Synthesis of Ag/Co@CoO NPs anchored within N-doped hierarchical porous hollow carbon nanofibers as a superior free-standing cathode for Li-O2 batteries

To develop high-performance and efficient bifunctional electrocatalysts for Li-O-2 batteries, a promising new material is developed in this study, which consists of hierarchical porous hollow carbon nanofibers (HCNFs) with Ag/Co@CoO nanoparticles immobilized inside. This material is prepared using a facile and convenient coaxial electrospinning method, followed by a simple heat treatment. The Ag/Co@CoO-HCNF cathode shows low polarization and excellent cycle performance. A combination of structural characterizations (e.g., scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman scattering spectroscopy, and the Brunauer-Emmett-Teller method) and electrochemical analyses shows that the excellent battery performance of the Ag/Co@CoO-HCNF cathode can be attributed to its hierarchical porous structure, high surface area and high content of active sites combined with the synergetic interactions between Ag and Co@CoO as well as the improved electrical conductivity. Notably, the introduction of Ag may promote the Li2O2 to grow and crystallize into nanosheets due to the synergetic interactions between Ag and CoO. The petal-like Li2O2 discharge products formed on the Ag/Co@CoO-HCNF cathode are more readily decomposed than the film-like Li2O2. Our findings provide a reference for designing free-standing high-performance hollow-structured Ag/Co@CoO hybrid electrodes by coaxial electrospinning for non-aqueous Li-O-2 batteries. (C) 2018 Elsevier Ltd. All rights reserved.