Optimization of metal–organic framework derived transition metal hydroxide hierarchical arrays for high performance hybrid supercapacitors and alkaline Zn-ion batteries

Abstract

The rational microstructure design of transition metal compound arrays using metal–organic frameworks (MOFs) as intermediates has been proved effective but is very challenging to achieve high electrical energy storage capacity. Herein, we report the synthesis of a Setaria viridis-like multi-component core–shell nanostructure, Co(OH)₂@NiCo-layered double hydroxide nanowire arrays (A-Co(OH)₂@NiCo-LDH), directly on carbon fiber cloths. The Setaria viridis-like unique nanostructure provides a large surface area, rich redox active sites, and stable microstructure for electrical energy storage. Consequently, the as-prepared A-Co(OH)₂@NiCo-LDH hierarchical array exhibits a high specific capacity of 285.9 mAh g⁻¹ at 0.5 A g⁻¹. Moreover, the electrode exhibits an excellent capacity retention of 72.9% in the range from 0.5 A g⁻¹ to 50 A g⁻¹. A hybrid supercapacitor (HSC) and an alkaline Zn-ion battery (AZIB) based on the A-Co(OH)₂@NiCo-LDH cathode were assembled for practical application, which delivered outstanding energy densities of 40.6 Wh kg⁻¹ (at a power density of 1.78 kW kg⁻¹, based on the mass of the active materials of both electrodes) and 489.6 Wh kg⁻¹ (at a power density of 0.38 kW kg⁻¹, based on the mass of the A-Co(OH)₂@NiCo-LDH cathode) and long lifetimes of 10 000 and 1000 GCD cycles, respectively. The excellent electrochemical performance of A-Co(OH)₂@NiCo-LDH proves its great promise as an electrode material for fabricating advanced energy storage devices for industrial applications.