Layered LnBaCo₂O_5+δ perovskite cathodes for solid oxide fuel cells: an overview and perspective

Aligned with an ever growing interest to reduce the operating temperature of solid oxide fuel cells (SOFCs) that offer technical and economical benefits, materials research in the area of SOFC cathodes is being directed toward mixed ionic-electronic conducting (MIEC) oxides with perovskite or related structures due to their promising performances particularly at reduced temperatures (T < 800 °C). This article focuses on the recent progress in the A-site ordered, layered LnBaCo₂O_5+δ perovskite family of MIECs that have been most actively investigated in the last decade. While significant progress has been made in understanding the promising cathode activity of LnBaCo₂O_5+δ, much efforts are being put towards further fine-tuning their properties by exploring their derivative chemical compositions and optimizing microstructures via advanced cathode fabrication processes. Based on the literature data, an overview of the structure–composition–property–performance relationships of the LnBaCo₂O_5+δ-based layered perovskite family is presented here. The challenges and perspectives of the LnBaCo₂O_5+δ-based cathodes are also discussed in relation to the conventional perovskite oxide cathodes.