A High Capacity Gas Diffusion Electrode for Li-O₂ Batteries

The very high theoretical specific energy of the lithium-air (Li-O₂) battery (3500 Wh kg^-1) compared with other batteries makes it potentially attractive, especially for the electrification of flight. While progress has been made in realizing the Li-air battery, several challenges remain. One such challenge is achieving a high capacity to store charge at the positive electrode at practical current densities, without which Li-air batteries will not outperform lithium-ion. The capacity is limited by the mass transport of O₂ throughout the porous carbon positive electrode. Here it is shown that by replacing the binder in the electrode by a polymer with the intrinsic ability to transport O₂, it is possible to reach capacities as high as 31 mAh cm^-2 at 1 mA cm^-2 in a 300 µm thick electrode. This corresponds to a positive electrode energy density of 2650 Wh L^-1 and specific energy of 1716 Wh kg^-1, exceeding significantly Li-ion batteries and previously reported Li-O₂ cells. Due to the enhanced oxygen diffusion imparted by the gas diffusion polymer, Li₂O₂ (the product of O₂ reduction on discharge) fills a greater volume fraction of the electrode and is more homogeneously distributed.