Heteroatom doped S, N-MXene/rGO flexible film for supercapacitor applications

MXenes have demonstrated remarkable potential in flexible electronics on account of their two-dimensional structure, high electrical conductivity, rich functional groups and excellent flexibility. However, the unavoidable self-restacking of MXene sheets inevitable leads to a significant reduction in both the electrochemical reaction active specific surface area and the energy storage capacity. It remains a great challenge to further increase the energy storage capacity of MXene based film electrodes. To address these concerns, in this research we have employed co-doping S and N elements and introducing rGO into MXene based. The resulting films can not only prevent the self-restacking of pristine MXene sheets but also preserve the excellent flexibility intrinsic to MXene, leading to the ultrahigh electrochemical performance. The S, N-MXene/rGO flexible film possesses an ultrahigh volumetric capacity of 2414.6F cm⁻³ at 1 A/g, significantly outperforming that of the S, N-MXene film (1794.2F cm⁻³) as well as the pristine MXene film (617.1F cm⁻³). The resulting S, N-MXene/rGO film electrode also demonstrates excellent rate capability, retaining a volumetric capacity of 1580.5F cm⁻³ at 10 A/g. The in-situ Raman and DFT results further reveal that the S, N-MXene/rGO hybrid film electrode displays rapid reversible electron transfer during charge/discharge processes with the heteroatoms (S and N) co-doping. Additionally, the soft packing pouch cell S, N-MXene/rGO//rGO enables the maintenance of long-time cycle stability, achieving a good capacity retention rate of 81.8 % after 5500 charge/discharge cycles. Moreover, it possesses a high energy density of 144.6 Wh kg⁻¹, along with a power density of 875.9 W kg⁻¹, which fully demonstrated its outstanding electrochemical performance.