Citrate-Assisted Growth of NiCo2O4 Nanosheets on Reduced Graphene Oxide for Highly Reversible Lithium Storage

Hybrid nanostructures based on graphene and transition metal oxides hold great promise as high-performance electrode materials for next-generation lithium-ion batteries. In this work, the rational design and fabrication of NiCo2O4 nanosheets supported on reduced graphene oxide (denoted as rGO/NiCo2O4) is presented as a novel anode material for highly efficient and reversible lithium storage. A solution method is applied to grow Ni-Co precursor nanosheets on rGO, in which the addition of trisodium citrate is found crucial to guide the formation of uniform Ni-Co precursor nanosheets. Subsequent thermal treatment results in formation of crystalline NiCo2O4 nanosheets on rGO without damaging the morphology. The interconnected NiCo2O4 nanosheets form hierarchically porous films on both sides of rGO. Such a hybrid nanostructure would effectively promote the charge transport and withstand volume variation upon prolonged charge/discharge cycling. As a result, the rGO/NiCo2O4 nanocomposite demonstrates high reversible capacities of 954.3 and 656.5 mAh g(-1) over 50 cycles at current densities of 200 and 500 mA g(-1) respectively, and remarkable capacity retention at increased current densities.