Fe, Co-codoped layered double hydroxide nanosheet arrays derived from zeolitic imidazolate frameworks for high-performance aqueous hybrid supercapacitors and Zn-Ni batteries

In the past decade, layered double hydroxides (LDHs) have attracted great attention in the field of energy storage owing to their excellent two-dimensional (2D) hydrotalcite-like structure, highly reversible redox kinetics, and adjustable composition. At the same time, nanomaterials constructed by ultrathin nanosheets have enhanced conductivity, rich electrochemical active sites and fast charge transfer channels, showing better electrochemical properties. Herein, we designed three-dimensional (3D) NiFeCo LDH vertical nanosheet arrays (denoted NiFeCo-LDH NA) assembled by the tight interconnection of 2D nanosheets using a Ni-coordinated zeolitic imidazolate framework (Ni-ZIF-L) as a sacrificial template via facile ion exchange and etching reaction processes under hydrothermal conditions. The appropriate doping ratio of iron and cobalt ions is regulated. Electrochemical tests show that the NiFeCo LDH NA-based electrode shows a high specific capacity of 1495C g-1 at 1 A g-1 and has great cycling stability (89% capacitance retention over 10,000 cycles). The assembled hybrid supercapacitor (NiFeCo LDH NA//AC) achieves a fine energy density of 34.4 W h kg-1 at a power density of 935.5 W kg-1 with good cycling stability of over a 96% retention rate (compared with the initial capacitance) and outstanding coulombic efficiency (nearly 99%) after 15,000 cycles. The constructed aqueous Zn-Ni battery (NiFeCo LDH NA//Zn) exhibits a remarkable specific capacity of 272 mA h g-1 at 3 A g-1 with a high energy density of 464.7 W h kg-1 and retains 81% of the initial specific capacity after 2000 cycles at 20 A g-1. This work not only proves that ternary LDHs can be used as good energy storage materials but also provides a new way to prepare nanomaterials with specific morphology.