Synthesis of 1D nanorod and 2D nanoflake mixed structures of nickel cobaltite: an efficient diffusion-controlled electrode material for asymmetric supercapacitor application

The intercalation pseudocapacitance mechanism holds the potential to significantly narrow the gap between supercapacitors and lithium-ion batteries, particularly in terms of energy density and power density properties. Herein, 1D nanorod and 2D nanoflake mixed structures of nickel cobaltite (NiCo₂O₄) were prepared for asymmetric supercapacitor application. For comparison, the NiO and Co₃O₄ materials were also prepared, and examined their supercapacitor properties. The NiCo₂O₄ store charges through the diffusion-controlled process and delivers the specific capacity of 347 C g⁻¹ (694 F g⁻¹) at 1 A g⁻¹ and it withstands 96% of initial capacity after 5000 cycles at a current density of 10 A g⁻¹. Furthermore, the asymmetric supercapacitor device (NiCo₂O₄//AC) exhibits the specific capacity of 141 C g⁻¹ (88 F g⁻¹) at 1 A g⁻¹, with an excellent energy and power density of 31.3 Wh kg⁻¹ and 800 W kg⁻¹ respectively. The device retained 86% of its initial capacity after 5000 GCD cycles at 10 A g⁻¹. Therefore, the 1D/2D mixed morphologies with diffusion-controlled charge storage process are guaranteed to achieve superior electrochemical performance.