High‐Entropy Perovskites for Solid Oxide Cells: Mechanistic Insights to Practical Applications

ABSTRACT Solid oxide cells (SOCs) are high‐temperature electrochemical platforms for efficient energy conversion and chemical production in both fuel‐cell and electrolysis modes. Practical deployment remains constrained by fuel‐electrode coking, limited transport, and sluggish kinetics at reduced temperatures, electrolyte instability, surface segregation, interfacial degradation, and chromium poisoning at the oxygen electrode. High‐entropy perovskite oxides (HEPOs) offer an emerging route to address these coupled constraints, as multication design can reshape defect chemistry, transport, and thermochemical stability within a single perovskite framework. This review summarizes recent progress in HEPOs for SOC applications, covering fundamental concepts, structural families, and structure–property relationships, followed by synthesis and processing strategies for microstructure control. Mechanistic understanding is discussed through in situ diffraction and spectroscopy, together with advanced electron microscopy, to track dynamic structures and interfaces under operation. Applications in electrodes and electrolytes are highlighted, with representative gains in activity, durability, and tolerance to CO 2 , H 2 O, and chromium‐related stressors. Finally, key challenges and research opportunities are discussed, and practical design principles are proposed for next‐generation SOC materials.