Boosting Cathode Activity and Anode Stability of Lithium-Sulfur Batteries with Vigorous Iodic Species Triggered by Nitrate.

ABSTRACT

Lithium-sulfur (Li-S) battery with a sulfurized polyacrylonitrile cathode is a promising alternative to Li-ion systems. However, the sluggish charge transfer of cathode and accumulation of inactive Li on anode remain persistent challenges. An advanced electrolyte additive with function towards both cathode and anode holds great promise to address these issues. Herein, we present a new strategy to boost sulfur activity and rejuvenate dead Li simultaneously. In the polar electrolyte containing I2-LiNO3 additives, I3 -/IO3 - are triggered significantly by the reaction between NO3 - and I- ions. The I3 -/IO3 - are reactive to insulated Li2S product of cathode and inactive Li on anode, thus accelerating the conversion reaction of sulfur and recovering Li sources back to battery cycling. The in situ/ex situ spectroscopic and morphologic monitoring reveal the crucial role of iodine in promoting Li2S dissociation and inhibiting dendritic Li growth. With the modified electrolyte, the symmetric Li||Li cells deliver a lifespan of 4000 h with an overpotential less than 12 mV at 0.5 mA cm-2. For Li-S cells, 100 % capacity retention up to thousands of cycles and enhanced rate capability are available. This work demonstrates a feasible strategy on electrolyte engineering for practical applications of Li-S batteries.