• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1125-1131
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• 1996

Ca or Sr-doped $PrMnO_3$ were prepared for cathode material of solid oxide fuel cell. The characteristics such as the electrical conductivity and the cathodic overpotential were investigated as to doping contents. Also the reactivity with yttria stabilized zirconia of electrolyte, and the thermal expansion coefficient were studied. The prepared perovskite powder had the mean particle size of $2{\sim}5{\mu}m$, and the particle size and the surface area was out of relation to the doping content. When Ca doping amount of electrode material was 30mol%, the electrical conductivity was the highest value of $266S{\cdot}cm^{-1}$ at $1000^{\circ}C$, and also the polarization characteristics showed the best property. The reactivity between YSZ and Ca-doped $PrMnO_3$ at $1200^{\circ}C$ for 100hours was lower than that between YSZ and Sr-doped $PrMnO_3$. The thermal expansion coefficient of $Pr_{0.7}Ca_{0.3}MnO_3$ was $1.19{\times}10^{-5}K^{-1}$ in the temperature range of $300{\sim}1000^{\circ}C$, and this value was similar to that of YSZ, $1.15{\times}10^{-5}K^{-1}$.

• Journal of the Korean Electrochemical Society
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• v.19 no.2
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• pp.50-56
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• 2016

Spherical lithium manganese oxide spinel, $Li_{1.10}Mn_{1.86}Al_{0.02}Mg_{0.02}O_4$ was prepared by wet-milling, spray-drying, and sintering process. In the spray-drying process, solid content in slurry was varied from 20 to 30 wt%. In the sintering process, the precursors have been sintered under air or $O_2$ atmosphere. While the as-prepared samples exhibit excellent electrochemical properties at room temperature, the discharge voltage profiles at 5.0C are very different one from another. The origin for the difference especially at initial state of discharge is oxygen defect. The sample prepared in air has larger capacity related to the plateau at 3.3 V (vs. $Li/Li^+$) which is caused by the oxygen defects than the one prepared in $O_2$. The difference of discharge voltage profiles especially at the final state of discharge comes from different diffusion rate of $Li^+$ ions. The sample prepared from 30 wt% solid content of slurry shows twice higher diffusion rate than the samples prepared from 20 wt% solid content, which is attributed to better compactness between primary particles for the sample prepared from 30wt % solid content than the one prepared by 20 wt%.

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.205-210
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• 2011

Structural and electrochemical properties of spinel oxide $LiMn_2O_4$ thin films prepared by using a sol-gel method on Pt/Ti/$SiO_2$/Si substrates were investigated. When Li/Mn molar ratio of the film was smaller than 0.5, $Mn_2O_3$hase was found to coexist with $LiMn_2O_4$. Half-cell batteries fabricated using the $LiMn_2O_4$ films as the cathode were put into chargedischarge (C-D) cycles and the change in structural properties of the cathode after the cycles was examined by X-ray diffraction and Raman spectroscopy. As the C-D cycle number increases, the discharge capacity of pure $LiMn_2O_4$ battery gradually decreases, being reduced to 72% of the initial capacity at 300 cycles. Such capacity fading is attributable to the decrease in the number of $Li^+$ ions that return to the tetrahedral sites of the spinel structure during the discharge step and the resultant increase in $Mn^{4+}$ density in the film. Also, $Mn_2O_3$ phase gradually appeared in the film as the cycle number increases.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.126-132
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• 2022

Alkaline fuel cells using liquid fuels such as hydrazine and ammonia are gaining great attention as a clean and renewable energy solution possibly owing to advantages such as excellent energy density, simple structure, compact size in fuel container, and ease of storage and transportation. However, common shortcomings including cathode flooding, fuel crossover, side yield reactions, and fuel security and toxicity are still challenging issues. Real time monitoring of fuel concentrations integrated into a fuel cell device can help improving fuel cell performance via predicting any loss of fuels used at a cathode for efficient energy production. There have been extensive research efforts made on developing real-time sensing platforms for hydrazine and ammonia. Among these, recent advancements in electrochemical sensors offering high sensitivity and selectivity, easy fabrication, and fast monitoring capability for analysis of hydrazine and ammonia concentrations will be introduced. In particular, research trend on the integration of metallic and metal oxide nanoparticles and also their hybrids with carbon-based nanomaterials into electrochemical sensing platforms for improvement in sensitivity and selectivity will be highlighted.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.101-106
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• 2016

In this study, we prepared an ionic liquid composite solid polymer electrolyte (PEO-LiTFSI-$Pyr_{14}TFSI$) with poly(ethylen oxide), lithium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide by blending-cross linking process. Although the PEO-LiTFSI-$Pyr_{14}TFSI$ composite solid polymer electrolyte displayed a small peak at 4.4 V, it had high electrochemical oxidation stability up to 5.7 V. Ionic conductivity of the PEO-LiTFSI-$Pyr_{14}TFSI$ composite solid polymer electrolyte increased with increasing temperature from $10^{-6}S\;cm^{-1}$ at $30^{\circ}C$ to $10^{-4}S\;cm^{-1}$ at $70^{\circ}C$. To investigate the electrochemical properties, the PEO-LiTFSI-$Pyr_{14}TFSI$ composite solid polymer electrolyte assembled with $LiFePO_4$ cathode and Li-metal anode. At 0.1 C-rate, the cell delivered $40mAh\;g^{-1}$ for $30^{\circ}C$, $69.8mAh\;g^{-1}$ for $40^{\circ}C$ and $113mAh\;g^{-1}$ for $50^{\circ}C$, respectively. The PEO-LiTFSI-$Pyr_{14}TFSI$ solid polymer electrolyte exhibited good charge-discharge performance in Li/SPE/$LiFePO_4$ cells at $50^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.44-48
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• 2000

Amorphous $V_2O_5$ cathode thin films were prepared by DC-magnetron sputtering at room temperature and the thin film rechargeable lithium batteries were fabricated with the configuration of $V_2O_5/LIPON/Li$ using sequential ex-situ thin film deposition techniques. The electrochemical characteristics of $V_2O_5$ cathode materials Prepared at 80/20 of $Ar/O_2$ ratio showed high capacity and cycling behaviors by half cell test. LIPON solid electrolytes films were prepared by RF-magnetron sputtering using the self-made $Li_3PO_4$ target in pure $N_2$ atmosphere, and it was very stable for lithium contact in the range of 1.2-4.0 V vs. Li. Metallic lithium were deposited on LIPON electrolyte by thermal evaporation methode in dry room. Vanadium oxide based full cell system showed the initial discharge capacity of $150{\mu}A/cm^2{\mu}m$ in the range of $1.2\~3.5V$.

• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.109-114
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• 2012

The cathode catalyst layer in polymer electrolyte membrane fuel cells (PEMFCs) was fabricated with anodic aluminum oxide (AAO) template and its structure was characterized with scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. The SEM analysis showed that the catalyst layer was fabricated the Pt nanowire with uniform shape and size. The BET analysis showed that the volume of pores in range of 20-100 nm was enhanced by AAO template. The electrochemical properties with the membrane electrode assembly (MEA) were evaluated by current-voltage polarization measurements and electrochemical impedance spectroscopy. The results showed that the MEA with AAO template reduced the mass transfer resistance and improved the cell performance by approximately 25% through controlling the structure of catalyst layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.79-84
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• 1993

This paper describes the development of lithium rechargeable cell. $LiCoO_2$ is recently recognized as a suitable cathode active material of a high voltage, high energy lithium rechargeable batteries because $Li^+$ ion can be electrochemically deintercalated/intercalated from/to $Li_xCoO_2$. The transition metal oxide of $LiCoO_2$ was investigated for using as a cathode active material of 4V class Li rechargeable cell. $LiCoO_2$ cathode was prepared by using a active material of 85 wt%, graphite powder of 12 wt% as a conductor and poly-vinylidene fluoride of 3 wt% as a binder. The electrochemical and charge/discharge properties of $LiCoO_2$ were investigated by cyclic voltammetry and galvanostatic charge/discharge. The open circuit voltage of prepared $LiCoO_2$ electrode exhibited approximately. potential range between 3.32V and 3.42V. During the galvanostatic charge/discharge, $LiCoO_2/Li$ cell showed stable cycling behavior at scan rate of 1mV/sec and potential range between 3.6V and 4.2V. Also its coulombic efficiency as function of cycling was 81%~102%. In this study the $LiCoO_2/Li$ cell showed the available discharge capacity of 90.1 mAh/g at current density of $1mA/cm^2$ and cell discharge voltage range between 3.6V~4.2V.

• Ceramist
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• v.21 no.4
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• pp.378-387
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• 2018

The optimal fabrication conditions for $Gd_{0.1}Ce_{0.9}O_{2-{\delta}}$(GDC) buffer layer and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LSCF) cathode on 1mol% $CeO_2-10mol%\;Sc_2O_3$ stabilized $ZrO_2$ (CeScSZ) electrolyte were investigated for application of IT-SOFCs. GDC buffer layer was used in order to prevent undesired chemical reactions between LSCF and CeScSZ. These experiments were carried out with $5{\times}5cm^2$ anode supported unit cells to investigate the tendencies of electrochemical performance, Microstructure development and interface reaction between LSCF/GDC/CeScSZ along with the variations of GDC buffer layer thickness, sintering temperatures of GDC and LSCF were checked, respectively. Electrochemical performance was analyzed by DC current-voltage measurement and AC impedance spectroscopy. Microstructure and interface reaction were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Although the interfacial reaction between these materials could not be perfectly inhibited, We found that the cell, in which $6{\mu}m$ GDC interlayer sintered at $1200^{\circ}C$ and LSCF sintered at $1000^{\circ}C$ were applied, showed good interfacial adhesions and effective suppression of Sr, thereby resulting in fairly good performance with power density of $0.71W/cm^2$ at $800^{\circ}C$ and 0.7V.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1107-1115
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• 2009

The strengthened regulations for atmospheric emissions from ships like MARPOL Annex VI have caused a necessity of new, alternative power system in ships for the low pollutant emissions and the high energy efficiency. This paper attempts to investigate the configuration of SOFC/GT hybrid power system for marine applications like LNG tanker and to analyze the influence of design parameters on the system performance. The simulation results provide the basic data for the design and efficiency improvement of SOFC/GT hybrid system and indicate the guidelines for the safe system operation.