc ₂ O ₃ ) at a volume ratio of 7:3 and then manufactured through ball milling. The prepared slurry was drop coated on the pre-sintered pellets and then dried in an oven (30° C.).

Manufacturing of anode layer composed of Ni-ScSZ (Ce, Gd)

To manufacture the anode layer, slurry production was first performed. The slurry is a mixture of raw material powder NiO (Kceracell, 99.9%), 10Sc _0.5 Ce _0.5 GdSZ[(Sc ₂ O ₃ ) _0.1 (CeO ₂ ) _0.005 (Gd ₂ O ₃ ) _0.005 (ZrO ₂ ) _0.89 mixed at a volume ratio of 5.5:4.5. , Kceracell, 99.9%, (d50) ∼ 0.2 ㎛] and corn starch were mixed and prepared through ball milling (150 rpm, 24 hours). 230 ㎕ of the prepared slurry was drop coated on the pellet formed up to the contact layer and dried in an oven (30° C.).

Manufacturing of a solid electrolyte layer composed of ScSZ (Ce, Gd)

To manufacture the solid electrolyte layer, slurry production was first performed. The slurry is a mixture of 10Sc _0.5 Ce _0.5 GdSZ ((Sc ₂ O ₃ ) _0.1 (CeO ₂ ) _0.005 (Gd ₂ O ₃ ) _0.005 (ZrO ₂ ) _0.89, Kceracell, 99.9%, (d50) ∼ 0.2 ㎛) and ethanol. It was manufactured through ball milling (150 rpm, 24 hours). 120 ㎕ of the slurry prepared above was drop coated on the pellet coated up to the anode layer and dried in an oven (30° C.). After drying, co-sintering was performed at 1350°C.

Manufacturing of a cathode containing LSM and ScSZ (Ce, Gd) and a cell containing the same

In the case of the air cathode layer, it was formed through a screen printing technique on a dense solid electrolyte layer. Air cathode powders, LSM (La _0.8 Sr _0.2 MnO ₃ ), Kceracell, 99.9%, (d50) ∼ 0.5 ㎛), and ScSZ were mixed. For screen printing, a 30 ㎛ thick mesh substrate and the air electrode mixture powder were used to form a circle with a diameter of 7.5 mm in the center of the solid electrolyte layer. Afterwards, heat treatment was performed in air at 1200°C for 2 hours to produce a cell.

Manufacturing Example 2: STS-based metal support type solid oxide fuel cell

Manufacturing of STS-based metal support

STS434L (Fe/16.5Cr/1Mo/0.2Ni/0.1Mn/0.0055S/0.017C/0.025P/0.8Si, Hoganas) powder, ethanol (SAMCHUN, purity 99.9%) and binder (PVB-76, SAMCHUN, purity 99.9%) was mixed and ball milled to prepare a slurry. The prepared slurry was used to produce a thick film-type tape molded body using a tape casting (STC-14C) process.

Preparation of contacting layer

Crofer22(Fe/22Cr/0.8Ti/0.5Mn/0.002S/0.005C/0.016P/0.006La, thyssenkrupp), 8YSZ((Y ₂ O ₃ ) _0.08 (ZrO ₂ ) _0.92 , Kceracell, 0.22um, 50 wt% ) or 20 g of ScSZ-6 (6 mol% Sc ₂ O ₃ ), ethanol (SAMCHUN, purity 99.9%) and binder (PVB-76, SAMCHUN, 99%) were mixed and then ball milled to prepare a slurry. The prepared slurry was used to produce a thick film-type tape molded body using a tape casting (STC-14C) process.

Manufacture of anode (cathode) layer containing Ni, ScSZ (Ce, Gd) and LST37

NiO (Kceracell), 10ScSZ (ZrO ₂ doped with 10 % Sc ₂ O ₃ , 0.5% CeO ₂ and 0.5 % Gd ₂ O ₃ , Kceracell), LST37 (La _0.7 Sr _0.3 TiO ₃ , Kceracell), ethanol (SAMCHUN, Purity 99.9%) and binder (PVB-76, SAMCHUN, 99%) were mixed and then ball milled to prepare a slurry. The prepared slurry was used to produce a thick film-type tape molded body using a tape casting (STC-14C) process.

Manufacturing of ScSZ (Ce, Gd) solid electrolyte layer

10ScSZ (ZrO ₂ doped with 10% Sc ₂ O ₃ , 0.5% CeO ₂ and 0.5% Gd ₂ O ₃ , Kceracell), ethanol (SAMCHUN, 99.9% purity) and binder (PVB-76, SAMCHUN, 99%). After mixing, a slurry was prepared by ball milling. A tape molded body in the form of a thick film was produced from the prepared slurry using a tape casting (using a tape-casting machine, STC-14C) process.

Lamination and co-sintering processes

After stacking the thick film-shaped tape molded bodies (metal support, contact layer, anode layer, and solid electrolyte layer) obtained through the tape casting process, a hot pressing process (applying a pressure of about 20 MPa) was performed. Afterwards, the obtained laminate was sintered (maintained at 1350°C for 4 hours).

Manufacturing of an air electrode (anode) layer containing LSM and ScSZ (Ce, Gd) and a cell containing the same

To prepare the air cathode layer, LSM (Sr-doped LaMnO ₃ ) and 10ScSZ (10 mol% Sc ₂ O ₃ -doped ZrO ₂ ) were mixed at a volume ratio of 7:3 to prepare air cathode layer powder. An air cathode layer was formed by screen printing the air cathode layer powder on the solid electrolyte layer of the obtained sintered body using a screen printing plate with a thickness of 30 μm. Afterwards, heat treatment was performed at 1200°C to obtain a fuel cell.

Comparative Example 1: Ni-based metal support type solid oxide fuel cell without contact layer

The remaining layers except the contact layer were manufactured in the same manner as Preparation Example 1.

Comparative Example 2: STS-based metal support type solid oxide fuel cell without contact layer

The remaining layers except the contact layer were manufactured in the same manner as Preparation Example 2.

Figure 2 is a cross-sectional view comparing the microstructure of a Ni-based metal support type solid oxide fuel cell before and after reduction. Figures 2(a) and (b) show the microstructure before reduction, and Figures 2(c) and (d) show the microstructure after reduction. Additionally, Figures 2(a) and (c) show a fuel cell including a contact layer, and Figures 2(b) and (d) show a fuel cell not including a contact layer.

As a result of comparing the microstructure before and after reduction, it was confirmed that the microstructure of the metal support and anode layer in Figures 2(b) and (d) using a fuel cell without a contact layer had a large difference in density and particle size. You can. Due to the large difference in density and particle size, not only does it cause large deformation between the layers constituting the fuel cell cell, but the compatibility between the layers is poor, so it can be easily destroyed during a thermal gradient within the fuel cell cell. You can. Additionally, if the porosity changes suddenly from the metal support to the anode layer, it may cause a large difference in gas flow or distribution.

Meanwhile, referring to Figures 2(a) and (c), it can be seen that the microstructure difference between the metal support and the anode layer is alleviated by inserting the contact layer into the fuel cell cell. As microstructural differences within the fuel cell cell are alleviated, strain between layers is reduced, thermal fracture is reduced, compatibility is improved, and resistance to internal and external stress increases. You can. Additionally, by reducing rapid changes in porosity from the metal support to the anode layer, gas flow or distribution and current flow can be smoothed. Therefore, it can be seen that when the contact layer is included in the fuel cell cell, the change in microstructure before and after reduction is significantly reduced.

Figure 3 is a cross-sectional view comparing the microstructure of the STS-based metal support type solid oxide fuel cell. Figure 3(a) shows a fuel cell including a contact layer, and Figure 3(b) shows a fuel cell not including a contact layer. Comparing Figures 3(a) and (b), it can be seen that in the case of Figure 3(a), which includes a contact layer in the fuel cell cell, the difference in microstructure between the metal support and the anode layer is alleviated.

<Evaluation examples>

density experiment

The Image J program was used to measure the density of each layer constituting the fuel cell cell. Through the ImageJ program, the SEM image of each layer was first scanned. At this time, the sample appeared bright and the pores appeared dark, and the density was measured through this ratio. The density of each layer was measured before and after reduction of the fuel cell according to an embodiment of the present invention and depending on the presence or absence of a contact layer, and the results are shown in Table 1 below.

division Density (before reduction) Density (after reduction) With contact layer No contact layer With contact layer No contact layer Air cathode (anode) layer ~75% ~75% ~75% ~75% solid electrolyte layer ~99% ~99% ~99% ~99% Fuel electrode (cathode) layer ~92% ~92% ~75% ~75% contact layer ~82% - ~70% - metal support ~67% ~66% ~57% ~57%

As a result of observing the density of each layer in the cell constituting the fuel cell before and after reduction, as shown in Table 1 above, the density of the contact layer before reduction was found to be greater than the density of the metal support and less than the density of the anode layer. . In addition, it can be seen that even after reduction, the density of the contact layer is formed between the density of the metal support and the anode layer. Therefore, it can be confirmed that the difference in microstructure between the metal support and the anode layer is alleviated by adding the contact layer.

Measurement of thermal expansion coefficient

To measure the thermal expansion coefficient of each layer constituting the fuel cell cell, a thermomechanical analysis device (TA Instrument, Q400) was used to measure the temperature under the conditions of a load of 0.1 N and a N ₂ flow of 100 mL/min. Table 2 below lists the thermal expansion coefficient of each layer constituting the fuel cell manufactured according to Preparation Example 1 and Comparative Example 1.

Manufacturing Example 1 Comparative Example 1 solid electrolyte layer 10 ~ 11 ppm/℃ 10 ~ 11 ppm/℃ anode layer 12 ~ 14.5 ppm/℃ 12 ~ 14.5 ppm/℃ contact layer 13.5 ~ 16.5 ppm/℃ - metal support 15 ~ 18 ppm/℃ 15 ~ 18 ppm/℃

Referring to Table 2, the thermal expansion coefficient of the contact layer inserted in Preparation Example 1 was found to be 13.5 to 16.5 ppm/℃, and the value was between the thermal expansion coefficients of the metal support and the anode layer, resulting in a thermal expansion coefficient gradient. ) can have. In the case of Preparation Example 1 having the thermal expansion coefficient gradient, thermal fracture is reduced and compatibility is improved compared to Comparative Example 1, resulting in increased resistance to internal and external stress. Delamination between layers of fuel cell cells can be suppressed.

stress test

To evaluate the lifespan of a fuel cell, the stress resulting from cell destruction was measured. The stress may appear through microscopic pores at the contact surface between cell layers or discontinuous areas of the structure.

Figure 4 shows the radius of curvature formed when a contact layer (Preparation Example 1) or an anode layer (Comparative Example 1) is laminated on the top of the metal support, respectively. Comparing FIGS. 4(a) and 4(b), the particle size in FIG. 4(a) with the contact layer laminated appears to be relatively larger compared to FIG. 4(b) with the anode layer laminated, so the contact layer The radius of curvature that appears at the interface between the metal support and the metal support can also be wide. The stress applied to the fuel cell of Preparation Example 1 and Comparative Example 1 was calculated using the radius of curvature and Equation 1 below, and is shown in Table 3 below.

[Equation 1]

At this time, σ _m is the maximum stress that can be withstood just before failure occurs, and σ ₀ is is the nominal applied tensile stress, a is the length of the surface/internal crack, and ρ _t is This is the radius of curvature of the crack area.

Manufacturing Example 1 Comparative Example 1 σ _m (maximum stress) 28σ ₀ (a) ^1/2 63σ ₀ (a) ^1/2 σ ₀ (tensile stress) σ ₀ σ ₀ a (surface crack length) a a ρ _t (radius of curvature) 50 10 particle size ∼3 ㎛ ∼1 ㎛

Referring to Table 3, in Preparation Example 1 and Comparative Example 1 The σ _m (maximum stress) values were found to be 28σ ₀ (a) ^1/2 and 63σ ₀ (a) ^1/2 , respectively, and in the case of Preparation Example 1 with a contact layer, compared to Comparative Example 1 without a contact layer. It can be seen that the σ _m (maximum stress) value decreases to less than 1/2. Therefore, in the case where the contact layer is present, the stress applied to the fuel cell cell is significantly reduced, thereby suppressing interlayer delamination within the fuel cell cell, and further increasing the lifespan of the fuel cell cell and improving thermal cycle characteristics can be expected.

Above, the present invention has been described in detail with preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and changes can be made by those skilled in the art within the technical spirit and scope of the present invention. Change is possible.

10: solid oxide fuel cell 14: solid electrolyte layer
11: metal support 15: protective layer
12: contact layer 16: air electrode layer
13: anode layer 17: current collector

Claims (16)

metal support;
A contact layer laminated on the metal support and passing gas and electricity while acting as a buffer in terms of microstructure;
an anode layer laminated on top of the contact layer and producing water and electrons by combining ionized oxygen ions and injected hydrogen;
A solid electrolyte layer laminated on top of the anode layer, which prevents hydrogen and air from mixing and at the same time allows oxygen ions to pass through; and
It includes an air electrode layer laminated on top of the solid electrolyte layer and producing oxygen ions by reducing the injected air,
A metal support type solid oxide fuel cell, wherein the contact layer is a mixture of the composition of the metal support and the composition of the anode layer and has a thickness of 20 um to 30 um. According to paragraph 1,
A metal support type solid oxide fuel cell comprising a protective layer between the solid electrolyte layer and the air electrode layer. According to paragraph 2,
The protective layer is a metal support type solid oxide fuel cell containing Ce _1-y Ln _y O _2-β (Ln=Gd, Sm, Nd or La, y=0.1∼0.3, β=0∼0.2). According to paragraph 1,
A metal support type solid oxide fuel cell further comprising a current collector stacked on the upper part of the air electrode layer. According to paragraph 1,
A metal support type solid oxide fuel cell in which the metal support is one of Ni metal, Ni-Fe alloy, and STS (Stainless Steel). According to paragraph 1,
A metal support type solid oxide fuel cell in which the anode layer is a composite of NiO and rare earth-doped zirconia or a composite of NiO and rare earth-doped ceria. delete delete delete According to paragraph 1,
A metal support type solid oxide fuel cell in which the solid electrolyte layer is any one of rare earth-doped zirconia-based oxide, rare-earth-doped ceria-based oxide, and perovskite-based oxide. delete delete According to paragraph 1,
A metal support type solid oxide fuel cell in which the metal support component of the contact layer and the anode layer component have a volume ratio of 7:3 to 6:4. According to paragraph 1,
A metal support type solid oxide fuel cell, characterized in that the particle size of the contact layer is 0.3 ㎛ to 30 ㎛. delete According to paragraph 1,
A metal support type solid oxide fuel cell, characterized in that the thermal expansion coefficient of the contact layer is 10 (ppm/℃) to 20 (ppm/℃).