Top-down fabrication of hierarchical nanocubes on nanosheets composite for high-rate lithium storage

A top-down method was developed to synthesize hierarchical composites consisting of NiCo2O4 nanocubes and graphene nanosheets through the electrostatic interaction of negatively charged graphene oxide nanosheets and positively charged NiCo2O4 spheres. Employed as anode materials for lithium-ion batteries, the hierarchical composites exhibit remarkably high electrochemical performance, including large reversible capacity, superior rate capability, and excellent cycling performance. Large reversible capacities of 1024 and 648 mA h g-1 are maintained at a current density of 500 and 3000 mA g-1, respectively, for over 200 cycles. The excellent electrochemical performance of the composite is attributed to the synergistic effect of the hierarchical structure, the well dispersed NiCo2O4 nanocubes and the uniform graphene coating. This work provides an effective and promising strategy for the rational structural design of the metal oxide electrode material.