Recent Progress of MXenes in Aqueous Zinc-Ion Batteries

Abstract

In recent years, aqueous zinc-ion batteries (AZIBs) have received considerable interest as a novel and promising alternative energy storage technology. Owing to their particular structural traits and physicochemical qualities, MXenes as cathodes impart significant beneficial properties to AZIBs, such as readily modifiable two-dimensional (2D) structure, high electrical conductivity, desirable chemical composition, and controllable surface chemical properties. This review includes a comprehensive discussion on the progression of MXenes in AZIBs in relation to the most sophisticated structural design and performance optimization methodologies available for the construction of cathodes and anodes. MXenes may be utilized directly as an active material or a precursor of an active material in cathodes to achieve a long cycle life and high rate performance because of their contribution, which is summarized as follow: (1) MXenes with a 2D layered structure and high conductivity can be employed as a conductive substrate in combination with manganese and vanadium oxides to enhance the cycle and rate performance of composite materials; (2) zinc ion transport kinetics is accelerated in manganese and vanadium oxide composites when 3D MXenes are used as a substrate; (3) MXenes allow excellent electrolyte penetration owing to the presence of abundant hydrophilic functional groups, which may enhance the electrochemical response of composite electrode materials; (4) MXene derivatives contain a broad range of surface functional groups and exhibit high activity and a wide voltage window; (5) MXenes possess remarkable mechanical flexibility, allowing for the production of flexible wearable AZIBs. Moreover, MXenes can be employed as a 2D/3D host, zincophilic seed matrix, and zinc interface protection layer to retard zinc metal corrosion and dendrite formation when zinc metal is used as the anode because of the following advantages: (1) MXenes have a 2D structure and multi-functional surface, allow excellent water dispersion, and can be processed into various porous skeletons; (2) MXenes exhibit excellent electrical conductance and ion diffusion, allowing for rapid electrochemical kinetics during zinc plating/stripping; (3) lattice size compatibility between MXenes and zinc metal allows zinc metal to nucleate and deposit evenly; (4) the abundant functional groups on the MXene surface may serve as zincophilic and nucleation sites to promote the homogeneous nucleation and deposition of zinc. The review also highlights the electrochemical deposition (for zinc foil) and physical mixing techniques for using MXenes as a host to encapsulate zinc (for zinc powder). Moreover, the discussion is directed to the use of MXenes as an electrolyte additive for AZIBs and as an inorganic filler for solid electrolytes to prevent dendrite formation and corrosion issues in zinc anodes. Finally, the challenges and prospects of using MXenes in AZIBs are presented.