Use of Tween Polymer To Enhance the Compatibility of the Li/Electrolyte Interface for the High-Performance and High-Safety Quasi-Solid-State Lithium–Sulfur Battery

Lithium metal batteries have attracted increasing attention recently due to their particular advantages in energy density. However, as for their practical application, the development of solid-state lithium metal batteries is restricted because of the poor Li/electrolyte interface, low Li-ion conductivity, and irregular growth of Li dendrites. To address the above issues, we herein report a high Li-ion conductivity and compatible polymeric interfacial layer by grafting tween-20 on active lithium metal. Sequential oxyethylene groups in tween-grafted Li (TG-Li) improve the ion conductivity and the compatibility of the Li/electrolyte interface, which enables low overpotentials and stable performance over 1000 cycles. Consequently, the poly(ethylene oxide)-based solid-state lithium–sulfur battery with TG-Li exhibits a high reversible capacity of 1051.2 mA h g–1 at 0.2 C (1 C = 1675 mA h g–1) and excellent stability for 500 cycles at 2 C. The decreasing concentration of the sulfur atom with increasing Ar+ sputtering depth indicates that the polymer interfacial layer works well in suppressing polysulfide reduction to Li2S/Li2S2 on the metallic Li surface even after long-term cycling.