Detailed electrochemical analysis of high-performance nanoscaled La0.6Sr0.4CoO 3-delta thin film cathodes

Nanoscaled and nanoporous La 0.6Sr 0.4CoO 3-? thin film cathodes derived from metal-organic precursors (metal organic deposition, MOD) with a film thickness of 200 nm and an average grain and pore size in the sub 100 nm regime were investigated with the focus on the reaction kinetics by a systematic temperature (T = 400 - 600°C) and oxygen atmosphere (pO 2 = 0.01 - 0.5 atm) variation. Electrochemical impedance spectroscopy was applied, followed by a detailed data analysis including calculating the distribution function of relaxation times (DRT) and CNLS fit. Five processes were identified. Four processes are temperature activated, whereas one process at low frequencies exhibits a slight deactivation with temperature. Furthermore, the three low and mid frequency processes are oxygen partial pressure dependent, whereas the two high frequency processes remain unaffected by pO 2 variations. Extremely low polarization losses as low as ASR pol = 9 m? cm 2 at 600°C were measured in synthetic air.