Progresses in lithium-sulfur and lithium air batteries

Abstract

Li-ion batteries today exceed at least by a factor of 2.5 any competing technology thanks to the high value of energy density, i.e. 150 Whkg -1 and 650 Whl-1. Due to their unique features, these batteries are the power sources of choice for the portable electronic market (including popular products such as cellular phones, lap-top computers, mp3s, etc) and are aggressively entering in the power tool equipment market and, in particular, in the emerging sustainable vehicle market. However, the present Li-ion battery technology, although a commercial reality, is not yet at such at a performance level to meet the power requirements of efficient hybrid or electric vehicles. Reduction in cost, enhancement in safety and rate, and, especially improvement in energy density, are mandatory requirements. We will show in this presentation that jumps in energy density may only be achieved by totally renewing the battery chemistry. The most significant examples of these novel high energy technologies are provided by the lithium-sulphur and the lithium-air systems. On the other hand, several issues still prevent the practical implementation of these superbatteries. In the case of the lithium sulphur battery these mainly include the solubility in the electrolyte of the discharge products, the high resistivity of the products and of the reactants, and the safety concern associated with the use of a lithium metal anode. The lithium-air system suffers of the low kinetics of the oxygen electrode, the poor stability of common electrolytes in the cell environment and, again, of the safety concern on the lithium metal anode. We will report here the steps carried out in our laboratory to properly address these issues and discuss how our results may be of interest for the progress of these advance battery technologies.