Spinel Nickel Cobaltite Mesostructures\nAssembled from Ultrathin Nanosheets for High-Performance Electrochemical\nEnergy Storage

Abstract

Transition\nmetal oxides (TMOs) are promising electrode materials for advanced\nelectrochemical energy storage (EES) due to their high theoretical\ncapacities, but they usually exhibit quite poor practical performance.\nThere is a pressing need to boost their EES performance by electrode\nengineering directed with a well-defined structure–performance\nrelationship. Herein, we report an efficient approach to improve the\nspecific capacitance and high-rate capability of spinel nickel cobaltite\nby constructing three-dimensional (3D) hierarchical porous mesostructures.\nThe optimal Ni_1.4Co_1.6O₄ mesostructures\nassembled from ultrathin nanosheets exhibit high capacitance (2282\nF g^–1 at 1 A g^–1), excellent\nhigh-rate capability (1234 F g^–1 at 50 A g^–1) and good cycling performance, which are significantly superior\nto the Co₃O₄ mesostructure counterparts, Ni_1.4Co_1.6O₄ mesostructures assembled from\nnanowires, and randomly packed Ni_1.4Co_1.6O₄ nanosheets. The excellent performance is attributed to the\nstable hierarchical porous architecture which enables a large electroactive\narea and synergistically enhanced electrolyte access, solid-state\nion diffusion, and electron transfer. This tactic of constructing\na 3D mesostructured electrode with enhanced charge transport can be\ngeneralized to other TMOs for improving their EES performances.