Boosting Li–O₂ Battery Performance and Stability With ZnI₂: Synergistic Effects on Anode Protection and Cathode Activation

Abstract

Recent advancements in lithium–oxygen (Li–O₂) batteries have focused on incorporating redox mediators (RMs) into the electrolyte to address challenges of low energy efficiency and poor cycle life. However, various soluble RMs induce parasitic reactions with Li, compromising the anode stability. In this study, we design optimized Li–O₂ batteries by introducing ZnI₂ into the electrolyte, which serves a dual function: facilitating a stable LiZn/Zn protective layer on the Li metal anode and acting as an effective RM. The in situ formed LiZn/Zn layer prevents I₃⁻ shuttle effects, stabilizing the Li anode and promoting uniform Li plating and stripping. Additionally, the ZnI₂ mediator facilitates rapid conversion of the I⁻/I₃⁻ and I₃⁻/I₂ redox couples at the cathode, contributing to a more reversible and lower overpotential Li₂O₂ cycle. Notably, ZnI₂ enhances early-stage LiO₂ formation, verified by in situ Raman spectroscopy, which supports uniform sheet-like Li₂O₂ deposition and contributes to stable cycling. These synergistic effects caused a significant reduction in the charge potential to less than 3.4 V, enabling over 800 stable cycles. This approach provides a viable pathway to achieving high energy density and long cycle life in Li–O₂ batteries, positioning them for practical applications.

Keywords

zinc iodide / redox mediator / LiZn/Zn protect layer / stable SEI layer / Li–O₂ batteries

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