• Bulletin of the Korean Chemical Society
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• v.19 no.1
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• pp.39-44
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• 1998

$LiCoO_2$ powder was synthesized in an aqueous solution by a sol-gel method and used as a cathode active material for a lithium ion rechargeable battery. The layered $LiCoO_2$ powders were prepared by igniting in air for 12 hrs at 600 ℃ $(600-LiCoO_2)$ and 850 ℃ $(850-LiCoO_2)$. The structure of the $LiCoO_2$ powder was assigned to the space group R bar 3 m (lattice parameters a=2.814 Å and c=14.04Å). The SEM pictures of $600-LiCoO_2$ revealed homogeneous and fine particles of about 1 μm in diameter. Cyclic voltammograms (CVs) of $600-LiCoO_2$ electrode displayed a set of redox peaks at 3.80/4.05 V due to the intercalation/deintercalation of the lithium ions into/out of the $LiCoO_2$ structure. CVs for the $850-LiCoO_2$ electrode had a major set of redox peaks at 3.88/4.13 V, and two small set of redox peaks at 4.18/4.42 V and 4.05/4.25 V due to phase transitions. The initial charge-discharge capacity was 156-132 mAh/g for the $600-LiCoO_2$ electrode and 158-131 mAh/g for the $850-LiCoO_2$ electrode at the current density of 0.2 mA/cm2. The cycleability of the cell consisting of the $600-LiCoO_2$ electrode was better than that of the $850-LiCoO_2$. The diffusion coefficient of the $Li^+$ ion in the $600-LiCoO_2$ electrode was calculated as $4.6{\times}10^{-8}\; cm^2/sec$.

• Electrical & Electronic Materials
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• v.7 no.4
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• pp.317-324
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• 1994

In this study, new preparation method of LiCoO$_{2}$ was applied to develop cathode active material for Li rechargeable cell, and followed by X-ray diffraction analysis, electrochemical properties and initial charge/discharge characteristics as function of current density. HC8A72- and CC9A24-LiCoO$_{2}$ were prepared by heating treatment of the mixture of LiOH H$_{2}$O/CoCO$_{3}$(1:1 mole ratio) and the mixture of Li$_{2}$CO$_{3}$/CoCO$_{3}$(1:2 mole ratio) at 850 and 900.deg. C, respectively. Two prepared LiCoO$_{2}$s were identified as same structure by X-ray diffraction analysis. a and c lattice constant were 2.816.angs. and 14.046.angs., respectively. The electrochemical potential of CFM-LiCoO$_{2}$(Cyprus Foote Mineral Co.'s product), HC8A72-LiCoO$_{2}$ and CC9A24 LiCoO$_{2}$ electrode were approximately between 3.32V and 3.42V vs. Li/Li reference electrode. Stable cycling behavior was obtained during the cyclic voltammetry of LiCoO$_{2}$ electrode. According as scan rate increases, cathodic capacity decreases, but redox coulombic efficiency was about 100% at potential range between 3.6V and 4.2V vs. Li/Li reference electrode. Cathodic capacity of HC8A72-LiCoO$_{2}$ was 32% higher than that of CFM-LiCoO$_{2}$ and that of CC9A24-LiCoO$_{2}$ was 47% lower than that of CFM-LiCoO$_{2}$ at 130th cycle in the condition of lmV/sec scan rate. Constant cur-rent charge/discharge characteristics of LiCoO$_{2}$/Li cell showed increasing Ah efficiency with initial charge/discharge cycle. Specific discharge capacities of CFM and HC8A72-LiCoO$_{2}$ cathode active materials were about 93mAh/g correspondent to 34% of theretical value, 110mAh/g correspondent to 40% of theretical value, respectively. In the view of reversibility, HC8A72-LiCoO$_{2}$ was also more excellent than CFM- and CC9A24-LiCoO$_{2}$.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.129.1-129
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• 2000

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1129-1135
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• 1999

Free energy perturbation and molecular dynamics simulations were carried out to investigate the relative binding affinities of [17] ketonand (1) toward alkali metal cations in methanol. The binding affinities of 1 toward the alkali metal cations were calculated to be in the order Li+ > Na+ > K+ > Rb+ > Cs+, whereas our recent theoretically predicted and experimentally observed binding affinities for [18]starand (2) were in the order K+ > Rb+ > Cs+ > Na+ > Li+. The extremely different affinities of 1 and 2 toward smaller cations, Li + and Na+ , were explained in terms of the differences in their ability to change the conformation to accommodate cations of different sizes. The carbonyl groups constituting the central cavity of 1 can reorganize to form a cavity with the optimal M+ -O distance, even for the smallest Li+, without imposing serious strain on 1. The highest affinity of 1 for Li+ was predominantly due to the highest Coulombic attraction between the smallest Li+ and the carbonyl oxygens of 1.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.277-278
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• 2008

Orthorhombic $LiMnO_2$(o-$LiMnO_2$) has attracted public attentions as a cathode materials of Lithium ion battery because it has low cost and high theoretical discharge capacity of 285mAh $g^{-1}$. In our study, o-$LiMnO_2$ is synthesized by quenching method. To verify their phase structure, X-ray diffraction is accomplished. Test cells are assembled to check electrochemical characteristics using acquired o-$LiMnO_2$ cathode and carbon anode. Charge/Discharge cycling was carried out for 50cycles. And impedance was measured at 1, 2, 5, 10, 30, 50cycle. During cycle test, the max discharge capacity was recorded 139mAh $g^{-1}$ at 10cycle.

• Journal of the Korean Electrochemical Society
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• v.17 no.1
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• pp.49-56
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• 2014

As an electrolyte additive, the effects of lithium bis(oxalate)borate (LiBOB) on the electrochemical properties of a carbon-coated silicon monoxide (C-coated SiO) negative electrode are investigated. The used electrolyte is 1.3M $LiPF_6$ that is dissolved in ethylene carbonate (EC), fluoroethylene carbonate (FEC), and diethyl carbonate (DEC) (5:25:70 v/v/v) with or without 0.5 wt. % LiBOB. In the LiBOB-free electrolyte, the film resistance is not so high in the initial period of cycling that lithiation is facilitated to generate the crystalline $Li_{15}Si_4$ phase. Due to repeated volume change that is caused by such a deep charge/discharge, cracks form in the active material to cause a resistance increase, which eventually leads to capacity fading. When LiBOB is added into the electrolyte, however, more resistive surface film is generated by decomposition of LiBOB in the initial period. The crystalline $Li_{15}Si_4$ phase does not form, such that the volume change and crack formation are greatly mitigated. Consequently, the C-coated SiO electrode exhibits a better cycle performance in the later cycles. At an elevated temperature ($45^{\circ}C$), wherein the effect of film resistance is less critical, the alloy ($Li_{15}Si_4$ phase) formation is comparable for the LiBOB-free and added cell to give a similar cycle performance.

• The Journal of Korean Medicine
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• v.19 no.1
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• pp.66-88
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• 1998

This study was performed from March to September 1997 on 95 healthy students to observe the effects of acupuncture at Hap-kok (LI4) according to the meridian and qi-xue(氣血) phenomenon of oriental medicine's theory. Skin temperature on the Hap-kok (LI4) and Chun-Choo (ST25) were measured by D. 1. T. I. (Digital Infrared Thermograph Imaging) before acupuncture stimulation and 1min, 10 min after acupuncture stimulation. 1. In healthy students, the left and right mean temperature of LI4 and ST25 was $29.04\;^{\circ}C,\;29.12\;^{\cir}C\;and\;30.29\;^{\circ}C,\;30.22\;^{\circ}C$ respectively. 2. In control group, the time dependent changes for 10 min of LI4 and ST25 were $-0.32\;^{\circ}C,\;-0.36\;^{\circ}C\;and\;-0.5\;^{\circ}C,\;-0.46\;^{\circ}C$ respectively, however, the thermal differences of both sides LI4 and ST25 were not changed for 10 min. 3. In acupuncture stimulation of both sides LI4, the time dependent changes of ST25 were $-0.13\;^{\circ}C,\;-0.06\;^{\circ}C$, and the thermal differences of both sides ST25 were reduced, but not changed significantly. In acupuncture stimulation of right side LI4, the time dependent changes of LI4 were $-0.1\;^{\circ}C,\;-0.32\;^{\circ}C$ respectively, and the thermal differences of both sides LI4 were increased more than control, but not significantly. Also, that of ST25 were changed by $-0.69\;^{\circ}C,\;-0.63\;^{\circ}C$ respectively, but not significantly. 4. In acupuncture stimulation group, it was classified following the thermal differences of both sides LI4 and ST25, and the effects of acupuncture were observed by changes of classification. The acupuncture of both sides LI4 results in temperature of the left side ST25 to be high after acupuncture. The acupuncture of right side LI4 results in increased ratio of the left side higher than right LI4. The above results indicates that D. I. T. I. was a useful method to observe follow-up the effects and changes by acupuncture stimulation on objective evaluation of phenomenon for the meridian system. Thus, acupuncture on LI4 affects to thermal changes of ST25 and LI4, but exact examination of thermal changes on ST25 will have to be.

• Journal of the Korean Chemical Society
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• v.47 no.6
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• pp.619-624
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• 2003

The $Gd_{1.9-x}Li_{0.1}Eu_xO_3$ (x=0.02, 0.05, 0.08, and 0.12) powders (${\thickapprox}1{\mu}m$) synthesized by sol-gel method, whose surfaces are modified in a colloidal silica suspension (size of $SiO_2$ particles: ${\sim}30$ nm), have been fabricated to highly stable and effective luminescent films on the glass substrates. Thanks to the fused $SiO_2$ nano particles in the vicinity of the glass softening temperature (at around $700^{\circ}C$), $Gd_{1.9-x}Li_{0.1}Eu_xO_3$ powders are strongly attached onto the surface of glass substrate (>9H, pencil hardness tester). This simple and low-cost method to get $Gd_{1.9-x}Li_{0.1}Eu_xO_3$ phosphor films without any loss of luminescence brightness would promise for applications to display devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.4
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• pp.316-322
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• 2001

Cathode materials $LiMn_{2-y}$$M_{y}$ $O_4$(M=Zn and Mg) were obtained by reacting the mixture of LiOH.$H_2O$, Mn $O_2$ and MgO ar ZnO at 80$0^{\circ}C$ for 36h in an air atmosphere. These materials showed an extended cycle life in lithium-anode cells working at room temperatue in a 3.0 to 4.3V potential window. Among these materials, LiM $n_{1.9}$M $g_{0.1}$ $O_4$ showed the best cycle performance in terms of the capacity and cycle life. The discharge capacities of the cathode for the Li/LiM $n_{1.9}$ $M_{0.1}$ $O_4$ cell at the 1st cycle and at the 70th cycle were about 120 and 105mAh/g, respectively. This cell capacity is retained by 88% after 70th cycle. In cyclic voltammetry measurement, all cells revealed tow oxidation peaks and reduction peaks. However, Li/$LiMn_{2-y}$$M_{y}$ $O_4$ cell substituted with Zn and Mg showed new reaction peak during reduction reaction.eaction.ion.ion.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.128-137
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• 2022

For this study, the sol gel method was used to synthesize the spinel LiNi_0.5Mn_1.5O₄ (LNMO) electrode material. Structural, morphological, electrochemical, and kinetic aspects of the LNMO have been characterized. The synthesized LNMO was indexed with the Fd3m cubic space group. The excellent capacity retention indicates that the spinel framework of LNMO has the ability to withstand high rate charge-discharge throughout long cycle tests. The Li diffusion coefficient (D_Li) changes non-monotonically across three orders of magnitude, from 10^-9 to 10^-12 cm² s^-1 determined from GITT method. The variation of D_Li seemed to be related to three oxidation reactions that happened throughout the charging process. A small dip in D_Li at the beginning stage of Li deintercalation is correlated with the oxidation of Mn³⁺ to Mn⁴⁺. While two pronounced D_Li minima at 4.7 V and 4.75 V are due to the oxidation of Ni²⁺/Ni³⁺ and Ni³⁺/Ni⁴⁺ respectively. The depletion of D_Li at the high voltage region is attributed to the occurrence of two successive phase transformation phenomena.