Ultrathin 2D metallenes for energy storage: a myth or reality?

Abstract

Rapid depletion of fossil fuels and increased energy scarcity have paved the way for the use of electrochemical energy storage devices, such as rechargeable batteries and supercapacitors, to power electronic devices. Ultrathin two-dimensional (2D) materials have attracted significant research interest due to their prominent characteristics, including large surface area, lightweight, good electronic conductivity, and good chemical and electrochemical properties. Metallenes are emerging class of 2D materials with an atomic thickness and consisting of metals or alloys with a well-controlled surface atomic arrangement. 2D metallenes are invariably used as electrode-active materials in energy storage devices such as rechargeable batteries and supercapacitors in the literature. Since metallenes consist of metallic 2D sheets, charge storage is limited by electrode kinetics and the electrode is more prone to corrosion when used in electrolytes. This motivated us to examine the truth behind these fascinating materials. We critically analysed the various types of metallenes available to date, their synthesis methods, and the mechanism of charge storage in rechargeable batteries and supercapacitors for better clarification.