▎ 摘　　要

A challenge still remains to develop high-performance and cost-effective air electrode for Li-O-2 batteries with high capacity, enhanced rate capability and long cycle life (100 times or above) despite recent advances in this field. In this work, a new design of binder-free air electrode composed of three-dimensional (3D) graphene (G) and flower-like delta-MnO2 (3D-G-MnO2) has been proposed. In this design, graphene and delta-MnO2 grow directly on the skeleton of Ni foam that inherits the interconnected 3D scaffold of Ni foam. Li-O-2 batteries with 3D-G-MnO2 electrode can yield a high discharge capacity of 3660 mAh g(-1) at 0.083 mA cm(-2). The battery can sustain 132 cycles at a capacity of 492 mAh g(-1) (1000 mAh g(carbon)(-1)) with low overpotentials under a high current density of 0.333 mA cm(-2). A high average energy density of 1350 Wh Kg(-1) is maintained over 110 cycles at this high current density. The excellent catalytic activity of 3D-G-MnO2 makes it an attractive air electrode for high-performance Li-O-2 batteries.