Li₂S-reduced graphene oxide nanocomposites as cathode material for lithium sulfur batteries

A lithium sulfide-reduced graphene oxide nanocomposite (Li ₂S-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 Li₂S-rGO nanocomposites were characterized by X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy, which showed 20-40 nm Li₂S particles homogeneously dispersed between reduced graphene oxide sheets. Li₂S contents as high as ∼66% could be obtained. When used with an electrolyte containing LiNO₃ and polysulfide, the Li₂S-rGO nanocomposites exhibited a high initial capacity of 982 mAh g^-1 Li₂S. 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^-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 Li₂S in the first delithiation step was discussed.