Improved lithium and sodium ion storage properties of WS2 anode with three-layer shell structure

A three-layer shell structured tungsten disulfide-based material for high capacity anode is prepared by a hydrothermal method. The three layers consist of a stable porous carbon shell (PCS), a tungsten disulfide nanosheet (WS2) and a highly conductive nitrogen-doped graphene (NG). While the nanostructured WS2 and NG ensured the fast lithium/sodium ions (Li+/Na+) insertion/extraction, the stable PCS shell provides structural stability during cycling, resulted in the improved rate capability and long cycle life of the PCS/WS2/NG anode material. For lithium-ion batteries (LIBs), the capacity of PCS/WS2/NG anode is 324.7 mAh g−1 after 510 cycles at a high current density of 2 A g−1. The discharge capacities of PCS/WS2/NG, PCS/WS2, WS2 and PCS anodes are 272.9, 105.1, 8.1 and 6.7 mAh g−1, respectively, at a high current density of 4 A g−1. When the current density rebound to 0.1 A g−1, their capacity retentions are 57.8%, 38.3%, 17.6% and 26.4%, respectively. The capacity retention of PCS/WS2/NG anode is 69.6%, higher than that of the pristine WS2 anode. For sodium-ion batteries (SIBs), PCS/WS2/NG anode exhibits a specific capacity of 205.0 mAh g−1 after the 900th cycle at the current density of 0.5 A g−1. The excellent electrochemical performance of the three-layer shell structured PCS/WS2/NG nanomaterial is a promising anode for high performance LIBs and SIBs.