• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1607-1610
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• 2009

The carbon-coated Si/Cu powder has been prepared by mechanical ball milling and hydrocarbon gas decomposition methods. The phase of Si/Cu powder was analyzed using X-ray diffraction (XRD), dispersive Raman spectroscopy, electron probe microanalysis (EPMA) and transmission electron microscope (TEM). The carbon-coated Si/Cu powders were used as anode active material for lithium-ion batteries. Their electrochemical properties were investigated by charge/discharge test using commercial LiCo$O_2$ cathode and lithium foil electrode, respectively. The surface phase of Si/Cu powders consisted of carbon phase like the carbon nanotubes (CNTs) with a spacing layer of 0.35 nm. The carbon-coated Si/Cu/graphite composite anode exhibited a higher capacity than commercial graphite anode. However, the cyclic efficiency and the capacity retention of the composite anode were lower compared with graphite anode as cycling proceeds. This effect may be attributed to some mass limitations in LiCo$O_2$ cathode materials during the cycling.

• Journal of Electrochemical Science and Technology
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• v.7 no.1
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• pp.33-40
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• 2016

Sr_0.92Y_0.08TiO_3-δ (SYT) was investigated as an alternative anode in humidified CH₄ fuel for SOFCs at low temperatures (650 ℃-750 ℃) and compared with the conventional Ni/yttria-stabilized zirconia (Ni/YSZ) anode. The goal of the study was to directly use a hydrocarbon fuel in a SOFC without a reforming process. The cell performance of the SYT anode was relatively low compared with that of the Ni/YSZ anode because of the poor electrochemical catalytic activity of SYT. In the presence of CH₄ fuel, however, the cell performance with the SYT anode decreased by 20%, in contrast to the 58% decrease in the case of the Ni/YSZ anode. The severe degradation of cell performance observed with the Ni/YSZ anode was caused by carbon deposition that resulted from methane thermal cracking. Carbon was much less detected in the SYT anode due to the catalytic oxidation. Otherwise, a significant amount of bulk carbon was detected in the Ni/YSZ anode.

• Journal of the Korean Electrochemical Society
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• v.19 no.4
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• pp.129-133
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• 2016

In this study, a polymer-carbon composite material is prepared for environmental-friendly organic anode. On poly(styrenesulfonate)(PSS)-carbon composite anode, the carbon is coated by PSS as a core-shell structure and the PSS-carbon composite anode has $524mAh\;g^{-1}$ theoretical capacity with <0.6V voltage. Moreover, the PSS-carbon composite anode shows $519.6mAh\;g^{-1}$, $461.2mAh\;g^{-1}$, $411.8mAh\;g^{-1}$ and $315.9mAh\;g^{-1}$ discharge capacities at 0.1, 0.5, 1 and 10 C, respectively, and stable cycle performance up to 30 cycles. The PSS-carbon composite anode, containing polystyrene and sulfonate functional groups, is suitable for high electrochemical properties organic rechargeable battery.

• 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.

• Carbon letters
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• v.9 no.3
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• pp.210-217
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• 2008

Petroleum pitch and coke with wet mixture method or with dry mixture method were investigated to develop the composite anodic carbon material of high power lithium ion battery. Cokes coated with pitch were obtained by the heat treatment of mixture of cokes and pitch with different weight ratios at $800{\sim}1200^{\circ}C$. The charge and discharge characteristic of the consequent composite anodic carbon material assembled in batteries was tested. Cokes with wet mixture method have a smooth surface and their capacity changed little with changing temperature and content as compared to the cokes with dry mixture method. Although the reversible capacities showed different values by the anode manufacturing method, the composite anode with the mixture of 20 wt% of petroleum pitch and 80 wt% of coke showed the higher power capability and initial efficiency than the pitch based anode. However, the reversible capacity of the composite anode showed the reduced value as compared with the pitch based anode.

• 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.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.37-41
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• 2008

The effects of carbon-coated silicon anode on the electrochemical properties and structural change were investigated. The carbon-coated silicon powders have been prepared by thermal decomposition under argon/10wt% propylene mixed gas flow at $700^{\circ}C$. The surface and crystal structure of the synthesized materials were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Lithium cells with electrodes made from the uncoated and the carbon coated silicon anode were assembled and tested. The carbon-coated silicon particles merged together well after the insertion/extraction of lithium ions, and showed a relatively low irreversible capacity compared with the uncoated silicon particle.

• Korean Journal of Materials Research
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• v.24 no.5
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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 Journal of Materials Research
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• v.33 no.6
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• pp.257-264
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• 2023

To develop a high capacity lithium secondary battery, a new approach to anode material synthesis is required, capable of producing an anode that exceeds the energy density limit of a carbon-based anode. This research synthesized carbon nano silicon composites as an anode material for a secondary battery using the RF thermal plasma method, which is an ecofriendly dry synthesis method. Prior to material synthesis, a silicon raw material was mixed at 10, 20, 30, 40, and 50 wt% based on the carbon raw material in a powder form, and the temperature change inside the reaction field depending on the applied plasma power was calculated. Information about the materials in the synthesized carbon nano silicon composites were confirmed through XRD analysis, showing carbon (86.7~52.6 %), silicon (7.2~36.2 %), and silicon carbide (6.1~11.2 %). Through FE-SEM analysis, it was confirmed that the silicon bonded to carbon was distributed at sizes of 100 nm or less. The bonding shape of the silicon nano particles bonded to carbon was observed through TEM analysis. The initial electrochemical charging/discharging test for the 40 wt% silicon mixture showed excellent electrical characteristics of 1,517 mAh/g (91.9 %) and an irreversible capacity of 133 mAh/g (8.1 %).

• Carbon letters
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• v.16 no.3
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• pp.198-202
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• 2015

Carbon-supported Pt catalyst systems containing defect adsorption sites on the anode of direct methanol fuel cells were investigated, to elucidate the mechanisms of H₂ dissociation and carbon monoxide (CO) poisoning. Density functional theory calculations were carried out to determine the effect of defect sites located neighboring to or distant from the Pt catalyst on H₂ and CO adsorption properties, based on electronic properties such as adsorption energy and electronic band gap. Interestingly, the presence of neighboring defect sites led to a reduction of H₂ dissociation and CO poisoning due to atomic Pt filling the defect sites. At distant sites, H₂ dissociation was active on Pt, but CO filled the defect sites to form carbon π-π bonds, thus enhancing the oxidation of the carbon surface. It should be noted that defect sites can cause CO poisoning, thereby deactivating the anode gradually.