Transition Metal-Based Medium-Entropy Composite Electrocatalyst for Stable and Efficient Li–O₂ Batteries

Lithium–oxygen batteries (LOBs) are emerging as promising next-generation energy storage systems due to their high theoretical energy density. Despite this potential, practical applicability is limited by issues such as insulating Li₂O₂ accumulation, large overpotentials, and pronounced cathode corrosion during repeated cycling. In this study, we present a highly active and durable NiFeCr transition metal-based medium-entropy composite (MEC) electrocatalyst with a near-equiatomic composition, synthesized through a facile pulse current electrodeposition (PCE) approach, which enhances both the compositional uniformity of the catalyst and enables controllable nanoscale synthesis. The optimized MEC, featuring a synergistic balance between catalytic activity and stability, comprises Ni and Fe as catalytic centers and Cr as a protective passivating element, and delivers outstanding electrochemical behavior and superior corrosion resistance by minimizing parasitic reactions. Consequently, this MEC achieves greatly accelerated Li₂O₂ decomposition kinetics, suppressed Li₂CO₃ formation, and superior cycling stability. Owing to its optimal balance of catalytic activity and durability, the MEC reaches a high energy efficiency of 83.9% at 500 mA g⁻¹ with a fixed capacity of 500 mAh g⁻¹, and maintains stable cycling over 200 cycles. This work, to the best of our knowledge, is the first to demonstrate a medium-entropy-based electrocatalyst for LOBs, providing a compelling pathway toward the development of highly active and corrosion-resistant cathode catalysts.