Research progress on construction and energy storage performance of MXene heterostructures

MXenes are a family of two-dimensional(2 D) transition metal carbides, carbonitrides/nitrides with superior physical and chemical properties, which have attracted extensive attention since the discovery in2011. The impressive electrochemical activity of MXene makes it one of the most potential electrode materials in rechargeable batteries and supercapacitors. However, single-component MXene electrodes are difficult to achieve high specific capacity, efficient ion/electron transport, and high stability compatibility in an electrochemical environment. Studies have shown that it is an effective method to introduce nanomaterials between MXene layers to construct heterostructures and to improve the electrochemical performance through the synergistic effect among the components in the heterostructures. The introduction of nanomaterials can effectively suppress the restacking of MXene nanosheets, shorten the diffusion path of ions and promote the electrolyte transport, which is beneficial to enhance the rate performance of MXene; moreover, the excellent mechanical flexibility of MXene can reduce the volume expansion of nanomaterials during charge/discharge, thereby effectively protecting the integrity of the electrode structure and improving the cycling stability. Therefore, in this review, combined with theoretical calculations,we summarize the recent advances of MXene heterostructures in terms of synthesis strategies and energy storage applications, including supercapacitors, metal-ions batteries(Li, Na, K, Mg, Zn, Al) and metal anode protection. Furthermore, potential challenges and application perspectives for MXene heterostructures are also outlined.