Understanding the Effects of the Low-Concentration Electrolyte on the Performance of High-Energy-Density Li-S Batteries.

High-energy-density Li-S batteries have been impeded by low power rate and low sulfur utilization of high-sulfur-loading cathode and unstable Li metal anode. Herein, a new method protocol was proposed to separately investigate the effects of low-concentration electrolytes on the cathode and the anode for Li-S batteries. It was found that 0.5 M LiTFSI showed better cycling stability than the standard concentration of 1.0 M LiTFSI under the condition of high sulfur loading due to its better wettability toward the electrode. In addition, the low-concentration electrolyte could improve the stability of the Li-electrolyte interface, which was attributable to a higher content of the organic component in the solid electrolyte interface (SEI), owing to the participation of more solvent in the buildup of the SEI. The flexible and elastic organic components could be more capable of accommodating the volume changes in the Li metal anode. Consequently, the low-concentration electrolyte could be more suitable for high-energy-density Li-S batteries. We anticipate this research could provide some inspirations for the development of high-energy-density and low-cost Li-S batteries.