• Journal of Electrochemical Science and Technology
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• 제7권2호
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• pp.170-178
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• 2016

Composited molybdenum oxide and amorphous carbon (MoO₃/C) as anode material for lithium ion batteries has been successfully synthesized by calcining polyaniline (PANI) doped with ammonium heptamolybdate tetrahydrate (AMo). The as prepared electrode material was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscopy (FE-SEM). The electrochemical performance of the anode was investigated by galvanostatic charge/discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The MoO₃/C shows higher specific capacity, better cyclic performance and rate performance than pristine MoO₃ at room temperature. The electrochemical of MoO₃/C properties at various temperatures were also investigated. At elevated temperature, MoO₃/C exhibited higher specific capacity but suffered rapidly declines. While at low temperature, the electrochemical performance was mainly limited by the low kinetics of lithium ion diffusion and the high charge transfer resistance.

• Macromolecular Research
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• 제15권2호
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• pp.114-128
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• 2007

Polyimides are one of the most important classes of polymers used in the microelectronics and photoelectronics industries. Because of their high thermal stability, chemical resistance, and good mechanical and electric properties, polyimides are often applied in photoresists, passivation and dielectric films, soft print circuit boards, and alignment films within displays. Recently, fully aliphatic and alicyclic polyimides have found applications as optoelectronics and inter layer dielectric materials, due to their good transparencies and low dielectric constants $(\varepsilon)$. The low molecular density, polarity and rare probability of forming inter- or intra-molecular charge transfers, resulting in lowering of the dielectric constant and high transparency, are the most striking characteristics of aliphatic polyimide. However, the ultimate end use of polyimides derived from aliphatic monomers is in their targeted applications that need less stringent thermal requirements. Much research effort has been exerted in the development of aliphatic polyimide with increased thermal and mechanical stabilities, while maintaining their transparencies and low dielectric constants, by the incorporation of rigid moieties. In this article, the recent research process in synthesizing fully aliphatic polyimides, with improved dimensional stability, high transparency and low $\delta$values, as well as the characterizations and future scope for their application in micro electric and photo-electronic industries, is reviewed.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2004년도 춘계학술대회
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• pp.247-257
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• 2004

Electrodes were fabricated based on activated carbon powder BP-20, conducting agent such as Super P, vapor grown carbon fiber (VGCF) and acetylene black (AB), and the mixed binders of flexible poly(vinylidenefluoridehexafluoropropylene) [P(VdF-co-HFP)] and cross linking dispersion agent of polyvinylpyrrolidone (PVP) to increase mechanical strength. According to impedance measurement of the electrode with the addition of conducting agent, we found that it was possible to charge rapidly by the fast steady-state current convergence due to low equivalent series resistance (AC-ESR, fast charge transfer rate at interface between electrode and electrolyte and low RC time constant. The self-discharge of unit cell showed that diffusion process was controlled by the ion concentration difference of initial electrolyte due to the characteristics of Electric Double Layer Capacitor (EDLC) charged by ion adsorption in the beginning, but this by current leakage through the double-layer at the electrode/electrolyte interface had a minor effect and voltages of curves were remained constant regardless of electrode material. We found that the 2.3V/230F grade EDLC would be applied to industrial safety usage such as uninterrupted power supply (UPS) because of the constant DC-ESR by IR drop regardless of discharge current.

• 한국전기전자재료학회논문지
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• 제24권10호
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• pp.850-854
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• 2011

Nano-fibers of the $Li[Ni_{1/3}Co_{1/3}Mn_{1/3}]O_2$ electrode were synthesized from a metal oxide precursor using the electrospun method. The XRD patterns of all prepared powders showed a hexagonal ${\alpha}$ - $NaFeO_2$ structure (space group: R-3 m, 166). Scanning electron microscopy showed that all the synthesized samples were comprised of nanofibers with a size of 100~800 nm. Among the samples tested, the calcined $Li[Ni_{1/3}Co_{1/3}Mn_{1/3}]O_2$ nanowires in oxygen heating atmosphere showed a high charge and discharge capacity of 239.22 and 172.81 $mAhg^{-1}$ at the $1^{st}$ cycle, respectively. In addition, the charge transfer resistance was also improved significantly compared to the other samples.

• 한국재료학회지
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• 제32권11호
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• pp.474-480
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• 2022

Lithium-ion batteries (LIBs) are powerful energy storage devices with several advantages, including high energy density, large voltage window, high cycling stability, and eco-friendliness. However, demand for ultrafast charge/discharge performance is increasing, and many improvements are needed in the electrode which contains the carbon-based active material. Among LIB electrode components, the conductive additive plays an important role, connecting the active materials and enhancing charge transfer within the electrode. This impacts electrical and ionic conductivity, electrical resistance, and the density of the electrode. Therefore, to increase ultrafast cycling performance by enhancing the electrical conductivity and density of the electrode, we complexed Ketjen black and graphene and applied conductive agents. This electrode, with the composite conductive additives, exhibited high electrical conductivity (12.11 S/cm), excellent high-rate performance (28.6 mAh/g at current density of 3,000 mA/g), and great long-term cycling stability at high current density (88.7 % after 500 cycles at current density of 3,000 mA/g). This excellent high-rate performance with cycling stability is attributed to the increased electrical conductivity, due to the increased amount of graphene, which has high intrinsic electrical conductivity, and the high density of the electrode.

• Corrosion Science and Technology
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• 제8권2호
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• pp.53-61
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• 2009

본 연구에서는 강교 도장재료로 사용될 수 있는 에폭시 하도 도료를 도포한 시험편을 촉진시험을 통해 열화시킨 후 도막의 외관 평가 및 EIS에 의한 평가를 실시하고, 그 2가지 방법에 대한 비교 분석을 실시하였다. 화상처리 기법에 의해 구한 총 열화 면적율과 열화도 평점 산정 결과를 상호 비교해 본 결과 녹이 발생한 경우가 그렇지 않은 경우보다 열화도 평점이 높게 나타났다. 이는 강교 도장의 열화도 평가 기준에서 단위 열화 면적율당 부여하는 열화도 평점이 박리의 경우보다 녹의 경우가 더 크기 때문이다. 열화 면적율과 EIS 측정 데이터를 비교해 본 결과 녹의 면적율 약 0.1% 이상, 블리스터링의 면적율 약 3% 이상만 되어도 도막의 임피던스는 약 $10^4{\Omega}{\cdot}cm^2$ 혹은 그 이하로 크게 저하되었다. 2개의 시험편을 제외한 모든 시험편에 대해 전하전달저항(charge transfer resistance, $R_{ct}$)과 이중층 정전용량(double layer capacitance, $C_{dl}$) 값이 나타났으며, 이 결과로부터 이들 시험편들은 도막과 강재 계면에 수분이 축적되어 부식이 진행되고 있음을 알 수 있었다. 열화도 평점과 EIS 측정결과를 상호 비교해 본 결과 저주파수(10 mHz)에서의 임피던스 값이 $10^6{\Omega}{\cdot}cm^2$ 이하로 떨어진 경우는 모두 열화도 평점이 10점 이상으로 나타났으며, NORSOK cyclic test 과정에 의해 열화시킨 경우 열화도 평점이 높지 않음에도 불구하고 임피던스는 가장 낮게 나타났다. 이것은 도장계와 열화조건이 주 시험편과 다르기 때문인 것으로 판단되며, 열화조건이 더 가혹하거나 복합적일 경우 외관 상태에 비해 도막의 저항이 더 크게 저하될 가능성이 있다고 생각된다.

• Korean Chemical Engineering Research
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• 제40권6호
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• pp.729-734
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• 2002

본 연구에서 PSS로 도핑된 EB와 LEB 형태의 폴리아닐린 필름을 ITO전극위에 m-cresol, chloroform 혼합용액을 도포시켜 제조하였다. UV 실험결과로부터 m-cresol에 의한 이차 도핑 효과를 확인 할 수 있었으며, m-cresol의 양이 증가할수록 폴리아닐린 필름의 전도도는 증가하였다. 이차도핑에 의한 전도도 향상은 제조된 폴리아닐린과 m-cresol의 상호작용에 의한 것으로 판단된다. 폴리아닐린의 전기화학적 실험결과 LEB로 제작된 폴리아닐린 전극의 산화 환원 피크 전류는 EB로 제작된 폴리아닐린 전극보다 더 크고 가역적인 것을 CV를 통해 구할 수 있었다. 또한 전하전달 저항은 m-cresol의 양이 증가할수록 감소하였으며, LEB/PSS 전극의 전하 전달 저항 값이 EB/PSS 전극보다 작았다. 이것은 CV에서 얻은 경향과 일치하였다. 제조된 폴리아닐린 전극 모두 이중층 용량과 용액저항은 일정하였으며, 용액저항은 주파수에 무관한 인자임을 알 수 있었다. 또한 PSS로 도핑된 폴리아닐린은 가상적인 n형 전도성 고분자의 특성을 나타내었다.

• 대한기계학회논문집B
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• 제38권3호
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• pp.227-234
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• 2014

전기 자동차의 연료 소모량은 배터리 성능에 의존한다. 배터리의 성능은 작동온도에 민감하기 때문에, 배터리 온도 관리는 성능과 내구성을 보장한다. 특히, 배터리 팩에서의 모듈의 온도 분포는 냉각특성에 영향을 미친다. 이 연구는 모듈 사이의 온도 분포를 확인 할 수 있는 배터리 열적 모델링에 초점을 두었다. 본 연구의 배터리 모델은 NiMH 각형 모델이며, 10개의 모듈로 구성되어졌다. 배터리 열 모델은 열 발생, 채널을 통과하는 대류 열 전달 그리고 모듈 사이의 전도 열 전달로 구성되었다. 배터리 내에서 발생되는 열발생 모델은 충/방전 동안의 전기적인 저항열에 의해 계산되어 진다. 모델은 전 하이브리드 자동차의 운전 동안 적절한 열관리의 전략을 결정한다.

• 전기화학회지
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• 제8권3호
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• pp.117-124
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• 2005

Electrochemical oxidation of ethanol at nickel electrodes has been studied in 1 M KOH solution containing 0.20M ethanol using electrochemical impedance spectroscopy. Equivalent circuits have been worked out by simulating the impedance data, and the results were used to model the oxidation of ethanol as well as the passivation of the electrode. The maximum rate of oxidation of $Ni(OH)_2$ to NiOOH was observed at about 0.37V vs. Ag/AgCl reference electrode, while the maximum rate of ethanol oxidation at the Ni electrode was observed at about 0.42V, The charge-transfer resistance for oxidation of the electrode itself became smaller in the presence of ethanol than in its absence. These results suggest that the $\beta-Ni(OH)_2/\beta-NiOOH$ redox couple is acting as an effective electron transfer mediator far ethanol oxidation. The kinetic parameters also were obtained by the experimental and simulated results.

• 반도체디스플레이기술학회지
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• 제17권2호
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• pp.57-60
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• 2018

Recently, Thin-film transistors (TFTs) are fundamental building blocks for state-of-the-art microelectronics, such as flat-panel displays and system-on-glass. Zinc oxide thin films have the advantage that they can grow at low temperature and can obtain high charge movility. Also the zinc oxide thin film can be used to control the resistance according to the oxygen content, so it is very easy to obtain the desired physical properties. In this paper, we fabricated a zinc oxide thin film on a polished copper substrate through a solution process, then improved the crystallinity through a geat treatment porcess, and studied to transfer it on a flexible substrate after the heat treatment was completed.