Recent progress in MXene-based nanomaterials for high-performance aqueous zinc-ion hybrid capacitors

Aqueous zinc-ion hybrid capacitors (ZHCs) have an intrinsic safety and low cost, and are promising for use in large-scale energy storage devices. However, traditional porous carbon cathodes have inappropriate pore structures for zinc ion storage and diffusion. Moreover, zinc foil anodes suffer from the growth of Zn dendrites and side reactions, so that traditional ZHCs usually have a non-competitive energy density and unsatisfactory service life, seriously inhibiting their practical use. Two-dimensional transition metal carbide/nitride MXenes with a highly conductive matrix and abundant surface functional groups are good choices for constructing high-capacity cathodes and long-life Zn anodes for high-performance ZHCs. Recent progress in MXene-based nanomaterials as electrode materials of advanced ZHCs is summarized. The fundamentals of ZHCs are first introduced, such as working principles and key electrochemical parameters. The use of various MXene-based cathodes and anodes in high-performance aqueous ZHCs are then considered and, finally, the challenges and prospects for MXene-based nanomaterials for next-generation ZHCs are briefly discussed.