The Li-Air (O2) Battery

New science and new materials will play a crucial role in efforts to transform energy storage. Such a transformation is vital in order to reduce CO2 emissions in the long-term. The lithium-ion battery is not only one of the most successful technologies of the past 20 years; it is also one of the best examples of a technology driven by materials research. However, the maximum energy storage possible with lithium-ion batteries is too low for key applications in the long-term; such as electric vehicles and storing electricity from intermittent sources, e.g. wind, solar, tidal. To go beyond the horizon of lithium-ion is a formidable challenge; there are few options. Here the promise and challenges of two, the aqueous and non-aqueous Li-air batteries, will be discussed. Both the aqueous and non-aqueous lithium-air batteries are generating a great deal of interest because theoretically they possess a specific energy more than 5 times that of a conventional Li-ion battery [1-11]. Specific energies and energy densities more than double those of today’s Li-ion batteries are required to extend the range of electric vehicles to 500 km. The typical non-aqueous lithium-air battery configuration consists of a lithium anode, an organic solvent + lithium salt electrolyte and a porous cathode composed of a carbon black, a catalyst and binder (Fig. 1). On discharge, O2 from the atmosphere enters the porous cathode, where it is reduced forming a solid product that can be oxidized upon charging. Figure 1: Schematic representation of a rechargeabl