SOFC anode morphology에 의한 출력 특성

지미정(Mijung Ji),구자빈(Jabin Koo),이은정(Enjung Lee),이서환(seohwan Lee),최병현(Byunghyun Choi) 한국신재생에너지학회 2016 한국신재생에너지학회 학술대회논문집 Vol.2016 No.5

Pb-Free 백색유전체에서 필러함량과 소성온도에 따른 유전체 특성

안용태,최병현,지미정,이정민,김형순,정경원,An, Yong-Tae,Choi, Byung-Hyun,Ji, Mi-Jung,Lee, Jung-Min,Kim, Hyun-Sun,Jung, Kyung-Won 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.8

For the development of a new white dielectric layer in plasma display panel, different $TiO_2$ types as a filler was add to the $Bi_2O_3$-BaO-ZnO glass matrix. The reflectance and dielectric constant of dielectric have been investigated as a function of the mixing content (rutile and anatase), and sintering temperature. The reflectance of dielectric sintered at the 520$^{\circ}C$ appeared most highly and suitable in terms of the adhesion and reflectance of the soda-lime glasses. Also, the thermal expansion coefficient of dielectric was found to be $85.6\times10^{-7}/K$, which was similar to that of the soda-lime glasses. Especially, the dielectric constants were not increased with increasing of $TiO_2$ filler contents.

TiCl₄를 출발원료로한 구형 Li₄Ti₅O₁₂ 분말합성 및 리튬이차 전지특성

최병현,지미정,권용진,김은경,남산,Choi, Byung-Hyun,Ji, Mi-Jung,Kwon, Yong-Jin,Kim, Eun-Kyung,Nahm, Sahn 한국재료학회 2010 한국재료학회지 Vol.20 No.12

One of the greatest challenges for our society is providing powerful electrochemical energy conversion and storage devices. Rechargeable lithium-ion batteries and fuel cells are among the most promising candidates in terms of energy and power density. As the starting material, $TiCl_4{\cdot}YCl_3$ solution and dispersing agent (HCP) were mixed and synthesized using ammonia as the precipitation agent, in order to prepare the nano size Y doped spherical $TiO_2$ precursor. Then, the $Li_4Ti_5O_{12}$ was synthesized using solid state reaction method through the stoichiometric mixture of Y doped spherical $TiO_2$ precursor and LiOH. The Ti mole increased the concentration of the spherical particle size due to the addition of HPC with a similar particle size distribution in a well in which $Li_4Ti_5O_{12}$ spherical particles could be obtained. The optimal synthesis conditions and the molar ratio of the Ti 0.05 mol reaction at $50^{\circ}C$ for 30 minutes and at $850^{\circ}C$ for 6 hours heat treatment time were optimized. $Li_4Ti_5O_{12}$ was prepared by the above conditions as a working electrode after generating the Coin cell; then, electrochemical properties were evaluated when the voltage range of 1.5V was flat, the initial capacity was 141 mAh/g, and cycle retention rate was 86%; also, redox reactions between 1.5 and 1.7V, which arose from the insertion and deintercalation of 0.005 mole of Y doping is not a case of doping because the C-rate characteristics were significantly better.

전사지를 이용 적층한 셀 구조 및 연료극 기능층 형성에 따른 출력 특성

안용태,지미정,구자빈,최진훈,황해진,최병현,An, Yong-Tae,Ji, Mi-Jung,Gu, Ja-Bin,Choi, Jin-Hoon,Hwang, Hae-Jin,Choi, Byung-Hyun 한국재료학회 2012 한국재료학회지 Vol.22 No.11

The properties of SOFC unit cells manufactured using the decalcomania method were investigated. SOFC unit cell manufacturing using the decalcomania method is a very simple process. In order to minimize the ohmic loss of flattened tube type anode supports of solid oxide fuel cells(SOFC), the cells were fabricated by producing an anode function layer, YSZ electrolyte, LSM electrode, etc., on the supports and laminating them. The influence of these materials on the power output characteristics was studied when laminating the components and laminating the anode function layer between the anode and the electrolyte to improve the output characteristics. Regarding the performance of the SOFC unit cell, the output was 246 $mW/cm^2$ at a temperature of $800^{\circ}C$ in the case of not laminating the anode function layer; however, this value was improved by a factor of two to 574 $mW/cm^2$ due to the decrease of the ohmic resistance and polarization resistance of the cell in the case of laminating the anode function layer. The outputs appeared to be as high as 574 and 246 $mW/cm^2$ at a temperature of $800^{\circ}C$ in the case of using decalcomania paper when laminating the electrolyte layer using the in dip-coating method; however, the reason for this is that interfacial adhesion was improved due to the dense structure, which leads to a thin thickness of the electrolyte layer.

전사지를 이용한 다전지식 평관형 고체산화물 연료전지 제작 및 셀 특성

안용태,지미정,박선민,신상호,황해진,최병현,An, Yong-Tae,Ji, Mi-Jung,Park, Sun-Min,Shin, Sang-Ho,Hwang, Hae-Jin,Choi, Byung-Hyun 한국재료학회 2013 한국재료학회지 Vol.23 No.3

In the segmented-in-series solid-oxide fuel cells (SIS-SOFCs), fabrication techniques which use decalcomania paper have many advantages, i.e., an increased active area of the electrode; better interfacial adhesion property between the anode, electrolyte and cathode; and improved layer thickness uniformity. In this work, a cell-stack was fabricated on porous ceramic flattened tube supports using decalcomania paper, which consists of an anode, electrolyte, and a cathode. The anode layer was $40{\mu}m$ thick, and was porous. The electrolyte layers exhibited a uniform thickness of about $20{\mu}m$ with a dense structure. Interfacial adhesion was improved due to the dense structure. The cathode layers was $30{\mu}m$ thick with porous structure, good adhesion to the electrolyte. The ohmic resistance levels at 800, 750 and $700^{\circ}C$ were measured, showing values of 1.49, 1.58 and $1.65{\Omega}{\cdot}cm^2$, respectively. The polarization resistances at 800, 750 and $700^{\circ}C$ were measured to be 1.63, 2.61 and $4.17cm^2$, respectively. These lower resistance values originated from the excellent interfacial adhesion between the anode, electrolyte and cathode. In a two-cell-stack SOFC, open-circuit voltages(OCVs) of 1.915, 1.942 and 1.957 V and maximum power densities(MPD) of 289.9, 276.1 and $220.4mW/cm^2$ were measured at 800, 750 and $700^{\circ}C$, respectively. The proposed fabrication technique using decalcomania paper was shown to be feasible for the easy fabrication of segmented-in-series flattened tube SOFCs.

리튬이온이차전지용 구형 Li₄Ti₅O₁₂ 음극 합성 및 Y와 Nb 도핑에 따른 전기화학적 특성

지미정,권용진,김은경,박태진,정성헌,최병현,Ji, Mi-Jung,Kwon, Yong-Jin,Kim, Eun-Kyung,Park, Tae-Jin,Jung, Sung-Hun,Choi, Byung-Hyun 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.6

Yttrium (Y) and niobium (Nb) doped spherical $Li_4Ti_5O_{12}$ were synthesized to improve the energy density and electrochemical properties of anode material. The synthesized crystal was $Li_4Ti_5O_{12}$, the particle size was less than $1{\mu}m$ and the morphology was spherical and well dispersed. The Y and Nb optimal doping amounts were 1 mol% and 0.5 mol%, respectively. The initial capacity of the dopant discharge and charge capacity were respectively 149mAh/g and 143 mAh/g and were significantly improved compared to the undoped condition at 129 mAh/g. Also, the capacity retention of 0.2 C/5 C was 74% for each was improved to 94% and 89%. It was consequently found that Y and Nb doping into the $Li_4Ti_5O_{12}$ matrix reduces the polarization and resistance of the solid electrolyte interface (SEI) layer during the electrochemical reaction.

용매열 합성법을 통하여 알루미늄을 도핑한 니켈옥사이드의 제조와 그 결정구조적, 전기적 특성

홍선기,지미정,이민진,정성헌,설광희,최병현,Hong, Sun-Ki,Ji, Mi-Jung,Lee, Min-Jin,Jung, Sung-Hun,Seol, Kwang-Hee,Choi, Byung-Hyun 한국재료학회 2012 한국재료학회지 Vol.22 No.11

Nickel oxide was doped with a wide range of concentrations (mol%) of Aluminum (Al) by solvothermal synthesis; single-phased nano powder of nickel oxide was generated after calcination at$900^{\circ}C$. When the concentration of Al dopant was increased, the reduced intensity was confirmed through XRD analysis. Lattice parameters of the synthesized NiO powder were decreased after treatment of the dopant; parameters were increased when the concentration of Al was over the doping limit (5 mol% Al). The binding energy of $Ni^{2+}$ was chemically shifted to $Ni^{3+}$ by doping $Al^{3+}$ ion, as confirmed by the XPS analysis. The tilted structure of the synthesized NiO with 5 mol% Al dopant and the polycrystalline structure of the $Ni_{0.75}Al_{0.25}O$ were observed by HR-TEM analysis. The electrical conductivity of the newly synthesized NiO was highly improved by Al doping in the conductivity test. The electrical conductivity values of the commercial NiO and the synthesized NiO with 5 mol% Al dopant ($Ni_{0.95}Al_{0.05}O$) were 1,400 s/cm and 2,230 s/cm at $750^{\circ}C$, respectively. However, the electrical conductivity of the synthesized NiO with 10 mol% Al dopant ($Ni_{0.9}Al_{0.1}O$) decreased due to the scattering of free-electrons caused by the large number of impurity atoms; the electrical conductivity of $Ni_{0.9}Al_{0.1}O$ was 545 s/cm at $750^{\circ}C$.

전사법에 의한 SOFC 연료극 지지체 단위셀 구성에서 기능층의 효과

조해란 ( Hae Ran Ch ),최병현 ( Byung Hyun Choi ),안용태 ( Yong Tae An ),구자빈 ( Ja Bin Koo ),백성현 ( Sung Hyeon Baeck ),노광철 ( Kwang Chul Roh ),지미정 ( Mi Jung Ji ),박선민 ( Sun Min Park ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.2

In this study, we fabricated anode-supported solid oxide fuel cells by the decalcomania method. To investigate the effect of the anode functional layer (AFL) in a cell, AFL decalcomania paper was coated between the electrolyte and the anode support. The results showed that the surface roughness of the electrolyte coated on the anode support was not uniform (Ra = 7.86 nm), but that of electrolyte coated on AFL was uniform. A thin electrolyte layer with very low surface roughness was obtained. Then Ra was 2.65 nm. In this case, while the output power of the cell with the AFL (Cell 2) had an open circuit voltage (OCV) of 1.12 V and a maximum power density (MPD) of 650 mW cm-2 at 800℃, the cell without the AFL layer (Cell 1) had an OCV of 0.9 V and an MPD of 635 mW cm-

RF-마그네트론 스퍼터링에 의해 제조된 In_1.6Zn_0.2Sn_0.2O_3-_δ 박막의 투과율 및 전기 전도성에 미치는 증착 온도의 영향

서한,지미정,안용태,주병권,최병현,Seo, Han,Ji, Mi-Jung,An, Yong-Tea,Ju, Byeong-Kwon,Choi, Byung-Hyun 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.6

In order to reduce the indium contents in transparent conducting oxide(TCO) thin films of $In_{1.6{\sim}1.8}Zn_{0.2}Sn_{0.2{\sim}0.4}O_3$ (IZTO), $In_{1.6}Zn_{0.2}Sn_{0.2}O_{3-{\delta}}$(IZTO) was prepared by replacing indium with Zn and Sn. The TCO films were deposited via RF-magnetron sputtering of the IZTO target at various deposition temperatures and its film characteristics were investigated. When deposited in an Ar atmosphere at $400^{\circ}C$, the electrical resistivity of the film decreased to $6.34{\times}10^{-4}{\Omega}{\cdot}cm$ and the optical transmittance was 80%. As the deposition temperature increased, the crystallinity of the IZTO film was enhanced. As a result, the electrical conductivity and transmittance properties were improved. This demonstrates the possibility of replacing ITO TCO film with IZTO.

Li_4Ti_5O_12 Nanofiber의 전기화학적 특성에 미치는 Oleic Acid 코팅 효과

김은경 ( Eun Kyung Kim ),최병현 ( Byung Hyun Choi ),지미정 ( Mi Jung Ji ),정성헌 ( Sung Hun Jung ),김광범 ( Kwang Bum Kim ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.3

For preparing spinel Li_4Ti_5O_12 nanofiber, a hydrogen titanate nanofiber precursor was mixed with LiOH·H2O and then the mixture was treated at 130℃ in an autoclave for 24 hrs. The hydrogen titanate nanofiber precursor was made using a TiO2 and NaOH solution as the starting material. As a result, the diameter of the Li4Ti5O12 nanofiber was 5-10nm and the length was over 100 nm longer fiber. The oleic acid (C17H33COOH) coated Li4Ti5O12 nanofiber with different oleic acid contents (5, 7.5, and 10 wt%) was obtained by a simple mixing method and heat treatment at 450℃ in a N_2 atmosphere. The results clearly revealed that the surface of the Li4Ti5O12 nanofiber was coated with an amorphous carbon layer (1 nm). The crystallinity of the samples was also enhanced. The oleic acid coated Li_4Ti_5O_12 nanofiber (5 wt% and 7.5 wt%) displayed a much lower impedance than the Li_4Ti_5O_12 nanofiber because of the decreased charge transfer resistance, therefore, it had an improved discharging/charging capacity, c-rate and cycle performance.