Sea Urchin-Like NiO-CoO Heterostructure as High-Energy Supercapattery Electrode: Laboratory Prototype to Field Application of Pouch-type Device

Abstract

Transition metal-oxides are being explored in the energy storage applications nowadays, serving as electrodes because of their desirable redox features. In this study, sea urchin-like nickel oxide-cobalt oxide (NiO-CoO) heterostructure was generated using a hydrothermal method and examined as supercapattery electrode. The crystallinity and morphological features of the synthesized heterostructure were analyzed using various techniques like powder X-ray Diffraction (XRD), scanning electron microscope (SEM), high-resolution-transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS), etc. The electrochemical activity of the sea urchin-like NiO-CoO heterostructure electrode toward supercapattery was tested in three diverse electrolytes consisting of KOH, NaOH, and LiOH. As a result, the heterostructure electrode exhibited excellent charge-storage features in three electrode configurations in the alkali electrolytes. Hence, the supercapattery practical devices were fabricated both in coin-type and pouch-type devices. The aqueous coin-type supercapattery device demonstrated an exceptionally high specific energy of 340 W h kg^–1 with a specific power of 295 W kg^–1, showing an excellent cycling stability over 10,000 cycles, whereas the pouch-type device attained a specific energy of 140 W h kg^–1 coupled with a specific power of 320 W kg^–1. Power Law and Dunn’s analyses confirmed the simultaneous contribution of the diffusive and the capacitive charge storage kinetics in the NiO-CoO heterostructure electrode. In the non-aqueous system, there seems to be Li⁺ ion intercalation leading to high specific energy at passable specific power. The fabricated coin-type and the pouch-type supercapattery devices were demonstrated in the field applications such as glowing LED and functional stopwatch independently and together.