A method to fabricate batteries from biodegradable materials that can operate in the environment, such as on or under soil, and are scalable in size.

Recently there have been significant developments in biodegradable sensors, which can perform environmental measurements (e.g., on or below the surface of soil) for a specific time and then degrade harmlessly into the environment. Such sensors often require power sources for standalone implementation. These power sources may be used to drive electronic components, take electrochemical measurements, and enable wireless communication with other external devices. To fully realize fully biodegradable sensor systems for these applications, their power sources must also be biodegradable.

Researchers at the University of Pennsylvania developed a method to fabricate metal-air batteries from biodegradable materials that operate in air or on/under soil. The battery can be scaled down to the approximate size of a corn-kernel for potential deployment with planters. The use of biodegradable materials allows for terrestrial implementation with lower sustainability risks compared to commercial batteries. A power source can be more stable on the surface and below it if it is enclosed in wax, which shields it from the surrounding conditions.

The disclosure demonstrated the fabrication of zinc-air batteries constructed from thin-film-based anodes, catalyst-containing cathodes, a biodegradable gel electrolyte, and a wax-based enclosure. Material selection is leveraged to allow for the preferential permeation of oxygen relative to the passage of water or carbon dioxide to power the battery. The technology can deliver a consistent output voltage of up to 1.2 volts for months in the air and underground, thanks to accurate power cell design. Current work involves further optimization to transition the batteries into integrated sensor platforms for wireless applications.

• A fabrication route to construct metal-air electrochemical cells (e.g., Zn-air) from biodegradable materials with selective passage of relevant chemical species for operation (water, oxygen, carbon dioxide).
• Provides a route to assemble the metal-air electrochemical cell with a biodegradable enclosure (e.g., wax) for ambient protection, allowing for stability in subsurface environments (e.g., soil) as well as air environments.
• Displays battery performance in surface and sub-surface environments such as soil over months-long periods with output voltages up to 1.2 volts, highlighting potential for usage in wireless sensors.