High-entropy perovskite air electrodes investigated with advanced 3D imaging

Recent studies have shown that the high-entropy perovskite La_0.2Pr_0.2Nd_0.2Sm_0.2Sr_0.2CoO_3-δ (LPNSSC) delivers excellent performance as an air electrode in both SOFC and SOEC operation. For such high-performance electrode materials, minimising microstructural limitations is essential to achieve maximum cell efficiency. Optimising the electrode morphology and the quality of the electrode/electrolyte interface can greatly improve the electrochemical performance and long-term stability of solid oxide cells. While many studies simulate the behaviour of electrodes with idealised (artificial) microstructures, researchers often struggle to directly link real microstructural features to cell performance. Our approach combines electrochemical testing with detailed 3D analysis of actual electrodes to break down cell performance into its contributing factors. This study focuses specifically on how the air electrode microstructure influences overall cell behaviour.
In this work, anode-supported button cells incorporating LPNSSC as the air electrode material were tested and the results were correlated with 3D imaging of the electrode microstructure. By varying the grain size distribution of the LPNSSC powders, electrodes with significantly different microstructures were produced. To evaluate oxygen transport rates toward electrochemically active regions, the cell performance was measured under different air flow conditions. At the highest air flow, the total polarisation resistance (anode plus cathode) at 800°C ranged from 0.13 to 0.24 Ω cm² at 0.7 V in SOFC mode. Detailed 3D imaging was used to explain these observations. Particular attention was given to the combined roles of porosity, tortuosity and internal surface area of the porous air electrodes in determining cell performance. Symmetrical cells were employed to isolate the contributions of the air electrode from overall cell performance and correlate the results with an analytical model developed for porous mixed conductors.