Abstract
Lithium-oxygen (Li-O2) batteries have drawn intensive attention owing to their exceptionally high theoretical specific energy. However, their further advancement has been significantly hindered by challenges including low discharge capacity, poor energy efficiency, severe parasitic reactions, etc. Here, we report a highly Li-O2 battery operated via a new quenching/mediating mechanism that relies on the direct chemical reactions between a versatile molecule and superoxide radical/Li2O2 nanoparticles. The battery exhibits a 46-fold increase of discharge capacity, a low charge over-potential of 0.7 V, and an ultralong cycle life > 1400 cycles. The tailor-designed organic molecule features two redox mediator-active 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) moieties bridged by a quenching-active perylene diimide (PDI) backbone. The PDI-TEMPO molecule not only acts as a soluble redox mediator to catalyze both discharge and charge reactions, but also serves as a reusable superoxide radical quencher to chemically react with superoxide species generated during the operation of Li-O2 batteries, leading to the formation of Li2O2 nanoparticles which are much easier to decompose than the conventional toroidal-shaped Li2O2. The all-in-one molecule as a multifunctional additive can tackle various issues of parasitic reactions associated with superoxide radicals, singlet oxygen, high over-potentials, and lithium corrosion, beyond the mere combination of PDI and TEMPO moieties’ functionalities. The molecular design of multifunctional additives combining the capabilities of redox mediators, superoxide radical quencher and beyond opens a new avenue for developing high-performance Li-O2 batteries.
A long-life lithium-oxygen battery via a molecular quenching/mediating mechanism
