• Korean Journal of Crystallography
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• v.15 no.1
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• pp.44-50
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• 2004

Spinel structured lithium managanese oxide $(LiMn_2O_4)$ powder with well defined facetted morphology was prepared by precipitation-evaporation method. {111}, {110}, and {100} planes are mainly observed in the $LiMn_2O_4$ powder. And powder shape of tetradecahedron and octahedron was observed depending on the calcinations temperature. The observed powder morphology observed seemed to be related to the nonstoichiometry of the oxygen in the $LiMn_2O_4$ spinel structure. Oxygen nonstoichiometry might be responsible for the Jahn-teller effect and structure transition which in turn affects the surface energy of the {111}, {110}, and {100} planes. Powder shape transition from tetradecahedron to octahedron seemed to be related to the surface energy of the {111}, {110}, and {100} planes with oxygen nonstoichiometry.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.564-568
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• 2000

Spinel LiMn2O4 catalyst with submicron and single phase particles was synthesized at 48$0^{\circ}C$ for 12 hr in air by a sol-gel method. The spinel LiMn2O4 was deoxidized by hydrogen at various temperatures. Effects of physiochemical properties of the catalyst reduced by hydrogen were examined with X-ray diffractometer, thermogravimetric analysis and scanning electron microscope. The decomposition rate of carbon dioxide was measrued using the catalyst deosidized at 35$0^{\circ}C$.

• Journal of Magnetics
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• v.6 no.3
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• pp.77-79
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• 2001

The semi-empirical superposition model has been applied to calculate the zero field splitting parameters of $Mn^{2+}$ion in $LiTaO_3$ single crystal, assuming that $Mn^{2+}$ion occupies one of two possible sites: $Li^{l+} \;or\; Ta^{5+}$ site, respectively. The 2nd-order axial zero field splitting parameters are $958\times10^{-4}cm^{-1}\; at\; Li^{1+}$ site and $193\times 10^{-4}cm^{-1} \;at\; Ta^{5+}$ site for $Mn^{2+}$ions. The 4th-order zero field splitting parameters at $Li^{l+} \;and\; Ta^{5+}$ sites are also determined. These calculated zero field splitting parameters are very important to determine the substitutional sites of doped impurity ions in $LiTaO_3$ crystal.

• Korean Chemical Engineering Research
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• v.45 no.2
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• pp.178-182
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• 2007

Non-aqueous supercapacitors by using activated C and $LiMn_2O_4$ as an active material in a positive electrode were prepared and characterized. From the cyclic voltammetry and AC impedance analysis, the capacitive effect by electric double layer of activated carbon and the faradic effect by intercalation/deintercalation of $Li^+$ ion were observed. Increasing the ratio of $LiMn_2O_4$, specific capacitances and energy densities of supercapacitor were increased. At the ratio of 0.86:0.14 ($LiMn_2O_4:C$), the maximum specific capacitance of 17.51 Wh/L and energy density of 23.83 F/cc were obtained, which were more than twice of those for a conventional electric double layer capacitor. Even after 1,000 charge/discharge cycle, the supercapacitor by using the electrode containing 14% of activated carbon and 86% of $LiMn_2O_4$ showed 60% better specific capacitance and energy density than that by using the electrode containing 100% activated carbon.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.175-178
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• 1998

LiMn$_2$O$_4$-based spinels has been studied extensively as positive electrode materials for rechargeable lithium and lithium ion batteries. We describe here that LiMn$_2$O$_4$ cathode active materials is preparated by sol-gel process using water as solvent, which often yields inorganic oxides of excellent phase purity and well-controlled stoichiometry. Using this process, it has been possible to synthesize phase-pure crystalline spinel LiMn$_2$O$_4$ by calcining the appropriate precursors in air at 80$0^{\circ}C$ for several hours. The influence of different time have also been explored. LiMn$_2$O$_4$ preparated in the present study exhibit the single phase of cubic and active reaction at 400 ~ $600^{\circ}C$. Electrochemical studies show that the this method- synthesized materials appear to present reversible oxidation and reduction reactions at 3.0V ~ 4.5V and cycle stability during 50 cycle.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.894-900
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• 2001

The spinel $Li{Mn_2}{O_4}$ catalysts for $CO_2$ decomposition were synthesized by a sol-gel method using manganese acetate and lithium hydroxide as starting materials through drying at $150^{\circ}C$ for 12 hrs under oxygen atmosphere followed by heat treatment at $480^{\circ}C$ for 12 hrs. The synthesized $Li{Mn_2}{O_4}$ were reduced by hydrogen for 3 hrs at various temperatures and the decomposition rate of carbon dioxide was investigated at 300, 325, 350, 375 and $400^{\circ}C$ using the $Li{Mn_2}{O_4}$ reduced by hydrogen gases. As a result of experiment, the optimum temperature of hydrogen reduction and $CO_2$ decomposition was shown $350^{\circ}C$. The physicochemical properties of the spinel $Li{Mn_2}{O_4}$ the reduced $Li{Mn_2}{O_4}$ and the $Li{Mn_2}{O_4}$ after $CO_2$ decomposition were examined with XRD, SEM and TGA.

• Journal of Electrochemical Science and Technology
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• v.1 no.2
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• pp.97-101
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• 2010

In order to apply hybrid capacitor, $Li_2Mn_3O_7$ was synthesized by combustion method using $LiNO_3$, $Li(CH_3COO){\cdot}2H_2O$ and $Mn(CH_3COO){\cdot}4H_2O$. Spinel pattern was identified the samples calcined over $400^{\circ}C$ in XRD. Intensity of $Mn_2O_3$ peak increased as the calcination temperature increased. To decide n/p ratio and to investigate electrochemical properties, charge-discharge tests of Li/$Li_2Mn_3O_7$ and Li/AC half-cell were carried out. Applying to AC/$Li_2Mn_3O_7$ hybrid capacitor, it had high discharge capacitance of 32.8 F/cc at 100 mA/g.

• Journal of Electrochemical Science and Technology
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• v.4 no.3
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• pp.102-107
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• 2013

The electrochemical properties of Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ and pure $LiFe_{0.5}Mn_{0.5}PO_4$ olivine cathodes are examined and the lattice parameters are refined by Rietveld analysis. The calculated atomic parameters from the refinement show that $Mg^{2+}$ doping has a significant effect in the olivine $LiFeMnPO_4$ structure. The unit cell volume is 297.053(2) ${\AA}^3$ for pure $LiFe_{0.5}Mn_{0.5}PO_4$ and is decreased to 296.177(1) ${\AA}^3$ for Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample. The doping of $Mg^{2+}$ cation with atomic radius smaller than $Mn^{2+}$ and $Fe^{2+}$ ion induces longer Li-O bond length in $LiO_6$ octahedra of the olivine structure. The larger interstitial sites in $LiO_6$ octahedra facilitate the lithium ion migration and also enhance the diffusion kinetics of olivine cathode material. The $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample with larger Li-O bond length delivers higher discharge capacities and also notably increases the rate capability of the electrode.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.653-656
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• 2009

3-Dimensionally ordered macroporous $LiMn_2O_4$ thin film was prepared by a sol-gel and dip coating method on Pt/Ti/$SiO_2$/Si substrate. An opal structure consisting of mono dispersed polystyrene beads (300 nm) was used as a template. After solution containing Mn and Li precursors was coated on the template-deposited substrate, the template and organic materials in the precursors was removed by calcination at 400 ${^{\circ}C}$. And then the 3-dimensional $LiMn_2O_4$ thin film with spinel structure was fabricated by heat treatment at 700 ${^{\circ}C}$. The structural and electrochemical property was investigated by XRD, SEM and charge-discharge cycler.

• 한국전기화학회:학술대회논문집
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• 2001.04a
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• pp.55-55
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• 2001