(The) role of electrolyte anions on $Li_2S$ growth realizing high-performance Li-S batteries

Abstract

Passivation of a sulfur cathode by uncontrolled growth of insulating lithium sulfide imposes a limitation in achieving high sulfur utilization of lithium-sulfur batteries. In electrolytes based on solvents with high Gutmann Donor Number, sulfur utilization can be augmented

however, this approach reveals the drawback of violent lithium metal corrosion. Here we report that particulate lithium sulfide growth can be achieved when using a salt anion with a high donor number such as bromide or triflate. The use of bromide leads to ~95 % sulfur utilization by suppressing electrode passivation. More importantly, the electrolytes with high-donor number salt anions are notably compatible with lithium metal electrodes. The approach enables a high sulfur-loaded cell with areal capacity higher than 4 mA h $cm^{-2}$ and high sulfur utilization (> 90 %). This finding offers a simple but practical strategy to modulate lithium sulfide growth mode, while conserving the stability for high-performance lithium-sulfur batteries.