Minimizing galvanic corrosion for durable anode-less aqueous zinc batteries

Anode-less aqueous zinc batteries offer a promising route to energy-dense and intrinsically safe energy storage, yet their practical deployment is hindered by poor reversibility under constrained zinc inventory. Here, we identify galvanic corrosion between deposited zinc and current collectors as a critical but previously underappreciated degradation pathway in anode-less aqueous zinc batteries. A hybrid passivation layer, comprising an electrically insulating polymer matrix embedded with high-permittivity metal fluorides, is designed to mitigate parasitic electron transfer and limit current collector exposure. The resulting dielectric polarization homogenizes the interfacial electric field, promoting planar and dense zinc deposition that isolates the current collector and suppresses corrosion. Consequently, irreversible zinc loss during both cycling and calendar ageing is reduced, enabling stable zinc plating/stripping for over 900 h at 5 mA cm^-2/3 mAh cm^-2 with 51% depth of discharge. Ampere-hour-scale anode-less full cells deliver 89% capacity retention after 130 cycles at 0.5 A g^-1, with minimal self-discharge during calendar ageing, and initially anode-free pouch cells achieve device-level energy densities exceeding 90 Wh L^-1. This work advances the mechanistic understanding of corrosion processes and motivates corrosion-conscious engineering of heterogeneous interfaces across broader metal battery systems.