Synthesis of a metallic mesoporous pyrochlore as a catalyst for lithium–O2 batteries.

The lithium–O2 ‘semi-fuel’ cell based on the reversible reaction of Li and O2 to form Li2O2 can theoretically provide energy densities that exceed those of Li-ion cells by up to a factor of five. A key limitation that differentiates it from other lithium batteries is that it requires effective catalysts (or ‘promoters’) to enable oxygen reduction and evolution. Here, we report the synthesis of a novel metallic mesoporous oxide using surfactant templating that shows promising catalytic activity and results in a cathode with a high reversible capacity of 10,000 mAh g(−1) (∼1,000 mAh g(−1) with respect to the total electrode weight including the peroxide product). This oxide also has a lower charge potential for oxygen evolution from Li2O2 than pure carbon. The properties are explained by the high fraction of surface defect active sites in the metallic oxide, and its unique morphology and variable oxygen stoichiometry. This strategy for creating porous metallic oxides may pave the way to new cathode architectures for the Li–O2 cell.