A TEMPO-grafted multi-functional cathode with strong anchoring ability towards redox mediators for high energy efficiency Li-O2 batteries

Soluble redox mediators (RMs) with favorable contact interface are considered to be an effective approach for high efficient lithium-oxygen (Li-O2) batteries. However, the shuttling effect of oxidized RMs from the cathode would lead to the degradation of the RMs’ functionality and poor cycling stability. Herein, TEMPO was anchored into three-dimensional porous [email protected]/NF conductive substrate ([email protected]@PPy-TEMPO/NF) and directly utilized as a self-supporting cathode for Li-O2 battery. This novel cathode serves multiple functions as redox mediator, abundant reaction center for lithium ion, as well as electron conduction matrix. The battery perform with a high discharge specific capacity of 6.9 mAh cm−2 and a low overpotential of 0.6 V similar with 4-OH-TEMPO in the electrolyte. The detailed catalysis mechanism of the immobilized TEMPO in improving the electrochemical performance has also been studied. During discharging, the cation-π effect between the conductive polypyrrole and lithium ions helps to realize the "isomorphic growth" of Li2O2. During charging, the TEMPO-immobilized electrochemical oxidation to TEMPO+ provides more direct contact with the discharge products, resulting in rapid chemical oxidation of Li2O2. The ingenious design and in-depth mechanism study provide a new avenue to address the shuttle effect of RMs and design an advanced cathode for Li-O2 batteries.