Enhanced Li-S Battery Performance Boosted by a Large Surface Area Mesoporous Alumina-Based Interlayer

Owing to high theoretical energy density (2600 W h kg-1), a lithium-sulfur (Li-S) battery is considered as one of the most promising next-generation energy storage systems. The "shuttle effect" of soluble polysulfides brings a series of negative problems and seriously hinders its practical application. In this work, a mesoporous alumina (MA) with a large surface area (598 m2 g-1) was combined with graphene (G) to construct a functional interlayer for separator coating in a Li-S battery to suppress the "shuttle effect". As demonstrated by DFT calculation and experimental investigation, the mesoporous structure and the large surface area of MA are beneficial to provide abundant exposed adsorption sites for polysulfides capture and meanwhile facilitate the migration of polysulfides to the conductive substrate surface for the electrochemical reaction conversion. The strong interaction between polysulfides and MA can reduce energy barriers of electrochemical polysulfide intermediate conversions, leading to enhanced sulfur redox reaction kinetics. The MA@G interlayer enables outstanding Li-S battery performance including large initial discharge capacity (1414 mA h g-1 at 0.5 C), good cycling stability (808 mA h g-1 at 0.5 C after 100 cycles), and rate performance (initial discharge capacity 1056 and 636 mA h g-1 after 300 cycles at 2 C). This work provides guidance for future design of functional separators for high-performance Li-S batteries.