▎ 摘　　要

These years, Li-O-2 batteries attract wide interest because of its high theoretical energy density. However, the catalytic activity and porous structure of cathode remains a great challenge. In this work, we developed a hierarchical porous graphene foam to serve as a battery cathode, which has much richer active sites for cathodic reaction and channels for Li+ transfer and O-2 diffusion. The cathode exhibits a superior specific capacity as high as 9559 mAh g(-1) at 57 mA g(-1) and remains a high-rate capability of 3988 mAh g(-1) at an increased current density of 285 mA g(-1). Benefiting from the well-designed cathode structure, the battery can be stably operated for 150 cycles with a stable voltage profile and voltage efficiency up to 65%. The well-designed graphene has a potential to be a superior free-standing cathode to other carbon-based materials due to its good combination of its hierarchical and porous structure, large surface area, abundant defects and excellent mechanical stability. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.