Preparation and theoretical analysis of NiCo2O4: xS series materials for high-performance supercapacitors

Nickel cobalt oxide and sulfide electrode materials with various nanostructures were synthesized via a facile hydrothermal method. The structural, morphological, electrochemical, and electronic properties of the electrode materials were studied to evaluate the effect of S addition into NiCo2O4. The results indicated that S atoms can influence the lattice structure and morphology, and appear to improve the electrochemical performance of the material. Excellent specific capacitance and cycling stability were found in the samples. The NiCo2S4 sample exhibited the highest specific capacitance of 1302 F/g at a current density of 1 A/g and a capacity retention of 92.4% after 5000 charge-discharge cycles. First-principles calculations were performed to provide more insight into the mechanism of improved electrochemical performance when S atoms were added to NiCo2O4 and demonstrate their potential as excellent electrode materials. In the NiCo2O4:xS series materials, the addition of S effectively manipulates the surface morphology and interfacial charge states of the materials to achieve superior electrochemical performance.