Design and Preparation of Cathode Catalysts for High-Performance Lithium-Oxygen Batteries

Abstract

The lithium-oxygen batteries have received considerable attention recently due to their high theoretical energy densities, which is highly desirable for long-range electric vehicles. However, their poor electrochemical performance, particularly the large overpotential, makes the practical application of Li-O2 battery full of challenge. In a typical prototype, non-aqueous Li-O2 battery is composed of a catalytic cathode, a lithium anode, and an organic Li+ conducting electrolyte. During the discharge process, oxygen molecules are reduced and reacted with the Li+ ions from the electrolyte (oxygen reduction reactions, ORRs), leading to the formation of dissoluble Li2O2 attached to the porous cathode. These Li2O2 species would reversibly decompose into Li+ ions and oxygen (oxygen evolution reactions, OERs) in the following charging process. Thus, the design of cathode catalysts with high ORR and OER reactivity, and porous structures with appropriate pore size for the permeation of O2 is of particular importance. In addition, polymer binders would react with superoxide Li2O2, consequently leading to the instability of Li-O2 batteries. It is also highly desired to develop novel binder-free cathode materials. Herein, strategies have been proposed for the preparation of free-standing porous structures promote the ORR and OER activities for high-performance Li-O2 batteries.