The use of redox mediators for enhancing utilization of Li₂S cathodes for advanced Li-S battery systems

The development of Li₂S electrodes is a crucial step toward industrial manufacturing of Li-S batteries, a promising alternative to Li-ion batteries due to their projected two times higher specific capacity. However, the high voltages needed to activate Li₂S electrodes, and the consequent electrolyte solution degradation, represent the main challenge. We present a novel concept that could make feasible the widespread application of Li₂S electrodes for Li-S cell assembly. In this concept, the addition of redox mediators as additives to the standard electrolyte solution allows us to recover most of Li₂S theoretical capacity in the activation cycle at potentials as low as 2.9 V_Li, substantially lower than the typical potentials >4 V_Li needed with standard electrolyte solution. Those novel additives permit us to preserve the electrolyte solution from being degraded, allowing us to achieve capacity as high as 500 mAhg^-1 _Li2_S after 150 cycles with no major structural optimization of the electrodes.