Durable Carbon-Coated Li2S Core–Shell Spheres for High Performance Lithium/Sulfur Cells

Lithium sulfide (Li2S) is an attractive cathode material with a high theoretical specific capacity (1166 mAh g–1). However, the poor cycle life and rate capability have remained significant challenges, preventing its practical application. Here, Li2S spheres with size control have been synthesized for the first time, and a CVD method for converting them into stable carbon-coated Li2S core–shell (Li2S@C) particles has been successfully employed. These Li2S@C particles with protective and conductive carbon shells show promising specific capacities and cycling performance with a high initial discharge capacity of 972 mAh g–1 Li2S (1394 mAh g–1 S) at the 0.2C rate. Even with no added carbon, a very high Li2S content (88 wt % Li2S) electrode composed of 98 wt % 1 μm Li2S@C spheres and 2 wt % binder shows rather stable cycling performance, and little morphology change after 400 cycles at the 0.5C rate.