Zinc-based batteries have gained attention for their potential in energy storage due to zinc's natural abundance, low cost, and high theoretical capacity. However, zinc anodes face significant challenges, primarily due to corrosion and dendrite formation, which reduce cycle life and efficiency. Addressing these issues requires effective corrosion prevention methods, including chemical inhibitors and coating technologies. This article examines the role of lead (Pb), indium (In), and bismuth (Bi) additives as well as coating strategies in mitigating zinc corrosion, analyzing their effectiveness in different electrolytes and their impact on electrochemical performance.

Corrosion in zinc anodes occurs through hydrogen evolution and self-discharge, particularly in acidic and alkaline electrolytes. In acidic media, zinc dissolves readily, while in alkaline solutions, passivation layers form but can lead to uneven deposition and dendrite growth. Chemical inhibitors and coatings are employed to stabilize the anode-electrolyte interface, suppress side reactions, and promote uniform zinc deposition.

Lead, indium, and bismuth additives are commonly used to reduce corrosion in zinc anodes. These metals modify the hydrogen overpotential on zinc surfaces, thereby suppressing hydrogen evolution. In acidic electrolytes, lead additives have shown effectiveness by forming a protective layer that reduces zinc dissolution. Studies indicate that lead concentrations as low as 0.1 wt% can decrease corrosion rates by up to 50% in sulfuric acid-based systems. However, lead's toxicity raises environmental concerns, limiting its widespread adoption.

Indium is another effective inhibitor, particularly in alkaline electrolytes. It enhances the hydrogen evolution overpotential, reducing self-discharge. Indium additives in concentrations of 0.05–0.2 wt% have been shown to improve cycle life by up to 30% in zinc-air batteries. The mechanism involves indium adsorbing onto the zinc surface, forming a barrier against electrolyte penetration. Despite its benefits, indium is costly and scarce, making it less practical for large-scale applications.

Bismuth offers a balance between effectiveness and environmental acceptability. In both acidic and alkaline electrolytes, bismuth additives reduce corrosion by forming intermetallic compounds with zinc, which stabilize the anode surface. Research demonstrates that bismuth at 0.2–0.5 wt% can suppress hydrogen evolution by 40–60% without significantly affecting discharge capacity. Bismuth-modified zinc anodes also exhibit improved cycling stability due to reduced dendrite formation. Compared to lead and indium, bismuth presents a more sustainable option with lower toxicity.

While chemical inhibitors are effective, they often introduce tradeoffs in electrochemical performance. Increased additive concentrations may reduce corrosion but can also decrease energy density due to inactive material incorporation. Additionally, some inhibitors may alter deposition morphology, leading to uneven zinc stripping and plating. Optimizing additive concentrations is critical to balancing corrosion suppression with battery performance.

Coating technologies provide an alternative or complementary approach to chemical inhibitors. Coatings physically isolate the zinc anode from the electrolyte, preventing direct contact and reducing parasitic reactions. Common coating materials include conductive polymers, carbon-based layers, and inorganic films.

Polymer coatings, such as polyaniline or polypyrrole, are widely studied for zinc anodes in alkaline electrolytes. These coatings act as ion-selective barriers, allowing zinc ion transport while blocking water and oxygen. Studies report that polymer-coated zinc anodes exhibit up to 70% lower corrosion rates compared to uncoated anodes. However, polymer coatings may increase interfacial resistance, slightly reducing power output.

Carbon-based coatings, including graphene and carbon nanotubes, enhance conductivity and provide mechanical stability. Graphene-coated zinc anodes demonstrate improved corrosion resistance due to the material's impermeability to electrolytes. In acidic systems, graphene coatings reduce zinc dissolution by forming a protective layer that maintains electrical contact even during cycling. The tradeoff lies in coating uniformity—defects or incomplete coverage can lead to localized corrosion.

Inorganic coatings, such as titanium dioxide or zinc oxide, offer chemical stability and mechanical robustness. These coatings are particularly effective in alkaline environments, where they prevent passivation layer formation. Titanium dioxide-coated zinc anodes show a 50% reduction in self-discharge rates while maintaining high discharge capacity. The challenge with inorganic coatings is their brittleness, which may lead to cracking during repeated cycling.

The choice of corrosion prevention method depends on the electrolyte system. In acidic electrolytes, lead and bismuth inhibitors combined with carbon-based coatings provide the best results. Alkaline systems benefit more from indium additives and polymer or inorganic coatings due to their ability to manage passivation and dendrite growth.

A comparison of corrosion prevention methods reveals tradeoffs between effectiveness, cost, and environmental impact. Lead inhibitors are effective but toxic, indium is efficient but expensive, and bismuth offers a middle ground. Coatings provide physical protection but may add manufacturing complexity. The optimal approach often involves a combination of additives and coatings tailored to the specific battery chemistry and application requirements.

In summary, corrosion prevention in zinc anodes is critical for improving battery performance and longevity. Chemical inhibitors like lead, indium, and bismuth modify surface properties to reduce hydrogen evolution, while coatings provide physical barriers against electrolyte interaction. Each method has advantages and limitations, necessitating careful selection based on electrolyte type and performance goals. Future advancements may focus on developing non-toxic, low-cost inhibitors and multifunctional coatings to further enhance zinc anode stability.