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.