MXenes with applications in supercapacitors and secondary batteries: A comprehensive review

Two-dimensional (2D) materials have received tremendous attention because they possess a set of merits not available in bulk materials, such as large specific surface area, low energy barrier for electron transportation and short ion diffusion path. These advantages are desirable especially for the electrodes in electrochemical energy storage devices. MXenes, first synthesized in 2011 by etching their MAX phase precursors, have plural reasons to represent a new family of 2D materials. Their rich diversity in structure and composition together with the uncommon combination of good electrical conductivity and hydrophilicity makes themselves outstand in the whole 2D materials world. Based on these advantages, MXenes hold great promise for various technologically important applications, particularly in developing new energy storage techniques for advanced smart systems, such as portable and flexible electronics. There have been remarkable research achievements in the synthesis and application of MXene-based materials. While new synthesis routes being continuously reported, MXenes with new composition and novel structure have also been routinely discovered, which will undoubtedly help understand the fundamental properties and expand the application scope of MXenes. As for their energy storage-related applications, to cope with the intrinsic weakness of MXenes, many endeavors have been made by doping, structure-tuning and compositing with hybrid ingredients. In this review, the current status of MXenes synthesis and up-to-date progress of their applications in supercapacitors, metal-ion batteries and lithium sulfur batteries are summarized and discussed, and the typical work on the application of MXenes for the aforementioned three categories is respectively tabulated for reference and comparison.