Hierarchical Ni–Co–Mn hydroxide hollow architectures as high-performance electrodes for electrochemical energy storage

Abstract

In this study, hierarchical Ni–Co–Mn hydroxide hollow architectures were successfully achieved via an etching process. We first performed the synthesis of NiCoMn-glycerate solid spheres via a solvothermal route, and then NiCoMn-glycerate as the template was etched to convert into hierarchical Ni–Co–Mn hydroxide hollow architectures in the mixed solvents of water and 1-methyl-2-pyrrolidone. Hollow architectures and high surface area enabled Ni–Co–Mn hydroxide to manifest a specific capacitance of 1626 F g⁻¹ at 3.0 A g⁻¹, and it remained as large as 1380 F g⁻¹ even at 3.0 A g⁻¹. The Ni–Co–Mn hydroxide electrodes also displayed notable cycle performance with a decline of 1.6% over 5000 cycles at 12 A g⁻¹. Moreover, an asymmetric supercapacitor assembled with this electrode exhibited an energy density of 44.4 W h kg⁻¹ at 1650 W kg⁻¹ and 28.5 W h kg⁻¹ at 12 374 W kg⁻¹. These attractive results demonstrate that hierarchical Ni–Co–Mn hydroxide hollow architectures have broad application prospects in supercapacitors.