(Georgia Institute of Technology, 2015-07-13)
Gu, Wentian
Highly porous carbon plays an important role in the fabrication of electrode materials, both for high-power supercapacitors and Li-ion batteries. It qualifies as suitable electrodes for high-power supercapacitors. The first part of this work discuss the effect of oxygen-containing functional groups (including hydroxyl, carbonyl and carboxyl groups) on the self-discharge behavior of carbon-based electrical double layer supercapacitors (EDLCs). The effects of carbon pore size and pore size distribution, pore alignment, electrolyte solvent and conducting ion are also studied. Based on the understandings of these multiple factors which have impact on the performance of carbon-based EDLCs, a novel S-doped activated carbon synthesized by carbonization and simultaneous activation of S-based polymers, which is almost free of bottle-neck pores and performs excellent capacitance and capacitance retention, is developed. Besides their essential role in carbon-based EDLCs, highly porous carbon materials have also been intensively studied as structural scaffold and conductive additives to assist the highly capacitive but poorly conductive active electrode materials for Li-ion batteries. The second part of this work discuss the application of mesoporous activated carbon spheres as structural matrix and conductive network which enables higher capacity, better rate retention and longer cycle life of transition metal fluoride-based cathode materials, compared to the simple mixture of non-porous conductive carbon filler and the active material.
(Georgia Institute of Technology, 2011-03-23)
Gu, Wentian
To fulfill the potential of carbon nanotube (CNT) as thermal interface material (TIM), the packing density of CNT array needs improvement. In this work, two potential ways to increase the packing density of CNT array are tested. They are liquid precursor(LP)CVD and cycled catalyst deposition method. Although LP-CVD turned out to be no help for packing density increase, it is proved to enhance the CNT growth rate. The packing density of CNT array indeed increases with the cycle number. The thermal conductivity of the CNT array increases with the packing density. This work is believed to be a step closer to the real life application of CNT in electronic packaging industry.