• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1607-1610
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• 2009

The carbon-coated Si/Cu powder has been prepared by mechanical ball milling and hydrocarbon gas decomposition methods. The phase of Si/Cu powder was analyzed using X-ray diffraction (XRD), dispersive Raman spectroscopy, electron probe microanalysis (EPMA) and transmission electron microscope (TEM). The carbon-coated Si/Cu powders were used as anode active material for lithium-ion batteries. Their electrochemical properties were investigated by charge/discharge test using commercial LiCo$O_2$ cathode and lithium foil electrode, respectively. The surface phase of Si/Cu powders consisted of carbon phase like the carbon nanotubes (CNTs) with a spacing layer of 0.35 nm. The carbon-coated Si/Cu/graphite composite anode exhibited a higher capacity than commercial graphite anode. However, the cyclic efficiency and the capacity retention of the composite anode were lower compared with graphite anode as cycling proceeds. This effect may be attributed to some mass limitations in LiCo$O_2$ cathode materials during the cycling.

• 한국세라믹학회지
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• 제42권12호
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• pp.793-799
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• 2005

A composite cathode of LSCF$(La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3)\;and\;GDC\; (Gd_2O_3-doped\;CeO_2:Ce_{0.9}Gd_{0.1}O_{1.95_})$ was characterized in terms of an electrode response, using a point contact in an Yttria-Stabilized Zirconia (YSZ) electrolyte incorporated into AC two-point impedance spectroscopy. The point-contacted configuration amplifies the responses occurring near the YSZ/cathode interface through the aligned point contact on the planar LSCF/GDC electrode. The point contact interface increases the bulk resistance allowing the estimation of the point contact geometry and resolving the electrode-related responses. The resultant impedance spectra are analyzed through an equivalent circuit model constructed by resistors and constant phase elements. The bulk responses can be resolved from the electrode-related portions in terms of spreading resistance. The electrode-related polarizations are measured in terms of temperature and oxygen partial pressure. The modified impedance spectroscopy is discussed in terms of methodology and analytical aspects, toward resolving the electrode-polarization issues in solid oxide fuel cells.

• 한국세라믹학회지
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• 제53권5호
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• pp.489-493
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• 2016

Scandia ($Sc2O_3$)-stabilized zirconia (ScSZ) electrolyte-supported symmetrical solid oxide electrolyzer cells (SOECs), in which lanthanum strontium cobalt ferrite (LSCF)-gadolinia ($Gd_2O_3$)-doped ceria (GDC) composite materials are used as both the cathode and anode, were fabricated and their high temperature steam electrolysis (HTSE) performance was investigated. Current density-voltage curves were obtained for cells operated in 10% $H_2O$/90% Ar at 750, 800, and $850^{\circ}C$. It was possible to determine the ohmic, cathodic, and anodic contributions to the total overpotential using the three-electrode technique. The HTSE performance was significantly improved in the symmetrical cell with LSCF-GDC electrodes compared to the cell consisting of an Ni-YSZ cathode and LSCF-GDC anode. It was found that the overpotential due to the LSCF-GDC cathode largely decreased and, at a given current density, the total cell voltage decreased, which resulted in the enhanced hydrogen production rate in the symmetrical cell.

• Journal of Electrochemical Science and Technology
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• 제12권4호
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• pp.453-457
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• 2021

Lithium-sulfur (Li-S) batteries are one of attractive energy conversion and storage system based on high theoretical specific capacity and energy density with low costs. However, volatile nature of elemental sulfur is one of critical problem for their practical acceptance in industry because it considerably affects electrode uniformity during electrode manufacturing. In this work, polymeric sulfur composite consisting of ionic liquid (IL) are suggested to reduce volatility nature of elemental sulfur, resulting in better processibility of the Li-S cell. According to systematic spectroscopic analysis, it is found that polymeric sulfur is consisting of repeating units combining with elemental sulfur and volatility of them is negligible even at high temperature. In addition, the IL-embedded polymeric sulfur shows moderate cycle performance compared to the cell with elemental sulfur. From these results, it is found that the IL-embedded polymeric sulfur composite is applicable cathode candidate for the Li-S cell based on their excellent non-volatility as well as their superior electrochemical performance.

• 한국세라믹학회지
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• 제44권12호
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• pp.740-746
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• 2007

The potential candidates for IT-SOFCs cathode materials, $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ (BSCF) and $La_{0.6}Ba_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LBCF) powders, were synthesized by a EDTA-citrate combined method from $Sr(NO_3)_2$, $Ba(NO_3)_2$, $La(NO_3)_3{\cdot}6H_2O$, $Co(NO_3)_2{\cdot}6H_2O$, $Fe(NO_3)_3{\cdot}9H_2O$, citric acid and $EDTA-NH_3$. The cathode performance of symmetrical electrochemical cells consisting of BSCF-GDC or LBCF-GDC composite electrodes and a GDC electrolyte was investigated using by AC impedance spectroscopy at the temperature range of 500 to $700^{\circ}C$. It was found that a single phase perovskite could be successfully synthesized when the precursor is heated at $850^{\circ}C$ for 2 h. Due to thermal expansion mismatch between BSCF and GDC, the composite cathodes with lower GDC content than 45 wt% were peeled off from the GDC electrolyte and their electrode polarization resistance was estimated to be high. The thermal expansion coefficient of BSCF-GDC composites was decreased with increasing the GDC content and the electrode peeling off did not occur in BSCF-45 and 55 wt% GDC composites. BSCF-45 wt% GDC composite electrode showed the lowest area specific resistances (ASR) of 0.15 and $0.04{\Omega}{\cdot}cm^2$ at 600 and $700^{\circ}C$, respectively. On the other hand, LBCF-GDC composite cathodes showed higher ASR than the BSCF-45 and 55 wt% GDC and their cathode performance were decreased with the GDC content.

• 전기화학회지
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• 제14권3호
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• pp.176-183
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• 2011

본 연구에서는 Sr이 치환된 이중층 페로브스카이트($SmBa_{0.5}Sr_{0.5}Co_2O_{5+{\delta}}$, SBSCO)와 전해질 물질로 사용되는 $Ce_{0.9}Gd_{0.1}O_{2-{\delta}}$ (CGO91)을 기반으로 한 중 저온형 고체산화물 연료전지 (ITSOFC) 복합공기극의 분말 크기와 열 사이클에 대한 전기화학특성을 연구하였다. 복합공기극의 모체가 되는 SBSCO에 CGO91물질을 이용하여 면적비저항을 확인 한 결과 약 $0.54\sim9.04{\mu}m$의 분말 크기를 보이는 SBSCO와 $0.4\sim42{\mu}m$의 분말 크기를 보인 CGO91이 각각 50 wt%로 구성된 SBSCO : 50 복합공기극이 600 및 $700^{\circ}C$에서 약 0.102 및 $0.013{\Omega}cm^2$의 우수한 면적비 저항을 가지는 것을 확인 하였으며 상대적으로 분말 크기가 큰 CGO91 분말을 이용한 두 개의 공기극의 경우 $700^{\circ}C$에서 약 $0.260{\Omega}cm^2$와 $0.055{\Omega}cm^2$의 특성을 보여주었다. 10회에 걸친 열 사이클실험을 통하여 SBSCO : 50의 면적비저항은 $0.0193{\Omega}cm^2$에서 $0.094{\Omega}cm^2$로 증가하였으며 7회 이후의 면적비저항은 일정하게 유지됨을 확인하였다.

• Transactions on Electrical and Electronic Materials
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• 제13권4호
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• pp.177-180
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• 2012

In this study, we prepared $LiFePO_4$- poly (sodium 4-styrenesulfonate) (PSS) composite by the hydrothermal method and ball-milling process. Different wt% PSS were added to $LiFePO_4$. The cathode electrodes were made from mixtures of $LiFePO_4$-PSS: SP-270: PVDF in a weighting ratio of 70%: 25%: 5%. $LiFePO_4$-PSS powders were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). The electrochemical properties of $LiFePO_4$-PSS/Li batteries were analyzed by cyclic voltammetry, charge/discharge tests, and AC impedance spectroscopy. A Li/$LiFePO_4$-PSS battery with 4.75 wt% PSS shows the best electrochemical properties, with a discharge capacity of 128 mAh/g.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.61-64
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• 2007

Ni/YSZ ($Y_{2}O_{3}-stabilized$ $ZrO_{2}$), Cu/YSZ and CuO/YSZ composite powder for a cathode material in high temperature electrolysis (HTE) was synthesized by a mechanical alloying method with Ni (or Cu, CuO, Co) and YSZ powder. Microstructure of the composite for HTE reaction has been analyzed with various techniques of XRD, SEM to investigate effects of fabrication conditions. And conductivity of electrode was measured, Cu/YSZ cermet showed the higher electrical conductivity value than Ni/YSZ.

• 상하수도학회지
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• 제27권4호
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• pp.503-509
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• 2013

Electrochemical redox capacity of a microbial fuel cell (MFC) electrode is an important factor in the power density. This study was conducted to investigate the redox capacity of surface modified anode and cathode electrodes by measuring their conductivities. An anode electrode was modified with nitric acid and a cathode electrode was modified with heat treatment. The anode electrode modified with 20 % of the nitric acid concentration showed the highest conductivity of $6.2{\mu}S/cm/g$ and the maximum power density of $306.0mW/m^2$ when used in a MFC. The cathode electrode modified at $472^{\circ}C$ for 18 min showed the highest conductivity of $5.2{\mu}S/cm/g$ and the maximum power density of $276.20mW/m^2$ when used in a MFC. On the other hand, an MFC using both the electrodes showed the highest maximum power density of $408.2mW/m^2$. Meanwhile, a control MFC without modified electrodes generated very small voltage (0.014 mV), so the power density could not be measured.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.137.2-137.2
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• 2011

Poly (sodium 4-styrenesulfonate) (PSS) is ionomer based on polystyrene that is electrical conductivity and isoviscosity. LiFePO4 has been a promising electrode material however its poor conductivity limits practical application. To enhance the electronic conductivity of LiFePO4, in this study we prepared LiFePO4- PSS composite by the hydrothermal method. LiFePO4 was heated at $170^{\circ}C$ for 12h and then different wt% PSS (0%, 2.91%, 4.75%, 7.36%, 10%) are added to LiFePO4 and milled at 300rpm for 10h. And then the obtained powders were subsequently heated at $500^{\circ}C$ for 1h under argon flow. The cathode electrode were made from mixtures of LiFePO4-PSS: SP-270- PVDF in a weighting ratio 75%: 25%:5%. The electrochemical properties of LiFePO4- PSS/Li batteries were analyzed by cyclic voltammetry and charge/discharge tests. LiFePO4-C/Li battery with 4.75 wt% PSS displays discharge capacity of 128 mAh g-1 at room temperature that is considerably higher than pure LiFePO4/Li battery ( 113.48 mAhg-1).