• 전기화학회지
• /
• 제10권1호
• /
• pp.20-24
• /
• 2007

최근 높은 에너지 밀도를 갖고 있는 리튬 이온 이차전지에 대한 관심이 높다. 리튬 이온 이차전지는 이미 휴대용 기기로 널리 적용되고 있으며, 하이브리드 전기자동차와 같은 고출력 전지시스템에 적용을 위해 연구되고 있다. 리튬 이온 이차전지의 전극 소재는 리튬 이온의 이동에 의해서 충전 및 방전되는 현상을 활용한다. 전극으로부터 리튬 이온이 이동될 때 전극내의 구조 변화가 발생한다. 전극의 구조분석은 중성자 또는 X-선을 이용하여 분석할 수 있다. X-선은 분석 시간이 짧고, 쉽게 분석할 수 있다는 장점이 있으나 원자내의 전자구름과의 산란을 응용하므로 전자가 적은 가벼운 원소의 경우 분석이 어려운 단점이 있다. 리튬도 원자량이 작아서 X-선 만으로는 리튬의 정확한 위치에 대한 분석이 어렵다. 중성자 분석기술은 이에 대한 해답이 될 것이다. 본 자료에서는 중성자를 활용한 전극물질의 구조 분석 사례 및 그 원리에 대해서 논의하고자 한다.

• Journal of Electrochemical Science and Technology
• /
• 제12권4호
• /
• pp.458-464
• /
• 2021

Lithium ion batteries (LIBs) is a kind of rechargeable secondary battery, developed from lithium battery, lithium ions move between the positive and negative electrodes to realize the charging and discharging of external circuits. Zeolitic imidazolate frameworks (ZIFs) are porous crystalline materials in which organic imidazole esters are cross-linked to transition metals to form a framework structure. In this article, ZIF-67 is used as a sacrificial template to prepare nano porous carbon (NPC) coated cobalt nanoparticles. The final product Co/NPC composites with complete structure, regular morphology and uniform size were obtained by this method. The conductive network of cobalt and nitrogen doped carbon can shorten the lithium ion transport path and present high conductivity. In addition, amorphous carbon has more pores that can be fully in contact with the electrolyte during charging and discharging. At the same time, it also reduces the volume expansion during the cycle and slows down the rate of capacity attenuation caused by structure collapse. Co/NPC composites first discharge specific capacity up to 3115 mA h/g, under the current density of 200 mA/g, circular 200 reversible capacity as high as 751.1 mA h/g, and the excellent rate and resistance performance. The experimental results show that the Co/NPC composite material improves the electrical conductivity and electrochemical properties of the electrode. The cobalt based ZIF-67 as the precursor has opened the way for the design of highly performance electrodes for energy storage and electrochemical catalysis.

• Bulletin of the Korean Chemical Society
• /
• 제28권12호
• /
• pp.2299-2302
• /
• 2007

A series of quaternary ammonium-based ionic liquids (ILs) containing an alkyl carbonate group on the cation was first prepared and their physical and electrochemical properties including density, viscosity, thermal stability, electrochemical stability, and ionic conductivity were reported. These ILs exhibited wide electrochemical windows of at least 5.0 V and relatively high conductivities. In contrast to dialkyl-substituted ionic liquids, the ILs with an alkyl carbonate group on the cation showed much smaller drop in conductivities when mixed with a lithium salt, due to the interaction of lithium ions with carbonate groups. Upon interaction with a Li salt, the carbonyl stretching frequency of the carbonate group shifted to a lower frequency whereas the peak associated with C-O single bond moved to a higher frequency.

• 한국세라믹학회지
• /
• 제37권10호
• /
• pp.955-961
• /
• 2000

사티탄산칼륨을 리튬이온 전지의 양극재료로써 사용하고자 할 때 사티탄산칼륨의 합성 열처리 온도가 리튬이온 치환량에 미치는 영향에 대해 조사하였다. 사티탄산칼륨은 $K_2$O와 TiO$_2$의 몰 비를 1 : 3.91로 칭량하여 95$0^{\circ}C$, 100$0^{\circ}C$, 105$0^{\circ}C$에서 각각 합성하였다. 그 후, 사티탄산칼륨의 (Ti$_4$O$_{9}$ )$^{2-}$ 층간에 존재하는 $K^{+}$ 이온을 H$^{+}$ 이온으로 치환하고 이것을 다시 Li$^{+}$ 이온으로 치환하였다. 사티탄산칼륨의 합성 열처리 온도가 증가할수록 사티탄산칼륨의 (Ti$_4$O$_{9}$ )$^{2-}$ 층간의 거리가 감소했고 사티탄산칼륨의 길이가 증가했다. 95$0^{\circ}C$에서 열처리된 사티탄산칼륨의 리튬이온 치환량이 가장 많았다. 이는 상대적으로 낮은 합성 열처리 온도에서 사티탄산칼륨의 (Ti$_4$O$_{9}$ )$^{2-}$ 층간의 거리가 넓어져 리튬이온의 층간 이동이 쉬어졌고, 고온에서 열처리되어 길이가 긴 사티탄산칼륨에 비해 저온에서 열처리된 사티탄산칼륨은 길이가 짧아져 리튬이온이 (Ti$_4$O$_{9}$ )$^{2-}$ 층간으로 이동해 가는 거리가 짧아졌으며 아울러 짧은 사티탄산칼륨의 개수가 동일한 무게 당긴 사티탄산칼륨의 개수보다 많으므로 리튬이온의 치환량이 많아진다고 사료된다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.46-46
• /
• 2007

There has been rapid progress in the portable electronics industry. which has led to a great increase for a demand of portable, lightweight power sources. Lithium 2'nd batteries have met these demand. and many studies on the cahtod materials for the lithium 2,nd batteries have been reported during the last decade. Possible candidates for the cathode materials for lithium 2,nd batteries are $LiCoO_2$, $LiNiO_2$, and $LiMn_2O_4$. Currently $LiCoO_2$ is widely used. but $LiMn_2O_4$ is an excellent alternative material in view of its several advantages such a low cost as well as the wasy availability of raw materials and environmental benignity. In this study, find the most suitable synthesis method that satisfied high capacitor and stability cycle character, etc in Li-Mn oxide for 2'nd batteries. And also made an experiment on doping the $LiMn_2O_4$ spinel with a small amount of metal ions has a remarkable effect on the electrochemical properties and characterics of powder, BET, PSA, Porosity, etc.

• Bulletin of the Korean Chemical Society
• /
• 제21권9호
• /
• pp.855-859
• /
• 2000

An application of synergistic solvent extraction for the etermination of trace lithium in sea water has been studied by forming an adduct complex of thenoyltrifluoroacetone (TTA) and trioctylphosphine oxide (TOPO) in a solvent. The interference by major constituents in sea water was eliminated by phosphate precipitation. Ex-perimental conditions such as solution pH, concentrations of TTA and TOPO etc. were optimized in synthetic sea water with similar compositionto its natural counterpart. To eliminate the interference, 1.38g of ammoni-um dihydrogen phosphate and 2.5 mL of ammonia water were added into 100 mL of thediluted solution at $60^{\circ}C$ to form the phosphate precipitates of Ca2+ and Mg2+ ions. After the pH of this filtrate was adjusted to 8.0, 10.0 mL of m-xylene containing 0.1 M TTA and 0.05 M TOPO was added to the solution in a separatory funnel, and the solution was shaken vigorously for 20 minutes. The solvent was separated from the aqueous solution, and 20 uL of m-xylene solution was injected into a gaphite tube to measure the absorbance by GF-AAS. The detection limit was 0.42 ng/mL. Lithium was determined within the range of 146 to 221 ng/mLin Korean coast-al sea waters, and the recoveries in the spiked samples were 94 to 106%.

• 한국결정성장학회지
• /
• 제6권4호
• /
• pp.620-626
• /
• 1996

자체 제작한 고주파 유도 가열 Czochralski 장치를 이용하여 조화용융조성(congruently melting composition)의 undoped 및 MgO.doped 단결정을 육성하였다. 최적육성조건을 확립하였으며, 보상가열전압조정방식을 이용하여 약 ${\pm}5\;%$ 이내의 범위로 직경제어하는데 성공하였다. 또한, 첨가된 $Mg^{2+}$ 이온이 ferroelectric domain 형성에 미치는 영향을 전자현미경(SEM)등으로 분석하였다.

• Corrosion Science and Technology
• /
• 제9권6호
• /
• pp.265-269
• /
• 2010

This paper describes the exfoliation and surface modification of muscovite mica for UV coating formulation. For the exfoliation of the mica, hydrothermal process was used in the presence of lithium nitrate ($LiNO_3$). After the cation exchange with $Li^+$ ions, the surface of the mica was modified with several amphiphilic substances to increase compatibility and storage stability in UV coating formulation. Such a hydrophobic surface modification affected colloidal stability as well as dispersibility of the exfoliated mica in UV coating solution. Anticorrosive property of mica/UV coated steel plates was tested by salt spray test (SST) and compared with sodium montmorillonite ($Na^+$-MMT)/UV coated steel plates.

• 한국세라믹학회지
• /
• 제37권1호
• /
• pp.82-89
• /
• 2000

In lithium silicate photosensitive glass-ceramics, the relationship between lithography time and crystallization, and the effect of addition of mineral acid in etching rate and pattern shape were investigated. Irradiation times for micropatterning were less than 5 minutes in which Ce3+ ions in glass were changed rapidly to Ce4+ with ultra violet light. Overexposure to ultra brought about blot of pattern by diffiraction of light. Addition of mineral acid to HF enhanced etching rate as compared with HF solution only. The addition of H2SO4 especially increased the etching rate by 70%. But the mixed solution also increased the etching rate of the noncrystallized portion of the glass and this resulted in heavy etching. Etching with ultrasonic wave showed higher etching rate than that with the static or fluid method.

• Bulletin of the Korean Chemical Society
• /
• 제22권2호
• /
• pp.189-193
• /
• 2001

The irreversible capacities caused by the reduction of solvent on the surface of a negative electrode (KMFC:Kawasaki Mesophase Fine Carbon) were examined during the initial cycle in ethylene carbonate (EC)-diethyl carbonate (DEC) electrolyte solut ions at various concentrations of LiPF6. Chronopotentiograms, linear sweep voltammograms, and impedance spectra clearly showed differences in irreversible capacity and that those differences are related to the concentration of electrolyte during the initial charge. These differences were caused by the amount of solvent decomposition as a function of the concentration of LiPF6 electrolytic salt. The data are discussed with reference to the concentration of electrolytic salt and the properties of passivation film formed by solvent decomposition.