Regenerative redox mediator for the suppression of dead lithium for lithium sulfur pouch cell

Abstract

Lithium sulfur batteries are persistently investigated by the research community due to their high energy density property. However, in order to get such performance, based on the current pouch cell strategy, less electrolyte and more stacking electrodes need be applied, leading to the aggravated dendrite growth, dead lithium accumulation and electrolyte depletion. In this context, we report a regenerative redox mediator strategy, targeting the operation window of the lithium sulfur batteries. The redox mediator can spontaneously consume the dead lithium on the anode, then be re-oxidized on the cathode through electrochemical process. Based on this design, the lithium sulfur pouch cell can be fully charged at 1C for more than 140 cycles. Moreover, the regeneration mechanism is studied by in situ UV-vis spectroscopy. This work not only validates the effectiveness of redox mediator for improving the high rate charging and cycling of lithium sulfur pouch cells, but also excludes the invalid mediator type and provides the design concept, guiding the future development of high rate charging strategy for lithium sulfur batteries.