Vertically Aligned Sulfiphilic Cobalt Disulfide Nanosheets Supported on a Free-Standing Carbon Nanofiber Interlayer for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are considered as a potential candidate for replacing lithium-ion batteries (LIBs), owing to their high theoretical energy density and low cost. However, the practical development of LSBs is considerably impeded, owing to the shuttling effect caused by soluble lithium polysulfide. Herein, we report porous cobalt disulfide (CoS2) nanosheets vertically grown on activated cellulose-derived carbon nanofibers (CoS2/ACCF) as an excellent interlayer for LSBs. The vertically arranged two-dimensional (2D) CoS2 nanosheets maximized the reactive surface area exposed to the electrolyte. In addition, each CoS2 nanosheet has a unique porous and crystalline structure comprising numerous nanograins encapsulated by carbon, which induces excellent electrical conductivity and stability. Benefiting from its novel architecture, CoS2/ACCF provides superior high-rate performance (815 mA h g-1 at 2C) in LSBs. Furthermore, electrochemical impedance spectroscopy studies proved that CoS2/ACCF accelerated the interfacial reaction kinetics through highly exposed active sites on vertical 2D nanosheets, resulting in reversible and stable long-term cycling performance (982 mA h g-1 after 100 cycles at 0.1C and 580 mA h g-1 after 500 cycles at 1C). Therefore, this work suggests a new strategy to design an effective interlayer through a facile and cost-effective method for the commercialization of LSBs.