Just Add Water—Paper-based Batteries Activated by a Water Switch

August 01, 2022 by Jake Hertz

To reduce e-waste, researchers are experimenting with paper-based batteries. This latest one comes from Empa, which is activated by water.

There has undoubtedly been an enormous amount of research and development in the battery industry. For the most part, the majority of this research focuses on increasing performance or decreasing cost, where considerations like capacity, weight, and power output are amongst the most sought-after developments.

However, equally as important is the sustainability aspect of modern batteries. Today, lithium-ion (Li-ion) batteries contribute to a significant amount of unwanted electronic waste (e-waste) across the world. To counteract this, researchers from Empa have developed a new, safely disposable battery made out of paper and activated by water.


Empa's paper-based battery.

Empa's paper-based battery. Image used courtesy of Empa


In this article, we’ll look at the rising e-waste concerns surrounding Li-ion batteries and how the new research from Empa hopes to address them.


Rising Electronic Waste Concerns

One of the biggest concerns facing the environment today is the growing amount of e-waste produced.

Generally, e-waste is defined as any and all electronic devices that are disposed of for any reason. E-waste is quickly becoming one of the largest contributors to landfills in the world, as recent reports estimate that in 2021, 57.4 million metric tonnes of unrecycled e-waste will find its way into landfills. 


An overview of global e-waste generation.

An overview of global e-waste generation. Image used courtesy of The RoundUp


Compared to other forms of landfill, e-waste can be particularly troubling for several reasons.

One reason is that many electronic devices are discarded because they are antiquated, not because they are no longer functional. Consider today’s consumer culture, where new smartphone models are introduced yearly. Many are prone to dispose of an “old” phone, even if it works, in place of the latest phone model.

Beyond this, unlike other waste, e-waste often contains battery-powered devices, where the batteries are likely to contain toxic and unsafe chemicals. When placed in a landfill, these chemicals can leak from the batteries and be absorbed into the earth, where the toxins can work their way into local water sources. Further complicating the matter, as of 2019, only 5% of lithium-ion batteries were recycled worldwide.


Unpacking Empa's Water Activated Paper-based Battery

Recently, researchers from Empa made headlines when they announced a new safely disposable, paper-based battery.

As described in its recently published paper, the battery structure consists of three different inks judiciously printed onto a 1 cm2 piece of paper. The battery cathode is created using graphite-infused ink, which is printed onto one side of the paper, while the anode is printed using ink infused with zinc powder on the opposite side. A third ink containing both graphite and carbon is then printed on the sides of the paper on top of the other inks to act as the current collector establishing a connection between anode and cathode. Salt is then dispersed across the paper, and one end of the paper is coated in wax.


A more detailed look at the battery from Empa.

A more detailed look at the battery from Empa. Image used courtesy of Poulin et al [click image to enlarge]


The battery works when a trace amount of water is added to the paper. The water absorbs the dispersed salt, and the new aqueous solution acts as an ionically conductive electrolyte, thus acting like a switch. This electrolyte solution then naturally disperses throughout the paper and induces oxidation at the anode, allowing the paper to act as a fully functional battery.

The result of the research was the successful demonstration of the battery’s ability to run low-power electronics. The researchers showed their battery offered an open-circuit voltage of 1.2 V and achieved a peak power density of 150 μW/cm2 at 0.5 mA. 

While not a powerful battery, designers could feasibly use it in low-power applications like Internet of Things (IoT) devices. Even more important is the potential environmental impact of a technology like this—where disposable battery technologies like these could significantly limit future e-waste.