Morphology engineering of NiCo2S4 for supercapacitor applications: A study on spherical and cubic structures

Abstract

This study investigates the effect of solvent composition on the morphology and electrochemical performance of NiCo₂S₄ (NCS) grown on nickel foam via a hydrothermal method. Different morphologies were prepared to explore how shape and structure affect electrochemical properties such as surface area and ion transport. By tailoring the morphology, it is possible to enhance the material's charge storage capacity for supercapacitor applications. By varying the water-to-ethylene glycol (EG) ratio, two distinct morphologies were obtained. A higher ratio (2:1) formed aggregated spherical particles (S-NCS), while a lower ratio (1:2) produced plate-like cubic shapes (C-NCS). A comprehensive XRD, FESEM, EDS, and elemental mapping techniques confirmed the successful synthesis of these morphologies. Structural analyses revealed that solvent ratio influenced crystallinity and particle size, with C-NCS exhibiting smaller crystallites and lower microstrain. Electrochemical tests revealed that S-NCS outperformed C-NCS, delivering a higher specific capacity (1112C/g vs. 898C/g at 1 A/g) and better cycling stability (86.4 % vs. 81.2 % retention after 5000 cycles at 8 A/g). In comparison, the asymmetric supercapacitor device of S-NCS//AC exhibited enhanced performance, achieving a maximum energy density of 68.8 Wh/kg at a power density of 400 W/kg, and maintaining a notable energy density of 22.2 Wh/kg even at a high-power density of 16 kW/kg. It also retained 83.1 % of its initial capacity after 5000 cycles at a current rate of 8 A/g. These results demonstrate that controlling NCS morphology through solvent ratio tuning significantly enhances supercapacitor performance.