Li–O2 batteries have attracted significant interest in the past decade owing to their superior high specific energy density in contrast to conventional lithium ion batteries. An 8.7-Ah Li–O2 pouch cell with 768.5 Wh kg−1 was fabricated and characterized in this investigation and the factors that influenced the electrochemical performance of the Li–O2 pouch cell were studied. In contrast to coin/Swagelok-type Li–O2 cells, it was demonstrated that the high-loading air electrode, pulverization of the Li anode, and the large-scale inhomogeneity of the large pouch cell are the major reasons for the failure of Li–O2 batteries with Ah capacities. In addition, safety tests of large Li–O2 pouch cells were conducted for the first time, including nail penetration, crushing, and thermal stability. It was indicated that a self-limiting mechanism is a key safety feature of these batteries, even when shorted. In this study, Li–O2 batteries were investigated in a new size and capacity-scale, which may provide useful insight into the development of practical pouch-type Li–O2 batteries.