• HE-LSCF air electrode exhibits superior ORR activity with a low polarization resistance of 0.042 Ω·cm² at 700°C, significantly outperforming conventional LSCF.
• Tubular R-SOCs with HE-LSCF achieve a high peak power density of 1.18 W·cm⁻² in fuel cell mode and a promising electrolysis current density of −0.52 A·cm⁻² at 1.5 V.
• The high-entropy design effectively mitigates Sr segregation, enhancing structural stability and durability over 180 h of reversible cycling.
• This work demonstrates that A-site high-entropy engineering is a viable strategy to boost both activity and robustness of perovskite air electrodes for R-SOCs.