Conversion/reconversion-driven heterostructure electrode for enhanced electrochemical performances in lithium-ion/sodium-ion batteries and supercapattery

Advanced high-performance materials are pivotal for enhancing the performance of energy storage technologies like lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and supercapattery. In the present study, a novel NiO-CoS heterostructure nanostrip was synthesized using a cost-effective hydrothermal approach and carried out an in-depth investigation of their electrochemical behaviour. Diverse characterization techniques were applied to explore the structural, morphological, and compositional aspects of the material. To assess the energy storage potential of the NiO-CoS heterostructure electrode in lithium-ion and sodium-ion systems, electrochemical methods such as cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) were systematically employed. Notably, the NiO-CoS anode achieved a high specific capacity of 988 mAh g⁻¹ when tested in a LIB half-cell at a 0.1C current rate. Consequently, a full-cell LIB achieved an acceptable high capacity of 150 mAh g⁻¹ and successfully powered commercial LED bulbs for long hours continuously, demonstrating its potential in real-time application. For the SIB, the heterostructure electrode demonstrated remarkable cycling durability and near-ideal coulombic efficiency, with the SIB half-cell delivering 400 mAh g⁻¹ of specific capacity at 0.1C-rate. An aqueous supercapattery device (NiO-CoS|1 M KOH|rGO) exhibited exceptional cycling stability for over 10,000 cycles while attaining impressive energy and power densities of 134 Wh kg⁻¹ and 1200 W kg⁻¹, respectively. The ex-situ XRD results obtained from postmortem analysis of the NiO-CoS electrode at two charged states (fully charged and fully discharged) validated the conversion/reconversion reactions in the lithium electrolyte leading to enhanced charge storage. Dunn's analysis across all three systems indicated that the charge storage is controlled by both capacitive and diffusion-driven contributions.