Shape-controlled synthesis of NiCo₂S₄ and their charge storage characteristics in supercapacitors

In this work, a facile hydrothermal approach for the shape-controlled synthesis of NiCo₂S₄ architectures is reported. Four different morphologies, urchin-, tube-, flower-, and cubic-like NiCo ₂S₄ microstructures, have been successfully synthesized by employing various solvents. The obtained precursors and products have been characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. It is revealed that the supersaturation of nucleation and crystal growth is determined by the solvent polarity and solubility, which can precisely control the morphology of NiCo₂S ₄ microstructures. The detailed electrochemical performances of the various NiCo₂S₄ microstructures are investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The results indicate that the tube-like NiCo₂S₄ exhibits promising capacitive properties with high capacitance and excellent retention. Its specific capacitance can reach 1048 F g^-1 at the current density of 3.0 A g^-1 and 75.9% of its initial capacitance is maintained at the current density of 10.0 A g^-1 after 5000 charge-discharge cycles.