• 전기화학회지
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• 제6권3호
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• pp.187-195
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• 2003

The present article is concerned with the overview of carbonaceous materials used as anode materials for lithium ion secondary batteries. This article first classified carbonaceous materials into graphite, soft carbon and hard carbon according to their crystal structures, and then summarised the previous works on the characteristics of lithium intercalation/deintercalation into/from the carbonaceous materials. Finally this article reviewed our recent research works on the mechanism of lithium transport through graphite, soft carbon and hard carbon electrodes from the kinetic view point by the analysis of the theoretical and experimental potentiostatic current transients.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3675-3678
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• 2010

In-situ X-ray absorption spectroscopy (XAS) was used to elucidate the structural variation of $\alpha-MoO_3$ electrode upon discharge/charge reaction in a lithium ion battery. According to the XAS analysis, hexavalent Mo atoms in $\alpha-MoO_3$ framework are reduced as the amount of intercalated lithium ions increases. As lithium de-intercalation proceeds, most of pre-edge peaks are restored again. However, according to the Fourier transforms of the extended X-ray absorption fine structure (EXAFS) spectra, lithium de-intercalation reaction is partially irreversible upon the charge reaction, which is one of the main reasons why the capacity of $\alpha-MoO_3$ electrode decreases upon successive discharge/charge cycles.

• Bulletin of the Korean Chemical Society
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• 제22권4호
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• pp.367-371
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• 2001

Lithium inserted into artificial carbon has been synthesized as a function of the Li concentration. The characteristics of these prepared compounds were determined from the studies using X-ray diffraction(XRD), solid nuclear magnetic resonance (NM R) spectrophotometric and differential scanning calorimeter(DSC) analysis. X-ray diffraction showed that lower stage intercalation compounds were formed with increasing Li concentration. In the case of the AG3, most compounds formed were of the stage 1 structure. Pure stage 1 structural defects of artificial graphite were not observed. 7Li-NMR data showed that bands are shifted toward higher frequencies with increasing lithium concentration; this is because non-occupied electron shells of Li increased in charge carrier density. Line widths of the Li inserted carbon compounds decreased slowly because of nonhomogeneous local magnetic order and the random electron spin direction for located Li between graphene layers. The enthalpy and entropy changes of the compounds can be obtained from the differential scanning calorimetric analysis results. From these results, it was found that exothermic and endothermic reactions of lithium inserted into artificial carbon are related to the thermal stability of lithium between artificial carbon graphene layers.

• 전기화학회지
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• 제5권2호
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• pp.86-92
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• 2002

속도론적 관점에서 키네틱 몬테 카를로 방법의 전기화학적 리튬 인터칼레이션에로의 응용에 대하여 다루었다. 우선 키네틱 몬테 카를로 방법과 전이상태이론의 기본 개념을 소개하였고, 확산거동을 평가하기 위한 시뮬레이션 과정을 설명하였다. 마지막으로 인터칼레이션 화합물중 $LiMn_2O_4$전극에 대해 전류 추이곡선과 선형 포텐셜 전류곡선을 해석하기 위해서 전이상태이론에 근거한 키네틱 몬테 카를로 방법을 셀-저항 제어조건하에서 사용하였다. 이로부터 키네틱 몬테 카를로 방법이 전기화학분야에서 리튬 인터칼레이션의 속도론적 연구에 매우 유용함을 알 수 있었다.

• 전기화학회지
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• 제5권4호
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• pp.178-182
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• 2002

The electrochemical behavior of binder-free carbon anode, comprising of only artificial and natural graphite (AG and NG) particles, for intercalation and deintercalation of lithium ion $(Li^+)$ in aluminum chloride (AICI_3)-I-ethyl­3-methylimidazolium chloride (EMIC)-lithium chloride (LiCl)-thionyl chloride $(SOCI_2)$ room-temperature molten salt (RTMS) was studied. Binder-free carbon electrodes were fabricated using electrophoretic deposition (EPD) method. The binder-free carbon anodes provided a relatively flat charge and discharge potentials $(0\;to\;0.2V\;vs.\;Li/Li^+)$ and current capabilities $(250-340mAh{\cdot}g^{-1})$ for the intercalation and deintercalation of $Li^+$. Stability of the binder-free carbon anodes for intercalation and deintercalation of 50 cycles was confirmed.

• 전기화학회지
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• 제16권2호
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• pp.81-84
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• 2013

We demonstrate rutile $TiO_2$ branched nanostructure ($TiO_2$-BN) electrodes synthesized by seeding method for enhanced lithium intercalation properties. The morphology and crystalline nature of the $TiO_2$-BN were clearly observed by field-emission transmission electron microscopy and fast Fourier transform pattern. The $TiO_2$-BN electrodes showed excellent capacity and high rate performance. The improved lithium-ion intercalation properties of the $TiO_2$- BN may be attributed to relatively large specific surface area and short transport distance of the branched nanostructure.

• Carbon letters
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• 제1권3_4호
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• pp.129-132
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• 2001

Carbonaceous thin films were prepared from acetylene and argon gases by plasma assisted chemical vapor deposition (Plasma CVD) at 873 K. The carbonaceous thin films were characterized by mainly Raman spectroscopy, and their electrochemical properties were studied by cyclic voltammetry and charge-discharge measurements in propylene carbonate (PC) solution. Raman spectra showed that crystallinity of carbonaceous thin films is correlated by the applied RF power. The difference of the applied RF power also affected on the results of cyclic voltammetry and charge-discharge measurements. In PC solution, intercalation and de-intercalation of lithium ion can occur as well as in the mixed solution of EC and DEC.

• Bulletin of the Korean Chemical Society
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• 제10권1호
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• pp.27-30
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• 1989

Lithium has been intercalated into $FeMoO_4Cl$, and deintercalated from $LixFeMoO_4Cl$ both electrochemically and chemically. The inserted $Li^+$ ions are stabilized in the distorted octahedral field in interlayer space of $FeMoO_4Cl$. The crystal symmetry is reduced from tetragonal to monoclinic due to the reduction of ferric to ferrous ions in $LixFeMoO_4Cl$ upon lithium intercalation. From the magnetic and structural data, it has been concluded that the high-spin electronic configuration of $Fe^{2+}(d_{xz}^2{d_{y2}^1}{d_1}{2d_z^12}{\cdot}_y2)$, corresponding to $^5E_g$, group term in $D_{4h}$ symmetry, can be stabilized by the elongation of $FeO_4Cl_{2-}$octahedra in a weak ligand field.

• 전기화학회지
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• 제5권4호
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• pp.173-177
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• 2002

Electrochemical characteristics of a graphite/lithium and a $LiCoO_2/lithium$ half cell and a $graphite/LiCoO_2$ full cell were analyzed using a GCSOC (gradual control test of the state of charge) technique. The IIE (initial intercalation coulombic efficiency), which represents lithium intercalation property of the electrode material, and the $lIC_s$ (initial irreversible capacity by the surface), which represents irreversible reaction between the electrode surface and the electrolyte were obtained from the GCSOC analysis. Linear-fittable capacity ranges of IIE of graphite and $LiCoO_2$ electrodes were 370 and 150 mAh/g, respectively, based on material weight. The value of lIE for graphite and $LiCoO_2$ electrodes were $93-94\%$ and $94-95\%$, respectively. The value of IICs for graphite and $LiCoO_2$ electrodes were 15-17 mAh/g and 0.3-1.7 mAh/g, respectively. The value of IIE for $graphite/LiCoO_2$ full cell, used GX25 and DJG311 as a graphite, was $89-90\%$ that lower than that for the half cells. Parameters of IIE and IICs can also be used to represent not only half cell but also full cell.

• 공업화학
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• 제8권6호
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• pp.1022-1028
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• 1997

본 연구에서는 1M $LiClO_4/PC$ 유기 용액 중에 존재하는 리튬 이온의 층간 반응에 의하여 전기 발색 현상을 나타내는 전자-선 증발법으로 제조된 비정질의 텅스텐 산화물 박막과 전해질 계면에서의 전기화학적 특성들을 연구하기 위하여 음극 Tafel 분극법, 순환 전류-전위법 및 전기량 적정법 등의 전기화학 측정법과 X선 회절 분석법을 이용한 박막의 결정 상태 조사 등이 수행되었다. 특히 다중 순환 전류-전위 곡선으로부터 리튬 이온의 층간 반응은 발색 반응에 대한 인가 과전압이 약 1.0V 이내에서는 안정된 소 발색의 가역적 현상을 나타내었으나, 발색 반응에 대한 인가 과전압이 1.5V일 때는 발색 시 삽입된 박막 내부의 리튬이 소색 시 완전히 빠져 나오지 못하여, 박막 내부에 리튬이 축적되는 현상을 나타내었으며, 적은 순환 횟수임에도 불구하고 소 발색의 전류 밀도가 감소되는 것이 조사되어 발색에 필요한 인가 과전압의 한계가 존재함을 알 수 있었다.