Transition Metal‐Based Medium‐Entropy Composite Electrocatalyst for Stable and Efficient Li–O 2 Batteries

ABSTRACT 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 Li 2 O 2 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 Li 2 O 2 decomposition kinetics, suppressed Li 2 CO 3 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.