Structural engineering of MXenes towards high electrochemical performance in supercapacitors

Supercapacitors (SCs) stand out among various energy storage devices owing to their high power density and long-term cycling stability. As new two-dimensional material, MXenes have become a research hotspot in recent years owing to their unique structure and rich surface functional groups. Compared with other materials, MXenes are more promising for SCs owing to their tunable precursors, structural stability, and excellent electrical conductivity. However, the rate performance and electrochemical reaction activity of MXene materials are poor, and stacking severely limits their application. Therefore, various modification strategies are employed to improve the electrochemical performance of MXene materials. As the modification strategy of MXene electrode materials often involves increasing the number of ion transport channels to expose more active sites, the packing density is also affected to different degrees. Therefore, achieving a balance between high volumetric capacitance and rapid ion transport has become a key issue for the application of MXene-based SCs in wearable devices and microdevices. In this paper, the latest progress in the preparation methods and modification strategies of MXenes in recent years is reviewed with the aim of achieving both high volumetric capacitance and high ion transport for expanding the application of MXene-based SCs in microdevices and wearable devices.