Diethyl Sulfide as a Multifunctional Electrolyte Additive for Enhancing Electrochemical Performance of Lithium Metal Batteries

ABSTRACT With the increasing demand for energy storage devices with higher energy density, lithium metal anode (LMA) has emerged as promising candidate due to ultra‐high theoretical specific capacity (3860 mAh g −1 ) and the lowest reduction potential (‐3.04 V vs. S.H.E.). However, the practical application of LMA is still restricted by notorious active lithium loss and lithium dendrite growth, which cause low Coulombic efficiency, poor cycling life, and even potential safety hazards. In this study, a multifunctional diethyl sulfide electrolyte additive is proposed to synergistically construct a stable Li 2 S‐rich solid electrolyte interphase (SEI) and Li 2 S/Li 2 SO 4 /Li 2 SO 3 ‐rich cathode electrolyte interphases (CEI), which could accelerate Li ions (Li + ) transport kinetics and enhance the interfacial stability during long‐term cycling. Moreover, the sulfur‐rich composite in electrolyte interface could reduce the energy barrier for Li + desolvation and thereby enhance interface dynamics. Based on these merits, the introduction of 2.0 vol.% diethyl sulfide into a carbonate electrolyte (without FEC) enables the lithium anode to achieve a 7‐fold enhancement in long‐term cycling performance. More impressively, the Li||LiFePO 4 (LFP) pouch cell with the modified electrolyte achieves an outstanding capacity retention of 98.75% after 200 cycles at 0.1 C. The multifunctional diethyl sulfide additive paves the way for high‐performance LMBs for practical applications.