Material scientists reveal how hidden galvanic corrosion drains zinc batteries, and show how a thin protective interface could help make safer, longer-lasting energy storage practical.
Battery cell cross-section with corrosion and plating. Credit: AI-generated image / OpenAI
A recent study published in the journal Nature Communications investigates a critical degradation pathway that limits the practical deployment of anode-less aqueous zinc batteries. The researchers identify galvanic corrosion between deposited zinc and metallic current collectors as a major previously underappreciated source of irreversible zinc loss. The work advances the understanding of zinc electrode degradation and offers a practical route toward energy-dense, durable aqueous zinc batteries.
Understanding Corrosion-Driven Capacity Loss
Rechargeable aqueous zinc batteries are emerging as promising candidates for large-scale energy storage because they offer low cost, intrinsic safety, and the high theoretical capacity of zinc metal. However, their practical energy density remains limited by the need for substantial excess zinc at the negative electrode. This excess zinc serves as a reservoir to compensate for irreversible zinc losses during repeated cycling, but it also increases cell weight and volume, reducing overall energy-storage efficiency.
Researchers have developed anode-less and initially anode-free battery architectures that minimize or eliminate excess zinc. These designs can significantly improve energy density by maximizing zinc utilization. However, their performance remains limited by irreversible zinc loss, zinc depletion-induced polarization, corrosion, and, in some cases, dendrite-related short-circuiting. Recent studies indicate zinc depletion as a critical failure mechanism under limited zinc inventory. Although some isolated zinc can be recovered, corrosion leads to irreversible zinc loss, and its role in battery degradation remains inadequately understood.
The researchers addressed this challenge by investigating the behavior of zinc electrodes under practical operating conditions. The findings reveal an overlooked degradation pathway and underscore the importance of interfacial engineering to improve battery durability.
Building a Corrosion-Resistant Interface
Researchers investigated zinc electrodes deposited on copper current collectors, which served as the primary model system. Electrochemical measurements, microscopy analysis, and aging studies revealed that direct contact between zinc and copper forms a galvanic couple in the aqueous electrolyte. In this configuration, zinc dissolves preferentially while hydrogen evolves at the copper surface, accelerating zinc consumption and promoting corrosion by-product formation.
To mitigate this degradation pathway, the team developed a hybrid passivation layer composed of a poly(vinylidene fluoride) (PVDF) matrix embedded with metal fluoride particles. The insulating PVDF matrix suppresses electron transfer and restricts electrolyte access to the current collector, while the inorganic fillers regulate zinc nucleation and deposition.
The researchers evaluated several metal fluorides, including SnF2, ZnF2, AlF3, and CeF3. Among these candidates, CeF3 delivered the most favorable balance of zinc reversibility and interfacial stability. The optimized coating used a 90 wt.% metal-fluoride loading, and a thin and scalable passivation layer about 2 μm thick was formed. The team performed finite-element simulations of zinc deposition to understand the underlying mechanism.
Suppressing Corrosion-Induced Degradation
Finite-element simulations revealed that high-permittivity CeF3 induces dielectric polarization, redistributing the local electric field at the electrode surface. By reducing electric-field concentration at the surface, the coating suppresses uneven zinc growth and promotes dense, uniform deposition. This effect improves current collector coverage and helps protect the electrode from corrosion.
Experimental results validated the simulation findings. Bare copper current collectors promoted rough, porous zinc deposits with large exposed surface areas, whereas the PVDF/CeF3 coating enabled dense, planar zinc growth that nearly fully covered the substrate. This compact deposition morphology effectively minimized current collector exposure and suppressed galvanic corrosion.
Electrochemical measurements showed that the passivated interface lowered the galvanic current to about one-third of that on bare copper and reduced cumulative corrosion losses by nearly 68% during aging. Microscopy and surface analysis indicated minimal corrosion product formation and improved preservation of the deposited zinc. Zinc deposits formed beneath the coating exhibited porosities below 5%, whereas deposits on unprotected copper showed highly porous structures. The dense morphology reduced surface reactivity and minimized the formation of electrically isolated zinc.
Corrosion proved to be the primary source of irreversible zinc loss in the tested cells. The hybrid interface reduced irreversible capacity loss by approximately 60% after excluding first-cycle loss and enabled Coulombic efficiencies above 99.8% during prolonged zinc plating and stripping. This enhanced reversibility supported stable zinc plating and stripping in symmetric cells for more than 900 hours under high-depth-of-discharge conditions with minimal voltage hysteresis.
The passivated interface significantly improved calendar-life performance during storage. It suppressed hydrogen evolution, slowed impedance growth, and minimized cell swelling, demonstrating effective mitigation of long-term corrosion-induced degradation.
Enabling Next-Generation Zinc Batteries
This study identifies galvanic corrosion as a critical degradation pathway in anode-less aqueous zinc batteries and demonstrates an effective strategy to suppress it. By integrating high-permittivity CeF3 particles within an electrically insulating polymer matrix, the researchers developed a hybrid interface that limits electron transfer, restricts electrolyte access, and promotes uniform zinc deposition.
The optimized interface delivered significant improvements in battery performance, cycling stability, and operational durability. In coin-type anode-less full cells, the interface supported 80% capacity retention after 720 cycles, while ampere-hour-scale anode-less pouch cells retained 89% capacity after 130 cycles at 0.5 A g-¹. The interfacial strategy also proved effective in initially anode-free pouch-cell configurations, delivering device-level energy densities exceeding 90 Wh L-¹, approaching the range reported for commercial lead-acid batteries.
The study establishes a general interfacial engineering strategy for metal-anode systems. By leveraging dielectric polarization to regulate local electric fields, the approach provides an effective means to control corrosion and guide uniform metal deposition.
Additional experiments using barium titanate suggested that the mechanism is not inherently dependent on rare-earth or fluoride chemistry, indicating that these design principles could be extended to other batteries where interfacial instability limits performance.
As efforts to develop safer, higher-energy, and longer-lasting energy-storage technologies continue, corrosion-conscious interface engineering may provide a valuable pathway toward practical next-generation metal batteries.
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