In situ protection of a sulfur cathode and a lithium anode via adopting a fluorinated electrolyte for stable lithium-sulfur batteries

Lithium-sulfur (Li−S) batteries are regarded as one of the most promising next-generation energy storage systems due to their high theoretical energy density and low material cost. However, the conventional ether-based electrolytes of Li−S batteries are extremely flammable and have high solubility of lithium polysulfides (LiPS), resulting in a high safety risk and a poor life cycle. Herein, we report an ether/carbonate co-solvent fluorinated electrolyte with a special solvation sheath of Li+, which can prevent the formation of dissoluble long-chain LiPS of the sulfur cathode, restrict Li dendrite growth at the anode side, and show fire resistance in combustion experiments. As a result, the proposed Li−S batteries with 70 wt% sulfur content in its cathode deliver stable life cycle, low self-discharge ratio, and intrinsic safety. Therefore, the unique passivation characteristics of the designed fluorinated electrolyte break several critical limitations of the traditional “liquid phase”-based Li−S batteries, offering a facile and promising way to develop long-life and high-safety Li−S batteries.