Rationally design of 2D branched Ni(OH)2/MnO2 hybrid hierarchical architecture on Ni foam for high performance supercapacitors

Abstract

As electrode materials for supercapacitors, nanostructured hybrids always show better performance compared to corresponding single material. In this work, Ni(OH)2 flakes/MnO2 nanosheets hybrid hierarchical architecture (Ni(OH)2/MnO2 HHA) was constructed on Ni foam (NF) through a two-step hydrothermal reaction. Interestingly, MnO2 nanosheets are vertically grown on the both sides of Ni(OH)2 flakes, forming a highly porous structure with large specific surface area and amounts of diffusion channels. As a binder-free electrode for supercapacitors, Ni(OH)2/MnO2 HHA/NF exhibits a high specific capacity of 253.6 mAh g−1 at 2 A g−1, which is much higher than the individual Ni(OH)2 and MnO2. The excellent electrochemical performance can be attributed to the highly porous architecture, two-dimensional (2D) feature and synergistic effect between Ni(OH)2 and MnO2. The asymmetric hybrid supercapacitor was assembled using Ni(OH)2/MnO2 HHA/NF (24 h) as positive electrode and activated carbon (AC) as negative electrode in 3 M KOH. The hybrid supercapacitor cell can be cycled in the voltage window of 0–1.9 V and exhibits a maximum specific energy of 29.9 Wh kg−1 at 1900 W kg−1. The results indicate that the Ni(OH)2/MnO2 HHA/NF electrode shows great potential in design of high-performance energy storage devices. The construction of this 2D branched hierarchical architecture provides an effective method to obtain excellent electrode materials for energy storage.