High-Performance Li-O2 Batteries with Controlled Li2O2 Growth in Graphene/Au-Nanoparticles/Au-Nanosheets Sandwich

The working of nonaqueous Li-O-2 batteries relies on the reversible formation/decomposition of Li2O2 which is electrically insulating and reactive with carbon and electrolyte. Realizing controlled growth of Li2O2 is a prerequisite for high performance of Li-O-2 batteries. In this work, a sandwich-structured catalytic cathode is designed: graphene/Au-nanoparticles/Au-nanosheets (G/Au-NP/Au-NS) that enables controlled growth of Li2O2 spatially and structurally. It is found that thin-layer Li2O2 (below 10 nm) can grow conformally on the surface of Au NPs confined in between graphene and Au NSs. This unique crystalline behavior of Li2O2 effectively relieves or defers the electrode deactivation with Li2O2 accumulation and largely reduces the contact of Li2O2 with graphene and electrolyte. As a result, Li-O-2 batteries with the G/Au-NP/Au-NS cathode exhibit superior electrochemical performance. A stable cycling of battery can last 300 times at 400 mA g(-1) when the capacity is limited at 500 mAh g(-1). This work provides a practical design of catalytic cathodes capable of controlling Li2O2 growth.