Paper-thin biodegradable zinc batteries developed at Nanyang Technological University Singapore may offer an environmentally sustainable option for powering flexible and wearable electronic systems.

The zinc batteries are composed of electrodes screen-printed onto both sides of a piece of cellulose paper reinforced with hydrogel. The paper functions as the separator between the anode, printed with a zinc- and carbon black-based conductive ink, and the cathode printed with manganese and nickel inks. The device is immersed in an electrolyte solution, after which a thin layer of gold is applied to both electrodes to increase conductivity.

Schematic of battery fabrication. Source: Nanyang Technological University SingaporeSchematic of battery fabrication. Source: Nanyang Technological University Singapore

The 0.4 mm thick battery as a more sustainable alternative to available battery options is confirmed by its microbial degradation within a month after being placed in soil. According to the researchers, the nickel and manganese used in the cathodes will remain in their oxide or hydroxide forms, which approximate the form of natural minerals. The zinc used in the anode is naturally oxidized to form a non-toxic hydroxide.

In a proof-of-concept experiment described in Advanced Science, the printed paper battery was demonstrated to power a small electric fan for at least 45 minutes. Bending or twisting the battery did not interrupt the power supply, confirming its utility for powering flexible and wearable electronics.

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