• Bulletin of the Korean Chemical Society
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• v.22 no.12
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• pp.1328-1332
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• 2001

The structure and electrochemical properties of the LixCoyNi1-yO2 (y=0.1, 0.3, 0.5, 0.7, 1.0) system synthesized by solid state reaction with various starting materials have been investigated to optimize the characteristics and synthetic conditions of the LixCoyNi1-yO2. The first discharge capacities of LixCoyNi1-yO2 are 60 mAh/g-180 mAh/g with synthetic conditions. Among them, the LixNi0.7Co0.3O2, which was prepared with LiOH, NiO, and Co3O4 at $850^{\circ}C$, had the best electrochemical properties. The first discharge capacity of the compound was 180 mAh/g.

• Bulletin of the Korean Chemical Society
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• v.9 no.6
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• pp.349-352
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• 1988

[(Benzene)Mn$(CO)_3$]$^+$ reacts with NaP(O) (OR)$_2$ (R = Me, Et, Ph) to give the phosphonate compound 1. Compound 1 reacts with R'Li (R = Me, Ph, $^nBu, ^tBu$) to yield the isomerized compound 2 and the alkylated compound 3. [(Toluene)Mn$(CO)_3$]$^+$ reacts with NaP(O)$(OMe)_2$ to give the phosphonate complexes 1-A and 1-B. Treatment of 1-A with $^tBuLi$ in THF affords complexes 3-A and 3-B with the later major. With 1-B only the complex 3-C is formed. [(Anisole)Mn$(CO)_3$]$^+$ reacts with NaP(O)$(OMe)_2$ to give the phosphate complex 1-C, which on treatment with $^tBuLi$ and then $H_2O$ yields compound 3-D. After demetallation of compound 3-D, meta-tertbutyl-anisole is obtained in a reasonable yield.

• Journal of Welding and Joining
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• v.3 no.1
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• pp.40-45
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• 1985

Wire meling characteristics were examined with variation of gas formers such as $MgCO_3, CaCO_3 and Li_ 2CO_ 3$ by self-shielded flux cored arc welding. The flux cored wire of overlap type was welded by DCRP. The results obtainedareas follows. 1) Drop type was observed with no gas former, repelled type with MgCO_3$ added and short circuit type with $Li_2CO_3$ added. The variation of transfer mode was related to the blowing force of $CO_2$ gas and the surface tension of the slag. 2) Droplet size increased with adding gas formers due to the effect of $CO_2$ gas cushion. 3) Core spikes were observed more frequently with increasing the amount of gas formers.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.3
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• pp.217-228
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• 2003

Li 이차 전지 음극용 활물질인 $Co_3O_4$의 초기 충방전 효율을 향상시키기 위해 chemical reduction method나 mechanical milling법을 이용하여 $Co_3O_4$에 Ni을 첨가하여 $Ni-Co_3O_4$, 복합물을 제조하였다. 그 결과 초기 충방전 효율이 약 69%에 불과한 $Co_3O_4$에 비해 mechanical milling법을 이용하여 제조된 $Ni-Co_3O_4$ 복합물은 약 79%이상의 대폭 향상된 초기 충방전 효율 특성을 나타내었다. 하지만 chemical reduction method를 이용하여 제조된 $Ni-Co_3O_4$ 복합물은 약 71%의 초기 충방전 효율 특성만을 나타내었다. SEM 분석을 통해 각 물질의 표면 형상을 관찰한 결과 mechanical milling법과 chemical reduction method를 통해 제조된 $Ni-Co_3O_4$ 복합물에서는 $Co_3O_4$ 표면에 분포된 Ni의 균일성의 차이가 존재하였다. $Co_3O_4$가 $Li_2O$의 분해, 형성에 의해 충방전되고 Ni이 $Li_2O$의 분해를 촉진시키는 효과를 가지고 있음을 고려할 때 이러한 균일성의 차이는 결국 Ni 과 $Co_3O_4$ 사이의 접촉면적의 차이로 이어져 $Ni-Co_3O_4$ 복합물의 초기 충방전 효율 특성이 그 제조 방법에 따라 달라지는 것으로 보인다.

• Journal of Powder Materials
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• v.23 no.2
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• pp.136-142
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• 2016

As precursors of cathode materials for lithium ion batteries, $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders are prepared in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH in the presence of $NH_4OH$ in air or nitrogen ambient. Calcination of the precursors with $Li_2CO_3$ for 8 h at $1,000^{\circ}C$ in air produces dense spherical cathode materials. The precursors and final powders are characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analysis, tap density measurement, and thermal gravimetric analysis. The precursor powders obtained in air or nitrogen ambient show XRD patterns identified as $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$. Regardless of the atmosphere, the final powders exhibit the XRD patterns of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ (NCM). The precursor powders obtained in air have larger particle size and lower tap density than those obtained in nitrogen ambient. NCM powders show similar tendencies in terms of particle size and tap density. Electrochemical characterization is performed after fabricating a coin cell using NCM as the cathode and Li metal as the anode. The NCM powders from the precursors obtained in air and those from the precursors obtained in nitrogen have similar initial charge/discharge capacities and cycle life. In conclusion, the powders co-precipitated in air can be utilized as precursor materials, replacing those synthesized in the presence of nitrogen injection, which is the usual industrial practice.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2571-2576
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• 2011

Surface film formation on $Li(Ni_{1/3}Co_{1/3}Mn_{1/3})O_2$ cathodes upon oxidation of electrolyte during electrochemical cycling was investigated. Information on the important factors for film formation on the cathode can facilitate the design of additives that improve the properties of the cathode. Pyrazole is added to the electrolyte because it is readily oxidized to form a surface film on the cathode. The results of differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR) showed that the active material played a dominant role in the interfacial film formation with the electrolyte. Carbon black played a negligible role in the surface film formation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.99-105
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• 2014

$LiCoO_2$ thin film have received attention as cathodes of thin-film microbatteries. In this study, $LiCoO_2$ thin films were synthesized on Au substrates by sol-gel spin coating method and electrochemical properties were investigated under annealing temperature and time. The phycochemical properties of $LiCoO_2$ thin film were investigated by X-ray diffraction, scaning electron microscopy and atomic force microscopy. The electrochemical properties were characterized using galvanostatic charging/discharging cycling tests. From X-ray diffraction, as-grown films annealed at $550^{\circ}C$ and $750^{\circ}C$ are presumed to be spinel structure and a single phase of the layered-rock-salt, respectively. The RMS roughness and grain size of the films which annealed at $750^{\circ}C$ has similar values for annealing time 10 and 30 min, while for annealing time 120 min surface roughness, grain size increase and pore appearance were observed. The first discharge capacity of $LiCoO_2$ thin films annealed at $750^{\circ}C$ for 10, 30 and 120 min is about 54.5, 56.8 and $51.87{\mu}Ah/cm^2{\mu}m$, respectively. Corresponding capacity retention at 50th cycle is 97.25, 76.69, 77.19%.

• 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 the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1025-1028
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• 2006

Dense $0.95(Na_{0.5}K_{0.5})NbO_3-0.05LiTaO_3$ (NKN-5LT) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding $Na_2CO_3$ as a sintering aid. The electrical properties of NKN-5LT ceramics were investigated as a function of $Na_2CO_3$ concentration. When the sample sintered at $1000^{\circ}C$ for 4 h with the addition of 1 mol% $Na_2CO_3$, electro-mechanical coupling factor $(k_p)$ and piezoelectric coefficient $(d_{33})$ of NKN-5LT ceramics were found to reach the highest values of 0.43 and 190 pC/N, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.2
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• pp.152-155
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• 2007

In this study, we fabricated FBAR(film bulk acoustic resonator) by using $Li_{2}CO_{3}:ZnO$ as a function of annealing temperature and concentrated on effect of frequency characteristic of FBAR. The results show that the annealing affects resistivity and crystallity. The optimum properties were observed for film annealed at $500^{\circ}C$. The resistivity was $1.5{\times}10^{11}\;{\Omega}{\cdot}cm$ and the roughness was 21.10 nm. And the return loss is improved from -24.9 at $300^{\circ}C$ to -29.8 at $500^{\circ}C$ without the resonant frequency change. We finally confirmed the improvement on the frequency characteristics of FBAR device by annealing process at the optimized condition.