Low-Temperature-Resilient and High-Rate Polypyrrole-Vanadium Oxide Carbon Fiber Structural Supercapacitors with Superior Mechanical-Electrochemical Synergy

The rapid expansion of the low-altitude economy-particularly the development of unmanned aerial vehicles (UAVs) and electric aircraft-has intensified the trade-off between flight endurance and payload capacity. Carbon fiber structural supercapacitors (CF-SSCs) offer a promising solution by integrating energy storage into load-bearing components; however, the inherent chemical inertness of carbon fibers restricts device capacitance, and their low-temperature electrochemical behavior remains largely unexplored. Here, we construct an H2V3O8@PPy composite electrode via in situ low-temperature oxidative polymerization. The uniform PPy coating facilitates rapid interfacial kinetics, provides reversible pseudocapacitance, and buffers the volume expansion of the H2V3O8 nanorods. The assembled H2V3O8@PPy@CF-SSC achieves a high specific capacitance of 1082.4 mF g-1 and an energy density of 573.6 mWh kg-1. Crucially, the device maintains 42.1% capacitance retention at -10 degrees C, delivering an energy density of 165 mWh kg-1 surpasses the performance of most previously reported CF-SSCs. Furthermore, the device demonstrates robust mechanical properties, featuring a tensile strength of 126.5 MPa and a tensile modulus of 6.92 GPa. This work fills the gap in low-temperature CF-SSC research and provides guidance for the design of high-energy-density structural energy-storage devices for extreme environments.