High performance thermal expansion offset LSCF-SZM cathodes of IT-SOFCs

Abstract

One big risk for commercial solid oxide fuel cells (SOFCs) is the potential delamination between cathode and electrolyte layers. It can be effectively alleviated by the thermal expansion offset strategy proposed in 2021, i.e., conventional cathode composited with the negative thermal expansion oxides. Here novel composite cathodes designated as La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF)-xSm_0.85Zn_0.15MnO₃ (SZM) (x = 0, 5, 10, 15, and 20 wt.%) are developed. Random phase boundaries with apparent lattice distortion are formed between LSCF and SZM phases. The best electrochemical performance is obtained for x = 10%. The corresponding peak power density at 923–723 K is 1.151–0.147 W·cm⁻², which is 57–69% higher than that (0.731–0.087 W·cm⁻²) for x = 0. More importantly, markedly enhanced long-term and thermal cycling stability is also obtained. Results of electrical conductivity, electrochemical impedance spectroscopy (EIS) and distribution of relaxation time (DRT) results further confirm that improved thermal match between cathode and electrolyte layers should be responsible for the high performance of intermediate temperature SOFCs (IT-SOFCs).