Three-dimensional graphene membrane cathode for high energy density rechargeable lithium-air batteries in ambient conditions

Lithium-air batteries have attracted significant interest for applications in high energy density mobile power supplies, yet there are considerable challenges to the development of rechargeable Li-air batteries with stable cycling performance under ambient conditions. Here we report a three-dimensional (3D) hydrophobic graphene membrane as a moisture-resistive cathode for high performance Li-air batteries. The 3D graphene membrane features a highly interconnected graphene network for efficient charge transport, a highly porous structure for efficient diffusion of oxygen and electrolyte ions, a large specific surface area for high capacity storage of the insulating discharge product, and a network of highly tortuous hydrophobic channels for O-2/H2O selectivity. These channels facilitate O-2 ingression while retarding moisture diffusion and ensure excellent charge/discharge cycling stability under ambient conditions. The membrane can thus enable robust Li-air batteries with exceptional performance, including a maximum cathode capacity that exceeds 5,700 mAh/g and excellent recharge cycling behavior (> 2,000 cycles at 140 mAh/g, and > 100 cycles at 1,400 mAh/g). The graphene membrane air cathode can deliver a lifetime capacity of 100,000-300,000 mAh/g, comparable to that of a typical lithium ion battery cathode. The stable operation of Li-air batteries with significantly improved single charge capacities and lifetime capacities comparable to those of Li-ion batteries may offer an attractive high energy density storage alternative for future mobile power supplies. These batteries may provide much longer battery lives and greatly reduced recharge frequency.