Energy storage in current Li-ion batteries is limited by the positive intercalation electrode, which does not have a sufficiently high charge to weight ratio for many applications. Although research on new intercalation materials is intense, such research can only hope to double the energy stored. Breaking through this barrier to obtain a step change in energy storage is a major challenge. One of but a few possible alternative technologies is the Li-O2 battery in which the positive intercalation electrode is replaced with an O2 electrode. Here, O2 from air combines with Li+ within a porous carbon matrix to form lithium peroxide. Significantly, the charge density of this material far exceeds that of standard positive electrodes, opening the door to significantly higher charge storage approaching ten times that of today's LiCoO2 based cells. We were the first group to demonstrate that the O2 reduction in the presence of Li+ is reversible, i.e. Li-O2 batteries are rechargeable. However, many challenges remain before a viable Li-O2 battery can be realised and we are working on a number of these, for example, electrolyte and cathode stability. Indeed, we recently demonstrated a Li-O2 battery that is capable of 100 cycles at high capacity. Our work on optimising the porous O2 electrode is complemented by fundamental studies of model systems to probe fully the mechanism of reversible lithium peroxide formation. Watch an animation of how the Li-air battery operates.
