Double-Doped Carbon-Based Electrodes with Nitrogen and Oxygen to Boost the Areal Capacity of Zinc-Bromine Flow Batteries

Ensuring a stable power output from renewable energy sources, such as wind and solar energy, depends on the development of large-scale and long-duration energy storage devices. Zinc-bromine flow batteries (ZBFBs) have emerged as cost-effective and high-energy-density solutions, replacing expensive all-vanadium flow batteries. However, uneven Zn deposition during charging results in the formation of problematic Zn dendrites, leading to mass transport polarization and self-discharge. Stable Zn plating and stripping are essential for the successful operation of high-areal-capacity ZBFBs. In this study, we successfully synthesized nitrogen and oxygen co-doped functional carbon felt (NOCF4) electrode through the oxidative polymerization of dopamine, followed by calcination under ambient conditions. The NOCF4 electrode effectively facilitates efficient "shuttle deposition" of Zn during charging, significantly enhancing the areal capacity of the electrode. Remarkably, ZBFBs utilizing NOCF4 as the anode material exhibited stable cycling performance for 40 cycles (approximately 240 h) at an areal capacity of 60 mA h/cm2. Even at a high areal capacity of 130 mA h/cm2, an impressive energy efficiency of 76.98% was achieved. These findings provide a promising pathway for the development of high-areal-capacity ZBFBs for advanced energy storage systems.