Zinc (Zn) plating/stripping is a promising anodic electrochemical reaction for aqueous batteries because of its high safety, low cost, two electron transfer, and rapid reaction kinetics. However, the notorious dendrite growth of Zn has become one of the biggest obstacles hindering its further commercialization. A multifunctional binder-free tin (Sn)-modified 3D carbon felt anodic host (SH) is constructed for aqueous zinc-based flow batteries (ZFB) via a facile and scalable strategy. Compared with the pristine carbon felt host (PH), the as-fabricated SH affords more robust Zn nucleation sites, lower hydrogen evolution reaction potential and lower nucleation overpotential of Zn and thus better induces uniform Zn plating/stripping with very high Coulombic efficiency (CE). Based on such an SH, a symmetrical flow battery exhibits superior CE (290 cycles with average CE of 99.4%) and a zinc-bromine flow battery demonstrates a longer cycle life (142 cycles with average CE of 97.2%), much better than pristine PH. This is a simple, novel, and effective way to suppress Zn dendrites and improve the performance of ZFBs.