• Journal of the Korean Electrochemical Society
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• v.9 no.1
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• pp.34-39
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• 2006

Electrochemical properties of Cu foil current collector with a $Li_{0.5}La_{0.5}TiO_3$ Cu a Si thin film deposited by r.f sputtering as an anode for Li free battery were evaluated. The Cu foil current collectors were lied in and out of plasma during sputtering process. The X-ray diffraction results indicated that the as-deposited Si and $Li_{0.5}La_{0.5}TiO_3$ thin films in and out of plasma did not show any crystalline difference. The $Li_{0.5}La_{0.5}TiO_3$ film in plasma and Si film out of plasma showed better cyclability since crystalline $Li_{0.5}La_{0.5}TiO_3$ has much higher ionic conductivity and crystalline Si film is much sensitive far volume change during charge-discharge process. These results suggested that the deposition of amorphous Si on Cu foil current collector is much better for fabrication of Li free battery and it can be useful for the unique battery with a cycling number constraint of below 10.

• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.219-223
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• 2000

All-solid state lithium rechargeable thin film batteries were fabricated with the configuration of$Cu_{0.5}V_2O_5/Lipon/Li$ using sequential thin film techniques. Copper vanadium oxide thin films and Lipon thin films were prepared by DC reactive dual source magnetron sputtering and RF magnetron sputtering, respectively. According to XRD analysis, we found out that copper vanadium oxide thin films were amorphous. The electrochemical behaviour of them was examined in half cell system using EC : DMC(1:1 in IM $LiPF_5$) liquid electrolyte. The ionic conductivity of Lipon thin film was $1.02\times10^{-6}S/cm$ at $25^{\circ}C$ and $Cu_{0.5}V_2O_5/Lipon/Li$ cell showed that the discharge capacity was about $50{\mu}Ah/cm^2{\mu}m$ beyond 500cyc1es.

• Journal of the Korean Ceramic Society
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• v.41 no.3
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• pp.229-234
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• 2004

In this study, we proposed new forming process for a porous ceramic body with unique pore structure. h tubular-type porous NiO-YSZ body with radially aligned pore channels was prepared by freeze-drying of aqueous slurry. A NiO-YSZ slurry was poured into the mold, which was designed to control the crystallization direction of the ice, followed by freezing. Thereafter the ice was sublimated at a reduced pressure. SEM observations revealed that the NiO-YSZ porous body showed aligned large pore channels parallel to the ice growth direction, and fine pores are formed around the outer surface of the tube. It was considered that the difference in the ice growth rate during the freezing process resulted in such a characteristic microstructure. Bilayer consisting of dense thin electrolyte film of YSZ onto the tubular type porous body has been successfully fabricated using a slurry-coating process followed by co-firing. It was regarded that the obtained bilayer structure is suitable for constructing electrode-support type electrochemical devices such as solid oxide fuel cells.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.127.1-127.1
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• 2010

고체산화물연료전지는 고효율 및 무공해의 전기화학 에너지 변환장치로서, 최근 국내외에서 활발한 연구개발이 수행되고 있다. 특히, 고체산화물 연료전지 시스템의 조기 상용화를 위해 시스템의 작동온도를 약 $800^{\circ}C$ 이하로 낮추고 저가로 생산 할 수 있는 제조공정 개발에 대한 연구를 적극적으로 수행하고 있다. 본 연구에서는 고체산화물연료전지의 단위셀를 구성하는 연료극지지체 및 박막 전해질에 대해서 저가 양산의 테이프케스팅법 및 동시소성 공정, 그리고 연료극 지지체 전해질(anode-supported electrolyte)에 대한 공기극 페이스트 프린팅 제조공정에 대해 소개한다. 또한 고체산 화물연료전지의 제조공정 및 시간을 단축하기 위해 방전플라즈마 소결공법(SPS)에 의한 연료극 지지체 제조 공정, 단위셀의 성능 최적화를 위한 나노 스케일의 고성능 전해질 소재 분말합성 공정(crystallite size: 5~10nm, surface area : $100m^2/g$ 이상) 그리고 테이프케스팅에 의한 박막 전해질 제조 공정(thin film : $10{\mu}m$ 이하) 등 주요 단위셀 소재 및 부품의 제조공정 특성 그리고 단위셀의 전기화학적 특성(max. power density : 1.0 W/$cm^2$)에 대해 소개하며, 최종적으로 평판형 대면적 고체산화물연료전지(max. $20cm{\times}15cm$)의 단위셀 상용화 제조 기술 및 성능평가 기술에 대해서도 소개 할 예정이다.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1414-1417
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• 1996

The purpose of this study Is to research and develop $V_{6}O_{13}$ composite cathode for lithium thin film battery. $V_{6}O_{13}$ represents a class of cathode active material used in Li rechargeable batteries. In this study, we investigated cyclic voltammetry and charge/discharge characteristics of $V_6O_{13}$/SPE/Li cells. Cyclic voltammogram of $V_{6}O_{13}$/SPE/Li cell at scan rate 1mV/sec showed reduction peaks of 2.25V and 2.4V and oxidation peaks of 2.4V and 2.2V. The discharge curve of $V_{6}O_{13}$/SPE/Li cell showed 4 potential plateaus. The discharge capacity was decreased in the beginning of charge/discharge cycling. After 8th cycling, the discharge capacity was stable. The discharge capacity of 1st cycle and 15th cycle was 290mAh/g and 147mAh/g at $25^{\circ}C$, respectively.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.202-208
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• 1999

Composite cathodes of $50/50\;vol\%$ LSM-YSZ $(La_{-x}Sr_xMnO_3-yttria\;stabilized\;zirconia)$ were deposited onto dense YSZ electrolytes by colloidal deposition technique. The cathode characteristics were then examined by scanning electron microscopy (SEM) and studied by ac-impedance spectroscopy (IS). The conditioning effects on LSM-YSZ cathodes were seen and remedies for these effects were noted in order to improve the performance of a solid oxide fuel cell (SOFC). The effects of temperature on impedance, surface contamination on cathode bonding to YSZ electrolyte, changing Pt paste, aerosol spray technique applied to curved surface on microstructure and cell to cell variability were solved by testing at $900^{\circ}C$, sanding the YSZ surface, using only one batch of Pt paste, using flat YSZ plates and using consistent procedures and techniques, respectively. And then, reproducible impedance spectra were confirmed by using the improved cell and the typical spectra measured for an (air)LSM-YSZ/YSZ/LSM-YSZ(air) cell at $900^{\circ}C$ were composed of two depressed arcs. Impedance characteristics of the LSM-YSZ cathodes were also affected by experimental conditions such as catalytic interlayer, composite cathode compositions and applied current.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.562-566
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• 2012

A novel design of tubular segmented-in-series(SIS) solid oxide fuel cell (SOFC) sub module was presented in this paper. The tubular ceramic support was fabricated by the extrusion technique. The NiO-YSZ anode and the yttria-stabilized zirconia (YSZ) electrolyte were deposited onto the ceramic support by dip coating method. After sintering at $1350^{\circ}C$ for 5 h, a dense and crack-free YSZ film was successfully fabricated. Also, the multi-layered cathode composed of LSM-YSZ composite, LSM and LSCF were coated onto the sintered ceramic support by dip coating method and sintered at $1150^{\circ}C$. The performance of the tubular SIS SOFC cell and sub module electrically connected by the Ag-glass interconnect was measured and analysed with different fuel flow and operating temperature.

• Journal of the Korean Electrochemical Society
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• v.4 no.2
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• pp.58-64
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• 2001

YSZ ($8mol\%$ yttria-stabilized zirconia)-modified LSM $(La_{0.85}Sr_{0.15}MnO_3)$ composite cathodes were fabricated by formation of YSZ film on triple phase boundary (TPB) of LSM/YSZ/gas. The YSZ coating film greatly enlarged electrochemical reaction sites from the increase of additional TPB. The composite cathode was formed on thin YSZ electrolyte (about 30 Um thickness) supported on an anode and then I-V characterization and AC impedance analyses were performed at temperature between $700^{\circ}C\;and\;800^{\circ}C$. As results of the impedance analysis on the cell at $800^{\circ}C$ with humidified hydrogen as the fuel and air as the oxidant, R1 around the frequency of 1000 Hz represents the anode Polarization. R2 around the frequency of 100Hz indicates the cathode polarization, and R3 below the frequency of 10 Hz is the resistance of gas phase diffusion through the anode. The cell with the composite cathode produced power density of $0.55\;W/cm^2\;and\;1W/cm^2$ at air and oxygen atmosphere, respectively. The I-V curve could be divided into two parts showing distinctive behavior. At low current density region (part I) the performance decreased steeply and at high current density region (part II) the performance decreased gradually. At the part I the performance decrease was especially resulted from the large cathode polarization, while at the part H the performance decrease related to the electrolyte polarization.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.64.1-64.1
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• 2010

The morphology of mesoporous $TiO_2$ films plays an important role in the operation of a DSSC. For example, the energy conversion efficiency of DSSCs with well-organized mesoporous $TiO_2$ films is much higher than those with traditional films possessing a random morphology. In previous research, well-organized mesoporous $TiO_2$ films have mainly been synthesized using an amphiphilic block copolymer, e.g., a poly(ethylene oxide) (PEO)-based template. A graft copolymer is more attractive than a block copolymer due to its low cost and the ease with which it can be synthesized. In this work, we provide the first report on the successful synthesis of well-organized mesoporous $TiO_2$ films templated by an organized graft copolymer as a structure directing agent. Well-organized mesoporous $TiO_2$ films with excellent channel connectivities were developed via the sol gel processusing an organized PVC-g-POEM graft copolymer synthesized by one-pot ATRP. The careful adjustment of copolymer composition and solvent affinity using a THF/$H_2O$/HCl mixture was used to systematically vary the material structure. The influence of the material structure on solar cell performance was then investigated. A solid-state DSSC employing both the graft copolymer templated organized 700 nm-thick $TiO_2$ films and graft copolymer electrolytes exhibited a solar conversion efficiency of 2.2% at 100 $mW/cm^2$. This value was approximately two-fold higher than that attained from a DSSC employing a random mesoporous $TiO_2$ film. The solar cell performance was maximized at 4.6% when the film thickness was increased to $2.5{\mu}m$. We believe that this graft copolymer-directed approach introduces a new and simple route toward the synthesis of well-organized metal oxide films as an alternative to a conventional block copolymer-based template.

• Journal of the Korean Electrochemical Society
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• v.20 no.1
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• pp.7-12
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• 2017

Using a precursor of $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ as a starting material, a surface-modified cathode material was obtained by coating with KCl, where the added KCl reduces residual Li compounds such as $Li_2CO_3$ and LiOH, on the surface. The resulting electrochemical properties were investigated. The amounts of $Li_2CO_3$ and LiOH decreased from 8,464 ppm to 1,639 ppm and from 8,088 ppm to 6,287 ppm, respectively, with 1 wt% KCl added $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ that had been calcined at $800^{\circ}C$. X-ray diffraction results revealed that 1 wt% of KCl added $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ did not affect the parent structure but enhanced the development of hexagonal crystallites. Additionally, the charge transfer resistance ($R_{ct}$) decreased dramatically from $225{\Omega}$ to $99{\Omega}$, and the discharge capacity increased to 182.73mAh/g. Using atomic force microscopy, we observed that the surface area decreased by half because of the exothermic heat released by the Li residues. The reduced surface area protects the cathode material from reacting with the electrolyte and hinders the development of a solid electrolyte interphase (SEI) film on the surface of the oxide particles. Finally, we found that the introduction of KCl into $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ is a very effective method of enhancing the electrochemical properties of this active material by reducing the residual Li. To the best of our knowledge, this report is the first to demonstrate this phenomenon.