• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.103.2-103.2
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• 2011

리튬이차전지의 음극물질로서 상용화되고 있는 탄소재료중 흑연은 전기자동차에 적용하기에는 낮은 용량과 나쁜 출력특성을 갖고 있어 지금보다 두배이상의 용량과 출력특성이 좋은 음극소재의 개발이 필요하다. 또 다른 음극물질로 실리콘은 흑연에 비해 월등히 높은 이론용량을 나타내고 있지만 실리콘이 리튬이온과 만나면 부피가 4배이상 팽창하여 사이클이 진행될수록 충방전 용량이 급격히 감소하게 된다. 그래서 본 연구에서는 이 두 음극소재를 상호보완하기 위해 천연흑연을 산처리 과정을 통해 제조된 팽창흑연을 매트릭스로 사용하여 팽창흑연에 실리콘을 충진 시키는 연구를 진행하였다. 팽창흑연에 실리콘을 충진시킴으로써 1C일 때 약 650mAh/g의 용량을 나타내었으며, 50cycle이 진행된 후에도 비교적 안정한 사이클 특성을 나타내었다.

• Journal of the Korean Ceramic Society
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• v.38 no.3
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• pp.293-299
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• 2001

이중층 탄소재료가 콜타르핏치와 메조페이스 핏치, 인조흑연, 천연흑연과 코크스를 사용하여 제조되었다. 콜타르 핏치는 톨루엔이나 경유와 같은 유기용매에 용해되어 코팅재로 사용되었다. 메조페이스 핏치, 인조흑연, 천연흑연 및 코크에 대한 콜타르 핏치의 코팅은 X선 회절분석과 CHN 분석을 통해 확인하였다. 코팅된 탄소재료를 질소분위기의 800-100$0^{\circ}C$에서 열처리한 후 리튬이온 전지의 음극으로 사용하기 위하여 2$600^{\circ}C$에서 열처리하였다. 이중층 탄소재료의 성능평가는 동전형태의 반쪽전지를 통해 수행되었는데, 평가는 음극으로서의 충전과 방전을 통해 수행되었다. 이런 충.방전 능력은 탄소재료의 열처리 온도의 변화나 전구체의 종류에 따라 달리 나타났지만 코팅방법의 차이에 의해서는 큰 차이가 없었다. 열처리를 80$0^{\circ}C$에서 한 경우가 100$0^{\circ}C$에서 한 경우보다 높은 충.방전 능력을 나타내었고, 2$600^{\circ}C$에서 흑연화된 것보다 탄화된 재료들이 높은 충.방전 능력을 나타내었다. 결론적으로, 음극재료의 성능은 결정화도, 조성 및 탄소재료의 미세구조에 따라 달라짐을 알 수 있었다.

• Clean Technology
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• v.26 no.2
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• pp.131-136
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• 2020

Biomass bamboo charcoal is utilized as anode for lithium-ion battery in an effort to find an alternative to conventional resources such as cokes and petroleum pitches. The amorphous phase of the bamboo charcoal is partially converted to graphite through a low temperature graphitization process with iron oxide nanoparticle catalyst impregnated into the bamboo charcoal. An optimum catalysis amount for the graphitization is determined based on the characterization results of TEM, Raman spectroscopy, and XRD. It is found that the graphitization occurs surrounding the surface of the catalysis, and large pores are formed after the removal of the catalysis. The formation of the large pores increases the pore volume and, as a result, reduces the surface area of the graphitized bamboo charcoal. The partial graphitization of the pristine bamboo charcoal improves the discharge capacity and coulombic efficiency compared to the pristine counterpart. However, the discharge capacity of the graphitized charcoal at elevated current density is decreased due to the reduced surface area. These results indicate that the size of the catalysis formed in in-situ graphitization is a critical parameter to determine the battery performance and thus should be tuned as small as one of the pristine charcoal to retain the surface area and eventually improve the discharge capacity at high current density.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.349-349
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• 2015

최근 고용량의 리튬이온전지 개발이 절실하다. 흑연의 용량을 뛰어넘는 고용량 음극재료로서 흑연의 10배가 넘는 이론용량을 가지는 실리콘이 차세대 음극재료로 주목받고 있다. 그러나 실리콘은 큰 부피팽창과 낮은 전기전도도와 같은 문제점을 안고 있으므로 이를 해결하는 것이 시급하다. 따라서 본 연구에서는 이러한 실리콘 음극재료의 전기전도도 향상을 위해 무전해 Ni-B 도금을 이용하여 실리콘 파우더 표면에 Ni 금속을 부분적으로 형성시켰다.

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.162-166
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• 2009

The carbon-coated Si/Cu powders were synthesized by mechanical ball-milling and hydrocarbon gas decomposition methods at high temperature. The carbon-coated Si/Cu powder was used as anode for lithium secondary battery and its electrochemical behavior was investigated. In addition, the carbon-coated Si/Cu/graphite composite anode material was prepared using natural graphite powder and their electrochemical characteristics were compared with natural graphite anode. The specific capacity of carbon-coated Si/Cu anode increased to the initial 10 cycles. The carbon-coated Si/Cu/graphite composite anode exhibited the reversible specific capacity of 450mAh/g and the first cycle efficiency of 81.3% at $0.25mA/cm^2$. The cycling performance of the composite anode was similar to that of pure graphite anode except the reversible specific capacity value.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.672-678
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• 2019

The electrochemical properties of pitch-coated natural graphite(NG) were investigated as an anode for lithium-ion batteries. The anode materials were prepared by heat-treatment of mixture of NG and petroleum pitch at $1000^{\circ}C$. The pitches with various softening points were used as carbon precursor. The physical properties of anode materials were analyzed by TGA, SEM, PSA and BET. As the softening point increased, the thickness of the coating layer increased and the specific surface area decreased. The electrochemical performances were investigated by initial charge/discharge efficiency, cycle stability, cyclic voltammetry, rate performance and electrochemical impedance spectroscopy. The carbon-coated NG using pitch with softening points of $250^{\circ}C$ showed an initial discharge capacity of 361 mAh/g and a coulombic efficiency of 92.6%. Also, the rate performance(5 C/0.2 C) was 1.6 times higher than that of NG, and it had a capacity retention (90%) after 50 cycles at 0.5 C.

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.154-159
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• 2012

Structural volume change occurring on the Si-based anode battery materials during alloying/dealloying with lithium is noticed to be a major drawback responsible for a limited cycle life. Silicon monoxide has been reported to show relatively improved cycling performance compared to Si-containing materials for rechargeable lithium batteries, due to the structural buffering role of in-situ formed $Li_2O$ and lithium silicate during the reaction of silicon monoxide and lithium. Here we report improved cycling ability of interfacially stabilized Si-$SiO_2$-graphite composite anode using silane-based electrolyte additive for rechargeable lithium batteries, which includes low cost silicon dioxide for structural stabilization and graphite for enhanced conductivity.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.118-123
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• 2019

In this study, the electrochemical characteristics of Graphite/Silicon/Pitch anode composites were analyzed to improve the low theoretical capacity of graphite as a lithium ion battery. The Graphite/Silica composites were synthesized by bonding silica onto polyvinylpyrrolidone coated graphite. The surface of used silica was treated with (3-Aminopropyl)triethoxysilane(APTES). Graphite/Silicon/Pitch composites were prepared by carbonization of petroleum pitch, the fabrication processes including the magnesiothermic reduction of nano silica to obtain silicon and varying the mass ratio of silica. The Graphite/Silicon/Pitch composites were analysed by XRD, SEM and XRD. Also the electrochemical performances of Graphite/Silicon/Pitch composite as the anode of lithium ion battery 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:DMC:EMC=1:1:1 vol%). The Graphite/Silicon/Pitch anode composite (silica 28.5 in weight) has better capacity (537 mAh/g). The cycle performance has an excellent capacity retention to 30th cycle of 95% and the retention rate capability of 98% in 0.1 C/0.2 C.

• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.4
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• pp.59-66
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• 2022

Lithium-ion batteries have greatly expanded along with the mobile phone market, and as the electric vehicle business is activated in earnest, they will attract many people's attention even afterwards. Until now, many people have attracted attention to the recovery of valuable metals inside lithium-ion batteries, but graphite, which is mainly used as an anode material, is also worth recycling. Therefore, in order to recover graphite with high purity and valuable metals, graphite that can be used as an anode material of a secondary battery may be generated again through a regeneration process of purifying and separating graphite from a waste lithium-ion battery and recovering electrical characteristics of graphite. This paper describes the process of converting waste graphite into regenerated graphite and the environmental and economic effects of regenerated graphite.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.487-492
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• 2021

In this study, the electrochemical properties of pitch coated silicon sheets/graphite anode materials were investigated. Using NaCl as a template, silicon sheets were prepared through the stöber method and the magnesiothermic reduction methode. In order to synthesize the anode composite, the silicon sheets and graphite were combined with SDBS. The pitch coated silicon sheets/graphite was synthesized using THF as a solvent for the anode material composite. The physical properties of the prepared anode composites were analysed by XRD, SEM, EDS and TGA. The electrochemical performances of the prepared anode composites were performed by the current charge/discharge, rate performance, cyclic voltammetry and EIS tests in the electrolyte LiPF₆ dissolved solvents (EC:DMC:EMC=1:1:1 vol%). As the silicon composition of silicon sheets/graphite composite material increased, the discharge capacity also increased, but the cycle stability tended to decrease. The anode material of pitch coated silicon sheets/graphite composite (silicon sheets:graphite=3:7 weight ratio) showed the initial discharge capacity of 1228.8 mAh/g and the capacity retention ratio of 77% after 50 cycles. From these results, it was found that the cycle stability of pitch coated silicon sheets/graphite was improved.