Sulphur–TiO2 yolk–shell nanoarchitecture with internal void space for long-cycle lithium–sulphur batteries

Sulphur is an attractive cathode material with a high specific capacity of 1,673 mAh g−1, but its rapid capacity decay owing to polysulphide dissolution presents a significant technical challenge. Despite much efforts in encapsulating sulphur particles with conducting materials to limit polysulphide dissolution, relatively little emphasis has been placed on dealing with the volumetric expansion of sulphur during lithiation, which will lead to cracking and fracture of the protective shell. Here, we demonstrate the design of a sulphur–TiO2 yolk–shell nanoarchitecture with internal void space to accommodate the volume expansion of sulphur, resulting in an intact TiO2 shell to minimize polysulphide dissolution. An initial specific capacity of 1,030 mAh g−1 at 0.5 C and Coulombic efficiency of 98.4% over 1,000 cycles are achieved. Most importantly, the capacity decay after 1,000 cycles is as small as 0.033% per cycle, which represents the best performance for long-cycle lithium–sulphur batteries so far. The practical performance of lithium–sulphur batteries is lower than expected because of polysulphide dissolution into the electrolyte over time. Sehet al. show that a yolk–shell nanoarchitecture is able to encapsulate sulphur cathode materials efficiently and thus allows over 1,000 charge/discharge cycles.