• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.226-226
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• 2003

The Commercial LiCoO$_2$ particles, which were 7.7${\mu}{\textrm}{m}$ in average diameter, were coated with $Al_2$O$_3$ by a gas suspension spray coating method. The coating amount of $Al_2$O$_3$ on the surface of LiCoO$_2$ was varied from 0.1 to 2 wt.% and compared their electrochemical characteristics with those of bare LiCoO$_2$. $Al_2$O$_3$ coating on the surface of LiCoO$_2$ increased surface area and electrical conductivity, and showed the better cycle and thermal stability even at the higher voltage. The observed optimum A1$_2$O$_3$ coating amount that exhibited the highest capacity retention was 0.2 wt.%.

• Archives of Metallurgy and Materials
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• 제64권2호
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• pp.481-485
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• 2019

This study was attempted to study for recovery of Li as Li₂CO₃ from cathode active material, especially NCA (LiNiCoAlO₂), recovered from spent lithium ion batteries. This consists of two major processes, carbonation using CO₂ and water leaching. Carbonation using CO₂ was performed at 600℃, 700℃ and 800℃, and NCA (LiNiCoAlO₂) was phase-separated into Li₂CO₃, NiO and CoO. The water leaching process using the differences in solubility was performed to obtain the optimum conditions by using the washing time and the ratio of the sample to the distilled water as variables. As a result, NCA (LiNiCoAlO₂) was phase-separated into Li₂CO₃ and NiO, CoO at 700℃, and Li₂CO₃ in water was recovered through vacuum filtration after 1 hour at a 1:30 weight ratio of the powder and distilled water. Finally, Li₂CO₃ containing Li of more than 98 wt.% was recovered.

• 한국세라믹학회지
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• 제34권3호
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• pp.303-313
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• 1997

용융탄산염 연료전지(Molten Carbonate Fuel Cell) 메트릭스의 성형성 및 강도 증진을 위한 알루미나/${\gamma}$-LiAlO2 화이버 강화 매트릭스에 대하여 연구하였다. ${\gamma}$-LiAlO2 입자에 10~30wt%의 화이버를 첨가한 슬러리를 테이프캐스팅 한 후 $650^{\circ}C$까지 열처리하여 두께가 500~600$\mu\textrm{m}$인 MCFC 매트릭스를 제조하였다. 화이버의 첨가량이 증가할수록 매트릭스의 기공율은 감소하였으나 입자크기가 대략 50$\mu\textrm{m}$인 ${\gamma}$-LiAlO2 분체의 첨가비를 50wt%까지 증가시킴으로써 MCFC 매트릭스에 적합한 기공율(50~60%)을 얻을 수 있었다. 알루미나 화이버의 첨가량이 20wt% 이고 길이가 250$\mu\textrm{m}$이하인 화이버를 사용하였을 때 매트릭스내의 분산성 및 강도 증진 효과가 가장 우수하였다. 반면에 본 연구에서 제조한 ${\gamma}$-LiAlO2 화이버를 이용한 강화 매트릭스의 강도(156 gf/$\textrm{mm}^2$)는 알루미나 화이버 강화 매트릭스에 비해 20~40% 정도 증진되었다. 또한 알루미나 화이버 강화 매트릭스는 용융탄산염에 의하여 부식되지만 ${\gamma}$-LiAlO2 화이버 강화 매트릭스는 전혀 부식되지 않음을 알 수 있었다.

• Korean Chemical Engineering Research
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• 제47권1호
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• pp.84-88
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• 2009

Al이 치환된 $LiMn_2O_4$ 미세 분말을 구연산과 에틸렌 글리콜이 첨가된 분무용액으로부터 분무열분해 공정에 의해 합성하였다. 구형의 형상, 다공성의 구조 및 마이크론 크기를 가지는 전구체 분말들은 $800^{\circ}C$ 이상의 후열처리 온도에서 마이크론 크기 및 균일한 형태를 가지는 $LiMn_{11/6}Al_{1/6}O_4$ 분말들로 전환되었다. 후열처리 온도가 $700^{\circ}C$ 일 때 $LiMn_{11/6}Al_{1/6}O_4$ 분말은 94 mAh/g의 낮은 초기 방전 용량을 가졌다. 후열처리 온도가 $750^{\circ}C$에서 $1,000^{\circ}C$로 증가함에 따라 $LiMn_{11/6}Al_{1/6}O_2$ 분말의 초기 방전 용량은 103 mAh/g에서 117 mAh/g로 변화하였으며, 후열처리 온도 $750^{\circ}C$에서 최대 초기 방전용량을 가졌다. 반면에 후열처리 온도 $900^{\circ}C$에서 얻어진 $LiMn_{11/6}Al_{1/6}O_2$ 분말들이 좋은 사이클 특성을 가졌다. 전류밀도 0.1 C에서 70 사이클 충방전 후에 $LiMn_{11/6}Al_{1/6}O_4$ 분말들의 방전 용량은 107 mAh/g에서 100 mAh/g으로 감소하였고 93%의 사이클 효율을 유지하였다.

• 한국안광학회지
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• 제7권2호
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• pp.27-31
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• 2002

4성분 $Li_2O-B_2O_3-Al_2O_3-SiO_2$ 유리들을 $R({\equiv}Li_2Omole%/B_2O_3mole%)$과 $K({\equiv}(Al_2O_3mole%+SiO_2mole%/B_2O_3mole%)$에 의해 제작하여 유리들의 구조를 굴절률 (refractive index)과 Vicker's 경도(hardness)의 변화를 측정하여 분석하였다. 먼저, 굴절률의 증가는 유리 내부구조의 분극률을 증가시키는 $Li^+$ 양이온 수의 증가에 우선적으로 의존하여 증가하였으며, 적은 양의 리튬 산화물($Li_2O$)이 첨가된 영역에서는 굴절률은 리튬 이온 양에 의존하며, 많은 양의 리튬 산화물이 첨가된 영역에서는 큰 몰 부피를 갖고 하나의 비가교 산소를 갖는 $BO_3{^-}$ 단위들의 형성으로 유리 구조 내의 몰 부피 증가로 유리들의 굴절률의 증가가 둔화되었다. 그리고 알루미늄 산화물($Al_2O_3$)과 규소 산화물($SiO_2$)의 증가에 따라 굴절률의 감소는 $Al_2O_3$와 $SiO_2$에 의해 형성되어진 $AlO_4$ 단위들과 $SiO_4{^-}$ 단위들이 붕소 산화물($B_2O_3$)에 의해 형성되어진 $BO_4$단위들보다 몰 부피의 증가로 감소되어졌다. 또한, 경도의 증가는 유리 망목구조에 형성되어지는 $BO_4$ 단위 수에 의존하였으며, 경도의 감소는 유리 망목구조를 개방화시키는 $BO_3{^-}$ 단위 수에 의존하여 감소함을 알 수 있었다.

• 한국세라믹학회지
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• 제33권10호
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• pp.1079-1088
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• 1996

Discontinuous ${\gamma}$-LiAlO2 fibers for fiber-reinforcing MCFC matrixes have been produced by the sol-gel process using the centrifugal spinning apparatus of the Rotary type. Gel fibers could be obtained through spinning of stable LiAlO2 complex polymetric sols under the optimum spinning conditions (hollow-disc rotating velocity 9000 rpm sol feeding rate of 4ml/min flowing N2 temperature of 4$0^{\circ}C$ and flowing N2 pressure of 4 bar). It was found that defect free and densified ${\gamma}$-LiAlO2 fibers with the relative density of 98% and the mean diameter of 4.7${\mu}{\textrm}{m}$ were prepared when the spinned fibers were heat-treated to 100$0^{\circ}C$ on the specified heating schedule. in particular the mean diameter and length of fibers could be controlled by the pressure of flowing N2 and the chopping-sieving method respectively.

• 한국재료학회지
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• 제17권8호
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• pp.447-451
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• 2007

We investigated the dependence of the various annealing conditions and thickness ($6\sim45nm$) of the Ti-doped $Al_2O_3$ coating on the electrochemical properties and the capacity fading of Ti-doped $Al_2O_3$ coated $LiCoO_2$ films. The Ti-doped-$Al_2O_3$-coating layer and the cathode films were deposited on $Al_2O_3$ plate substrates by RF-magnetron sputter. Microstructural and electrochemical properties of Ti-doped-$Al_2O_3$-coated $LiCoO_2$ films were investigated by transmission electron microscopy (TEM) and a dc four-point probe method, respectively. The cycling performance of Ti-doped $Al_2O_3$ coated $LiCoO_2$ film was improved at higher cut-off voltage. But it has different electrochemical properties with various annealing conditions. They were related on the microstructure, surface morphology and the interface condition. Suppression of Li-ion migration is dominant at the coating thickness >24.nm during charge/discharge processes. It is due to the electrochemically passive nature of the Ti-doped $Al_2O_3$ films. The sample be made up of Ti-doped $Al_2O_3$ coated on annealed $LiCoO_2$ film with additional annealing at $400^{\circ}C$ had good adhesion between coating layer and cathode films. This sample showed the best capacity retention of $\sim92%$ with a charge cut off of 4.5 V after 50 cycles. The Ti-doped $Al_2O_3$ film was an amorphous phase and it has a higher electrical conductivity than that of the $Al_2O_3$ film. Therefore, the Ti-doped $Al_2O_3$ coated improved the cycle performance and the capacity retention at high voltage (4.5 V) of $LiCoO_2$ films.

• 한국세라믹학회지
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• 제32권4호
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• pp.507-515
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• 1995

The monolithic dry gels of the Li2O-Al2O3-TiO2-SiO2 system were prepared by the sol-gel technique using metal alkoxides as starting materials to obtain monolithic glass-ceramics at low temperature without melting. Activation energy for the crystal growth of the gel with 6.05% TiO2, nucleating ageng, for the preparation of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was 101.14kcal/mol. As a result of the analysis of DTA & XRD, it was confirmed that the crytallization of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was the most efficient when 6.05% TiO2, nucleating agent, was added. $\beta$-eucryptite solid solution crystals and $\beta$-spodumene solid solution crystals were detected in the sample heat treated above 85$0^{\circ}C$. The sintered gel heat treated at 85$0^{\circ}C$ had the specific surface area of 185$m^2$/g, the pore volume of 0.19cc/g and the average pore radius of 20.8$\AA$. This shows that the sintered gel is also comparatively porous material. In temperature range of 25~85$0^{\circ}C$ thermal expansion coefficient of the specimen which was crystallized for 10hrs at 85$0^{\circ}C$ was 6.7$\times$10-7/$^{\circ}C$, which indicated that the crystallized specimen was turned out to be the glass-ceramic with low thermal expansion.

• Journal of Electrochemical Science and Technology
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• 제8권2호
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• pp.101-106
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• 2017

$Li_2SiO_3$ was used as a coating material to improve the electrochemical performance of $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$. $Li_2SiO_3$ is not only a stable oxide but also an ionic conductor and can, therefore, facilitate the movement of lithium ions at the cathode/electrolyte interface. The surface of the $Li_2SiO_3$-coated $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ was covered with island-type $Li_2SiO_3$ particles, and the coating process did not affect the structural integrity of the $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ powder. The $Li_2SiO_3$ coating improved the discharge capacity and rate capability; moreover, the $Li_2SiO_3$-coated electrodes showed reduced impedance values. The surface of the lithium-ion battery cathode is typically attacked by the HF-containing electrolyte, which forms an undesired surface layer that hinders the movement of lithium ions and electrons. However, the $Li_2SiO_3$ coating layer can prevent the undesired side reactions between the cathode surface and the electrolyte, thus enhancing the rate capability and discharge capacity. The thermal stability of $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ was also improved by the $Li_2SiO_3$ coating.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(2)
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• pp.195-200
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• 1997

핵융합로 증식재용 r-LiAlO$_2$, Li$_2$ZrO$_3$, Li$_2$TiO$_3$ 분말을 자발착화 연소반응법으로 합성하였다. LiAlO$_2$와 달리 Li$_2$ZrO$_3$ 와 Li$_2$TiO$_3$는 가열하는 동안 침전물이 생겼지만 카르복실산기만을 지닌 구연산과 아민기만을 지닌 우레아를 화학정량의 조성으로 혼합한 연료로 쉽게 분말을 합성할 수 있었다. LiAlO$_2$나 Li$_2$TiO$_3$분말은 별도의 하소 공정이필요없이 원하는 결정상이 형성되었으며, Li$_2$ZrO$_3$분말은 Li이 과량인 상이 형성되므로 110$0^{\circ}C$에서 하소하여 원하는 상을 얻었다. 합성된 Li계 산화물 분말은 비표면적 10~17 $m^2$/g으로 약 150 nm정도의 입자크기를 갖는 미세한 입자이었다.