• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1257-1261
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• 2010

The electrochemical performances of anode composites comprising elemental silicon (Si), silicon monoxide (SiO), and graphite (C) were investigated. The composite devoid of elemental silicon (SiO:C = 1:1) and its carbon coated composite showed reduced capacity degradation with measured values of 606 and 584 mAh/g at the fiftieth cycle. The capacity retention nature when the composites were cycled followed the order of Si:SiO:C = 3:1:4 < Si:SiO:C = 2:2:4 < SiO:C = 1:1 < SiO:C = 1:1 (carbon coated). A comparison of the capacity retention properties for the composites in terms of the silicon content showed that a reduced silicon content increased the stability of the composite electrodes. Even though the carbon-coated composite delivered low capacity during cycling compared to the other composites, its low capacity degradation made the anode a better choice for lithium ion batteries.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.636-643
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• 2006

Si-C materials were synthesized by the heating the mixture of silicon and polyvinylidene fluoride (PVDF). The electrochemical properties of the Si-C materials as the high capacitive anode materials of lithium secondary batteries were evaluated by the galvanostatic charge-discharge test through 2032 type $Si-C{\mid}Li$ coin cells. Charge-discharge tests were performed at C/10 hour rate(C = 372 mAh/g). Initial discharge and charge capacities of $Si-C{\mid}Li$ cell using a Si-C material derived from PVDF(20wt.%) were found to be 1,830 and 526 mAh/g respectively. The initial discharge-charge characteristics of the developed Si-C electrode were analyzed by the electrochemical galvanostatic test adopting the capacity limited charge cut-off condition(GISOC). The range of reversible specific capacity IIE(intercalation efficiency at initial discharge-charge) and IICs(surface irreversible specific capacity) were 216 mAh/g, 68 % and 31 mAh/g, respectively.

• Journal of Electrochemical Science and Technology
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• v.2 no.2
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• pp.116-123
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• 2011

Herein, a novel preparation method of highly homogeneous carbon-silicon composite materials was presented. In contrast to conventional solvent evaporation method, a milled silicon-graphite or its oxidized material were directly reacted with petroleum-derived pitch precursor. After thermal reaction under high pressure, pitch-graphite-silicon composite was prepared. Carbon-graphite-silicon composite were prepared by an air-oxidization and following carbonization. From energy dispersive spectroscopy, it was observed that small Si particles were highly embedded within carbon, which was confirmed by disappearance of Si peaks in Raman spectra. Furthermore, X-ray diffraction and Raman spectra revealed that carbon crystallinity decreased when the strongly oxidized silicon-graphite was added, which was probably due to oxygen-induced cross-linking. From the anode application in lithium ion batteries, carbon-graphite-silicon composite anode displayed a high capacity ($565\;mAh\;g^{-1}$), a good initial efficiency (68%) and an good cyclability (88% retention at 50 cycles), which were attributed to the high dispersion of Si particles within cabon. In case of the strongly oxidized silicongraphite addtion, a decrease of reversible capacity was observed due to its low crystallinity.

• Journal of the Korean Electrochemical Society
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• v.5 no.4
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• pp.178-182
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• 2002

The electrochemical behavior of binder-free carbon anode, comprising of only artificial and natural graphite (AG and NG) particles, for intercalation and deintercalation of lithium ion $(Li^+)$ in aluminum chloride (AICI_3)-I-ethyl­3-methylimidazolium chloride (EMIC)-lithium chloride (LiCl)-thionyl chloride $(SOCI_2)$ room-temperature molten salt (RTMS) was studied. Binder-free carbon electrodes were fabricated using electrophoretic deposition (EPD) method. The binder-free carbon anodes provided a relatively flat charge and discharge potentials $(0\;to\;0.2V\;vs.\;Li/Li^+)$ and current capabilities $(250-340mAh{\cdot}g^{-1})$ for the intercalation and deintercalation of $Li^+$. Stability of the binder-free carbon anodes for intercalation and deintercalation of 50 cycles was confirmed.

• Journal of the Korean Electrochemical Society
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• v.22 no.3
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• pp.122-127
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• 2019

In this study, we investigate the electrochemical performance of lithium terephthalate (LTA) battery using graphite coated metal current collector to overcome the disadvantages of organic batteries which is high interfacial resistance between current collector and electrode. The LTA anode material is synthesized by acid-based ion exchange reaction without impurities. The contact properties between stick-type LTA-based electrode and graphite coated current collector are estimated by the cross-section SEM and EIS. The graphite coated current collector significantly reduced the interfacial resistance of the LTA battery. The second discharge capacities of bare current collector LTA and graphite coated current collector LTA batteries are 107.6 mAh/g and 148.8 mAh/g at 0.1C, respectively. The graphite coated current collector LTA batteries show higher cycle life, higher discharge capacity, and higher rate-capability than bare LTA batteries.

• Membrane Journal
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• v.31 no.6
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• pp.417-425
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• 2021

As the demand for high-capacity batteries increases, there has been growing researches on the lithium metal anode with a capacity (3,860 mAh/g) of higher than that of conventional one and a low electrochemical potential (-3.040 V). In this study, using the anatase phased TiO₂ nanoparticles synthesized by hydrothermal synthesis, a PVdF-HFP/TiO₂ organic/inorganic composite material was designed and used as an interfacial protective layer for a Li metal anode. As-formed organic/inorganic-lithium composite thin film was confirmed through the crystalline structure and morphological analyses. In addition, the electrochemical test (cycle stability and voltage profile) confirmed that the protective layer of PVdF-HFP/TiO₂ composite (10 wt% TiO₂ and 1.1 ㎛ film thickness) contributed to the enhanced electrochemical performance of the lithium metal anode (Colombic efficiency retention: 90% for 77 cycles). Based on comparative test with the untreated lithium electrode, it was confirmed that our protective layer plays an important role to stabilize/improve the EC performance of the lithium metal negative electrode.

• 한국전기화학회:학술대회논문집
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• 2005.04a
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• pp.39-40
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• 2005

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.534-538
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• 2017

In this study, the molecular weight controlled pitches derived from pyrolyzed fuel oil (PFO) were prepared using solvent extraction and were carbonized. Electrochemical characteristics of lithium battery anode materials were investigated using these petroleum pitches. Three pitch samples prepared by the thermal reaction were 3903 (at $390^{\circ}C$ for 3 h), 4001 (at $400^{\circ}C$ for 1 h) and 4002 (at $400^{\circ}C$ for 2 h). The prepared hexane insoluble pitches were analysed by XRD, TGA, SEM and Gel permeation Chromatography (GPC). The electrochemical characteristics of the PFO-derived pitch as an anode material were investigated by constant current charge/discharge, cyclic voltammetry and electrochemical impedance tests. The coin cell using pitch (4001) and the electrolyte of $LiPF_6$ in organic solvents (EC : DMC = 1 : 1 vol%, VC 3 wt%) has better initial capacity (310 mAh/g) than that of other pitch coin cells. Also, this carbon anode showd a high initial efficiency of 82%, retention rate capability at 2 C/0.1 C of 90% and cycle retention of 85%. It was found that modified pitches improved the cycling and rate capacity performance.

• 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.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.290-298
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• 2021

A purification process was performed for the application of natural graphite as an anode material. The influence of the structural change and impurity content of graphite according to the process on the anode electrochemical characteristics was investigated. Natural graphite was chemically/physically purified by acid-treatment which used different amounts of solution of ammonium fluoride/sulfuric acid in the same ratio and thermal treatment used different temperatures (800~2500 ℃). Acid-treatment had limitation to remove impurities, and identified that all impurity contents was removed except some traces of atom such as Si by after progressed thermal-treatment until 2500 ℃. The anode materials characteristic of graphite treated by purification process was improved, and changes in the structure and impurity contents affected dominantly the capacity, rate property and initial Coulombic efficiency. Consequently, the complex purification process improved the graphite structure and also the performance of lithium ion battery by controlling the excessive formation of solid electrolyte interphase and expanding Li⁺ insertion space originated from the effective removal of impurities.