KR20070068141A - Cathode material for molten carbonate fuel cell and fuel cell using the same - Google Patents
Cathode material for molten carbonate fuel cell and fuel cell using the same Download PDFInfo
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- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 title claims abstract description 59
- 239000000446 fuel Substances 0.000 title claims abstract description 55
- 239000010406 cathode material Substances 0.000 title claims abstract description 39
- 229910000531 Co alloy Inorganic materials 0.000 claims abstract description 34
- QXZUUHYBWMWJHK-UHFFFAOYSA-N [Co].[Ni] Chemical compound [Co].[Ni] QXZUUHYBWMWJHK-UHFFFAOYSA-N 0.000 claims abstract description 29
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 26
- 229910017052 cobalt Inorganic materials 0.000 claims abstract description 11
- 239000010941 cobalt Substances 0.000 claims abstract description 11
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims abstract description 6
- 230000006698 induction Effects 0.000 abstract description 10
- 230000008018 melting Effects 0.000 abstract description 4
- 238000002844 melting Methods 0.000 abstract description 4
- 239000002994 raw material Substances 0.000 abstract 1
- 229910000480 nickel oxide Inorganic materials 0.000 description 15
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 14
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 8
- 239000003792 electrolyte Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 238000004090 dissolution Methods 0.000 description 5
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 238000011978 dissolution method Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- AHKZTVQIVOEVFO-UHFFFAOYSA-N oxide(2-) Chemical compound [O-2] AHKZTVQIVOEVFO-UHFFFAOYSA-N 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 230000002745 absorbent Effects 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000009616 inductively coupled plasma Methods 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229910001453 nickel ion Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 239000002028 Biomass Substances 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910010981 Li2CO3—Na2CO3 Inorganic materials 0.000 description 1
- 229910010586 LiFeO 2 Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- -1 alkaline earth metal carbonates Chemical class 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000003034 coal gas Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000011859 microparticle Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 230000007096 poisonous effect Effects 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229910000027 potassium carbonate Inorganic materials 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
- H01M4/9025—Oxides specially used in fuel cell operating at high temperature, e.g. SOFC
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/14—Fuel cells with fused electrolytes
- H01M2008/147—Fuel cells with molten carbonates
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Inert Electrodes (AREA)
- Fuel Cell (AREA)
Abstract
Description
도 1은 일반적인 용융탄산염 연료전지의 구성을 나타내는 구성도.1 is a block diagram showing the configuration of a typical molten carbonate fuel cell.
도 2는 종래의 용융탄산염 연료전지용 공기극 물질을 나타내는 구성도.2 is a block diagram showing a conventional cathode material for molten carbonate fuel cell.
도 3은 본 발명의 일실시예에 의한 용융탄산염 연료전지용 공기극 물질을 나타내는 구성도.3 is a block diagram showing a cathode material for a molten carbonate fuel cell according to an embodiment of the present invention.
도 4는 본 발명의 일실시예에 의한 용융탄산염 연료전지용 공기극 물질의 용해도를 나타내는 그래프.Figure 4 is a graph showing the solubility of the cathode material for molten carbonate fuel cell according to an embodiment of the present invention.
<도면의 주요부분에 대한 부호의 설명><Description of the symbols for the main parts of the drawings>
1 : 니켈-코발트 합금 산화물1: nickel-cobalt alloy oxide
2 : 산화니켈2: nickel oxide
본 발명은 용융탄산염 연료전지용 공기극 물질 및 이를 이용한 연료전지에 관한 것으로서, 보다 상세하게는 용융탄산염 연료전지용 공기극 물질의 대량 생산 공정을 확립하기 위해 탄산염 내에서의 안정성을 가진 니켈-코발트 합금 산화물로 이루어진 용융탄산염 연료전지용 공기극 물질 및 이를 이용한 연료전지에 관한 것이다. The present invention relates to a cathode material for a molten carbonate fuel cell and a fuel cell using the same, and more particularly, to a nickel-cobalt alloy oxide having stability in carbonate to establish a mass production process of the cathode material for a molten carbonate fuel cell. A cathode material for a molten carbonate fuel cell and a fuel cell using the same.
일반적으로, 연료전지는 탄화수소 등의 화학연료가 가지고 있는 화학에너지를 전기에너지로 직접 전환시키는 장치로, 600℃ 이상의 고온에서 작동하는 연료전지로는 용융탄산염 연료전지와 고체 산화물형 연료전지를 들 수 있다. In general, a fuel cell is a device that directly converts chemical energy contained in chemical fuels such as hydrocarbons into electrical energy. Fuel cells operating at a high temperature of 600 ° C. or higher include molten carbonate fuel cells and solid oxide fuel cells. have.
특히 제 2 세대 연료전지로 불리는 용융탄산염 연료전지는 다른 형태의 연료전지와 함께 높은 열효율, 높은 환경 친화성, 모듈화 특성 및 작은 설치공간으로 대표되는 장점을 공유하는 동시에, 650℃의 고온에서 운전되기 때문에 인산형 또는 고분자 연료전지와 같은 저온형 연료전지에서 기대할 수 없는 다음과 같은 추가 장점이 있었다. In particular, molten carbonate fuel cells, called second-generation fuel cells, share the advantages of high thermal efficiency, high environmental friendliness, modularity, and small footprint with other fuel cells, while operating at high temperatures of 650 ° C. Therefore, there are additional advantages that cannot be expected in low temperature fuel cells such as phosphoric acid or polymer fuel cells.
즉, 고온에서의 빠른 전기화학반응은 전극재료를 백금 대신 저렴한 니켈의 사용을 가능케 하여 경제성에서 유리할 뿐만 아니라, 백금전극에 피독물질로 작용하는 일산화탄소마저도 수성가스 전환반응을 통하여 연료로 이용하는 니켈전극의 특성은 석탄가스, 천연가스, 메탄올, 바이오매스 등 다양한 연료 선택성을 제공한다. In other words, the rapid electrochemical reaction at high temperature enables the use of inexpensive nickel instead of platinum, which is advantageous in terms of economic efficiency, and even carbon monoxide, which acts as a poisonous substance on the platinum electrode, is used as a fuel through the water gas conversion reaction. Properties offer a variety of fuel selectivities, including coal gas, natural gas, methanol, and biomass.
그러나 이와 같이 탄산염 흡수물질을 사용하여 탄산염 성분을 제거하는 경 우, 탄산염 전해질 층으로부터 탄산염 흡수물질로 계속적인 탄산염 전달이 일어나 전해질층 내의 탄산염이 소모되어 오히려 연료전지의 수명이 단축되고, 탄산염을 흡수하는 무기물질에 의해 연료전지 내부의 저항값이 증가하는 문제점이 있었다.However, when the carbonate component is removed using the carbonate absorbent in this way, continuous carbonate transfer occurs from the carbonate electrolyte layer to the carbonate absorbent material, which consumes the carbonate in the electrolyte layer, thereby shortening the life of the fuel cell and absorbing the carbonate. There is a problem in that the resistance value of the fuel cell is increased by the inorganic material.
도 1은 일반적인 용융탄산염 연료전지의 구성을 나타내는 구성도이고, 도 2는 종래의 용융탄산염 연료전지용 공기극 물질을 나타내는 구성도이다.1 is a block diagram showing the configuration of a typical molten carbonate fuel cell, Figure 2 is a block diagram showing a conventional cathode material for molten carbonate fuel cells.
도 1에 표시된 바와 같이, 일반적인 용융탄산염 연료전지는 음극인 연료극(20)에 수소(H2)가 공급되어 물(H2O)과 이산화탄소(CO2)가 배출되고, 양극인 공기극(10)에는 산소(O2)와 이산화탄소(CO2)가 공급되어 전해질(40)에서 탄산이온(CO3 2-)으로 변환된다. 따라서 연료극(20)의 전자(e-)들이 공기극(10)으로 이동하면서 저항체(30)에 전류가 흐르게 된다.As shown in FIG. 1, in a typical molten carbonate fuel cell, hydrogen (H 2 ) is supplied to the
도 2에 표시된 바와 같이, 종래의 용융탄산염 연료전지용 공기극 물질은 산화니켈(2)에 니켈-코발트 합금 산화물(1)을 코팅하여 이루어진 것이므로, 코팅된 니켈-코발트 합금 산화물(1)에 의해서 용융탄산염 연료전지의 공기극이 탄산염 내에서 용해속도가 느려져서 용융탄산염 연료전지의 장기운전이 가능하게 된다.As shown in FIG. 2, the conventional cathode material for molten carbonate fuel cells is formed by coating nickel-cobalt alloy oxide (1) on nickel oxide (2), and thus, molten carbonate by the coated nickel-cobalt alloy oxide (1). The cathode of the fuel cell has a slow dissolution rate in the carbonate, thereby enabling long-term operation of the molten carbonate fuel cell.
그러나 용융탄산염 연료전지의 상용화를 위한 과제는 공기극 물질에 대한 탄산염 내에서의 용해도에 의거해서 운전시간이 결정되므로, 용해도를 저하시키는 방안에 대한 연구의 필요성이 대두되었다. 따라서, 용해도는 전해질 조성이나 공기극 물질에 의해 영향을 받게 되므로, 전해질 조성이나 공기극 물질에 대한 구체적인 연구가 진행되었다.However, the task for commercialization of the molten carbonate fuel cell is to determine the operation time based on the solubility in the carbonate to the cathode material, so the need for research to reduce the solubility has emerged. Therefore, since solubility is affected by the electrolyte composition and the cathode material, specific studies on the electrolyte composition and the cathode material have been conducted.
특히, 종래의 용융탄산염 연료전지용 공기극 물질은 코팅된 니켈-코발트 합금 산화물(1)이 용해된 후에는 내부의 산화니켈(2)이 용해되므로, 용해된 니켈 이온이 연료극 쪽으로 이동하여 금속상태로 환원되어 지지체 내에 금속성 니켈 입자로서 침적되기 때문에 산화니켈의 용해도를 해결하는 것도 주요 해결과제 중 하나였다. In particular, in the conventional cathode material for molten carbonate fuel cells, after the coated nickel-cobalt alloy oxide (1) is dissolved, the nickel oxide (2) therein is dissolved, so that the dissolved nickel ions move toward the anode and are reduced to a metal state. It was also one of the main challenges to solve the solubility of nickel oxide because it is deposited as metallic nickel particles in the support.
즉, 연료극 쪽으로 이동하여 니켈이온이 침적되면, 전극간 단락현상을 일으키게 하고 또 출력손실을 유발하는 문제가 있었다. 또한, 용해침적과정이 재질 손실 및 지지체 내 전해질 치환 때문에 공기극의 구조적 변화를 유발하게 되는 문제점도 있었다. That is, when nickel ions move toward the anode and are deposited, there is a problem of causing a short circuit between the electrodes and causing an output loss. In addition, there is a problem that the dissolution deposition process causes structural changes in the cathode due to material loss and electrolyte replacement in the support.
본 발명은 상기와 같은 종래의 문제점을 해소하기 위해 안출한 것으로서, 니켈-코발트 합금 산화물을 용융탄산염 연료전지용 공기극 물질로 사용하므로, 종래의 공기극 물질에 비해 대량생산이 용이하며, 코발트가 공기극 물질 내부에도 존재하게 되어 장시간 동안 탄산염에 안정하고, 니켈과 코발트의 성분비를 소정값으로 한정하므로, 니켈-코발트 합금 산화물의 용해도를 향상시킬 수 있는 용융탄산염 연료전지용 공기극 물질 및 이를 이용한 연료전지를 제공하는 것을 그 목적으로 한다. The present invention has been made to solve the above conventional problems, and since nickel-cobalt alloy oxide is used as a cathode material for a molten carbonate fuel cell, mass production is easier than that of a conventional cathode material, and cobalt is contained in the cathode material. The present invention also provides a cathode material for a molten carbonate fuel cell and a fuel cell using the same, which are present in the present invention and are stable to carbonate for a long time and limit the component ratio of nickel and cobalt to a predetermined value. For that purpose.
상기와 같은 목적을 달성하기 위한 본 발명은, 용융탄산염 연료전지용 공기극 물질로서, 니켈-코발트 합금 산화물로 이루어진 것을 특징으로 한다.The present invention for achieving the above object, characterized in that the cathode material for molten carbonate fuel cell, made of a nickel-cobalt alloy oxide.
보다 바람직하게, 상기 니켈-코발트 합금 산화물은 니켈과 코발트의 성분비(wt%)가 97:3 내지 90:10으로 이루어진 것을 특징으로 한다.More preferably, the nickel-cobalt alloy oxide is characterized in that the component ratio (wt%) of nickel and cobalt is 97: 3 to 90:10.
보다 바람직하게, 상기 니켈-코발트 합금 산화물은 진공분위기에서 15∼20㎾의 고압을 인가하여 대략 5∼15분 동안 진공유도 용해된 니켈-코발트 합금으로 이루어진 것을 특징으로 한다.More preferably, the nickel-cobalt alloy oxide is made of a nickel-cobalt alloy in which vacuum induction is dissolved for about 5 to 15 minutes by applying a high pressure of 15 to 20 kPa in a vacuum atmosphere.
보다 바람직하게, 상기 기재된 용융탄산염 연료전지용 공기극 물질을 공기극으로 사용하는 것을 특징으로 한다.More preferably, the cathode material for molten carbonate fuel cell described above is used as the cathode.
이하, 첨부도면을 참조하여 본 발명의 바람직한 일실시예를 더욱 상세히 설명한다. Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.
도 3은 본 발명의 일실시예에 의한 용융탄산염 연료전지용 공기극 물질을 나타내는 구성도이고, 도 4는 본 발명의 일실시예에 의한 용융탄산염 연료전지용 공기극 물질의 용해도를 나타내는 그래프이다.3 is a block diagram showing a cathode material for a molten carbonate fuel cell according to an embodiment of the present invention, Figure 4 is a graph showing the solubility of the cathode material for molten carbonate fuel cell according to an embodiment of the present invention.
도 3에 표시된 바와 같이, 본 실시예의 용융탄산염 연료전지용 공기극 물질은 공기극 물질 전체가 니켈-코발트 합금 산화물로 이루어져 있고, 진공 유도 용해법(Vacuum Induction Melting method; VIM)을 이용하여 니켈-코발트 합금을 제조한 후 탄산염 내에서 운전 중 산화시켜 산화물이 되었을 경우 실제 운전 조건에서 용해도가 향상되는 공기극 물질에 관한 것이다.As shown in FIG. 3, the cathode material for the molten carbonate fuel cell of the present embodiment is made of nickel-cobalt alloy oxide as a whole of the cathode material, and a nickel-cobalt alloy is manufactured by using a vacuum induction melting method (VIM). The present invention relates to a cathode material which improves solubility under actual operating conditions when the oxide is oxidized during operation in a carbonate.
용융탄산염 연료전지에 있어서 공기극 물질중 산화니켈(NiO)의 용해도는 염기성 또는 산화물이온농도(higher basicity or oxide ion concentration; O2-)가 높을수록 전해질 조성에서 감소된다. In a molten carbonate fuel cell, the solubility of nickel oxide (NiO) in the cathode material decreases in electrolyte composition with higher basic or oxide ion concentration (O 2- ).
따라서, 전형적인 용융탄산염 연료전지의 조업조건에서는 산화니켈이 반응식 1과 같이 산성용해형태(acidic dissolution)로 진행하게 된다.Therefore, in the operating conditions of a typical molten carbonate fuel cell, nickel oxide proceeds in an acidic dissolution form as in
즉, 산화물이온함량이 많을 수록 Ni2+농도는 낮게 유지된다. In other words, the higher the oxide ion content, the lower the Ni 2+ concentration.
특히, 반응식 2에 표시된 바와 같이, 산화물 이온농도는 이산화탄소 분압 및 알칼리 탄산염의 해리 상수에 의해 변화된다. In particular, as shown in
일반적으로 쓰이는 알칼리 탄산염들의 상대적인 염기도는 다음의 비교식과 같다.The relative basicity of alkali carbonates in general use is shown in the following comparison.
<비교식><Comparative Ceremony>
(basic)Li2CO3 > Na2CO3 > K2CO3(acidic)(basic) Li 2 CO 3 > Na 2 CO 3 > K 2 CO 3 (acidic)
따라서 NiO의 용해도는 Li2CO3-K2CO3혼합물에서 보다 Li2CO3-Na2CO3혼합물 내에 서 더 낮게 형성된다. 어떠한 2-성분계이든 NiO의 용해도는 공융조성 이외에서는 Li의 농도가 증가함에 따라서 증가하게 된다. Thus, the solubility of NiO is lower in the Li 2 CO 3 -Na 2 CO 3 mixture than in the Li 2 CO 3 -K 2 CO 3 mixture. The solubility of NiO in any two-component system increases with increasing Li concentration, except for eutectic composition.
공기극 쪽 전지 몸체의 부식속도는 62% Li2CO3-38% K2CO3 및 52% Li2CO3-48% Na2CO3 공비조성에서 최소로 나타난다. The corrosion rate of the battery body on the cathode side is minimal at 62% Li 2 CO 3 -38% K 2 CO 3 and 52% Li 2 CO 3 -48% Na 2 CO 3 azeotrope.
이러한 2-혼합물계에 알칼리 토금속 탄산염을 추가하면 산화니켈 용해도는 감소하게 된다. 특히 MgO, CaCO3, SrCO3 및 BaCO3를 추가하면 모든 전해액의 염기도가 증가함으로써, 이 2-성분계 탄산염 내에 용해되어 있는 Ni의 농도를 감소시키게 된다.The addition of alkaline earth metal carbonates to this two-mixture system reduces nickel oxide solubility. In particular, addition of MgO, CaCO 3 , SrCO 3 and BaCO 3 increases the basicity of all the electrolytes, thereby reducing the concentration of Ni dissolved in this two-component carbonate.
공기극 반응의 저속특성 및 기타 기구를 규명하기 위해 복합산화물을 가하여 시험한 결과를 제시한 바도 있고, 산화니켈을 다른 대체물질로 교체하여 성능검토를 시행한 바도 있다. In order to identify the low-speed characteristics and other mechanisms of the cathode reaction, the results of the tests with the addition of composite oxides have been presented, and the performance review has been carried out by replacing nickel oxide with another substitute.
특히 열역학적으로 안정한 세라믹산화물(LiFeO2)은 용해속도가 거의 영(zero)에 해당되나 소형전지의 시험결과에서 저성능을 나타내었다. LiCoO2는 대기압에서 작동시 NiO에 비해 절반 정도의 용해도를 나타내었다. In particular, thermodynamically stable ceramic oxides (LiFeO 2 ) showed almost zero dissolution rates, but showed low performance in small cell test results. LiCoO 2 exhibited about half solubility compared to NiO when operated at atmospheric pressure.
그러나 LiCoO2는 그 가격이 비싸고 성형이 쉽지 않아 이를 이용하여 기존의 니켈 입자 주위에 LiCoO2 미세입자를 피복하여 전극을 성형하는 기법이 시도되었고 그 결과 용해도 향상의 결과를 얻었다. However, LiCoO 2 is expensive and not easy to form, so a method of forming an electrode by coating LiCoO 2 microparticles around the existing nickel particles has been attempted, resulting in improved solubility.
LiCoO2가 코팅된 NiO의 용해도가 향상된 결과는 실제 표면에 형성된 니켈-코 발트 합금 산화물의 영향으로 밝혀졌으며 코발트의 첨가로 인한 산화니켈 구조가 보다 안정화된 것이 그 원인으로 파악되었다.The improved solubility of LiCoO 2 -coated NiO was found to be due to the effect of nickel-cobalt alloy oxides formed on the actual surface, which was attributed to the more stable nickel oxide structure due to the addition of cobalt.
따라서 이러한 근거에 의거하여 본 발명에서는 공기극 물질 전체가 진공 유도 용해법에 의한 니켈-코발트 합금 산화물로 이루어지고, 이러한 니켈-코발트 합금 산화물은 니켈과 코발트의 성분비(wt%)가 97:3 내지 90:10으로 이루어지는 것이 바람직하다.Accordingly, in the present invention, the entire cathode material is made of nickel-cobalt alloy oxide by vacuum induction dissolution method, and the nickel-cobalt alloy oxide has a component ratio (wt%) of nickel and cobalt of 97: 3 to 90: It is preferable that it consists of ten.
즉, 성분비가 97:3 보다 작으면 용해도의 향상이 이루어지지 않아 효과를 나타낼 수 없고, 90:10 보다 높으면 고가의 코발트의 사용량이 증가하여 비용이 증가하므로 경제성이 저하하게 되므로, 니켈과 코발트의 성분비(wt%)는 97:3 내지 90:10으로 적용하는 것이 바람직하며, 최적의 효과를 나타내기 위해서는 97:3 내지 95:5로 적용하는 것이 더욱 바람직하다.In other words, if the component ratio is less than 97: 3, the solubility is not improved, and the effect cannot be exhibited. If the ratio is higher than 90:10, the use of expensive cobalt increases and the cost increases, thereby lowering the economical efficiency of nickel and cobalt. The component ratio (wt%) is preferably applied in a range of 97: 3 to 90:10, and more preferably in a range of 97: 3 to 95: 5 in order to exhibit an optimal effect.
진공 유도 용해법(Vacuum Induction Melting method; VIM)은 유럽 공개특허공보 제0127430호(1984.12.05)에 개시된 바와 같이, 근간의 보편화된 기술로서 자체 섞임 작용의 유도가열과 자체탈가스의 진공가열에 의해 우수한 고 청정성과 균일한 조직이 얻어지며, 진공 내에서 합금이 이루어져서 탈가스된 합금을 얻을 수 있는 특성이 있다. Vacuum Induction Melting method (VIM), as disclosed in European Patent Publication No. 0227430 (December 5, 1984), is a generalized technology based on induction heating of self-mixing action and vacuum heating of self degassing. Excellent high cleanliness and uniform structure are obtained, and the alloy is made in vacuum to obtain the degassed alloy.
본 실시예의 니켈-코발트 합금에 대한 진공 유도 용해의 조건으로는 대략 2×10-3Torr 정도의 진공분위기에서 15∼20㎾의 고압을 인가하여 대략 5∼15분 동안 진공유도 용해되는 것이 바람직하다. As a condition of vacuum induction melting of the nickel-cobalt alloy of this embodiment, it is preferable that a vacuum oil is also dissolved for about 5 to 15 minutes by applying a high pressure of 15 to 20 kPa in a vacuum atmosphere of approximately 2 x 10 -3 Torr. .
즉, 인가전력이 15㎾보다 적으면 용해성이 저하되고, 20㎾보다 크면 과부하의 위험이 있고, 용해시간도 5분 보다 짧으면 용해성이 저하되고, 15분 보다 길면 전력이 손실이 과다하게 발생하여 경제성이 저하되므로 부적합하다.In other words, if the applied power is less than 15 kW, the solubility is lowered. If the applied power is more than 20 kW, there is a risk of overload. If the dissolution time is shorter than 5 minutes, the solubility is lowered. It is inferior because it falls.
다음은 본 발명의 실시예에 의거해서 구제적으로 설명한다.The following describes in detail based on the embodiment of the present invention.
(실시예)(Example)
우선, 진공 유도 용해법을 이용하여 니켈-코발트 합금을 준비하고 탄산염 내에서 실험 중 산화시켜 그 산화물을 얻는다. 즉, 99wt% 니켈 - 1wt% 코발트 합금과, 97wt% 니켈 - 3wt% 코발트 합금을 진공 유도 용해법을 이용하여 준비한다. First, a nickel-cobalt alloy is prepared using a vacuum induction dissolution method and oxidized in an experiment in carbonate to obtain its oxide. That is, 99 wt% nickel-1 wt% cobalt alloy and 97 wt% nickel-3 wt% cobalt alloy are prepared by using a vacuum induction dissolution method.
따라서, 먼저 전체 300g의 합금을 얻을 수 있도록 각각의 무게를 계량하여 용해용기에 투입하고, 대략 2×10-3Torr 정도의 진공분위기 하에서 15㎾의 고압을 인가하여 10분 동안 유도 용해시킨다. Therefore, first, each weight is weighed in order to obtain a total of 300 g of alloy, and then dissolved in an induction furnace for 10 minutes by applying a high pressure of 15 kPa under a vacuum atmosphere of approximately 2 × 10 -3 Torr.
이렇게 얻어진 합금을 약 5㎜×5㎜×5㎜의 입방체 형태로 절단하여, 10개씩 알루미나 도가니에 투입하여, 650℃로 가열하면서 250시간 동안 용해도를 측정하였다.The alloy thus obtained was cut into a cube shape of about 5 mm x 5 mm x 5 mm, 10 pieces were put into an alumina crucible, and the solubility was measured for 250 hours while heating at 650 ° C.
이때, 전해질로는 62:38의 몰 비로 혼합된 탄산리튬과 탄산칼륨의 혼합 탄산염을 사용하고, 2:1의 부피비로 이산화탄소와 산소를 공급하면서 실험 분위기를 유지시켜 주었다.At this time, a mixed carbonate of lithium carbonate and potassium carbonate mixed in a molar ratio of 62:38 was used, and the experimental atmosphere was maintained while supplying carbon dioxide and oxygen in a volume ratio of 2: 1.
일정한 시간이 지날 때마다 알루미나 피펫을 이용하여 탄산염을 약 0.3g 정도를 수취하여 두고, 얻어진 탄산염 시료는 1N 질산에 녹여 ICP(Inductively Coupled Plasma)를 이용하여 니켈의 용해도를 측정하였다.After a certain time, about 0.3 g of carbonate was received using an alumina pipette, and the obtained carbonate sample was dissolved in 1N nitric acid, and the solubility of nickel was measured by using ICP (Inductively Coupled Plasma).
도 4는 99wt% 니켈 - 1wt% 코발트 합금 산화물과 97wt% 니켈 - 3wt% 코발트 합금 산화물의 용융탄산염 내에서의 니켈의 용해도를 측정한 그래프이다. 4 is a graph measuring the solubility of nickel in molten carbonate of 99 wt% nickel-1 wt% cobalt alloy oxide and 97 wt% nickel-3 wt% cobalt alloy oxide.
도 4에 표시된 바와 같이, 99wt% 니켈 - 1wt% 코발트 합금 산화물의 경우 그 용해도가 산화니켈을 사용한 경우와 비슷하여 효과를 기대할 수 없었으나, 97wt% 니켈 - 3wt% 코발트 합금 산화물은 용해도가 많이 향상되었음을 알 수가 있었다.As shown in FIG. 4, in the case of 99 wt% nickel-1 wt% cobalt alloy oxide, the solubility was similar to that in which nickel oxide was used, but an effect could not be expected. I could see that.
이상 설명한 본 발명은 그 기술적 사상 또는 주요한 특징으로부터 벗어남이 없이 다른 여러 가지 형태로 실시될 수 있다. 따라서 상기 실시예는 모든 점에서 단순한 예시에 지나지 않으며 한정적으로 해석되어서는 안 된다. The present invention described above can be embodied in many other forms without departing from the spirit or main features thereof. Therefore, the above embodiments are merely examples in all respects and should not be interpreted limitedly.
이상에서 살펴본 바와 같이, 본 발명은 니켈-코발트 합금 산화물을 용융탄산염 연료전지용 공기극 물질로 사용하므로, 종래의 공기극 물질에 비해 대량생산이 용이하며, 코발트가 공기극 물질 내부에도 존재하게 되어 장시간 동안 탄산염에 안정한 용융탄산염 연료전지용 공기극 물질을 얻을 수 있는 효과가 있다.As described above, since the present invention uses nickel-cobalt alloy oxide as a cathode material for a molten carbonate fuel cell, mass production is easier than that of a conventional cathode material, and cobalt is also present in the cathode material, and thus, There is an effect that a cathode material for a stable molten carbonate fuel cell can be obtained.
또한, 니켈과 코발트의 성분비를 소정값으로 한정하므로, 니켈-코발트 합금 산화물의 용해도를 향상시킬 수 있는 효과가 있다.In addition, since the component ratio of nickel and cobalt is limited to a predetermined value, there is an effect of improving the solubility of the nickel-cobalt alloy oxide.
니켈-코발트 합금 산화물을 공기극 물질로 사용하므로 가동시간을 연장시킬 수 있는 용융탄산염 연료전지를 얻을 수 있는 효과가 있다.Since nickel-cobalt alloy oxide is used as the cathode material, there is an effect of obtaining a molten carbonate fuel cell that can extend the operating time.
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