Efficient Modulation of Electron Pathways by Constructing a MnO2-x@CeO2 Interface toward Advanced Lithium-Oxygen Batteries.

Abstract

A major challenge for Li-O2 batteries is to facilely achieve the formation and decomposition of the discharge product Li2O2, and the development of an active and synergistic cathode is of great significance to efficiently accelerate its formation/decomposition kinetics. Herein, a novel strategy is presented by constructing a MnO2-x@CeO2 heterostructure on the porous carbon matrix. When it was used as a cathode for Li-O2 batteries, excellent electrochemical performances, including low overpotential, large discharge capacity, and superior cycling stability were obtained. Series theoretical calculations were conducted to reveal the mechanism for the reversible battery reactions and explain how Li2O2 interacts with the MnO2-x@CeO2 interface. Apart from the electronic ladders formed between MnO2-x 3d and CeO2 4f orbitals, which can act as a highly efficient "electron transfer expressway", the specific adsorption of MnO2-x and CeO2 with Li2O2 molecules contributes to the enhanced anchoring force of Li2O2 and delocalization of the electron cloud on the Li-O bond. Thanks to the constructed heterostructure and synergistic effect, filmlike Li2O2 can be formed through a surface pathway, and when charging, it accelerates the separation of electrons and Li+ in Li2O2, thus achieving fast redox kinetics and low overpotential.