Hydrothermal synthesis of urchin-like NiCo2O4/stereotaxically constructed graphene microspheres for ultrahigh-rate lithium and sodium storage

Abstract

Urchin-like NiCo2O4/stereotaxically constructed graphene (t-SCG) microspheres are synthesized via a hydrothermal method. NiCo2O4/t-SCG microspheres display hierarchical porous structures with large specific surface area (138.81 m2 g−1). When evaluated as anode materials for Li-ion battery, NiCo2O4/t-SCG electrode shows a high reversible specific discharge capacity of 498.5 mA h g−1 even in the 200th cycle at a current density of 0.5 A g−1. The performance of the sample as anode materials for Na-ion battery is also evaluated. NiCo2O4/t-SCG electrode can deliver a high initial specific discharge capacity of 818.9 mA h g−1, stable cycling with more than 314 mA h g−1 at 0.1 A g−1 in the 50th cycle. Compared with bare NiCo2O4 microspheres, NiCo2O4/t-SCG microspheres show much higher capacities and stability for both Li- and Na-ion battery, attributed that t-SCG acts as an efficient 3D conductive network to improve electronic conductivity.