• 한국전기화학회:학술대회논문집
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• 한국전기화학회 1998년도 제1회 총회 및 추계학술발표회
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• pp.88-88
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• 1998

• 한국입자에어로졸학회지
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• 제15권4호
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• pp.127-137
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• 2019

Recently, high electrochemical performance anode materials for lithium ion secondary batteries are of interest. Here, we present silicon-carbon-graphene (Si-C-GR) composites for high performance anode materials of lithium ion secondary battery (LIB). Aerosol process and heat-treatment were employed to prepare the Si-C-GR composites using a colloidal mixture of silicon, glucose, and graphene oxide precursor. The effects of the size of the silicon particles in Si-C-GR composites on the material properties including the morphology and crystal structure were investigated. Silicon particles ranged from 50 nm to 1 ㎛ in average diameter were employed while concentration of silicon, graphene oxide and glucose was fixed in the aerosol precursor. Morphology of as-fabricated Si-C-GR composites was generally the shape of a crumpled paper ball and the Si particles were well wrapped in carbon and graphene. The size range of composites was about from 2.2 to 2.9 ㎛. The composites including silicon particles larger than 200 nm in size exhibited higher performance as LIB anodes such as capacity and coulombic efficiency than silicon particles less than 100 nm, which were about 1500 mAh/g at 100 cycles in capacity and 99% in coulombic efficiency, respectively.

• Korean Chemical Engineering Research
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• 제56권1호
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• pp.42-48
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• 2018

리튬이온전지의 음극재로 높은 이론적인 용량과 낮은 방전 전위 및 무독성을 가진 실리콘이 높은 관심을 받고 있다. 본 연구에서는 리튬이온전지의 고효율 음극재로 활용을 위한 실리콘-탄소나노튜브-탄소(Si-CNT-C) 복합체를 제조하였다. 복합체 제조를 위해서는 에어로졸 자기조립과 후 열처리 공정을 사용하였다. 제조된 Si-CNT-C 복합체는 구형이었으며 평균 입자크기는 $2.72{\mu}m$이었다. 복합체의 크기는 실리콘 및 탄소나노튜브의 농도가 증가할수록 커지는 것을 확인하였다. Si-CNT-C 복합체는 탄소나노튜브와 글루코스에서 탄화된 탄소가 실리콘 입자들을 중심으로 표면에 부착된 형태이었다. 제조된 Si-CNT-C 복합체는 전기화학 분석을 통해 순수한 실리콘보다 우수한 사이클 성능을 보여주고 있음을 확인하였다.

• Transactions on Electrical and Electronic Materials
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• 제15권6호
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• pp.338-343
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• 2014

A $Fe_3O_4$-graphite nanofiber composite for use as an anode material was successfully synthesized by calcining $Fe_3O_4$ and graphite nanofiber (GNF) together in a $N_2$ atmosphere. Using this $Fe_3O_4$-GNF composite in a lithium ion battery resulted in a higher lithium storage capacity than that obtained using $Fe_3O_4$-graphite ($Fe_3O_4$-G). The $Fe_3O_4$-GNF (10 wt%) electrode exhibited a higher lithium ion diffusion coefficient ($2.29{\times}10^{-9}cm^2s^{-1}$) than did the $Fe_3O_4$-G (10%) ($3.17{\times}10^{-10}cm^2s^{-1}$). At a current density of $100mA\;g^{-1}$, the $Fe_3O_4$-GNF (10 wt%) anode showed a higher reversible capacity ($1,031mAh\;g^{-1}$) than did the $Fe_3O_4$-G (10%) anode ($799mAh\;g^{-1}$). Moreover, the $Fe_3O_4GNF$ electrodes showed good cycling performance without the addition of a conductive material.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.852-856
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• 2011

The lithium ion diffusion coefficients of bare, carbon-coated and Cr-doped $LiFePO_4$ were obtained by fitting the discharge curves of each half cell with Li metal anode. Diffusion losses at discharge curves were acquired with experiment data and fitted to equations. Theoretically fitted equations showed good agreement with experimental results. Moreover, theoretical equations are able to predict lithium diffusion coefficient and discharge curves at various discharge rates. The obtained diffusion coefficients were similar to the true diffusion coefficient of phase transformation electrodes. Lithium ion diffusion is one of main factors that determine voltage drop in a half cell with $LiFePO_4$ cathode and Li metal anode. The high diffusion coefficient of carbon-coated and Cr-doped $LiFePO_4$ resulted in better performance at the discharge process. The performance at high discharge rate was improved much as diffusion coefficient increased.

• 자원리싸이클링
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• 제33권1호
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• pp.15-21
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• 2024

전기차용 리튬이온배터리의 수요가 증가함에 따라 향후 발생할 폐리튬이온배터리 중의 유가금속 회수가 필요하다. 본 연구에서는 리튬이온배터리의 NCM계 양극재를 수소환원과 수침출에 의해 리튬을 수산화리튬으로 회수할 때의 회수율에 미치는 반응온도의 영향을 조사하였다. 반응온도가 상승함에 따라 수소에 의한 NiO, CoO의 환원에 의해 무게 감소율이 반응초기부터 급격하게 증가하였으며 동시에 H₂O 발생량도 증가하였다. 602 ℃ 이상에서는 양극재 중의 Ni, Co가 전부 환원되어 금속상으로 존재하였다. 그리고 수소환원 온도의 상승과 함께 Li 회수률도 증가하였으나 704 ℃ 이상에서는 약 92 % 이상의 유사한 수준을 나타내었다. 따라서 폐Li이온 배터리의 전처리로 수소환원하는 것에 의해 리튬만 사전에 회수하고 잔사를 재처리하면 효율적으로 유가금속을 분리하여 회수할 수 있을 것으로 기대된다.

• Carbon letters
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• 제5권3호
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• pp.118-126
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• 2004

MCMB (Mesocarbon microbeads) is a kind of anode material for lithium-ion secondary battery. MCMB charge/discharge cycle stability is one of the important criterion at lithium-ion battery operation. In this study, the cycling stability of a lithium-ion secondary battery has been examined. MCMB was made by the direct solvent extraction method. After the MCMB was carbonized and graphitized, the measurement of charge/discharge capacity and efficiency were carried out. In the result, discharge capacity of MCMB in the initial cycle was above 290.0 mAh/g. After the second cycle, efficiency of charge/discharge MCMB was about 98%. These results were similar to the commercial MCMB product.

• 청정기술
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• 제24권4호
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• pp.332-338
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• 2018

현재 리튬이온전지의 음극 소재 활물질로는 흑연이 주로 사용되고 있다. 그러나 흑연의 최대 이론 용량이 $372mA\;h\;g^{-1}$으로 제한되기 때문에 차세대 고용량 및 고에너지 밀도의 리튬이온전지 개발을 위해서는 새로운 음극 소재 활물질이 필요하다. 여러 음극 소재 활물질 중에서 Si의 최대 이론 용량은 $4200mA\;h\;g^{-1}$으로 흑연의 최대 이론 용량보다 약 10배 이상 높은 값을 나타내고 있지만 부피 팽창율이 거의 400%로 크기 때문에 사이클이 진행될수록 비가역 용량이 증가하여 충전 대비 방전 용량이 현저히 감소하는 현상을 나타내고 있다. 이러한 문제점을 해결하기 위한 방법으로 Si 음극 소재 활물질의 입자 크기를 조절하여 기계적 응력 및 반응상의 체적 변화를 감소시켜 사이클 특성을 다소 향상시킬 수 있다. 따라서 Si 입자의 부피 팽창율에 따른 충전 및 방전 용량의 감소를 최소화하기 위해 공정 시간 및 원가 절감이 우수한 건식 방법으로 Si을 분쇄하여 사이클 특성 향상에 관한 연구를 진행 하였다. 본 논문에서는 진동밀을 이용하여 Si을 나노 크기로 제어하고 실험 변수에 따른 재료들의 물리화학적 특성과 전기화학적 특성을 측정하였다.

• 한국응용과학기술학회지
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• 제20권2호
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• pp.130-140
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• 2003

In order to improve the lithium ion battery's performance, the carbon nanofibers were introduced to the anode electrode fabricated with natural graphite particles. The influence of structural adjustment of the particles by the introduction method of carbon nanofibers and the content of carbon nanofibers on the electrical property and charge/discharge characteristics of the electrode were investigated. The electrode fabricated with the mixture of 10 wt% of carbon nanofibers grown separately and 90 wt% of graphite particles showed an excellent discharge capacity of 400 mAh/g and the improved cycle performance. The improved performance could be explained by that the carbon nanofibers shortened and uniformly distributed on the surface of graphite particles by ball milling increased the stability for the intercalation/deintercalation of lithium ion and increased the electrical conductivity due to the closed packing between graphite particles.

• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1965-1968
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• 2008

The effects of carbon-coated silicon/graphite (Si/Gr.) composite anode on the electrochemical properties were investigated. The nanosized silicon particle shows a good cycling performance with a reasonable value of the first reversible capacity as compared with microsized silicon particle. The carbon-coated silicon/graphite composite powders have been prepared by pyrolysis method under argon/10 wt% propylene gas flow at $700{^{\circ}C}$ for 7 h. Transmission electron microscopy (TEM) analysis indicates that the carbon layer thickness of 5 nm was coated uniformly onto the surface silicon powder. It is confirmed that the insertion of lithium ions change the crystalline silicon phase into the amorphous phase by X-ray diffraction (XRD) analysis. The carbon-coated composite silicon/graphite anode shows excellent cycling performance with a reversible value of 700 mAh/g. The superior electrochemical characteristics are attributed to the enhanced electronic conductivity and low volume change of silicon powder during cycling by carbon coating.