• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.4
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• pp.154-159
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• 2001

(Li,Al)$MnO_2(OH)_2$:Co compound was synthesized by hydrothermal method. $MnO_2$, LiOH.$H_2$O, $Co_3O_4$ and $Al(OH)_3$ were used as starting materials and the optimum conditions for synthesis of monolithic (Li,Al)$MnO_2(OH)_2$:Co compound were as follows : reaction temperature; $200^{\circ}C$, reaction time; 3 days, hydrothermal solvent; 3M-KOH solution, reaction apparatus; seesaw type, atomic ratio of Li:Al:Mn;Co = 1:2.1:2.5~2:0.5~1. Monolithic(Li,Al)$MnO_2(HO)_2$:Co compound synthesized in this work had a god crystallinity and excellent color forming effect as a blue pigment compatible with natural mineral. The particles of the synthesized (Li,Al)$MnO_2(OH)_2$:Co compound have hexagonal plate shape with the size of 0.5~1 $\mu\textrm{m}$.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.242-246
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• 2017

The application of composite cathode materials including $LiFePO_4$ (lithium iron phosphate) of olivine crystal structure, which has high thermal stability, were investigated as alternatives for hybrid battery-capacitors with a $LiMn_2O_4$ (spinel crystal structure) cathode, which exhibits decreased performance at high temperatures due to Mn-dissolution. However, these composite cathode materials have been shown to have a reduction in capacity by conducting life cycle experiments in which a $LiFePO_4$/activated carbon cell was charged and discharged between 1.0 V and 2.3 V at two temperatures, $25^{\circ}C$ and $60^{\circ}C$, which caused a degradation of the anode due to the lowered voltage in the anode. To avoid the degradation of the anode, composite cathodes of $LiFePO_4/LiMn_2O_4$ (50:50 wt%), $LiFePO_4$/activated carbon (50:50 wt%) and $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ (50:50 wt%) were prepared and the life cycle experiments were conducted on these cells. The composite cathode including $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ of layered crystal structure showed stable voltage behavior. The discharge capacity retention ratio of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ was about twice as high as that of a $LiFePO_4/LiMn_2O_4$ cell at thermal stability experiment for a duration of 1,000 hours charged at 2.3 V and a temperature of $80^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.55 no.1
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• pp.21-35
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• 2018

Spinel $LiNi_{0.5}Mn_{1.5}O_4$ has received great attention as one of the most outstanding cathode materials for Li-ion batteries (LIBs) because of its high energy density resulting from the operating voltage of ~ 4.7 V (vs. $Li^+/Li$) based on the $Ni^{2+}/Ni^{4+}$ redox reaction. However, $LiNi_{0.5}Mn_{1.5}O_4$ is known to suffer from undesirable side reactions with the electrolyte at high voltage as well as Mn dissolution from the structure. These issues prevent the realization of the optimal electrochemical performance of $LiNi_{0.5}Mn_{1.5}O_4$. Extensive research has been conducted to overcome these issues. This review presents an overview of the various surface-modification methods available to improve the electrochemical properties of $LiNi_{0.5}Mn_{1.5}O_4$ and provides perspectives on further research aimed at the application of $LiNi_{0.5}Mn_{1.5}O_4$ as a cathode material in commercialized LIBs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.1-4
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• 1991

The applicability of $LiNbO_{3}$ as a substrate for fabrication of Ti-indiffused waveguide electro-optic devices is limited. Ti diffuses comparatively in congruently melting $LiNbO_{3}$; the Curie temperature of this material is too low to permit diffusion temperatures much above $1100^{\circ}C$ without the necessity of re-poling the crystal. Both of hese difficulties could be eliminated by incorporating certain dopants in $LiNbO_{3}$. Crystals of $LiNbO_{3}$ doped with Ti and Mg were grown and evaluated. The electroptic coefficients and birefringence of $LiNbO_{3}$ doped crystals were measured at ${\lambda}=.6328$ and $1.32\;$\mu{m}$. Curie temperatures were measured. The Curie temperature of both undoped and Ti-doped $LiNbO_{3}$ was $1130^{\circ}C$; that for Mg-doped $LiNbO_{3}$ was $30^{\circ}$ higher. From these data, a composition for the crystals was estimated. Thermogravimetric data confirmed this estimate and showed that the composition of Mg : $LiNbO_{3}$ was $49.3{\pm}0.2mole%\;Li_{2}O$ ; the composition of the undoped and Ti : $LiNbO_{3}$ samples was $48.6{\pm}0.2mole%$. Diffusion of Ti into both Mg-doped and Ti-doped $LiNbO_{3}$ crystals was studied as a function of $Li/NbO_{3}$ ratio and temperature.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.269.1-269
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• 2002

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.735-741
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• 2004

$LiMn_{1.92}Co_{0.08}O_4$ and $LiNi_{0.7}Co_{0.3}O_2$ synthesized by a simplified combustion method had good electrochemical properties. Mixtures $LiMn_{1.92}Co_{0.08}O_4$-x wt$\%$ $LiNi_{0.7}Co_{0.3}O_2$ (x=9, 23, 33, 41, and 47) were prepared by milling for 30 min and their electrochemical properties were investigated. The electrode with x=9 had a relatively large first discharge capacity (109.9 mAh/g at 0.1 C) and good cycling performance. The decrease in the discharge capacity of the mixture electrodes with cycling is considered to result mainly from the degradation of $LiNi_{0.7}Co_{0.3}O_2$, caused by coating of $LiNi_{0.7}Co_{0.3}O_2$ with Mn dissolved from $LiMn_{1.92}Co_{0.08}O_4$.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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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).

• Journal of the Korean Magnetic Resonance Society
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• v.20 no.1
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• pp.1-6
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• 2016

The proton NMR line widths and spin-lattice relaxation rates, $T_1^{-1}$, of ferroelectric $LiH_3(SeO_3)_2$, $Li_2SO_4{\cdot}H_2O$, and $LiN_2H_5SO_4$ single crystals were measured as a function of temperature. The line width measurements reveal rigid lattice behavior of all the crystals at low temperatures and line narrowing due to molecular motion at higher temperatures. The temperature dependences of the proton $T_1^{-1}$ for these crystals exhibit maxima, which are attributed to the effects of molecular motion by the Bloembergen - Purcell - Pound theory. The activation energies for the molecular motions of $^1H$ in these crystals were obtained. From these analysis, $^1H$ in $LiH_3(SeO_3)_2$ undergoes molecular motion more easily than $^1H$ in $LiN_2H_5SO_4$ and $Li_2SO_4{\cdot}H_2O$ crystals.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.8
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• pp.737-743
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• 2006

[ $Li[Co_{0.50}Li_{0.17}Mn_{0.33}]O_2$ ] powder was prepared using a simple combustion method. specially, ratio of 2:1, 3:2, 1:1, 2:3, 1:2 was adopted as acetate source/nitrate source. The diffraction pattern of $Li[Co_{0.50}Li_{0.17}Mn_{0.33}]O_2$ powder showed that this compound could be classified as hexagonal $a-NaFeO_2$ structure (space group : $R\bar{3}m$). The size of powder was less than $1{\mu}m$. Small particle size of cathode powder would give a good ionic and electronic conductivity to cathode electrode, which made of cathode powder. As the increase of nitrate source-ratio, discharge capacity of $Li[Co_{0.50}Li_{0.17}Mn_{0.33}]O_2$ at high charge-discharge rate was increased. When the ratio of acetate source/nitrate source was 1:2, discharge capacity at 10 C rate (2000 mA/g) was 180 mAh/g. It was $10{\sim}15%$ larger than that of powder, which have 2:1 as acetate source/nitrate ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.418-419
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• 2005

$\o-LiMnO_2$ is known to have poor cycle performance causing the irreversible phase transformation on cycling. In this paper, the effect of chemical substitution on improving cycle performance of $o-LiMnO_2$ was studied at the compositions of $LiCr_xMn_{1-x}O_2$(x=0, 0.1, 0.2, 0.4). XRD is showed that structure of $LiCr_xMn_{1-x}O_2$ transformed from orthorhombic to spinel according to the increase of substitute degree. For lithium ion battery applications, $LiCr_xMn_{1-x}O_2$/Li cell were characterized electrochemically by charge/discharge cycling.