Electrochemical properties of heteroatom doped graphyne sheet for energy storage devices

Electrical double layer capacitors (EDLCs) have attracted significant attention because of their excellent power density, superb cycling stability, and fast charging/discharging speed. However, EDLCs are significantly limited in use due to their poor energy density. The challenge is to increase the energy density of EDLCs without affecting their excellent power density and cycle stability. Among the components of the electrode, the active material plays a crucial role in determining charge storage and kinetic characteristics, depending on its structure and morphology. New active materials are required for the development of high-performance EDLCs. We report the fabrication of F-doped graphyne (F-Graphyne-Ar) using planetary milling in Ar atmosphere and hydrothermal method. F-Graphyne-Ar has sp–sp² hybridized structure with excellent electrical/ionic conductivity and fine particles size. Additionally, the F doping reinforces the electrical conductivity and expands the graphyne structure. The F-Graphyne-Ar electrode shows excellent low- and high-rate performance (138.5 F g⁻¹ at current density of 0.2 A g⁻¹ and 88.0 F g⁻¹ at current density of 20 A g⁻¹) with fine cycling stability (capacity retention of 84.3 % after 5000 cycles at a current density of 3 A g⁻¹). The excellent performance of F-Graphyne-Ar is attributed to the synergistic effect of increased electrochemical activity induced by the fine particle size and enhanced ionic/electrical conductivity caused by alkynyl carbon and F doping. The fabricated F-Graphyne-Ar plays a role an excellent active material in EDLC having high-capacity, excellent ultrafast performance, and highly stable energy storage capability in EDLCs. Therefore, F-Graphyne-Ar as a new two-dimensional carbon allotrope is a promising candidate for active material of EDLCs.