Facile and scalable synthesis of nanosized core–shell Li2S@C composite for high-performance lithium–sulfur batteries

Abstract

Lithium sulfide (Li₂S) is one of the most promising cathode materials for the next-generation advanced Li-ion batteries because of its high theoretical capacity (1167 mA h g⁻¹) and large energy density. However, Li₂S suffers from poor rate performance and short cycle life due to its insulating nature and polysulfide shuttle during cycling. In this work, we have proposed a facile and scalable strategy for the synthesis of nanosized Li₂S particles via a solution-based method. For further application in Li–S batteries, chemical vapor deposition (CVD) technology is used to successfully deposit a uniform conductive carbon layer on the Li₂S particles to obtain a core–shell structured nanocomposite (nano-Li₂S@C). The average size of the as-prepared nano-Li₂S particles is around 100 nm, and covered by a carbon shell with a thickness of ∼20 nm. These nanoscale Li₂S@C particles guarantee a short diffusion distance of lithium ions and the protective carbon layer allows fast electron transport as well as effectively constraining the migration of the soluble polysulfides. As a result, the core–shell structured nano-Li₂S@C cathodes show outstanding electrochemical performance with a high initial discharge capacity of 1083.5 mA h g⁻¹ at 0.2C and 766.3 mA h g⁻¹ after 200 cycles with a low decay of 0.15% per cycle. The enhanced electrochemical performance is due to the core-shelled architecture with enhanced electrical conductivity and better suppression effect for the polysulfide shuttle.