Improving the durability of cobaltite cathode of solid oxide fuel cells - a review

Solid oxide fuel cells (SOFCs) are highly efficient, low-emission, and fuel-flexible energy conversion devices. However, their commercialization has lagged due to the lack of long-term durability. Among several performance degradation mechanisms, cathode degradation and elemental inter-diffusion of the electrolyte and cathode has been identified as the predominant factors. In the most common SOFC systems, a cobalt-based perovskite material is used, for example LSC or LSCF. These cobalt-based materials offer mixed conductivity and higher concentration of oxygen vacancies as compared to LSM at lower operating temperature leading to favorable reduction kinetics. However, the presence of cobalt results in higher cost, higher thermal expansion co-efficient (TEC) mismatch and most importantly leads to rapid degradation. Various elements like strontium, cobalt, cerium, chromium, or zirconium accumulate or deposit at the electrode-electrolyte interface, which results in sluggish reaction kinetics of the oxygen reduction reaction (ORR). These elements react to form secondary phases that have lower ionic and electronic conductivity, cover active reaction sites, and eventually lead to cell and system deterioration. Over the past decade, several studies have focused on preventative and protective measures to prolong SOFC lifetime which includes novel fabrication techniques, introduction of new layers, addition of thin films to block the cation transport. Such efforts to prevent the formation of insulating phases and decomposition of the cathode have resulted in a remarkable improvement in long-term stability. In this review paper, current research on leading mechanisms responsible for the degradation of cobaltite cathode of solid oxide fuel cell has been summarized and durability improvement strategies of cobalt-based SOFC cathodes have been discussed.

Automated summary

Solid oxide fuel cells (SOFCs) are efficient and environmentally friendly energy conversion devices. However, their commercialization has been hindered by the lack of long-term durability. Cathode degradation and inter-diffusion of electrolyte and cathode materials have been identified as the main factors contributing to performance degradation. Cobalt-based perovskite materials, commonly used in SOFCs, offer favorable reduction kinetics but suffer from rapid degradation. Various elements accumulate or deposit at the electrode-electrolyte interface, leading to sluggish reaction kinetics and cell deterioration. Preventative and protective measures, such as novel fabrication techniques and addition of thin films, have improved the long-term stability of cobalt-based SOFC cathodes. This review paper summarizes the leading mechanisms of cobaltite cathode degradation and discusses strategies for enhancing the durability of cobalt-based SOFC cathodes.