Ruthenium functionalized graphene aerogels with hierarchical and three-dimensional porosity as a free-standing cathode for rechargeable lithium-oxygen batteries

Abstract

Although possessing extremely high energy density, lithium-oxygen (Li-O2) battery suffered from large charge overpotential, low round-trip efficiency and poor cycling life, which limited the practical application of this smart system. Ru particles functionalized graphene aerogels (Ru-GAs) were designed and directly used as a free-standing cathode for Li-O2 battery. The Ru-GAs showed hierarchical pores, which had the pore volumes of 2.8 and 14.1 cm3 g−1 below and above critical pore diameter of 100 nm. The Ru-GA cathode in Li-O2 battery delivered a high capacity of more than 12 000 mAh g−1 and excellent cycling retention, which was mainly attributed to the three-dimensional porosity, abundant active sites with Ru particles and chemical stability arising from the character of binder-free cathode. Based on the results of in situ gas chromatography–mass spectrometry analysis, the reaction mechanism during charge process in aprotic electrolyte was proposed by the theory of three oxidation stages.