Dual-Interface Regulation of Cyclic Thioether Electrolyte Additives for Enhancing the Cycling Stability of...

The development of high-energy-density lithium metal batteries (LMBs) using carbonate electrolytes is severely hindered by unstable interfacial chemistry, leading to uncontrolled lithium dendrite growth and rapid performance degradation. Given that the electrode/electrolyte interface property is highly dependent on the interface interactions, this work introduces 1,4-dithiane (1,4-DH), an environmentally benign cyclic thioether, as a multifunctional additive for stabilizing electrode-electrolyte interfaces in conventional carbonate electrolytes without fluorinated solvents. The 1,4-DH additive exhibits preferentially adsorption on both Li metal anodes and NCM811 (LiNi_0.8Co_0.1Mn_0.1O₂) cathodes, displacing solvent molecules from electrode surfaces to suppress solvent decomposition while driving localized PF₆ ^- enrichment at the electrode interfaces via a robust binding interaction. The additive undergoes preferential self-decomposition during cycling to form sulfur-rich SEI (solid-electrolyte-interphase)/CEI (cathode electrolyte interphase), promoting synergistic decomposition of PF₆ ^- simultaneously to form inorganic-dominated interphases (LiF, Li₂S). As a result, the lithium iron phosphate full cell achieves 87.54% capacity retention and 99.99% average coulombic efficiency over 3000 cycles. Crucially, 1,4-DH stabilizes NCM811 cathodes against cracking, enabling prolonged cycle stability at 4.8 V. The additive further demonstrates exceptional adaptability under extreme conditions (-10 and 60 °C) and practical pouch cell configurations. This work provides a practical strategy for durable LMBs via non-fluorinated electrolyte engineering.