Metallic phase W0.9Mo0.1S2 for high-performance anode of sodium ion batteries through suppressing the dissolution of polysulfides

Abstract

WS2 with layered graphite-like structure as anode for sodium ion batteries has high specific capacity. However, the poor cycling performance and rate capability of WS2 caused by the low electronic conductivity and structure changes during cycles inhibit its practical application. Herein, metallic phase (1T) WxMo1−xS2 (x = 1, 0.9, 0.8 and 0.6) with high electronic conductivity and expanded interlayer spacing of 0.95 nm was directly prepared via a simple hydrothermal method. Specially, 1T W0.9Mo0.1S2 as anode for sodium ion batteries displays high capacities of 411 mAh g−1 at 0.1 A g−1 after 180 cycles and 262 mAh g−1 at 1 A g−1 after 280 cycles and excellent rate capability (245 mAh g−1 at 5 A g−1). The full cell based on Na3V2(PO4)2O2F/C cathode and 1T W0.9Mo0.1S2 anode also exhibits high capacity and good cycling performance. The irreversible electrochemical reaction of 1T W0.9Mo0.1S2 with Na ions during first few cycles results in the main products of W-Mo alloy and S. The strong adsorption of W-Mo alloy with polysulfides can effectively suppress the dissolution and shuttle effect of polysulfides, which ensures the excellent cycling performance of 1T W0.9Mo0.1S2.