• Journal of the Korean Magnetic Resonance Society
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• v.3 no.2
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• pp.90-99
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• 1999

Doping of boron atoms in graphite has been well known method to increase the discharge capacity as the negative electrode material for lithium secondary battery. Herein, the boron-doped graphites are prepared by mixing 1, 2.5, 5, and 7 wt. % of boron carbide in carbon during the graphitizing process. The structural states of boron in boron-doped graphites are investigated by solid-state 11B NMR spectroscopy. The resonance lines for substitutional boron atoms are identified as the second order quadrupolar powder pattern with the quardrupole coupling constant, QCC = 3.36(2) MHz. The quantitative analysis of 11B NMR spectra with boron-doped graphite has also been performed via simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.159-162
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• 1998

The new type polymer electrolyte composed of polyacrylonitrile(PAN) baed polymer electrolyte contain LiClO$_4$-EC/PC and LiPF$\sub$6/-EC/PC were developed for the weightless and long or life time of lithium polymer battery system with using polyaniline electrode. The gel type electrolytes were prepared by PAN at different lithium salts in the glove box. We prepared for polymer electrolyte with knife casting method. The minimum thickness of PAN gel electrolyte for the slim type is about <400∼500$\mu\textrm{m}$. These gel electrolytes showed good compatibility with lithium electrode. The test cell of Li/polymer electrolyte/Lithium cobalt oxide solid state cell which was prepared by different lithium salt was researched by electrochemical technique. Resistance of polymer electrolyte which consist of LiClO$_4$ is more less than that of LiPF$\sub$6/ and cycle life is more longer than that of LiPF$\sub$6/.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.50-55
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• 1999

We have investigated the $LiMn_2O_4$system as an cathode material for lithium rechargeable batteries. $LiMn_2O_4$spinel oxides have been synthesized by a solid state methode. We varied sintering time at a fixed sintering temperature of 75$0^{\circ}C$. In order to investigate the electrochemical properties of prepared $LiMn_2O_4$we assembled three-electrode cells using the working electrode as active material and Li metal as the counter and reference electrodes. The electrolyte was 1 M LiPE$_{6}$-EC:DEC(1:1 by volume). The particle size of sample synthesized at 75$0^{\circ}C$ ranged about 60$\mu m$. The discharge capacity of a cell involving spinel $LiMn_2O_4$ increased with increasing sintering time.e.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.972-976
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• 1997

Single phase ruthenium oxides with perovskite (ATi1-xRuxO3 (A=Ca, Sr)) and pyrochlore structure (Bi2Ru2O7, Pb2Ru2O6.5) have been prepared reproducibly by solid state reaction methods and their electrocatalytic activities for oxygen evolution have been examined by Tafel plots. Tafel slopes vary from a low value of 42 mV/decade up to 222 mV/decade at room temperature. The high exchange current densities and high Tafel slopes compared with those obtained from the RuO2 DSA electrode at the crystalline single phase metal oxide electrodes suggest that they are better electrocatalysts at low overpotentials. A favorable change in the Tafel slope for the oxygen evolution reaction occurs as the ruthenium content increases. Substitution of Ti for Ru in the perovskite solid solutions enhanced their chemical stability by losing marginal electrochemical activity.

• Journal of the Korean Chemical Society
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• v.41 no.12
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• pp.653-660
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• 1997

Silicone rubber-matrix membranes doped with tetradecyltrimethylammonium chloride (TDTMACl) are used to enhance electrode performance for chloride measurements in physiological samples. The optimized membrane formulation incorporates 95.4 wt% silicone rubber and 4.6 wt% TDTMACl, and its pH response is negligible in the range of pH 6-10. The TDTMACl-doped silicone rubber membrane exhibits sub-Nernstian response to chloride from 10 to 300 mM (-37.5 mV/decade), but its selectivities for chloride over other anions are remarkably enhanced: KpotCl,NO3=1.3, KpotCl,I=2.0, KpotCl,Sal=0.8, KpotCl,SCN=2.0 and KpotCl,ClO4=0.8. Furthermore, since the silicone rubber-matrix membrane exhibits better adhesion to the solid surface than do PVC membranes, the lifetime of the coated-wire type membrane electrode is greatly improved. The response properties toward chloride and salicylate for solid-state sensor are not significantly changed after at least 35 days of use.

• Journal of the Korean Society of Safety
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• v.28 no.5
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• pp.5-9
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• 2013

Recently, eco-friendly sources of energy by fuel cells that use hydrogen as an energy source has emerged as the next generation of energy to solve the problem of environmental issues and exhaustion of energy. A solid oxide fuel cell(SOFC) classified based on the type of ion transfer mediator electrolyte has actively being researched. However, the reliability according to the thermal cycle is low during the operation of the fuel cell, and deformation problem comes from the difference in thermal expansion coefficient between the electrode material, the components made of ceramic material is also brittle, which means disadvantages in terms of the strength. Therefore, in this study, considering the states of the manufacturing and operating of SOFC single cells, the stress analyses in the each of the interfacial layer between the anode, electrolyte and the cathode were performed to get the basic data for reliability assessment of SOFC. The obtained results show that von Mises stress according to the thickness direction on operating state occurred maximum stress value in the electrolyte layer. And also the stresses inside the active area on a distance of 1 ${\mu}m$ from the electrode interface were estimated. Futhermore the evaluation was done for the variation of the stress according to the stage of the operation divided into three stages of manufacturing, stack, and operating.

• 한국전기화학회:학술대회논문집
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• 2003.11a
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• pp.141-151
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• 2003

The electrochemical activity of the olivine type $LiMPO_4$ (M=transition metals) cathodes strongly depends on various factors, e.g., the transition metal element M, perturbative doping of the supervalent cations into Li site, composite formation with conductive additives, state of charge/discharge, and particle size and its geometries, etc. This is, therefore, an important issue of interdisciplinary between electrochemistry and solid state science towards practical applications. In order to shed light on this interesting but complicated issue with the transport properties and crystallographic aspects, systematic discussion will be made with the review of our recent publications; (1) first principle derivation of the electronic structures, (2) crystallographic mapping of the selected solid solutions, (3) quantitative elucidation of the electron-lattice interaction, (4) spectroscopic detection of the local environment with Mossbauer and EXAFS, (5) synthetic optimization of the electrode composite, and (6) electrochemical evaluation of the reaction kinetics, particularly on M = Fe, Mn.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.920-923
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• 2000

All solid-state thin film supercapacitor(TFSC) based on $RuO_2$ electrode was fabricated. Ruthenium oxide$(RuO_2)$ thin film was deposited on Pt/Ti/Si subsrate by d.c. magnetron sputtering. LiPON(lithium phosphorus oxynitride) thin film were deposited by r.f. reactive sputtering. X-ray diffraction patterns of $RuO_2$ and LiPON films revealed that crystal structures of both films were amorphous. To decrease resistivity of $RuO_2$ thin film, $RuO_2$ thin film was deposited with $H_2O$ vapor. In order to decide the maximum ionic conductivity, the LiPON films were prepared by various sputtering condition. The maximum ionic conductivity was $9.5\times{10}^7S/cm$. A charge-discharge measurements showed the capacity of $3\times{10-2}\;F/cm^2-\mu{m}$ for the as-fabricated TFSC. The discharging efficiency was decreased after 500 cycles by 40 %.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.379-383
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• 2011

This paper presents the synthesis of one-dimensional spinel $LiMn_2O_4$ nanostructures using a facile and scalable two-step process. $LiMn_2O_4$ nanorods with average diameter of 100 nm and length of 1.5 ${\mu}m$ have been prepared by solid-state lithiation of hydrothermally synthesized ${\beta}$-$MnO_2$ nanorods. $LiMn_2O_4$ nanowires with diameter of 10 nm and length of several micrometers have been fabricated via solid-state lithiation of ${\beta}$-$MnO_2$ nanowires. The precursors have been lithiated with LiOH and reaction temperature and pressure have been controlled. The complete structural transformation to cubic phase and the maintenance of 1-D nanostructure morphology have been evaluated by XRD, SEM, and TEM analysis. The size distribution of the spinel $LiMn_2O_4$ nanorods/wires has been similar to the $MnO_2$ precursors. By control of reaction pressure, cubic 1-D spinel $LiMn_2O_4$ nanostructures have been fabricated from tetragonal $MnO_2$ precursors even below $500^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.5 no.4
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• pp.221-225
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• 2002

Assisted by the highly sensitive confocal microprobe Raman spectrometer and proper surface roughening procedure, the Raman investigation on the adsorption and reaction of methanol was performed on Pt-Ru electrodes with different coverages. A detailed description of the roughening process of the Pt electrodes and the underpotential deposition of the Ru was given. Reasonably good Raman signal reflecting the metal-carbon vibration and CO vibration was detected. The appearance of vibrations of the Ru oxides, together with the existence of Ru-C, Pt-C and CO bands, clearly demonstrates the participation of the bi-functional mechanism during the oxidation process of methanol on Pt-Ru electrodes. The Pt-Ru electrode was found to have a higher catalytic activity over Pt electrodes. This preliminary study shows that electrochemical Raman spectroscopy can be applied to the study of rough electrode surface.