Review on recent advances in nanostructured transition-metal-sulfide-based electrode materials for cathode materials of asymmetric supercapacitors

In the past decades, energy storage devices have drawn widespread attention in diverse fields including hybrid electric vehicles and smart portable electronics. By taking advantage of two different electrode materials, asymmetric supercapacitors (ASCs) can extend their operating voltage window and display more excellent energy-storage capacity than those of symmetric supercapacitors. Recent developments demonstrated that transition metal sulfides (TMSs) have emerged as a promising class of materials for ASCs due to their low cost, fascinating redox reversibility and electronic conductivity. In this review, the latest progresses in various types of TMS-based electrode materials for ASCs are summarized. Particularly, the study places emphasis on the impact of morphological control and composite engineering on the final electrochemical performances of the materials. Moreover, some effective strategies and potential challenges for further development of TMS-based electrode materials are discussed. It is believed that an in-depth understanding would be a guide for designing TMSs with ideal electrochemical performances in the future.