Papers by Author: Shin Woo Kim

Abstract: The electrochemical properties of LiFePO4 as a cathode of lithium ion batteries considerably depend on a particle size of LiFePO4 and a condition of carbon coating. In this study, LiFePO4 powders were prepared using ultrasonic spray pyrolysis method, and then LiFePO4/C composites were made by infiltrating sucrose solution into LiFePO4 powders, drying, high-energy milling and annealing. The effects of high-energy milling were analyzed by comparing with electrochemical properties of powders synthesized without high-energy milling. It was found that the milling process drastically reduced the particle size of synthesized powders and electrical conductivity, and improved discharge capacity, cycle stability and rate performance.

Abstract: The ultrasonic spray pyrolysis method and proper heat treatments were applied in order to synthesize La0.8Sr0.2CrO3 (LSC) which is one of promising materials for separator in soild oxide fuel cell in this study. LSC powders that were sprayed at 800oC, heat-treated at 900oC for 5 hrs, ball-milled and finally heat-treated again at 1200oC for 20 hrs showed the average diameter of 0.3 *m and narrow size distribution to find particles above 0.5 *m hardly. In addition, the synthesizing temperature of LSC powders in ultrasonic spray pyrolysis method was 100
lower than conventional ball milling and drying method. Therefore the proper combination of heat treatment and milling process after spray pyrolysis was found to be very critical in synthesizing fine and uniform LSC powders. Finally, the sintering properties of these LSC powders were analyzed and compared with those of conventional ones.