Li sub(2)S-reduced graphene oxide nanocomposites as cathode material for lithium sulfur batteries

A lithium sulfide-reduced graphene oxide nanocomposite (Li sub(2)S-rGO) was synthesized and evaluated as the cathode material and Li source for the assembly of Li-S batteries. The composite, with a unique 3-D pocket structure, was synthesized by a combination of facile solution chemistry and thermal treatment. The as-prepared Li sub(2)S-rGO nanocomposites were characterized by X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy, which showed 20-40 nm Li sub(2)S particles homogeneously dispersed between reduced graphene oxide sheets. Li sub(2)S contents as high as ~66% could be obtained. When used with an electrolyte containing LiNO sub(3) and polysulfide, the Li sub(2)S-rGO nanocomposites exhibited a high initial capacity of 982 mAh g super(-1) Li sub(2)S. However, there was noticeable capacity fade in subsequent cycles, probably due to polysulfide dissolution and the shuttle mechanism, but a capacity of 315 mAh g super(-1) could still be obtained after 100 cycles, with 90-95% coulomb efficiency. The effect of polysulfide additive in the electrolyte on the activation of Li sub(2)S in the first delithiation step was discussed.