A bidirectional phase-transfer catalyst for Li-O2 batteries with high discharge capacity and low charge potential

Abstract

Li-O2 batteries require catalysts to solve the problem of sluggish oxygen-related reaction kinetics. However, the solid catalysts and redox mediators are intrinsically deficient due to poor solid contacts and shuttle problems, respectively. Here, we report lithium phthalimide-N-oxyl (LiPINO) as a phase transfer catalyst (PTC) for promoting Li2O2 formation and its reversible decomposition through the solution-phase reactions. The interaction between LiPINO and oxygen species in the electrolyte enables the high dissolution and stability of oxygen species, the fast charge transfer at liquid-solid interfaces and superior kinetics, and the suppressed side reactions. The efficient bidirectional catalytic activity and high stability of LiPINO capacitate batteries with a highly improved discharge capacity (11400 mAh g−1), a largely lowered charge potential (3.14 V) and an extended cycle life (more than 200 cycles) both in O2 and air. Our understanding of the phase-transfer catalysis towards the Li-O2 electrochemistry and the discovery of the PTC with superior activity and stability provide deep insights into the design of the most reliable catalysts for Li-O2 batteries.