A Simple Synthesis of Two-Dimensional Ultrathin Nickel Cobaltite Nanosheets for Electrochemical Lithium Storage

We report a simple microwave-assisted method to fabricate high-quality two-dimensional (2D) ultrathin NiCo₂O₄ nanosheets with a geometrically graphene-like architecture. The unique large-area nanostructures represent an ultrahigh surface atomic ratio with almost all active elements exposed outside for surface-dependent electrochemical reaction processes. Experimental results reveal that the as-synthesized ultrathin NiCo₂O₄ nanosheets show excellent electrochemical performances for lithium storage application. The ultrathin NiCo₂O₄ nanosheets could deliver a high first discharge capacity (1287.1 mAh g^-1) with initial Coulombic efficiency of 80.0% at 200 mA g^-1 current density. The reversible lithium storage capacity still retains at 804.8 mAh g^-1 in the 100th cycle, suggesting a good cycling stability. The excellent electrochemical properties of the as-synthesized NiCo₂O₄ nanosheets could be ascribed to the unique ultrathin 2D architecture, which could offer large exposed active surface with more lithium-insertion channels and significantly reduce lithium ion diffusion distance. The cost-efficient synthesis and excellent lithium storage properties make the 2D NiCo₂O₄ nanosheets as a promising anode material for high-performance lithium ion batteries.