Rational design of titanium oxide-coated dual Core–Shell sulfur nanocomposite cathode for highly stable lithium–sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) have been considered as one of the promising next-generation energy storage systems due to their high specific capacity and energy density compared to intercalated metal oxide-based lithium-ion batteries (LIBs). However, the bottleneck that prevents commercialization of LSBs is how to tackle the polysulfide shuttle (PSS) effect, including low conductivity and dramatic volume change of the cathode material, which lead to rapid capacity fading and poor cycle life. In this paper, a new LSB cathode material with a nano-sized structure of sulfur encapsulated TiO2-coated dual core–shell hollow carbon sphere (S@HCS@TiO2) has been developed. The inner hollow carbon sphere (HCS) with a foamy carbon shell provides space for volumetric expansion, good electronic and ionic conductivity; while the outside TiO2 shell is not only a physical barrier to polysulfide species, but also possesses a strong chemical interaction with polysulfides. As a result, the obtained Li–S cells with S@HCS@TiO2 cathode material display a high initial capacity (751.6 mA h g−1) and low capacity decay (0.039% per cycle) for 800 cycles at a high current density (1C).