• 전기화학회지
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• 제7권1호
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• pp.32-37
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• 2004

리튬 이차전지의 음극재료로서 천연흑연의 충방전 속도에 따른 용량특성을 조사하였다 정전류 조건에서 $0.0-2.0V(vs. Li/Li^+)$의 범위에서 충방전 하였을 때, 충전전류가 증가할수록 충전반응의 과전압이 증가하여 $Li^+$이온이 충분히 삽입되지 못한 상태에서 컷오프 전압(0.0 V)에 도달하기 때문에 충전용량은 충전전류의 크기가 클수록 감소하였다. 한편, 방전전류가 증가함에 따라 방전반응의 과전압도 증가하여 0.0-0.3V범위에서 방전반응이 일어나나 방전 컷오프 전압(2.0 V)과는 격차가 커서 $Li^+$이온이 탈리되지 못한 상태에서 방전 컷오프에 도달하는 현상은 없기 때문에 방전용량이 방전전류의 크기에 영향을 받지 않았다. 충전전류가 증가함에 따라 부반응인 리튬 전착반응의 과전압도 증가하므로 충전 컷오프 전압을 0.0V 이하로 낮출 수 있었다. 그러나 $Li^+$이온의 삽입반응에 비해 전착반응의 저항이 적어 충전전류에 따른 전착반응의 과전압 증가에는 한계가 있었다. 1C조건에서 -0.04V까지 충전 z컷오프 전압을 낮추었을 때 리튬의 전착반응은 없었고, 이로부터 약 $11\%$의 방전용량을 증가시킬 수 있었다.

• Journal of Electrochemical Science and Technology
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• 제7권4호
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• pp.306-315
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• 2016

Amorphous vanadium titanates (aVTOs) are examined for use as a negative electrode in lithium-ion batteries. These amorphous mixed oxides are synthesized in nanosized particles (<100 nm) and flocculated to form secondary particles. The $V^{5+}$ ions in aVTO are found to occupy tetrahedral sites, whereas the $Ti^{4+}$ ions show fivefold coordination. Both are uniformly dispersed at the atomic scale in the amorphous oxide matrix, which has abundant structural defects. The first reversible capacity of an aVTO electrode ($295mAhg^{-1}$) is larger than that observed for a physically mixed electrode (1:2 $aV_2O_5$ | $aTiO_2$, $245mAhg^{-1}$). The discrepancy seems to be due to the unique four-coordinated $V^{5+}$ ions in aVTO, which either are more electron-accepting or generate more structural defects that serve as $Li^+$ storage sites. Coin-type Li/aVTO cells show a large irreversible capacity in the first cycle. When they are prepared under nitrogen (aVTO-N), the population of surface hydroxyl groups is greatly reduced. These groups irreversibly produce highly resistive inorganic compounds (LiOH and $Li_2O$), leading to increased irreversible capacity and electrode resistance. As a result, the material prepared under nitrogen shows higher Coulombic efficiency and rate capability.

• 한국표면공학회지
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• 제42권1호
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• pp.8-12
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• 2009

Electronic structures and chemical bonding of Li-intercalated $LiTiS_2$ and $LiTiO_2$ were investigated by using discrete variational $X{\alpha}$ method as a first-principles molecular-orbital method. ${\alpha}-NaFeO_2$ structure is the equilibrium structure for $LiCoO_2$, which is widely used as a commercial cathode material for lithium secondary battery. The study especially focused on the charge state of Li ions and the magnitude of covalency around Li ions. The average voltage of lithium intercalation was calculated using pseudopotential method and the average intercalation voltage of $LiTiO_2$ was higher than that of $LiTiS_2$. It can be explained by the differences in Mulliken charge of lithium and the bond overlap population between the intercalated Li ions and anions in $LiTiO_2$ as well as $LiTiS_2$. The Mulliken charge, which means the ionicity of Li atom, was approximately 0.12 in $LiTiS_2$ and the bond overlap population (BOP) indicating the covalency between Ti and S was about 0.339. One the other hands, the Mulliken charge of lithium was about 0.79, which means that Li is fully ionized. The BOP, the covalency between Ti and O, was 0.181 in $LiTiO_2$. Because of high ionicity of Li and the weak covalency between Ti and the nearest anion, $LiTiO_2$ has a higher intercalation voltage than that of $LiTiS_2$.

• 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.

• 청정기술
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• 제20권2호
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• pp.166-170
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• 2014

강산성 양이온 교환수지를 충전한 고정층 컬럼을 사용하여 수중의 리튬이온을 제거하는 연속식 실험을 수행하였다. 층 높이, 유입 유량 및 유입 농도와 같은 파라미터들을 살펴보았으며, 파과곡선으로부터 파과시간($t_{0.05}$), 포화시간($t_{0.95}$) 및 제거된 리튬이온의 총량(mtotal)을 구하였다. 실험 결과 $t_{0.05}$와 $t_{0.95}$는 층 높이가 감소함에 따라 감소하였고, 유입 농도와 유입 유량이 증가함에 따라 감소하였다. mtotal은 유입 유량과 층 높이가 증가함에 따라 증가하였지만, 유입 유량이 증가함에 따라서는 감소하였다. 실험자료를 토마스 모델식과 윤-넬슨 모델식을 적용한 결과, 토마스 모델식이 파과 데이터에 잘 부합하였다.

• 한국수소및신에너지학회논문집
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• 제23권4호
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• pp.353-363
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• 2012

The relationship between the diffusivity and electrochemical characteristics of lithium secondary battery with the modified Si anode material prepared in HF/$AgNO_3$ solution was investigated. The crystallographic structure and images of the modified porous Si and modified Si/Cu was examined using the X-ray diffraction, BET and SEM. To examine the effect of metal composite and pore size distribution according to chemical etching on the electrochemical characterization, the electrodes for half cells were prepared with the modified Si, modified Si/Cu, and modified Si/Cu annealed with $600^{\circ}C$. Our results showed that the chemical diffusivity of lithium ions was related to structure and resistance of Si/Cu composite anode material. The lithium diffusivity in modified silicon compound calculated from the CV was at the range of $1{\times}10^{-12}$ to $9{\times}10^{-16}cm^2/s$. The effects of modified silicon structure and resistance on the cycling efficiency were significant.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.869-876
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• 2018

The force of a direct current (DC) electromagnetic pump used to transport liquid lithium was analyzed to optimize its geometrical and electrical parameters by numerical simulation. In a heavy-ion accelerator, which is being developed in Korea, a liquid lithium film is utilized for its high charge-stripping efficiency for heavy ions of uranium. A DC electromagnetic pump with a flow rate of $6cm^3/s$ and a developed pressure of 1.5 MPa at a temperature of $200^{\circ}C$ was required to circulate the liquid lithium to form liquid lithium films. The current and magnetic flux densities in the flow gap, where a $Sm_2Co_{17}$ permanent magnet was used to generate a magnetic field, were analyzed for the electromagnetic force distribution generated in the pump. The pressure developed by the Lorentz force on the electromagnetic force was calculated by considering the electromotive force and hydraulic pressure drop in the narrow flow channel. The opposite force at the end part due to the magnetic flux density in the opposite direction depended on the pump geometrical parameters such as the pump duct length and width that defines the rectangular channels in the nonhomogeneous distributions of the current and magnetic fields.

• 한국전자통신학회논문지
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• 제18권1호
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• pp.195-204
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• 2023

드론의 배터리 시스템은 리튬이온 또는 리튬폴리머 배터리를 사용하는데, 드론 사용 후 폐기 과정에서 화재 원인은 폐기되는 배터리에서 발생하는 가연성 가스인 것으로 알려졌다. 폐기공정에 들어간 배터리는 대부분 산소가 발생했지만 미량의 가연성 가스도 발생했고, 처리에 사용된 장비에서도 다량의 염소 이온과 황산염이 검출됐다. 이를 조기에 감지하는 시스템이 구성된다면 폐기 배터리로 인한 사고 위험을 줄일 수 있을 것이다.

• 한국세라믹학회지
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• 제18권2호
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• pp.91-98
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• 1981

Synthetic zeolite A was prerared from domestic Hadong kaolin with sodium hydroxide solution and their ion exchange isotherms of $K^+$, $NH^{4+}$, $Li^+$ and $Ag^+$ ion were presented. The optimum reaction conditions for synthetic zeolite A from calcinated kaolin were 2 fold excess of 2N sodium hydroxide solution, 10$0^{\circ}C$ and 8 hours. It was observed that before the crystallization of zeolite A the samples reacted with sodium hydroxide solution had rather higher ion exchange capacities than zeolite A. The $K^+$-$Na^+$ and $Ag^+$$Na^+$ ion exchange isotherms were signoidal. The initial selectivity series was in the order $Ag^+$$K^+$>$Na^+$>$NH_4$>$Li^+$. Between approximately 33 and 67% replacement of soium ions the selectivity series became $Na^>$ and above 67% became $Ag^+$>$K^+$. Evidence were also presented to demonstrate that 8 out of 12 sodium ions per pseudo unit cell were not easily replaceable by lithium ions and 4 out of 12 not easily replaceable by ammonium ions.

• Carbon letters
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• 제28권
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• pp.1-8
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• 2018

Graphene is a single atomic layer of carbon atoms, and has exceptional electrical, mechanical, and optical characteristics. It has been broadly utilized in the fields of material science, physics, chemistry, device fabrication, information, and biology. In this review paper, we briefly investigate the ideas, structure, characteristics, and fabrication techniques for graphene applications in lithium ion batteries (LIBs). In LIBs, a constant three-dimensional (3D) conductive system can adequately enhance the transportation of electrons and ions of the electrode material. The use of 3D graphene and graphene-expansion electrode materials can significantly upgrade LIBs characteristics to give higher electric conductivity, greater capacity, and good stability. This review demonstrates several recent advances in graphene-containing LIB electrode materials, and addresses probable trends into the future.