Nanostructured Ni compounds as electrode materials towards high-performance electrochemical capacitors

Abstract

Integration of Ni compound-based nanomaterials into energy storage devices, especially electrochemical capacitors, offers opportunities to timely meet the ever increasing demands of fast charging/discharging processes, longer cycle life, and higher power density and energy density. Besides that, Ni compound-based nanomaterials are also found to bring such merits as high electrochemical activity, low price, and being environmentally friendly. Therefore, it is crucial to design nanostructured Ni compound-based nanomaterials towards high-performance electrochemical capacitors and understand the role of morphology in enhancing the electrochemical performance at the atomic or molecular scale. In this review, we focus on the rational design and synthesis of different structured Ni compound-based nanomaterials, such as nickel oxides, ternary Ni-based metal oxides, nickel sulfides, ternary Ni-based metal sulfides, Ni-based metal organic frameworks, and their composites. More importantly, their electrochemical performances are also discussed by virtue of the effects of morphology, structure, and composition of Ni compound-based materials. Finally, the main challenges as well as opportunities that researchers are facing now in the field of Ni compound-based nanomaterials for electrochemical energy storage are summarized. We hope that this review will shed light on the development of Ni compound-based nanostructured electrodes and exploitation of their energy storage mechanisms towards high-performance electrochemical capacitor applications.