Sung Eun Jo1,Byung Chan Yang1,Hyong June Kim1,Jihwan An1
Seoul National University of Science & Technology1
Sung Eun Jo1,Byung Chan Yang1,Hyong June Kim1,Jihwan An1
Seoul National University of Science & Technology1
Solid Oxide Fuel Cell (SOFC) is a promising next-generation energy conversion device with high efficiency, fuel versatility, and easy scalability. SOFC usually operate at high temperature(600 ~ 1000<sup>o</sup>c), where performance degradation is followed by structure disruption. For example, lanthanum strontium cobalt ferrite(LSCF) is the popular material for SOFC cathode. Strontium in perovskite material segregates at elevated temperature. Exsolution of Sr occurs SrOx at the surface of the cathode and SrZrO3 formation between cathode and electrolyte. The secondary phase diminishes ORR activity and escalates polarization resistance by blocking active sites.<br/>To increase the durability of LSCF cathode, porous ZrO<sub>2</sub> overcoat by atomic layer deposition (ALD) method is widely reported. ALD is an atomic-level deposition process composed of separated precursor and reactant steps. Nanoscale film thickness can be precisely controlled by the designated ALD cycle number. ALD is widely used in the semiconductor industry and is also an advantageous tool for improving electrochemical device performance and durability. Conformal nature and thickness/doping controllability of ALD are known to allow nanoscale surface modification for porous electrodes of SOFC. Nevertheless, conventional ALD coating is limited in synthesizing perfectly conformal overcoats for complex anode structures.<br/>In this study, we report on the use of powder ALD to conformally coat LSCF powders for SOFC cathodes. Bare LSCF powders are ball-milled, situated in the rotary module assembled with the ALD station, and are coated with ALD ZrO<sub>2</sub>. As powders have extremely high area-to-volume ratio, static exposure mode for precursor infiltration between nanoscale air gap. The rotary powder holder rotates for powder agitation during the ALD process. In the electrochemical test, the cells with bare LSCF cathodes (no ALD), LSCF cathodes with conventional ALD (C-ALD) and with power ALD (P-ALD)-coated ZrO2 overcoats are compared. While the cell with ALD-coated cathode showed better thermal stability possibly due to the suppression of Sr segregation, the P-ALD cathode with 5nm-thick ZrO<sub>2</sub> overcoat effectively suppresses degradation than the C-ALD cathode due to more conformal coating.