Non-rechargeable zinc-air batteries have found specialized applications in devices where high energy density, compact size, and cost efficiency are critical. These primary batteries operate by oxidizing zinc with oxygen from the air, enabling a lightweight design with high theoretical energy density. Three key use cases—hearing aids, medical sensors, and railway signaling—demonstrate their advantages while also exposing limitations that influence their adoption.

In hearing aids, zinc-air batteries dominate the market due to their ability to deliver consistent power in a small form factor. The high energy density, typically ranging between 1,000 and 1,400 Wh/L, allows these batteries to last significantly longer than alternatives in the same size category. This is crucial for users who rely on hearing aids daily, as frequent battery replacements are inconvenient. The low cost of zinc-air cells compared to primary lithium batteries further enhances their appeal for disposable applications. However, a major limitation is their sensitivity to environmental conditions. Once activated by exposure to air, the electrolyte gradually dries out, leading to a finite shelf life even when unused. Humidity can accelerate this process, making storage conditions critical. In contrast, primary lithium batteries, such as lithium coin cells, offer longer shelf life and better humidity resistance but at a higher cost and with lower energy density for the same size.

Medical sensors, particularly those used in continuous glucose monitoring (CGM) systems, also benefit from zinc-air chemistry. These sensors require stable, long-lasting power sources to operate for extended periods without intervention. The high energy density of zinc-air batteries allows for miniaturization, which is essential for wearable medical devices. Additionally, the flat discharge curve ensures consistent voltage output, improving sensor accuracy. However, the same environmental vulnerabilities apply. Medical applications often demand reliability over months, and zinc-air batteries may degrade prematurely if exposed to high humidity or temperature fluctuations. Primary lithium batteries are sometimes preferred in these cases due to their stability, but their higher cost can be prohibitive for disposable medical devices.

Railway signaling systems, especially in remote or backup applications, utilize zinc-air batteries for their high capacity and low maintenance. These batteries power trackside signals, ensuring operational safety even during power outages. The ability to store large amounts of energy in a compact package makes them suitable for locations where space and weight are constraints. Unlike hearing aids or medical sensors, railway signaling can tolerate some environmental variability, but long-term reliability remains a concern. Shelf life is less critical than in consumer applications, as batteries are typically installed and activated as needed. However, once activated, the same degradation mechanisms apply, limiting their service life. Primary lithium batteries are sometimes used in extreme climates where zinc-air performance may falter, but the cost differential often favors zinc-air for large-scale deployments.

The advantages of zinc-air batteries in these applications are clear. Their energy density outperforms many other primary chemistries, enabling smaller and lighter devices. The use of atmospheric oxygen as a reactant reduces internal material requirements, lowering production costs. This makes them economically attractive for high-volume, disposable applications. Additionally, they are environmentally benign compared to some alternatives, as they contain no toxic heavy metals like cadmium or mercury.

However, limitations must be carefully managed. Shelf life is a persistent challenge; once the battery’s seal is broken and air enters, the electrochemical process begins, even if the battery is not in use. This makes inventory management critical, particularly for medical and consumer applications where batteries must be fresh to meet performance expectations. Humidity sensitivity further complicates storage and handling, requiring protective packaging or climate-controlled environments. In contrast, primary lithium batteries do not rely on air exposure and can remain stable for years, but their higher cost and lower energy density in small formats often make them less practical for these specific use cases.

Performance trade-offs also exist. Zinc-air batteries provide a flat voltage discharge curve, which is beneficial for consistent device operation, but their power density is relatively low. This makes them unsuitable for high-drain applications. Primary lithium batteries, with their higher power density, can support more demanding loads but may not last as long in low-power, continuous-use scenarios.

In summary, non-rechargeable zinc-air batteries excel in hearing aids, medical sensors, and railway signaling due to their unmatched energy density and cost efficiency. Their limitations—shelf life and humidity sensitivity—require careful consideration in device design and deployment. While primary lithium batteries offer superior stability in harsh conditions, their higher cost and lower energy density in small form factors often make zinc-air the preferred choice for these specialized applications. The selection between the two depends on specific operational requirements, environmental conditions, and economic constraints.