Biodegradable battery brings sustainability to the Internet of Things

“By combining nanocellulose with various forms of carbon particles we were able to create a highly functional device containing non-toxic and biodegradable materials”Gustav Nyström

Researchers from the Swiss Federal Laboratories for Materials Science and Technology (Empa) have developed a biodegradable battery made from a modified and commercially available 3D printer. The printing process, based on a combination of gelatinous inks produced from cellulose nanofibers and nanocrystallites, as well as carbon black, graphite and activated carbon, ensures the device is biodegradable, and can be left to decompose.

The battery has potential uses in biodegradable inks for sustainable electronics, energy storage devices for low power applications in the Internet of Things, integrated health monitoring, and environmental or agricultural sensing. Expanded use of the Internet of Things for wearables, packaging and powering sensors in environmental monitoring has helped a new class of electronics to emerge, with the number of connected devices expected to rise rapidly over the next few years. However, standard lithium-ion and alkaline batteries are still powering most smart devices that require dedicated collection and recycling of their non-renewable and toxic materials.

This has all helped promote the field of sustainable electronics. In this study, reported in the journal Advanced Materials [Aeby et al. Adv. Mater. (2021) DOI: 10.1002/adma.202101328], a combination of digital material assembly, stable performance operation, and non-toxicity could offer a path to innovative and sustainable electronics.

Led by Gustav Nyström, the team focused on identifying new ways to create high performance materials from renewable resources. Here, they examined the multifunctional use of nanocellulose as a structural material, dispersing agent for inks and as active component in the electrodes of a fully 3D printed supercapacitor. As Nyström told Materials Today, “By combining nanocellulose with various forms of carbon particles we were able to create a highly functional device containing non-toxic and biodegradable materials”.

Glycerin, water and two types of alcohol were used to liquefy the gelatinous inks, with some table salt to ensure ionic conductivity. These ingredients were processed in four layers – a flexible substrate, a conductive layer, the electrode and then the electrolyte – which were 3D printed in succession in a single procedure. This combination was then folded up with the electrolyte in the middle.

The resulting mini-capacitor can store electricity for hours, and there would be no need to collect these batteries as they could be left in nature to degrade. The battery can also endure thousands of charge and discharge cycles and years of storage, even in freezing temperatures, and is resistant to pressure and shock. The team now hope to further develop their fully green printed energy storage approach, as well as to enhance its performance and investigate ways to interface with biodegradable sensing concepts.