Mushroom-like Au/NiCo₂O₄ nanohybrids as high-performance binder-free catalytic cathodes for lithium-oxygen batteries

Li-O₂ (or Li-air) batteries currently represent a hot topic in the field of energy storage and conversion. The electrochemical performance of the Li-O₂ battery depends largely on the material and architecture of the catalytic cathode. In this work, we propose a unique design of a binder-free catalytic cathode for Li-O₂ batteries. The electrode consists of a novel mushroom-like Au/NiCo₂O₄ nanohybrid on three-dimensional graphene (3D-G) grown directly on the skeleton of Ni foam. The Au/NiCo₂O₄/3D-G catalyst exhibits a good catalytic effect for Li-O₂ batteries, where Au directs the growth of Li₂O₂ mainly on the top of mushroom-like Au/NiCo₂O₄, and induces the crystallization of Li₂O₂ into the thin-flake or thin-film form that is found to decompose relatively easily compared with the large-particle form upon charging. Mushroom-like NiCo₂O₄ provides additional catalytic sites and acts as the support for both Au and Li₂O₂. A Li-O₂ battery with the Au/NiCo₂O₄/3D-G catalyst can deliver a capacity of around 1275 mA h g^-1 at 42.5 mA g^-1. When the capacity is limited at 510 mA h g^-1, the Li-O₂ battery can sustain stable cycling up to 40 times.