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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 | Year: 2010

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.

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 | Year: 2010

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.

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 | Year: 2010

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.

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 | Year: 2010

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.

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