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

Abstract

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.