Facile ordered ZnCo2O4@MnO2 nanosheet arrays for superior-performance supercapacitor electrode

Constructing ZnCo2O4 nanosheet arrays (NSAs)@MnO2 nanosheets core-shell nanostructures directly on the current collector (Ni foam) was successfully realized via hydrothermal process and heat treatment. The whole surfaces of uniform ZnCo2O4 NSAs were covered with well-ordered MnO2 nanosheets, which make the whole system have a large specific surface area. At a low current density of 2 mA cm−2, supercapacitor electrode made of ZnCo2O4@MnO2 composite gave rise to a superior specific capacity about 929.2 C g−1. Although at an ultrahigh current density of 40 mA cm−2, it still kept a satisfactory specific capacity about 751.1 C g−1, and retained ∼95.75% of the capacity even after 5000 cycles. Because of the synergistic effect between ZnCo2O4 and MnO2 and the great surface area of the system with the special core-shell structure, ZnCo2O4@MnO2 composite has the excellent rate performance, considerable capacity, and quite good cycle performance, which make it a candidate for a new generation of superior-performance electrochemical supercapacitors.