Highly Reversible Lithium-Metal Anode and Lithium-Sulfur Batteries Enabled by an Intrinsic Safe Electrolyte.

Rechargeable lithium-metal batteries have gained significant attention as potential candidates of energy storage systems; however, severe safety issues including flammable electrolyte and dendritic lithium formation hinder their further practical application. In this work, we develop a novel intrinsic flame-retardant electrolyte, which enables a stable and dendrite-free cycling with lithium plating/stripping Coulombic efficiency of up to 99.1% over 500 cycles. Raman spectra indicate that no free molecular solvent exists, and X-ray photoelectron spectroscopy reveals the LiF-rich interphase on the Li-metal anode. When coupled with sulfurized pyrolyzed poly(acrylonitrile) cathode, it shows a benign electrochemical reversibility with the areal capacity of up to 3.41 mAh cm-2 after 70 cycles. To further check its compatibility with sulfur cathode, a higher sulfur content (51.6%) is examined with the areal capacity of 3.92 mAh cm-2 and sulfur utilization of 81.7%. This work provides an alternative for safe and high-performance Li-S batteries via a novel electrolyte strategy.