A Bilayer Electrode Architecture Enabling SnO 2 ‐Induced Spatial‐Controllable Zinc Deposition for Ultra‐High‐Areal‐Capacity Zinc‐Based Flow Batteries

ABSTRACT Aqueous zinc‐based flow batteries (ZFBs) show great promise for large‐scale energy storage. However, the practical deployment of ZFBs is hindered by a limited areal capacity, due to uncontrolled zinc deposition and low utilization of electrode volume. Herein, we propose a spatially controllable deposition strategy enabled by a bilayer electrode architecture, featuring a SnO 2 ‐functionalized carbon felt (CF) as the bottom layer and a pristine CF as the top layer. This architecture introduces a steep gradient in nucleation overpotential and zincate affinity that counteracts the ionic migration trend, reversing the deposition behavior from surface‐clogging mode to internal‐to‐external filling. This unique mechanism enables an ultrahigh areal capacity of 330 mAh cm −2 and an ultrahigh volumetric capacity of 1100 mAh cm −3 , representing a 65% improvement over conventional electrodes. Even under a harsh condition of 100% state of charge and 100% depth of discharge at 240 mAh cm −2 , the battery demonstrates exceptional durability over 175 cycles. This work significantly expands volume utilization for zinc deposition via a bilayer electrode design, providing a robust strategy for regulating spatial deposition behavior and paving the way for practical high‐areal‐capacity ZFBs.