• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.2
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• pp.5-15
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• 2022

In this study, heated tobacco biomass was prepared as an active material for supercapacitor device. Retrieved tobacco leaf from the heated tobacco was carbonized at various temperature(800/850/950℃). Carbonized tobacco leaf material synthesized at 850℃ exhibited the highest C/O ratio, indicating the finest carbon quality. In addition, polypyrrole was coated onto the carbonized leaf material for increasing the electrochemical performance via low-temperature polymerization method. As-synthesized carbonized leaf material at 850℃(CTL-850)-based electrode and polypyrrole-coated carbonized leaf material(CTL-850/PPy)-based electrode displayed outstanding specific capacitances of 100.2 and 155.3F g^-1 at 1 A g^-1 with opertaing window of -1.0V and 1.0V. Asymmetric supercapacitor device, assembled with CTL-850 as the negative electrode and CTL-850/PPy as the positive electrode, manifested specific capacitance of 31.1F g^-1(@1 A g^-1) with widened operating voltage window of 2.0V. Moreover, as-prepared asymmetric supercapacitor device was able to lighten up the RED Led (1.8V), suggesting the high capacitance and extension of operating voltage window. The result of this research may help to pave the new possibility toward preparing the effective energy storage device material recycling the biomass.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.5
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• pp.167-173
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• 2023

Li₃V₂(PO₄)₃ and Li₃V₂(PO₄)₃/C composite with single phase monoclinic structure for the cathode materials are successfully synthesized by direct co-precipitation method using N₂H₄·H₂O as the reducing agent and alginic acid as the carbon source, and their electrochemical properties were compared. The particles with approximately 1~2 ㎛ size and the uniform spherical-like morphology of the narrow particle size distribution were obtained. In addition, the residual carbon can also improve the electrical conductivity. The Li₃V₂(PO₄)₃/C composite has improved initial specific discharge capacity and excellent cycle characteristics to maintain capacity stably than Li₃V₂(PO₄)₃. The results indicate that the reducing agent and carbon composite can affect the good crystallinity and electrochemical performance of the cathode materials.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.19-26
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• 2024

In this study, the electrochemical properties of SiOx@C composite materials were prepared to alleviate volume expansion and cycle stability of silicon and to increase the capacity of anode material for LIBs. SiO₂ particles of 100, 200, and 500 nm were synthesized by the Stӧber method, and reduced to SiOx (0≤x≤2) through the magnesiothermic reduction method. Then, SiOx@C anode materials were synthesized by carbonization of PVC on SiOx. The physical properties of prepared SiOx and SiOx@C anode materials were analyzed by XRD, SEM, TGA, Raman spectroscopy, XPS and BET. The electrochemical properties were investigated by cycling performance, rate performance, CV and EIS test. As a result, the SiOx@C-7030 manufactured by coating carbon at SiOx : C = 70 : 30 on a 100 nm SiOx with the smallest particle size showed the best electrochemical properties with a discharge capacity of 1055 mAh/g and a capacity retention rate of 81.9% at 100 cycles. It was confirmed that cycle stability was impoved by reducing particle size and carbon coating.

• Journal of the Korean Electrochemical Society
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• v.27 no.3
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• pp.97-104
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• 2024

The electrodes of commercialized lithium secondary batteries are manufactured through a wet coating process, and the drying process (DC) is a very important factor as to electrode production speed and process cost. In this study, silicon anodes were manufactured under high-temperature (180 ℃) and low-temperature (50 ℃) DC to investigate the quality and the electrochemical performance of Si-electrodes according to DC. High-temperature DC can quickly evaporate the solvent in the Si-electrode slurry, improving the electrode production rate. However, this also causes the electrode composite to peel off from the current collector. As a result, the Si-electrode's adhesion weakened, and the electrode coating's quality deteriorated. In addition, the Si-electrode manufactured under high-temperature was found to have a thicker composite material than the Si-electrode manufactured under low-temperature. Si-electrodes manufactured under high-temperature had higher sheet resistance and lower electrical conductivity than those manufactured under low-temperature. Consequently, the Si-electrode manufactured under low-temperature showed 152.5% superior cycle performance compared to the Si-electrode manufactured under high-temperature. (Discharge capacities of Si-electrodes manufactured under high-temperature and low-temperature DC were 844 and 1287 mAh g^-1, respectively, after 300 cycles). Establishing the DC of Si-electrodes can easily provide new perspectives to improve the quality and stability of Si-electrodes.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.11-17
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• 2010

Modifying surface of activated carbon for the electrode of EDLC with an organic electrolyte was investigated to improve the electrochemical performance of EDLC by the microwave radiation. Three kinds of activated carbons, prepared activated carbon from petroleum cokes and pitch cokes and commercial activated carbon BP-25, were used for this study. For all investigated activated carbons, hydrophilic functional groups-containing oxygen disappeared from the surface of activated carbon as microwave radiation. And as microwave radiation time was increased, the specific surface area and total pore volume of activated carbons were reduced and average pore diameter were increased. From theses effects, interfacial resistance of EDLC with the modified activated carbon electrode was drastically decreased, and discharge capacitance was increased although the specific surface area of activated carbon was reduced by this microwave radiation.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.179-179
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• 2012

국내에는 나노 분말 제조를 위한 RF 열플라즈마 시스템 제조 기술이 확보되어 있지 않고, 또한 나노 파우더 제조를 위한 공정 기술 역시 외국 업체에 전적으로 의존하고 있다. 본 연구에서는 나노 분말 제조를 위한 RF 열 플라즈마 토치 시스템 개발과 고품질의 나노 파우더 합성 공정 기술을 확립하여 필요 기관에 제공하는데 있다. 80 kW RF Plasma torch system의 설계 및 제작을 위해 플라즈마 Simulator인 CFD-ACE+를 이용하여 플라즈마 토치 및 반응로 내의 온도 분포, 유체 유동, 열전달 등의 해석을 통해 플라즈마 토치 및 반응로의 반경 및 길이, 구조의 설계 값을 도출하여 반응로를 설계하여 RF 파워, RF 플라즈마 토치(Torch), 반응기(Reactor), 사이클론(Cyclone), 포집부(Collector), 열교환기 및 진공배기 시스템으로 구성하였다. Si 나노 소재의 경우, 이차전지 음극재에 적용이 가능한 대표적인 소재로서 높음 비용량과 충/방전시 부피팽창을 감소시킬 수 있어 이차전지의 고용량 구현을 위해서는 가장 중요한 소재중 하나로 많은 관심 재료로 평가 받고 있다. 따라서 본 연구에서는 상용화된 Si 원료 powder를 사용하여 고상 분체 공급 장치를 통하여 고온의 플라즈마를 통과시켜 기상화 및 결정화과정을 통해 Si 나노분말을 제조하였다. 공정 변수로서 공정압력 및 플라즈마 power, Gas의 변화량에 따른 나노 분말의 제조 특성에 대한 실험을 진행한 후 제조된 나노 분말을 비표면적측정(BET) 및 SEM 측정 결과 분석을 통하여 시스템 특성을 파악하였으며 제조된 Si 나노 파우더는 이차전지 음극재로서 770 mAh/g의 용량과 93%@50 cycle 수준의 유지율을 나타내었다.

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.561-567
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• 2018

In this study, the electrochemical characteristics of Silicon/Carbon anode materials were analyzed to improve the cycle stability of silicon as an anode materials of lithium ion battery. Porous silicon was prepared from TEOS by the $st{\ddot{o}}ber$ method and the magnesiothermic reduction method. Silicon/Carbon anode materials were synthesized by varying the mass ratio between porous silicon and pitch. Physical properties of the prepared Silicon/Carbon anode materials were analyzed by XRD and TGA. Also the electrochemical performances of Silicon/Carbon anode materials were investigated by constant current charge/discharge, rate performance, cyclic voltammetry and electrochemical impedance tests in the electrolyte of $LiPF_6$ dissolved in organic solvents (EC : DEC = 1 : 1 vol%). The Silicon/Carbon anode composite (silicon : carbon = 5 : 95 in weight) has better capacity (453 mAh/g) than those of other composition cells. The cycle performance has an excellent capacity retention from 2nd cycle to 30th cycle.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.462-462
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• 2009

$CeO_2$는 고체 산화물 연료전지 (SOFC, soild oxide fuel cell)의 전해질 재료와 CMP(Chemical Mechanical Polishing) 슬러리 재료, 자동차의 3원 촉매, gas sensor, UV absorbent등 여러 분야에서 사용되고 있다. 본 연구에서는 위의 활용범위 외에 $CeO_2$의 구조적 안정성과 빠른 $Ce^{3+}/Ce^{4+}$의 전환 특성을 이용하여 lithium ion battery의 anode 재료로서 전기화학적 특성을 알아보고자 실험을 실시하였다. $CeO_2$ 합성에 사용되는 전구체인 cerium carbonate의 형상 및 크기, 비표면적과 같은 물리화학적 특성이 $CeO_2$ 분말의 특성에 직접적인 영향을 주기 때문에 전구체의 합성 단계에서 입자의 특성을 조절하였다. 전구체 합성의 출발원료로 cerium nitrate hexahydrate 와 ammonium carbonate를 사용하였고 반응온도 및 농도 등을 변화시켜 입자의 형상 및 결정상을 fiber형태의 orthorombic $Ce_2O(CO_3)_2{\cdot}H_2O$와 구형의 hexagonal $CeCO_3OH$의 세리아 전구체를 합성하였다. 이를 $300^{\circ}C$에서 30분 동안 하소하여 전구체의 입자형상을 유지하는 cubic $CeO_2$를 합성하고 X-ray diffraction, FE-SEM, micropore physisorption analyzer 분석을 통하여 입자의 결정상과 형상, 비표면적 등을 비교 분석하고 $Li/CeO_2$ couple의 충,방전 용량과 수명특성을 비교 분석하여 $CeO_2$의 전기화학적 특성을 알아보았다.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.1-6
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• 2002

Silver doped vanadium pentoxides with a doping ratio Ag/V ranging from 0.03 to 0.11 were synthesized by sol-gel process, and $Li/Ag_xV_2O_5$ cell was investigated by the electrochemical methods. It appears to be amorphous layered material and entangled fibrous textures has been grown to form anisotropic corrugated fibrils. NMR measurements revealed that several different kinds of $Li^+$ ions exist in the lithium intercalated xerogel electrodes and the average cell potential was about 3.0V vs. $Li/Li^+$. The cell capacity of the silver doped $Ag_xV_2O_5$ xerogel cathodes was more than 359 mAh/g at discharge current 10mA/g and cycle efficiency $94\%$ was achieved.