Engineered 2D MXene-based materials for advanced supercapacitors and micro-supercapacitors

The class of two-dimensional transition metal carbides/nitrides/oxycarbides (known as MXenes) has shown great potential in energy storage applications due to their intrinsic layered structure, outstanding electrical conductivity, tunable surface chemistry, and unique physicochemical properties. This review summarizes the latest progresses of MXene-based materials for supercapacitors and micro-supercapacitors. First, state-of-the-art structural engineering strategies for the construction of novel MXene-based electrodes are highlighted, as the electrochemical performance of MXenes is influenced by their structure, such as interlayer spacing and surface functional group density. Furthermore, the charge storage mechanisms of MXene-based electrodes in different electrolytes are discussed to stimulate further design and development of tailored materials for high-performance devices. Moreover, different device fabrication technologies are summarized and the achievements of specific device geometries (e.g., fiber-shape, planar-type, and three-dimensional devices) containing MXene-based materials are critically reviewed. Finally, perspectives and outlook for the development of high-performance MXene-based electrodes in terms of material engineering, performance improvement and device innovation are provided, clearly indicating research directions for next-generation advanced energy storage devices.