LiFSI-based and DOL-free Ultralight Electrolyte Design for Long-cycling and High-energy-density Lithium-sulfur Battery

Lithium-sulfur (Li-S) battery provides a promising solution toward high-energy and cost-effective energy storage. Unlike dense electrodes of lithium-ion batteries, the highly porous S cathode of Li-S battery uptakes a large amount of electrolyte, which significantly lowers the energy density of the battery. To address this challenge, we report here an ultralight electrolyte (ULE) that simultaneously possesses a low mass density and high Li + ion conductivity. ULE utilizes the lightweight lithium-bis(fluorosulfony)imide (LiFSI) salt and removes the heavy 1,3-dioxolan (DOL) solvent, therefore significantly reducing the density from 1.20 to 0.89 g cm -1. Moreover, LiFSI offers LiF-rich interphase at the Li metal anode to suppress the polysulfide corrosion, and its high donor number also improve the solubility of polysulfides to enhance the capacity of the S cathode. The exclusion of DOL can circumvent the harmful DOL polymerization and S cathode agglomeration. Consequently, pouch cells show 42.5% higher energy density and 133% longer cycle life in ULE than in conventional electrolyte.