Morphology-controlled synthesis of a NiCo-carbonate layered double hydroxide as an electrode material for solid-state asymmetric supercapacitors

Abstract

Transition metal carbonate hydroxides are emerging as potential candidates as electrode materials for efficient energy storage systems. Herein, we report the solvothermal synthesis of NiCo-layered double hydroxide carbonate hybrid or NiCo-carbonate layered double hydroxide (NiCo-CH) nanostructures as active electrode materials for energy storage in supercapacitors. The morphology and physicochemical properties of the NiCo-CH nanostructure are tailored by controlling the synthesis parameters. The NiCo-CH nanorods synthesized at 180 °C (NiCo-CH-180) deliver the best performance, i.e., a specific capacitance of 762 F g−1 at 1 A g−1 current density, among the as-synthesized NiCo-CHs. An asymmetric supercapacitor (ASC) device fabricated using NiCo-CH-180 as the positive electrode and activated carbon (AC) as the negative electrode (NiCo-CH-180//AC) exhibits an energy density of 52 W h kg−1 with a power density of 1500 W kg−1 at 2 A g−1 current density. The fabricated ASC retains 76.2% of its capacitance after 5000 charge-discharge cycles, which corroborates its good cycling stability. This work demonstrates an effective strategy to synthesize a well-defined NiCo-CH nanostructure as an electrode material for energy storage applications.