The performance degradation of composite cathodes of La0.6Sr0.4Co0.2Fe0.8O3-δ and Gd-doped ceria (LSCF-GDC), prepared by impregnating the porous GDC scaffold with a nitrate solution containing La, Sr, Co and Fe in desired composition, is investigated at 750 C and open circuit in air for 500 hrs. The performance of the impregnated LSCF-GDC composite cathodes deteriorates after testing at 750 o C for 500 hrs; the electrode polarization resistance (Rp) increases from 0.38 to 0.83 Ω cm 2 , and the electrode ohmic resistance (Ro) increases from 1.79 to 2.14 Ω cm 2. The grain growth and coarsening of impregnated LSCF nanoparticles are responsible for the performance degradation of the cathodes. XPS analysis shows the enrichment of cobalt on the surface of the infiltrated LSCF-GDC cathodes and such surface segregation could also contribute to the degradation of the electrocatalytic activity of the cathodes. Introducing MgO and LaNi0.6Fe0.4O3 phases can effectively suppress

The content of oxygen vacancy, as the intercalation places of oxygen during the oxygen ion intercalation process, has a significant influence on the electrochemical properties of the perovskite pseudocapacitance. To enhance the electrochemical performance of perovskite supercapacitors, we propose a novel strategy of the plasma etching technique to improve the oxygen vacancy concentration of the LaCoO3 electrode. The influence of plasma composition and etching time on the etching effect was investigated. Results show that the etching effect of H2 is better than that of Ar. The specific capacitance of the LaCoO3 electrode etched for 5 min in 10 sccm H2 and 90 sccm Ar increased from 339.8 F g–1 to 706.9 F g–1. The asymmetric supercapacitor assembled with graphene oxide delivers a high energy density of 47.64 Wh kg–1 at a power density of 804.4 W kg–1 and still maintains 35.02 Wh kg–1 at a high power density of 37 080 W kg–1. After 4000 cycles at 5 A g–1, there is little degradation of specific capacitance with the Coulombic efficiency maintaining a high level of 96%. It can be concluded that the plasma etching technique is an efficient way to improve the energy storage performance of perovskite pseudocapacitive materials.

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