Nickel Disulfide (NiS2): A Sustainable Low‐Cost Electrode Material for High‐Performance Supercapacitors

In the family of transition metal sulfides, nickel disulfide (NiS2) received significant attention in the recent past, particularly as an electrode‐active material for supercapacitors due to its high specific capacitance, high power density, long cyclic stability, and low cost. A detailed overview on the supercapacitor applications of NiS2 is lacking in the literature. In this review article, the unique features of NiS2 in terms of its various methods of synthesis, characterizations, and electrochemical performance evaluations are described. This review provides an in‐depth understanding on the unique properties of ultrathin nanostructured NiS2 such as structural properties, electronic properties, optical properties, and so on. Later, the various methods of synthesis including hydrothermal method, solvothermal method, solvent‐free approach, and so on are reviewed. Further, the strategies are discussed to improve the electrochemical performance of NiS2 by preparing hybrids or nanocomposites with other types of electrode‐active materials. The influence of electrode nanostructure and surface morphology on the charge storage is discussed with the help of specific examples. Furthermore, the potential challenges and future perspectives of NiS2 for commercial supercapacitors are examined. This review proclaims the development of novel approaches and strategies for the effective utilization of NiS2‐based electrodes for high‐performance low‐cost supercapacitors. A detailed review on the NiS2‐based electrodes for supercapacitors is provided. The crystal structure and various properties such as structural, electronic, and optical are discussed. The electrochemical performance evaluations of NiS2‐based supercapacitor electrodes and supercapacitors are explained with cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge measurements.