Fuel cell electrode and fuel cell comprising same

Abstract

A fuel cell electrode according to one embodiment of the present invention has a substrate and an oxide film on one surface or both surfaces of the substrate, wherein the oxide film comprises a spinel containing at least one of Co, Ni, Cu, Mn, Fe, and Cr.

Description

Electrode of a fuel cell and a fuel cell including the same

[0001] One embodiment of the present invention relates to an electrode of a fuel cell and a fuel cell including the same. Specifically, it relates to an electrode of a fuel cell capable of protecting the electrode from Cr gas by forming an oxide film on the surface of a substrate, and a fuel cell including the same.

[0002] Solid oxide fuel cells (SOFCs) and high-temperature water electrolysis cells (SOECs) operate at high temperatures.

[0003] High-temperature degradation is the biggest problem in the commercialization of SOFCs and SOECs, and among the various high-temperature degradation phenomena, Cr poisoning is known to be a very persistent and difficult problem to solve.

[0004] The stacks and systems of SOFCs and SOECs include various metal components, including metal separators, and high-temperature stainless steel with excellent oxidation resistance at high temperatures is generally used.

[0005] High-temperature stainless steel contains a large amount of Cr to form a high-temperature oxidation-resistant film.

[0006] In a high-temperature oxidizing atmosphere, Cr in stainless steel volatilizes into gas.

[0007] Volatile Cr migrates into the cell and is deposited on the surface of the electrode, forming inert / non-conductive compounds that degrade the electrode's performance.

[0008] Such volatilization of Cr and electrode poisoning are inevitable phenomena in SOFCs and SOECs, and much research has been conducted to suppress them.

[0009] Although a method of depositing a protective coating on metal surfaces, such as metal separators, has been proposed, there are difficulties in applying the protective coating due to the size or shape of many parts, with the exception of some components like separators.

[0010] In addition, although electrode materials with high resistance to Cr poisoning have been proposed, the inherent performance of such poison-resistant materials is significantly low, making them difficult to apply to actual cells.

[0011] Therefore, to ensure the durability of SOFC and SOEC stacks and systems, technology is required to protect the electrodes from external Cr gas.

[0012] One embodiment of the present invention provides an electrode of a fuel cell and a fuel cell including the same. Specifically, it provides an electrode of a fuel cell capable of protecting the electrode from Cr gas by forming an oxide film on the surface of a substrate, and a fuel cell including the same.

[0013] An electrode of a fuel cell according to one embodiment of the present invention has an oxide film on one or both sides of a substrate, and the oxide film comprises a spinel containing one or more of Co, Ni, Cu, Mn, Fe, and Cr.

[0014] Spinel may contain one or more of Co and Ni.

[0015] Spinel may contain one or more of Co and Ni and Cr.

[0016] The thickness of the oxide film can be 10 to 50 μm.

[0017] The porosity of the oxide film can be 10 to 50%.

[0018] A fuel cell according to one embodiment of the present invention comprises a fuel electrode, an electrolyte layer located on the fuel electrode, and an air electrode located on the electrolyte layer, wherein the air electrode comprises a substrate and an oxide film located on one or both sides of the substrate, and the oxide film comprises one or more of Co, Ni, Cu, Mn, Fe, and Cr.

[0019] Spinel may further contain one or more of Co and Ni.

[0020] Spinel may contain one or more of Co and Ni and Cr.

[0021] The thickness of the oxide film can be 10 to 50 μm.

[0022] The porosity of the oxide film can be 10 to 50%.

[0023] The oxide film can be located on the upper surface of the substrate.

[0024] According to one embodiment of the present invention, Cr gas is consumed externally through an oxide film and prevented from reaching the electrode.

[0025] The oxide film reacting with Cr has excellent electrical conductivity, so it can act as a current collector between the cell and the separator.

[0026] The oxide film does not lose electrical conductivity even after reacting with Cr, and performance degradation does not occur as it absorbs Cr.

[0027] FIG. 1 is a schematic diagram showing a cross-section of a fuel cell in one embodiment of the present invention.

[0028] Figure 2 is a scanning electron microscope (SEM) image of a cross-section of the air electrode and electrolyte layer prepared in Example 2.

[0029] Figure 3 is the X-ray diffraction (XRD) analysis result of the oxide film prepared in Example 1.

[0030] Figure 4 is a transmission electron microscope (TEM) image of the oxide film prepared in Example 1 after exposure to Cr vapor.

[0031] Figure 5 is a graph of the electrical conductivity measurement results before and after Cr exposure for the electrode prepared in Example 1.

[0032] Figure 6 shows the results of measuring the impedance after Cr exposure for the electrode prepared in Example 1.

[0033] Figure 7 shows the results of measuring the impedance after Cr exposure for the electrode prepared in Comparative Example 1.

[0034] Figure 8 is a scanning electron microscope (SEM) image of the electrode prepared in Example 1 after evaluating Cr exposure stability.

[0035] Figure 9 is a scanning electron microscope (SEM) image of the electrode prepared in Comparative Example 1 after the evaluation of Cr exposure stability.

[0036] Figure 10 shows the results of manufacturing a full cell in Example 2 and evaluating long-term stability.

[0037] Figure 11 is a scanning electron microscope (SEM) image of the electrode after manufacturing the full cell in Example 2 and evaluating long-term stability.

[0038] Figure 12 is a scanning electron microscope (SEM) image of the electrode after manufacturing a full cell in Comparative Example 2 and evaluating long-term stability.

[0039] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0040] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0041] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0042] In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components.

[0043] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0044]

[0045] An electrode (30) of a fuel cell (100) according to one embodiment of the present invention has a substrate (31) and an oxide film (32) on one or both sides of the substrate (31), and the oxide film (32) includes a spinel comprising one or more of Co and Ni.

[0046] According to one embodiment of the present invention, when the spinel in the oxide film (32) is exposed to Cr vapor at a high temperature, it reacts with Cr, and the spinel that reacted with Cr actually has increased electrical conductivity, so the oxide film functions as a current collector and can protect the electrode (30) from Cr gas introduced from the outside.

[0047] The fuel cell (100) can be a solid oxide fuel cell (SOFC) and a high-temperature water electrolysis cell (SOEF).

[0048] The electrode (30) can be an air electrode, and the substrate (31) of the electrode (30) is not particularly limited, but specifically may include lanthanum strontium cobalt oxide (LSC).

[0049] The oxide film (32) includes a spinel containing one or more of Co, Ni, Cu, Mn, Fe, and Cr. More specifically, it may include a spinel containing Co and Ni.

[0050] These spinels react with Cr at high temperatures and absorb Cr, so that even if spinels such as Co-Cr, Ni-Cr, and Co-Ni-Cr are formed, the electrical conductivity actually increases and the electrode (30) can be protected from Cr gas introduced from the outside.

[0051] Spinel may contain one or more of Co and Ni. These elements are advantageous in terms of reactivity with Cr, so that the electrode (30) can be protected from Cr gas.

[0052] More specifically, it may include one or more of Co and Cr and Cr. In this case, the Cr may be absorbed from volatilized Cr gas during the fuel cell operation. Cr may be included in the total spinel at 5 to 50 at%.

[0053] Spinel can be represented by the following chemical formula 1.

[0054] [Chemical Formula 1]

[0055] (M 1 x M 2 1-x )3O4

[0056] (M in Chemical Formula 1 1 and M 2 represents one or more of Co, Ni, Cu, Mn, Fe, and Cr, and M 1 and M 2 are distinct from each other, and x is between 0.1 and 1.)

[0057] The thickness of the oxide film (32) may be 10 to 50 μm. If the thickness of the oxide film (32) is too thin, it may be difficult to sufficiently protect the electrode (30) from Cr gas by the oxide film (32). If the thickness of the oxide film (32) is too thick, it may hinder the movement of oxygen gas and degrade performance. More specifically, the thickness of the oxide film (32) may be 15 to 30 μm.

[0058] The porosity of the oxide film (32) may be 10 to 50%. If the porosity is too low, it may hinder the movement of oxygen gas and reduce the performance of the battery. If the porosity is too high, the proportion of spinel may be too low, making it difficult to adequately protect the electrode (30) from Cr gas. More specifically, the porosity of the oxide film (32) may be 20 to 40%. The porosity can be measured by electron microscope image analysis.

[0059] FIG. 1 schematically shows a fuel cell (100) according to one embodiment of the present invention.

[0060] As shown in FIG. 1, a fuel cell (100) according to one embodiment of the present invention comprises a fuel electrode (10), an electrolyte layer (20) located on the fuel electrode (10), and an air electrode (30) located on the electrolyte layer (20). The air electrode (30) comprises a substrate (31) and an oxide film (32) located on one or both sides of the substrate (31), and the oxide film (32) comprises a spinel comprising one or more of Co, Ni, Cu, Mn, Fe, and Cr.

[0061] According to one embodiment of the present invention, when the spinel in the oxide film (32) is exposed to Cr vapor at a high temperature, it reacts with Cr, and the spinel that reacted with Cr actually has increased electrical conductivity, so the oxide film functions as a current collector and can protect the air electrode (30) from Cr gas introduced from the outside.

[0062] The fuel cell (100) can be a solid oxide fuel cell (SOFC) and a high-temperature water electrolysis cell (SOEF).

[0063] The substrate (31) of the air electrode (30) is not particularly limited, but specifically may include lanthanum strontium cobalt oxide (LSC).

[0064] The oxide film (32) includes a spinel containing one or more of Co, Ni, Cu, Mn, Fe, and Cr. More specifically, it may include a spinel containing Co and Ni.

[0065] These spinels react with Cr at high temperatures and absorb Cr, so that even if spinels such as Co-Cr, Ni-Cr, and Co-Ni-Cr are formed, the electrical conductivity actually increases, and the air electrode (30) can be protected from Cr gas introduced from the outside.

[0066] Spinel may contain one or more of Co and Ni. These elements are advantageous in terms of surface, so that the air electrode (30) can be protected from Cr gas.

[0067] More specifically, it may include one or more of Co and Cr and Cr. In this case, the Cr may be absorbed from volatilized Cr gas during the fuel cell operation. Cr may be included in the total spinel at 5 to 50 at%.

[0068] Spinel can be represented by the following chemical formula 1.

[0069] [Chemical Formula 1]

[0070] (M 1 x M 2 1-x )3O4

[0071] (M in Chemical Formula 1 1 and M 2 represents one or more of Co, Ni, Cu, Mn, Fe, and Cr, and M 1 and M 2 are distinct from each other, and x is between 0.1 and 1.)

[0072] The thickness of the oxide film (32) may be 10 to 50 μm. If the thickness of the oxide film (32) is too thin, it may be difficult to sufficiently protect the electrode (30) from Cr gas by the oxide film (32). If the thickness of the oxide film (32) is too thick, it may hinder the movement of oxygen gas and reduce performance. More specifically, the thickness of the oxide film (32) may be 15 to 30 μm.

[0073] The porosity of the oxide film (32) may be 10 to 50%. If the porosity is too low, it may hinder the movement of oxygen gas and reduce the performance of the battery. If the porosity is too high, the proportion of spinel is too low, making it difficult to adequately protect the air electrode (30) from Cr gas. More specifically, the porosity of the oxide film (32) may be 20 to 40%.

[0074] As shown in FIG. 1, the oxide film (32) can be located on the upper surface of the substrate (31).

[0075] Additionally, the electrolyte layer (20) is located on the fuel electrode (10) and, while not particularly limited, may include gadolinium-doped ceria (GDC) and yttria-stabilized zirconia (YSZ).

[0076] The fuel electrode (10) may include nickel and yttria-stabilized zirconia (Ni-YSZ).

[0077] The method of forming the oxide film (32) is not particularly limited, and it can be manufactured by preparing a paste containing spinel powder, applying the paste onto a substrate, and sintering it.

[0078]

[0079] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0080]

[0081] Example 1: Preparation of an electrode including an oxide film (with Co-Ni layer)

[0082] Co-Ni spinel was prepared by the glycine-nitrate process and mixed with a solvent to produce a paste. This paste was deposited onto a lanthanum strontium cobalt oxide (LSC) substrate by screen printing and sintered at 950°C to form an oxide film with a thickness of approximately 20 μm.

[0083]

[0084] Comparative Example 1: Electrode without oxide layer (No Co-Ni layer)

[0085] A lanthanum strontium cobalt oxide (LSC) substrate was prepared as an electrode without an oxide film.

[0086] Experimental Example 1: X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) Analysis

[0087] X-ray diffraction (XRD) analysis was performed on the electrode prepared in Example 1, and after exposing the electrode prepared in Example 1 to Cr vapor at a temperature of 800°C for 100 hours, X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) analysis were performed and are shown in Figures 3 and 4.

[0088] As shown in Figure 3, before exposure to Cr, the spinel structure after synthesis of Co-Ni oxide was observed, and after exposure to Cr, it was confirmed that Co-Cr spinel was formed by reacting with Cr.

[0089] In addition, as shown in Figure 4, it can be seen that Co-Cr spinel is formed on the surface when exposed to Cr vapor.

[0090] As shown in Figures 3 and 4, it can be confirmed that the oxide film contains 15 at% Cr after exposure to Cr vapor.

[0091] Experimental Example 2: Measurement of Electrical Conductivity

[0092] The electrical conductivity of the electrode prepared in Example 1 before Cr exposure (Co-Ni Spinel Oxide) and after exposure (Co-Ni-Cr Spinel Oxide) was measured and is shown in Figure 5.

[0093] As shown in Figure 5, it can be confirmed that an electrical conductivity level suitable for use as a current collector is obtained in SOFCs and SOECs.

[0094] Furthermore, it can be confirmed that when Co-Ni spinel reacts with Cr to form Cr-containing spinel, the electrical conductivity actually increases. Consequently, it can be verified that the performance of the Co-Ni spinel current collector is not degraded but rather improved through the reaction with Cr.

[0095] Experimental Example 3: Half-cell fabrication, impedance measurement, and SEM observation

[0096] The electrodes prepared in Example 1 and Comparative Example 1 were exposed to Cr at 700°C at 24-hour intervals, and the increase in impedance was measured and shown in Figures 6 and 7, respectively.

[0097] In the case of Example 1, it was confirmed that the polarization resistance was maintained within 1 Ohm cm2 when measured for the same amount of time.

[0098] On the other hand, in the case of Comparative Example 1, approximately 20 Ohm cm⁻¹ for 144 hours due to Cr poisoning 2 It was confirmed that the polarization resistance increased up to.

[0099] In addition, after exposure to Cr, the surface of the oxide film was observed using a scanning electron microscope (SEM), and the images are shown in Figures 8 and 9.

[0100] In the case of Example 1, it was confirmed that a dense porous structure was maintained without the formation of reactants even after prolonged exposure to Cr. At this time, it was confirmed that the porosity was ~25%.

[0101] In the case of Comparative Example 1, it was confirmed that a large amount of reactants with Cr were produced.

[0102] Example 2 and Comparative Example 2: Preparation of a Full Cell

[0103] A full cell was prepared using the air electrode of Example 1, with the fuel electrode being Ni-YSZ and the electrolyte layer being YSZ-GDC. This is named Example 2. Additionally, a full cell was prepared using the air electrode of Comparative Example 1 instead of the air electrode of Example 1. This is named Comparative Example 2.

[0104] Figure 2 shows a scanning electron microscope (SEM) image of a cross-section of the air electrode and electrolyte layer prepared in Example 2.

[0105] Experimental Example 4: Long-term stability evaluation

[0106] Long-term stability at 700°C in an environment exposed to a large amount of Cr was evaluated using full cells prepared in Example 2 (With Co-Ni layer) and Comparative Example 2 (No Co-Ni layer).

[0107] 0.5 A / cm 2 When a long-term evaluation was conducted under constant current conditions, it was confirmed that in the case of Example 2, the initial performance was slightly lower but it operated stably and almost no voltage drop occurred. On the other hand, it was confirmed that in Comparative Example 2, the cell voltage decreased rapidly and performance degradation occurred.

[0108] In addition, after conducting a long-term evaluation, a cross-section of the cell was observed using a scanning electron microscope (SEM), and the image is shown in Figures 11 and 12.

[0109] In the case of Example 2, it can be confirmed that the reaction with Cr is effectively suppressed by maintaining a porous, dense electrode structure.

[0110] On the other hand, as in Comparative Example 2, a secondary phase with a dense structure formed through reaction with Cr was observed on the surface.

[0111] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also included within the scope of the present invention.

[0112] [Explanation of the symbol]

[0113] 100: Fuel cell, 10: Fuel electrode,

[0114] 20: Electrolyte layer, 30: Air electrode, Electrode

[0115] 31: Substrate, 32: Oxide film

Claims

1. An oxide film exists on a substrate and on one or both sides of the substrate, and The above oxide film is an electrode of a fuel cell comprising a spinel containing one or more of Co, Ni, Cu, Mn, Fe, and Cr.

2. In Paragraph 1, The above spinel is an electrode of a fuel cell comprising one or more of Co and Ni.

3. In Paragraph 2, The above spinel is an electrode of a fuel cell comprising one or more of Co and Ni and Cr.

4. In Paragraph 1, An electrode of a fuel cell having an oxide film thickness of 10 to 50 μm.

5. In Paragraph 1, An electrode of a fuel cell in which the porosity of the oxide film is 10 to 50%.

6. comprising a fuel electrode, an electrolyte layer located on the fuel electrode, and an air electrode located on the electrolyte layer, The above air electrode comprises a substrate and an oxide film located on one or both sides of the substrate, and The above oxide film is a fuel cell comprising a spinel containing one or more of Co, Ni, Cu, Mn, Fe, and Cr.

7. In Paragraph 6, The above spinel is a fuel cell containing one or more of Co and Ni.

8. In Paragraph 7, The above spinel is a fuel cell comprising one or more of Co and Ni and Cr.

9. In Paragraph 6, A fuel cell having an oxide film thickness of 10 to 50 μm.

10. In Paragraph 6, A fuel cell in which the porosity of the oxide film is 10 to 50%.

11. In Paragraph 6, The above oxide film is a fuel cell located on the upper surface of the above substrate.

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