Development of electric vehicle has led ever increasing demand of high energy density lithium ion batteries such as Li-sulfur, and Li-oxygen batteries. In this regard, lithium metal received huge attention as an anode due to the high specific capacity (3,860mAh/g) and the lowest electrochemical potential (-3.04V versus standard hydrogen electrode). However, nature of lithium metal is giving rise to safety concerns including uncontrollable dendrite growth, chemical reaction with organic electrolyte, and volume change while cycling, which also result in poor cycling performance. Due to those reasons, broader use of lithium metal as an anode was hindered in the commercialized field.

Here, we introduce Ethyl Methyl Sulfone (EMS) as a co-solvent in a typical electrolyte system, 1,3-Dioxolane (DOL) and Dimethyl ether (DME) to tackle those challenges. Adding EMS into the DOL/DME shows outstanding performance of suppressing dendrite growth as well as retaining good cycling stability proven by Li|Li symmetric cells and Li|Cu cells respectively. Scanning Electron Microscopy (SEM) showed non-dendritic surface of lithium metal unlike needle-like dendrite surface of control sample (DOL/DME only). Energy Dispersive X-ray Spectroscopy (EDX) also showed well-dispersed fluorine and sulfur elements and XPS analysis was conducted to prove the existence of Solid Electrolyte Interface (SEI) composed of lithium-sulfur-carbon(oxygen) mixed with lithium fluoride. We suggest sulfur in EMS act as crosslinking agents to form robust SEI that holds volume expansion, dendrite growth, and continuous lithium consumption which leads higher C.E. than DOL/DME system. Lastly, lithium metal was paired with sulfur cathode in coin cells to show better cycling performance, which can be further used in Li-S environments.