Electrochemical properties of tungsten sulfide-carbon composite microspheres prepared by spray pyrolysis

Tungsten sulfide (WS₂)-carbon composite powders with superior electrochemical properties are prepared by a two-step process.WO ₃-carbon composite powders were first prepared by conventional spray pyrolysis, and they were then sulfidated to form WS₂-carbon powders. Bare WS₂ powders are also prepared by sulfidation of bareWO ₃ powders obtained by spray pyrolysis. Stacked graphitic layers could not be found in the bare WS₂ and WS₂-carbon composite powders. The amorphous bare WS₂ and WS₂-carbon composite powders have Brunauer-Emmett-Teller (BET) surface areas of 2.8 and 4 m2 g ^-1, respectively. The initial discharge and charge capacities of the WS₂-carbon composite powders at a current density of 100 mA g ^-1 are 1055 and 714 mA h g^-1, respectively, and the corresponding initial Coulombic efficiency is 68%. On the other hand, the initial discharge and charge capacities of the bare WS₂ powders are 514 and 346 mA h g^-1, respectively. The discharge capacities of the WS₂-carbon composite powders for the 2nd and 50th cycles are 716 and 555 mA h g^-1, respectively, and the corresponding capacity retention measured after first cycle is 78%.