Facile synthesis of porous Li2S@C composites as cathode materials for lithium–sulfur batteries

Lithium sulfide (Li 2 S) is regarded as a promising cathode material for lithium–sulfur (Li–S) batteries in terms of its high theoretical specific capacity of 1166 mAh g −1 and good compatibility with lithium metal-free anodes. However, Li 2 S suffers from poor cycling stability and rate capability resulted from the serious shuttle effect of lithium polysulfides and its low electronic and ionic conductivity . Here, we present a facile ball milling combined with carbon coating method to synthesize porous carbon-coated Li 2 S (Li 2 S@C) composites with a high Li 2 S content by using polystyrene (PS) as a carbon precursor. The Li 2 S@C composites show a high reversible specific capacity of 676 mAh g −1 (equal to 971 mAh g −1 sulfur) after 3 cycles at the current density of 0.1 A g −1 , superior cycling stability with an average decay rate of 0.18% per cycle over 200 cycles, and improved rate capability of 416 mAh g −1 at the current density of 1.0 A g −1 . The enhanced electrochemical properties of Li 2 S can be attributed to the porosity and core–shell structure of the Li 2 S@C composites, which increased the electronic and ionic conductivity of Li 2 S and alleviated the shuttle effect of intermediate lithium polysulfides in the discharge/charge process.