KR102247686B1 - Self-transforming solid oxide cell and method of manufacturing the same - Google Patents

Abstract

The present invention provides a self-conversion solid oxide battery having excellent electrochemical performance, high thermal stability, and capable of reducing manufacturing processes and costs, and a method of manufacturing the same. Self-conversion solid oxide battery according to an embodiment of the present invention, the anode; A cathode disposed facing the anode; And an electrolyte disposed between the anode and the cathode; wherein the anode and the cathode are composed of the same solid oxide, have the same first crystal structure immediately after manufacture, and the anode is adapted to the atmosphere It has a second crystal structure different from the first crystal structure by being phase-shifted by self-transformation.

Description

Self-transforming solid oxide cell and method of manufacturing the same}

The technical idea of the present invention relates to a self-conversion solid oxide battery and a method of manufacturing the same.

Since hydrogen has a variety of uses, is a clean, efficient fuel, and exists very much on the planet, interest in hydrogen energy systems is increasing as an application for a renewable energy conversion system. As one of these hydrogen energy systems, the solid oxide fuel cell has advantages of high conversion efficiency, low pollutant emission, and excellent fuel flexibility. In addition, solid oxide fuel cells can be used as solid oxide electrolytic cells by adding _{H 2 O in reversible operation.} Therefore, solid oxide cells that can be used in both fuel cells and water-receiving cells are attracting attention as next-generation energy devices.

Solid oxide batteries can be classified into two types according to electrode configuration. The fuel electrode and the air electrode may be classified into an asymmetrical configuration using different electrode materials and a symmetrical configuration using the same electrode material. Conventional solid oxide batteries generally have an asymmetrical configuration, and are specifically composed of an anode and a cathode each including a different material with a dense electrolyte interposed therebetween. This asymmetrical configuration has an advantage of having excellent performance because the anode and the cathode are separately configured to contain materials optimized for each operating environment. However, when the anode and the cathode are made of different materials, there is a problem in that the manufacturing process is complicated, the manufacturing cost is increased, and the thermal and mechanical compatibility is reduced due to different coefficients of thermal expansion. In particular, it is necessary to additionally form a buffer layer in order to reduce thermal problems. Therefore, the solid oxide battery having an asymmetrical configuration is limited in commercialization despite its excellent electrochemical performance.

The symmetrical configuration is characterized by the use of the same material for the anode and cathode. In the symmetrical configuration, since the same material is used for the electrodes, the interface formed between the electrode and the electrolyte is the same, so that it is possible to overcome the limitations of the asymmetric configuration described above, such as a problem of reactivity between constituent materials or a problem of a difference in thermal expansion coefficient. . In addition, since the symmetrical configuration can be implemented using only one heat treatment step in electrode manufacturing, the manufacturing process is relatively simple and manufacturing cost is reduced. However, the symmetrical configuration has a lower limit in phase stability and electrochemical performance than the asymmetrical configuration. The reason is that it is difficult to find a material having structural stability, chemical stability, and high catalytic activity required at the same time in oxidation and reduction. Accordingly, there is a need for an electrode for a solid oxide battery that has excellent electrochemical performance, high thermal stability, and can reduce manufacturing processes and costs.

Korean Patent Registration No. 10-1549443

The technical problem to be achieved by the technical idea of the present invention is to provide a self-converting solid oxide battery that has excellent electrochemical performance, high thermal stability, and can reduce manufacturing processes and costs, and a method of manufacturing the same.

However, these problems are exemplary, and the technical idea of the present invention is not limited thereto.

A self-conversion solid oxide battery according to the technical idea of the present invention for achieving the above technical problem, the anode; A cathode disposed facing the anode; And an electrolyte disposed between the anode and the cathode; wherein the anode and the cathode are composed of the same solid oxide, have the same first crystal structure immediately after manufacture, and the anode is adapted to the atmosphere It has a second crystal structure different from the first crystal structure by being phase-shifted by self-transformation.

In some embodiments of the present invention, the first crystal structure may include a cationic irregular arrangement perovskite structure.

In some embodiments of the present invention, the second crystal structure may include a cationic ordered perovskite structure.

In some embodiments of the present invention, the atmosphere may be composed of a hydrogen-containing gas atmosphere.

In some embodiments of the present invention, the atmosphere may _{include H 2} O in the range of 3 vol% to 10 vol%.

In some embodiments of the present invention, the self-conversion may be performed at a temperature in the range of 600°C to 800°C.

In some embodiments of the present invention, the cathode is Pr _{0 . 5} Ba _{0 . 5} Mn _{0 . 85} Co _{0 . 15} O _{3 - δ} .

In some embodiments of the present invention, the anode is PrBaMn _{1 . 7} Co _{0 .3- x} O _{5 + δ} .

In some embodiments of the present invention, the anode may further include a metal eluate formed by eluting metal.

In some embodiments of the present invention, the metal eluate may contain cobalt.

A method of manufacturing a self-converting solid oxide battery according to the technical idea of the present invention for achieving the above technical problem is an anode disposed with an electrolyte interposed therebetween, comprising the same solid oxide, and having the same first crystal structure Forming a symmetrical electrode structure composed of a cathode and a cathode; Heating the symmetrical electrode structure in an atmosphere composed of a hydrogen-containing gas atmosphere; And forming a second crystal structure different from the first crystal structure by the anode being phase-shifted by self-transformation made by adapting to the atmosphere, thereby forming an asymmetric electrode structure.

In some embodiments of the present invention, the step of forming the symmetrical electrode structure may be performed by simultaneously forming the anode and the cathode by infiltrating a precursor solution into the support.

In some embodiments of the present invention, the support may have a three-layer configuration of a porous layer/dense layer/porous layer, one of the porous layers constituting the anode, and the other of the porous layers is the A cathode may be formed, and the dense layer may constitute the electrolyte.

In some embodiments of the present invention, the electrolyte is La _{0 . 9} Sr _{0 . 1} Ga _{0 . 8} Mg _{0 . 2} O _{3 - δ} may be included.

In some embodiments of the present invention, the electrolyte is La _{0 . 9} Sr _{0 . 1} Ga _{0 . 8} Mg _{0 . 2} O _{3 -δ} powder can be formed using a slurry formed by injecting brown herring fish oil, xylene, polyalkylene glycol, butyl benzyl phthalate, and an ethanol solvent containing polyvinyl butylal.

In the self-converting solid oxide battery according to the technical idea of the present invention, perovskite Pr _0.5 Ba _0.5 Mn _0.85 Co _0.15 O _3-δ (PBMCO) was applied to the anode and the cathode as an atmosphere adaptive material. The PBMCO changes to layered perovskite and metal in a fuel atmosphere, and maintains its original structure in an air atmosphere. In the fuel cell mode, the self-conversion solid oxide cell exhibited excellent electrochemical performance with a high maximum power density of ^{1.10 W cm -2 at 800° C., and very good stability for 200 hours without using a catalyst.} In the water electrolysis mode, a current density of -0.42 A cm ^-2 _{was shown for 3 vol.% H 2} O, and a current density of -0.62 A cm ^-2 was shown for 10 vol.% H _{2 O.} In addition, it exhibited a battery voltage of 1.3 V at 800°C. In the reversible cycle test, the conversion cell can maintain a uniform voltage for 30 hours at +/- 0.2 A cm ^-2 _{for 10 vol% H 2 O.}

Therefore, the self-conversion solid oxide battery can provide excellent electrochemical performance and high thermal stability, and by configuring the anode and the cathode of the same material, the manufacturing process can be simplified, and the manufacturing cost can be reduced. can do.

The above-described effects of the present invention have been described by way of example, and the scope of the present invention is not limited by these effects.

1 is a schematic diagram showing a self-conversion solid oxide battery according to the technical idea of the present invention.
2 is a flowchart illustrating a method of manufacturing a self-conversion solid oxide battery according to the technical idea of the present invention.
3 is a schematic diagram showing a double-layer perovskite structure as a perovskite structure material constituting a self-converting solid oxide battery according to an embodiment of the present invention.
4 is a schematic diagram showing a phase shift and metal elution under operating conditions for an electrode constituting a self-converting solid oxide battery according to an embodiment of the present invention.
5 is a graph showing X-ray diffraction analysis under operating conditions for an electrode constituting a self-converting solid oxide battery according to an embodiment of the present invention.
6 is a graph showing X-ray diffraction analysis of an electrode constituting a self-converting solid oxide battery according to an embodiment of the present invention.
7 is a graph showing an X-ray photoelectron spectrum analysis of an electrode constituting a self-converting solid oxide battery according to an embodiment of the present invention.
8 is a scanning electron microscope photograph showing a cross section of a self-converting solid oxide battery according to an embodiment of the present invention.
9 are scanning electron micrographs of each configuration of a self-converting solid oxide battery according to an embodiment of the present invention.
10 is a graph showing an impedance spectrum of a self-converting solid oxide battery according to an embodiment of the present invention.
11 is a graph showing electrochemical characteristics of a self-converting solid oxide battery according to an embodiment of the present invention.
12 is a graph showing voltage and power density versus current density of a self-converting solid oxide battery according to an embodiment of the present invention.
13 is a table comparing the electrochemical performance of a self-converting solid oxide battery with a conventional battery according to an embodiment of the present invention.
14 is a graph showing a voltage change according to a current density according to an atmospheric atmosphere in a water electrolysis mode for a self-converting solid oxide battery according to an embodiment of the present invention.
15 is a graph showing the stability of a self-converting solid oxide battery according to an embodiment of the present invention.
16 is a graph showing long-term stability of a self-converting solid oxide battery according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more completely explain the technical idea of the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, and The scope of the technical idea is not limited to the following examples. Rather, these embodiments are provided to make the present disclosure more faithful and complete, and to completely convey the technical idea of the present invention to those skilled in the art. In the present specification, the same reference numerals refer to the same elements. Furthermore, various elements and areas in the drawings are schematically drawn. Therefore, the technical idea of the present invention is not limited by the relative size or spacing drawn in the accompanying drawings.

Compared to a solid oxide battery having an asymmetrical configuration, a solid oxide battery having a symmetrical configuration has practical advantages such as excellent compactness, a simple manufacturing process, and a cost reduction, and thus interest is increasing. However, the symmetrical configuration has limitations in terms of phase stability and electrochemical performance. Accordingly, the technical idea of the present invention is to propose a self-transforming solid oxide battery based on an atmospheric adaptive material in order to implement a high-performance battery by overcoming the above-described limitations. The self-conversion solid oxide battery may include both the advantages of an asymmetrical configuration and a symmetrical configuration. In the present specification, the atmosphere-adaptive materials refer to materials having high catalytic activity by changing structural properties such as phase and composition by themselves depending on the atmosphere.

1 is a schematic diagram showing a self-conversion solid oxide battery 100 according to the technical idea of the present invention.

Referring to FIG. 1, the self-conversion solid oxide battery 100 includes an anode 110, a cathode 120 disposed facing the anode 110, and oxygen disposed between the anode 110 and the cathode 120. It includes an electrolyte 130 which is an ion conductive solid oxide.

In addition, the anode 110 may include a metal eluate 140 formed by eluting metal during operation. The metal eluate 140 may contain cobalt, however, this is exemplary, and the technical idea of the present invention is not limited thereto.

The electrochemical reaction of the self-converting solid oxide cell 100 is _{anodic reaction in which oxygen gas O 2} at the cathode 120 is changed to oxygen ions O ^2- and fuel and electrolyte at the anode 110, as shown in the following reaction equation. It consists of a cathodic reaction in which oxygen ions that have been moved through react to form water. The fuel may include hydrogen gas (H ₂ ) or a hydrocarbon, for example, CH ₄ , C ₃ H ₈ , and the like.

<Reaction Scheme>

Anode ^{_{reaction: 1/2 O 2 + 2e - -}} > O 2-

Cathode ^{_{reaction: H 2 + O 2- ->}} H 2 O + 2e -

In the cathode 120 of the self-converting solid oxide battery 100, oxygen adsorbed on the electrode surface undergoes dissociation and surface diffusion to meet the electrolyte 130, the cathode 120, and the three-phase interface (triple phase) where the pores (not shown) meet. boundary) to obtain electrons to become oxygen ions, and the generated oxygen ions move to the anode 110, which is the anode, through the electrolyte 130.

In the anode 110 of the self-converting solid oxide cell 100, the moved oxygen ions combine with hydrogen contained in the fuel to generate water. At this time, hydrogen discharges electrons to ^{change into hydrogen ions (H +} ), and combines with the oxygen ions. The discharged electrons move to the cathode 120 through a wiring (not shown) to convert oxygen into oxygen ions. Through such electron transfer, the self-converting solid oxide battery 100 may perform a battery function.

The anode 110 and the cathode 120 may have the same material and structure immediately after manufacture. The anode 110 and the cathode 120 may include the same solid oxide, and may have the same first crystal structure immediately after manufacture. The anode 110 and the cathode 120 may have a perovskite structure. The perovskite structure may be a single perovskite or a double layer perovskite structure. In addition, the anode 110 and the cathode 120 may include a cationic irregular arrangement perovskite structure.

In this way, when the anode 110 and the cathode 120 are made of the same material, since there is no difference in the coefficient of thermal expansion between the anode 110 and the cathode 120, the difference in the coefficient of thermal expansion occurs during manufacture. Can prevent possible defects. In addition, since the anode 110 and the cathode 120 can be simultaneously manufactured in the same process, the manufacturing process can be simplified and economical efficiency can be increased. The anode 110 and the cathode 120 may be symmetrical with respect to the electrolyte 130. For example, the anode 110 and the cathode 120 may have a symmetrical structure with respect to the electrolyte 130 or may include a symmetrical material.

The anode 110 may have a second crystal structure different from the first crystal structure by being phase-shifted by self-transformation made by adapting to the atmosphere. The second crystal structure may include a cationic ordered perovskite structure. The atmosphere may be composed of a hydrogen-containing gas atmosphere, and the atmosphere may _{include H 2} O in the range of 3 vol% to 10 vol%. The self-conversion may be performed at a temperature in the range of 600°C to 800°C. This self-conversion may be implemented by a separate heat treatment process, or may be implemented during the operation of the self-conversion solid oxide battery 100.

The anode 110 and the cathode 120 are Pr _{0 immediately after manufacture. 5} Ba _{0 . 5} Mn _{0 . 85} Co _{0 . 15} O _{3 - δ} . On the other hand, after the self-conversion is performed, the anode 110 is PrBaMn _{1 . 7} Co _{0 .3-x} O _5+δ may be included. In this case, the material constituting the cathode 120 may not be changed. However, this is exemplary and the technical idea of the present invention is not limited thereto.

As a material constituting the anode 110 and the cathode 120, Pr _{0 . 5} Ba _{0 . 5} MnO _{3 -δ} (PBMO) can be proposed, because it has excellent chemical stability and structural stability, and the mixed valence Mn ^{4 +} /Mn ^{3 +} /Mn ^{2 + can accept electrons to accelerate the reaction.} Because it has. In addition, since perovskite oxide can flexibly select an element, catalytic activity can be controlled by doping at the A-position and doping at the B-position. Recently, Kwon et al. reported an elution phenomenon in a PBMO system by substituting a transition metal for manganese. According to a conventional study, among transition metals, cobalt is known to be the easiest material for doping and elution as a dopant for air electrodes and fuel electrodes. In general, doping the air electrode material with cobalt increases the oxygen depletion concentration and improves the electrical conductivity. In the fuel electrode, the eluted cobalt performs the function of a catalyst to improve electrochemical performance. In summary, Pr _{0 . 5} Ba _{0 . 5} Mn _{0 . 85} Co _{0 . 15} O _{3 -δ} (PBMCO) has a single perovskite structure in which a cubic crystal layer and a hexagonal crystal layer are mixed. When exposed to hydrogen, the structure changes and cobalt is eluted to form a perovskite structure in which cations are regularly arranged. Accordingly, in order to obtain a cobalt doping effect for the cathode 120 corresponding to the air electrode, and obtain a cobalt elution effect for the anode 110 corresponding to the fuel electrodes, the PBMCO can be selected as the atmosphere adaptive material. have. In order to increase the surface area and electrochemical performance of the electrodes, penetration technology can be applied to the manufacturing process. The conversion battery formed with the electrode materials can be expected to have excellent electrochemical performance and stability compared to conventional symmetric batteries.

The electrolyte 130 is not particularly limited as long as it can be generally used in the present technical field. For example, the electrolyte 130 may be a stabilized zirconia system such as yttria stabilized zirconia (YSZ) and scandia stabilized zirconia (ScSZ); A ceria system to which rare earth elements such as Samaria-doped ceria (SDC) and gadolinia-doped ceria (GDC) are added; Other LSGM ((La, Sr)(Ga, Mg)O ₃ ) system; And the like. In addition, the electrolyte 130 may include lanthanum gallate doped with strontium or magnesium. For example, the electrolyte 130 is La _{0 . 9} Sr _{0 . 1} Ga _{0 . 8} Mg _{0 . 2} O _{3 -δ} (LSGM 9182).

Although not shown, it may further include a buffer layer positioned between the anode 110 and the electrolyte 130 to provide smooth contact. The buffer layer may perform a function of alleviating distortion of the crystal lattice between the anode 110 and the electrolyte 130, for example. The buffer layer may include, for example, the _{LDC (La 0. 4 Ce 0} . 6 O 2 -δ).

Since the self-conversion solid oxide battery 100 can be manufactured using a conventional method known in various documents in the relevant technical field, a detailed description thereof will be omitted herein. In addition, the self-converting solid oxide battery 100 may be applied to various structures such as a tubular stack, a flat tubular stack, and a planar type stack. The self-conversion solid oxide battery 100 may be in the form of a stack of unit cells. For example, a unit cell (MEA, Membrane and Electrode Assembly) composed of an anode 110, a cathode 120, and an electrolyte 130 is stacked in series, and a separator electrically connecting them between the unit cells A (separator) is interposed so that a stack of unit cells can be obtained.

The self-converting solid oxide battery 100 may have a symmetrical electrode configuration immediately after manufacture, and may have an asymmetrical electrode configuration during operation. Specifically, the self-conversion solid oxide battery 100 may have a symmetrical configuration in which the anode 110 and the cathode 120 are made of the same material. On the other hand, during operation, the anode 110 adapts to the atmosphere and self-converts by phase shifting and metal elution, so that the anode 110 may change into an asymmetrical configuration having a different material or a different structure from the cathode 120.

The self-conversion solid oxide battery 100 can be manufactured in a symmetrical configuration, thereby simplifying the manufacturing process, minimizing thermal problems, and providing excellent phase stability and electrochemical performance as it changes to an asymmetrical configuration during operation. . That is, since the atmospheric environment of the anode 110 as the fuel electrode and the cathode 120 as the air electrode are very different, the problem that the phase becomes unstable and the electrochemical performance is deteriorated in the symmetrical electrode configuration is compared to the asymmetrical electrode configuration formed by self-conversion. Can be eliminated or minimized.

2 is a flow chart showing a method (S100) of manufacturing a self-conversion solid oxide battery according to the technical idea of the present invention.

Referring to FIG. 2, a method of manufacturing a self-converting solid oxide battery (S100) is a symmetric type composed of an anode and a cathode disposed with an electrolyte interposed therebetween, including the same solid oxide, and having the same first crystal structure. Forming an electrode structure (S110); Heating the symmetrical electrode structure in an atmosphere composed of a hydrogen-containing gas atmosphere (S120); And a step (S130) of forming an asymmetrical electrode structure by allowing the anode to have a second crystal structure different from the first crystal structure by being phase-shifted by self-transformation made by adapting to the atmosphere.

The forming of the symmetrical electrode structure may be performed by simultaneously forming the anode and the cathode by infiltrating a precursor solution into the support.

The support has a three-layer configuration of a porous layer/dense layer/porous layer, one of the porous layers constitutes the anode, the other of the porous layers constitutes the cathode, and the dense layer contains the electrolyte. Configurable.

The electrolyte is La _{0 . 9} Sr _{0 . 1} Ga _{0 . 8} Mg _{0 . 2} O _{3 - δ} may be included. The electrolyte is _{a slurry formed by injecting La 0.9} Sr _0.1 Ga _0.8 Mg _0.2 O _3-δ powder into an ethanol solvent containing brown herring fish oil, xylene, polyalkylene glycol, butyl benzyl phthalate, and polyvinyl butyral. It can be formed using.

Hereinafter, the perovskite crystal structure material will be described in detail.

3 is a schematic diagram showing a double-layer perovskite structure as a perovskite structure material constituting a self-converting solid oxide battery according to an embodiment of the present invention.

Referring to Figure 3, a double layer perovskite structure is shown. The perovskite structure can be largely divided into a single perovskite structure and a double-layer perovskite structure. A single perovskite structure may have the formula of _{ABO 3.} In the single perovskite structure, elements having a relatively large ion radius may be located at the A-site, which is a corner position of a cubic lattice, and 12 coordination numbers (CN , Coordination number). For example, a rare earth element, an alkaline rare earth element, and an alkaline element may be located in the A-position. Elements having a relatively small ion radius may be located in the B-site, which is a body center position of the cubic lattice, and may have a coordination number of 6 by oxygen ions. For example, a transition metal such as cobalt (Co) or iron (Fe) may be located at the B-site. Oxygen ions may be located in each face center of the cubic lattice. Such a single perovskite structure can cause structural displacement when other substances are substituted in the A-site (site), and its nearest oxygen ions ( There may be structural mutations in the octahedron of _{BO 6} consisting of 6).

The double perovskite structure shown in FIG. 3 has a crystal lattice structure in which two or more elements are regularly arranged at the A-site, for example, AA'B ₂ O _{5 +δ.} It may have the formula of. Specifically, in the lanthanide compound having a double-layer perovskite structure, the _{stacking permutation of [BO 2} ]-[AO]-[BO ₂ ]-[A'O] may be repeated along the c-axis. For example, B may be manganese (Mn), A may be a lanthanide group including yttrium (Y) or praseodymium (Pr), and A′ may be barium (Ba). Reduction in a hydrogen atmosphere can change from a single perovskite structure to a double layer perovskite structure. This double-packed perovskite structure can accelerate the movement of oxygen ions and improve thermal and chemical stability. In addition, it has high electrical conductivity in a hydrogen atmosphere and can exhibit excellent performance with thermal and chemical stability.

Hereinafter, an embodiment of a self-conversion solid oxide battery according to the technical idea of the present invention will be described as a specific experimental example.

In order to form a self-converting solid oxide cell, an infiltration technique was applied. First, a scaffold and a precursor solution were prepared. The support was composed of an ion conductor, and had a three-layer configuration of a porous layer/dense layer/porous layer by using a double-sided tape casting method. _{Subsequently, La 0.9} Sr _0.1 Ga _0.8 Mg _0.2 O _3-δ (LSGM) powder formed using a solid phase reaction was prepared. The LSGM powder was mixed with brown menhaden fish oil (Tape casting warehouse), xylene (Aldrich, 98.5+%), polyalkylene glycol (Tape casting warehouse), and butyl benzyl phthalate. phthalate, Tape casting warehouse), and polyvinyl butyral (Tape casting warehouse) was added to ethanol to form a slurry for double-sided tape casting. A green tape containing 50 wt% LSGM and 50 wt% graphite for forming a porous layer was attached to the upper side of the tape containing 100 wt% LSGM. Subsequently, a perforated tape was attached for the porous layer. Subsequently, the three-layer tape was heated at 1475°C for 5 hours.

The precursor solution is Pr(NO ₃ ) ₃ 6H ₂ O (Aldrich, 99.9%), Ba(NO ₃ ) ₂ (Aldrich, 99+%), Mn(NO ₃ ) ₂ (Aldrich, 98%), Co(NO ₃ ) ₂ 6 H ₂ O (Aldrich, 98+%) and citric acid were added and dissolved in deionized water to form. After heat treatment of the precursor solution to form a high concentration solution by reducing the amount of the solvent, ammonia was additionally added to the precursor solution. The formed high-concentration precursor solution was permeated into the porous layer of the three-layered support, followed by sintering at 450° C. for 20 minutes. The self-conversion solid oxide battery was formed by repeating until it became 45 wt% with respect to the initial amount.

The structure of the self-converting solid oxide battery was analyzed at an angle ranging from 20 degrees to 60 degrees using an X-ray diffraction apparatus (Bruker D8 Advance). The microstructure of the self-converting solid oxide battery was analyzed using a scanning electron microscope (Nova SEM) and a transmission electron microscope (JEOL, JEM-2100F). Using an ESCALAB 2 50XI (Thermo Fisher Scientific) apparatus having a monochromatic Al-Kα (ultraviolet He1, He2) X-ray source, X-ray photoelectron spectrum analysis of the self-converting solid oxide battery was performed. In order to measure the electrochemical performance of the self-converting solid oxide battery, a standard 4-point probe technique was performed using a BioLogic Potentiostat device. In order to measure the electrochemical performance, a current collector having a silver paste was prepared by contacting a silver wire with both electrodes of an electrolyte supporting battery. Then, the cell was sealed on a 10 mm diameter alumina tube using a ceramic adhesive (Aremco, Ceramabond 552).

In order to analyze the electrochemical performance for the fuel cell mode of the self-converting solid oxide cell, _{hydrogen containing 3 vol% H 2} O was injected into the fuel electrode region, and air was injected into the air electrode region. In order to analyze the electrochemical performance of the self-conversion solid oxide cell for the electrochemical cell mode, _{hydrogen containing 10 vol% H 2} O was injected into the fuel electrode. At the same time, an AC impedance meter was used to measure the open circuit voltage (OCV) for a frequency range of ^{10 -1} Hz to 10 ⁴ Hz, and an area specific resistance (ASR) was calculated for an active electrode area of ^{0.36 cm 2.}

4 is a schematic diagram showing a phase shift and metal elution under operating conditions for an electrode constituting a self-converting solid oxide battery according to an embodiment of the present invention.

Referring to FIG. 4, the phase shift and elution of cobalt metal of PBMCO, an atmospheric adaptive material constituting the anode, are shown. As shown on the left, immediately after the self-conversion solid oxide battery is manufactured, both the anode and the cathode sintered in an air atmosphere exhibit a single perovskite structure, and cobalt-doped PBMO (Pr _0.5 Ba _0.5 Mn _0.85 Co _0.15 O _3-δ ), i.e. PBMCO. The structure of the PBMCO may be referred to as a cation disordered perovskite structure.

On the other hand, during operation, the anode, which is the fuel electrode, is exposed to an atmosphere of hydrogen gas, so that a phase shift and elution of cobalt metal occur. That is, PrBaMn _{1 . 7 0 .3-} Co _x O appears as a _{5 + δ} + xCo, the following description will be represented by S-PBMCO. The structure of the S-PBMCO may be referred to as a cation ordered perovskite structure.

In order to confirm the phase shift and cobalt elution of the anode, X-ray diffraction and X-ray photoelectron spectrum analysis were performed.

5 is a graph showing X-ray diffraction analysis under operating conditions for an electrode constituting a self-converting solid oxide battery according to an embodiment of the present invention.

5, in order to analyze the change in the operating conditions of the self-converting solid oxide battery, the PBMCO-LSGM electrode formed by sintering in advance was maintained at each temperature in a hydrogen gas atmosphere for 2 hours while at the same time X-ray diffraction. This is the result of performing the analysis. The PBMCO has a single perovskite structure in which a cubic crystal layer and a hexagonal crystal layer are mixed at a temperature of 600° C. or less. The peak indicated by "H" in the left graph corresponds to the hexagonal crystal layer. This single perovskite sphere is changed at a temperature in the range of 700°C to 800°C so that the hexagonal crystal layer disappears and thus the peaks marked with "H" disappear. In addition, as shown in the graph on the right, a peak corresponding to the cobalt metal appears at about 45° C. at 800° C., which corresponds to the cobalt eluted from the PBMCO. From these results, it can be seen that a reduction reaction occurs in the fuel electrode at 800°C.

6 is a graph showing X-ray diffraction analysis of an electrode constituting a self-converting solid oxide battery according to an embodiment of the present invention.

Referring to FIG. 6A, it is a case of PBMCO sintered in an air atmosphere. The PBMCO before reduction clearly shows peaks for the crystal plane of a single perovskite and the crystal plane of LSGM.

Referring to FIG. 6B, it is the case of S-PBMCO reduced in a hydrogen gas atmosphere and a temperature of 800°C. After reduction, the S-PBMCO shows peaks for the perovskite crystal plane in which cations are regularly arranged and the crystal plane of LSGM. In addition, peaks corresponding to the eluted cobalt metal appeared. From these results, it can be seen that cobalt remains doped in PBMO at the cathode corresponding to the air electrode by the operation, but cobalt is eluted at the anode corresponding to the fuel electrode.

7 is a graph showing an X-ray photoelectron spectrum analysis of an electrode constituting a self-converting solid oxide battery according to an embodiment of the present invention.

의 온도 및 수소 가스 분위기에서 환원된 S-PBMCO에 대한 Co 2p 전자 영역 스펙트럼이고, (c)는 환원 전의 Pr_{0 . 5}Ba_{0 . 5}MnO₃ 에 대한 Ba 3d 전자 영역 스펙트럼이고, (d)는 환원 후의 PrBaMn₂O₅ 에 대한 Ba 3d 전자 영역 스펙트럼이고, (e)는 환원 전의 Pr_{0 . 5}Ba_{0 . 5}Mn_{0 . 85}Co_{0 . 15}O₃ 에 대한 Mn 2p_{3 /2} 전자 영역 스펙트럼이고, (f)는 환원 후의 PrBaMn_1.7Co_0.3O₅ 에 대한 Mn 2p_{3 /2} 전자 영역 스펙트럼이다.In Figure 7, (a) is a Co 2p electron domain spectrum for the PBMCO, (b) is 800

Co 2p electron domain spectrum for the reduced S-PBMCO in a temperature and hydrogen gas atmosphere, (c) is Pr _{0 before reduction. 5} Ba _{0 . 5} is the Ba 3d electron domain spectrum for MnO _{3 , (d) is the Ba 3d electron domain spectrum for PrBaMn 2} O ₅ after reduction, and (e) is the Pr _{0 before reduction. 5} Ba _{0 . 5} Mn _{0 . 85} Co _{0 . 15} O ₃ is the Mn 2p _{3 /2} electron domain spectrum, and (f) is the Mn 2p _{3 /2} electron domain spectrum of _{PrBaMn 1.7} Co _0.3 O _{5 after reduction.}

온도 및 수소 가스 분위기의 작동 조건에서 코발트가 용출됨을 의미한다.Referring to FIG. 7, the binding energy (BE) at the C 1s peak was found to be 284.5 eV. Since the peak of Co 2p and the peak of Ba 3d are overlapped, it is necessary to observe whether the peak of Ba 3d is changed. Therefore, referring to the results of (c) and (d) of FIG. 7, it can be seen that the Ba 3d peaks appear the same regardless of the phase shift caused by the reduction process. Therefore, it can be seen that the change in the X-ray photoelectron spectrum peak at the binding energy in the range of 770 eV to 810 eV is due to the change in the Co 2p peak caused by the phase transition from the PBMCO to S-PBMCO. As for the ratio of cobalt ions, Co ^{3 +} /Co ^{2 +} , the PBMCO was 0.56 and the S-PBMCO was increased to 1.43. The increase in this ratio is analyzed to be due to lattice defects and the corresponding cobalt oxidation (Co ^{2 +} => Co ^{3 + ).} In addition, as shown in (e) and (f) of FIG. 7, the oxidation of cobalt can also be confirmed by ^{reduction of manganese (Mn 3 +} or Mn ⁴⁺ => Mn ^{2 + ).} That is, ^{the content of Mn 3 +} and Mn ^{4 +} decreased by reduction, and the content of Mn ^{2 +} increased. The occurrence of cobalt metal peaks in the S-PBMCO is 800

It means that cobalt is eluted under operating conditions of temperature and hydrogen gas atmosphere.

8 is a scanning electron microscope photograph showing a cross section of a self-converting solid oxide battery according to an embodiment of the present invention.

Referring to FIG. 8, a cross section of a three-layer battery composed of PBMCO-LSGM/LSGM/S-PBMCO-LSGM is shown. The dense layer, the LSGM electrolyte, has a thickness of about 60 μm and shows excellent contact with both electrode layers. The cathode, which is an air electrode, is located on the upper side of the LSGM electrolyte, is a porous layer, and has a thickness of about 83 μm. The anode, which is a fuel electrode, is located under the LSGM electrolyte, has a porous layer, and has a thickness of about 83 μm.

9 are scanning electron micrographs of each configuration of a self-converting solid oxide battery according to an embodiment of the present invention.

9, (a) is an LSGM, (b) is a PBMCO-LSGM cathode that is an air electrode, and (c) is an S-PBMCO-LSGM anode that is a fuel electrode. It can be seen that the nano-sized particles of the LSGM are uniformly distributed and maintain the surface shape even after reduction. From the characteristics of microstructures having electrodes composed of nanostructures and thin electrolyte layers, it can be expected that self-converting solid oxide batteries have excellent electrochemical performance.

10 is a graph showing an impedance spectrum of a self-converting solid oxide battery according to an embodiment of the present invention.

Referring to FIG. 10, the results of operating the self-converting solid oxide battery having the configuration of PBMCO-LSGM/LSGM/S-PBMCP-LSGM in a hydrogen atmosphere at temperatures of 700°C, 750°C, and 800°C are shown. The ohmic losses of the self-converting solid oxide battery measured at the intersection of the real axis (Re Z) at high frequencies were 0.147 Ω cm ² at 800°C, 0.187 Ω cm ² at 750°C, and 0.244 Ω cm ² at 700°C. The polarization resistance of the electrodes determined by the difference between the two intersections of the real axis (Re Z) was 0.139 Ω cm ² at 800°C, 0.273 Ω cm ² at 750°C, and 0.530 Ω cm ² at 700°C. appear.

11 is a graph showing electrochemical characteristics of a self-converting solid oxide battery according to an embodiment of the present invention.

Referring to FIG. 11, (a) is an experiment and simulation request graph of a PBMCO-LSGM composite on an LSGM symmetric battery at an operating temperature of 700°C, 750°C, and 800°C, and (b) is a fit by an equivalent circuit. The resistances of the PBMCO-LSGM composite on a line-based LSGM symmetric cell are shown. In order to measure the cathode loss, a half-cell experiment was performed using the PBMCO-LSGM/LSGM/PBMCO-LSGM cells. From this, a fitted line was derived using EC-Lab software. Ohmic resistance was removed for direct comparison of the cathode polarization resistance at various operating temperatures. The cathode polarization resistance for PBMCO-LSGM was found to be 0.033 Ω cm ² at 800°C, 0.073 Ω cm ² at 750°C, and 0.189 Ω cm ² at 700°C. The fitted lines obtained based on the equivalent circuit shown in (b) of FIG. 11 agree well with the Nequest graph. In the above equivalent circuit, “L ₁ ”is the inductance by the cable, “R ₁ ” is the ohmic resistance, “R ₂ ”is related to the transfer of oxygen ions from the reaction site to the electrolyte lattice and charge transfer during diffusion, , “R ₃ ”can be induced by oxygen surface exchange, solid phase diffusion, and uncharged movement associated with gas phase diffusion. Specific values of these R ₂ , R ₃ and R _P (ie, R ₂ + R ₃ ) are shown in Table 1 below.

Table 1 shows the measured values of the resistance values obtained in the half-cell experiment and the fitted line values. In addition, Table 2 shows the results of the electrochemical impedance spectrum.

Temperature
(℃) Half-cell experiment (Ω cm ² ) Measures Fitted line value Cathode loss (R _p ) R ₂ R ₃ R _p 800 0.033 0.031 0.002 0.033 750 0.073 0.036 0.036 0.072 700 0.189 0.071 0.118 0.189

Temperature
(℃) Conversion battery experiment Half cell experiment Ohmic resistance
(Ω cm ² ) Polarization resistance
(Ω cm ² ) Cathode loss
(Ω cm ² ) 800 0.147 0.139 0.033 750 0.187 0.273 0.073 700 0.244 0.530 0.189

12 is a graph showing voltage and power density versus current density of a self-converting solid oxide battery according to an embodiment of the present invention.

Referring to FIG. 12, for a self-converting solid oxide battery at temperatures of 800°C, 750°C, and 700°C when hydrogen gas containing _{3% H 2 O is used as a fuel and air is used as an oxidizing agent.} The results are shown. Since the self-conversion solid oxide battery has a low polarization resistance, compared with a conventional symmetric battery as shown in Table 3 below, it exhibited a maximum power density of ^{1.10 W cm -2 at 800°C without adding a catalyst.} . As a result, the self-converting solid oxide battery can provide high catalytic activity by changing its structure with respect to the atmospheric atmosphere. This excellent catalytic activity performance is analyzed to be due to the penetration characteristics and a new structure with a thin electrolyte.

13 is a table comparing electrochemical performance of a self-converting solid oxide battery with conventional batteries according to an embodiment of the present invention.

Referring to FIG. 13, it can be seen that the electrochemical performance of the self-converting solid oxide battery is superior to that of conventional batteries.

14 is a graph showing a voltage change according to a current density according to an atmospheric atmosphere in a water electrolysis mode for a self-converting solid oxide battery according to an embodiment of the present invention.

및 1.3 V의 전지 전압에서, 3 vol% H₂O의 경우에는 -0.42 A cm^{- 2} , 10 vol% H₂O의 경우에는 -0.62 A cm^{- 2} 의 전류 밀도를 나타내었다. 따라서, 3 vol% H₂O와 같이 매우 적은 양의 H₂O 를 공급하여도, 우수한 전기화학 성능을 나타냄을 알 수 있다. 따라서, 상기 자가 변환 고체 산화물 전지는 수전해셀로서 적용 가능성이 있음을 알 수 있다.Referring to FIG. 14, a voltage curve according to a current density at a temperature of 800° C. in a water electrolysis mode for hydrogen gas containing _{3% H 2} O and 10% H _{2 O, respectively, is shown.} The electrochemical performance was recorded by scanning the current density in the voltage range from 0 V to 1.5 V. The self-conversion solid oxide battery 800

In the case of 1.3 and at a cell voltage V, 3 vol% H ₂ O is -0.42 A cm ^{- 2,} 10% H ₂ O In case of vol -0.62 A cm ^- shows a current density of ^2. Thus, it can be seen that very small amounts of H ₂ O supplied to the Figure, shows excellent electrochemical performance, such as 3 vol% H ₂ O. Accordingly, it can be seen that the self-conversion solid oxide battery has the potential to be applied as a water-receiving cell.

15 is a graph showing the stability of a self-converting solid oxide battery according to an embodiment of the present invention.

Referring to Figure 15, it shows the stability of the self-conversion solid oxide battery at a temperature of 700 ℃ and ^{a current density of +/-0.2 A cm -2.} In order to analyze the operating reversibility of the self-converting solid oxide battery, a current density of ^{-0.2 A cm -2} at a temperature of 700°C using hydrogen gas containing _{3 vol% H 2} O and 10 vol% H _{2 O, respectively.} The furnace operated as a water electrolysis mode, and also operated as a fuel cell mode with a current density of ^{+0.2 A cm -2, and operated in an alternating cycle manner between these two modes.} In both 3 vol% H ₂ O and 10 vol% H ₂ O, the self-conversion solid oxide cell was analyzed to exhibit stable performance in the water electrolysis mode and the fuel cell mode without causing any special deterioration.

16 is a graph showing long-term stability of a self-converting solid oxide battery according to an embodiment of the present invention.

Referring to FIG. 16A, when _{hydrogen gas containing 10 vol% H 2} O is used, a water electrolysis ^{mode with a current density of -0.2 A cm- 2 and} a current density of +0.2 A cm ^{- 2} Shows the reversible cycle results in the fuel cell mode. The self-conversion solid oxide cell exhibited a uniform voltage for up to 30 hours in the water electrolysis mode and the fuel cell mode, and thus it can be seen that long-term stability is excellent.

Referring to (b) of FIG. 16, after performing a reversible cycle of 6 hours, the result of operating for 100 hours in a fuel cell mode using hydrogen gas containing _{3 vol% H 2 O is shown.} It can be seen that the self-conversion solid oxide battery did not cause any special deterioration, and thus has excellent long-term stability.

As a result of the above, the following conclusion can be drawn for the self-converting solid oxide battery according to the technical idea of the present invention.

First, by applying PBMCO of perovskite structure as an atmosphere adaptive material to the anode and cathode, a self-converting solid oxide battery having the advantages of an asymmetrical configuration and a symmetrical configuration was formed. _{The PBMCO is PrBaMn 1.7} Co _0.3-x O _5+δ + xCo (S-PBMCO) by phase shift and metal elution at the anode, as confirmed by X-ray diffraction results and X-ray photoelectron spectrum analysis. Changed. It was confirmed that the self-conversion solid oxide cell can be operated in a fuel cell mode and a water electrolysis cell mode. In the fuel cell mode, the self-conversion solid oxide cell ^{exhibited a high maximum power density of 1.10 W cm -2} at 800° C. without using a catalyst, and exhibited very stable performance for 100 hours. In the electrolytic cell mode, the self-converting solid oxide battery exhibited an electrochemical performance of -0.62 A cm ^-2 _{for 10 vol% H 2 O at 800° C. and a battery voltage of 1.3 V.} In the reversible cycle experiment, the self-conversion solid oxide battery maintained a uniform voltage at _{10 vol% H 2} O and +/- 0.2 A cm ^{-2 for 30 hours.} From these results, it can be seen that the self-conversion solid oxide cell can provide a promising system as a fuel cell and a water electrolysis cell.

The technical idea of the present invention described above is not limited to the above-described embodiments and the accompanying drawings, and that various substitutions, modifications and changes are possible within the scope not departing from the technical idea of the present invention, the technical idea of the present invention It will be apparent to those of ordinary skill in the art to which this belongs.

100: self-conversion solid oxide cell, 110: anode,
120: cathode, 130: electrolyte, 140: metal eluate,

Claims (15)

Forming a symmetrical electrode structure comprising an anode and a cathode disposed with an electrolyte interposed therebetween, including the same solid oxide, and having the same single perovskite crystal structure in a state doped with cobalt;
Supplying hydrogen-containing gas as fuel to the anode and air to the cathode to operate the symmetrical electrode structure;
During operation of the symmetrical electrode structure, the anode is phase-shifted by self-transformation, thereby having a double-layer perovskite crystal structure in which cobalt is eluted to the surface, and the cathode is a single perovskite in a state doped with the cobalt A method of manufacturing a self-converting solid oxide battery comprising; forming an asymmetric electrode structure by maintaining a crystal structure. delete delete delete delete The method according to claim 1,
In the step of forming the symmetrical electrode structure,
The anode and the cathode having the single perovskite crystal structure include Pr _0.5 Ba _0.5 Mn _0.85 Co _0.15 O _3-δ ,
In the step of forming the asymmetric electrode structure,
The self-conversion is made at a temperature in the range of 600 ℃ to 800 ℃,
The anode is a PrBaMn _1.7 Co _0.3-x O _{5 + δ} phase-transformed, the method of manufacturing a self-conversion solid oxide battery. delete delete delete delete delete The method according to claim 1,
The step of forming the symmetrical electrode structure is performed by simultaneously forming the anode and the cathode by infiltrating a precursor solution into a support, a method of manufacturing a self-converting solid oxide battery. The method of claim 12,
The support has a three-layer configuration of a porous layer/dense layer/porous layer,
One of the porous layers constitutes the anode, the other of the porous layers constitutes the cathode, and the dense layer constitutes the electrolyte. The method according to claim 1,
The electrolyte comprises La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _3-δ , a method of manufacturing a self-conversion solid oxide battery. The method according to claim 1,
The electrolyte is _{a slurry formed by injecting La 0.9} Sr _0.1 Ga _0.8 Mg _0.2 O _3-δ powder into an ethanol solvent containing brown herring fish oil, xylene, polyalkylene glycol, butyl benzyl phthalate, and polyvinyl butyral. A method for producing a self-converting solid oxide battery formed by using.

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