The quest for negative electrode materials for Supercapacitors : 2D materials as a promising family

With increasing clean energy demands and the rapid progress of flexible electronics, research on high–performance supercapacitors (SCs) has recently attracted significant attention. Two–dimensional (2D) materials have attained great interest for energy applications due to their distinctive physical, chemical, and electrochemical properties. Although significant advances have been made for positive–electrode (cathode) materials, a negative–electrode (anode) is comparatively less explored for SCs applications. Anode plays a vital role in getting the overall high performance of SC devices; however, it is challenging to strike a balance between anode and cathode. This review focuses on the recent advances in 2D materials–based negative electrodes for SCs beyond carbon/graphene–based materials. First, we briefly introduce the general classification, structure, and importance of negative electrodes for SC and technological advances in device fabrications. We then summarized the various 2D materials–based negative electrodes for SCs: graphene, metal carbides/nitrides (MXenes), metal oxides, metal sulfides, metal selenides, metal nitrides, and metal–organic framework–derived 2D materials. The excellent controllability and diversity of the surface properties and chemical composition of 2D materials can provide a valuable opportunity to enhance the overall performance of SCs. Finally, the challenges and outlooks for the future development of 2D materials–based negative electrodes for SCs are discussed.