Graphene–Vanadium Oxide Heterojunction Boosting Electron–Ion Coupling for Ultrahigh Energy Density Carbon Fiber Structural Supercapacitors

Abstract The rapid advancement of drone logistics and electric aviation has created a growing demand for carbon fiber structural supercapacitors (CF–SSCs) that combine energy storage with lightweight and structural functionality. However, achieving high energy density remains challenging due to the chemical inertness of carbon fiber. In this work, it is demonstrated that H 2 V 3 O 8 /rGO is a promising and high‐performance electrode coating for carbon fiber structural supercapacitors that possess both ultrahigh energy density and load‐bearing functionality. Herein, a simple and efficient one‐step high‐temperature mixing hydrothermal method is developed to synthesize H 2 V 3 O 8 /rGO. Density functional theory calculations reveal that strong interfacial synergy between rGO and H 2 V 3 O 8 promotes electron transport and Li + diffusion, boosting efficient electron–ion coupling. The device exhibits high capacitance (964 mF g −1 ) and exceptional energy density (502.1 mWh kg −1 ), exceeding previously reported values. Remarkably, it maintains 88% capacitance retention after 5 000 cycles at 3 A g −1 under a compressive load of 120 kPa, exceeding the 83% retention without load, demonstrating excellent electrochemical load‐bearing stability. In addition, the device shows robust mechanical properties (127.2 MPa tensile strength, 6.95 GPa tensile modulus) and high safety, offering strong potential for practical application. This study proposes a promising strategy for designing CF–SSCs with high energy density.