Citrate-assisted growth of NiCo₂O₄nanosheets 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 NiCo₂O₄nanosheets 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 NiCo₂O₄nanosheets on rGO without damaging the morphology. The interconnected NiCo₂O₄nanosheets 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/NiCo₂O₄nanocomposite demonstrates high reversible capacities of 954.3 and 656.5 mAh g^-1over 50 cycles at current densities of 200 and 500 mA g^-1respectively, and remarkable capacity retention at increased current densities. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA.