Novel nanomaterials for lithium ion batteries and lithium sulfur batteries

Publication Type:
Thesis
Issue Date:
2014
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Rechargeable energy storage devices are being seen as having a crucial role in the powering of myriad portable electronic devices, electrical vehicles and hybrid electrical vehicles. The properties of electrode materials are of extreme significance for the electrochemical performances of both lithium-ion (Li-ion) batteries and lithium-sulfur (Li-S) batteries. Tin-graphene nanocomposites were prepared by a combination of microwave hydrothermal and one-step hydrogen gas reduction. When applied as an anode material in Li-ion batteries, tin-graphene nanocomposite exhibited a high lithium storage capacity of 1407 mAh g-1. The materials also demonstrated an excellent high rate capacity and a stable cycle performance. Graphene-carbon nanotube hybrid materials were successfully prepared that demonstrated high reversible lithium storage capacity, high Coulombic efficiency and excellent cyclability. Fe₂O₃-CNT-graphene nanosheet hybrid materials were synthesized using a chemical vapor deposition method, exhibiting a high specific capacity of 984 mAh•g-1 with a superior cycling stability and high rate capabilities. High quality single crystalline graphene sheets were prepared by the ambient pressure chemical vapor deposition method using acetylene as the carbon source and coral-like iron with body-centered-cubic structure as the catalyst. It showed high lithium storage capacity and excellent cyclability. Hierarchical three-dimensional carbon-coated mesoporous Si nanospheres@graphene foam nanoarchitectures were successfully synthesized by a thermal bubble ejection assisted chemical-vapor-deposition and magnesiothermic reduction method. The materials exhibited superior electrochemical performances, including a high specific capacity of 1200 mAh/g at the current density of 1 A/g, excellent high rate capabilities and outstanding cyclability. Mesoporous Co₃O₄ nanoflakes with interconnected architecture were successfully synthesized by means of a microwave-assisted hydrothermal and low-temperature conversion method. Co₃O₄ nanoflakes delivered a high specific capacity of 883 mAh/g at 0.1 C current rate and stable cycling performances even at higher current rates as anodes of Li-ion batteries. The synthesis of graphitic hyperbranched hollow carbon nanorods encapsulated sulfur composites were employed as cathode materials for Li-S batteries. The sulfur composite cathodes delivered a high specific capacity of 1378 mAh/g at 0.1 C current rate and exhibited a stable cycling performance. Multi-shelled hollow carbon nanospheres-sulfur composites with a high percentage of sulfur loading (86 wt. %) were synthesized by an aqueous emulsion approach and in-situ sulfur impregnation, delivering a high specific capacity of 1350 mAh/g and excellent capacity retention. By adopting a dual confinement strategy, poly(3,4- ethylenedioxythiophene) (PEDOT) coated micro/mesoporous carbon nanocube encapsulated sulfur (P@CNC-S) composites were synthesized. The P@CNC-S composites exhibited superior performances, including a high specific capacity, extended cycle life and outstanding rate capabilities.
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