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Yeongju, South Korea

Lee S.-Y.,Kangwon National University | Park J.H.,Sungkyunkwan University | Park P.,LG Corp | Kim J.H.,LG Corp | And 6 more authors.
Journal of Solid State Electrochemistry

Multi-walled carbon nanotube (MWCNT) with bundle-type morphology was introduced as a new functional additive working as a particle connector or an expansion absorber in the anodes of lithium-ion batteries. By controlling the dispersion process, the MWCNT bundles were successfully divided and dispersed between the host particles. The composite anode consisting of rounded shape natural graphite and 2 wt.% of MWCNT exhibited the capacity of 300 mAh g -1 at 3 C rate and excellent cyclability. The well-dispersed MWCNT bundles made it possible to relieve the large strains developed at high discharge C rates and to keep the electrical contact between the host particles during repeated intercalation/deintercalation. This study has also emphasized that when high C-rate applications of lithium-ion batteries are targeted, it is important to get optimum content of MWCNT as well as uniform dispersion of their bundles in the composite anodes. © 2009 Springer-Verlag. Source

Doh C.-H.,Korea Electrotechnology Research Institute | Veluchamy A.,Korea Electrotechnology Research Institute | Veluchamy A.,CSIR - Central Electrochemical Research Institute | Lee D.-J.,Korea Electrotechnology Research Institute | And 5 more authors.
Bulletin of the Korean Chemical Society

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. Source

Doh C.-H.,Korea Electrotechnology Research Institute | Lee J.-H.,Korea Electrotechnology Research Institute | Lee J.-H.,Kyungnam University | Lee D.-J.,Korea Electrotechnology Research Institute | And 5 more authors.
Physica Scripta T

The electrochemical and thermochemical properties of a silicon-graphite composite anode for lithium ion batteries were evaluated. The electrochemical properties were varied by the condition of pretreatment. The electrochemical pretreatment of constant current (C/10) and constant potential for 24 h showed specific discharge and charge capacities of 941 and 781 mA h g-1 to give a specific irreversible capacity of 161 mA h g-1 and a coulombic efficiency of 83%. The initial cycle as the next cycle of pretreatment showed a specific charge capacity (Li desertion) of 698 mA h g-1 and a coulombic efficiency of 95%. Coulombic efficiency at the fifth cycle was 97% to clear up almost all of the irreversible capacity. During the pretreatment cycle to the fourth cycle, the average specific charge capacity was 683 mA h g -1 and the cumulative irreversible capacity was 264 mA h g -1. Exothermic heat values based on the specific capacity of the discharged (Li insertion) electrode of silicon-graphite composite for the temperature range of 50-300 °C were 2.09 and 2.21 J mA-1h -1 for 0 and 2 h as time of pretreatment in the case of just disassembled wet electrodes and 1.43 and 1.01 J mA-1h-1 for 12 and 24 h as time of pretreatment in the case of dried electrodes, respectively. © 2010 The Royal Swedish Academy of Sciences. Source

Jo Y.N.,Korea Electronic Technology Institute | Kim Y.,Korea Electronic Technology Institute | Kim J.S.,Korea Electronic Technology Institute | Song J.H.,Korea Electronic Technology Institute | And 5 more authors.
Journal of Power Sources

Two types of Si-graphite (Si-C) composites are synthesized and evaluated for anode materials of lithium secondary batteries. The mechano-chemical milling and the rotational impact blending methods are applied to synthesize two types of Si-C composites. Graphite powders having Si on the surface (type A) is synthesized by mechano-chemical milling using the pitch as a binder. Si embedded inside the graphite particle (type B) is synthesized by rotational impact blending. The loading level of Si is about 20 wt% for both type Si-C composites. The location of Si is verified by observing cross sectional images of particle and conducting EDS mapping. The initial discharge capacity of type B has larger value than that of type A, while the type A shows better cycle performance than type B. The efficiency of first cycle is about 87% for both types A and B. © 2010 Elsevier B.V. All rights reserved. Source

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