Flower-like Highly Open-Structured Binder-Free Zn-Co-Oxide Nanosheet for High-Performance Supercapacitor Electrodes

Abstract

Scientific research is being compelled to develop highly efficient and cost-effective energy-storing devices such as supercapacitors (SCs). The practical use of SC devices is hindered by their low energy density and poor rate capability due to the binding agents in fabricating electrodes. Herein, we proposed flower-like highly open-structured binder-free ZnCo2O4 micro-flowers composed of nanosheets supported in nickel foam (ZnCoO@NF) with improved rate capability up to 91.8% when current varied from 2 to 20 A·g−1. The ZnCoO@NF electrode exhibited a superior specific capacitance of 1132 F·g−1 at 2 A·g−1 and revealed 99% cycling stability after 7000 cycles at a high current density of 20 A·g−1. The improved performance of the ZnCoO@NF electrode is attributed to the highly stable structure of the micro/nano-multiscale architecture, which provides both the high conduction of electrons and fast ionic transportation paths simultaneously.

Electrode Materials, Structural Design, and Storage Mechanisms in Hybrid Supercapacitors

“…Generally, multi-metal compounds can be divided into multi-metal oxides, sulfides, and hydroxides. Multi-metal oxides, such as NiCo 2 O 4 [ 121 , 122 , 123 ], ZnCo 2 O 4 [ 124 , 125 , 126 , 127 ], MnMoO 4 [ 128 , 129 , 130 ], and CoMoO 4 [ 131 , 132 , 133 , 134 ], have been widely explored for energy conversion and storage. Among these multi-metal oxides, the NiCo 2 O 4 nanomaterials have attracted increasing attention due to their merits of higher electrical conductivity, and higher electrochemical activity, which would offer richer redox reactions, including contributions from both Ni 2+ /Ni 3+ and Co 3+ /Co 4+ redox couples in the materials [ 121 , 122 , 123 ].…”