Suppressing Redox Shuttling with Lithiated Nafion-Modified Separators for Li-O₂ Batteries

Although the employment of redox mediator (RM) is an effective strategy to reduce the overpotential by avoiding the direct electrochemical oxidization of Li₂ O₂ during charging, an unexpected redox shuttling in Li-O₂ system leads to RM degradation and continuous deterioration of Li anode, finally resulting in a limited cycling stability. Here, a functional lithiated Nafion-modified separator was firstly introduced to inhibit the shuttle effect by coulombic/electrostatic interactions in RM-involved Li-O₂ batteries. The fabrication of the separator involved easily accessible raw materials and an easy-to-operate process, which made it suitable for large-scale production. The enhancement of lithiated process on electrochemical properties was systematically investigated. In addition, the influence of decorated amount on cycling stability was also studied. Furthermore, the functional contribution of lithiated Nafion on inhibition of redox shuttling and the working mechanism for cells with and without as-prepared separators were proposed. This work can give an insight into the development of functional separator (i. e., activity issue) and the suppression of parasitic reactions (i. e., selectivity issue) in Li-O₂ batteries.