Electron-Deficient Sites Constructed by Boron Doping Induce Homogenous Zn Deposition in Alkaline Zinc–Iron Flow Batteries

Alkaline zinc-iron flow batteries (ZFBs) have recently attracted renewed attention. However, the critical issues with zinc anodes, such as dendrite formation, side reactions, and labile plating or stripping, have yet to be adequately addressed. Here, an attempt is made to overcome these challenges by designing Boron-doped carbon-felt (B–CF) electrodes rich in electron-deficient sites and defects. The fabricated B–CF provides improved adsorption of negatively charged Zn(OH) 4 2− , robust Zn nucleation sites, and lower Zn nucleation and deposition overpotentials, leading to homogeneous Zn deposition morphology. Uniform Zn deposition enables the prevention of undesirable dendrite growth and parasitic reactions. As a result, the constructed alkaline ZFBs achieve a high average Coulombic efficiency of ≈99.85% and energy efficiency of 88% with uniform Zn deposition during 300 cycles (40 mA cm −2 ). This work expands the understanding of the electrode design strategy for achieving favorable Zn plating/stripping.