Anchored Mediator Enabling Shuttle–Free Redox Mediation in Lithium–Oxygen Batteries

Abstract

Redox mediators (RMs) are considered an effective countermeasure to reduce the large polarization in lithium–oxygen batteries. Nevertheless, achieving sufficient enhancement of the cyclability is limited by the trade–offs of freely mobile RMs, which are beneficial for charge transport but also trigger the shuttling phenomenon. Here, we successfully decoupled the charge–carrying redox property of RMs and shuttling phenomenon by anchoring the RMs in polymer form, where physical RM migration was replaced by charge transfer along polymer chains. Using a model system of a polymer, PTMA (2,2,6,6–tetramethyl–1–piperidinyloxy–4–yl methacrylate), based on the well–known RM tetramethylpiperidinyloxyl (TEMPO), it is demonstrated that PTMA is capable of functioning as a stationary RM, preserving the redox activity of TEMPO. The efficiency of RM–mediated Li2O2 decomposition remains remarkably stable without the consumption of oxidized RMs or degradation of the lithium anode, resulting in marked improvement of the performance of the lithium–oxygen cell.