Strategies to mitigate Sr segregation of the LSCF oxygen electrode for solid oxide cells

Abstract

The electrocatalytic activity and long-term stability of the oxygen electrode are critical for solid oxide cells (SOCs) operating in both fuel cell and electrolysis cell modes to realize large-scale energy storage. The La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) oxygen electrode exhibits high mixed ionic–electronic conductivity, excellent catalytic activity, and a thermal expansion coefficient compatible with common electrolytes. However, Sr segregates to the LSCF surface under the effects of lattice elastic energy and electrostatic interactions, forming insulating phases such as SrO and SrCO₃, or diffusing into the electrolyte interfaces, particularly yttria-stabilized zirconia (YSZ), generating insulating and chemically inert SrZrO₃ compounds. These phenomena significantly degrade the catalytic performance and operational stability by reducing active surface sites and increasing the interfacial polarization resistance. Over the past decade, multiple strategies have been developed to suppress Sr segregation and enhance electrode performance. This review systematically examines the driving forces and key factors underlying Sr segregation and critically evaluates recent mitigation approaches from the perspective of both theoretical insights and practical implementation.