• 전기화학회지
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• 제5권1호
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• pp.1-6
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• 2002

졸-겔법을 이용하여 미량의 은이 도핑된 $Ag_xV_2O_5$ xerogel(x=0.06, 0.11, 0.22)을 합성하여 리튬이차전지용 양극 소재로서 전기화학적 특성을 연구하였다. $Ag_xV_2O_5$ xerogel은 무정형의 층상구조로 열처리하면 orthorhombic 구조로 전환되었으며, 표면구조는 $V_2O_5$와 유사한 단위체가 서로 얽혀 일정한 방향으로 성장하여 비등방성 fibril을 형성하고 있다. $Li/Ag_xV_2O_5$ xerogel셀의 전지 용량(specific capacity)은 10mA/g의 방전율에서 평균 359mAh/g, 싸이클 효율 $94\%$이상이었으며, 바나듐산화물에 첨가된 미량의 은에 의해 전기화학적 특성이 향상되었다. NMR실험으로 서로 다른 환경의 $Li^{+}$이온이 전극에 존재함을 확인하였다.

• 전기화학회지
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• 제20권2호
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• pp.41-48
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• 2017

폴리올레핀 분리막의 내열성을 향상시키면서도 전기화학특성 개선을 위해 RF Magnetron Sputter기반으로 수십 나노미터 수준의 세라믹 층이 코팅된 내열 분리막을 제조하였다. 분리막 원단의 열적 손상없이 코팅 시간을 최소화하기 위한 증착 조건을 최적화 하였고, 이를 기반으로 제조된 내열 분리막의 물리적, 전기화학적 평가를 진행하였다. 약 20 nm의 $Al_2O_3$가 코팅된 Polypropylene(PP) 분리막은 원단 분리막 대비 통기 특성 (원단: 211.3 sec/100 mL, 코팅 분리막: 250.8 sec/100 mL)은 떨어졌으나, 열 수축율 (원단: 19.4%, 코팅 분리막: 0.0% @ $140^{\circ}C$ & 30 min), 전해액 Uptake(원단: 176%, 코팅 분리막: 190%) 및 이온전도도 (원단: 0.700 mS/cm, 코팅 분리막: 0.877 mS/cm)는 모두 향상되었다. 그 결과, 2032-type Half-cell($LiMn_2O_4/Li$)을 이용한 전기화학적 평가에서도, 향상된 율별 특성과 유사한 수명 특성을 나타내었다.

• 폴리머
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• 제34권1호
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• pp.74-78
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• 2010

본 연구에서는 다양한 전류조건하에 전자선 조사로 가교된 리튬 이차전지용 폴리에틸렌 분리막을 제조하였다. 제조된 폴리에틸렌 분리막의 가교율은 조사량이 증가할수록 그리고 빔 전류가 낮을수록 증가하여 최대 71%까지 증가하였다. 낮은 빔 전류에서 조사된 폴리에틸렌 분리막은 상용 분리막 보다 우수한 열수축률(51%) 및 기계적 특성을 보여주었다. 가교된 분리막의 이온전도도는 $1.01{\times}10^{-3}\;S/cm$와 전해액 함침률(275%)은 조사되지 않은 분리막과 거의 동일하였다.

• 한국전기전자재료학회논문지
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• 제29권5호
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• pp.298-302
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• 2016

In this work, $LiMn_2O_4$ and $LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ cathode materials are mixed by some specific ratios to enhance the practical capacity, energy density and cycle performance of battery. At present, the most used cathode material in lithium ion batteries for EVs is spinel structure-type $LiMn_2O_4$. $LiMn_2O_4$ has advantages of high average voltage, excellent safety, environmental friendliness, and low cost. However, due to the low rechargeable capacity (120 mAh/g), it can not meet the requirement of high energy density for the EVs, resulting in limiting its development. The battery of $LiMn_2O_4-LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ (50:50 wt%) mixed cathode delivers a energy density of 483.5 mWh/g at a current rate of 1.0 C. The accumulated capacity from $1^{st}$ to 150th cycles was 18.1 Ah/g when the battery is cycled at a current rate of 1.0 C in voltage range of 3.2~4.3 V.

• 한국재료학회지
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• 제23권12호
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• pp.680-686
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• 2013

Tungsten oxide films were prepared by an electrochemical deposition method for use as the anode in rechargeable lithium batteries. Continuous potentiostatic deposition of the film led to numerous cracks of the deposits while pulsed deposition significantly suppressed crack generation and film delamination. In particular, a crack-free dense tungsten oxide film with a thickness of ca. 210 nm was successfully created by pulsed deposition. The thickness of tungsten oxide was linearly proportional to deposition time. Compositional and structural analyses revealed that the as-prepared deposit was amorphous tungsten oxide and the heat treatment transformed it into crystalline triclinic tungsten oxide. Both the as-prepared and heat-treated samples reacted reversibly with lithium as the anode for rechargeable lithium batteries. Typical peaks for the conversion processes of tungsten oxides were observed in cyclic voltammograms, and the reversibility of the heat-treated sample exceeded that of the as-prepared one. Consistently, the cycling stability of the heat-treated sample proved to be much better than that of the as-prepared one in a galvanostatic charge/discharge experiment. These results demonstrate the feasibility of using electrolytic tungsten oxide films as the anode in rechargeable lithium batteries. However, further works are still needed to make a dense film with higher thickness and improved cycling stability for its practical use.

• 전기화학회지
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• 제16권3호
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• pp.177-183
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• 2013

고전압에서도 사용 가능한 바인더 개발에 대한 요구가 증대됨에 따라 이에 적합한 내산화성이 우수한 바인더를 양자화학적 모델링에 기반하여 제안하고자 하였다. 각 고분자 poly(acryl amide)(PAM), poly(methyl acrylate)(PMA), poly(vinylidene fluoride)(PVDF), poly(hexafluropropylene)(PHFP)에 대하여 반경험적 방법(Semi-empirical method) 및 밀도범함수 이론(Density Functional Theory, DFT) 방법을 이용하여 단량체부터 사량체까지의 고분자 바인더에 대한 최고 점유 분자 궤도함수(Highest occupied molecular orbital, HOMO) 에너지와 이온화 에너지(Ionization Potential, IP) 값을 구하여 실험 값과 비교하였다. 밀도범함수 방법으로 해석한 결과, PHFP, PVDF, PMA, PAM 순으로 고분자의 내산화성이 좋은 것으로 시뮬레이션을 통해 예측되었고, 이러한 결과는 선형 훑음 전압-전류법(Linear Sweep Voltametry, LSV)으로부터 얻은 실험값과 일치하였다. 또한 이 결과는 HOMO 오비탈의 구조를 분석하여 내산화성이 좋은 원인을 규명하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권2호
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• pp.53-61
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• 2004

Characteristics of half cells of graphite/lithium and LiCoO$_2$/lithium, and full cells of graphite/LiCoO$_2$/ were analyzed by the use of GISOC(the gradual increasing of the state of charge). GISOC analyses generated IIE(the initial intercalation efficiency), which represents lithium intercalation property of the electrode material, and IIC$_{s}$(the initial irreversible capacity by the surface), which represents irreversible reaction between the electrode surface and electrolyte. Linear-fit range of graphite and LiCo/O$_2$electrodes were respectively 370 and 150 mAh/g based on material weight. IIE of graphite and LiCo/O$_2$electrodes were respectively 93∼94 % and 94∼95 %, and IICs of graphite and LiCo/O$_2$electrodes were 15∼17 mAH/g and 0.3∼1.7 mAh/g, respectively. IIE of graphite/LiCo/O$_2$full cell for GX25 and DJG311 as graphite showed 89∼90 %, which IIE value was lower than IIE of half cell of the cathode and the anode. Parameters of IIE and IIC$_{s}$ can also be used to represent not only half cell but also full cell. The characteristics of the full cell can be simulated through the correlative interpretation of potential profile, IIE, and IIC$_{s}$ of half cells.cells.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.378-379
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• 2006

The carbon thin film was developed by the CVD method using the carbon source of toluene with the stream of argon gas at $800{\sim}1100^{\circ}C$ for 1 hour. Developed carbon thin films have the material loading of 0.27 mg($800^{\circ}C$), 0.80 mg($900^{\circ}C$), 2.3 mg($1000^{\circ}C$), and 2.9 mg($1100^{\circ}C$) for the disk of 15 mm diameter on single side. The characteristics of carbon thin film as the anode of thin film battery were evaluated using Li|C coin cell. Li|C($1100^{\circ}C$) coin cell has the first specific discharge and charge capacity of 953 mAh/g and 374 mAh/g, respectively, resulting the first Ah efficiency of 39.3 %. Capacity retention of the 5th cycle was 93.2 % indicating good cycleability. The carbon thin film prepared by CVD shows good specific capacity and cycleability, but low Ah efficiency.

• 한국재료학회지
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• 제24권5호
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• pp.243-248
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• 2014

Silicon-carbon composite was prepared by the magnesiothermic reduction of mesoporous silica and subsequent impregnation with a carbon precursor. This was applied for use as an anode material for high-performance lithium-ion batteries. Well-ordered mesoporous silica(SBA-15) was employed as a starting material for the mesoporous silicon, and sucrose was used as a carbon source. It was found that complete removal of by-products ($Mg_2Si$ and $Mg_2SiO_4$) formed by side reactions of silica and magnesium during the magnesiothermic reduction, was a crucial factor for successful formation of mesoporous silicon. Successful formation of the silicon-carbon composite was well confirmed by appropriate characterization tools (e.g., $N_2$ adsorption-desorption, small-angle X-ray scattering, X-ray diffraction, and thermogravimetric analyses). A lithium-ion battery was fabricated using the prepared silicon-carbon composite as the anode, and lithium foil as the counter-electrode. Electrochemical analysis revealed that the silicon-carbon composite showed better cycling stability than graphite, when used as the anode in the lithium-ion battery. This improvement could be due to the fact that carbon efficiently suppressed the change in volume of the silicon material caused by the charge-discharge cycle. This indicates that silicon-carbon composite, prepared via the magnesiothermic reduction and impregnation methods, could be an efficient anode material for lithium ion batteries.

• Korean Chemical Engineering Research
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• 제59권3호
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• pp.326-332
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• 2021

본 연구에서는 수열 합성법을 이용하여 나노 실리콘이 포함된 구형의 탄소 복합체를 합성하고, 석유계 피치로 코팅하여 제조된 음극 소재의 전기화학 특성을 조사하였다. 수크로스의 몰 농도를 변화시켜 수열합성한 후, 유기 용매로 THF를 사용하여 피치로 코팅된 음극 복합소재를 제조하였다. 제조된 음극 소재는 SEM, EDS, XRD 및 TGA를 사용하여 물리적 특성을 분석하였으며, 1.0 M LiPF₆ (EC : DMC : EMC = 1 : 1 : 1 vol%) 전해액에서 사이클, 율속, 순환전압전류 및 임피던스 테스트를 통해 리튬이차전지의 전기화학 성능을 조사하였다. 1.5 M의 수크로스와 피치를 사용하여 제조된 실리콘/탄소 소재는 구형 형태를 보였으며, 1756 mAh/g의 높은 초기 용량, 50 사이클 후 82 %의 용량 유지율 및 2 C/0.1 C에서 81%의 우수한 속도 특성을 확인할 수 있었다.