Mesoscale Electrode Engineering via Rapid Carbothermic Reduction: Mitigating Transport–Reaction Mismatch in High-Power Vanadium Flow Batteries

The large-scale application of vanadium flow batteries (VFBs) is critically limited by low power density, a consequence of the severe mass transport–reaction mismatch within conventional carbon felt electrodes. To overcome the challenge, we pioneer a rapid microwave-induced carbothermic reduction (MICR) technique for mesoscale electrode engineering with cooptimized ion transport and catalytic activity. Initiated by finite element simulations that reveal the fundamental importance of uniform pore networks in eliminating concentration polarization and parasitic reactions, our MICR strategy enables ultrafast (within 10 s), precisely controlled gradient pore systems integrating 0.4 μm defect cavities with 2–10 nm mesopores across fiber surfaces. Simultaneously, this process in situ generates abundant oxygen-containing functional groups that markedly enhance the adsorption energy and redox kinetics of vanadium ions, as confirmed by density functional theory calculations. The resulting MICR-engineered electrode empowers a VFB to achieve peak power density of 932.69 mW cm–2 alongside excellent long-term durability, maintaining 74.67% energy efficiency over 1000 cycles at a high current density of 300 mA cm–2. This work establishes a scalable manufacturing paradigm that merges computational design with practical synthesis, enabling high-power-flow batteries through rational mesoscale electrode engineering.