Facile one-pot synthesis of NiCo2O4 hollow spheres with controllable number of shells for high-performance supercapacitors

In this work, single- and double-shelled NiCo2O4 hollow spheres have been synthesized in situ by a one-pot solvothermal method assisted by xylose, followed by heat treatment. Employed as supercapacitor electrode materials, the double-shelled NiCo2O4 hollow spheres exhibit a remarkable specific capacitance (1,204.4 F center dot g(-1) at a current density of 2.0 A center dot g(-1)) and excellent cycling stability (103.6% retention after 10,000 cycles at a current density of 10 A center dot g(-1)). Such outstanding electrochemical performance can be attributed to their unique internal morphology, which provides a higher surface area with a larger number of active sites available to interact with the electrolyte. The versatility of this method was demonstrated by applying it to other binary metal oxide materials, such as ZnCo2O4, ZnMn2O4, and CoMn2O4. The present study thus illustrates a simple and general strategy for the preparation of binary transition metal oxide hollow spheres with a controllable number of shells. This approach shows great promise for the development of next-generation high-performance electrochemical materials.