Researchers from NTU have recently developed a zinc-based battery using screen printing techniques that allow for custom shapes and biodegradability. What challenges do batteries present, what did the researchers develop, and how could they be used in engineering projects?

What challenges do batteries face?

Batteries are often the most significant limiting factor when designing portable devices. They dictate how long a device can operate before needing to either be recharged or have the battery replaced. Battery life can be extended with a bigger battery, increasing the device’s weight. Reducing the power consumption of a circuit will also increase battery life, but this will undoubtedly result in fewer capabilities for the circuit. Different battery technologies (such as lithium) can be considered, but this can increase the product’s final price, making it harder to sell.

All of these problems relate to the usage of a device, but recent changes in legislation and activism for environmental protections now sees engineers having to also consider the end-of-life impact of their devices. How will their device be recycled? What dangers do their devices pose to the environment if improperly disposed of?

Most of these concerns are already solved using RoHS and REACH compliant components for modern electronics. Such legalisation has seen most harmful compounds eliminated from modern electronics (such as lead and cadmium), and the hazardous compounds that remain are either essential or in very small quantities.

But batteries are once again one of the largest areas of concern for engineers as they can be toxic and dangerous. For example, lithium-ion batteries are not only a fire risk (which can ignite waste around it if dumped in a landfill) but can also leak toxic compounds into the ground that can find their way into the environment. As such, finding battery technologies that both fit the application as needed and provide a good end-of-life solution is increasingly difficult.

Researchers develop biodegradable zinc paper battery

Researchers from NTU (Nanyang Technological University) have recently developed a new battery that uses an electrodes screen printed directly onto two sides of a piece of cellulose paper. To suspend the electrolyte between the printed electrodes, a hydrogel was used to reinforce the battery structurally.

The printed battery is not only extremely thin, but it also shows extreme flexibility that allows it to be bent with no drop in performance. The battery was also demonstrated to operate even when being twisted, demonstrating the batteries potential in flexible electronics. Furthermore, the battery can be cut to any 2D shape and still perform without reducing efficiency. This allows for creating batteries of unusual shapes that can be fitted into a product’s enclosure.

The battery’s ability was demonstrated by using a 4x4cm piece to power a small electric fan for 45 minutes. The resilience of the battery was also demonstrated by connecting it to an LED and demonstrating that the LED remained lit despite the researchers cutting pieces of the battery off.

But what makes the new battery even more promising is that the researchers demonstrated that the battery is 100% biodegradable. After one month of being in the soil, the battery completely breaks down, and the use of zinc and cellulose reduces the environmental impact of the battery.

What applications could this new battery be used in?

It is important to note that many research papers produce concept electronic devices or power sources that rarely have any practicality. For example, some researchers continue to explore wearable TEGs, but such power sources would never be practical due to their very low efficiency and large temperature gradient required.

The researchers at NTU have demonstrated a battery that shows real promise as it was demonstrated to power a small fan for 45min. Even if the DC motor used was a low current device, powering a motor requires a sizeable amount of energy that could easily be used by low-energy semiconductor devices. Furthermore, powering a fan for 45 minutes straight is an impressive feat when the battery is just 4x4cm in size that is 100% biodegradable and can be cut to size.

If this battery technology can be made commercial, it would have great use in portable devices that want to create custom shaped batteries. For example, the enclosure of a device with curves and protrusions could have a battery perfectly tailored to it, and this would provide the most efficient use of space. Assuming that the battery technology is thin, multiple batteries could be stacked vertically in layers inside an enclosure to help increase the device’s battery life. Each layer can be custom made to fit perfectly inside the device.

Such batteries could also be used in disposable electronics. Printed NFC tags on product packaging could be fitted with zinc batteries that provide users with data such as total journey travelled, CO2 emitted as a result from production, logged temperature at all stages of distribution, and even warnings if the product has expired.

In conclusion, this battery technology shows great promise. If it can be proven to work with modern devices, then printed disposable batteries could be the key to a more sustainable future.