• Title, Summary, Keyword: Vinylene Carbonate

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Effects of Phosphorous-doping on Electrochemical Performance and Surface Chemistry of Soft Carbon Electrodes

  • Kim, Min-Jeong;Yeon, Jin-Tak;Hong, Kijoo;Lee, Sang-Ick;Choi, Nam-Soon;Kim, Sung-Soo
    • Bulletin of the Korean Chemical Society
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    • v.34 no.7
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    • pp.2029-2035
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    • 2013
  • The impact of phosphorous (P)-doping on the electrochemical performance and surface chemistry of soft carbon is investigated by means of galvanostatic cycling and ex situ X-ray photoelectron spectroscopy (XPS). P-doping plays an important role in storing more Li ions and discernibly improves reversible capacity. However, the discharge capacity retention of P-doped soft carbon electrodes deteriorated at $60^{\circ}C$ compared to non-doped soft carbon. This poor capacity retention could be improved by vinylene carbonate (VC) participating in forming a protective interfacial chemistry on soft carbon. In addition, the effect of P-doping on exothermic thermal reactions of lithiated soft carbon with electrolyte solution is discussed on the basis of differential scanning calorimetry (DSC) results.

Electrochemical Characteristics of Surface Modified CTP Anode by H3PO4 Treatment (인산 처리된 표면 개질 음극 석탄계 피치의 전기화학적 특성)

  • Lee, Ho Yong;Lee, Jong Dae
    • Applied Chemistry for Engineering
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    • v.27 no.4
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    • pp.415-420
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    • 2016
  • To enhance electrochemical performances of anode materials, the surface of coal tar pitch (CTP) was modified by incorporating heteroatoms through chemical treatment with phosphoric acid ($H_3PO_4$). The prepared anode materials with modified CTP was analyzed by XRD, FE-SEM and XPS. The electrochemical performances of modified CTP were investigated by constant current charge/discharge test, rate performance, cyclic voltammetry and impedance tests using the electrolyte of $LiPF_6$ dissolved in the mixed organic solvents (ethylene carbonate : dimethyl carbonate = 1 : 1 vol% + vinylene carbonate 3 wt%). The coin cell using modified CTP ($H_3PO_4/CTP$ = 3 : 100 in weight) has better initial capacity and initial efficiency (489 mAh/g, 82%) than those of other composition coin cells. Also, it was found that the capacity retention was 86% after 30 cycles and the rate capability was 87% at 2 C/0.1 C.

Electrochemical Characteristics of Graphite/Silicon/Pitch Anode Composites for Lithium Ion Batteries using Silica-Coated Graphite (실리카로 코팅된 흑연을 이용한 리튬 이차전지용 흑연/실리콘/피치 복합소재의 전기화학적 특성)

  • Lee, Su Hyeon;Lee, Jong Dae
    • Korean Chemical Engineering Research
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    • v.58 no.1
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    • pp.142-149
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    • 2020
  • In this study, the electrochemical performance of Graphite/Silicon/Pitch composites as anode material was investigated to improve the low theoretical capacity of artificial graphite. Spherical artificial graphite surface was coated with polyvinylpyrrolidone (PVP) amphiphiles material to synthesize Graphite/Silica material by silica islands growth. The Graphite/Silicon/Pitch composites were prepared by petroleum pitch coating and magnesiothermic reduction. The Graphite/Silicon/Pitch composite electrodes manufactured using poly(vinylidene fluoride) (PVDF), carboxymethyl cellulose (CMC) and polyacrylic acid (PAA) binders. The coin type half cell was assembled using various electrolytes and additives. The Graphite/Silicon/Pitch composites were analysed by X-ray diffraction (XRD), scanning electron microscope (SEM) and a thermogravimetric analyzer (TGA). The electrochemical characteristics of Graphite/Silicon/Pitch composite were investigated by constant current charge/discharge, rate performance, cyclic voltammetry and electrochemical impedance spectroscopy. The Graphite/Silicon/Pitch composites showed high cycle stability at a graphite/silica/pitch ratio (1:4:8 wt%). When the electrode is prepared using PAA binder, the high capacity and stability is obtained. The coin type half cell assembled using EC: DMC: EMC electrolyte showed high initial capacity (719 mAh/g) and excellent cycle stability. The rate performance has an capacity retention (77%) at 2 C/0.1 C and an capacity recovery (88%) at 0.1 C / 0.1 C when the vinylene carbonate (VC) was added.

Synthesis and Electrochemical Characteristics of Silicon/Carbon Anode Composite with Binders and Additives (Silicon/Carbon 음극소재 제조 및 바인더와 첨가제에 따른 전기화학적 특성)

  • Park, Ji Yong;Lee, Jong Dae
    • Korean Chemical Engineering Research
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    • v.56 no.3
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    • pp.303-308
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    • 2018
  • Silicon/Carbon (Si/C) composite as anode materials for lithium-ion batteries was synthesized to find the effect of binders and an electrolyte additive. Si/C composites were prepared by two step method, including magnesiothermic reduction of SBA-15 (Santa Barbara Amorphous material No. 15) and carbonization of phenol resin. The electrochemical performances of Si/C composites were investigated by charge/discharge, cyclic voltammetry and impedance tests. The anode electrode of Si/C composite with PAA binder appeared better capacity (1,899 mAh/g) and the capacity retention ratio (92%) than that of other composition coin cells during 40 cycles. Then, Vinylene carbonate (VC) was tested as an electrolyte additive. The influence of this additive on the behavior of Si/C anodes was very positive (3,049 mAh/g), since the VC additive is formed passivation films on Si/C surfaces and suppresses irreversible changes.