• Journal of the Korean Electrochemical Society
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• v.16 no.1
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• pp.9-18
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• 2013

Components of zinc-air battery and their problems are explained. Energy density of zinc air battery is superior to other commercial ones including Li-ion batteries. Cycle life of the zinc air batteries is poor because of irreversible redox reactions on both electrodes. In order to improve the performance of the zinc air battery, catalysts, passivation, and the new structure of electrodes should be developed to optimize several reactions in an electrode. Multidisciplinary efforts, such as mechanics, corrosion science, composite materials are necessary from the beginning of the research to obtain a meaningful product.

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.753-756
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• 2011

지속적인 충/방전에 의하여 표준 수명 보다 더 빠른 노화 현상을 일으키는 배터리의 효율적인 관리를 위하여, 배터리의 내부 상태를 모니터링 하였다. 정확한 배터리 모니터링을 위해서 해당하는 배터리의 잔존 용량 및 잔존 수명을 정확히 예측할 수 있어야 하며, 이를 위해 Open Voltage를 사용한 실험, 에너지 보존 법칙에 의한 충전 전류 측정법, 시동 시 최대 전류와 내부 저항의 변화량을 알아내는 실험을 하였다. Open Voltage 실험 결과, SOC수치에 따른 특정 전압의 범위를 알 수 있었고, 이 전압은 온도에 의해 변동된다는 것을 확인할 수 있었다. 충전 그래프를 그려본 결과 충전횟수와 완충에 걸리는 시간은 반비례하며, 배터리 내부에 충전되는 총 전류의 양과도 관계가 있었다. 시동 실험에서는 최저 전압 드롭 값과 최대 공급 전류의 범위를 알 수 있었으며, 특정 SOC 구간 내 내부 저항의 값을 차이를 알 수 있었다. 이 값들은 각 SOC의 수치에 비례한 결과를 보였다. 이 결과들을 정리하여, 배터리 내부 상태를 예측하는 방법을 제안하고자 한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.186.2-186.2
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• 2014

최근 친환경 에너지에 대한 관심이 증폭되면서 리튬이차전지에 대한 연구가 활발히 진행되고 있다. 특히 음극(anode) 물질의 경우 기존의 흑연(graphite)보다 이론적 용량이 약 10배 이상 높은 실리콘(Silicon)에 대한 관심이 매우 높다. 하지만 Si의 경우 리튬 충전거동 시 400% 이상의 부피팽창으로 몇 번의 충전/방전 싸이클(cycle)에 전극이 파괴되는 문제점을 지니고 있다. 이를 극복하기 위해 Si 나노선이 고려되고 있다. 우수한 전극특성을 갖는 Si 소재를 개발하기 위해서는 원자단위에서 Si 나노선의 리튬 충전 메커니즘을 살펴보는 것이 매우 중요하다. 하지만 기존의 시뮬레이션 기법으로는 Si 나노선의 볼륨팽창에 관한 메커니즘과 리튬 충전과정에서의 상변화(결정질에서 비정질) 과정을 설명하기는 기술적으로 매우 힘들다. 고전적인 분자동역학 방법의 경우 실제 나노스케일을 고려할 수 있지만, empirical potential로는 원자들간의 화학반응을 제대로 묘사할 수 없다. 한편 양자역학에 기반을 둔 제일원리방법의 경우 계산의 복잡성으로 현재의 컴퓨터 환경에서는 나노스케일에서 원자들의 동역학적인 거동을 연구하기 매우 힘들다. 우리는 이러한 문제를 해결하기 위해 실제 나노스케일에서 원자간 화학반응을 예측할 수 있는 Si-Li 시스템의 Reactive force field를 개발하였고, 분자동역학 계산방법을 이용하여 Si 나노선의 Li 충전 메커니즘을 규명하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.3
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• pp.188-196
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• 2009

Due to its high power density, long cycle life and clean nature supercapacitors are widely used for improving the dynamic characteristics of the new and renewable energy sources and extending the battery run-time and life. In this paper improved dynamic model of the supercapacitor is developed by the electrochemical impedance spectroscopy technique. The developed model can be used to accurately estimate the dynamic behaviour of the supercapacitor and calculate the exact capacitance value at a certain state of charges. The model of the supercapacitor in the frequency domain is equivalently transformed into that in the time domain for Matlab/Simulink simulaton. The simulation data shows fine agreements with experimental results, thereby proving the validity and the accuracy of the developed model.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.283-291
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• 2010

In this review, the studies on the electrochemical properties of $TiO_2$ nanotube as an anode material of lithium-ion battery, which was prepared by an alkaline hydrothermal reaction and anneling process, were investigated andanalyzed in terms of charge-dischage characteristics. Up to date, a maximum discharge capacity of $338mAh\;g^{-1}$(x=1.01) was achieved by the nanotube with $TiO_2(B)$ phase, whereas the theoretical capacity of $TiO_2$ anode was $335mAh\;g^{-1}$(x=1) in the basis of $Li_xTiO_2$ as a product of electrochemical reaction between $TiO_2$ and lithium. This was due to fast lithium transport by a shortened diffusion path provided by controlling the nanostructure of $TiO_2$, because the self-diffusion of lithium was slow in a basis of its activation energy as 0.48 eV. Due to an excellent ion storage capabilities in both the surface and the bulk phase, the $TiO_2$ nanotube could be a promising active material as both an anode of lithium-ion battery and an electrode of capacitor with high-rate performances.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.42-48
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• 2021

Zn and Al added LiNi0.85Co0.15O2 cathode materials were synthesized to improve electrochemical properties and thermal stability using a solid-state route. Crystal structure, particle size and surface shape of the synthesized cathode materials was measured using XRD (X-ray diffraction) and SEM (scanning electron microscopy). CV (cyclic voltammetry), first charge-discharge profiles, rate capability, and cycle life were measured using battery cycler (Maccor, series 4000). Strong binding energy of Al-O bond enhanced structure stability of cathode material. Electrochemical properties were improved by preventing cation mixing between Li+ and Ni2+. Large ion radius of Zn+ increased lattice parameter of NC cathode material, which meant unit-cell volume was expanded. NCZA25 showed 80% of capacity retention at 0.5 C-rate during 100 cycles, which was 12% higher than that of NC cathode. The discharge capacity of NCZA25 showed 104 mAh/g at 5 C-rate. NCZA25 achieved 36 mAh/g more capacity than that of NC cathod. NCZA25 cathode material showed excellent rate capability and cycling performance.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.3
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• pp.27-34
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• 2023

In this study, various plant-based biomass are recycled into carbon materials to employ as anode materials for lithium-ion batteries. Firstly, various biomass of rice husk, chestnut, tea bag, and coffee ground are collected, washed, and ground. The carbonization process is followed under a nitrogen atmosphere at 850℃. The morphological and chemical properties of materials are investigated using FE-SEM, EDS, and FT-IR to compare the characteristic differences between various biomass. It is noticeable that biomass-derived carbon materials vary in shape and degree of carbonization depending on their precursor materials. These materials are applied as anode materials to measure the electrochemical performance. The specific capacities of rice husk-, chetnut-, tea bag-, and coffee ground-derived carbon materials are evaluated as 65.8, 80.2, 90.6, and 104.7 mAh g^-1 at 0.2C. Notably, coffee ground-based carbon exhibited the highest specific capacity owing to the difference in elemental composition and the degree of carbonization. Conclusively, this study suggests the possibility of utilizing as energy storage devices by employing various plant-based biomass into active materials for anodes.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1088-1095
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• 2018

In this study, reduced graphene oxide/polyaniline composite was fabricated tomaximize their advantages with electrochemical performances and use as a electrodematerial for supercapcaitor. Polyaniline as an electrode material was synthesized bychemical polymerization of aniline monomer and reduced graphene oxide wasintroduced to prepare composite with polyaniline without any pre-treatment. Thereduced graphene oxide, polyaniline and their composite electrodes were fabricatedon gold coated PET(polyethylene terephthalate) substrate through spray coatingmethod which can also apply to industrial scale. we have also prepared reducedgraphene oxide and polyaniline single material electrode to compare theirelectrochemical properties with reduced graphene oxide/polyaniline composite electrode. We have analyzed and compared electrochemical properties of eachelectrodes by using cyclic voltammetry(CV), galvanostaticcharge-discharge(GCD) and electrochemical impedancespectroscopy(EIS) at same condition. As a result, reduced graphene oxide /polyaniline composite electrode showed higher capacitance value more thanpolyaniline and reduced graphene oxide electrode, respectively. Internal resistanceof reduce graphene oxide/polyaniline composite electrode was 24% and 58% lessthan polaniline and reduced graphene oxide electrode respectively. These resultsconsidered that reduced graphene oxide/polyaniline composite electrode has potential ability and enable to apply flexible energy storage and wearable devices.

• Journal of the Korean Electrochemical Society
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• v.14 no.4
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• pp.201-207
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• 2011

Supercapacitor has been studied actively as one of the most promising electrochemical energy storage system for a wide range of applications. To increase the energy density of supercapacitor, the introduction of ionic liquids is required. In this study, two types of EMI-$BF_4$ based on quaternary imidazolium salt were prepared with quaternary reaction and anion exchange. The structural characterization and thermal stability were analyzed by nuclear magnetic resonance($^1H$-NMR) and thermogravimetric analysis(TGA), respectively. Thermal stability of the EMI-$BF_4$ using TGA confirmed that, after heat treatment, the decomposition temperature of EMI-$BF_4$ was increased. Supercapacitors were fabricated with synthesized and commercial ionic liquids, and charge/discharge characteristics were also investigated. The capacity of supercapacitor, for synthesized and commercial EMI-$BF_4$ were determined to be 0.067 F and 0.073 F respectively, by means of charge/discharge test.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.325-333
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• 2007

[ $LiNi_{0.995}Al_{0.005}O_2$ ], $LiNi_{0.990}Ti_{0.010}O_2$ and $LiNi_{0.0990}Al_{0.005}Ti_{0.005}O_2$ were synthesized with a combustion method by calcining in an $O_2$ stream at $750^{\circ}C$ for 36 h. The X-ray diffraction patterns of these synthesized samples showed $-NaFeO_2$ structure of rhombohedral system(space group; $R{\bar{3}}\;m$) with no evidence of impurities. Among these samples, $LiNi_{0.995}Al_{0.005}O_2$ exhibited comparatively high first discharge capacity and discharge capacity, and the best cycling performance. $LiNi_{0.995}Al_{0.005}O_2$ had the first discharge capacity of 165.2 mA h/g and a discharge capacity of 116.7 mA h/g at the 50th cycle at 0.1C rate. It showed the first discharge capacity of 141.0 mA h/g and a discharge capacity of 93.5 mA h/g at the 50th cycle at 0.5C rate.