Improving Cycling Stability in Li-O2 Batteries through in-situ SEI Formation Using 4-fluoro-2-iodoaniline: Interface Morphology and Kinetic Insights via Operando XRD and X-ray CT

Lithium-oxygen (Li-O 2 ) batteries have recently shown improved kinetics of oxygen reduction/evolution reaction (ORR/OER) by redox mediators (RMs). Effective strategies are needed to protect the Li anode from side reactions with solvents, reduced oxygen species, and soluble redox intermediates. In this work, 4-fluoro-2-iodoaniline (4-F-2-IAn) is employed as a self-defensive redox mediator (RM) to facilitate the decomposition of Li 2 O 2 . Operando XRD is carried out to study the catalytic kinetics during OER process. Additionally, 4-F-2-IAn participates in in-situ formation of a stable SEI layer, which protects the Li anode through suppressing the shuttle effect, thereby promoting the cycling stability. Moreover, the evolution of the cell interface is visualized using synchrotron X-ray computed tomography (SX-CT). This work provides a good insight into Li anode protection and an in-depth exploration of in situ approaches to obtaining the interface morphology and kinetic insights into Li 2 O 2 decomposition in RM-based Li-O 2 batteries. 4-F-2-IAn acts as a self-defensive redox mediator, accelerating Li 2 O 2 decomposition while forming a protective SEI layer that suppresses the shuttle effect and enhances Li anode stability. • A self-defensive redox mediator (4-F-2-IAn) accelerates Li 2 O 2 decomposition • 4-F-2-IAn facilitates the in-situ formation of a durable SEI, effectively suppressing shuttle reactions and Li corrosion. • Operando synchrotron XRD confirms enhanced OER kinetics and reduced charge overpotential. • In situ SX-CT visualizes stabilized Li-anode morphology throughout cycling. • Coupled redox mediation and interfacial protection substantially improve durability.