• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.2
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• pp.142-147
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• 2005

In this work, a gel polymer electrolyte (GPE) was prepared using polyoxyalkylene glycol acrylate (POAGA) as a macromonomer LiCoO$_2$/GPE/graphite cells were prepared and their electrochemical properties were evaluated at various current densities and temperatures. The ionic conductivity of the GPE was more than 6.2${\times}$10$^{-3}$ S$.$$cm^{-1}$ / at room temperature. The GPE had good electrochemical stability up to 4.5 V vs. Li/Li$^{+}$. POAGA-based cells were showed good electrochemical performances such as rate capability, low-temperature performance, and cycleability. The cells, also, passed a safety test such as the overcharge and nail-penetration test.t.

• Journal of the Korean Electrochemical Society
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• v.14 no.4
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• pp.208-213
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• 2011

Solid polymer electrolytes using $BF_3LiMA$ as monomer were synthesized by usual one step radical polymerization in THF solvent. The effect of $BF_3LiMA$ concentration on ionic conductivity and electrochemical stability was investigated by AC impedance measurement and linear sweep voltammetry. As a result, the highest ionic conductivity reached $7.71{\times}10^{-6}S\;cm^{-1}$ at $25^{\circ}C$ was obtained in 12.9 wt% of $BF_3LiMA$ content. Further increase or decrease of $BF_3LiMA$ content result to decrease the ionic conductivity due to the brittle matrix properties in former case and the insufficient number of charge carrier in the latter case. Furthermore, since the counter-anion was immobilized in the self-doped solid polymer electrolytes, high electrochemical stability up to 6.0 V was observed even in $60^{\circ}C$.

• Journal of Powder Materials
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• v.21 no.2
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• pp.108-113
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• 2014

Flake-like $LiCoO_2$ nanopowders were fabricated using electrospinning. To investigate their formation mechanism, field-emssion scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were carried out. Among various parameters of electrospinning, we controlled the molar concentration of the precursor and the PVP polymer. When the molar concentration of lithium and cobalt was 0.45 M, the morphology of $LiCoO_2$ nanopowders was irregular and round. For 1.27 M molar concentration, the $LiCoO_2$ nanopowders formed with flake-like morphology. For the PVP polymer, the molar concentration was set to 0.011 mM, 0.026 mM, and 0.043 mM. Irregular $LiCoO_2$ nanopowders were formed at low concentration (0.011 mM), while flake-like $LiCoO_2$ were formed at high concentration (0.026 mM and 0.043 mM). Thus, optimized molar concentration of the precursor and the PVP polymer may be related to the successful formation of flake-like $LiCoO_2$ nanopowders. As a results, the synthesized $LiCoO_2$ nanopowder can be used as the electrode material of Li-ion batteries.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.541-544
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• 2001

Orthorhombic $LiMnO_2$ was synthesized by solid-state reaction using $LiOH{\cdot}H_{2}O$ and $Mn_{2}O_{3}$ as starting material. Its electrochemical properties as cathode in lithium batteries were examined. X-ray diiffraction revealed that the $LiMnO_2$ compound showed a well-defined orthorhombic phase of a space group with Pmnm. The capacity of $LiMnO_2$ agreed well with its specific surface area and grinding treatment was effective in improving cycling performance. For lithium polymer battery applications. the $LiMnO_2$ cell was characterized electrochemically by charge-discharge experiments. And the relationship between the characteristics of powder and electrochemical properties was studied in this research. A maximum discharge capacity of $160-170mAhg^{-1}$ for $LiMnO_2/Li$ cell was achieved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.541-544
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• 2001

Orthorhombic LiMnO$_2$ was synthesized by solid-state reaction using LiOH$.$H$_2$O and Mn$_2$O$_3$ as starting material. Its electrochemical properties as cathode in lithium batteries were examined. X-ray diffraction revealed that the LiMnO$_2$ compound showed a well-defined orthorhombic phase of a space group with Pmnm. The capacity of LiMnO$_2$ agreed well with its specific surface area and grinding treatment was effective in improving cycling performance. For lithium polymer battery applications, the LiMnO$_2$ cell was characterized electrochemically by charge-discharge experiments. And the relationship between the characteristics of powder and electrochemical properties was studied in this research. A maximum discharge capacity of 160-170mAhg$^{-1}$ for LiMnO$_2$/Li cell was achieved

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.608-612
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• 2012

We investigated the cycling behavior of $Li_4Ti_5O_{12}$ electrode in a cross-linked gel polymer electrolyte based on non-flammable ionic liquid consisting of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide and vinylene carbonate. The $Li_4Ti_5O_{12}$ electrodes in ionic liquid-based gel polymer electrolytes exhibited reversible cycling behavior with good capacity retention. Cycling data and electrochemical impedance spectroscopy analyses revealed that the optimum content of the cross-linking agent necessary to ensure both acceptable initial discharge capacity and good capacity retention was about 8 wt %.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.252-254
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• 2002

In this study, polyurethane acrylate macromer was synthesized and it was used in a gel polymer electrolyte, and then its electrochemical performances were evaluated. LiCoO$_2$/GPE/MCF cells were also prepared and their performances depending on discharge currents and temperatures were evaluated. ionic conductivity of the gel polymer electrolyte with PUA at room temperature and -20$^{\circ}C$ was ca. 4.5 x 10$\^$-3/ S/cm and 1.7${\times}$10$\^$-3/ S/cm, respectively. GPE was stable electrochemically up to 4.5 V vs. Li/Li$\^$+/. LiCoO$_2$/GPE/MCF cell showed a good high-rate and a low-temperature performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.12
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• pp.1033-1038
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• 2002

In this study, urethane acrylate macromer was synthesized and it was used in a gel polymer electrolyte (GPE), and then its electrochemical performances were evaluated. LiCoO$_2$/GPE/graphite cells were Prepared and their performances depending on discharge currents and temperatures were evaluated. The precursor consisting of urethane acrylate (UA), hexanediol dimethacrylate (HDDA) and benzoyl peroxide (BPO) had a low viscosity relatively ionic conductivity of the gel polymer electrolyte with UA at room temperature and -20$\^{C}$ was ca. 4.5 $\times$ 10$\^$-3/S$.$cm$\^$-1/ and 1.7 x 10$\^$-3/ S$.$cm$\^$-1/, respectively GPR was stable electrochemically up to potential of 4.i V vs. Li/Li$\^$+/. LiCoO$_2$/GPE/graphite cells showed good a high-rate and a low-temperature performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.374-377
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• 1999

The purpose of this study is to research and develop solid polymer electrolyte(SPE) for Li polymer battery. This paper describes temperature dependence of conductivity, impedance spectroscopy, electrochemical properties of PVDF/PAN electrolytes as a function of a mixed ratio. PVDF/PAN based polymer electrolyte films were prepared by thermal gellification method of preweighed PVDF/PAN, plasticizer and Li salt. The conductivity of PVDF/PAN electrolytes was 10-3S/cm. 20PVDF5PANLiCIO$_4$PC$\sub$10//EC$\sub$10/ electrolyte shows the better conductivity of the others. 20P7DF5PANLiCI$_4$PC$\sub$10//EC$\sub$10/ electrolyte remains stable up to 5V vs. Li/Li$\^$+/. Steady state current method and ac impedance used for the determination of transference numbers in PVDF/PAN electrolyte film. The transference number of 20PVDF5ANLICIO$_4$/PC $\sub$10//EC$\sub$10/ electrolyte is 0.48

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.347-350
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• 2000

The purpose of this study is to research and develop solid polymer electrolyte(SPE) for Li polymer battery. The temperature dependence of conductivity, impedance spectroscopy and electrochemical properties of PMMA/PVDF electrolytes as a function of a mixed ratio were reported for PMMA/PVDF based polymer electrolyte films, which were prepared by thermal gellification method of preweighed PMMA/PVDF, plasticizer and Li salt. The ion conductivity of PMMA/PVDF electrolytes was 10$\^$-3/S/cm, which may be applicable to a constituent of lithium secondary battery. 5PMMA20PVDFLiC1O$_4$PC$\sub$8/EC$\sub$8/ electrolyte remains stable up to 5V vs. Li/Li$\^$+/. Steady state current method and AC impedance were used for the determination of transference numbers in PMMA/PVDF electrolyte film. The transference number of 5PMMA20PVDFLiC1O$_4$PC$\sub$8/EC$\sub$8/ electrolyte is 0.55.