The removal of the "A" group layer from the MAX conductive ceramics(a family of ternary transition metal carbides or nitrides) phases results in two-dimensional materials which are named as MXene to denote the loss of the A element and emphasize their structure similarities with graphene. MXene is an emerging functional material in the field of two-dimensional crystal materials, which has excellent electric conductivity, low resistance of ion, strong mechanical strength, highly hydrophilic surface and 2D layer structure. As a novel kind of functional material, the methodology for preparing MXene and the potential applications have triggered tremendous interests. Until now, only 20 MXenes have been successfully synthesized and their composite materials have been demonstrated superior performance when applied in electrochemical energy storage, including secondary battery(Li-ion batteries and non-Li-ion batteries, i.e. Na⁺, K⁺, Mg²⁺, Ca²⁺ and Al³⁺) and electrochemical supercapacitor. In this review, the recent preparation methods and properties of MXene, especially the electrical characteristics, are summarized and compared. Then the applications of MXene materials in electrochemical energy storage are discussed in detail. The challenges and future perspective in the application of MXene materials are lastly outlined.
Contents
1 Introduction
2 Synthesis of MXene materials
2.1 HF etching
2.2 Fluoride-HCl mixture etching
2.3 Other approach
2.4 Synthesis of few/single layer MXene
3 Properties of MXene
3.1 Electronic properties
3.2 Electromagnetic properties
3.3 Mechanical properties
4 The applications in electrochemical energy storage of MXene materials
4.1 Lithium ion batteries
4.2 Non-lithium ion batteries
4.3 Lithium sulfur batteries
4.4 Supercapacitors
5 Conclusion and perspective