Current and further trajectories in designing functional materials for solid oxide electrochemical cells: A review of other reviews

Complex oxides are an important class of materials with enormous potential for electrochemical applications. Depending on their composition and structure, such complex oxides can exhibit either a single conductivity (oxygen-ionic or protonic, or n-type, or p-type electronic) or a combination thereof generating distinct dual-conducting or even triple-conducting materials. These properties enable their use as diverse functional materials for solid oxide fuel cells, solid oxide electrolysis cells, permeable membranes and gas sensors. The literature review shows that the field of solid oxide materials and related electrochemical cells has a significant level of research engagement, with over 8,000 publications published since 2020. The manual analysis of such a large volume of material is challenging. However, by examining the review articles, it is possible to identify key patterns, recent achievements, prospects, and remaining obstacles. To perform such an analysis, the present article provides, for the first time, a comprehensive summary of previous review publications that have been published since 2020, with a special focus on solid oxide materials and electrochemical systems. Thus, this study provides an important reference for researchers specializing in the fields of solid state ionics, high-temperature electrochemistry, and energy conversion technologies.