Text:Supercapacitors, known for their rapid charge/discharge rates and excellent cyclic stability. The doping of two-dimensional (2D) graphene (G) nanosheets can alter the bonding type of carbon atoms and electronic configuration of carbon atoms, and affects the physical and chemical properties of G, which can effectively alleviate the stacking problem of G-based materials, it can be an ideal choice for supercapacitors. In this work, we focused on an one-step green scalable electrochemical exfoliation strategy for the rapid preparation of high-quality thin-layer graphene nanosheets with double halogen doping during synthesis. The as-made chlorine (Cl) and bromine (Br) dual-doped G (Cl/Br-G) nanosheets exhibits the transparent feature with large lateral size. Density functional theoretical calculations brought out that the introduction of Br can enlarge the layer spacing of graphene, and the introduction of Cl can enhance charge distribution. The flexible supercapacitor constructed with electrodes, demonstrates remarkable charge storage performances and impressive mechanical flexibility. In particular, the Cl/Br-G-MSC displays the much higher specific capacitance and long-term cycling stability for 300,000 cycles compared with the single-doping counterparts. This innovative approach to dual halogen doping in G holds significant promise for energy storage, while the electrochemical exfoliation technique offers valuable insights for producing other 2D layered materials.