• Title/Summary/Keyword: LI6

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Electrochemical Characteristics of Hybrid Capacitor using Core-shell Structure of MCMB/Li4Ti5O12 Composite (Core-shell 구조의 MCMB/Li4Ti5O12 합성물을 사용한 하이브리드 커패시터의 전기화학적 특성)

  • Ko, Hyoung Shin;Choi, Jeong Eun;Lee, Jong Dae
    • Korean Chemical Engineering Research
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    • v.52 no.1
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    • pp.52-57
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    • 2014
  • The MCMB-$Li_4Ti_5O_{12}$ with core-shell structure was prepared by sol-gel process to improve low cycle capability of MCMB in this study. The electrochemical characteristics were investigated for hybrid capacitor using MCMB-$Li_4Ti_5O_{12}$ as the negative electrode and $LiMn_2O_4$, Active carbon fiber as the positive electrode. The electrochemical behaviors of hybrid capacitor using organic electrolytes ($LiPF_6$, EC/DMC/EMC) were characterized by charge/discharge, cyclic voltammetry, cycle and impedance tests. The hybrid capacitor using MCMB-$Li_4Ti_5O_{12}/LiMn_2O_4$ electrodes had better capacitance than MCMB hybrid systems and was able to deliver a specific energy with 67 Wh/kg at a specific power of 781 W/kg.

Corrosion Behavior and Effect of Alloying Elements of Fe-base and Ni-base Superalloys on Hot Molten Salt (고온 용융염에서 Fe기 및 Ni기 초합금의 부식거동 및 합금원소의 영향)

  • Jo, Su-Haeng;Jang, Jun-Seon;Jeong, Myeong-Su;O, Seung-Cheol;Sin, Yeong-Jun
    • Korean Journal of Materials Research
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    • v.9 no.10
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    • pp.985-991
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    • 1999
  • Corrosion behaviors of Incoloy 800H, KSA(Kaeri Superalloy)-6, Inconel 600 and Hastelloy C-276 in molten salts were investigated in the temperature range of 650 ~ $850^{\circ}C$. Due to $\textrm{Li}_{2}\textrm{O}$-induced basic fluxing mechanism, the corrosion rates of the alloys in mixed molten salt of LiC1-$\textrm{Li}_{2}\textrm{O}$ were significantly higher than those in molten salt of LiCl. In the mixed molten salt, Fe-base alloys showed higher corrosion resistance than the Ni-base alloys. and Hastelloy C-276 with high Mo and W contents exhibited the highest corrosion rate among the examined alloys. The single layer of $\textrm{LiCrO}_{2}$ was formed in molten salt of LiCl and two phase structure of a scale consisted of oxides and Ni was formed in the mixed molten salt.

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A LiPF6-LiFSI Blended-Salt Electrolyte System for Improved Electrochemical Performance of Anode-Free Batteries

  • Choi, Haeyoung;Bae, YeoJi;Lee, Sang-Min;Ha, Yoon-Cheol;Shin, Heon-Cheol;Kim, Byung Gon
    • Journal of Electrochemical Science and Technology
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    • v.13 no.1
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    • pp.78-89
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    • 2022
  • ANODE-free Li-metal batteries (AFLMBs) operating with Li of cathode material have attracted enormous attention due to their exceptional energy density originating from anode-free structure in the confined cell volume. However, uncontrolled dendritic growth of lithium on a copper current collector can limit its practical application as it causes fatal issues for stable cycling such as dead Li formation, unstable solid electrolyte interphase, electrolyte exhaustion, and internal short-circuit. To overcome this limitation, here, we report a novel dual-salt electrolyte comprising of 0.2 M LiPF6 + 3.8 M lithium bis(fluorosulfonyl)imide in a carbonate/ester co-solvent with 5 wt% fluoroethylene carbonate, 2 wt% vinylene carbonate, and 0.2 wt% LiNO3 additives. Because the dual-salt electrolyte facilitates uniform/dense Li deposition on the current collector and can form robust/ionic conductive LiF-based SEI layer on the deposited Li, a Li/Li symmetrical cell exhibits improved cycling performance and low polarization for over 200 h operation. Furthermore, the anode-free LiFePO4/Cu cells in the carbonate electrolyte shows significantly enhanced cycling stability compared to the counterparts consisting of different salt ratios. This study shows an importance of electrolyte design guiding uniform Li deposition and forming stable SEI layer for AFLMBs.

High Pressure X-ray Diffraction Study of LiFePO4/C-olivine-like Phase (LiFePO4/C-유사 감람석 결정구조에 대한 고압 X-선회절연구)

  • Hwang, Gil-Chan;Kim, Young-Ho
    • Journal of the Mineralogical Society of Korea
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    • v.26 no.1
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    • pp.35-44
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    • 2013
  • Synthetic carbon-coated olivine-like structured lithium iron phosphate ($Li^+Fe^{2+}(PO_4)^{3-}/C$) powder composites were compressed up to 35.0 GPa in the symmetrical diamond anvil cell at room temperature. Bulk modulus of $LiFePO_4/C$ was determined to be $130.1{\pm}10.3$ GPa. New peak appears at the d-spacing of 3.386 ${\AA}$ above 18 GPa, and another new one at 2.854 ${\AA}$ around 35 GPa. The crystallographic symmetry of the sample (i.e. orthorhombic) is apparently retained up to 35 GPa as no clear evidence for the phase transition into spinel structure has been observed. The pressure-induced volume change in the M1 site ($Li^+O_6$) is more significant than those in M2($Fe^{2+}O_6$) and $PO_4$ tetrahedral sites.

Growth and defect structures of undoped and heavily MgO-doped LiNbO3 single crystals (Undoped and heavily MgO-doped $LiNbO_3$ 결정의 성장 및 결함구조)

  • 김상수
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.5
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    • pp.447-453
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    • 1999
  • Congruent $LiNbO_3$ crystals with doped Mg and codoped with Mn or Fe were grown by the Czochralski method. It is known that the physical properties of $LiNbO_3$ depend strongly on the addition of Mg and transition metals. This is established by studying the following properties; XRD patterns, the phase transition temperature, energy of the fundamental absorption edge, the shape of the absorption band of the $OH^-$ vibration and lines of the ESR of $Fe^{3+},\; Mn^{2+}$. The position of the UV absorption edge and the shape and peak point of the absorption band of the $OH^-$ vibrational band changed monotonously up to a critical concentration of $Mg^{2+}$ ions. The mechanism of the incorporation of Mg ions changes at this concentration. The transition temperature was estimated by measuring the dielectric temperature behavior up to $1230^{\circ}C$ in a frequency range of 100Hz to 10MHz. EPR of $Mn^{2+}\;and\; Fe^{3+}$ ions were employed to investigated the Mg doping effects in the $LiNbO_3$ crystal. The increase of linewidths and the asymmetry of signals were observed in all crystals. New signals of $Fe^{3+}$ arising from the new centers were observed I the heavily Mg-doped crystals.

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Conceptual Design of Electrical Power System using Li-ion Cell Technology for a Satellite (리튬이온 전지 기술을 채용한 인공위성용 전력계 개념 설계)

  • Shin, Goo-Hwan;Park, Kyung-Hwa;Kim, Hyung-Myung;Lim, Jong-Tae
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.2
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    • pp.115-123
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    • 2007
  • This paper presents the conceptual design of the electrical power system using Li-ion cell technology for a satellite application. Compared to a conventional NiCd cell, a Li-ion cell has a lot of advantages such as an energy density, mass and a volume. Normally, a Li-ion cell has three times than conventional NiCd cells in a capacity such as a cell voltage. The normal voltage of a NiCd cell is around +1.2V and a Li-ion cell could be in +3.6V. However, the handling procedure for a Li-ion cell in charge and discharge might be difficult than a conventional NiCd cell, which means that the charge and discharge of each cell should be monitored and controlled by electrical circuits to prevent an over-charge and over-discharge. Therefore, in this paper we propose the design consideration and the characteristics of a Li-ion cell during charging and discharging battery packs in the point of view of electrical power system.

Electrochemical Performances of LiMn2O4:Al Synthesized by Solid State Method (고상법으로 합성한 LiMn2O4:Al의 전기화학적 특성)

  • Park, Hye-Jung;Park, Sun-Min;Roh, Gwang-Chul;Han, Cheong-Hwa
    • Journal of the Korean Ceramic Society
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    • v.48 no.6
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    • pp.531-536
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    • 2011
  • Al doped $LiMn_2O_4$ ($LiMn_2O_4:Al$) synthesized by several Al doping process and Solid State method. The Al contents in $Mn_{1-x}Al_xO_2$ for $LiMn_2O_4:Al$ were analyzed 1.7 wt% by EDS. The $LiMn_2O_4:Al$ confirmed cubic spinel structure and approximately 5 ${\mu}m$ particles regardless of three kinds of doping process by solid state method. In the result of electrochemical performances, initial discharge capacity had 115 mAh/g in case of $LiMn_2O_4$ and 111 mAh/g of $LiMn_2O_4:Al$ after 100th cycle at room temperature. But the capacity retention results showed that $LiMn_2O_4$ and $LiMn_2O_4:Al$ were 44% and 69% respectively in the 100th cycle at 60$^{\circ}C$. Therefore we are confirmed that $LiMn_2O_4:Al$ increased the capacity retention about 25% than $LiMn_2O_4$, thus the effect of Al dopping on $LiMn_2O_4$ capacity retention.

Surface Morphology and Characteristics of LiNbO3 Single Crystal by Helicon Wave Plasma Etching (Helicon Wave Plasma에 의해 식각된 단결정 LiNbO3의 표면 형상 및 특성)

  • 박우정;양우석;이한영;윤대호
    • Journal of the Korean Ceramic Society
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    • v.40 no.9
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    • pp.886-890
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    • 2003
  • The etching characteristics of a LiNbO$_3$ single crystal have been investigated using helicon wave plasma source with bias power and the mixture of CF$_4$, HBr, SF$_{6}$ gas parameters. The etching rate of LiNbO$_3$ with etching parameters was evaluated by surface profiler. The etching surface was evaluated by Atomic Force Microscopy (AFM). The surface morphology of the etched LiNbO$_3$ changed with bias power and the mixture of CF$_4$/Ar/Cl$_2$, HBr/Ar/Cl$_2$, and SF$_{6}$/Ar/Cl$_2$ parameters. Optimum etching conditions, considering both the surface flatness and etch rate were determined.

Conductivity and Electrochemical characterization of Lithium ion secondary battery electrolytes (리튬이온 2차 전지용 전해액의 이온전도도와 전기화학적 특성)

  • 임동규;이제혁;변문기;조봉희;김영호;우병원;나두찬
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1998.11a
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    • pp.295-298
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    • 1998
  • We have investigated ionic conductivity and electrochemical stability of the electrolytes containing organic solvent. Ion conductivities were measured between 10 and 80$^{\circ}C$, and electrochemical stabilities were determined by cyclic voltammetry on glassy carbon, platinum and aluminum electrodes. Ionic conductivity of electrolyte(EC:DEC=1:1) with IM LiPF$\_$6/ shows better than that of the other electrolytes having Li salts. The IM LiBF$_4$-PC electrolyte exhibits good electrochemical stability. IM LiPF$\_$6/ (EC:DEC=1:1) and IM LiPF$\_$6/ (EC:DMC=1:1) electrolytes are used for the high capacity of battery system.

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A study on synthesis of $Li_{x}Mn_{2}O_{4}$ for asecondary battery with various $MnO_{2}$ structure (다양한 $MnO_{2}$ 구조에 따른 2차전지용 $Li_{x}Mn_{2}O_{4}$ 합성에 관한 연구)

  • 김익진;이영훈;이종호;이재한;장동환;이경희;고영신
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.6 no.4
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    • pp.600-608
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    • 1996
  • Specific structural properties of Li intercalation reaction into the spinel relatedmanganese dioxide, $Li_{x}Mn_{2}O_{4}(0.2{\leq}x{\leq}2.0)$, are investigated by X-ray diffractional and electrochemical studies of Li/1M $LiClO_{4}$-propylene carbonate solution/$Li_{x}Mn_{2}O_{4}$ cell. The effect of the chemical composition and the reaction temperature on electrochemical parameter of $Li_{x}Mn_{2}O_{4}$ are studied by the phenomena of phase-transition, analysis of crystal lattice, fine structure, and thermal analysis. Treatment of the spinel $Li_{x}Mn_{2}O_{4}$ with aqueous acid was found to result in conversiton of $Li_{x}Mn_{2}O_{4}$ to nearly pure $MnO_{2}$, as evidenced by a reduction in the lattice constant $a_{c}$ from 8.255 to $8.031\;{\AA}$. At a composition range of $0.2{\leq}x{\leq}0.6$ in $Li_{x}Mn_{2}O_{4}$ the reduction proceeded in a homogeneous phase, which was characterized by a constant voltage of 3.9~3.7 V together with a lattice constant of $8.255\;{\AA}$.

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