KR101702217B1 - Low-temperature Solid Oxide Fuel Cell - Google Patents

Abstract

The present invention relates to a low temperature type solid oxide fuel cell and a method of manufacturing the same, and more particularly, to a cathode for a solid oxide fuel cell having a core-shell fiber structure, a method for producing the same, A solid oxide fuel cell having excellent output characteristics, and a method of manufacturing the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a low-temperature solid oxide fuel cell,

The present invention relates to a low temperature type solid oxide fuel cell and a method of manufacturing the same.

With the advent of high oil prices, research and demand for new energy has increased, and the importance of fuel cell research has been emphasized. Unlike general heat engines, fuel cells convert the chemical energy of the fuel directly into electric energy, so the energy conversion efficiency is very high. No combustion process is required and NO _x , SO _x , CO ₂ And low-emission environmentally friendly power generation method with little emissions.

Fuel cells are classified into 1, 2, and 3 generations depending on the type of electrolyte. The first generation is a phosphate based fuel cell (PAFC) using phosphate as an electrolyte and the second generation is a Molten Carbonate Fuel (Fuel Cell) using a molten carbonate such as Na, K, Li as an electrolyte. (MCFC), and the third generation is classified as a Solid Oxide Fuel Cell (SOFC) that operates at a higher temperature and achieves high efficiency.

The solid oxide fuel cell of the fuel cell has a higher power generation efficiency than the other cells and operates at a high temperature, so that a noble metal catalyst is not required, and a fuel cell system can be constructed using an inexpensive catalyst (Pd, Ni, Co, etc.). In addition, it does not require a reformer, which is a device for converting natural gas, methanol, etc., which is a fuel, into a hydrogen-rich fuel, and thermal combined power generation using waste heat is possible.

The solid oxide fuel cell is divided into a tubular type and a planar type according to the configuration. Cylindrical SOFC has been evaluated as the closest design to commercialization because it is easy to seal between cells and has high thermal resistance, but it has a lower power density than flat type.

The solid oxide fuel cell is classified into a high-temperature type, a middle-low temperature type, and a low-temperature type according to temperature. The high-temperature type solid oxide fuel cell operates at 800 ° C to 1000 ° C, the low-temperature type at 650 ° C to 800 ° C, and the low temperature type at 400 ° C to 600 ° C. However, since the electrical resistance and the electrode reaction resistance decrease with temperature rise, the power generation efficiency is higher than that of the other two fuel cells because the decrease in the theoretical efficiency due to the temperature rise can be compensated for. However, the high temperature type solid oxide fuel cell [Non-Patent Document 1] suffers from chemical reaction and deterioration phenomenon due to high temperature operation temperature, has a problem of long-term stability and durability, and has difficulty in commercialization due to use of costly exterior material which can withstand high temperature . Accordingly, it has recently been focused on research and development of low-temperature (400 ° C ~ 600 ° C) solid oxide fuel cells with long-term stability and various applications.

The low-temperature type solid oxide fuel cell (Non-Patent Document 2) has a problem that an activation voltage loss occurs due to oxygen ion conduction and surface reaction rate in an electrolyte driven at a low temperature, thereby deteriorating performance.

S. C. Singhal and K. Kendall High-temperature solid oxide fuel cells: fundamentals, design and applications: fundamentals, design and applications (Elsvier, 2003) Wachsman, E. D. et al. Lowering the temperature of solid oxide fuel cells. Science 334, 935-939 (2011)

As a result, the present inventors have found that a functional layer of a nanocomposite material is formed on a cathode of a solid oxide fuel cell, an electrolyte is thinly formed on a cathode by a thin film manufacturing method, and a porous core Temperature type solid oxide fuel cell having high performance at a low temperature by using a shell-fiber structure anode, thereby completing the present invention.

Accordingly, it is an object of the present invention to provide a low-temperature type solid oxide fuel cell having high performance and a method of manufacturing the same.

The present invention provides, as means for solving the above problems,

Core fibers of perovskite type metal oxide and

Including shell nanoparticles of an electrolyte material

And a cathode for a low temperature type solid oxide fuel cell.

In another aspect of the present invention, there is provided a solid oxide fuel cell comprising a cathode, an electrolyte layer and a cathode,

The anode;

An electrolyte layer of no pores; And

Anode functional layer of a nanocomposite material comprising nickel and an electrolyte material

Temperature type solid oxide fuel cell.

The present invention, as another means for solving the above problems,

Forming a core fiber with a perovskite-type metal oxide;

Forming a shell of an electrolyte material on the core fiber;

The present invention also provides a method of manufacturing a positive electrode for a low temperature type solid oxide fuel cell.

The present invention, as another means for solving the above problems,

Forming a negative electrode functional layer of a nanocomposite material comprising nickel and an electrolyte material on a negative electrode support;

Forming an electrolyte layer of inorganic fine particles on the negative electrode functional layer; And

Producing the anode on the electrolyte layer

Type solid oxide fuel cell according to the present invention.

The cathode for a low temperature type solid oxide fuel cell according to the present invention can be formed by using an inorganic material including a ceramic oxide as a precursor by using electrospinning and a Phechni process as well as by shortening the time required for forming the inorganic fiber structure, The porous core shell structure is formed to reduce the activation loss voltage, the resistance due to the charge transfer, and the gas diffusivity, resulting in an increase in the surface oxygenation. In addition, by forming a tight fiber structure at a low temperature, durability and structural stability can be secured, and the life extension effect can be expected.

In addition, the low-temperature type solid oxide fuel cell according to the present invention increases the reactivity by widening the three-phase interface by forming the nanocomposite functional layer on the anode together with the anode, thinning the electrolyte and reducing the activation voltage loss .

1 shows the structure of a solid oxide fuel cell according to the present invention.
2 is a schematic diagram of an electrospinning device used for producing BSCF core fibers in the present invention.
3 is a scanning electron micrograph (SEM) photograph of a BSCF core shell-fiber structure using electrospinning (scale bars: 1 mm and 100 nm).
4 is a color photograph showing the BSCF core shell-fiber structure after the calcination reaction (500 ° C).
5 is a scanning electron micrograph (SEM) image of the BSCF core shell-fiber structure after calcination (500 ° C) [scale bar: 10 mm].
6 is a schematic schematic diagram of the Pecheni method used in the synthesis of the BSCF-GDC core-shell structure.
Figure 7 on page struck by BSCF-GDC composite using the method _{(Ba 0 .5 Sr 0 .5 Co} 0 .8 Fe 0 .2 O 3 -δ Gd 0.1 Ce 0.9 O 1.95) BSCF after reaction calcining (600 ℃) of - Scanning electron microscope (SEM) photograph showing the fiber core structure of the GSC core shell [scale bar: 10 μm].
Figure 8a shows the BSCF-GDC core-shell fiber structure measured by X-ray diffractometer before and after the calcination (600 ° C), b shows the BSCF-GDC core- The shell fiber structure is measured by a thermogravimetric analyzer (TGA) / differential scanning calorimeter (DSC).
9 shows the results of the calcination (500 ° C), BSCF-GDC (b), BSCF-GDC core-shell fiber structure (c) after calcination Scanning electron microscope (SEM) photograph [scale bar: 1 ㎛].
10 is a transmission electron microscope (TEM) photograph showing the morphology of BSCF-GDC core-shell fibers [scale bar: 1 μm].
11 shows a GDC shell particle formed on a BSCF core fiber, which is a photograph of Box 1 of FIG. 10 observed with a high-resolution transmission electron microscope (HRTEM) [scale bar: 10 nm].
Fig. 12 shows an arbitrary arrangement of the GDC lattice structure, which is a photograph of the box 2 of Fig. 11 observed with a high-resolution transmission electron microscope (HRTEM) [scale bar: 5 nm].
13 shows an electron diffraction pattern of a GDC lattice structure of core-shell fibers.
14A is a graph comparing the area specific resistivity (ASR) values of the existing BSCF-GDC and the core-shell fiber structure BSCF-GDC with temperature,
FIG. 14B compares the existing BSCF-GDC and the core-shell fiber structure BSCF-GDC with an impedance spectrum at an electrode thickness of 10 μm and 550 ° C. FIG.
15 is a photograph of a conventional BSCF-GDC electrode observed with a scanning electron microscope (SEM) at a resolution of 100 nm and 1 탆.
16 is a photograph of a BSCF-GDC electrode having a core-shell fiber structure observed with a scanning electron microscope (SEM) at a resolution of 100 nm and 1 탆.
17 compares the electron mobility diagrams of the existing BSCF-GDC and the BSCF-GDC of the core-shell fiber structure.
FIG. 18 is a graph showing the relationship between a first-generation cell (a) and a BSCF-GDC (.about.30 占 퐉) | GDC (.about.5 占 퐉) of BSCF-GDC (.about.24 占 퐉) | GDC (B) of Ni-GDC nanocomposite material (~ 10 탆) (cathode function layer; AFL) and Ni-GDC (~ 800 탆).
19 is a photograph (a) comparing the voltage and power densities of the first-generation battery and the second-generation battery of FIG. 18, and FIG. 19 (b) comparing the impedance spectrum at 550 ° C.
FIG. 20 is a graph showing a relationship between a voltage of a battery (BSCF-GDC (~ 30 占 퐉), GDC (~ 5 占 퐉), Ni-GDC nanocomposite material (~ 10 占 퐉) [A: OCVs and maximum power densities, b: resistance and electrode ASR].
FIG. 21 is a graph showing the relationship between the voltage of the battery (BSCF-GDC (~ 30 占 퐉), GDC (~ 5 占 퐉), Ni-GDC nanocomposite material (~ 10 占 퐉) ㎛)] was run five times to observe durability and stability at repeated operation at 550 ° C and the resulting current density-voltage.
FIG. 22 is a graph showing a relationship between a voltage of a battery (BSCF-GDC (~ 30 占 퐉) | GDC (~ 5 占 퐉) | Ni-GDC nanocomposite material Mu] m) was operated five times in order to see durability and stability at repeated operation at 550 DEG C, and the resulting impedance spectrum was shown.
FIG. 23 is a graph showing the results of a comparison between the battery of the present invention (BSCF-GDC (~ 30 占 퐉) | GDC (~ 5 占 퐉) | Ni-GDC nanocomposite material (~ 10 占 퐉) )] Is operated five times in order to see durability and stability at repeated operation at 550 ° C, and the time-dependent voltage is shown.

The present invention relates to a cathode for a low temperature type solid oxide fuel cell comprising core fibers of a perovskite-type metal oxide and shell nanoparticles of an electrolyte material.

The perovskite-type metal oxide forms the core fibers of the anode of the solid oxide fuel cell, and the electrolyte material is surrounded by the core fibers in the form of particles to form a shell structure.

Since the perovskite-type metal oxide is excellent in redox stability and has both ionic conductivity and electron conductivity as mixed inonic and electronic conductor (MIEC), it has excellent electrode activity at a low temperature, And may contribute to decrease polarization resistance and ion and electron transfer resistance.

According to one embodiment, the perovskite-type metal oxide may be represented by, for example, the following formula (1).

[Chemical Formula 1]

ABO _{3- 隆}

In Formula 1, A is at least one element selected from a lanthanide element, a rare earth element and an alkaline earth metal element,

B is at least one element selected from transition metal elements,

is a value which makes the compound of formula (1) electrically neutral.

According to one embodiment, the perovskite-type metal oxide of Formula 1 may have a composition represented by Formula 2 below.

(2)

_{A '1- x A "x B} ' 1 - y B" y O 3 -δ

In Formula 2, A 'is at least one element of La and Ba,

A "is at least one element selected from Sr, Ca, Sm and Gd,

B 'and B' are different elements and each independently at least one element selected from Cr, Mn, Fe, Co, Ni, Cu, Ti, V, Nb,

0? A <1, 0? B <1,

[delta] is a value that makes the compound of Formula 2 electrically neutral.

These perovskite-type metal oxides may be used singly or in combination of two or more. According to one embodiment, the perovskite-type metal oxide is selected from the group consisting of lanthanum strontium chromium manganese oxide (LSCM), lanthanum strontium chromium vanadium oxide (LSCV), lanthanum strontium chromium ruthenium oxide, lanthanum strontium chromium nickel oxide, lanthanum strontium chromium titanium oxide, Lanthanum strontium cobalt iron oxide (BSCF), barium strontium cobalt titanium oxide (BSCT), and barium strontium zinc cobalt oxide (LSCF), lanthanum strontium titanium cerium oxide, lanthanum strontium titanium cerium oxide, lanthanum calcium chromium titanium oxide, lanthanum strontium gallium manganese oxide, (BSZF). &Lt; / RTI &gt; For example, La _{0 .75} Sr _{0 .25} Cr _{0 .5} Mn _{0 .5} O ₃ La _0.8 Sr _0.2 Cr _0.97 V _0.03 O ₃ , La _{0 .7} Sr _{0 .3} Cr _{0 .95} Ru _{0 .5} O ₃ , La _{1 - x} Sr _x Cr _{1 - y} Ni _y O ₃ , La _{0 .8} Sr _{0 .2} Cr _{0 .8} Mn _{0 .2} O ₃ , La _0.75 Sr _0.25 Cr _0.5 Mn _0.5 O ₃ , La _{0 . 6} Sr _{0 .4} Fe _{0 .8} Co _{0 .2} O ₃ , La _{1 - x} Ca _x Cr _{0 .5} Ti _{0 .5} O ₃ (x = 0 to 1), La _0.7 Sr _0.3 Cr _0.8 Ti _0.2 O ₃ , (La, Sr) (Ti, Ce) O ₃ , La _{0 .9} Sr _{0 .1} Ga _{0 .8} Mn _{0 .2} O ₃ , La ₄ Sr ₈ Ti ₁₁ Mn _{0 .5} Ga _{0 .5} O _{37 . 5, (Ba 0.5 Sr 0.5)} 1-x Sm x Co 0.8 Fe 0.2 O 3-δ (BSSCF; x = 0.05-0.15), Ba 0 .6 Sr 0 .4 Co 1 - y Ti y O 3 -δ ( BSCT), Ba0.5Sr0.5Zn0.2Fe0.8O3-delta (BSZF), or the like may be used.

The electrolyte material is a yttria stabilized zirconia dolly (YSZ), scandia stabilized zirconia (ScSZ), Oh-doped ceria (GDC), Samaritan doped ceria doped barium zirconate (BaZrO _3), and barium three rates (BaCeO ₃₎ But is not limited thereto.

In the anode for the solid oxide fuel cell, the content of the electrolyte material and the perovskite-type metal oxide may be determined in consideration of effects such as resistance and power density. For example, the content of the electrolyte material may be 20 to 40 wt% And the content of the perovskite-type metal oxide may be 60 to 80% by weight. According to one embodiment, the content of the electrolyte material may be 25 to 35% by weight, and the content of the perovskite-type metal oxide may be 62 to 75% by weight.

The anode for a solid oxide fuel cell according to the present invention may be a complexed electrolyte material on the perovskite type metal oxide core fiber in the form of shell nanoparticles in order to increase the surface reaction and the ion transfer rate. FIG. 17 shows the transfer mode diagram of electrons and oxygen ions when the cathode material for the solid oxide fuel cell is applied to a solid oxide fuel cell. As shown in FIG. 17, in the cathode structure produced by the solid-phase reaction method generally used in the production of the anode structure, the conductivity of the electron is not smooth because of low connectivity between the electrolyte material and the perovskite-type metal oxide, It is possible to cause a decrease in the surface reaction due to the decrease in the transfer speed of the catalyst. On the other hand, in the anode where the electrolyte material is distributed in the form of shell nanoparticles on the perovskite-type metal oxide core fiber manufactured by the AE & P method, the electron transfer rate by the fiber structure is significantly improved, Ion transfer rate and surface reaction rate can be improved.

The core fibers have an average diameter of 100 nm to 200 nm irregularly aggregated to form particles having a size of 500 nm to 800 nm. The shell nanoparticles are particles having an average diameter of 100 to 200 nm The particles are surrounded to form a shell structure. The core-shell fiber structure may have an average diameter of 800 to 1500 nm.

The cathode material for a low temperature type solid oxide fuel cell according to the present invention forms a porous core shell structure tightly connected to a net structure, thereby reducing an activation loss voltage, a resistance due to charge transfer, a gas diffusion degree, and an increase in surface oxygenation. In addition, by forming a tight fiber structure at a low temperature, durability and structural stability can be secured, and the life extension effect can be expected.

The present invention also relates to

Forming a core fiber with a perovskite-type metal oxide;

Forming a shell of an electrolyte material on the core fiber;

And more particularly, to a method of manufacturing a positive electrode for a low temperature type solid oxide fuel cell.

Specifically, a slurry composition comprising a perovskite-type metal oxide, a resin, and an organic solvent is electrospun and calcined to form a core of the fiber structure. At this time, the slurry composition is prepared so as to have a viscosity of 80 to 150 cP at 20 캜.

The calcination is heat treated at 500 to 600 DEG C for 4 to 8 hours.

A metal precursor constituting an electrolyte material, a polymer for uniformity of particles and a metal salt including an organic solvent are added to the core fiber, followed by stirring and heat treatment to form a core-shell structure. Thereafter, a cathode paste is produced through a calcination reaction.

The present invention also includes a solid oxide fuel cell comprising the anode.

In one embodiment of the present invention, the anode; An inorganic electrolyte layer; An anode functional layer of a nanocomposite material comprising nickel and an electrolyte material; And a low temperature type solid oxide fuel cell including a cathode.

1 is a schematic view showing a structure of a solid oxide fuel cell according to one embodiment.

Hereinafter, each component of the solid oxide fuel cell according to the present invention will be described in detail.

Cathode support

The cathode acts as electrochemical oxidation and charge transfer of the fuel. The negative electrode may include nickel and an electrolyte material. Since the electrolyte material is as described above, a detailed description thereof will be omitted.

The thickness of the negative electrode may be 1 to 1000 mu m, 10 to 950 mu m, or 100 to 900 mu m. Since the anode support reacts with the fuel at the three phase boundary, the mesoporous structure must have a wide three-phase interface and oxygen ion conductivity and electron conductivity should be high during the reaction. When the temperature changes, the physical properties should not be affected by temperature and should not be easily cracked. In addition, since the pressure of the gas is received from both sides of the support, the support must have a strength capable of withstanding the pressure.

cathode Functional layer

The anode functional layer plays an important role in expanding the three phase interface occupying the reaction area of most of the fuel cells of the present invention. The three-phase interface is the region where the reaction occurs most actively between the cathode and the electrolyte. Therefore, in order to further expand the three-phase interface, a function layer is coated between the cathode and the electrolyte to widen the reaction area between the cathode and the electrolyte.

In the present invention, the negative electrode functional layer includes nickel and an electrolyte material in the same manner as the preceding negative electrode support, but has a composition different from that of the negative electrode support in accordance with the characteristics of the functional layer.

Unlike the negative electrode support, the negative electrode functional layer has the main purpose of improving the mechanical properties of the negative electrode, which can change the mechanical properties of the negative electrode functional layer depending on the particle size characteristics of the ion conductive oxide.

In the present invention, it is preferable to use a nanocomposite material containing nickel and an electrolyte material.

Since the electrolyte material is as described above, a detailed description thereof will be omitted.

The nanocomposite refers to a form in which Ni nanoparticles are wrapped around an electrolyte material particle.

In the present invention, the raw material composition of the anode functional layer has a weight ratio of nickel and electrolyte material of 55 to 75: 25 to 45. If the amount of Ni is too small, the electrochemical role of oxidizing the fuel is reduced to cause a resistance at the interface between the cathode and the electrolyte. If too much Ni is present, it is difficult to transfer the oxidized hydrogen ions to the electrolyte, .

The thickness of the negative electrode functional layer increases as the thickness of the negative electrode increases, which may act as a factor of deterioration in performance during ion transport, and therefore, it is preferably 5 to 15 μm.

Electrolyte layer

The electrolyte layer should be dense so that air and fuel do not mix, high oxygen ion conductivity and low electronic conductivity. In addition, since the anode and the cathode having a great difference in oxygen partial pressure exist on both sides of the electrolyte layer, it is necessary to maintain the above properties in a wide range of oxygen partial pressure.

In the case of the electrolyte layer, the same electrolyte material as the electrolyte material used for the negative electrode is generally used as the electrolyte material.

The material for the electrolyte layer is not particularly limited as long as it can be generally used in the related art and includes at least one selected from zirconia-based, ceria-based, bismuth oxide-based and lanthanum gallate-based solid electrolytes . For example, the electrolyte may be a zirconia-based, doped or undoped with at least one of yttrium, scandium, calcium, and magnesium; Ceria system doped or undoped with at least one of gadolinium, samarium, lanthanum, ytterbium, and neodymium; Bismuth oxide system doped or undoped with at least one of calcium, strontium, barium, gadolinium and yttrium; And a lanthanum gallate system doped with or not doped with at least one of strontium and magnesium. Specific examples of such electrolytes include yttria stabilized zirconia (YSZ), scandia stabilized zirconia (ScSZ), samaria doped ceria (SDC), gadolinia doped ceria (GDC) and the like.

Since the composition of the electrolyte is not a complex, the difficulty in selecting the composition is relatively less. However, it is important to form a thin electrolyte layer because it improves the oxygen ion transfer rate and improves the performance. Therefore, in the present invention, it is possible to form an electrolyte layer of a thin film having a thickness of 4 to 10 mu m by a dip-coating method.

Further, the electrolyte layer must be formed without pores to prevent permeation of oxygen and hydrogen supplied to the positive electrode and the negative electrode, respectively.

anode

The anode (air electrode) reduces the oxygen gas to oxygen ions and keeps the air flowing to the anode to maintain a constant oxygen partial pressure. As the material of the anode, for example, metal oxide particles having a perovskite type crystal structure can be used, as described above.

The thickness of the anode may be generally from 1 to 100 mu m.

The solid oxide fuel cell of the present invention comprising the above components satisfies the following general formula 1:

[Formula 1]

X? 1.5

And X represents the output (W / cm ² ) at a temperature of 550 ° C.

Therefore, the solid oxide fuel cell according to the present invention is operable at a low temperature of 400 to 600 ° C.

The present invention also provides a method of forming a negative electrode, comprising: forming a negative electrode functional layer of a nanocomposite material comprising nickel and an electrolyte material on a negative electrode support;

Forming an inorganic porous electrolyte layer on the negative electrode functional layer; And

Preparing a cathode comprising a core fiber of perovskite-type metal oxide and shell nanoparticles of an electrolyte material on the central portion of the electrolyte layer

And a method for producing the solid oxide fuel cell.

A method of manufacturing a low-temperature type solid oxide fuel cell according to the present invention includes:

Fabricating a negative electrode support comprising nickel and an electrolyte material;

Coating and heat-treating a slurry containing nickel and an electrolyte material on the anode support to form a negative electrode functional layer;

Forming an electrolyte layer by dip coating a slurry containing an electrolyte material on the negative electrode functional layer; And

And forming a cathode comprising a core fiber of a perovskite-type metal oxide and shell nanoparticles of an electrolyte material on a central portion of the electrolyte layer.

First, a pore-forming agent is added to a nickel oxide and an electrolyte material powder to prepare a slurry, which is then powdered, and a binder and distilled water are added to the powder to prepare a cathode paste. At this time, the nickel oxide, the electrolyte material and the pore-forming agent are mixed in a weight ratio of 60 to 45: 45 to 30: 5 to 20. Activated carbon, carbon black, starch, PMMA and the like may be used as the pore former.

The negative electrode paste is formed through an extrusion process, and is then calcined at 1100 to 1300 ° C to produce a negative electrode support.

Nickel oxide and an electrolyte material powder are formed on the anode support by a Pechini sol-gel method. For example, the nickel oxide and the electrolyte material powder are calcined at 400 to 800 ° C., The functional layer slurry to which a dispersant, an organic solvent, a plasticizer, a binder and a surfactant are added is ball-milled to form a negative electrode functional layer.

The electrolyte material powder is formed into an electrolyte slurry on the negative electrode functional layer and coated by a dip coating method. The electrolyte slurry may be prepared by mixing together additives such as a dispersant, an organic solvent, a plasticizer, a binder, and a surfactant.

The slurry having a viscosity of 2.0 to 3.5 cP at 25 캜 is preferred for reasons of thin and uniform coating. The thickness of the electrolyte layer can be adjusted according to the viscosity.

A core slurry containing a perovskite-type metal oxide powder, a resin, and an organic solvent is formed on a central portion of the electrolyte layer to prepare a core fiber by electrospinning.

A shell is formed on the core fiber by an electrolyte material particle by a Peltier method.

A metal precursor constituting an electrolyte material, a polymer and a metal salt including an organic solvent are added to the core fiber, followed by stirring and heat treatment to form a core-shell structure. Thereafter, a cathode paste is produced through a calcination reaction.

The positive electrode paste is applied to the negative electrode coated with the electrolyte through screen printing to produce a solid oxide fuel cell.

[ Example ]

Hereinafter, the present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited by the following examples.

Manufacturing example  1: Core-shell structure cathode manufacturing

1) Core fiber manufacturing

0.7 g of BSCF powder, 0.7 g of poly-vinyl-pyrrolidine (PVP) and 7 g of ethanol was prepared. The viscosity of the core slurry is about 100 cP at 20 캜. A core slurry was prepared in a syringe having a nozzle having an inner diameter of 0.15 mm. Fig. 2 is a schematic diagram of an electrospinning device used for BSCF core fiber fabrication. Electrospinning was performed at a rate of 15 [mu] L / min at a voltage of 15 kV. The temperature was maintained at 20 ° C and the humidity was about 30-35%. 3 is a scanning electron micrograph (SEM) photograph of a BSCF core shell-fiber structure using electrospinning, wherein the electrospun core fiber was calcined at 500 ° C for about 5 hours in an oxygen atmosphere. These perovskite type metal oxide core fibers were prepared.

2) Shell manufacture

Cerium nitride and gadolinium nitride were dissolved in 100 mL of distilled water to a molar ratio of 9: 1, and the mixture was stirred at 70 DEG C for about 1 hour. Citric acid and metal were mixed at a molar ratio of 1: 1, and ethylene glycol and citric acid were mixed at a molar ratio of 4: 1. Then, calcined BSCF core fibers and oxide (GDC) were mixed at a mass ratio of 7: 3. The mixture was stirred at about 70 DEG C for about 1 hour and then kept at 200 DEG C for about 3 hours. The powder having the core-shell structure was obtained after calcination at 600 DEG C for about 3 hours (Figs. 6, 7, 9).

In the yellow line of FIG. 4, the reduced electrode core fibers made by sol-gel electrospinning showed weak shrinkage during the calcination at 500 ° C, and the fiber structure was maintained as shown in the SEM image of FIG. 5. 6, the BSCF-GDC core / shell fiber calcined at 600 ° C as in the SEM image of FIG. 7 shows the fiber structure even when the BSCF core fibers were packed with GDC nanoparticles using the Perkini synthesis method accompanied by the active agitation and combustion reaction Respectively. The formation of BSCF-GDC core / shell fibers through the AE & P process is accomplished by the following process: (1) GDC of cubic fluorite forms core / shell fiber structure formed at calcination at 600 ° C but not calcined The BSCF has only a perverse structure as shown in FIG. 8A. (2) The mass loss difference between BSCF core fibers (10%) and BSCF-GDC core / shell fibers (20%) is mainly due to the amount of polymer in the GDC shell particles.

FIG. 9A is an SEM image of BSCF core fibers. BSCF particles having a diameter of about 500 to 800 nm and a size of 100 to 200 nm have a fiber structure. In the process of attaching the GDC grains to the BSCF core fibers, it increased to about 1.2 to 1.5 μm due to the surrounding of the BSCF core fibers with gadolinium and cerium nanoparticles mixed with the polymer material as shown in the SEM image of FIG. 9b. This indicates that the pores between the BSCF particles of the core fibers are filled by the polymer nanoparticles and the polymer fibers are surrounded by the polymer nanoparticles. 9C shows a fiber structure obtained by applying a GDC metal oxide to a BSCF core fiber and calcining at 600 ° C. After removal of the polymers, the fiber structure is again formed on the BSCF core fiber surface by small pores and the thickness of the fibers is also reduced. Using the energy dispersive x-ray spectroscopy (EDX), the GDC nanoparticles were precisely identified as pores and shapes that closely packed the BSCF core fibers, and the compositions of gadolinium and cerium were confirmed. When synthetic materials _{Ba 0 .5 Co 0 .8 Fe 0} .2 O 3 -δ and Gd _{0 .1} Ce _{0 .9} O Chemicals amount of _{1 .95} stoichiometric ratio can also be confirmed that the fit. Figs. 10-13 show electron transmission microscopy (TEM) and HRTEM images of BSCF-GDC core / shell fibers after calcination at 600 &lt; 0 &gt; C. The BSCF-GDC core / shell fiber of Figure 10 shows a diameter of 1 μm similar to the size found in the SEM photographs. Fig. 11 is a HRTEM photograph showing bright nanoparticles attached to core fibers of a dark part in Fig. 10; Fig. FIG. 12 is an enlarged photograph of FIG. 11, and FIG. 13 shows an electron diffraction image obtained in the region of FIG. The bright nanoparticles exhibit a d-spacing value of approximately 2.6 A. The Debye-Scherrer rings of electron diffraction patterns and bright nanoparticles are consistently considered cubic fluorite GDCs, which allows bright GDC nanoparticles to be fabricated through simple AE & P processes without structural collapse of BSCF core fibers and core / shell fiber structures . The symmetry cell experiments are conducted by the BSCF-GDC electrodes of the general BSCF-GDC and the core / shell fiber structure. Both electrode thicknesses are approximately 10 μm. FIG. 14A shows that the area specific resistances of the reducing electrode of the BSCF-GDC reduction electrode of the core / shell fiber structure and the activation energy of the general BSCF-GDC reduction electrode are shown in FIG. The values were ~ 105 kJ mol ^-1 and ~ 114 kJ ㆍ mol ^-1 , respectively, which were similar to the oxygen exchange values (113 ± 11 kJ · mol ^-1 ). This indicates that the oxygen surface exchange reaction of the electrode acts as a rate determining step at low temperature. The reduction electrode ASR was measured through the impedance, at high frequencies the electrolyte resistance was shown, and the arc length was the reduction electrode resistance. 14B, the ASR value of the BSCF-GDC reduction electrode of the core / shell fiber structure at 550 ° C is 0.5520? Cm ^{2, which} is significantly lower than 1.1150? Cm ² of the typical BSCF-GDC reduction electrode. The ASR of the two reducing electrodes increased rapidly at 500 ℃. This is related to the BSCF material, but the structure has improved these properties in the present invention. Typical BSCF-GDC electrode to decrease from 550 ℃ to 500 ℃ ASR value of 1.115 Ω and increase in cm ² to 3.361 Ω and cm ^2, and when reduced at 500 ℃ to 450 ℃ 1200O Ω at 3.361 Ω and cm ² and cm &lt; ² &gt; On the other hand, when the ASR value of the BSCF-GDC core / shell fiber electrode decreases from 550 ° C to 500 ° C, the ASR value increases from 0.552 to 1.284 Ω · cm ² and decreases from 500 ° C to 450 ° C at 1.284 Ω · cm ² And increased to 4.717? Cm ² . The ASR of the two electrodes of the same thickness shows a large difference in the ASR value even though the ASR value decreases without the change of the activation energy if the surface area increases as the reduction electrode thickness increases. It is seen that the surface area is greatly increased. In addition, an oxygen surface reaction occurs at the electrode at low frequencies, indicating that the low ASR core / shell fiber electrode performs more active oxygen exchange. This can be attributed to the high specific area and morphological characteristics of the BSCF-GDC core / shell fiber structure. FIGS. 15 and 16 show SEM photographs of the structure of the electrode made of general BSCF-GDC particles and the core / shell fiber electrode. 15, 16 can be found to exhibit a high specific surface area of 1.697 m ² g ^-1 and in BSCF GDC-core / shell fiber than the 0.667 m ² g ^-1 and a non-area (SBET) of general BSCF-GDC particles . Typical BSCF-GDC particles are 100-200 nm in size and irregularly and rarely have a size of 500-800 nm attached to large BSCF particles. In addition, the GDC particles should be attached to the BSCF particles as an oxygen ion transfer material, but they also tend to aggregate GDCs. This agglomeration has a negative effect on the electrical properties of the reducing electrode of the BSCF-GDC electrode. The BSCF-GDC core / shell fiber structure maintains the fiber shape and the GDC shell particles have a size of 100 nm. These shells are constantly attached to form a BSCF-GDC core / shell fiber structure of approximately 1 μm thickness. GDC shell nanoparticles are closely attached to BSCF and show high oxygen ion transmission tendency. It also helps improve the oxygen ion transfer capability between the GDC electrolyte and the reducing electrode. The structure of this structure is shown in the SEM image and the schematic oxygen ion transfer ability is shown in FIG.

Example  1: Low-temperature solid oxide fuel cell manufacturing

FIG. 1 shows a schematic configuration of the low temperature type solid oxide fuel cell.

1) Manufacture of cathode powder

The powder of NiO and Gadolodo doping ceria (GDC) and carbon black were mixed in a weight ratio of 54.5: 36.4: 9.1. The ball milling process with zirconia balls was carried out in 150 ml of ethanol a day. The powder was dried in a 60 ° C oven for one day.

2) Cathode support production

The dried cathode powder was molded at a pressure of 88 MPa by taking 4 g into a mold having a diameter of 36 mm. The disk-shaped NiO-GDC support was calcined at 1100 ° C for about 3 hours to prepare a negative electrode support. The thickness of the support is about 800 μm.

3) Manufacture of cathode functional layer powder

Nickel oxide and an electrolyte material powder were prepared by using a Pechini sol-gel method. Powders of NiO and Gadolodo-doping ceria (GDC) were mixed at a weight ratio of 60:40 Functional layer powder was prepared.

(NO ₃ ) ₃ .6H ₂ O, Ce (NO ₃ ) ₃ .6H ₂ O, Ni (NO ₃ ) ₂揃 6H (NO ₃ ) ₃ .6H ₂ O, and the like were mixed so that the weight ratio of NiO and Gadolodo- ₂ O in distilled water at a molar ratio of 1.7: 15.4: 82.9 and stirred at room temperature for 3 hours. The stirred salt was mixed with citric acid at a molar ratio of 1: 1 and ethylene glycol at a molar ratio of 1: 4, and the core particles were also put into the solution and stirred at 70 캜 until a polymer gel was formed. Particles were burned at 200 ° C to obtain a functional layer powder. Thereafter, a functional layer powder having crystallinity was prepared by calcination at 600 ° C for about 3 hours.

4) Negative electrode functional layer production

10 g of cathode functional layer powder, 100 ml of a toluene / isopropyl alcohol mixture, 1 ml of a plasticizer, 1 g of a binder and 0.2 ml of a surfactant were added and the mixture was ball-milled for one day to prepare a functional layer slurry. The plasticizer is di-butyl phthalate, the binder is poly-vinyl-butyral, and the surfactant is EFKA-4340. The fuel electrode functional layer slurry was coated on the plated anode support by dip coating method and plasticized at 1100 ° C for about 3 hours. The functional layer showed a thickness of 10 μm.

5) Formation of electrolyte layer

15 g of GDC powder, 150 ml of toluene / isopropyl alcohol mixture, 1.5 ml of plasticizer, 1.5 g of binder and 0.3 ml of surfactant were added and the mixture was ball-milled for one day to prepare a functional layer slurry. The plasticizer is di-butyl phthalate, the binder is poly-vinyl-butyral, and the surfactant is EFKA-4340. The viscosity of the slurry was 2.5 cP at 25 캜. The anode support coated with anode functional layer was coated three times by dip-coating method and sintered at 1500 ° C for about 3 hours. The electrolyte layer has a thickness of 5 μm to 10 μm.

6) Fabrication of core-shell structure anode

The positive electrode prepared in the core-shell structure in Preparation Example 1 was formed into a paste, coated on a support coated with an electrolyte by screen printing, and calcined at 950 ° C for about 2 hours. The thickness of the anode is approximately 30 μm.

Experimental Example  One

The crystal structure of the BSCF-GDC core-shell fiber was measured using an X-ray diffractometer (Rigaku, Miniflex model) at room temperature using Cu Ka radiation. Mass reduction and heat flow of BSCF-GDC core-shell fibers and BSCF core fibers were measured by thermogravimetric analysis and differential scanning calorimetry (Mettler Toledo, 1100 SF) before calcination at temperatures between 100 and 1000 ° C in an air atmosphere Respectively.

8a shows the BSCF-GDC core-shell fiber structure measured by an X-ray diffractometer (XRD) before and after the calcination reaction (600 ° C) by attaching GDC to the BSCF fiber via the AE & P method. As a result, it can be confirmed that a fluorocyte GDC is formed in the perovskite BSCF after calcination. b shows the BSCF-GDC core-shell fiber structure measured with a thermogravimetric analyzer (TGA) / differential scanning calorimeter (DSC) before the calcination reaction (600 ° C) by attaching GDC to the BSCF fiber via the AE & P method. The mass reduction shown here is due to the polymer contained in the GDC shell particles.

Experimental Example  2

Components and components of GDC-based LT-SOFC and BSCF-GDC core-shell fibers using field emission scanning electron microscopy (FE-SEM, JEOL, JSM-7001F model) with energy dispersive x-ray spectroscopy Respectively.

Field emission transmission electron microscopy (FE-TEM or HRTEM; JEOL, JEM 2100-F model) is used to distinguish nanoparticles of GDC shells from BSCF core fibers. FIG. 10 is a transmission electron microscope (TEM) photograph showing the morphological characteristics of the BSCF-GDC core-shell fiber. The diameter of the BSCF of the fiber core-shell structure is 1 μm. 11 shows a GDC shell particle formed on a BSCF core fiber, which is a photograph of a box 1 of FIG. 10 observed by a high-resolution transmission electron microscope (HRTEM). Here, bright nanoparticles are clearly attached to the cores of dark fiber structure. FIG. 12 shows an arbitrary arrangement of the GDC lattice structure. FIG. 12 is a photograph of the box 2 of FIG. 11 observed by a high-resolution transmission electron microscope (HRTEM). It can be seen that the d-spacing values of bright nanoparticles are approximately 2.6 A. 13 shows an electron diffraction pattern of a GDC lattice structure of core-shell fibers. The Debye-Scherrer circles of bright nanoparticles represent the GDC of the fluorite structure, indicating that the GDC is attached to the BSCF fiber via the AE & P method.

Experimental Example  3

In the preparation of the symmetrical cell, the GDC electrolyte powder was prepared as a disc-shaped support as in the case of forming the anode support in Example 1 above. A general anode paste and a core-shell fiber structure anode paste made on an electrolyte support sintered at 1550 ° C for about 5 hours were coated on both sides by screen printing, respectively. The symmetrical cells sintered at 950 ° C for about 2 hours were measured by impedance analyzer at 650 ° C to 450 ° C at 50 ° C intervals in the range of 0.1 to 1 MHz with an amplitude of 10 mV in an air atmosphere. 14A is a graph comparing the area specific resistivity (ASR) values of the existing BSCF-GDC and the core-shell fiber structure BSCF-GDC with temperature. The area specific resistivity was measured between 450 ° C and 600 ° C, and the activation energy was calculated and compared. In the case of conventional BSCF-GDC, the activation energy of 114 kJ · mol ^-1 is shown, which is similar to the activation energy of surface oxygenation. In contrast, the core-shell fiber structure BSCF-GDC exhibits an activation energy of 105 kJ · mol ^-1 . FIG. 14B compares the existing BSCF-GDC and the core-shell fiber structure BSCF-GDC with an impedance spectrum at an electrode thickness of 10 μm and 550 ° C. FIG. 0.552 Ω · cm ² for core-shell fiber structure BSCF-GDC at 550 ° C and 1.115 Ω · cm ² for conventional BSCF-GDC.

Experimental Example  4: Check battery performance

The unit cell performance was measured with the performance evaluation equipment at 50 ° C intervals from 550 ° C to 450 ° C while supplying the unit cell (FIG. 1) prepared in Example 1 with 80 sccm of hydrogen at the anode and 300 sccm of air at the cathode. FIG. 19 (a) is a graph comparing the voltage and power density of the first-generation battery and the second-generation battery of FIG. 18, and FIG. 20 (a) is a graph illustrating performance of the battery according to the present invention. Impedance was measured in the range of 0.1 to 1 MHz with an amplitude of 10 mV. FIG. 19 is a photograph showing the impedance spectrum of the first-generation battery and the second-generation battery of FIG. 18 at 550 ° C. FIG.

The first generation cell represents the core / shell fiber BSCF-GDC (~ 24 μm) | GDC (~9 μm) | Ni-GDC (800 μm) fuel cell -GDC (~ 30 μm) | GDC (~ 5 μm) | Nano-component Ni-GDC AFL (~ 10 μm) | Ni-GDC (~ 800 μm) fuel cell (FIG. 18b). As shown in FIG. 19A, the open-circuit voltages of the first-generation battery and the second-generation battery are 0.908 and 0.923 V, respectively, which are similar to those of the GDC-based battery. Ni-SDC &lt; / RTI & gt ^; exhibiting a maximum power of approximately 0.65 to 0.7 W-cm & lt ^; SDC (20 μm) | BSCF battery and Ni-GDC exhibiting maximum power of 0.86 W · cm ^-2 | GDC (10 μm) | Unlike the sol-gel-derived BSCF, it shows high power of 1.14 W · cm ^-2 and 1.97 W · cm ^{-2 in} the first- and second-generation cells, respectively. The first-generation cell is approximately 9 탆 thick electrolyte and exhibits a thickness similar to that of the cell, which exhibits a power of 0.86 W cm cm ^-2 . Nonetheless, the improvement in performance is due to the structural inventions of the reducing electrode. In addition, a secondary battery having a performance of about 2 W · cm ^-2 at 550 ° C. is of great value as it has not yet been achieved by the production of LT-SOFCs at low cost. The difference in power density between the primary battery and the secondary battery can be illustrated in FIG. 19B. First, by reducing the thickness of the electrolyte from 9 μm to 5 μm, it can be seen that the ASR _ohmic value of the secondary battery is remarkably reduced from 0.11 to 0.05 Ω · cm ² . Unlike previous studies which reported that the minimum thickness of the impermeable electrolyte membrane of the battery made by the low-cost process is 10-15 [mu] m, the present invention succeeded in mass production of the battery having the electrolyte of 5 [ . The helium gas permeability of the cell was found to be sufficient to be usable as an SOFC electrolyte at a concentration of 2.06 · 10 ^-9 mol · m ^-2 · s ^-1 · Pa ^-1 at 0.25 Mpa. In addition, reduced the nano-component cathode functional layer and the electrode of the invention reduced 2G cell electrode area specific resistance of from 550 ℃ (ASR _electrode) value, as shown in Figure 18b at 0.059 to 0.043 and Ω cm ^2. By AFL, the oxidized electrode and the electrolyte are closely connected to each other to improve the electrical performance and reduce the material transfer resistance of the oxidized electrode. Further, by controlling the thickness of the negative electrode functional layer, the increase in ohmic resistance due to the shrinking effect can be prevented. In the present invention, the shrinkage effect can be most effectively reduced when the thickness of the AFL is 10 μm.

Experimental Example  5: Reproducibility measurement

In the reproducibility measurement, the number of times was measured by the method 2 in the experiment based on the unit cell obtained in Example 1 above. In the durability measurement, the gas flow rate was 60 sccm of hydrogen and 300 sccm of air, respectively. FIG. 21 shows the current density-voltage according to the present invention when the battery was operated five times to observe durability and stability at repeated operation at 550 ° C. 22 shows the impedance spectrum of the battery according to the present invention operated five times in order to observe durability and stability at repeated operation at 550 ° C. FIG. 23 shows the voltage of the battery of the present invention operated five times in order to see durability and stability when the battery is repeatedly operated at 550.degree.

20 to 22 show experimental results for confirming the reproducibility of GDC-based LT-SOFCs. 20A, the maximum power densities were 1.705 0.405 W-cm ^-2 , 1.562 0.405 W-cm ^-2 , 1.192 0.391 W-cm ^-2 , 0.655 0.185 W-cm ^-2 . In FIG. 20B, the ASRs _ohmic was approximately 0.046 ± 0.01 Ω · cm ² , 0.060 ± 0.006 Ω · cm ² , 0.079 ± 0.008 Ω · cm ² , and 0.118 ± 0.008 Ω · cm ² at 600 ° C, 550 ° C, 500 ° C, And the ASRs _electrode was approximately 0.035 ± 0.019 Ω · cm ² , 0.061 ± 0.018 Ω · cm ² , 0.129 ± 0.060 Ω · cm ² _and 0.314 ± 0.119 Ω · cm ² at 600 ℃, 550 ℃, 500 ℃ and 450 ℃ respectively Respectively. The cell exhibits a power density of approximately 1.7 to 1.9 W · cm ^-2 at approximately 550 ° C., but exhibits a large variation in OCV of less than 0.84 to 0.85 V at 500 ° C. in one or two experiments. While the operating temperature has to rise and the OCV has to rise, we can see that these cells increase only slightly. Most cells are coated with a constant, thin electrolyte of 5 to 6 μm, but low OCV cells have some problems found in coatings with a 3 μm thick electrolyte. The IV graph and the impedance graph were obtained by five cell experiments. In FIG. 20c and 20d, the power density of 1.8 ± 0.1 W · cm ^-2 at 550 ° C. and the ASRs _ohmic of 0.058 ± 0.004 Ω · cm ² _, 0.051 ± 0.008 Ω · cm It represented the ^two ASRs _electrode was confirmed that the reproducibility. To ensure the structural stability and durability of batteries with high power densities at low temperatures, 1 A · cm ^-2 was continuously supplied. Figure 20 e shows that maintaining 50 hours the cells with 0.776 V at 0.5 A cm ^-2 and the mixture was kept for 250 hours in 0.756 V and 1 A cm ^-2. Compared to a general GDC-based cell maintaining 0.7 V at 0.3 to 0.4 A · cm ^-2 , the battery has the effect of reducing the number of SOFC stacks and showing the possibility of being used for auxiliary power supply of automobiles. The voltage decrease was approximately 5.6% and 0.00017 V.H ^-1 when maintained at 1 A · cm ^-2 for 250 hours and approximately 0.6% and 0.00010 V · h ^-1 when maintained at 0.5 A · cm ^-2 for 50 hours. . This shows that LT-SOFCs based on GDC with high stability and high reproducibility at low temperature are manufactured.

Claims (17)

Core fibers of barium strontium cobalt iron oxide (BSCF) and
Including shell nanoparticles of an electrolyte material
Anode for Low Temperature Type Solid Oxide Fuel Cells.
delete The method according to claim 1,
The electrolyte material may be selected from the group consisting of yttria stabilized zirconia (YSZ), scandia stabilized zirconia (ScSZ), gadollo doping ceria (GDC), samarium doped ceria doped barium zirconate (BaZrO3) and barium cerate (BaCeO3) Lt; RTI ID = 0.0 &gt; solid oxide fuel cell &lt; / RTI &gt;
A positive electrode according to claim 1;
An electrolyte layer of an inorganic ore containing gadolya doped ceria (GDC);
An anode functional layer of a nanocomposite material comprising nickel and a gadolinium-doped ceria (GDC) electrolyte material; And
An anode support comprising nickel and a gadolinium-doped ceria (GDC) electrolyte material
Type solid oxide fuel cell.
5. The method of claim 4,
Wherein the electrolyte layer has a thickness of 4 to 10 占 퐉.
5. The method of claim 4,
Wherein the cathode functional layer has a thickness of 5 to 15 占 퐉.
delete 5. The method of claim 4,
Wherein the cathode comprises nickel and a gadolinium-doped ceria (GDC) electrolyte material.
5. The method of claim 4,
A solid oxide fuel cell satisfying general formula (1)
[Formula 1]
X? 1.5
And X represents the output (W / cm ² ) at a temperature of 550 ° C.
Forming core fibers with barium strontium cobalt iron oxide (BSCF);
Forming a shell of an electrolyte material on the core fiber;
Wherein the low-temperature-type solid oxide fuel cell comprises a cathode.
11. The method of claim 10,
Wherein the core fibers are formed by an electrospinning method.
11. The method of claim 10,
Wherein the shell is formed using a Perkinier process.
delete Preparing a negative electrode support comprising nickel and a gadolinium-doped ceria (GDC) electrolyte material;
Forming a negative electrode functional layer by coating and heat treating a slurry containing nickel and a Gadolinium Doped Ceria (GDC) electrolyte material on the negative electrode support;
Forming an electrolyte layer by dip coating a slurry containing an electrolyte material on the negative electrode functional layer; And
Preparing a positive electrode comprising core fibers of barium strontium cobalt iron oxide (BSCF) and shell nanoparticles of an electrolyte material on the central region of the electrolyte layer
Lt; RTI ID = 0.0 &gt; a &lt; / RTI &gt; low-temperature solid oxide fuel cell.
delete 15. The method of claim 14,
Wherein the slurry of the electrolyte layer has a viscosity of 2.4 to 2.6 cP at 25 占 폚.
15. The method of claim 14,
A method for producing a low temperature type solid oxide fuel cell satisfying the following general formula (1)
[Formula 1]
X? 1.5
And X represents the output (W / cm ² ) at a temperature of 550 ° C.

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