Homogenizing Zn Deposition in Hierarchical Nanoporous Cu for a High‐Current, High Areal‐Capacity Zn Flow Battery

Abstract

AbstractA Zn anode can offset the low energy density of a flow battery for a balanced approach toward electricity storage. Yet, when targeting inexpensive, long‐duration storage, the battery demands a thick Zn deposit in a porous framework, whose heterogeneity triggers frequent dendrite formation and jeopardizes the stability of the battery. Here, Cu foam is transferred into a hierarchical nanoporous electrode to homogenize the deposition. It begins with alloying the foam with Zn to form Cu5Zn8, whose depth is controlled to retain the large pores for a hydraulic permeability ≈10−11 m2. Dealloying follows to create nanoscale pores and abundant fine pits below 10 nm, where Zn can nucleate preferentially due to the Gibbs–Thomson effect, as supported by a density functional theory simulation. Morphological evolution monitored by in situ microscopy confirms uniform Zn deposition. The electrode delivers 200 h of stable cycles in a Zn–I2 flow battery at 60 mAh cm−2 and 60 mA cm−2, performance that meets practical demands.