Scandium-stabilized zirconia electrolyte for intermediate-temperature solid oxide fuel cells: phase stability regulation, bilayer/composite structure design and machine learning-guided optimization strategies

Abstract

Scandium-stabilized zirconia (ScSZ) offers significantly higher ionic conductivity than conventional yttria-stabilized zirconia in the 600–800 °C range, making it an excellent electrolyte candidate for intermediate-temperature solid oxide fuel cells (IT-SOFCs). However, large-scale application is fundamentally constrained by scandium's high cost, coupled with intermediate-temperature structural degradation—such as cubic phase instability, oxygen-vacancy ordering, and dopant segregation—and detrimental interfacial reactions with electrodes. This paper systematically reviews recent advances in ScSZ electrolytes, focusing on phase stability, ion transport mechanisms, and structural optimization. We analyze atomic-scale oxygen-vacancy dynamics and elucidate how multivalent co-doping synergistically regulates stability and conductivity through ionic radius and electronic structure modifications. Furthermore, from the broader perspective of structural optimization, we summarize research on advanced fabrication techniques and multilayer/composite architectures aimed at promoting densification, suppressing phase transitions, and enhancing interfacial compatibility. Finally, the emerging applications of machine learning in high-throughput material screening, dynamic defect evolution, and electrolyte structural optimization are explored, outlining future research directions for IT-SOFCs.