Two-dimensional MXene based innovative electrode materials for supercapacitors: Recent advances and prospects

Electrochemical energy storage (EES) devices, including various batteries and supercapacitors (SCs), have emerged as promising candidates and have attracted tremendous interest in recent years. Among various EES devices, rechargeable batteries are leading the way in terms of high-energy density. Though significant developments rechargeable batteries suffer from low power density and high-cost problems. Besides, SCs are recently booming due to long cycle life, wide working temperature range, high safety, and high maintainability. The electrochemical performance of SCs highly depends on selecting efficient electrode materials. This review work is focused on two-dimensional (2D) MXenes, an emerging electrode material with high electrochemical performance for SC application. Owing to MXenes' fascinating properties, this work accumulates the recent research regarding MXene-based electrode materials for SCs. In this work, we briefly discuss the crystal structure of 2D MXenes along with their various properties. We pay special attention to recent innovative pristine MXenes and MXene-based composite/hybrid electrode materials for SC application. For the first time in this work, we shed light on MXene-based composites with different families, like carbon, graphene, polymers, metal-organic frameworks (MOFs), transition metal oxides (TMOs), transition metal dichalcogenides (TMDs), etc. The characterization and electrochemical performance of MXene-based electrode materials are discussed in detail, and experimental and theoretical studies are given. We also discussed the importance of selecting the electrolytes for the SC application to obtain high performance. Finally, the crucial future outlook and perspective for developing MXene-based electrode materials for SCs are highlighted. We hope this work will provide helpful insights for selecting 2D MXene electrode materials for the SC application.