Enhancing the Reaction Kinetics and Reversibility of Li–O_2 Batteries by Multifunctional Polymer Additive

摘要

As a potential candidate for next-generation energy storage systems, Li–O_2 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 superoxideinduced parasitic reactions. Uniform Li~+ flux gives evenly-distributed Li_2O_2 that can be completely decomposed during OER. In addition, PTFEMA protects Li-metal against corrosion from O_2, 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.