Enhanced ionic conductivity and grain boundary conduction behavior of YSZ-LSGM heterostructure composite electrolyte for SOFCs

Y 0.15 Zr 0.85 O 1.93 (YSZ) has emerged as a crucial solid electrolyte material for modern solid oxide fuel cells (SOFCs) and oxygen sensors, prized for its exceptionally high oxygen ionic conductivity. However, further enhancement of its oxygen ionic conductivity is essential to optimize SOFCs energy efficiency and mitigate high-temperature electrode degradation. Despite extensive efforts involving various doping strategies, this critical challenge remains unsolved. To address this issue, a novel YSZ-LSGM heterostructure composite electrolyte was developed by adding a minor La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 2.85 (LSGM) phase into the YSZ phase, and its performance as an electrolyte was systematically evaluated. LSGM’s high ionic conductivity promotes rapid oxygen ion transport across grain boundaries. The heterogeneous interface between YSZ and LSGM also favors oxygen ion transport, significantly enhancing both the grain boundary conductivity and the total ionic conductivity of the heterostructure composite. Remarkably, the YSZ-30 wt% LSGM composite demonstrates approximately 8 times in total conductivity (0.0008 S/cm at 750 °C) compared to pure YSZ (0.0001 S/cm at 750 °C). Most strikingly, the YSZ-30 wt% LSGM’s grain boundary conductivity is around 24 times higher than the YSZ electrolyte’s. These findings highlight the synergistic advantages of the heterostructure composite electrolyte, which combines the excellent compatibility of YSZ with the superior ionic conductivity of LSGM. This study not only provides a promising strategy for developing advanced composite electrolyte materials but also opens a new avenue for further research in high-performance SOFC technologies.