Two-dimensional Spinel Structured Co-based Materials for High Performance Supercapacitors: A Critical Review

Abstract Under the time theme of the energy crisis and environmental pollution, a great deal of attention has been devoted to the field of supercapacitors (SCs) for relieving this situation. Two-dimensional (2D) materials show great potential in various energy storage fields due to their unique and attractive characteristics. Especially, different types of 2D spinel structured Co-based MCo2O4 (M = Co, Ni, Zn, Cu, Fe, and Mn) materials are supposed to be promising candidates of electrode materials for SCs, which ascribes to their natural abundance and superior electrochemical performances including relatively high electron conductivity, rich electroactive sites, high specific capacitance, and good cycling stability. Moreover, 2D spinel structured Co-based materials can incorporate with other nanomaterials to form various diverse composites such as heterostructures, carbonaceous composites, transition metal oxide (TMO) composites, transition metal hydroxide (TMH) composites, transition metal sulfide (TMS) composites, transition metal phosphide (TMP) composites, and ternary composites, which can deliver satisfactory electrochemical performances. In this review, we highlighted the 2D spinel structured Co-based materials and their composites for SC applications. Finally, the future challenges and outlooks of 2D spinel structured Co-based materials in energy storage devices were also discussed.