Enhancing the Reaction Kinetics and Reversibility of Li–O₂ Batteries by Multifunctional Polymer Additive

Abstract As a potential candidate for next‐generation energy storage systems, Li–O₂ batteries (LOBs) with their attractive theoretical energy density have triggered great interest. However, tough issues of sluggish oxygen reduction reaction/oxygen evolution reaction (ORR/OER) kinetics, poor rechargeability, superoxide‐derived side reactions, and Li‐metal corrosion in LOBs limit their practical applications. Herein, a poly(2,2,2‐trifluoroethyl methacrylate) (PTFEMA) additive is introduced into the typical electrolyte, giving superior cycling performance to LOBs. Enabling strong solvation of Li⁺, PTFEMA regulates a uniform Li⁺ flow at the cathode and anode sides of LOBs. Induced by homogeneous Li⁺ flux and favorable adsorption with superoxide species, PTFEMA promotes superoxide transformation in the ORR and inhibits superoxide‐induced parasitic reactions. Uniform Li⁺ flux gives evenly‐distributed Li₂O₂ that can be completely decomposed during OER. In addition, PTFEMA protects Li‐metal against corrosion from O₂, superoxide, and byproducts shuttle. Hence, accelerated ORR/OER kinetics, facilitated rechargeability, suppressed superoxide‐derived side reactions, and well‐protected Li‐metal can be simultaneously realized with PTFEMA, resulting in significantly enhanced electrochemical performance of LOBs. This electrolyte engineering involving facile multifunctional polymer additives provides a practical alternative to complex componential optimization toward commercial LOBs and gives insight to the understanding of uniform Li⁺ flux on reaction kinetics and reversibility.