Anion-redox nanolithia cathodes for Li-ion batteries

The development of lithium-air batteries is plagued by a high potential gap (>1.2 V) between charge and discharge, and poor cyclability due to the drastic phase change of O 2 (gas) and O x' (condensed phase) at the cathode during battery operations. Here we report a cathode consisting of nanoscale amorphous lithia (nanolithia) confined in a cobalt oxide, enabling charge/discharge between solid Li 2 O/Li 2 O 2 /LiO 2 without any gas evolution. The cathode has a theoretical capacity of 1,341 Ah kg '1, a mass density exceeding 2.2 g cm '3, and a practical discharge capacity of 587 Ah kg '1 at 2.55 V versus Li/Li +. It also displays stable cycling performance (only 1.8% loss after 130 cycles in lithium-matched full-cell tests against Li 4 Ti 5 O 12 anode), as well as a round-trip overpotential of only 0.24 V. Interestingly, the cathode is automatically protected from O 2 gas release and overcharging through the shuttling of self-generated radical species soluble in the carbonate electrolyte.