Papers by Author: Jae Kook Kim

Abstract: TiO2 nanoparticles were synthesized from a triethylene glycol solution of titanium isopropoxide (Ti(O-iPr)4) by refluxing at 270°C for 12 hrs. The as-prepared sample was heated at 600 °C for 3 hrs in order to study the thermal stability of the sample. The X-ray diffraction patterns of the samples were well indexed to the anatase phase. The field emission TEM images show uniform spherical morphologies with average sizes of 25 nm. The electrochemical measurements revealed that the discharge capacities of the heated sample exhibited high capacities and good rate performances without capacity fading during extended cycles, due to their electrochemically beneficial highly crystalline structures, nano-sized particles, and uniform distribution.

Abstract: LiFePO₄/C nanocomposite was synthesized by the polyol process without any further heating as a post step and its properties were compared to LiFePO₄ with no carbon. The X-ray diffraction patterns of all samples were indexed on the basis of the orthorhombic olivine-type structure. The field emission-SEM and TEM images of the nanocomposite showed agglomerated larger particles with rod type mixed with carbon nanoparticles. The initial discharge capacity of LiFePO₄/C nanocomposite showed 166 mAh/g at a current density of 0.1 mA/cm² in the voltage range of 2.5-4.2 V without capacity fading during the 20 cycles. Furthermore, the nanocomposite appeared more enhanced high rate performance, compared with the result of LiFePO₄ with no carbon, due to the existence of conductive agents such as carbon which suppresses particle growth and exhibits improved electronic conductivity and lithium ion diffusivity, simultaneously.