Polymeric Ionic Liquid‐Enabled <i>In Situ</i> Protection of Li Anodes for High‐Performance Li‐O₂ Batteries

Redox mediators (RMs) have shown promise in enhancing Li-O₂ battery cycling stability by reducing overpotential. However, their application is hindered by the shuttle effect, leading to RM loss and Li anode corrosion. Here, we introduce a polyionic liquid, poly (1-Butyl-3-vinylimidazolium bis(trifluoromethanesulfonylimine)) ([PBVIm]-TFSI) as an additive, showcasing a novel Li anode protection strategy for LiI-mediated Li-O₂ batteries. [PBVIm]⁺ cations migrate to the Li anode, forming a protective cationic shield that promotes uniform Li⁺ deposition. The addition of [PBVIm]-TFSI enhances the cycling stability, achieving 105 cycles at 200 mA⋅g^-1, compared to the cell with LiI which exhibited 38 cycles under the same conditions. Synchrotron X-ray tomography reveals the evolution of this protective layer, providing insights into its formation mechanism, in conjunction with XPS analysis. Our findings offer a new approach to Li anode protection in Li-O₂ batteries, emphasizing the critical role of interfacial engineering for battery performance.