• Journal of Electrochemical Science and Technology
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• v.5 no.3
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• pp.87-93
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• 2014

The fluorine-substituted $0.3Li_2MnO_3{\cdot}0.7Li[Mn_{0.60}Ni_{0.25}Co_{0.15}]O_{2-x}F_x$ cathode materials were synthesized by using the transition metal precursor, $LiOH{\cdot}H_2O$ and LiF. This was to facilitate the movement of lithium ions by forming more compact SEI layer and to reduce the dissolution of transition metals. The $0.3Li_2MnO_3{\cdot}0.7Li[Mn_{0.60}Ni_{0.25}Co_{0.15}]O_{2-x}F_x$ cathode material was sphere-shaped and each secondary particle had $10{\sim}15{\mu}m$ in size. The fluorine-substituted cathodes initially delivered low discharge capacity, but it gradually increased until 50th charge-discharge cycles. These results indicated that fluorine substitution gave positive effects on the structural stabilization and resistance reduction in materials.

• Journal of the Korean Applied Science and Technology
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• v.20 no.1
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• pp.33-43
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• 2003

$LiMn_2O_4$ catalyst for $CO_2$ decomposition was synthesized by oxidation method for 30 min at 600$^{\circ}C$ in an electric furnace under air condition using manganese(II) nitrate $(Mn(NO_3)_2{\cdot}6H_2O)$, Lithium nitrate ($LiNO_3$) and Urea $(CO(NH_2)_2)$. The synthesized catalyst was reduced by $H_2$ at various temperatures for 3 hr. The reduction degree of the reduced catalysts were measured using the TGA. And then $CO_2$ decomposition rate was measured using the reduced catalysts. Phase-transitions of the catalysts were observed after $CO_2$ decomposition reaction at an optimal decomposition temperature. As the result of X-ray powder diffraction analysis, the synthesized catalyst was confirmed that the catalyst has the spinel structure, and also confirmed that when it was reduced by $H_2$, the phase of $LiMn_2O_4$ catalyst was transformed into $Li_2MnO_3$ and $Li_{1-2{\delta}}Mn_{2-{\delta}}O_{4-3{\delta}-{\delta}'}$ of tetragonal spinel phase. After $CO_2$ decomposition reaction, it was confirmed that the peak of $LiMn_2O_4$ of spinel phase. The optimal reduction temperature of the catalyst with $H_2$ was confirmed to be 450$^{\circ}C$(maximum weight-increasing ratio 9.47%) in the case of $LiMn_2O_4$ through the TGA analysis. Decomposition rate(%) using the $LiMn_2O_4$ catalyst showed the 67%. The crystal structure of the synthesized $LiMn_2O_4$ observed with a scanning electron microscope(SEM) shows cubic form. After reduction, $LiMn_2O_4$ catalyst became condensed each other to form interface. It was confirmed that after $CO_2$ decomposition, crystal structure of $LiMn_2O_4$ catalyst showed that its particle grew up more than that of reduction. Phase-transition by reduction and $CO_2$ decomposition ; $Li_2MnO_3$ and $Li_{1-2{\delta}}Mn_{2-{\delta}}O_{4-3{\delta}-{\delta}'}$ of tetragonal spinel phase at the first time of $CO_2$ decomposition appear like the same as the above contents. Phase-transition at $2{\sim}5$ time ; $Li_2MnO_3$ and $Li_{1-2{\delta}}Mn_{2-{\delta}}O_{4-3{\delta}-{\delta}'}$ of tetragonal spinel phase by reduction and $LiMn_2O_4$ of spinel phase after $CO_2$ decomposition appear like the same as the first time case. The result of the TGA analysis by catalyst reduction ; The first time, weight of reduced catalyst increased by 9.47%, for 2${\sim}$5 times, weight of reduced catalyst increased by average 2.3% But, in any time, there is little difference in the decomposition ratio of $CO_2$. That is to say, at the first time, it showed 67% in $CO_2$ decomposition rate and after 5 times reaction of $CO_2$ decomposition, it showed 67% nearly the same as the first time.

• 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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• 2007.11a
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• pp.515-515
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• 2007

$LiCoO_2$ powder was synthesized by Sol-Gel method using inorganic materials. The starting materials, $CH_3COOLi^*2H_2O\;and\;Co(CH_3COO)_2{^*}4H_2O$, were mixed in the atomic ratio Li/Co of 1 and dissolved in i-propanol with acetic acid. The solution was dried for gelation, and finally obtained the pre-powder. The pre-powder were studied by thermal analysis. Based on the TGA result, heat treatment was performed at various temperature(500 to $800^{\circ}C$) for 2h in air atmosphere. The crystal structure, morphology, electrochemical property were carried out using XRD, SEM, cyclic voltammetry(CV).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.5
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• pp.443-449
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• 2007

The structural and thermal stability of $Li[Co_{0.1}Ni_{0.15}Li_{0.2}Mn_{0.55}]O_2$ electrode during cycling process was studied. The sample was prepared by simple combustion method. Although there were irreversible changes on the initial cycle, O3 stacking for $Li[Co_{0.1}Ni_{0.15}Li_{0.2}Mn_{0.55}]O_2$ structure was retained during the first and subsequent cycling process. Impedance of the test cell was decreased after the first charge-discharge process, which would be of benefit to intercalation and deintercalation of lithium ion on subsequent cycling. As expected, cycling test for 75 times increased impedance of the cell a little, instead, thermal stability of $Li[Co_{0.1}Ni_{0.15}Li_{0.2}Mn_{0.55}]O_2$ was improved. Moreover, based on DSC analysis, the initial exothermic peak was shifted to high temperature range and the amount of heat was also decreased after cycling test, which displayed that thermal stability was not deteriorated during cycling.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.11
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• pp.1029-1035
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• 2008

$LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ cathode materials prepared from different precursors in lithium rechargeable batteries were characterized by various analytical methods. $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ powders were synthesized by using solid-state reaction method and their physical and chemical properties were analyzed by XRD, SEM, particle size analyzer and TCP-AES. These materials showed different crystallinity, particle size, surface morphology and chemical composition. Also, the charge/discharge cycling of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ electrodes was carried out under various cut-off voltages and it showed different behaviors. It was found that the electrochemical cyclability of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ was strongly related to its crystallinity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.5
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• pp.298-302
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• 2016

In this work, $LiMn_2O_4$ and $LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ cathode materials are mixed by some specific ratios to enhance the practical capacity, energy density and cycle performance of battery. At present, the most used cathode material in lithium ion batteries for EVs is spinel structure-type $LiMn_2O_4$. $LiMn_2O_4$ has advantages of high average voltage, excellent safety, environmental friendliness, and low cost. However, due to the low rechargeable capacity (120 mAh/g), it can not meet the requirement of high energy density for the EVs, resulting in limiting its development. The battery of $LiMn_2O_4-LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ (50:50 wt%) mixed cathode delivers a energy density of 483.5 mWh/g at a current rate of 1.0 C. The accumulated capacity from $1^{st}$ to 150th cycles was 18.1 Ah/g when the battery is cycled at a current rate of 1.0 C in voltage range of 3.2~4.3 V.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.94-98
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• 2014

$LiCoO_2$ thin film has received diverse attention as cathodes material of thin-film micro-batteries. In this study, $LiCoO_2$ thin films were synthesized on Au substrates by sol-gel spin coating method and an annealing process. Their structures were studied using X-ray diffraction and Raman Spectroscopy. The particle morphologies of these thin films were observed by Scaning electron microscope. From the results of X-ray diffractometry and Raman Spectroscopy analyses, it was found that as-grown films had the structure of spinel (LT-$LiCoO_2$) and layered-Rock-salt (HT-$LiCoO_2$) at $550^{\circ}C$ and $750^{\circ}C$ respectively. The annealed films at $650^{\circ}C$ were presumed to be the mixed state of these two types. Throlugh the scanning electron microscope, It was estimated that the particle size in as-grown films at $750^{\circ}C$, were larger crystilline particle than in those at the other lower temperature and well distributed in the film.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.336-337
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• 2005

This study shows the effect of addition of $LiCoO_2$, with different milling time ranging from 0, 30, 200 hours, to the activated carbon electrode. Test cells consisting of activated carbon (100-X%) and $LiCoO_2$ (X%)were made (where X=10, 20, and 40). Test cells with varying concentrations of $LiCoO_2$ which differ in the milling time showed improved specific capacity compare with the cells fabricated using activated carbon alone. The enhanced capacity may be caused due to the addition of $LiCoO_2$ powders at varying concentration. An improved ESR value obtained may be caused by the smaller particle size of $LiCoO_2$. It was concluded that finer the particle size higher will be the efficiency.

• Journal of Sensor Science and Technology
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• v.9 no.2
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• pp.146-152
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• 2000

Lithium doped zinc oxide(ZnO:Li) films are prepared by rf magnetron sputtering on Corning 7059 glass substrate using specifically designed ZnO targets containing different amount of $Li_2CO_3$ powder as the Li doping source. The structural properties of the Li doped ZnO films are investigated by XRD, SEM and AFM. The electrical properties of the ZnO:Li films are measured for various deposition conditions, such as the substrate temperature, $O_2$/Ar gas ratio and rf power. The effects of the $Li_2CO_3$ content in target and the deposition conditions on the structural and electrical properties were studied. When ZnO:Li films were sputtered at the substrate temperature of $200^{\circ}C$, $O_2$/Ar gas ratio of 100% and rf power of 100W with a target containing less than 1wt% content of $Li_2CO_3$, showed good surface morphology, strong c-axis orientation and high resistivity of more than $10^8{\Omega}cm$.