Rapid synthesis of hexagonal NiCo ₂ O ₄ nanostructures for high-performance asymmetric supercapacitors

A facile, robust and cost-effective co-precipitation method was employed to develop NiCo ₂ O ₄ (NCO) hexagonal nanostructures for effective positive electrode in asymmetric supercapacitors. With an inclusion of alkali ions in growth solution, the nickel and cobalt ions were homogeneously precipitated and nucleated in the form of hexagonal-shaped NCO with porous properties. Electrochemical performance of NCO was probed in aqueous electrolyte of 2 M KOH. NCO nanostructures exhibited good electrochemical performance with a maximum specific capacitance of 1525 (±5) F g ⁻¹ at a current density of 1 A g ⁻¹ . Owing to good electrochemical properties of the material, an asymmetric supercapacitor (ASC) was assembled in 2 M KOH electrolyte. Specific energy and power densities of the ASC were obtained to be 24.5 Wh kg ⁻¹ and 175 W kg ⁻¹ , respectively at 0.25 A g ⁻¹ . Furthermore, the parallel-connected two red colored light-emitting diodes (1.8 V @ current 20 mA) were lit for 4 min. In addition, ASC device can also drive the electrical motor fan up to 50 s, showing the potential application of the electrode material. This high performance in both three electrode and two electrode systems is related to rich redox reaction, well-defined morphology with mesopores and nano-architecture electrode material.