Needle-like NiCo₂O₄ Coated on Graphene Foam as a Flexible Cathode for Lithium-Oxygen Batteries

The electrochemical performance of non-aqueous lithium-oxygen batteries depends largely on the catalytic activity of the cathode, among which the architecture design plays an important role. In this paper, we present a novel free-standing, flexible cathode with needle-like NiCo₂O₄ coated on a three-dimensional graphene framework. The hierarchical structure exhibits a macropore nest of graphene foam along with mesopore decoration of NiCo₂O₄ nanorods, which can provide fast diffusion or adsorption for the reactants and abundant active site for the oxygen reduction reaction and oxygen evolution reaction. With the novel cathode, the battery delivers a capacity about 5000 mAh g⁻¹ at a current density of 400 mA g⁻¹, and can cycle stably at least 80 times without obvious degradation at the capacity limitation of 1000 mAh g⁻¹. This flexible cathode shows potential application in foldable electronic devices.