Single-Atomic Zn/Co-Nx Sites Boost Solid-Soluble Synergistic Catalysis for Lithium-Oxygen Batteries.

Abstract

Lithium-oxygen batteries have attracted widespread attention owing to their superior theoretical energy density. However, they are obstructed by sluggish oxygen reduction (ORR) and evolution reaction (OER) kinetics at air cathodes. Herein, different from using single solid or soluble catalysts, solid-soluble synergistic catalysis is proposed to conjointly enhance ORR/OER performances. During discharge, single-atomic zinc/cobalt embedded in nitrogen-doped carbon (Zn, Co-N/C) is judiciously engineered as a solid catalyst to regulate the growth pathway of Li2O2 and promote ORR kinetics. During charge, a typical redox mediator (RM, LiI) is added as a soluble catalyst to permit efficient oxidation of Li2O2. Of note is that the atomic Zn/Co-Nx sites can chemically adsorb oxidized iodine (I2) and accelerate OER kinetics, which plays a decisive role in eliminating the shuttle effect of I3-/I2 to the Li anode. Coupling a single-atomic catalyst with restricted oxidized iodine offers an exceptional discharge capacity, remarkably low polarization, and superior long-term cycling stability.