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

The working of nonaqueous Li-O₂ 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-O₂ 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-O₂ 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.