Discarded electronics are accumulating rapidly, prompting researchers to explore creative ways to reduce the resulting litter, known as e-waste. Now, a team has designed a disposable, water-activated battery made from paper and other durable materials.
The wires, screens, and batteries that make up our devices, not to mention the plastic, metal, and other materials that envelop them, fill landfills with dangerous debris. Some electronic waste is relatively large: old flip phones, air conditioners and radios, to name a few common items. Other e-waste is more insidious, such as single-use electronic medical diagnostic kits, environmental sensors, and smart tags containing disposable batteries and other equipment.
“It’s those little batteries that are the big problems,” says Dele Ogunseitan, a professor of public health at the University of California at Irvine, a green technology researcher and adviser to big tech companies, who wasn’t involved in the development. paper battery. . “Nobody really cares where they end up.”
Researchers from the Cellulose & Wood Materials Laboratory at Empa (Federal Laboratory for Materials Science and Technology) are trying to solve this neglected problem. This week they published an article in Scientific reports describing a new water-activated paper battery they developed from environmentally friendly materials. Such a device could potentially present a sustainable alternative to the more harmful batteries that are common in low-drain devices.
The new paper battery has the same key components as the standard batteries but packages them differently. Like a typical chemical battery, it has a positively charged side called the cathode, a negatively charged side called the anode, and a conductive material called the electrolyte in between. The components of a traditional battery are encased in plastic and metal; in the new battery, the anode and the cathode are inks printed on the front and back of a sheet of paper. This paper is infused with salt, which dissolves when the paper is moistened with water. The resulting salt water solution acts as an electrolyte.
Sustainable materials were a prerequisite for the researchers, who considered only non-toxic and abundant ingredients to create their device. “We were pretty confident that we would have something that would work in the end, but developing these materials and ink systems is far from trivial,” says Gustav Nyström, head of the Cellulose & Wood Materials lab and lead author of the study. After trying hundreds of formulations for the different components, the scientists settled on graphite ink to make the cathode, zinc ink for the anode, and salt-infused paper to create the electrolyte. When the paper is dry, the battery is stable. However, add just a few drops of water and the rooted salt dissolves, allowing electrons to flow. Once the paper is moistened, it takes about 20 seconds for the battery to activate. At this point, it produces a steady 1.2 volt electricity until the paper dries. (For comparison, an AA battery provides 1.5 volts.) When the researchers rewet the paper, the battery produced 0.5 volts for more than an hour.
Although the researchers demonstrated that their battery could power an alarm clock, disposable paper batteries are unlikely to replace standard AA batteries on store shelves. Instead, Nyström envisions a future where these batteries are integrated into diagnostic tests and environmental sensors, ideally alongside other durable components such as displays and packaging. This future may not be so distant.
It’s hard to predict a timeline for manufacturing such items on a large scale, but Nyström says he’s in touch with potential industry partners and believes these batteries could make their way into products within two. at five years old. “I think the performance you see on this device is already good enough for a lot of these apps,” he says. This is mainly to increase production and integrate the batteries into systems such as diagnostic tests and environmental sensors.
Importantly, Nyström says his team created the battery without compromising sustainability criteria. “It’s work that really starts with the development of sustainable materials,” he explains. From there, he says, “I think we were able to create something very useful.”