3D MoS ₂ -graphene microspheres consisting of multiple nanospheres with superior sodium ion storage properties

A novel anode material for sodium-ion batteries consisting of 3D graphene microspheres divided into several tens of uniform nanospheres coated with few-layered MoS ₂ by a one-pot spray pyrolysis process is prepared. The first discharge/charge capacities of the composite microspheres are 797 and 573 mA h g ^-1 at a current density of 0.2 A g ^-1 . The 600th discharge capacity of the composite microspheres at a current density of 1.5 A g ^-1 is 322 mA h g ^-1 . The Coulombic efficiency during the 600 cycles is as high as 99.98%. The outstanding Na ion storage properties of the 3D MoS ₂ -graphene composite microspheres may be attributed to the reduced stacking of the MoS ₂ layers and to the 3D structure of the porous graphene microspheres. The reduced stacking of the MoS ₂ layers relaxes the strain and lowers the barrier for Na ⁺ insertion. The empty nanospheres of the graphene offer voids for volume expansion and pathways for fast electron transfer during repeated cycling.