Hierarchically structured MnO2nanowires supported on hollow Ni dendrites for high-performance supercapacitors

Abstract

We report a hierarchical Ni@MnO₂ structure consisting of MnO₂ nanowires supported on hollow Ni dendrites for high-performance supercapacitors. The Ni@MnO₂ structure, which was prepared via a facile electrodeposition method, is highly porous and appears like a forest of pine trees grown vertically on a substrate. At a MnO₂ mass loading of 0.35 mg cm⁻², the Ni@MnO₂ electrode demonstrated a specific capacitance of 1125 F g⁻¹ that is close to the theoretical value. In addition, a remarkable high-rate performance (766 F g⁻¹ at a discharge current density of 100 A g⁻¹) was achieved. Electrochemical tests in a two-electrode configuration for the Ni@MnO₂ structure with a high MnO₂ loading of 3.6 mg cm⁻² showed a low equivalent series resistance (ESR) of 1 Ω and a high specific power of 72 kW kg⁻¹. This superior performance can be attributed to the highly porous and hierarchical structure of Ni@MnO₂ that favors rapid diffusion of an electrolyte, highly conductive pathway for electron transport, and efficient material utilization.