MXenes for Non-Lithium-Ion (Na, K, Ca, Mg, and Al) Batteries and Supercapacitors

The 2019 Nobel Prize in Chemistry for lithium-ion batteries is a powerful confirmation of the importance of portable energy storage devices, which will further promote collaborative innovation in the field of new energy storage. Non-lithium rechargeable energy storage technologies are attracting attention due to their low cost and high energy densities. However, electrochemical performance depends upon the inherent properties of the electrodes. In recent decades, 2D materials have been extensively investigated owing to their unique physical and chemical properties. One of the typical representatives is the MXenes with good electrochemical properties, which have become popular material in the field of energy storage in recent years. The discovery of MXene with metal solution, expanded interlayer-spacing and tamperable surface termination offers a valuable strategy to discover MXenes with new structures. These flexible properties of MXene allow the tuning of properties for energy storage technologies. Here, the synthesis, structure, properties and applications of MXenes in non-lithium energy storage technologies are reviewed, and a comprehensive outlook and personal perspective on the future development of MXene in the energy storage system are also presented.