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Jo Y.N.,Kyung Hee University | Prasanna K.,Kyung Hee University | Park S.J.,ECOPRO | Lee C.W.,Kyung Hee University
Electrochimica Acta | Year: 2013

We have investigated the crystallographical, morphological, and electrochemical behaviors of synthe-sized four different compositions of xLi2MnO3(1-x)Li[MnyNizCo 1-y-z]O2cathode active materials usingX-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), and galvanostaticcycler. The four different compositions of cathode active materials demonstratea commonly angularshape of primary particles, but agglomerated spherical shape in appearance. All the attempted compo-sitions of xLi 2MnO3(1-x)Li[MnyNizCo 1-y-z]O2cathodes deliver a specific discharge capacity of between220 and 242 mAh/g at room temperature when cycled between 2.5 and 4.6 V versus Li/Li+at C/10 rate. © 2013 Elsevier Ltd. All rights reserved. Source

Sin B.C.,University of Ulsan | Lee S.U.,University of Ulsan | Jin B.-S.,Korea Electrotechnology Research Institute | Kim H.-S.,Korea Electrotechnology Research Institute | And 4 more authors.
Solid State Ionics | Year: 2014

As a cathode material for lithium rechargeable batteries, fluorine-substituted lithium iron manganese phosphate (LiFe0.4Mn 0.6PO4-δFδ, δ = 0 to 0.09) without additional carbon sources was synthesized by solid state reaction by using planetary mill grinding and characterized by XRD, SEM, TEM with EDX mapping, XPS and galvanostatic charge-discharge testing. LiFe 0.4Mn0.6PO4-δFδ samples were shown to have single-phase crystalline nature with X-ray diffraction analysis and enhanced discharge capacity at various C-rates as compared to bare LiFe0.4Mn0.6PO4. Among them, the LiFe 0.4Mn0.6PO3.970F0.03 with the best cycleability exhibited an initial discharge capacity of 153 mAh g- 1 at 0.1 C and 113 mAh g- 1 at 1 C. It is proven that the enhanced electrochemical properties of LiFe0.4Mn0.6PO 4-δFδ by fluorine substitution are incorporated with not only electrical conductivity but also stability of crystal structure. First principle computations were also performed to determine the optimum molar ratio of Fe and Mn and evaluate the improvement in electrical conductance through fluorine substitution to oxygen. © 2014 Elsevier B.V. Source

Vediappan K.,Kyung Hee University | Park S.-J.,ECOPRO | Kim H.-S.,Korea Electrotechnology Research Institute | Lee C.W.,Kyung Hee University
Journal of Nanoscience and Nanotechnology | Year: 2011

Novel cathode active materials, Li[Li x(Ni 0.3Co 0.1Mn 0.6) 1.x]O 2 (x = 0.09, 0.11) composed of rod-like primary particles, but aggregated spherical shape in appearance, were synthesized. The newly Mn-rich cathode active materials were then adopted as cathodes to show the benefits for Li-ion rechargeable batteries. The results show that to use proper nano-scaled particles as a cathode and to make homogeneous particle sizes have great improvements on electrochemical performances, probably ascribed to enhancement of charge transfer kinetics and lower cell impedance at high voltage region (∼4.6 V). The electrochemical performances of Mn-rich cathodes were investigated by cycler (BT2000, Arbin), comparing electrochemical behaviors between room and elevated temperature, 55 °C. The morphology of cathodes having nano-scaled particles of active materials and the Mn-rich cathode active materials were investigated using field emission scanning electron microscope (FE-SEM) and field emission transmission electron microscope (FE-TEM), also the crystalline phase identification was analyzed by high power X-ray diffractometer (XRD). Copyright © 2011 American Scientific Publishers All rights reserved. Source

Vediappan K.,Kyung Hee University | Jo Y.N.,Kyung Hee University | Park S.-J.,ECOPRO | Kim H.-S.,Korea Electrotechnology Research Institute | Lee C.W.,Kyung Hee University
Japanese Journal of Applied Physics | Year: 2012

The high rate capability of Mn-rich Li[Li x (Ni 0.3Co 0.1Mn 0.6) 1-x]O 2 (x = 0.11) cathode active materials is investigated by cycling the cell at a given rate for five cycles and keeping the cell idle under thermal control chamber for 10 h and the same process repeating up to 30 cycles. The before and after thermal aging of Mn-rich cathode materials deliver the initial discharge capacity of 153 and 157.32mAh g -1 up to 30 cycles and also it is maintained the average specific discharge capacity of 140mAh g -1 for before thermal aging and more than 90% capacity retention. After thermal aging of cathode materials have maintain the average specific discharge capacity of 155mAh g -1 and more than 97% capacity retentions. During charging, they are not oxidized further; Ni 2+ and at least part of Co 3+ ions are oxidized to higher valence states. During the discharge reactions, the small amount of Mn 3+ reduced to the Mn 4+ and some part of Ni 3+ ions are reduced to Ni 4+. Also the Co 3+ ions are fully reduced to the Co 4+ state, which due to thermal aging studies does not have major affects in the Mn-rich layered structure under thermal control chamber. These thermal aging analyses are essential to achieve a deeper understanding of the structural defects and safety views for Li-ion batteries to use in electric vehicle technologies. © 2012 The Japan Society of Applied Physics. Source

Park J.-H.,Chungbuk National University | Kang D.-C.,Chungbuk National University | Park S.-J.,ECOPRO | Shin C.-H.,Chungbuk National University
Journal of Industrial and Engineering Chemistry | Year: 2015

MnO2 was prepared by a simple redox method using potassium permanganate and various Mn2+ precursors (Mn-chloride, Mn-nitrate, Mn-acetate, and Mn-sulfate) and the influence of Mn-precursors in the CO oxidation was investigated. The light-off temperatures (T50%) in the dry conditions increased as following order: Mn-chloride2 and H2O vapor, the T50% value significantly shifted to higher temperatures compared to its value in the absence of them. MnO2 catalyst prepared from Mn-chloride exhibited a high quantity of labile oxygen and better reducibility compared with the other catalysts. © 2014 The Korean Society of Industrial and Engineering Chemistry. Source

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