Evolution of electrolyte materials for solid oxide electrolysis cells: From traditional oxides to high-performance ionic conductors

Abstract

Solid oxide electrolysis cells (SOECs) represent one of the most thermodynamically efficient pathways for large-scale green hydrogen production, yet their commercial viability remains constrained by the performance limitations of ceramic electrolyte materials. This review provides a comprehensive and critically integrated analysis of the full spectrum of oxide-ion conducting electrolytes for SOEC applications, spanning from established vacancy-mediated conductors to emerging interstitial-transport frameworks. This work systematically bridges nanoscale ion-transport mechanisms with stack-level technoeconomic realities, offering a unified evaluation framework for electrolyte selection and design. Conventional electrolytes are assessed with emphasis on their degradation pathways under SOEC-specific redox conditions. The review then examines underexplored material families, critically assessing their ionic transport mechanisms, phase stability, and compatibility with SOEC operating environments. A dedicated section addresses machine-learning and DFT-assisted electrolyte discovery, highlighting both capabilities and current limitations in predicting stability and degradation behavior. Technoeconomic analysis reveals that area-specific resistance, electrolyte thickness optimization, and manufacturing yield collectively determine the levelized hydrogen cost far more significantly than raw material pricing alone. This integrative roadmap identifies the unresolved challenges impeding intermediate-temperature SOEC commercialization and defines priority research directions toward durable, high-conductivity electrolytes compatible with industrial hydrogen production targets. • Correlates structure-defect chemistry with oxide-ion conductivity in SOEC electrolytes. • Critically compares conventional and emerging fast-ion conductors. • Links atomic-scale transport to macroscopic durability and efficiency. • Establishes design rules for high-performance, cost-effective hydrogen production.